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Chemical composition of coal surface as derived from micro-FTIR and its effects on contact angle Liu, Jie 2016

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CHEMICAL COMPOSITION OF COAL SURFACE AS DERIVED FROM MICRO FTIR AND ITS EFFECTS ON CONTACT ANGLE by Jie Liu  B.S., Central South University, 2013  A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF  MASTER OF APPLIED SCIENCE in The Faculty of Graduate and Postdoctoral Studies (Mining Engineering)  THE UNIVERSITY OF BRITISH COLUMBIA (Vancouver) July 2016  © Jie Liu, 2016   ii   Abstract  In this study, in situ image analysis, contact angle measurements, micro-FTIR spectroscopy and SEM are used to obtain information on the surface composition of coal. The heterogeneous coal surface is investigated with regard to the distribution of the chemical functional groups and its effect on hydrophobicity as derived from contact angle measurements. Contact angles obtained from sessile drop and captive bubble techniques are correlated with the semi-quantitative ratios from micro-FTIR spectroscopy. As part of the new methodology, image analysis and SEM are also applied in order to characterize and analyze for the petrographic composition of areas that are subjected to these measurements. An opposite trend between high rank coal and low rank coal is found in relation to the micro-FTIR semi-quantitative ratios versus contact angle. For lower rank coal, the increase in Aromaticity 1 and 2 led to an increase in the contact angle, while the increased quantity of aliphatic groups decreased the contact angle values. For high rank coal, the rising aliphatic groups increased the contact angle values and the increase in Aromaticity 1 and 2 led to smaller contact angle values. The newly introduced CHal/C=O was used to assess the abundance of aliphatic groups and oxygenated groups. The increased content of oxygenated groups in the high rank coal samples led to a decrease in the contact angle, which is consistent with the findings of previous studies. For low rank coal samples, although the correlation was less distinct, an opposite trend was observed. iii   Preface  Dr. Maria Holuszko suggested the idea of characterizing the hydrophobicity and investigating the heterogeneity of coal surface using micro-FTIR mapping, which can be used to explore the hydrophobicity, petrographic composition and chemical composition of coal surface. The correlation between the hydrophobicity and chemical composition of coal surface was observed by combining contact angle measurements and micro-FTIR analysis with micro-FTIR mapping. The design of this research project, analysis of the experimental data and the preparation of the manuscript were conducted by the author under the supervision of Dr. Maria Holuszko. All the experimental work including sample preparation, contact angle measurements, micro-FTIR, petrographic analysis by image analysis and SEM were carried out by the author. Measurements of vitrinite reflectance were performed by the lab of Dr. Maria Mastalerz at the Indiana Geological Survey of Indiana University, USA.    iv   Table of Contents  Abstract .......................................................................................................................................... ii Preface ........................................................................................................................................... iii Table of Contents ......................................................................................................................... iv List of Tables ............................................................................................................................... vii List of Figures ............................................................................................................................. viii List of Abbreviations .................................................................................................................. xii Acknowledgements .................................................................................................................... xiii Chapter 1: Introduction ............................................................................................................... 1 1.1 Objectives ................................................................................................................... 2 1.2 Thesis organization ..................................................................................................... 3 Chapter 2: Literature Review ...................................................................................................... 4 2.1 Coal rank ..................................................................................................................... 4 2.2 Coal chemistry ............................................................................................................ 6 2.3 Heterogeneity of coal surface ..................................................................................... 9 2.4 Wettability of coal surface ........................................................................................ 11 2.5 Contact angle and micro-FTIR techniques ............................................................... 15 2.5.1 Contact angle measurement .................................................................................. 15 2.5.2 Micro-FTIR technique .......................................................................................... 18 Chapter 3: Experimental Procedures ....................................................................................... 30 3.1 Introduction ............................................................................................................... 30 3.2 Sample preparation ................................................................................................... 32 3.3 Petrographic analysis ................................................................................................ 34 3.4 Contact angle measurement ...................................................................................... 37 3.4.1 Drop volume ......................................................................................................... 39 3.4.2 Other parameters ................................................................................................... 40 v   3.5 Micro-FTIR spectra .................................................................................................. 41 3.6 SEM analysis ............................................................................................................ 43 Chapter 4: Results....................................................................................................................... 44 4.1 Petrographic analysis ................................................................................................ 44 4.1.1 Vitrinite reflectance .............................................................................................. 44 4.1.2 Petrographic characterization................................................................................ 45 4.2 Contact angle measurements..................................................................................... 49 4.2.1 Advancing and receding contact angles ................................................................ 50 4.2.2 Sessile drop and captive bubble techniques .......................................................... 53 4.3 Micro-FTIR measurements ....................................................................................... 59 4.3.1 Micro-FTIR spectra .............................................................................................. 59 4.3.2 Semi-quantitative ratios ........................................................................................ 62 4.3.3 Micro-FTIR mapping ............................................................................................ 67 Chapter 5: Discussions ............................................................................................................... 72 5.1 Aromaticity ............................................................................................................... 73 5.2 Degree of condensation............................................................................................. 77 5.3 CH2/CH3 .................................................................................................................... 78 5.4 Aliphatic CHx/Oxygenated groups ........................................................................... 79 Chapter 6: Conclusion ................................................................................................................ 83 Chapter 7: Recommendations ................................................................................................... 86 References .....................................................................................................................................88 Appendices ....................................................................................................................................94 Appendix A Micro-FTIR spectroscopy operation ............................................................ 94 Appendix B SEM operation .............................................................................................. 95 Appendix C SEM results .................................................................................................. 96 Appendix D Petrographic analysis results ...................................................................... 100 vi   Appendix E Contact angle measurements results ........................................................... 109 Appendix F Contact angle measurements results ........................................................... 110 Appendix G Micro-FTIR measurements results ............................................................. 114     vii   List of Tables  Table 2.1 Vitrinite Reflectance values for different coal rank...................................................6 Table 2.2 Comparison between the most frequently used Fourier Transform Infrared spectroscopy techniques related to sample preparation, resolution, sensitivity and other aspects. ..........................................................................................................................................19 Table 2.3 Absorption bands observed in the FTIR spectra of coals based on previous works.........................................................................................................................................................22 Table 2.4 Semi-quantitative ratios derived from FTIR spectra based on previous research. ........................................................................................................................................24 Table 2.5 The characteristics of each individual maceral and corresponding functional group abundance. ....................................................................................................................................26 Table 3.1 Band assignments for the micro-FTIR spectra of coal samples. ............................42 Table 4.1 Vitrinite reflectance and description of analyzed coal marked area. .....................44 Table 4.2 Petrographic analysis results of predetermined spots on coal surface (the specific image analysis information is attached in Appendix C). ..........................................................48 Table 4.3 The reproducibility of contact angle measurements using FTA1000 on glass. .....54 Table 4.4 Contact angles and standard deviations using sessile drop and captive bubble techniques. ....................................................................................................................................57 Table 4.5 Semi-quantitative ratios on the predetermined areas for all polished sample blocks (the average areas of band intensities using micro-FTIR spectroscopy on predetermined areas is attached in Appendix F). ...............................................................................................66  viii   List of Figures  Figure 2.1 Variation in coal structure and carbon content with coal rank (Barnes et al., 1984)...........................................................................................................................................................4 Figure 2.2 Carbon distribution as a function of coal rank (Whitehurst et al., 1980). .............5 Figure 2.3 Schematic representative of coal surface (Laskowski, 2001a). ................................9 Figure 2.4 FTA1000 drop shape analyzer (left) and an example image captured for surface tension analysis (right) (Liu et al., 2015). ...................................................................................18 Figure 3.1 Methodology for experimental approach. ...............................................................31 Figure 3.2 Schematic of contact angle measurement area and micro-FTIR points. .............32 Figure 3.3 Polished sample blocks for contact angle measurements and micro-FTIR (a) low rank coals with average vitrinite reflectance of about 0.6% (b) high rank coal with average virinite reflectance of about 1.6%. .............................................................................................34 Figure 3.4 Image analysis window of the microscope software Stream, including maceral distribution and settings for maceral determination. ...............................................................35 Figure 3.5 Example of image analysis results using Phase Analysis of Stream (a) original coal surface under microscope (b) first ROI area of mostly vitrinite area (c) second ROI area of mostly inertinite. ..........................................................................................................................36 Figure 3.6 FTA 1000B Class drop shape analyzer instrument (a) and examples of sessile drop (b) and captive bubble methods of contact angle measurements. ...........................................37 Figure 3.7 The effect of evaporation prevention on contact angle using the sessile drop method. ..........................................................................................................................................38 Figure 3.8 Contact angle versus time using different drop volumes: from 2 to 6 𝛍𝐥, on sample (a) E2 and (b) E3. .........................................................................................................................40 Figure 3.9 Micro-FTIR spectra instruments (a) in Indiana University, Bloomington, IN and an example of OMNIC software possessing the micro-FTIR mapping data (b). ..................41 Figure 3.10 The Hitachi S3000N Scanning Electron Microscope (Materials Engineering, UBC) ..............................................................................................................................................43 ix   Figure 4.1 Photomicrographs of macerals on predetermined spots in high rank coal. (a) Liptinite finely dispersed with vitrinite, (b) fusinite and (d) semifusinite are common in the studied high rank coal. ................................................................................................................46 Figure 4.2 Photomicrographs of macerals on predetermined spots in low rank coal (a) Semifusinite, cutinite and vitrinite are associated together in sample L6. (b) Semifusinite is surrounded by vitrinite in sample L7. (c) Cutinite in sample L2. (d) Pure vitrinite associated with some pyrite in sample L3. ...................................................................................................47 Figure 4.3 Illustration of the four methods used for contact angle measurements (a) sessile-drop technique (static) (b) sessile-drop technique (dynamic) (c) captive bubble technique (static) (e) captive bubble technique (dynamic). .......................................................................49 Figure 4.4 The advancing and receding contact angles obtained from sessile drop measurements and the corresponding four points on the plot on which contact angles were measured (Point A, B, C and D). ................................................................................................51 Figure 4.5 The advancing and receding contact angles obtained from captive bubble measurement and the corresponding four points on the plot for which contact angles were measured (Point A, B, C and D). ................................................................................................51 Figure 4.6 An example of individual contact angle versus time on predetermined areas (L1, L2, L3 and L4) using the sessile drop technique. ......................................................................55 Figure 4.7 An example of individual contact angle versus time on predetermined areas (L1, L2, L3 and L4) using the captive bubble technique. .................................................................56 Figure 4.8 Average contact angles of different sample blocks using sessile drop and captive bubble techniques.........................................................................................................................58 Figure 4.9 Average micro-FTIR spectra on predetermined areas on the different samples. Functional groups: (A) aromatic CHx; (B) aliphatic CHx (C) oxygenated groups (D) C=C aromatic ring (E) aliphatic CHx out-of-plane deformation (F) aromatic CHx out-of-plane deformation. .................................................................................................................................60 Figure 4.10 Micro-FTIR spectra of vitrinite from low rank coal (H2, H3) and high rank coal (L1, L8)..........................................................................................................................................62 Figure 4.11 Graphs of semi-quantitative ratios on the predetermined areas for a) high rank coal and b) low rank coal.............................................................................................................63 x   Figure 4.12 Value of aliphatic CHx versus oxygenated groups for both low rank and high rank coals. .....................................................................................................................................65 Figure 4.13 The results of micro-FTIR mapping on Danville 2. (a) Micro-FTIR microscopic image observed through 10× objective; (b) chemical mapping of aliphatic CHx (3000-2800 cm-1) in the field of study; (c) corresponding 3D-image of absorbance; (d) screen shot of the results of micro-FTIR mapping on Danville 2 using the software Stream. ............................68 Figure 4.14 The corresponding chemical map superimposed on the microscopic image in the field of study on Danville 2 of (a) aliphatic CHx stretching region (b) oxygenated groups (c) aromatic CHx out-of-plane deformation (d) ratio of aliphatic CHx stretching region/aromatic CHx out-of-plane deformation. ...................................................................................................69 Figure 4.15 Micro-FTIR mapping of heterogeneous coal surface on Danville 1. (a) Micro-FTIR microscopic image; (b) the corresponding chemical map of aliphatic CHx stretching region in the field of study. ..........................................................................................................70 Figure 5.1 Illustration of the major structure of this thesis and the corresponding approaches and techniques used. ....................................................................................................................72 Figure 5.2 Relationship between the ratio of aromatic groups to the aliphatic group and respective contact angles using sessile drop (a)aromaticity 1: aromatic CHx stretching at 3082-3002 cm-1 versus aliphatic CHx stretching; (b)aromaticity 2: aromatic CHx out of plane deformation at 904-700 cm-1 versus aliphatic CHx stretching and captive bubble (c)aromaticity 1; (d)aromaticity 2. .............................................................................................74 Figure 5.3 Scanning electron microscopy images of fusinite macerals on (a) H3 and semifusinite macerals on (b) H4..................................................................................................76 Figure 5.4 Photomicrographs of vitrinite maceral on L3 and corresponding scanning electron microscopy images of vitrinite maceral on L3 ............................................................76 Figure 5.5 Micro- FTIR mapping of pure vitrinite. (a) Micro-FTIR microscopic image and corresponding chemical mapping of ratio of CHal stretching groups (2803-2996 cm-1) versus CHar stretching groups (700-904 cm-1); (b)micro-FTIR microscopic image and corresponding chemical mapping of CHar stretching groups (700-904 cm-1). ........................77 xi   Figure 5.6 Relation between degree of condensation and respective contact angles using sessile drop (a) DOC 1: aromatic CHx stretching versus C=C stretching at 1677-1521 cm-1 (b) DOC 2: aromatic CHx out of plane deformation versus C=C stretching. ..............................78 Figure 5.7 Relationship between the ratio of CH2 to CH3 and respective contact angle using (a) sessile drop technique and (b) captive bubble technique....................................................79 Figure 5.8 Relationship between the ratio of CHal stretching to C=O groups and respective contact angle using (a) sessile drop technique and (b) captive bubble technique. .................80 Figure 5.9 Scanning electron microscopy images taken on L8 with observed minerals (a) and corresponding energy-dispersive X- ray spectroscopy on spot b of L8 ..................................81 xii    List of Abbreviations  Micro-FTIR                   Micro-Fourier Transform Infrared Spectroscopy SEM                              Scanning Electron Microscope  IGC                               Inverse Gas Chromatography CGA                             Coal Grain Analysis xiii   Acknowledgements  My primary thanks must go to my supervisor, Dr. Maria E. Holuszko, for supporting my stay in the Mining Engineering Department at the University of British Columbia for the two years of my Master of Applied Science degree. Her expert opinions, valuable comments, the countless hours spent on my research proposal and endless discussions and review, are all deeply appreciated.   I am particularly thankful to Dr. Maria Mastalerz from the Indiana Geological Survey of Indiana University, USA, for providing coal samples, instruments for micro-FTIR measurements and specific training on operating the instrument. Dr. Maria Mastalerz also provided me with insightful suggestions and comments about my work, and displayed tireless enthusiasm during my stay at Indiana University.   I would like to express my sincere gratitude to the faculty, staff and my fellow students in the Mining Engineering Department at the University of British Columbia. In particular, sincere thanks are due to Sally Finora for providing coherent answers to a great variety of technical matters.   Finally, I would like to offer my parents much gratitude for their constant encouragement and support through the course of my studies  1   Chapter 1: Introduction  Coal is not a uniform substance but rather a mixture of combustible metamorphosed plant remains that vary in both physical and chemical composition (Yancey et al., 1968). The progressive enrichment of the coal substance in organic bound carbon is referred to as coalification (Laskowski, 2001a). The diversity of the original plant material and the degree of metamorphism (coalification) that has affected these materials, are the two major reasons for the complex heterogeneity of coal. The widely varying composition greatly affects the characteristics of coal, such as its hydrophobicity, which is very important during processing by flotation.   The heterogeneity of coal surface is the result of variations in petrographic composition, porosity,  as well as size and the distribution of mineralogical inclusions, all of which have great influence on the hydrophobicity of coal (Laskowski, 2001b, Laskowski and Walters, 1992). Contact angle has been used for over a century to characterize surface hydrophobicity. High contact angle values indicate a hydrophobic surface, while lower contact angle values indicate a less hydrophobic surface. Macerals have been shown to exhibit different hydrophobicity characteristics, and hence their response to flotation can vary depending on the surface properties that result from their chemical composition as well as their associations with each other and minerals. Ofori et al. (2010) have developed a methodology to assess the hydrophobicity of petrographically different coal surfaces and their methodology was based on the assumption that individual macerals are chemically uniform.   2   This thesis investigates the chemical composition of the areas that are heterogeneous as well as represented by single macerals. Here, chemical composition is derived from the micro-FTIR analysis of the spots that were selected for contact angle measurements, and this correlation is referred to as ‘in situ’. The correlation between contact angles and semi-quantitative ratios from micro-FTIR analysis were observed for low and high rank coal samples. The importance of this research is that:  This is the first time that the chemical surface composition of coal has been assessed exactly on the area where contact angles were measured, hence direct correlations between the chemistry, petrographic composition and physical surface heterogeneity of coal and hydrophobicity were developed.   Micro-FTIR methodology was adopted to use on a scale that could be employed for developing such correlations.  New ratios were developed from micro-FTIR analysis, specifically with respect to correlation with hydrophobicity.  1.1 Objectives The main objective of this study is to investigate the chemical composition of coal surface in relation to the hydrophobicity of coal.  Specifically, the following objectives are addressed:   To investigate the most feasible method for contact angle measurements; sessile drop and captive bubble techniques were evaluated while choosing between static and dynamic measurements and the most suitable parameters for measuring contact angle. 3    To assess coal hydrophobicity by contact angle.  To investigate the distribution of functional groups on pure macerals and other preselected areas with different macerals in composition via micro-FTIR spectroscopy and mapping.   To adopt micro-FTIR for the purpose of measuring the large areas of coal surface that were suitable for contact angle measurements.  To establish the correlation between the functional group abundance of coal surface and hydrophobicity, using image analysis, petrographic composition and SEM to study the unusual trends.   1.2 Thesis organization The thesis starts with an introduction to the research background and objectives. Section 2 provides background with respect to petrographic and chemical compositions, as well as coal heterogeneity and the hydrophobicity of coal surface. It reviews the theories related to contact angle measurement for characterizing hydrophobicity and obtaining the chemical composition of coal surface. Section 3 describes the methodologies for the preparation of polished sample blocks, contact angle measurements, micro-FTIR analysis, image analysis and SEM used in this study. In section 4, the results are presented from two aspects, contact angle measurements and micro-FTIR measurements followed by the petrographic analysis. In section 5, discussions regarding the outcomes of contact angle measurements, micro-FTIR and the image analysis are included. The effect of chemical and petrographic composition is also discussed in greater detail. The relationships between hydrophobicity and chemical composition are developed through contact angles and semi-quantitative ratios extracted from FTIR spectra and mapping. Finally, section 6 provides the conclusions and recommendations with respect to the work completed in this study.  4   Chapter 2: Literature Review  2.1 Coal rank The term ‘coal rank’ refers to the degree of chemical and physical changes that occur in the organic part of coal that resulted from coalification (Stach and Murchison, 1982). Figure 2.1 shows that the coalification processes may have started with peat formation, followed by a transition to lignite when the peat was buried under sedimentary conditions. The transformation of lignite to bituminous coal and finally to anthracite occurred under the influence of high temperatures and high pressure (Brown, 1962, Stach and Murchison, 1982). Increasing degree of coalification in coals is accompanied by an increase in  elemental carbon content (Barnes et al., 1984).   Figure 2.1 Variation in coal structure and carbon content with coal rank (Barnes et al., 1984).  As seen in Figures 2.1 and 2.2, changes within the structure of coal can be seen as moving from larger molecules assembled together through cross-links to form macromolecules in lower rank 5   coals (lignite, subbituminous) to more condensed aromatic structures with fewer cross-links in the higher rank coals. During its transformation from lignite to bituminous, the structure of coal loses a significant portion of oxygen groups  and the content of aromatic hydrocarbon increases simultaneously (Blom et al., 1957). This is often used to explain the increase of hydrophobicity as coal rank increases. At the onset of the semi-anthracite rank, a sudden molecular orientation is developed and small aromatic stacks aggregate into clusters (Blom et al., 1957). The aromaticity for this class of coal sharply increases while the aliphatic hydrocarbon decreases after reaching a maximum concentration of around 85% C. The graphite-like structure renders the aromatic carbons less hydrophobic than paraffinic hydrocarbons (Pawlik, 2008). Therefore, hydrophobicity decreases as anthracite rank is reached.  Figure 2.2 Carbon distribution as a function of coal rank (Whitehurst et al., 1980).  According to most of the classification systems, rank parameters such as Volatile Matter (VM), Fixed Carbon (FC), vitrinite reflectance, and Calorific Value (heating value) are used to assess the rank of coal (Laskowski, 2001a). Lower rank coals are classified using Caloric Value rather than 6   FC and VM parameters due to its ultimate use in power generation (Baughman, 1978). Higher rank coals past High Volatile B Bituminous rank correlate well with VM content according to ASTM Standards (2005). Hoffmann and Jenkner (1932) were the first to observe that the reflectance of vitrinite increased consistently with increasing rank, regardless of the petrographic composition of coal. In this investigation, vitrinite reflectance, R0, was used to classify coal samples. Table 2.1 presents the R0 values for different coal ranks.  Table 2.1 Vitrinite Reflectance values for different coal rank.  Coal Rank Vitrinite Reflectance Anthracite >2.5% Semi-anthracite 2.0-2.5% Low-volatile bituminous 1.5-2.0% Medium-volatile bituminous 1.5-1.1% High-volatile bituminous A 1.1-0.75% High-volatile bituminous B 0.75-0.65% High-volatile bituminous C 0.65-0.50% Sub-bituminous 0.5-0.4% Lignite <0.4%  2.2 Coal chemistry Coal is an organic sedimentary rock, hence from a geological point of view, coal is comprised mostly of organic matter (macerals) and of a small portion of inorganic matter (minerals). Macerals are the smallest distinguishable components of organic matter on the microscopic scale. There are three maceral groups: vitrinite, inertinite, and liptinite (exinite). The individual macerals are 7   grouped according to similar origins or similar petrographic properties, such as morphology, reflectance, and color in reflected or transmitted light (Holuszko, 1991). The associations of macerals in different proportions to each other and with variable amounts of mineral matter on a macroscopic scale are defined as lithotypes, or microlithotypes, when observed on a microscopic scale.    As discussed in Section 2.1, the evolution of the chemical composition of coal has involved a steady increase in its aromatic structure and a simultaneous decrease in its oxygenated functional groups. The content of the aliphatic groups reaches a maximum in low-volatile bituminous coals and subsequently decreases in higher rank coals.   Chen et al. (2012) have concluded that the evolutionary trend of functional groups in vitrinite is similar to the trend for bulk coal that vitrinite originated from. With respect to elemental composition, there is a progressive decrease in elemental O content and an increase in C content with increasing coal rank (Stach and Murchison, 1982).  Within the iso-rank, the macerals are not only petrographically distinct but also have diverse chemical compositions and physical properties. Previous studies have explored the chemical functional groups in coal macerals via Fourier Transform Infrared spectroscopy (FTIR) (Chen et al., 2012, Chen et al., 2013a, Guo and Bustin, 1998, Morga, 2010, Iglesias, 1995, Mastalerz and Bustin, 1993b, Mastalerz and Bustin, 1993a). However, micro-FTIR has commonly been conducted on micro sized spots of pure macerals, it has never been accomplished on a larger area.   8   Coal maceral chemistry  plays a significant role in many utilization processes such as conversion and carbonization (Kaegi et al., 1988). Vitrinite is the most abundant maceral in coals and it is the most desired component for coking coal, since it contributes to the plasticity of coal upon heating. Liptinite contains the largest amount of long-chain, unbranched aliphatics in comparison with other maceral groups. The contribution of tar and oily byproducts from the breakdown of such liptinite helps increase plasticity during  the coking process (Walker and Mastalerz, 2004). Inertinite has been found to be the least aliphatic and most aromatic of all the maceral groups (Iglesias, 1995, Chen et al., 2012). It has been found to be the most thermally stable structure out of all  macerals (Vassallo et al., 1991).  The mineral matter of coal is derived from the inorganic constituents of the precursor plants, from other organic materials and from the inorganic components transported to the coal bed (Rao, 1973, Stach and Murchison, 1982). Most of mineral matter is associated with coal macerals. The amount of minerals and the distribution of mineral matter grains both contribute to the heterogeneity of the coal surface on a number of levels. However, this thesis will not focus specifically on the influence of mineral matter on the hydrophobicity of coal surface. For the purpose of this work, the areas that were used for analysis were selectively chosen to represents spots free from invisible minerals under the microscope. The instances where the effects of mineral matter were observed were further investigated by SEM.  9   2.3 Heterogeneity of coal surface Coal surface is heterogeneous at different levels. In simple terms, heterogeneity of coal results from a variation in petrographic composition, as well as the size and the distribution of mineralogical inclusions (Laskowski, 2001a, Laskowski and Walters, 1992).   As shown in Figure 2.3, surface properties of coal are determined by the mineral matter to a large extent, the numbers and types of functional groups (related to organic matter), the pores, and the associations between macerals and minerals. Coal surface heterogeneity is complex and poorly reproducible at both the molecular and microscopic levels. At the molecular level, it can be depicted as a hydrocarbon matrix that contains various functional groups, the contents of which vary with rank or within iso-rank (Blom et al., 1957). At the microscopic level, heterogeneity is affected by maceral composition (Horsley and Smith, 1951), mineral matter inclusions (Gosiewska et al., 2002),  and porosity (Laskowski et al., 2002).   Figure 2.3 Schematic representative of coal surface (Laskowski, 2001a).  A number of studies have been conducted on the factors that affect coal surface heterogeneity. The microscopically distinguishable components (macerals) of coal have diverse chemical compositions and physical properties, hence the petrographic composition contributes to the 10   heterogeneity on microscopic scale (Mastalerz and Bustin, 1993b, Chen et al., 2013a, Holuszko and Mastalerz, 2015).   Coal is a naturally porous substance. Berkowitz (1979) concluded that the abundance of pores and their size is related to the rank of coal. The porosity of lower-rank coal is primarily due to the presence of macrospores. Transitional pores and microspores are usually typical for higher rank coals. Macerals such as semifusinite and fusinite are characterized by their natural porosity due to their origin (wood cell structure), hence the heterogeneity of coal related to the porosity will depend on the rank and maceral composition (Stach and Murchison, 1982, Mastalerz and Bustin, 1993a).  O’Brien et al. (2007)  have developed a semi-automated method for coal grain analysis that renders an assessment of the extent of the surface heterogeneity possible (Ofori et al., 2006). Connecting the heterogeneity of coal with its hydrophobicity is significant for predicting the performance of coal in the preparation processes or other utilization processes. The heterogeneous nature of coal, at both the macroscopic and microscopic levels, is the main reason for the variation in the wetting properties of coal from sample to sample representing the same coal.   It has been established that whereas coal macerals are mainly hydrophobic, most of the mineral matter (ash) that forms inclusions in coal macerals are hydrophilic (Arnold and Aplan, 1989, Berkowitz, 1979). As ash content increases, coal becomes more hydrophilic (Laskowski et al., 2002). Even small amounts of minerals associated with macerals can change the wetting characteristics of a coal surface significantly (Laskowski, 2001a, Laskowski and Walters, 2007). 11   Small mineral grains and their distribution have a significant effect on coal surface properties and its heterogeneity.  Gosiewska et al. (2002) concluded that hydrophilic grains larger than about 0.1 μm significantly affect the wetting characteristics of the coal surface. This is due to the variation in heterogeneous patterns for microscopic areas that are exposed to the probing liquid in close vicinity to the three-phase contact line. The following section will discuss wettability of coal surface.  2.4 Wettability of coal surface Froth flotation is used as a main process through which to upgrade the fines of higher rank coals. The primary requisite for flotation is the replacement of surrounding water at the coal particles to surface to allow attachment to the air bubble. The effectiveness of flotation relies on the relative strength of the particle-air bubble and particle-water interactions. The interaction of the coal surface with water is broadly referred as coal wettability. When the minerals (particles) interact strongly with surrounding water, they are called “hydrophilic” or “wettable by water”. Hydrophobic minerals (particles) interact weakly with water, but they interact strongly with air bubbles. The organic components of coal are usually hydrophobic and float easily. The minerals associated with coal are mostly hydrophilic and non-floatable. Therefore, an understanding of coal wettability by water (coal/water interface) is of utmost importance in coal flotation.   Theoretically, the wetting process occurs when the adhesion force between a solid and a liquid is greater than the cohesion force between the liquid’s molecules. The work of adhesion is the difference of interfacial energy between the adhering and individual phases, such as a liquid on a solid (Mohammadi-Jam et al., 2014). This involves the work required to detach a column of a 12   liquid from a column of a solid with a unit cross-sectional area (Pawlik, 2008)). The work of adhesion of a liquid with a solid is related to the various interfacial tensions, and can be seen through the following equation: 𝑊𝑎𝑑ℎ =  𝛾𝑆0 + 𝛾𝐿𝑉 − 𝛾𝑆𝐿                      (1) where 𝛾 denotes surface tension (or energy) [mJ ∙ m−2] at an interface, and the subscripts LV stands for liquid-vapour, SL for solid-liquid and S0 for the solid placed in vacuum.  Young proposed the idea of observing a three phase contact angle created by a fluid, sitting on a smooth surface in air, known as Young’s Equation. 𝛾𝐿𝑉 cos 𝜃 =  𝛾𝑆𝑉 − 𝛾𝑆𝐿                       (2) where θ denotes the contact angle at the three phase contact point.  Combining Young’s Equation with Eq. (1), the work of adhesion provides a direct indication of the wettability of a material. And the difference (𝛾𝑆𝑂 − 𝛾𝑆𝑉) is normally considered 0.  𝑊𝑎𝑑ℎ =  𝛾𝐿𝑉(1 + cos 𝜃)                     (3) where 𝛾𝐿𝑉 and θ can be measured. Therefore, the work of adhesion of water to hydrophobic solids can be estimated. The most common method for characterizing wettability is through the measurement of contact angles.   A fundamental understanding of coal surface chemistry and wettability is paramount not only with respect to coal flotation, but also in other utilization processes, including oil agglomeration, dust abatement, and the preparation of coal-water slurries. As discussed in the previous sections, coal 13   surface properties are determined by the coal hydrocarbon skeleton (coal rank), functional groups on macerals and mineral matter associated with coal.  The hydrophobicity of coal surface has long been the subject of numerous studies. Various researchers  have studied the relationship between hydrophobicity and coal rank (Elyashevitch et al., 1967). It was concluded that lower rank coals are more hydrophilic, which correlated well with oxygen content in coal (Whitehurst et al., 1980, Gutierrez-Rodriguez and Aplan, 1984).The oxygen functional groups in the coal structure provide sites for water adsorption on the coal surface (Laskowski and Walters, 1992).  Horsley and Smith (1951) have shown that vitrain (a concentrate of vitrinite) is the most hydrophobic, followed by clarain (vitrinite +inertinite), durain (vitrinite +inertinite + mineral matter), and fusain (inertinite). Arnold and Aplan (1989) observed that the hydrophobicity of coal macerals follows the pattern: exinite > vitrinite > inertinite.  A wide variety of indicators and methods have been used to study and to assess the wetting characteristics of coals, including contact angle, film flotation, displacement pressure, penetration rate, heat of immersion, immersion/sink time, imbibition time, and induction time measurements (Good and Lin, 1976). However, contact angle has been found to be a useful and straightforward indicator in providing information on the wetting characteristics of coal surface due to its close relationship between the contact angle and the floatability of coal particles.   14   O’Brien et al. (2007) proposed Coal Grain Analysis (CGA) method to measure the distribution of macerals and minerals on coal surface. Later, Ofori et al. (2010) combined the composition information derived from the Coal Grain Analysis method with the contact angles measured at the spot where the semi-automated petrographic analysis is conducted. In their study, the advancing and receding contact angles of vitrinite and minerals were directly measured. The contact angles of finely dispersed liptinite and inertinite, could not be directly measured, hence they were calculated by least squares fitting via Cassies’s equation. Using this equation, the advancing and receding contact angles of heterogeneous surfaces with varying amounts of macerals were also derived. The fractional areas of the different macerals were determined by CGA semi-automated petrographic analysis on the spots where contact angles had been measured. This methodology provided a robust pathway for estimating the hydrophobicity of heterogeneous coal particles via Cassie’s equation, thereby deriving the basis for the kinetic flotation model as described by Ofori et al. (2014).   Direct characterization of the surface functional groups of individual coal macerals offers more detailed information on coal’s chemical heterogeneity than do any measurements of bulk properties of coal. Fourier Transform Infrared (FTIR) spectrometry can quantify the abundance of chemical functional groups and is one of the most versatile analytical techniques for determining coal structure (Mazzeo and Joseph, 2007, Skrtic et al., 2004, Iglesias, 1995). Chen et al. (2013b) have suggested a novel reflectance based micro-FTIR mapping method to characterize the abundance of functional groups in coal macerals while taking pictures of the area where FTIR measurement is being conducted. This provides high-resolution information on the chemical properties of coal macerals.  15    In this thesis, a new experimental methodology has been developed to assess coal surface composition in relation to its hydrophobicity. This methodology combines an assessment of the extent of surface heterogeneity by the distribution of functional groups with contact angle measurements, using the axi-symmetric drop shape analysis technique. Contact angle measurements are taken on optically uniform macerals and macerals associated with each other where the distribution of functional group abundance is obtained through micro-FTIR mapping. The semi-quantitative FTIR ratios calculated based on Fourier transform infrared spectral analysis are correlated with the contact angle measured at that position. Since, contact angle is the most direct parameter that can be used to characterize the hydrophobicity of coal, connecting the chemical information from micro-FTIR and the contact angles helps to explain the hydrophobicity of coal as well as of individual macerals. This type of information could provide suggestions regarding the selectivity of flotation reagents. While selectivity in floating certain petrographic components could be obtained with the right chemical reagents, establishing which reagents to use through an understanding of the chemical nature of coal macerals could become the next step in fine coal processing as suggested by Holuszko and Mastalerz (2015).   2.5 Contact angle and micro-FTIR techniques 2.5.1 Contact angle measurement In most cases, the techniques for contact angle measurement can be divided into two major categories: direct contact angle measurement from which angle values are obtained directly by viewing the drop profile, e.g. sessile and captive bubble (Taggart and Taylor, 1930, Wark and Cox, 1934), the tilted plate method (Adam and Jessop, 1925) and the compressed pellet method 16   (Shuttleworth and Bailey, 1948), and indirect contact angle measurement from which contact angle values are calculated and deduced, e.g. the Wilhelmy plate method (Wilhelmy, 1863), interference microscopy (Ducker et al., 1994) and film flotation (Laskowski et al., 2002).  For flat solid surfaces, the most widely used technique for contact angle measurement is through a direct measurement of the angle by viewing the drop profile. Brady and Gauger (1940) showed that a telescope goniometer can be used to view a drop placed on a polished surface, and the profile of the contact can be measured. The sessile drop and captive bubble methods are the most widely used techniques. Figure 2.4 shows an FTA drop shape instrument and an example of the sessile drop and captive bubble methods.   The sessile drop technique is straightforward, and requires only small quantities of liquid and small areas of solid for a measurement if high accuracy is not required. The captive bubble technique is more advantageous than sessile drop method since it minimizes the contamination that can be caused by airborne substances. Also, this technique is less sensitive to the imperfections of coal sample surface  while  humidity is constant (Drelich et al., 1997),. Most importantly, the captive bubble technique is more relevant to the environment representing flotation conditions, hence, the majority of contact angle measurements are carried out using the captive bubble technique.    Drelich et al. (1997) recommended an improved sample preparation methodology for contact angle measurements using the captive bubble and sessile drop techniques. Many negative effects were eliminated when this sample preparation method was used.   17   For a real liquid/solid system, not all of the experimentally measured or observed contact angles are reliable and appropriate. These range from receding (smallest) contact angle to advancing (largest) contact angle. Their names are derived from the fact that an advancing angle is measured when the periphery of a drop advances over a surface, and a receding angle is measured when the periphery of a drop recedes over a surface, and is measured by pulling it back. The difference is known as contact angle hysteresis, and it provides a useful measure of coal surface heterogeneity (Hanning and Rutter, 1989, Lam et al., 2002).  𝜃ℎ𝑦𝑠𝑡 = 𝜃𝑎 − 𝜃𝑟 The contact angles hysteresis determined for the discrete coal maceral groups and minerals is used to estimate the contact angles of heterogeneous particle classes so that the responses of the coal components during flotation separation can be predicted. Adamson and Gast (1999) proposed three major factors that can be attributed to hysteresis: contamination of solid surface, surface roughness, and surface heterogeneity.  Liu et al. (2015) used an FTA1000 Drop Shape Analyzer to investigate the role of colloidal precipitates in the interfacial behavior of alkyl amines at gas–liquid and gas–liquid–solid interfaces as shown in Figure 2.4. A droplet of test solution was dispensed from the tip of a straight stainless steel needle (17-gauge with an inner/outer diameter of 1.194/1.499 mm) on a dry quartz slide that had been washed in a mixture of hydrochloric acid and hydrogen peroxide. The evolution of contact angles for different test solutions was measured as a function of time. This procedure is adopted for contact angle measurements in this thesis.  18    Figure 2.4 FTA1000 drop shape analyzer (left) and an example image captured for surface tension analysis (right) (Liu et al., 2015).  2.5.2 Micro-FTIR technique Fourier Transform Infrared (FTIR) spectroscopy has long been used to investigate coal characterization (Mastalerz and Bustin, 1993b). In the early 1990s, FTIR was widely utilized to quantify the abundance of chemical functional groups. The basic semi-quantitative analysis of the infrared spectra of three maceral groups provides complete information on the functional groups of pure macerals from different coals (Iglesias et al., 1995), as well as information on the evolution of coal structure during the coalification process (Ibarra et al., 1996), The development of accessories, such as the infrared microscope, as well as spectral handling and processing techniques, allow FTIR techniques to be applied to coal characterization dealing with all kinds of experimental conditions. The characteristics of all techniques are discussed in Table 2.2.    19   Table 2.2 Comparison between the most frequently used Fourier Transform Infrared spectroscopy techniques related to sample preparation, resolution, sensitivity and other aspects.   KBr-FTIR yields an average sample analysis rather than the composition of distinct genetic components. As a result, it is hard to characterize small areas such as those represented by macerals, which are difficult to isolate as pure species (Chen et al., 2014). On the other hand, micro-Fourier Transform Infrared (FTIR) spectrometry is uniquely qualified to investigate the in situ chemical Technique Sample Preparation Resolution Sensitivity Distortion Others KBr-FTIR KBr Pellet Average Higher absorbance of aliphatic bands and lower absorbance of aromatic bands compared to reflectance  micro-FTIR Kramers-Krönig applied Bulk analysis; semi-quantitative Reflectance micro-FTIR Polished block sample ~20μm Higher absorbance in 700-900 cm-1 than in transmission;  reduced influence of mineral matter and long aliphatic chains than in KBr-FTIR Kramers-Krönig applied In situ analysis; semi-quantitative Transmission micro-FTIR Thin section (< 30μm) ~20μm Higher quality than in reflectance. Stronger absorbance of aliphatic bands than aromatic bands Kramers-Krönig applied Thin section required; semi-quantitative ATR-FTIR Polished block sample 25~30μm Higher sensitivity and signal-to-noise ratio compared to micro-FTIR No significant spectral distortion The objective must contact the sample 20   properties of small-size macerals and to characterize areas as small as 20μm. In situ techniques are based on high-resolution point analyses on polished surfaces of coal and therefore (a) avoid the difficulty of mechanically isolating individual macerals; (b) yield far more detailed information on the macerals’ heterogeneity than do bulk measurements; and (c) can document intermaceral zonal heterogeneities at a microscopic level.   Micro-FTIR can be performed under reflectance or transmission modes. Although the transmission mode yields spectra of higher quality than does reflectance micro-FTIR, the sample sections required for this technique are thin, hence difficult to prepare. The ability to investigate the exact same maceral area in standard reflected light microscopy renders micro-FTIR technique highly valuable (Chen et al., 2013b, Mastalerz and Bustin, 1995). However, micro-FTIR also has its limitations and cannot be applied in all cases (Iglesias et al., 1995). For coal conversion and utilization, microscale characterization of the different maceral groups is not sufficient as it is difficult to predict the behavior of the entire material. This is due to the fact that the chemical properties between macerals and within individual macerals in iso-rank coal are not uniform. In such cases, the bulk analyses are preferred.   The Attenuated Total Reflectance, ATR-FTIR,  was developed to study maceral structure (Mazzeo and Joseph, 2007, Thomasson et al., 2000). As compared to other micro-FTIR techniques, in the attenuated total reflectance (ATR) method, crystal is brought into contact with the sample while the FTIR spectrum is collected, allowing spectra with improved signal-to-noise ratio to be obtained. The major disadvantage of ATR-FTIR is that the objective must contact the sample and there is 21   the possibility of damage and contamination to the sample’s surface. The following discussion is based on previous research with respect to reflectance micro-FTIR spectra.  Due to the fact that no calibrations have been made between reflectance micro-FTIR spectra and the absolute values of aromatic and aliphatic hydrogen in coals of various ranks, at present this method cannot be regarded as quantitative. However, combining KBr-FTIR and micro-FTIR analysis allows indirect quantitative characterization of functional groups in macerals, yielding both aromatic and aliphatic H contents by measuring regions between 4000-500 cm-1 with the bands assigned as prescribed by (Chen et al., 2015, Chen et al., 2012, Chen et al., 2013a, Mastalerz et al., 2013, Guo and Bustin, 1998, Morga, 2010). The most widely used IR signals and derived from it chemical functional groups are listed in Table 2.3. The major peaks in the absorption regions are also discussed and summarized.            22   Table 2.3 Absorption bands observed in the FTIR spectra of coals based on previous works.  Wavenumber (𝐜𝒎−𝟏) Assignment Peaks 3300 Hydrogen-bonded OH  3100-3000 Aromatic CHx stretching - Peak at 3030 or 3080 c𝑚−1 3000-2800 Aliphatic CHx stretching - Five major sub-absorption peaks (2950-2975, 2915-2940, 2880-2890 and 2840-2870 c𝑚−1) are resolved due to asymmetric CH3, CH2 stretching, CH stretching, symmetric CH3 and CH2 stretchingTwo or three overlapping bands at about 2920 and 2850 cm-1 because aliphatic CH3, CH2, CH groups all contribute to the intensity of these bands 1800-1650 C=O (Oxygenated groups) - Peak at 1710-1700 c𝑚−1is attributed to C=O stretching in ketone, aldehyde, and carboxylic structures (aromatic carbonyl/carboxyl C=O groups) - Peak at 1740-1730 c𝑚−1is due to aliphatic C=O ester substances. 1650-1500 Aromatic C=C ring stretching - Peak at 1600 c𝑚−1 can be explained in terms of the presence of phenolic groups; - Peak at 1500 c𝑚−1is not present because of the substitution of benzene ring 1450-1500 Aliphatic CHx stretching out of plane deformation The shift of CHx deformation from 1460 to 1450 cm-1 reflect a trend towards shorter aliphatic chains, which is due to aliphatic chain groups in liptinite that are easily oxidized to form aliphatic acid (or ester) C=O groups.    23    None of the above techniques are quantitative. Numerous semi-quantitative ratios (Table 2.4) have been used to characterize the chemical properties of macerals in previous research (Chen et al., 2012, Hacura et al., 2003, Walker and Mastalerz, 2004, Morga, 2010, Lin and Ritz, 1993, Mastalerz and Bustin, 1993b). The relatively more intense and stable absorbance peaks are discussed in following table. Wavenumber (𝐜𝒎−𝟏) Assignment Peaks 1000-900 CH2 deformation in plane - Peak at 910 c𝑚−1 presents the CH2 deformation in normal olefin; - Peak at 950 c𝑚−1 may be due to CH2 deformation in vinyl-and trans-substituted olefins; - Peak at 970 c𝑚−1 reflects CH2 deformation in trans-olefin 900-700 Aromatic CHx out of plane deformation The region is influenced by mineral matter and long aliphatic chains; - Band at 870 c𝑚−1 suggests the presence of pentasubstituted aromatic rings containing isolated CH bonds - In 850-770 c𝑚−1,the out of plane vibrations from two- and three-adjacent aromatic CH groups overlapped - Peak at 750 c𝑚−1 reflects the ortho substitution of aromatic rings because of absence in rang 700±10 c𝑚−1 - Peak at 730-720 c𝑚−1 might be due to CH2 rocking in long chain alkanes that have four or more methylenes in their molecular structures 24   Table 2.4 Semi-quantitative ratios derived from FTIR spectra based on previous research.  Semi-quantitative Index Index Calculation  Aromaticity 1 𝐶𝐻𝑎𝑟(3000-3100 c𝑚−1 )/                      𝐶𝐻𝑎𝑙 (2800-3000 c𝑚−1) Estimate the concentration of aromatic and aliphatic hydrogen functional groups Aromaticity 2 𝐶𝐻𝑎𝑟 out of plane deformation(700-900 c𝑚−1)/      𝐶𝐻𝑎l (2800-3000 c𝑚−1) Degree of condensation 1 𝐶𝐻𝑎𝑟(3000-3100 c𝑚−1 )/                     C=Car (1500-1650 c𝑚−1) Degree of substitution and condensation of the aromatic rings Degree of condensation 2 𝐶𝐻𝑎𝑟 out of plane deformation(700-900 c𝑚−1)/   C=Car (1500-1650 c𝑚−1) Aliphatic chain length C𝐻2(2915-2940 c𝑚−1)/                 𝐶𝐻3(2950-2975 c𝑚−1) Estimate the length and degree of branching of aliphatic side-chain; relate to oil-proneness Factor A 𝐶𝐻𝑎𝑙 (2800-3000 c𝑚−1)/                        [𝐶𝐻𝑎𝑙 (2800-3000 c𝑚−1)+ C=Car (1500-1650 c𝑚−1)] Represent changes in the relative intensities of aliphatic groups; assess the hydrocarbon-generating potentials; Factor C C=O (1650-1800 c𝑚−1)/                      [C=O (1650-1800 c𝑚−1) + C=Car (1500-1650 c𝑚−1)] Represent changes in the C=O groups; demonstrate kerogen-type; reflect coal’s maturation level Others C=O (1650-1800 c𝑚−1)/                     C=Car (1500-1650 c𝑚−1)   C=O (1650-1800 c𝑚−1)/                        (C𝐻2 + C𝐻3)  25    With respect to the evolution in maceral chemistry, Chen et al. (2012)  found that the intensity of absorbance decreases in aliphatic stretching band (2800-3000 c𝑚−1) and carboxyl/carbonyl band (1710 c𝑚−1) and increases in aromatic bands (3000-3100 c𝑚−1and 700-900 c𝑚−1). The decrease of carboxyl/carbonyl band (1710 c𝑚−1) can be explained in terms of decarboxylation and the removal of the carbonyl group from ketones and aldehydes (Iglesias et al., 1995). The semi-quantitative FTIR ratios also reflect a similar trend in functional group abundances in bulk coals. The aromaticity and condensation of aromatic rings increases with the increasing rank of coal samples, whereas the aliphatic chain length and ‘C’ factor decreases. The ‘A’ factor initially rises in low rank and later decreases in higher-rank coals (Chen et al., 2012).  FTIR spectroscopy has widely been used to study the maceral chemistry of coals from various locations, thus representing variable sedimentary environments, maturation conditions and most importantly, age and organic precursors. Based on these previous studies some general trends in chemical properties of individual macerals can be summarized as shown in Table 2.5 (Chen et al., 2013a, Niekerk et al., 2008, Guo and Bustin, 1998, Iglesias et al., 1995).        26   Table 2.5 The characteristics of each individual maceral and corresponding functional group abundance.  Maceral Groups Macerals Characteristics Functional Group            (iso-rank) Vitrinite Telocollinite - Intermediate - Higher aromaticity than liptinite and lower aromaticity than inertinite  Desmocollinite  Inertinite Semifusinite - Greater portion of aromatic functionalities - Highest degree of condensation of aromatic domains and lowest hydrocarbon generating potential Lower aromaticity and condensation of structure than fusinite Fusinite Higher aromaticity and condensation of the structure than semifusinite Liptinite  Sporinite - Greater numbers of long chain aliphatic - Fewer aromatics and a broader range of oxygen-containing groups - Highest hydrocarbon generating potential Aliphatic components are the shortest aliphatic chained and most branched Resinite Intermediate Alginite Strongest aliphatic and least aromatic.  Research performed in the early 1990’s used physically separated macerals and established chemistry of individual macerals. Most of these studies were conducted on vitrintie, which can be easily separated using density gradient separation techniques. Iglesias et al. (1995) conducted a FTIR study on pure vitrains from coals of varying rank. An understanding of the vitrinite chemical composition is important since it is the major maceral in most of the coals.  27    Guo and Bustin (1998) investigated the chemical composition of liptinite in a variety of coals   from high to medium volatile bituminous rank. Compared to the vitrinite within the same rank, the liptinite macerals are characterized by stronger aliphatic CHx absorptions, less intense aromatic C=C ring stretching and aromatic CHx out of plane deformation. The bands in 1000-900 c𝑚−1 that are due to aliphatic CH2 vibrations in olefins and in 730-720 c𝑚−1 are due to 𝐶𝐻2 vibration in long chain aliphatic substances, are characteristic of liptinite macerals.   The characteristics of semifusinite and fusinite from inertinite group have been studied by several authors (Mastalerz and Bustin, 1997, Morga, 2010, Niekerk et al., 2008). A typical spectrum of semifusinite contains several bands of absorption. They are assigned to OH groups, aromatic CHx stretching, aliphatic CHx stretching, aromatic carbonyl/carboxyl C=O stretching and C=C ring stretching. Fusinite spectra is distinguished by an intense band of aromatic CHx out of plane deformation. Semifusinite is characterized by lower aromaticity and a lower level of condensation of the structure compared to fusinite. The details of chemistry and resulting properties for various macerals derived from FTIR studies are presented in Table 2.5.  Micro-FTIR mapping is a novel methodology used for the micro-scale characterization of functional group abundance in coal macerals. The combination of reflectance micro-FTIR and visible light microscopy makes it possible to map the abundance of functional groups across small areas on micro scale. This technique has been widely used in many fields including for medical applications (Skrtic et al., 2004), and metal and composites materials (Mazzeo and Joseph, 2007, Tesch et al., 2001). Chen et al. (2012) first applied reflectance micro-FTIR mapping to the 28   characterization of some common macerals. Based on previous studies, this technique can be used to:  Detect the chemical heterogeneity in optically uniform macerals.  Assess the distribution of functional groups in coal macerals.  Investigate chemical interactions among different macerals.   Chen et al. (2013b) concluded that vitrinite exhibits significant heterogeneity even within a petrographically homogenous area, and resinite can influence the chemistry of adjacent vitrinite by contributing some of its mobile aliphatic moieties. Micro-FTIR mapping of coal samples further confirms the aliphatic character of resinite and the aromatic nature of funginite (liptinite group macerals). In addition, chemical mapping of resinite and adjacent vitrinite shows that vitrinite immediately adjacent to resinite displays a higher aliphatic CHx stretching intensity than more distant vitrinite, suggesting that the chemical components from resinite can diffuse over short distances into adjacent vitrinite, more specifically, causing hydrogen enrichment. This way, the chemical map of resinite and associated vitrinite provides direct evidence of the intermaceral effects occurring during the peat forming stage, or later during coalification.  As discussed in earlier sections of this chapter, previous studies have focused on the micro-FTIR characterization of pure macerals, hence a micro-scale approach of the developed technique was very appropriate. However, these methodologies were not appropriate for collecting chemical information from larger areas. In this study, the micro-FTIR measurements were used to assess the chemical composition of coal surface in order to build a correlation between chemical compositions on the same area, and area where contact angle has been measured. This has never 29   been accomplished before. As a consequence, the chemical data had to be collected on millimeter size areas. The new methodology was developed for this purpose based on the micro-FTIR technique developed by Chen et al. (2012). The following chapters provide a detailed description of this new methodology, which can be used to measure surface chemical composition on the millimeter scale.  30   Chapter 3: Experimental Procedures  3.1 Introduction In this research, contact angle was used to assess the hydrophobicity of coal surface. Micro-FTIR analysis was employed as a method to provide information on the chemical composition and functional group distribution of the coal surface as well as the functional group distribution of individual macerals on areas that were being used for contact angle measurements. These two techniques are referred to as in situ techniques since both of the measurements are performed almost simultaneously on the surface that is being evaluated rather than relying on the chemical information from the bulk coal, as has been done in previous studies where the contact angle and chemical composition of coal were correlated. The key point of this proposed approach is to ensure that the contact angle and FTIR analysis are conducted on the same spots. In addition, the image analysis of the coal surface was also introduced in order to provide information on the petrographic composition of predetermined areas that were used for contact angle measurements. The chemical composition derived from FTIR spectra along with the petrographic composition help explaining hydrophobicity and its complexity as it relates to the coal surface. Additionally, area Micro-FTIR maps and line maps were also obtained from pure macerals to provide more in depth information on the chemical heterogeneity of pure macerals and its effect on the overall hydrophobicity of coal.  The methodology for the experimental approach used in this research is presented in Figure 3.1 The following experimental steps were taken to complete this research:   Sample preparation for contact angle and micro-FTIR analysis.  Areas for both type of measurements were outlined using a reflected light microscope. 31    Image analysis and reflectance measurements were carried out.  Contact angle measurements were done using both sessile drop and captive bubble methods.  Micro-FTIR chemical composition analysis and micro-FTIR mapping were conducted on the same areas that the contact angle was measured, as well as on pure macerals.  Figure 3.1 Methodology for experimental approach.  In order to conduct contact angle measurements on the coal surface, blocks of coals were prepared according to previously-used methodologies (Drelich et al., 2000, Drelich et al., 1997). Detailed procedures are provided in Section 3.2. The vitrinite reflectance of each coal sample was measured to determine the rank of the coal. Areas on each coal block were marked for contact angle measurement, and the same marked areas were used for micro-FTIR analysis. Image analysis using reflected light microscopy was performed to obtain information on the petrographic composition of each area on the coal surface that was analyzed. Contact angles were measured first on the marked areas and then micro-FTIR analysis was performed on the same areas.  32   The challenging aspect of the proposed approach was that the measurements of contact angle either through the sessile drop or captive bubble method were done on a millimeter scale while the micro-FTIR chemical information was collected on a micro scale. Figure 3.2 shows the marked area of 4×4 mm and the drop size of the bubble is 3 mm. The aperture for FTIR analysis (effective area for measurement) is usually 50×50 μm.In order to measure the area required for contact angle measurement, the FTIR aperture had to be increased to a maximum size 100×100μm and 12 points were chosen for FTIR analysis. In order to cover most of the area measured for contact angle, points were evenly distributed on the marked area as depicted in Figure 3.2.  Figure 3.2 Schematic of contact angle measurement area and micro-FTIR points.  3.2 Sample preparation Coal samples representing two different ranks were selected for this investigation. The average mean vitrinite reflectance 𝑅𝑜 of higher rank coal was 1.6%. This coal was from southeast British Columbia Mist Mountain Formation and most of the samples used in this research were dull looking. The lower-rank coal samples with a mean vitrinite reflectance of 0.6% were obtained 33   from Indiana’s coalfields, and were provided by Dr. Maria Mastalerz from the Indiana Geological Survey (IGS) of Indiana University, USA. They were collected from Danville, Hymera and Springfield coalfields. In contrast, samples with higher vitrinite content were bright-looking as found in low rank coal.   Samples for contact angle measurements, micro-FTIR and vitrinite reflectance analyses were prepared as polished blocks. The same coal blocks were used for the subsequent contact angle measurements. Contact angle measurements are strongly influenced by mineral matter inclusion (Klassen, 1953), petrographic composition (Sun, 1954) and sample preparation. To minimize any effects related to sample preparation, Drelich et al. (2000) recommended an improved methodology for coal surface preparation prior to measuring the contact angles. This includes polishing the surface with abrasive paper, alumina powder, and a cloth, followed by ultrasonic and mechanical cleaning. As a result of this sample preparation method, the effects of the surface roughness scrutinized  by Wenzel (1949) are significantly eliminated. Figure 3.3 below shows the polished blocks of coal that were prepared for measurement and the procedure used in this research was adapted as follows:   Set the sample in polymer resin and wet polish with 120 grit paper to remove extra resin.  Wet polish of the coal sample with 600 and 1200 grit abrasive papers.  Wash coal sample with a stream of water.  Surface polish using 0.05 μm alumina powder (wet conditions).  Wash the coal surface with a stream of water.  Clean the coal sample in an ultrasonic bath filled with water for about 10 min and then washing with water. 34    Wet polish/clean of the coal surface with a polishing cloth (inactive to coal).  Clean the sample in an ultrasonic bath for 4-6 min and then wash with water.  Put the sample into desiccator for 24 hrs.  Figure 3.3 Polished sample blocks for contact angle measurements and micro-FTIR (a) low rank coals with average vitrinite reflectance of about 0.6% (b) high rank coal with average virinite reflectance of about 1.6%.  3.3  Petrographic analysis Measurements of mean maximum reflectance R0 on vitrinite on studied coal samples were performed according to the standard coal petrographic procedures prescribed in ICCP (1963) using a Zeiss RS-III microscope, (IGS, Indiana University, USA). The reflectance measurements were performed using the oil immersion objective because some of the oil may have spread over the areas where contact angle and micro-FTIR were to be measured. For this reason, special caution was needed when choosing the area for taking the reflectance readings. As such, the reflectance readings would not be conducted directly on the area marked for either contact angle or micro-FTIR measurements, but rather had to be taken elsewhere on the polished coal surface (on vitrinite) 35   within a small area further from the selected spots. In order to avoid the contamination caused by oil film, careful cleaning procedures were applied to remove remnants of oil after the vitrinite reflectance measurements.  Figure 3.4 Image analysis window of the microscope software Stream, including maceral distribution and settings for maceral determination.  The maceral analyses for the predetermined areas on the coal samples were performed using reflected light microscope. To ensure that the same spots were analyzed, microscopic images of each of the predetermined areas (4×4 mm) were taken under a Nicolet Continuum microscope operated in connection with the Micro FTIR probe. These images were then analyzed by Stream Motion software by Olympus (Figure 3.4). The Phase Analysis tool in Stream Motion software can discriminate particles based on the gray level.  Petrographic composition information can be obtained based on the semi-automated phase analysis using gray level approach combined with the operator’s ability to distinguish different macerals under the reflected light microscope. Different macerals display a different shades of gray and can be identified by their morphological 36   features, for example, by their cavities in the fusinite. Hence, the operator’s ability to distinguish these features becomes a necessity. Figure 3.4 illustrates the phase analysis applied in this study for maceral determination. The phase analysis provided the estimation of an area of different macerals in composition and fairly accurate textural composition of coal surface. The latter included estimation of the areas occupied by the cracks and holes on the coal surface where the contact angle was to be measured. The image analyses (Figure 3.5) were carried out area by area in order to obtain maceral composition with the best possible precision.    Figure 3.5 Example of image analysis results using Phase Analysis of Stream (a) original coal surface under microscope (b) first ROI area of mostly vitrinite area (c) second ROI area of mostly inertinite. 37    3.4 Contact angle measurement Contact angles were measured using the drop shape method with the use of the FTA 1000 Drop Shape Analyzer (Figure 3.6). The equipment consisted of a manual stage with a specialized illumination source that was situated behind the sample so that the image became a silhouette. A dispenser delivered the drop or air bubble to the sample, and a microscope piece equipped with a camera (the image is turned into an electrical signal that computer uses to reconstruct the image) was used.  Figure 3.6 FTA 1000B Class drop shape analyzer instrument (a) and examples of sessile drop (b) and captive bubble methods of contact angle measurements.  Both captive bubble and sessile drop methods were employed in this study. In the sessile drop method, a droplet of distilled water is generated at the tip of a needle and then placed on a predetermined area of the coal surface. The bottom of the cuvette contains water and the top of the cuvette is covered with paraffin film to create a vapor pressure in order to minimize droplet 38   evaporation. As illustrated by data presented in Figure 3.7, droplet evaporation could be a factor affecting the contact angle measurement. In the captive bubble method, the sample is immersed in the liquid and either attached to the top or laid on the bottom of the cuvette. A small air bubble is produced at the tip of the U-shaped needle using the micro-syringe and placed in contact with the sample surface. In order to place the air drop exactly on the predetermined area, a dental mirror was used to improve the view of sample from below.   Figure 3.7 The effect of evaporation prevention on contact angle using the sessile drop method.  Before collecting final data on the predetermined area, preliminary tests were conducted to investigate the limitations of the contact angle measurements related to the shortcomings of the equipment and the measurement condition. The following sections will discuss test conditions.  39   3.4.1 Drop volume In the sessile drop method, the drop volume needs to be calibrated in such a way that it is neither too large nor too small. If the drop volume is too large, a large enough diameter of needle is needed to support the necessary droplet size. Also, a large drop area will increase the area required for effective micro-FTIR analysis. This is not desirable as it will reduce the precision of FTIR spectra results. However, if the drop volume is too small, the drop will be significantly affected by evaporation.   Drop volumes ranging from 2 μl to 6 μl were tested on spare (additional) samples designated as E2 and E3. The results are shown in Figure 3.8. The data presented here is for five separate contact angle measurements performed individually on different spots on each sample. Due to the heterogeneity of the coal surface, the contact angle values vary significantly. The contact angle measurements are plotted against time and they represent dynamic contact angle. The contact angles with 2 μl , 3 μl  and 4 μl  drop volumes decreased rapidly due to the evaporation and penetration of water into the pores and cracks of the coal surface. The contact angle measurements with drop volumes of over 4μl maintained a relatively constant slope versus time. A drop volume of 5μl was selected to satisfy the requirement of minimizing the measurement area necessary for micro-FTIR analysis.  40    Figure 3.8 Contact angle versus time using different drop volumes: from 2 to 6 𝛍𝐥, on sample (a) E2 and (b) E3.   3.4.2 Other parameters As the example shown in Figure 3.8, the contact angle values measured through the sessile drop method always decreased with respect to time. The effects of evaporation and penetration can be reduced but cannot be fully avoided, even with effective prevention as discussed previously. In contrast, when using captive bubble method, the contact angle values increase before reaching equilibrium. The contact angle measured at 25 seconds was used as the contact angle to characterize the hydrophobicity of the predetermined spots.   The following parameters were used for both methods: syringe capacity of 100μl, an automatic rate of syringe pump in and pump out at 0.08 μl/s, and a needle inner diameter of s 0.152mm.  41   3.5 Micro-FTIR spectra Micro-FTIR was performed using a Nicolet 6700 Spectrometer connected to a Nicolet Continuum microscope operated in reflectance mode (Indiana Geological Survey, Indiana University, Bloomington, IN) as shown in Figure 3.9. The Nicolet Continuum microscope consists of a video camera, a liquid nitrogen-cooled MCT (Mercury Cadmium Telluride) detector, and a motorized mapping stage. The OMNIC software was used for spectral curve-fitting, deconvolution and peak-ware integration. The Atlus software in OMNIC controlled the data collection and data processing of the micro-FTIR mapping and the line mapping. The detailed procedure for obtaining micro-FTIR mapping and line map are attached in Appendix A.    Figure 3.9 Micro-FTIR spectra instruments (a) in Indiana University, Bloomington, IN and an example of OMNIC software possessing the micro-FTIR mapping data (b).  Reflectance micro-FTIR spectra was obtained at a resolution of 4 cm-1 with a gold plate as background. The number of sample scans used was 400 and the obtained spectra were subjected to Kramers-Krönig transformation. For micro-FTIR analysis on predetermined spots, the largest aperture of 100 μm was used and a total of 12 mapping points were evenly distributed on each 42   area of 4×4 mm as illustrated in Figure 3.2. The average spectra were obtained using OMNIC software based on these 12 points of analysis. For FTIR mapping on pure macerals, an aperture of 60 μm and step size of 80 μm were used. For the FTIR line mapping, the step size was reduced to 10 μm. Also, the 3D-image of the integrated area of aliphatic CHx stretching bands, the aromatic CHx stretching bands and the oxygenated groups were obtained with OMNIC.  Table 3.1 Band assignments for the micro-FTIR spectra of coal samples.  Band position (cm-1) Functional Group 3082-3002 Aromatic CHx stretching 2996-2803 Aliphatic CHx stretching 1832-1677 Oxygenated groups 1677-1521 Aromatic C=C ring stretching 904-700 Aromatic CHx out of plane deformation  Micro-FTIR analysis was conducted at 4000-500 cm-1. Table 3.1 lists the observed bands and their designations. As discussed in Section 2.5.2, numerous semi-quantitative ratios were used to characterize the chemical properties of macerals. The most significant semi-quantitative ratios used in this study to characterize the chemical properties of coal surface include:   Aromaticity 2 (CHar stretching out of plane deformation at 904-700 cm-1 versus CHal stretching at 2996-2803 cm-1).  Degree of Condensation (CHar stretching out of plane deformation versus C=C stretching at 1677-1521 cm-1).  Chain length (CH2 at 2942-2902 cm-1 versus CH3 at 2981-2942 cm-1).  CHal stretching versus C=O. 43    3.6 SEM analysis  As shown in Figure 3.10, the Hitachi S3000N, which is a variable pressure Scanning Electron Microscope (SEM), was used to analyze the minerals in the studied coal samples. In variable pressure mode, the system is capable of imaging at a resolution of 4 nm using the backscatter detector. For elemental analysis, an energy dispersive x-ray (EDS/EDX) detector was utilized allowing for a semi-quantitative and quantitative elemental compositional analysis. In this study, the SEM was used to analyze minerals present on the spots of coal sample that were previously analyzed by micro-FTIR and contact angle measurements. The SEM was used to provide additional information on minerals that were otherwise not visible under the optical microscope. The detailed procedure can be found in Appendix B.   Figure 3.10 The Hitachi S3000N Scanning Electron Microscope (Materials Engineering, UBC)  44   Chapter 4: Results  4.1 Petrographic analysis 4.1.1 Vitrinite reflectance Vitrinite reflectance values as measured on vitrinite found on predetermined areas of the studied coal blocks are presented in Table 4.1. Samples 3, 6, 7, 9 and 10 from British Columbia have a vitrinite reflectance of 1.45~1.65%, which can be classified as medium to low volatile bituminous coal. The samples obtained from Indiana Geological Survey Danville 1, Danville 2, Springfield 1 and Hymera 1 had vitrinite reflectance values of ~0.60%, which classifies them as high volatile bituminous C coal. From here on, samples that had higher vitrinite reflectance are referred to as “high rank” coal samples (H1-H8) and the samples that had lower vitrinite reflectance are referred to as “low rank” coal samples (L1-L8). The abbreviations shown in Table 4.1 were used for each predetermined area.   Table 4.1 Vitrinite reflectance and description of analyzed coal marked area.  Samples Area No.               (in short) Reflectance Vitrinite  (%) Coal Rank Sample 3 1-7 (H1) 1.50 Medium to low bituminous C coal Sample 6 1-2 (H2) 1.19 Sample 7 3-2 (H3) 1.39 4-1 (H4) 4-2 (H5) 4-3 (H6) Sample 9 3-1 (H7) 1.33 Sample 10 1-3 (H8) 1.38 Danville 1 1-2 (L1) 0.63 High volatile bituminous C  1-3 (L2) 0.63 45   Samples Area No.               (in short) Reflectance Vitrinite  (%) Coal Rank Danville 2 1-1 (L3) 0.63 High volatile bituminous C 2-2 (L4) Springfield 1 1-1 (L5) 0.59 2-1 (L6) 2-2 (L7) Hymera 1-1-2 1-2 (L8) 0.63  4.1.2 Petrographic characterization The results of the image analysis performed on the predetermined areas are presented in Table 4.2. Image analysis provided the petrographic compositions of the studied spots on the coal surface.  Vitrinite is a commonly occurring maceral in the compositions of both low and high rank coals. It varies from 69%~88% in high rank coal, while it accounts for over 90% in low rank coal as observed in L3 and L4 coal samples. Vitrinite content varies from 75~88% (on area basis) for high rank coal samples, and between 72~93 % for low rank coal samples. The high rank coal (H1-H8) has a higher content of inertinite macerals (up to 12.25%) as compared to the intertinite content in lower rank samples where the highest intertinite content is 5.01% (L5). On the other hand, the L2 coal sample contains the highest percentage of liptinite (18.04%) among all samples.    The most common inertinite group macerals found in these coals are semufusinite, inertidetrinite and fusinite. Liptinite macerals found in these coals were represented mainly by cutinite, sporinite and a small quantity of resinite, Figures 4.1 and 4.2 show the maceral distribution in high rank coal samples and low rank coal samples, respectively. The analyzed areas are characterized by having significant portions covered by fusinite (Figure 4.1 b, d and Figure 4.2 b) as well as semifusinite, 46   while liptinite is finely dispersed with vitrinite (Figure 4.1 a and Figure 4.2 c). As shown in Figure 4.2 (d), samples L3 and L4 are characterized by a large area of microscopically homogenous vitrinite. Compared to high rank coal, low rank coal has lesser amount of semifusinite and a higher content of vitrinite in composition. Inertinite macerals associated with vitrinite and liptinite are shown in Figure 4.2 (a). The fusinite and semifusinite are dispersed with black holes as shown in Figure 4.1 (b). As shown in Figure 4.1 (d), other semifusinite are associated with inertinite, clays or quartz. This was further confirmed by SEM analysis.   Figure 4.1 Photomicrographs of macerals on predetermined spots in high rank coal. (a) Liptinite finely dispersed with vitrinite, (b) fusinite and (d) semifusinite are common in the studied high rank coal.  47    Figure 4.2 Photomicrographs of macerals on predetermined spots in low rank coal (a) Semifusinite, cutinite and vitrinite are associated together in sample L6. (b) Semifusinite is surrounded by vitrinite in sample L7. (c) Cutinite in sample L2. (d) Pure vitrinite associated with some pyrite in sample L3.        48   Table 4.2 Petrographic analysis results of predetermined spots on coal surface (the specific image analysis information is attached in Appendix C).  No. Samples Cracks, holes or quartz Liptinite Vitrinite Inertinite Minerals H1 Sample 3 0.85% 13..63% 78.95% 5.85% 0.00% H2 Sample 6 0.72% 9.51% 88.22% 0.90% 0.00% H3 Sample 7 0.48% 15.01% 82.91% 0.62% 0.00% H4 1.29% 7.45% 78.34% 12.25% 0.00% H5 0.72% 7.93% 84.82% 5.75% 0.00% H6 0.65% 8.80% 81.77% 7.70% 0.00% H7 Sample 9 1.25% 18.98% 68.88% 9.67% 0.00% H8 Sample 10 0.85% 16.34% 75.34% 6.57% 0.00% L1 Danville 1 1.53% 15.06% 72.27% 0.32% 0.01% L2 3.11% 18.04% 77.05% 0.57% 0.01% L3 Danville 2 1.22% 3.07% 93.27% 0.04% 1.09% L4 1.70% 5.28% 90.83% 0.15% 0.47% L5 Springfield 1 4.65% 14.99% 73.72% 5.01% 0.01% L6 1.06% 9.85% 86.52% 2.01% 0.00% L7 2.33% 10.41% 79.25% 3.87% 0.00% L8 Hymera 1 1.60% 14.47% 74.21% 0.29% 0.01%  The petrographic analysis will be used to elaborate on the effects of maceral composition on the coal hydrophobicity and this will be discussed in the following sections of this thesis.  49   4.2 Contact angle measurements  Contact angles were measured on predetermined areas of polished blocks that were prepared from high and low rank coals, as described in Section 3.2. These areas, as discussed previously in Section 4.1, represent spots of varied petrographic composition. It needs to be noted that the precision of the contact angle measurement is greater than the accuracy of these measurements due to the many limitations of the equipment, as well as  the effects related to the measurement process itself (evaporation, inability of control size of the drop/bubble over the time, uneven size of the drop/bubble etc.). To establish optimal conditions for contact angle measurement and to determine reference points for comparison, the sessile drop and captive bubble tests were performed under both static and dynamic conditions. Illustrations of these various test conditions are shown in Figure 4.3 below.  Figure 4.3 Illustration of the four methods used for contact angle measurements (a) sessile-drop technique (static) (b) sessile-drop technique (dynamic) (c) captive bubble technique (static) (e) captive bubble technique (dynamic). 50    4.2.1 Advancing and receding contact angles Advancing and receding contact angles were measured by increasing or reducing drop volume, which include the use of dynamic sessile-drop and captive-bubble techniques as illustrated in Figure 4.3 (b) and (d). Both the sessile-drop and captive-bubble measurements were conducted on the same areas of the polished coal blocks. Using the sessile-drop technique (Figure 4.4), the advancing contact angle was measured as 100°, and the receding contact angle was measured as 40°. Using the captive-bubble technique (Figure 4.5), the advancing and receding contact angles were 80° and 60°, respectively. The difference of 60° between the advancing and receding contact angles in the dynamic sessile drop is larger than the difference of 40° in the dynamic contact angle measured by the captive bubble. The difference between advancing and receding contact angles defines contact angle hysteresis, and usually is used to assess the surface heterogeneity. A larger contact angle hysteresis, represents a more heterogeneous coal surface than does one with smaller hysteresis. The sessile drop and captive bubble techniques give different values of contact angle hysteresis with respect to the same block of coal. Also, data obtained from measurements using the captive bubble technique is more consistent when compared to data obtained from the tests done using the sessile drop technique, especially with respect to receding contact angles.   51    Figure 4.4 The advancing and receding contact angles obtained from sessile drop measurements and the corresponding four points on the plot on which contact angles were measured (Point A, B, C and D).   Figure 4.5 The advancing and receding contact angles obtained from captive bubble measurement and the corresponding four points on the plot for which contact angles were measured (Point A, B, C and D).    52   The following should be noted with respect to the advancing and receding contact angle measurement procedures,   With increased water/air, the drop/bubble will grow unevenly around the tip. This will increase the difficulty of obtaining accurate contact angles  The dimensions of the drop contact with the coal surface changes as water/air advances or recedes. It has not been possible to place the drop/bubble accurately (with the micrometer precision) on the predetermined areas.  The advancing and receding contact angles provide a range of contact angle values, which also can reflect the significant heterogeneity of the coal surface.  Accordingly, the 60° difference in sessile drop for the same spot on the coal surface could reflect the significantly heterogeneous character of the coal surface. Another issue affecting the hysteresis arises when the drop is not symmetrically positioned around the needle during test, particularly if the drop dimensions are comparable in diameter to that of the needle. This will lead to a difference between the angles at the left and right sides. All of the above mentioned effects will lead to inaccuracy with respect to contact angle measurements. Nevertheless, the advancing and receding contact angles provide a range of contact angle values that can be used for evaluating the degree of hydrophobicity of the coal surface. While the advancing and receding contact angles can be measured across the desired area, and the averaged value can be assigned to assess the hydrophobicity of the entire block of coal, it will not reflect the true nature of the coal surface with its complex heterogeneity.   53   For the purpose of this research contact angle values derived from the static sessile drop and captive bubble methods were used for correlating with the chemical composition of the coal surface as derived from the micro-FTIR technique. These were found to be easier to compare when using the measurements that represent the advancing and receding contact angle values for the predetermined spots. The details and results of the static sessile drop and captive bubble techniques are presented in the following section.  4.2.2 Sessile drop and captive bubble techniques Measurements using the static sessile drop and captive bubble techniques were conducted to obtain contact angles on predetermined spots. The measurements were performed at least three times on each of the selected areas of the coal samples. With respect to the captive bubble technique, the contact angles became stable after around 20 seconds. The contact angles using the sessile drop decreased versus time due to the evaporation and penetration of water into the coal surface. In this study, a contact angle value at 25 seconds was used to assess the hydrophobicity of the coal surface for both sessile drop and captive bubble procedures. To assess operational error (the reproducibility of operator and instrument), contact angles were measured on glass using the captive bubble technique, since glass represents a very flat and homogeneous surface, and it provides a way to establish the reproducibility of the measurement. Table 4.3 shows that the reproducibility of the captive bubble technique is about ±0.5° with a standard deviation of ±0.28.      54   Table 4.3 The reproducibility of contact angle measurements using FTA1000 on glass.  Test 1st 2nd 3rd 4th 5th 6th Average Standard Deviation Contact angle (Degree) 44.97 45.80 45.60 45.40 45.60 45.51 45.48 ±0.28  Figures 4.6 and 4.7 illustrates an example of contact angles measured on predetermined areas versus time using the sessile drop and captive bubble techniques. The drop shape at point A was evaluated and the value is given next to the measurement line. The contact angles of low rank coal exhibit a rapid decrease versus time as compared to those for the high rank coal samples. The reduction rate is particularly noticeable for Danville 1 area (L1 and L2) due to penetration since the evaporation rate is assumed to be constant for all the measurements under stable conditions. When the captive bubble technique is used, the contact angle is not significantly influenced by the evaporation of surrounding water, and it is more likely to lead to the contact angle reaching an equilibrium value as shown in Figure 4.7. The predetermined areas L3 and L4 on Danville 2 produced similar contact angles which could be due to the fact that both areas were predominately composed of smooth vitrinite. Figures 4.6 and 4.7 presents a set of data for determined areas using both sessile drop and captive bubble techniques. The measurements were repeated three times to improve the accuracy of the results. The remaining data is included in Appendix D. 55    Figure 4.6 An example of individual contact angle versus time on predetermined areas (L1, L2, L3 and L4) using the sessile drop technique.  56    Figure 4.7 An example of individual contact angle versus time on predetermined areas (L1, L2, L3 and L4) using the captive bubble technique.  Values for the average contact angle measurements and related standard deviation are given in Table 4.4. The average contact angle values obtained with the sessile drop technique were 51.96°~94.44° with a standard deviation of 0.9°~6.7°. The average contact angle values obtained with the captive bubble technique were found to be 42.87°~80.72° with a standard deviation of 0.5°~4.7°. For the comparisons, the reproducibility of direct angle measurements with captive bubble on homogeneous glass is ±0.5°, as indicated in Section 4.2.2. High standard deviations were attained for contact angle measurements on the coal surface. This was expected, since the 57   coal is very heterogeneous, as shown by its complex petrographic composition in Table 4.2. Even through the measurements were repeated three times to improve the accuracy of the results, there could still be some test errors related to the procedure. Similar standard deviations have been reported by other researchers using these techniques (Ofori et al., 2010). Data from the three-time contact angle measurements are presented in Appendix E.  Table 4.4 Contact angles and standard deviations using sessile drop and captive bubble techniques.  No. Samples Sessile Drop (Degree) Standard Deviation Captive Bubble (Degree) Standard Deviation H1 Sample 3 87.82 ±3.4 74.96 ±2.2 H2 Sample 6 71.96 ±2.2 63.19 ±2.2 H3 Sample 7 94.44 ±6.7 80.72 ±3.1 H4 80.48 ±4.9 62.41 ±0.4 H5 83.68 ±1.8 69.25 ±1.4 H6 84.79 ±1.6 72.52 ±0.5 H7 Sample 9 88.21 ±3.7 67.54 ±1.0 H8 Sample 1 79.47 ±0.9 64.53 ±1.5 L1 Danville 1 57.56 ±2.3 44.80 ±1.2 L2 62.37 ±1.7 43.23 ±1.4 L3 Danville 2 71.67 ±1.0 59.74 ±2.7 L4 72.22 ±2.4 55.97 ±4.7 L5 Springfield 1 64.23 ±2.6 48.95 ±1.4 L6 69.70 ±1.4 53.83 ±3.0 L7 68.90 ±1.8 55.03 ±2.9 L8 Hymera 1 51.96 ±2.4 42.87 ±2.3 58    Figure 4.8 presents the measured contact angle values as derived from the sessile drop and captive bubble techniques as well as standard deviation. It is important to note that the sessile drop technique produced a higher contact angle values than did the captive bubble technique. Even on the same polished sample block, the average contact angle value is represented by a wide range of values with high standard deviations, as shown on Sample 7 in Figure 4.8. The difference in measured contact angle values could have arisen from (a) the local petrographic and chemical heterogeneity on the chosen spots; (b) the cracks; (c) the roughness and porosity of the coal surface; (d) the presence of invisibly small amounts of minerals, especially as observed in low rank coal. The visible difference between  the sessile drop and captive bubble contact angle values is due to the nature of the measurement, and this has been documented by Gutierrez-Rodriguez and Aplan (1984).   Figure 4.8 Average contact angles of different sample blocks using sessile drop and captive bubble techniques.   0.020.040.060.080.0100.0120.0Contact Angle (Degree)Polished  Sample Blocks Sessile Drop Captive bubble59   4.3 Micro-FTIR measurements Micro-FTIR spectra was conducted on the same areas where contact angles were measured. The average micro-FTIR spectra of all selected areas for high rank coal and low rank coal were obtained. The average micro-FTIR spectra of high rank coal was characterized by stronger aromatic CHx stretching vibration and aromatic CHx out-of-plane deformation signals. For the purpose of comparison, the chemical structure of pure vitrinite in both ranks of coal was investigated. The vitrinite in high rank coal has lower aliphatic and higher aromatic adsorptions, which is consistent with previous research (Chen et al., 2012).  4.3.1 Micro-FTIR spectra  Most of the micro-FTIR were performed on petrographic heterogeneous surfaces rather than on pure individual maceral groups. The spectras presented in Figure 4.9 are the average FTIR spectra of all 12 points on the selected area of the studied coal samples. L8, L6 and L2 represent low rank coal samples (Ro~0.6%). H7, H6, H4 and H2 represent high rank coal samples (Ro~1.6%). Typical spectrum in both types of coal contains several bands of absorption. These bands are assigned to OH groups (peak at ~3590 cm-1), CHar stretching at 3083-3002 cm-1 and CHal stretching at 2996-2803 cm-1. There are also bands of C=Car ring stretching with peaks at 1677-1521 cm-1, and C=O groups at 1832-1677 cm-1. At lower wavenumbers, bands due to aliphatic CH2 + CH3 deformation (peak at ~1445 cm-1) as well as CO-stretching vibration (peak at ~1190-1240 cm-1) and C-O-stretching (peak at ~990-1100 cm-1) were found. There is a broad band attributed to CHar out of plane deformation with a range of 904-700 cm-1 with main peaks at 870 cm-1, 812 cm-1 and 750 cm-1. The IR signals from chemical functional groups of interest are listed in Table 2.3. 60    Figure 4.9 Average micro-FTIR spectra on predetermined areas on the different samples. Functional groups: (A) aromatic CHx; (B) aliphatic CHx (C) oxygenated groups (D) C=C aromatic ring (E) aliphatic CHx out-of-plane deformation (F) aromatic CHx out-of-plane deformation.  The chemical variations between these two types of coals (low and high rank) display an evolutional path from high volatile bituminous to low volatile bituminous coals. The band representing the CHar stretching vibration (3083-3002 cm-1) is weakly marked in low rank coal, something that is frequently observed when micro-FTIR reflectance mode is used (Mastalerz and Bustin, 1996, Guo and Bustin, 1998, Stach and Murchison, 1982), while the high-rank coal is characterized by considerably higher values of CHar stretching. Also, the band of CHar out-of-plane deformation (904-700 cm-1) is more prominent in high rank coal. Low rank coal showed a relatively higher absorbance intensity of hydroxyl groups, CHal stretching and out-of-plane 61   deformation as well as oxygenated groups. Hydroxyl group absorbance is no longer noticeable in high-rank coal.  The CHar out - of - plane deformation region at 904-700 cm-1 provides important information regarding aromatic structures (Ibarra et al., 1996, Barnes et al., 1984). The range of 904-700 cm-1 is separated into three bands, aromatic structure with one isolated aromatic hydrogen atom at 870 cm-1, two or three adjacent aromatic hydrogen atoms at 812 cm-1, and four adjacent aromatic hydrogen atoms at 750 cm-1, respectively. The number of adjacent hydrogens per ring provides an estimate of the degree of aromatic substitution and condensation with increasing coalification. The strong 870 cm-1 and 815 cm-1 bands were more likely attributed to highly substituted aromatic rings than to large aromatic rings, which indicates increasing alkyl substitutions on aromatic rings. Figure 4.10 shows the evolution of aromatic hydrogen in the 904-700 cm-1 zone for the studied coals. In these samples, high rank coal displayed higher intensity at the 750 cm-1 band than 870 cm-1 and 815 cm-1 bands. In contrast, the relatively low intensity at the 750 cm-1 band in low rank coal should be attributed to alkyl substitutions on aromatic rings.  Figure 4.10 shows the distinct characteristics in FTIR spectra of pure vitrinite: (a) the aliphatic stretching region in low rank coal is stronger than that in high rank coal; (b) the aromatic stretching region is more intensive in high rank coal. The overall evolutionary trends of functional groups in vitrinite are similar to the average micro-FTIR spectra for low rank coal and high rank coal. Among those 192 spectra collected on different spots, some of these were collected from pure vitrinite in each coal rank. Most studies on the coal’s origins, history and chemical compositions of coal were 62   based on pure vitrinite across different coal ranks via micro-FTIR. In this study, both pure macerals and composite spots were analyzed simultaneously.   Figure 4.10 Micro-FTIR spectra of vitrinite from low rank coal (H2, H3) and high rank coal (L1, L8).  4.3.2 Semi-quantitative ratios The typical indices derived from micro-FTIR spectra were: (a) Aromaticity (AR), including AR1 and AR2; (b) chain length; (c) the degree of aromatic ring condensation (DOC), including DOC1 and DOC2; and (d) ‘A’ and ‘C’ factors. The index calculations are discussed in section 3.5. All the semi-quantitative ratios on predetermined areas are presented in Table 4.5.   As shown in Figure 4.11, the values of AR1 and DOC1 are almost zero because the band of aromatic CHar stretching vibration (3083-3002 cm-1) is weakly marked in the ratios of AR1 and DOC1. The significant characteristics among these ratios of high rank and low rank coal are that: (a) the AR2 and DOC2 is increasing from low rank coal to high rank coal, and (b) the chain length 63   (CH2/CH3) is not changing as coal rank increases. This is consistent with the research of Chen et al. (2015).   Figure 4.11 Graphs of semi-quantitative ratios on the predetermined areas for a) high rank coal and b) low rank coal.  The rising AR2 and DOC2 shows the higher aromaticity and degree of condensation of aromatic domains in high rank coal. The chain length ratios are highly scattered. The weakness of the CHal 64   stretching signal might cause the uncertainty in the calculated CH2/CH3 ratios for high-rank coal. The decreased ‘C’ factor in high rank coal suggests the decreasing oxygenated groups and this indicates higher maturation level of this coal. On the other hand, it is known that the ‘A’ factor reaches maximum value for coals with vitrinite reflectance of Ro~1.5 % (Chen et al., 2012). In Figure 4.11, the ‘A’ factor is not distinctly different between two studied coals (Ro~0.6% and Ro~1.6%) and this could be because these two samples are located on opposite sides of the maximum point.  Both ‘A’ and ‘C’ factors are not considered to be significant for the purpose of this study and will not be further discussed.  The ratio of CHal versus C=O was introduced in this thesis to assess the abundance of aliphatic groups over oxygenated groups as shown in Figure 4.12. Compared to low rank coal, the ratio is considerably higher for high rank coal, except for the L8 spot in low rank coal. The highest ratio is due to the lowest intensity of C=O stretching region in this area and the relatively high levels of aliphatic groups. This particular spot L8 is represented by large liptinite content, which is highly aliphatic. This provides evidence on how local composition affects the surface chemistry of predetermined areas.    65    Figure 4.12 Value of aliphatic CHx versus oxygenated groups for both low rank and high rank coals.  051015202530354045L1 L2 L3 L4 L5 L6 L7 L8 H1 H2 H3 H4 H5 H6 H7 H8Semi-quantitative ratiosPredetermined AreasAliphatic CHx stretching / Oxygenated group66    Table 4.5 Semi-quantitative ratios on the predetermined areas for all polished sample blocks (the average areas of band intensities using micro-FTIR spectroscopy on predetermined areas is attached in Appendix F). No. Aromaticity 1 Aromaticity 2 Aliphatic/C=O C=O/C=C CH2/CH3 DOC1 DOC2 ‘A’ factor ‘C’ factor  A/B G/B B/E E/F D/C A/F G/F B/(B+F) E/(E+F) L1 0.001 0.267 13.782 0.069 1.485 0.001 0.255 0.488 0.065 L2 0.001 0.244 11.380 0.092 1.604 0.001 0.256 0.512 0.084 L3 0.021 0.384 2.210 0.279 1.227 0.013 0.237 0.382 0.218 L4 0.022 0.375 2.180 0.266 1.111 0.013 0.217 0.367 0.210 L5 0.010 0.292 2.586 0.283 1.623 0.007 0.214 0.423 0.221 L6 0.005 0.307 2.498 0.295 1.362 0.004 0.227 0.424 0.228 L7 0.010 0.309 2.423 0.292 1.339 0.007 0.219 0.415 0.226 L8 0.000 0.294 38.147 0.026 1.578 0.000 0.290 0.497 0.025 H1 0.090 0.642 11.347 0.051 1.683 0.052 0.373 0.367 0.049 H2 0.091 0.449 27.170 0.026 1.495 0.063 0.313 0.410 0.025 H3 0.158 0.917 5.732 0.114 1.252 0.103 0.600 0.396 0.103 H4 0.138 0.876 11.040 0.076 1.350 0.115 0.732 0.455 0.070 H5 0.130 0.608 16.472 0.050 1.340 0.107 0.499 0.451 0.047 H6 0.189 0.812 5.264 0.136 1.053 0.136 0.583 0.418 0.120 H7 0.120 0.562 25.064 0.042 1.448 0.125 0.586 0.511 0.040 H8 0.171 0.785 9.105 0.064 1.115 0.100 0.460 0.370 0.061 67   4.3.3 Micro-FTIR mapping Micro-FTIR mapping is a novel tool in organic petrography and it has already been explored to characterize the abundance of functional groups in coal macerals. This section provides an introduction on how to (a) study chemical variations in functional group abundance in different macerals using micro-FTIR mapping; (b) analyze visibly homogenous vitrinite; and (c) further investigate the potential to utilize micro-FTIR mapping in order to correlate chemical composition derived from these measurements with the hydrophobicity of coal surface, as measured by contact angle.  Figure 4.13 provides an example of the micro-FTIR mapping technique. The selected area was observed through the objective of 10× magnification, as seen micro-FTIR spectra was obtained at a resolution of 4in Figure 4.13 (a). All of the sampling points were evenly distributed with a point-to-point distance of 20μm. Figure 4.13 (b) shows the intensity distribution of the CHal stretching region at 3000-2800 cm-1. Figure 4.13 (c) provides the corresponding 3D-image of absorbance, which can provide a display of the intensity distribution of all kinds of function groups. Similarly, the chemical mapping shows that red peaks that represent high intensities of the CHal stretching group and the blue valleys indicate a low content of aliphaticity. 68    Figure 4.13 The results of micro-FTIR mapping on Danville 2. (a) Micro-FTIR microscopic image observed through 10× objective; (b) chemical mapping of aliphatic CHx (3000-2800 cm-1) in the field of study; (c) corresponding 3D-image of absorbance; (d) screen shot of the results of micro-FTIR mapping on Danville 2 using the software Stream.  The chemical mapping of the CHal stretching region, the oxygenated groups at 1521-1677 cm-1, CHar out-of-plane deformation at 904-700 cm-1, and the ratio of CHal stretching region/ CHar out-of-plane deformation were chosen to represent abundances of important functional groups for evaluating and discussing the chemical properties of polished coal blocks. As seen in Figure 4.14, it becomes clear that the microscopically pure vitrinite is chemically heterogeneous at the intensity of all aliphatic and aromatic stretching regions, which is in agreement with the results of previous 69   research, as discussed in the literature review. Figures 4.15 (a) and (b) represent vitrinite associated with liptinite and the chemical map of CHal stretching group of the same area, respectively. The signal intensities of CHal stretching at 3000-2800 cm-1 are higher in the area of liptinite than vitrinite, indicating that liptinite is more aliphatic than vitrinite.    Figure 4.14 The corresponding chemical map superimposed on the microscopic image in the field of study on Danville 2 of (a) aliphatic CHx stretching region (b) oxygenated groups (c) aromatic CHx out-of-plane deformation (d) ratio of aliphatic CHx stretching region/aromatic CHx out-of-plane deformation.      70    Figure 4.15 Micro-FTIR mapping of heterogeneous coal surface on Danville 1. (a) Micro-FTIR microscopic image; (b) the corresponding chemical map of aliphatic CHx stretching region in the field of study.  Micro-FTIR mapping could be used to:  Investigate the distribution of functional groups on various macerals and provide information regarding varied functional groups on the integrated areas.   Study the chemical heterogeneity of coal surface, where different macerals are associated with each other.  Correlate the distribution of chemical groups with the hydrophobicity of the coal surface assessed by contact angle measurements.  There was found to be a scale problem that resulted in the software not being able to perform the chemical groups mapping on a large enough area where the contact angle was measured. As a result, it was not possible to directly use micro-FTIR mapping in order to find correlation between chemical maps and hydrophobicity on the studied samples. Some possible ways to resolve this would be to: 71    Stitch small scale chemical maps together to make a big chemical map for 4×4 mm areas.  Develop a new in situ technique to assess the surface hydrophobicity rather than using contact angle measurements. Micro-FTIR mapping should be further investigated with respect to studying the heterogeneity of coal surface.  72   Chapter 5: Discussions  In this study, the chemical composition of coal surface as derived from micro-FTIR analysis in combination with petrographic composition was investigated in correlation with contact angle measurements on the analyzed areas. As shown in Figure 5.1, chemical composition and petrographic composition were assessed using micro-FTIR and image analysis, respectively. The correlations between contact angle, and semi-quantitative ratios of aromatic and aliphatic hydrocarbons as well as functional groups were obtained.   Figure 5.1 Illustration of the major structure of this thesis and the corresponding approaches and techniques used.  Chemical composition extracted from semi-quantitative micro-FTIR analysis was correlated with contact angle measurements. The following ratios were discussed as they relate to contact angles: Aromaticity 2, DOC 2, CH2/CH3 and CHal/C=O. The examined coal samples representing low and high rank coals exhibited opposite trends between the semi-quantitative ratios and contact angle values. In lower-rank coal rising Aromaticity 2 led to an increase in contact angle, whereas the contact angle decreased when the ratios of CHal/C=O and CH2/CH3decreased. In high rank coal, the contact angle increased when Aromaticity 1 and 2 decreased, the contact angle increased when 73   aliphatic chain length and CHal/C=O ratio increased. These trends were found to be the same for both sessile drop and captive bubble techniques (Figure 5.2 a,b,c,d). The detailed semi-quantitative ratios versus contact angle are discussed in the following sections. In all the figures of this chapter, the orange dots represent the high rank coal and the deep blue dots represent the low rank coal.  5.1 Aromaticity As shown in Figure 5.2 (a) and (c). The linear relationships between Aromaticity 1 (CHar stretching out of plane deformation at 3082-3002 cm-1, over CHal stretching at 2996-2803 cm-1) and contact angles as derived from the sessile drop and captive bubble techniques are less pronounced for low rank coal. This is likely due to the weakness of the CHar stretching signal at 3083-3002 cm-1. The lower rank coal is usually less aromatic by nature, which could have the effect on signal strength at the aromatic stretching region. As a result, Aromaticity 2 (aromatic C-H out-of-plane region at 904-700 cm-1 versus CHal stretching region) was chosen to evaluate aromaticity in this study.  74    Figure 5.2 Relationship between the ratio of aromatic groups to the aliphatic group and respective contact angles using sessile drop (a)aromaticity 1: aromatic CHx stretching at 3082-3002 cm-1 versus aliphatic CHx stretching; (b)aromaticity 2: aromatic CHx out of plane deformation at 904-700 cm-1 versus aliphatic CHx stretching and captive bubble (c)aromaticity 1; (d)aromaticity 2.   In low rank coal, the correlation between Aromaticity 2 and contact angle indicates that increasing aromaticity leads to higher contact angle values. In higher rank coal as the aromaticity decreases, the contact angle increases.  Klassen (1966) suggested that the decreasing contact angle for coals past the medium-volatile bituminous rank is caused by the increase in aromatic groups. As an analogy with respect to anthracite, the aromatic rings in anthracite coal can interact with polar water molecules through the π-electrons, thus increasing the total work of adhesion and resulting in decreasing contact angles. The coal used in this study is of high rank with a reflectance R0 1.45~1.65, hence, it could be considered as high rank coal (medium to low volatile bituminous). 75   In the low volatile bituminous rank, it is possible that the decrease in hydrophobicity of this coal is due to the increase in aromaticity.  As observed in Figure 5.2 (b) and (d), a difference of 20 degrees in contact angle was noticed within the iso-rank, which led to the investigation of the extreme points, H3, H4, L3 and L4, using image analysis and SEM. From the micro-FTIR results of the high rank coal, it was found that H4 has a higher intensity of aromaticity than does H3, which is consistent with the image analysis results showing that the H4 spot has more inertinite maceral in its composition (12.25%) than does H3 (0.62%). As discussed in Chapter 2, generally, inertinite is believed to be the most aromatic as compared to the other macerals (liptinite and vitrinite). The higher content of inertinite on H4 results in a higher Aromaticity 2 value and lower contact angle when compared to H3. One possible reason of the lower contact angle on H4 spot is the increased aromaticity caused by high inertinite content. As discussed previously in this Chapter 2, the aromatic structure of high rank coal decreases the contact angle. Another reason could be related to the fact that inertinite macerals especially fusinite and semifusinite carry minute minerals in their cavities on the surface. Cavities are part of the morphology of these macerals. In Figure 5.3 representing H3 and H4, it is visible that the cavity of fusinite is filled with minerals smaller than 10 μm in size on H3, while the H4 spot is represented by semifusinite with minerals in its cavities.   76    Figure 5.3 Scanning electron microscopy images of fusinite macerals on (a) H3 and semifusinite macerals on (b) H4.  In low rank coal, the L3 and L4 spots have similar petrographic compositions and the highest Aromaticity 2 values. These two spots are made up of almost 90% pure vitrinite, with negligible content of minerals. Figure 5.4 shows that the microscopically pure vitrinite on L3 has no significant minerals present, as observed under the optical microscope and confirmed by SEM. The micro-FTIR mapping of vitrinite on L3 indicatesa strong intensity of CHar stretching region and the lowest aliphaticity (CHal/CHar out of stretching region), which is consistent with semi-quantitative micro-FTIR results. The vitrinite in low rank coal analyzed here using micro-FTIR mapping is found to be highly aromatic, with relatively low aliphaticity (Figure 5.5).  Figure 5.4 Photomicrographs of vitrinite maceral on L3 and corresponding scanning electron microscopy images of vitrinite maceral on L3 77     Figure 5.5 Micro- FTIR mapping of pure vitrinite. (a) Micro-FTIR microscopic image and corresponding chemical mapping of ratio of CHal stretching groups (2803-2996 cm-1) versus CHar stretching groups (700-904 cm-1); (b)micro-FTIR microscopic image and corresponding chemical mapping of CHar stretching groups (700-904 cm-1).  5.2 Degree of condensation The degree of condensation of aromatic hydrocarbons is represented by DOC 1and DOC2. The trend between DOC 1 and DOC2 and contact angle is very similar to that ascribed for Aromaticity 2 (Figure 5.6). In lower rank coal, the correlation between DOC 1 and contact angle is not significant, which is similar to previously discussed Aromaticity trends. This is due to the enhanced intensity of the C=C aromatic ring at 1600 cm-1 and by highly conjugated hydrogen-bonded C=O functional groups. The amounts of COO- groups near 1580 cm-1 caused by the enhanced intensity of C=C aromatic ring at 1600 cm-1 and by highly conjugated hydrogen-bonded C=O functional groups and amounts of COO- groups near 1580 cm-1 could also have an effect on this correlation.  78    Figure 5.6 Relation between degree of condensation and respective contact angles using sessile drop (a) DOC 1: aromatic CHx stretching versus C=C stretching at 1677-1521 cm-1 (b) DOC 2: aromatic CHx out of plane deformation versus C=C stretching.  5.3 CH2/CH3 Figure 5.7 illustrates different effect of aliphatic chain length (CH2/CH3) of high and low rank coals. In lower-rank coal samples, the relationship between CH2/CH3 and contact angle forms descending line, while for higher rank coal, it forms an ascending one. This correlation is somewhat scattered. According to Chen et al. (2012), the CH2/CH3 ratio steadily decreases from peat to medium volatile bituminous coal and the length of aliphatic chains in high-rank coals (Ro> 1.5%) becomes difficult to measure. In this study, both type of samples; low rank coal with reflectance Ro~0.6% and high rank coal with reflectance Ro~1.6%, exhibit similar CH2/CH3 ratio ranges except that they show opposite trends.  79      Figure 5.7 Relationship between the ratio of CH2 to CH3 and respective contact angle using (a) sessile drop technique and (b) captive bubble technique.  5.4 Aliphatic CHx/Oxygenated groups The amount of oxygenated groups present (Oxygen functional groups) is one of the major factors that affect the wettability of a coal surface. Klassen (1996) suggested that the low contact angles in low rank coal are caused by high oxygen functional groups. This also explains the results that the high rank coal (70°~80°) has higher contact angle values than does low rank coal (40°~50°). Hydrogen bonding, dipole-dipole, and even electrostatic interactions between water molecules and oxygen functional groups on the coal surface would increase the overall work of adhesion of water to coal. In high rank coal, the increased content of oxygenated groups make the coal surface more hydrophilic and thus decrease the contact angle as the ratio of CHal/C=O is being reduced.  The ratios of CHal/C=O at 1832-1677 cm-1 were introduced in this work to demonstrate the relative contents of aliphatic and oxygenated groups, and to assess their effect on contact angle values, as shown in Figure 5.8. In high rank coal samples, the CHal/C=O versus contact angle conforms to a 80   trend indicating an increase in contact angle values as the ratio of CHal/C=O is increased. This is similar to the correlation between contact angle and the length of aliphatic chain. For the lower rank coal samples, the maximum value of the CHal/C=O ratio was observed on L8 in Figure 5.8. The L8 spot has the highest intensity of aliphatic groups and the lowest contents of oxygenated groups. This is caused by the high content of liptinite maceral (14.47%). In addition, highly dispersed minerals were observed under SEM on L8 as shown in Figure 5.9 (a) and (b). Therefore, the L8 spot was considered to be an outlier when correlating the CHal/C=O ratio with contact angle for the low rank coal.    Figure 5.8 Relationship between the ratio of CHal stretching to C=O groups and respective contact angle using (a) sessile drop technique and (b) captive bubble technique.   81    Figure 5.9 Scanning electron microscopy images taken on L8 with observed minerals (a) and corresponding energy-dispersive X- ray spectroscopy on spot b of L8  Generally, low and high rank coal samples have distinct trends between semi-quantitative ratios and contact angle, reflecting the effects of functional groups on surface hydrophobicity. The correlation between micro-FTIR analysis using different ratios and contact angle was observed to have the following characteristics:   In low rank coal, the contact angle increased with the increase of Aromaticity 1 and Aromaticity 2, whereas aliphatic groups seemed to have little effect on contact angle values.  Increase in the magnitude ratios of CHal /C=O and CH2/CH3 in high rank coal samples enhanced surface hydrophobicity which can be seen to be reflected by the increasing contact angle values.  Increased aromaticity in high rank coal samples may have decreased the surface hydrophobicity of coal. This is supported by the trends for both Aromaticity 1 and Aromaticity 2.   82   While the main objective of this study was to develop an understanding of the chemical composition of coal surface through the use of the newly developed micro-FTIR technique, the major achievement of this study has been in adopting the micro-FTIR technique to analyze coal surface in situ. This is the first time that the surface chemistry of coal has been studied on such a small scale. This was achieved through comprehensive analysis that combined micro-FTIR, petrographic image analysis and SEM to gain a better understanding of coal surface composition with its complex heterogeneity. This is considered to be significant leap towards the understanding how the heterogeneity of coal affects its hydrophobicity. 83   Chapter 6: Conclusion  A new methodology was introduced in this study to correlate the chemical composition of the coal surface as derived from micro-FTIR spectroscopy, with corresponding contact angle. This is the first study to obtain direct chemical information on the coal surface (in situ) that has been used for contact angle measurements.   Until now, micro-FTIR has been used in petrographic studies for assessing the chemistry of macerals. This has typically involved the chemical characterization of very small areas (micron in size) corresponding to the sizes of macerals. In this study, the micro-FTIR technique is adapted to provide information on the scale that is suitable for contact angle measurements. As a result, a new approach was needed for building the correlation between chemical information that is usually collected at the micron scale (micro-FTIR) and contact angle measurements at the millimeter scale.   The key point in developing such a methodology was to adapt the micro-FTIR point analysis to collect reliable information that should uniformly cover the whole area needed for contact angle measurement. A total of 12 analysis points on each area were used in this approach. There were 192 analysis points and FTIR spectra collected for both high rank and low rank coal samples.   The semi-quantitative ratios for all samples were calculated using micro-FTIR spectra to assess the chemical composition of the coal surface that was used for contact angle measurements. The trends obtained from this study were in general agreement with accepted theories regarding the 84   chemical composition of low and high rank coals. For the samples that were studied here, the following can be concluded:  High rank coal exhibit higher aromaticity and lower aliphaticity than does the low rank coal.  Increase in Aromaticity 1 and 2 led to increase of contact angles in low rank coal samples, while the type and quantity of aliphatic groups seem to have had little effect on contact angle values.   For the high rank coal samples, an increase in the aliphatic groups increased contact angle values, while increase in Aromaticity 1 and Aromaticity 2 led to smaller contact angle values.  The newly introduced CHal/C=O ratio was used to provide additional information on its effect on contact angle. The increased content of oxygenated groups in high rank coal samples led to decreases in contact angles. This is consistent with the results of previous studies (Pawlik, 2008, Gutierrez-Rodriguez and Aplan, 1984). For the low rank coal samples, the correlation was less distinct, but an opposite trend was observed.   As a part of the new methodology for studying the correlation between the chemical composition of the coal surface derived from micro-FTIR spectroscopy and the contact angle, image analysis was also applied to characterize and analyze the petrographic composition of the areas that were subjected to these measurements. This provided insights on how the petrographic composition and physical appearance of each area contributed to the final results.  Image analysis was able to provide additional information regarding otherwise unresolved trends. Image analysis in connection with SEM were able to reveal details related to the coal surface by being able to point to the small quantities of minerals within the analyzed areas.  85    Combination of all these techniques formulates, as it has been described in this thesis a new approach. Since, this is the first attempt to use micro-FTIR to provide chemical information on a scale that could be utilized for contact angle measurements, there were many shortcomings that were noted during the course of this research and possible improvements are outlined  in the next chapter.  86   Chapter 7: Recommendations  Further developments towards a better understanding the hydrophobicity of coal surface could include introducing a more automatic instrument to measure contact angle, testing a greater variety of coals of different ranks, and further improving the micro-FTIR mapping technique to obtain a quantitative distribution of chemical groups on larger areas that are applicable for contact angle measurements.  In situ contact angle measurements using an FTA 1000 shape analyzer (First Ten Angstroms, Inc.) remains problematic due to issues such as evaporation of a drop, distortion of the bubble/drop, needle dimension, and operational errors. The development of a fully automatic expert system is recommended in order to increase the precision and accuracy of contact angle measurements. This instrument would need to be able to control temperature, humidity, and be able to place a measurably small drop of liquid to wet a microscopically small surface. The Drop Shape Analyzer DSA100 (KRÜSS GmbHu) could offer such possibility as measuring technique.   Alternative techniques to assess the hydrophobicity of coal surface could also be further investigated and compared to classical contact angle measurements. IGC (inverse gas chromatography) could provide one such method to determine the surface heterogeneity of coal surface, as it has already been used to assess the surface heterogeneity of minerals for flotation (Ali et al., 2013, Wang et al., 2013).  87   Further improvement should be to increase the number of analysis points to render the average micro-FTIR spectra more representative. 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Properties of Coal and Impurities in Relation to Preparation. Coal Preparation, AIME, New York, 1-35.  94   Appendices Appendix A  Micro-FTIR spectroscopy operation Procedure of micro-FTIR spectroscopy: (a) Run background in Setup menu by putting 500 as No. of scans, collect background and save (b) Insert sample into the sample compartment and navigate the predetermined area  (c) Take the microscopic image observed through 10× objective  (d) Collect FTIR spectrum of coal samples using the previous back ground using 10× objective  (e) Correct the spectrum with Kramers-Krönig, Automatic Baseline and Smooth (f) Save the file and analyze the data.   Procedure of micro-FTIR mapping:  (a) Run background as previous procedure and same setup (b) Collect background and save (c) Set the aperture dimensions of 60μm ×60μm and step size of 100μm, and the mapping area is fixed.  (d) Run the FTIR mapping program (e) Save and analyze data (f) Export data of all kinds functional groups intensiy distribution or 3-D image.    95    Appendix B  SEM operation Procedure of SEM on the coal sample as follows:  (a) Coat the sample surface with carbon and mount the samples on pin mounts using adhesive conductive carbon discs (b) Set the “EVAC” switch to the air position (green light off) and wait approximately one minute for the chamber pressure to equalize with the atmosphere (c) Place the prepared sample in the sample stage and hold the chamber door shut (d) Set the “EVAC” switch to the evacuate position and wait approximately 2 minutes for the chamber to evacuate (e) Select appropriate accelerating voltage and enter the value of 15.0 kV in the Vacc field (f) Click the “HV” button to the left of the beam condition and select the SE detector (g) Navigate the predetermined area using stage control and bring the surface into focus (h) Select appropriate aperture, condenser llens/beam current and perform aperture alignment (i) Take image of the selected area on sample surface using “HR” button and transfer images to Quart Xone by “PCI”, or select the spot analysis using Quart Xone for elemental compositional analysis (j) Save image or spectra  on the Quartz Xone computer (k) Change the sample by turning off the high voltage, bringing the stage to the home position, extracting EDX detector, and set the “EVAC” switch to the air position (l) Wait approximately one minute for chamber pressure to equalize with the atmosphere and them remove the sample of change another one  96   Appendix C  SEM results      97        98         99           100   Appendix D  Petrographic analysis results  Image analysis information of each photo image under the microscope. No. Area  Cracks/Holes (%) Liptinite (%) Vitrinite (%) Inertinite (%) Minerals (%) H1-1 63106.83 0.95 23.76 14.49 57.91 0.00 518306.41 0.23 7.41 88.39 3.18 0.00 H1-2 54574.99 1.67 31.29 24.88 40.61 0.01 524630.41 0.19 8.86 88.61 1.66 0.00 H1-3 61010.9 0.94 29.68 19.14 48.22 0.00 518079.26 0.28 10.71 85.15 3.77 0.00 H1-4 34981.87 0.46 29.97 0.70 64.42 0.00 H1-5 579390.6 0.21 11.23 84.15 3.69 0.00 H1-6 545380.49 0.22 8.74 85.91 4.39 0.00 H1-7 59080.54 0.23 35.19 18.48 43.46 0.00 H1-8 579390.6 0.17 14.20 81.92 3.09 0.00 H1-9 579390.6 0.40 12.33 83.04 3.50 0.00 H1-10 520742.65 3.37 11.84 81.18 3.01 0.00 H1-11 520742.65 3.37 11.84 81.18 3.01 0.00 H1-12 556731.31 1.15 24.67 67.47 6.07 0.00  No. Area  Cracks/Holes (%) Liptinite (%) Vitrinite (%) Inertinite (%) Minerals (%) H2-1 579391 0.16 9.17 90.16 0 0 H2-2 579391 0.83 10.52 88.11 0 0 H2-3 90684 0.41 21.54 27.47 48.66 0 455742 1.43 11.86 86.14 0 0 H2-4 579391 0.34 11.42 87.71 0.01 0 H2-5 579391 0.14 6.91 92.5 0.01 0 H2-6 579391 3.3 18.1 77.28 0.6 0 H2-7 222759 0.51 8.45 86.79 2.14 0 356188 0.39 4.99 91.99 1.2 0 H2-8 579391 0.63 5.54 93.38 0 0 H2-9 579391 0.07 6.82 92.33 0.26 0 H2-10 579391 1.19 11.65 86.54 0.02 0 101   No. Area  Cracks/Holes (%) Liptinite (%) Vitrinite (%) Inertinite (%) Minerals (%) H2-11 579391 0.2 6.77 92.52 0 0 H2-12 579391 0.12 7.66 90.99 0.71 0  No. Area  Cracks/Holes (%) Liptinite (%) Vitrinite (%) Inertinite (%) Minerals (%) H3-1 13717 0.03 16.73 4.13 75.49 0 565028 0.27 14.03 84.57 0.6 0 H3-2 579391 0.08 16.36 82.6 0.53 0 H3-3 579105 0.29 19.66 75.98 0.93 0 H3-4 579391 0.05 18.79 80.45 0.03 0 H3-5 579391 0.91 25.06 73.88 0.07 0 H3-6 579391 0.18 10.33 88.79 0.13 0 H3-7 579391 0.44 15.07 83.54 0.1 0 H3-8 33348 2.55 33.91 62.57 0 0 543825 0.57 17.48 75.83 3.48 0 H3-9 579391 0.31 6.42 92.82 0.01 0 H3-10 579105 1.03 16.42 81.04 0 0 H3-11 579391 1.09 12.5 85.85 0.02 0 H3-12 579391 0.4 7.02 92.26 0 0  No. Area  Cracks/Holes (%) Liptinite (%) Vitrinite (%) Inertinite (%) Minerals (%) H4-1 93020 1.73 9.39 22.9 65.39 0 486251 0.44 3.99 94.31 0.98 0 H4-2 579391 0.77 10.68 84.91 3.24 0 H4-3 438555 3.44 12.94 49.33 33.44 0 139694 0.81 3.97 94.63 0.37 0 H4-4 36270 2.3 9.9 29.06 58.04 0 541605 0.15 2.75 95.16 1.83 0 H4-5 108850 0.79 5.74 78.68 14.33 0 468499 0.25 2.91 94.12 2.41 0 H4-6 579391 0.35 5 92.92 1.41 0 102   No. Area  Cracks/Holes (%) Liptinite (%) Vitrinite (%) Inertinite (%) Minerals (%) H4-7 241371 0.4 6.29 48.73 42.79 0 337661 0.36 7.95 85.58 3.48 0 H4-8 579391 0.75 7.73 87.7 3.41 0 H4-9 290669 7.27 6.37 85.68 0 0 285965 0.51 2.33 92.46 2.46 0 H4-10 370368 2.81 14.06 48.9 33.66 0 208228 0.48 7.74 87.88 3.12 0 H4-11 288529 3.74 16.85 34.88 43.8 0 290697 0.42 4.91 93.47 0.79 0 H4-12 348873 1.83 11.83 42.49 43.24 0 230019 0.36 5.79 93.48 0.29 0  No. Area  Cracks/Holes (%) Liptinite (%) Vitrinite (%) Inertinite (%) Minerals (%) H5-1 26562 1.47 14.16 6.42 75.58 0 551749 0.38 5.03 89.92 4.19 0 H5-2 579391 0.34 8.56 88.65 1.86 0 H5-3 579391 0.42 6.96 0 5.37 0 H5-4 579391 0.29 5.44 89.7 4.17 0 H5-5 579105 0.41 6.38 84.57 5.54 0 H5-6 579391 0.53 6.66 86.41 5.91 0 H5-7 507733 0.65 5.85 89.06 3.94 0 H5-8 579391 0.8 7.43 90.07 1.23 0 H5-9 579391 0.4 6.74 91.3 1.23 0 H5-10 280334 6.32 37.82 18.49 36.19 0 269064 0.77 5.07 90.91 2.93 0 H5-11 102391 0.18 8.48 42.99 47.18 0 412543 0.53 5.12 91.88 1.29 0 H5-12 515059 0.37 8.45 88.16 2.61 0   103   No. Area  Cracks/Holes (%) Liptinite (%) Vitrinite (%) Inertinite (%) Minerals (%) H6-1 579105 0.51 5.72 83.81 6.88 0 H6-2 579391 0.1 6.89 90.1 2.35 0 H6-3 221411 4.94 23.55 27.11 39.99 0 356946 1.17 10.99 79.07 5.76  H6-4 125014 1.03 17.77 25.79 54.36 0 H6-5 29575 1.39 18.19 33.73 45.56 0 549139 0.33 5.19 91.35 2.83 0 H6-6 75894 0.96 18.34 23.75 56.1 0.29 492288 0.2 4.73 91.15 3.46 0 H6-7 579391 0.97 10.11 85.55 2.89 0 H6-8 579391 0.96 13.83 82.99 1.65 0 H6-9 30301 0.3 14.89 20.42 62.63 0 H6-10 579391 0.01 4.18 84.41 10.65 0 H6-11 579391 0.24 7.25 88.65 3.44 0 H6-12 579391 0.31 9.55 87.71 1.95 0  No. Area  Cracks/Holes (%) Liptinite (%) Vitrinite (%) Inertinite (%) Minerals (%) H7-1 579391 1.71 24.56 61.92 10.67 0 H7-2 579391 1.41 19.81 65.31 12.48 0 H7-3 579391 0.72 21.81 62.28 14.32 0 H7-4 579391 0.85 20.31 62.08 15.74 0 H7-5 579391 0.85 19.72 68.38 10.05 0 H7-6 579391 1.17 16.2 76.73 4.88 0 H7-7 579391 0.69 13.68 81.25 3.47 0 H7-8 579391 0.8 18.36 68.92 10.76 0 H7-9 579105 1.78 13.87 72.05 9.45 0 H7-10 579391 2.06 19.78 69.35 7.71 0 H7-11 579391 2.07 20.8 69.72 6.18 0 H7-12 579391 0.88 18.85 68.61 10.38 0  104   No. Area  Cracks/Holes (%) Liptinite (%) Vitrinite (%) Inertinite (%) Minerals (%) H8-1 579391  0.46 12.75 85.27 0.8 0 H8-2 579391  0.55 14.41 82.61 1.63 0 H8-3 579391  0.5 14.67 80.63 3.45 0 H8-4 579391  1 13.9 82.99 1.55 0 H8-5 579391  1.06 17.44 79.13 1.63 0 H8-6 227564  1.12 15.9 14.69 65.98 0 351452  1.73 16.87 80.37 0.18 0 H8-7 579391  1.09 18.33 78.76 1.01 0 H8-8 579391  0.83 19.42 78.24 0.72 0 H8-9 579391  0.9 17.83 73.69 6.66 0 H8-10 579391  0.78 16.43 74.45 7.27 0 H8-11 579391  0.98 18.83 67.6 11.44 0 H8-12 579391  0.59 15.57 66.16 16.64 0  No. Area  Cracks/Holes (%) Liptinite (%) Vitrinite (%) Inertinite (%) Minerals (%) L1-1 162581  6.12 29.25 58.91 0.07 0 175602  2.13 6.38 87.06 0.42 0.07 239843  4.18 21.07 64.71 0 1.16 L1-2 78368  7.48 38.42 52.82 0 0.07 498911  3.11 9.37 81.6 0 0.04 L1-3 579391  3.95 4.64 91 0.38 0.03 L1-4 579391  0.93 0 99.03 0 0 L1-5 579391  0.55 0 99.23 0 0 L1-6 579391  1.46 0 97.93 0 0.06 L1-7 579391  1.88 0 97.53 0 0.13 L1-8 579391  2.42 0 96.7 0 0.35 L1-9 579391  2.62 0 97.26 0 0 L1-10 579391  1.77 0 98.21 0 0 L1-11 579391  1.37 0 97.82 0 0.02 L1-12 579391  1.93 0 96.84 0 0  105   No. Area  Cracks/Holes (%) Liptinite (%) Vitrinite (%) Inertinite (%) Minerals (%) L2-1 579390.6 7.07 28.31 62.6 0.8 0.01 L2-2 570328.6 4.51 24.65 68.63 1.07 0.02 L2-3 579390.6 1.8 0 97.35 0 0.07 L2-4 579390.6 2.9 0 92.86 0 0 L2-5 579390.6 0.56 3.86 93.97 0 0.28 L2-6 579390.6 0.64 4.76 93.03 0 0.21 L2-7 579390.6 0.98 2.14 94.51 0 0.08 L2-8 579390.6 2.31 0 96.29 0 0 L2-9 579390.6 1.62 0 97.26 0 0 L2-10 579390.6 0.77 0 98.21 0 0 L2-11 579390.6 1.18 0 97.82 0 0.08 L2-12 579390.6 0.93 0 97.04 0 0.1  No. Area  Cracks/Holes (%) Liptinite (%) Vitrinite (%) Inertinite (%) Minerals (%) L3-1 579390.6 0.4 0 99 0.06 0 L3-2 26753.7 21.04 30.56 3.23 38.15 0 550050.4 2.23 20.79 75.28 0.65 0 L3-3 106453.3 0.85 99 0 0 0 457927.5 2.03 23.19 73.38 0.12 0.01 L3-4 566353.6 0.68 25.17 73.12 0.2 0.01 L3-5 579390.6 0.09 2.36 97.03 0.02  L3-6 579390.6 1.83 9.29 88.15 0.06 0.01 L3-7 505727.5 1.3 8.9 88.71 0.26 0.01 L3-8 488947.7 1.39 9.49 73.51 0 0.01 L3-9 304842.3 3.13 26.21 69.78 0.07 0 218688.5 0.39 6.04 81.75 0.65 0 L3-10 526693.1 0 23.92 74.77 0.13 0.02 L3-11 237062.7 1.8 7.47 90.11 0 0.01 275506.3 9.13 27.95 61.23 0.3 0 L3-12 579390.6 0 3.16 71.71 0.03 0  106   No. Area  Cracks/Holes (%) Liptinite (%) Vitrinite (%) Inertinite (%) Minerals (%) L4-1 552763.2 2.29 15.04 81.46 0.12 0 L4-2 536441.7 2.45 21.57 73.94 0.73 0.09 L4-3 579390.6 2.65 20.51 75.32 0.29 0 L4-4 579390.6 6.78 18.9 69.29 4.03 0 L4-5 579390.6 527846.28 0.58 10.31 87.96 0.29 L4-6 520915.3 3.3 17.75 77.49 0.03 0 L4-7 546821.6 2.15 16.07 80.78 0 0.01 L4-8 252276.3 12.35 46.08 40.05 0.07 0 L4-9 579390.6 1.35 16.11 80.97 0.42 0.01 L4-10 326126.5 1.34 2.55 93.25 0 0 L4-11 528907.1 2.59 16.21 80.03 0.12 0.02 L4-12 579390.6 3.55 23.58 71.76 0.05 0  No. Area  Cracks/Holes (%) Liptinite (%) Vitrinite (%) Inertinite (%) Minerals (%) L5-1 509727.5 2.67 15.45 77.04 3.7 0 L5-2 573193 6.12 20.88 65.94 5.6 0.02 L5-3 564186.4 4.94 19.88 68.94 4.56 0 L5-4 579390.6 3.04 16.49 76.32 2.79 0 L5-5 561085.0 5.59 20.66 68.85 3.42 0.02 L5-6 538722.8 6.1 11.52 77.33 3.57 0.01 L5-7 545108.8 2.92 13.27 80.19 2.43 0 L5-8 43028.22 17.82 1.62 77.4 0 0.01 524860.8 2.92 9.59 85.39 0.84 0.01 L5-9 147319.8 17.08 20.37 0 61.51 0 417489.8 1.5 14.29 80.71 2.14 0.01 L5-10 502187.9 3.32 12.18 81.22 1.49 0 L5-11 560743.8 4.22 13.84 77.78 2.8 0.01 L5-12 120626.4 17.96 0.09 26.53 42.05 0 454350.8 3.97 13.18 79.21 2.29 0.01   107   No. Area  Cracks/Holes (%) Liptinite (%) Vitrinite (%) Inertinite (%) Minerals (%) L6-1 529360.1 0.08 5.34 94.28 0 0 L6-2 579390.6 0.1 4.4 95.17 0 0 L6-3 579390.6 0.5 4.4 94.69 0 0 L6-4 579390.6 0.14 8.06 90.99 0.35 0 L6-5 525904.2 0.43 9.79 88.08 1.01 0.01 L6-6 579390.6 0.11 4.89 93.37 1.24 0 L6-7 538375.0 2.2 15.06 80.05 1.43 0.01 L6-8 579390.6 0.35 4.16 95.96 0.18  L6-9 519368.9 0.57 6.33 91.16 1.29 0 L6-10 552735.8 1.22 16.92 80.39 0.84 0 L6-11 579390.6 2.56 23.56 59.57 13.06 0.01 L6-12 549717.1 4.57 15.56 74.5 4.36 0  No. Area  Cracks/Holes (%) Liptinite (%) Vitrinite (%) Inertinite (%) Minerals (%) L7-1 579390.6 0.54 12.93 86.07 0 0 L7-2 8721.55 5.93 93.48 0 0 0 568112.0 0.17 10.84 87.55 0.79 0 L7-3 20160.99 25.23 0 0 68.68 0 550842.0 2.21 12.95 82.78 1.24 0 L7-4 50750.06 25.8 73.94 70.71 4.54 0 135553.8 0.18 2.12 96.02 1.21 0 393353.7 2.84 20.54 70.71 4.54 0 L7-5 303506.8 3.18 14.88 77.48 3.22 0 237659.6 1.9 10.68 78.56 7.68 0 L7-6 250932.9 0.41 0.67 98.88 0 0 220565.2 5.23 14.01 65.83 12.94 0 106740.7 0.18 0.52 98.96 12.94 0 L7-7 579390.6 2.77 8.15 88.24 0.1 0 L7-8 407880.4 2.68 4.98 87.6 3.98 0 L7-9 579390.6 1.81 7.52 88.2 1.74 0 L7-10 579390.6 1.14 7.58 89.04 1.41 0 L7-11 82315.95 14.67 0 8.62 75.95 0 108   No. Area  Cracks/Holes (%) Liptinite (%) Vitrinite (%) Inertinite (%) Minerals (%) L7-12 493916.5 2.91 9.65 78.76 7.77 0   No. Area  Cracks/Holes (%) Liptinite (%) Vitrinite (%) Inertinite (%) Minerals (%) L8-1 579390.6 1.52 10.6 86.93 0.1 0 L8-2 579390.6 4.94 26.45 67.71 0 0.06 L8-3 579390.6 2.15 14.56 82.52 0.04 0 L8-4 579390.6 0.47 11.22 87.19 0.27 0 L8-5 579390.6 1.8 10.87 85.95 0.5  L8-6 579390.6 0.42 7.01 91.68 0.25 0 L8-7 579390.6 2.8 18.99 77.78 0.04  L8-8 579390.6 1.51 12.1 85.25 0.38 0 L8-9 579390.6 1.51 12.1 85.25 0.38 0 L8-10 579390.6 1.77 0 98.21 0 0 L8-11 579390.6 3.1 12 83.46 0.27 0 L8-12 579390.6 0.25 22.69 75.2 0.77 0.02  109   Appendix E  Contact angle measurements results The contact angle values and corresponding average contact angle with standard deviations. No. Sessile drop Captive bubble Average 1ST 2ND 3RD Standard Deviation Average 1ST 2ND 3RD Standard Deviation L1 57.56 54.98 58.57 59.14 2.3 44.80 46.03 44.73 43.63 1.2 L2 62.37 62.67 63.89 60.54 1.7 42.31 43.83 41.66 41.43 1.3 L3 71.67 71.90 72.54 70.56 1.0 59.74 62.12 60.35 56.76 2.7 L4 71.56 72.13 72.69 69.85 1.5 55.97 53.64 52.91 61.36 4.7 L5 64.23 64.79 66.49 61.42 2.6 48.95 49.85 49.69 47.32 1.4 L6 69.70 68.81 69.02 71.27 1.4 53.83 55.67 55.48 50.33 3.0 L7 68.90 69.67 70.21 66.81 1.8 55.03 56.72 56.68 51.68 2.9 L8 51.96 50.57 50.59 54.73 2.4 42.87 40.32 43.63 44.67 2.3 H1 87.82 88.92 90.53 84.02 3.4 74.96 76.54 76.53 71.81 2.2 H2 70.50 73.54 66.98 70.98 3.3 63.19 62.23 61.11 66.22 2.2 H3 97.44 93.52 95.21 103.60 5.4 80.72 82.34 83.50 76.32 3.1 H4 80.48 78.21 77.07 86.15 4.9 62.41 61.91 62.68 62.65 0.4 H5 83.68 83.01 82.30 85.74 1.8 69.25 70.67 69.81 67.28 1.4 H6 84.79 84.96 83.10 86.31 1.6 72.52 73.16 72.42 71.97 0.5 H7 88.21 90.82 89.82 84.00 3.7 67.54 67.18 66.57 68.88 1.0 H8 79.47 79.84 80.16 78.42 0.9 64.53 63.87 63.14 66.59 1.5 110   Appendix F  Contact angle measurements results The example of contact angle value (the first contact angle measurement) versus time using sessile drop (H1 to H8)  111   The example of contact angle value (the first contact angle measurement) versus time using sessile drop (L1 to L8)  112   The example of contact angle value (the first contact angle measurement) versus time using captive bubble (H1 to H8)  113   The example of contact angle value (the first contact angle measurement) versus time using captive bubble (L1 to L8)  114   Appendix G  Micro-FTIR measurements results The average spectra using micro-FTIR spectroscopy on predetermined areas (H1 to L8) No. CHar  CHal CH3 CH2 C=O C=C CHar  Out-of-Plane CHar Out-of-Plane  3002-3083 cm-1 2996-2803 cm-1 2981-2942 cm-1 2942-2902 cm-1 1832-1677 cm-1 1677-1521 cm-1 904-700 cm-1 870 cm-1 812 cm-1 750 cm-1 H1 0.97 10.78 14.62 24.61 0.95 18.56 6.92 0.88 0.97 1.42 H2 2.38 12.58 19.71 20.75 2.39 17.52 10.22 14.84 13.10 11.91 H3 1.31 14.40 18.54 27.71 0.53 20.68 6.47 0.98 0.99 0.80 H4 2.36 14.96 20.32 25.44 2.61 22.85 13.72 1.47 1.57 1.74 H5 2.28 16.56 22.63 30.56 1.50 19.81 14.50 1.44 1.41 1.65 H6 2.32 17.79 25.00 33.49 1.08 21.69 10.82 1.45 1.41 1.89 H7 1.41 11.78 17.40 25.19 0.47 11.29 6.62 3.88 2.21 3.13 H8 1.63 9.56 15.77 17.59 1.05 16.29 7.50 6.45 5.18 5.25 L1 0.01 16.40 13.30 19.75 1.19 17.20 4.38 2.83 3.14 3.46 L2 0.01 18.55 14.70 23.58 1.63 17.69 4.53 2.83 4.02 3.63 L3 0.24 11.36 11.59 14.22 5.14 18.40 4.36 2.47 1.97 1.92 L4 0.23 10.27 10.66 11.84 4.71 17.73 3.85 2.32 2.14 2.18 L5 0.12 12.13 11.07 17.97 4.69 16.56 3.54 1.54 4.41 4.48 L6 0.07 12.49 12.21 16.63 5.00 16.95 3.84 1.74 2.58 2.67 L7 0.12 11.63 11.20 15.00 4.80 16.42 3.59 1.90 3.08 3.27 L8 0.01 28.61 29.56 46.66 0.75 28.93 8.40 24.37 24.94 21.75 

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