UBC Theses and Dissertations
Comparative solvent extraction studies of molybdenum and other impurity metals in sulfuric acid medium by cyanex® 600 and fentamine™ TA0810 Dutta, Brighty
Molybdenum is widely used as an alloying element in the manufacture of steels and super alloys. The widespread use of the element encourages a growing need to develop extraction processes for recovery from both primary and secondary sources. The Cytec Solvay Group has developed a solvent extractant, CYANEX® 600 for the recovery of molybdenum from acidic solutions originating from both low grade (e.g., copper solvent extraction raffinates, smelter dusts and slags) and high grade (molybdenite) molybdenum sources. CYANEX® 600 is a purified form of CYANEX® 272 with the active component, bis(2,4,4- trimethylpentyl)phosphinic acid. Heap leaching of copper from ores followed by solvent extraction is practiced commercially and the raffinate solution after the copper solvent extraction has substantial levels of molybdenum along with minor impurity metal ions in acidic pH range. The extraction behavior of CYANEX® 600 towards molybdenum in sulfuric acid medium was evaluated. The uptake of molybdenum increased with the increase in concentration of CYANEX® 600. An organic solution of 0.1 M CYANEX® 600 extracted ~97 % of 0.04 M Mo (VI) at pH < 2 and the predominant extracted species was found to be molybdenyl cation, MoO₂²⁺. The approximate stoichiometry of the extracted complex was Mo: [CYANEX® 600]dimer = 1:2. Effective stripping could be achieved with 0.25 M NH₄OH at O/A = 1 in two strip stages. A tri-alkyl amine, FENTAMINE™ TA0810 was considered to compare the recovery behavior of molybdenum. At the lower initial pH values (< 2), almost all the molybdenum was extracted. The slope obtained from the linear regression for FENTAMINE™ TA0810 ensured that the ratio of extractant to metal species is approximately 2, which confirmed H₂Mo₈O₂₆²ˉ as the predominant extracted species. A solution of 1 M NH₄OH stripped 99.9 % of Mo (VI) from the loaded organic phase after three stages at A/O = 1. The impurity loading behavior of CYANEX® 600 and FENTAMINE™ TA0810 in sulfuric acid solutions at low pH was studied and suitable scrubbing reagents were examined and recommended for the removal of potential impurity metal ions from the molybdenum loaded organic solution.
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