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Dixit, Fuhar

University of British Columbia

Per- and polyfluoroalkyl substances (PFAS) are anthropogenic compounds with numerous industrial applications. Their widespread use in specialized chemical operations, such as firefighting foams, industrial solvents and textile coatings has made them ubiquitous in the present environment. Significant concentrations of PFAS have been detected in the drinking and recycled water sources over the past few years and have been associated with human health risks. Removal of PFAS from drinking water treatment systems is a major challenge since conventional water treatment technologies have limited effectiveness. Even advanced water treatment processes such as low-pressure membrane filtration (MF/UF) and ozonation are considered ineffective for PFAS removal. Anionic ion exchange (IX) resins offer a promising and cost-effective treatment alternative for natural waters affected by PFAS. In the present research, I investigated the application of anionic organic scavenger ion exchange (IX) resins, nonionic IX resins, PFAS-specific resins and Ti₃C₂ MXenes (novel two-dimensional metal carbides) for the simultaneous removal of dissolved organic matter (DOM), anionic and zwitterionic PFAS, and inorganic ions from natural waters. Several PFAS including carboxylic PFAS, sulfonic PFAS, emerging PFAS (such as GenX and zwitterionic fluorotelomer betaines) were tested. The PFAS-specific resins exhibited the fastest uptake kinetics amongst all anionic PFAS investigated, with ~15% removal of dissolved DOM. The organic scavenger resin (A860), removed ~70% of dissolved DOM (C₀ ≤ 5 mg C/L). The resin breakthrough (Ctreated (PFAS)>70 ng/L) was observed around 120,000 bed volumes (BV) for the PFAS-specific resins, whereas the breakthrough was noted around 20,000 BV for organic scavenger resins in influent waters with ~5 mg C/L dissolved DOM. Yet, a mass balance on PFAS and OM removal indicated ~90-98% site saturation (in milli-equivalents) on all IX resins before exhaustion. More importantly, when regenerated with 10% NaCl, the organic scavenger resin exhibited PFAS and DOM removal capabilities for longer operational BVs in comparison to the PFAS-specific resins. However, A860 necessitated approximately 3-fold higher contact times for achieving the same degree of PFAS removal when compared to the PFAS-specific resins, a critical tradeoff between reuse (OPEX) and shorter-contact times (CAPEX).

Text

2024-04-30

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/81267

Chemical and Biological Engineering

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/