Electrochemical Oxidation of Perfluoroalkyl Acids in Still Bottoms from Regeneration of Ion Exchange Resins

Quingguo Huang | University of Georgia



Ion exchange (IX) resin has been shown advantageous in removing per- and polyfluoroalkyl substances (PFASs) from groundwater and gained popularity in recent years. The application of IX resin requires a regeneration procedure involving the use of a mixture of sodium chloride, water and methanol. The methanol in spent regenerant needs to be recovered by distillation to make the process economically feasible, and thus a still bottom containing highly concentrated PFASs, chloride, and residual organic content in water is generated. The current practice on still bottom treatment is off-site incineration, but such an option can cause secondary air pollution, and may become elusive as regulation evolves. Recent results have indicated that electrochemical oxidation (EO) can be coupled to IX resins to treat the highly concentrated PFASs in the still bottoms, and thus eliminate the necessity of off-site incineration.

This proof-of-concept study is designed to systematically investigate how the major constituents in the IX resin still bottoms (chloride and organic contents) may impact the EO treatment efficiency and the final water quality. This project will screen the optimum conditions of EO process, and identify the ranges of chemical compositions of still bottoms that are suitable for EO treatment.

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Technical Approach

This study is designed to probe the specific hypothesis that the EO process can be optimized to effectively mineralize PFAAs in still bottom samples with acceptable energy consumption, while at the meantime limit the formation of chlorinated byproducts. Three tasks are planned to test the hypothesis: Task 1 will screen the most effective EO operation conditions, and identify the chemical compositions suitable for EO treatment using spiked solutions containing PFOA and PFOS and other major constituents present in still bottoms; Task 2 will examine real still bottom samples, and further verify the relationships depicting the dependence of PFAA treatment efficiency and chlorinated products formation on the EO conditions and the sample compositions; Task 3 will evaluate oxidative technologies as pretreatment to manage the properties of still bottoms for effective EO treatment.

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IX resin has been demonstrated to be effective in removing low concentrations of PFASs found in groundwater, but as a non-destructive technology, the treatment of its ultimate waste is costly and may soon be restricted. This project will provide a cost-effective means to destroy the PFASs concentrated in IX resin regenerant brine, and thus avoid the necessity of off-site waste treatment. The study will provide a basis for a novel treatment scheme by coupling IX resin with EO, and thus provide an energy-effective total solution for PFAS-impacted groundwater. The IX resin and EO processes are synergetic in that PFAAs are greatly concentrated through IX that improve the energy-efficiency of EO treatment, and the EO-treated solution can be recycled for IX resin regeneration to reuse water and chloride. (Anticipated Project Completion - 2019)

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Points of Contact

Principal Investigator

Dr. Qingguo Huang

University of Georgia

Phone: 770-229-3302

Program Manager

Environmental Restoration