Treatment of perfluoroalkyl acids by heat-activated persulfate under conditions representative of in situ chemical oxidation

• Published in: Chemosphere (Oxford) Vol. 206; pp. 457 - 464
• Main Authors: Bruton, Thomas A., Sedlak, David L.
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.09.2018
• Subjects: aquifers; Caprylates - chemistry; carboxylic acids; chlorides; drinking water; Fluorocarbons - chemistry; foams; groundwater contamination; Hot Temperature; In situ chemical oxidation; metals; oxidation; Oxidation-Reduction; perfluorooctane sulfonic acid; perfluorooctanoic acid; persulfate; PFAS; PFOA; PFOS; Remediation; sediments; Water Pollutants, Chemical - analysis; Water Pollutants, Chemical - chemistry; Water Purification - methods; water treatment; In situ chemical oxidation; Remediation; persulfate; PFOA; PFAS; PFOS
• ISSN: 0045-6535; 1879-1298; 1879-1298
• DOI: 10.1016/j.chemosphere.2018.04.128

Perfluoroalkyl acids (PFAAs) are a class of organic contaminants notable for their extreme persistence. The unique chemical properties of these compounds make them difficult to remove from water using most standard water treatment techniques. To gain insight into the possibility of remediating contaminated groundwater by in situ chemical oxidation with heat-activated persulfate, PFAA removal and the generation of transformation products were evaluated under laboratory conditions. Solution pH had a strong influence on the removal of perfluorooctanoic acid (PFOA), resulting in its transformation into shorter-chain perfluorocarboxylic acids (PFCAs) at pH values below 3. The presence of chloride and aquifer sediments decreased the efficiency of the process by less than 25% under conditions likely to be encountered in drinking water aquifers. Perfluorooctane sulfonic acid (PFOS) was not transformed by heat-activated persulfate under any of the conditions tested. Despite challenges related to the need to manipulate aquifer pH, the possible generation of undesirable short-chain PFCAs and chlorate, and metals mobilization, heat-activated persulfate may be a useful treatment technology for sites contaminated with PFCAs and fluorotelomer-based compounds, including those used in current-generation aqueous film-forming foams. •PFOA is mineralized by sulfate radical at pH values below 3.•Chloride must be converted into chlorate before PFOA removal occurs.•The presence of aquifer solids slows but does not prevent PFOA mineralization.