Efficient Decomposition of Environmentally Persistent Perfluorocarboxylic Acids by Use of Persulfate as a Photochemical Oxidant

TLDR

The study aimed to develop a photochemical persulfate-based method to neutralize stationary sources of persistent perfluorocarboxylic acids in water. Photolysis of persulfate generates highly oxidative sulfate radical anions that rapidly decompose C4–C8 perfluoroalkyl PFCAs. The approach fully mineralized 1.35 mM PFOA to fluoride and CO₂ within 4 h, achieving an 11‑fold faster rate than photolysis alone and successfully degrading perfluorononanoic acid in floor‑wax solution.

Abstract

Photochemical decomposition of persistent perfluorocarboxylic acids (PFCAs) in water by use of persulfate ion (S2O82-) was examined to develop a technique to neutralize stationary sources of PFCAs. Photolysis of S2O82- produced highly oxidative sulfate radical anions (SO4•-), which efficiently decomposed perfluorooctanoic acid (PFOA) and other PFCAs bearing C4−C8 perfluoroalkyl groups. The major products were F- and CO2; also, small amounts of PFCAs with shorter than initial chain lengths were detected in the reaction solution. PFOA at a concentration of 1.35 mM (typical of that in untreated wastewater after an emulsifying process in fluoropolymer manufacture) was completely decomposed by a photochemical system with 50 mM S2O82- and 4 h of irradiation from a 200-W xenon−mercury lamp. The initial PFOA decomposition rate was 11 times higher than with photolysis alone. All sulfur-containing species in the reaction solution were eventually transformed to sulfate ions by this method. This method was successfully applied to the decomposition of perfluorononanoic acid contained in a floor wax solution.