Enhanced decomposition of long-chain perfluorocarboxylic acids (C9−C10) by electrochemical activation of peroxymonosulfate in aqueous solution

Abstract

The decomposition of long-chain perfluorocarboxylic acids (PFCAs), including perfluorononanoic acid (PFNA) and perfluorodecanoic acid (PFDA), were investigated by electrochemical activation of peroxymonosulfate (PMS) on porous Ti/SnO2-Sb membrane anode. The results indicated that PMS activation could efficiently promote PFNA/PFDA decomposition, with pseudo-first-order rate constants about 3.12/2.06 times as compared with that of direct electro-oxidations. The energy consumptions of PFNA and PFDA decomposition were 36.31 and 37.46 kWh·m−3·order−1, respectively. The quantitative detection results of •OH with electron paramagnetic resonance (EPR) demonstrated that PMS activation promoted •OH formation. The inhibited performance in radical scavengers indicated both •OH and SO4•− might be mainly involved in PFNA decomposition, while SO4•− might be mainly involved in PFDA decomposition during PMS activation process. The mineralization mechanism for long-chain PFCAs decomposition which was mainly by repeating CF2-unzipping cycle via radical reaction based on the intermediates verification and mass balance of C and F, was proposed. These results suggested that electrochemical activation of PMS on porous Ti/SnO2-Sb membrane anode exhibited high efficiency in mineralizing PFNA and PFDA under mild conditions. This work might provide an efficient way for persistent organic pollutants, including, but not limited to long-chain PFCAs elimination from wastewater.