Electrochemical generation of persulfate and its performance on 4-bromophenol treatment

Abstract

Abstract Adding additional persulfate is a common way in sulfate radical-based advanced oxidation processes. The present study provides an alternative which is in situ preparation of persulfate from sulfate-containing solution to deal with wastewaters, avoiding the separation, purification and transportation of persulfate. The electrochemical synthesis of persulfate in mild conditions (low sulfate concentration and weak acidity) was realized in anode chamber and the performance of prepared persulfate was tested using 4-bromophenol as representative pollutant in Cathode/Fe3+ system. The increase of SO42− concentration and anode current density improve persulfate production, but the utilization efficiency of SO42− increases more and more slowly and the current efficiency doesn’t increase above 0.4 A/cm2. The additive of SCN− significantly improves persulfate generation, while this additive and possible by-product has no significant effect on the 4-bromophenol degradation in Cathode/Fe3+ system. With initial (NH4)2SO4 concentration of 0.30 M, initial pH of 5.6 and NH4SCN dosage of 2.6 mM, the in situ generated persulfate can totally remove 0.50 mM 4-bromophenol and more than half of TOC in Cathode/Fe3+ system with Fe3+ dosage of 2.0 mM. The increase of Fe3+ dosage, current density and initial SO42− concentration favor organics removal. A high initial organics concentration is beneficial to the persulfate utilization.