Insight into the mechanisms of BPS degradation by electro-Fenton method modified by Co-based nanoparticles on the oxidized carbon cathode

4,4′-sulfonyldiphenol, as one type of persistent organic pollutants, has become an environmental problem because of its toxicity and harmfulness. In this study, cobalt-based nanoparticles on oxidized carbon black (Co-OBC) rich in oxygen functional groups and pyrrole nitrogen, which were adopted as catalyst to promote the performance for BPS degradation using electro-Fenton method. The results show that Co-OBC exhibited better performance in degradation of BPS by electro-Fenton than cobalt-based nanoparticles on carbon black (Co-BC), and BPS could be completely degraded within 15 min under optimal conditions (c(Fe2+) = 0.3 mM, pH 3, U = -0.5 V). In order to explore the degradation mechanisms of BPS, Liquid Chromatography-Mass Spectrometry (LC-MS) analysis was combined with Density Functional Theory (DFT) calculation. Three degradation paths were proposed. More importantly, the decomposition free energy of BPS in path I was 15.5 kcal/mol, which is the lowest of three paths. Therefore, path I was the main pathway of BPS degradation, and other pathways were secondary. Finally, ECOSAR software prediction revealed that the degradation of BPS could reduce the toxicity step-by-step, which was beneficial for environmental protection. By analyzing the degradation mechanisms and toxicity prediction of BPS, we can better understand the characteristics of persistent compounds and their harm to the environment, which can be beneficial to solve environmental pollution.