Micro-nano structured CoS: An efficient catalyst for peroxymonosulfate activation for removal of bisphenol A

Co-based catalysts demonstrated high performance for activating peroxymonosulfate (PMS). In the present study, micro-nano structured CoS was prepared by a simple solvothermal reaction and the influence of sulfur in CoS in the PMS activation for bisphenol A (BPA) decomposition was investigated systematically. It was found that micro-nano structured CoS exhibited remarkable catalytic activity with 90% removal of 20 mg L-1 BPA within 10 min under 0.05 g L-1 CoS and 0.3 mmol L-1 PMS at 25 degrees C. The peso-first reaction rate constant for BPA degradation in this system was 0.37 min(-1) , 1.1 and 1.5 times that by using surface sulfur modified Co3O4 (S-Co3O4) and Co3O4 nanoparticles as a catalyst. Factors influencing BPA degradation were also examined, including initial pH (pH(0)), dosages of PMS and CoS. The BPA removal was enhanced with the raise from 3 to 11 in the reaction solution due to enhanced PMS decomposition and free radicals production. Moreover, the conversion of SO4 center dot- to (OH)-O-center dot as the main reactive species was observed as pH(0) was varied from 3 to 10 through electron paramagnetic resonance (EPR) analysis and quenching experiments. BPA degradation pathways by CoS/PMS system were proposed based on LC-MS results of degradation intermediates. Finally, a possible mechanism for activation of PMS by CoS was proposed according to the surface evolution of CoS during the reaction process by XPS spectra.