Peroxymonosulfate activation by Ru/CeO2 for degradation of Triclosan: Efficacy, mechanisms and applicability in groundwater

Although ruthenium (Ru) catalyst has attracted extensive attention in many chemical industries, its application in sulfate radical-based advanced oxidation processes (AOPs), especially the heterogeneous Ru activator for groundwater remediation, is less studied. In this study, Ru species was loaded on cerium dioxide (CeO2) particles to prepare the stable Ru/CeO2, and it served as the peroxymonosulfate (PMS) activator to degrade triclosan (TCS) which is a toxic and recalcitrant pollutant in groundwater worldwide. Ru/CeO2 showed a greater performance for activating PMS when compared with some other AOPs, and TCS in the system can be almost completely removed within 10 min. Ru/CeO2 and PMS dosage can undoubtedly affect the TCS removal rate, and acid or neutral environments favored the degradation. Besides, interference of potential complex components in groundwater on the TCS removal rate must get attention, Cl- had an obvious promotion effect, while HCO3– inhibited these processes; metal cations could slightly enhance the PMS activation, while humic acid had an inhibitory effect. Theoretically, 1O2 (non-radical pathway) was determined to play the major role in TCS removal during PMS activation in the system, while ·OH and SO4·- (radical pathway) played a minor role. Importantly, the activator has good stability and reusability, and its TCS removal capacity decreased by only 4.04% after five cycles; it also performed excellently in batch experiments with natural groundwater and in soil column experiments under different pH and hydraulic conditions. These indicate that the Ru/CeO2/PMS system has promising applicability for TCS remediation in groundwater environments.