Enhanced peroxymonosulfate activation by (NH4)2Mo3S13 for organic pollutant removal: Crucial roles of adsorption and singlet oxygen

Abstract

Though sulfide materials have attracted much attentions in sulfate radicals (SO4•–) based advanced oxidation processes, the catalytic performance and inherent mechanism of ammonium thiomolybdate ((NH4)2Mo3S13) activating peroxymonosulfate (PMS) are less studied. In this work, (NH4)2Mo3S13 materials were prepared by the hydrothermal method and applied as the PMS activator to degrade various organic pollutants. The (NH4)2Mo3S13/PMS system significantly decomposed tetracycline, oxytetracycline, methylene blue, and congo red. However, the degradation of carbamazepine, disodium p-nitrophenyl phosphate, norfloxacin, and sulfamethoxazole was relatively weaker. This selective catalytic performance was attributed to the adsorption affinities of (NH4)2Mo3S13 for organic pollutants. Besides, the exposed Mo(IV) and S on the surface of (NH4)2Mo3S13 were found to be the main active sites for activation of O2 and PMS. Among various active species, singlet oxygen was the crucial active species, while sulfate and hydroxyl radicals played limited roles for the removal of methylene blue in (NH4)2Mo3S13/PMS system. The findings of this work proved (NH4)2Mo3S13 materials are promising catalyst for organic pollutants removal in advanced oxidation processes.