Thermally regenerable FeS/N-doped biochar catalyzed peroxydisulfate oxidative destruction of aqueous triclosan

Abstract

Ferrous sulfide loaded on N-doped biochar (FeS/NBC) was prepared to pyrolyze jute fibers pretreated with (NH4)2Fe(SO4)2. FeS/NBC-catalyzed degradation of triclosan was assessed by peroxydisulfate oxidation. The effects of solution pH, foreign anions and peroxydisulfate concentration were investigated. It is found that neutral pH was conducive to removal of triclosan, achieving about 99% triclosan removal and 65% mineralization level. The presence of HCO3− and HPO42− will inhibit triclosan degradation, but Cl− showed a considerable promotion. Importantly, the spent FeS/NBC catalyst can be regenerated via a reheat treatment to completely recover the catalytic activity. Electron paramagnetic resonance and quenching experiments demonstrated that radicals (OH, SO4−O2−) and non-radical (1O2) were the major reactive species in the reaction. GC–MS analysis identified that the residual intermediates from cycloaddition and ether bond breakage existed in the reaction solution, and recommended radical-dominated and singlet oxygen-assisted degradation pathways. The evaluation of actual samples showed that the presence of Cl− could enhance the removal of triclosan, and the generation of chlorine-based radicals was suggested as the main reason for this result. This study proved FeS/NBC-PDS system could efficiently remove triclosan in water, and the catalyst can be regenerated by a simple reheat treatment.