Development of a heterogenous catalyst FeWO4/Cu2S as peroxymonosulfate activator for effective sulfachloropyridazine elimination

This work successfully synthesized magnetic FeWO4/Cu2S through a facile method with efficient peroxymonosulfate (PMS) activation to eliminate sulfachloropyridazine (SCP) in water, in which 97.56% of SCP was removed in 30 min with activating only 0.2 mM PMS. Factors such as calcination temperature, the addition amounts of WS2 in FeWO4/Cu2S, molar ratio of Cu/Fe in FeWO4/Cu2S, catalyst dosage, solution pH, inorganic anions and natural organic matters（NOM）were investigated. It was found that in FeWO4/Cu2S at 1:2 possessed the best catalytic performance for PMS. FeWO4/Cu2S performed well in a wide pH range (3–9) and the effect was better under acidic conditions. A high catalyst dosage could supply more catalytic active sites for PMS activation and encourage the production of reactive oxygen species. Anions (HCO3−and HPO42−) and NOM significantly inhibited SCP degradation, whereas Cl− had only a tiny inhibitory impact. In addition, H2PO4− and NO3− demonstrated duality in the degradation of SCP. The oxidation process was dominated by non free radical oxidation by 1O2 rather than free radicals oxidation by HO⋅ and SO4•−. Three SCP degradation pathways—SO2 extrusion, S-N bond cleavage and hydroxylation were proposed according to intermediate products analysis. The mechanism was found that the introduction of W improved the the dual metals cycles of Fe3+/Fe2+ and Cu+/Cu2+ which could efficiently promote PMS activation. In addition, the magnetic FeWO4/Cu2S was easy to separate after reaction, which had great application potential in the water treatment.