Enhanced catalytic activities of natural iron ore in peroxymonosulfate activation assisted by WS2 for rapid degradation of pollutants

Abstract

The seek for efficient and low-cost heterogeneous catalysts for peroxymonosulfate (PMS) activation holds great promise in the treatment of organic contaminants. Natural iron ore (IO) has been identified as a potential catalyst due to its low environmental risk and cost-savings. Herein, the commercial tungsten sulfide (WS2) was employed to significantly enhance the performance of IO towards PMS activation (WS2/IO/PMS) for the removal of pollutants. This system demonstrated remarkable performance, with >98.2% removal of organic pollutants in 60 min, including dyes and antibiotics, under the optimized conditions of 0.50 g/L IO, 0.10 g/L WS2, 2.0 mM PMS, and initial pH 6.0. The apparent degradation rate constant (k) of Acid Orange 7 (AO7) in WS2/IO/PMS system (0.073 min−1) was about 30.4-fold and 104.3-fold higher than that of in WS2/PMS system (0.0024 min−1) and IO/PMS system (0.0007 min−1), respectively. Mechanism insights revealed the crucial role of WS2 in boosting the degradation kinetics in the WS2/IO/PMS system. The exposed W4+ or S2− species on WS2 surface were the dominant reactive sites responsible for the promotion of Fe3+/Fe2+ redox cycles and subsequently the PMS activation. Importantly, the electrochemical analysis demonstrates that the iron ions released from IO were prone to adsorb onto the WS2 surface, forming active Fe species with high oxidative potential, which remarkably accelerated the electron transfer for Fe2+ regeneration, thereby enhancing PMS activation to generate reactive oxygen species like hydroxyl radicals (OH), sulfate radicals (SO4−) and superoxide radicals (O2−). Furthermore, the practicability of WS2/IO/PMS system was validated by treating various pollutants and investigating the interference of coexisting anions in water. Overall, this study provides a green and advanced strategy to enhance the PMS activation by natural iron ore for efficient water decontamination.