Construction of SnS2/Ni–Fe LDH type-II heterojunction for efficient promotion of PMS activation and metronidazole degradation

Photocatalysis-peroxymonosulfate (PMS) activation system is regarded as a promising strategy for antibiotic degradation. Herein, a type-II SnS 2 /NiFe LDH heterojunction assembled by nanosheets was constructed to realize the dual modulation of photogenerated carrier directional migration and PMS activation sites. The intimate and large coupled interface facilitated the charge separation and transfer. And the optimization of the electronic structure in the heterojunction enabled good visible light absorption capacity. Benefiting from the construction of type-II heterojunction, the Fe 2+ /Fe 3+ and Ni 2+ /Ni 3+ redox cycles in SnS 2 /NiFe LDH had been greatly improved, which further promoted the PMS activation. The constructed heterojunction achieved excellent metronidazole (MNZ) degradation performance (93.9% removal within 30 min) via PMS activation-assisted photocatalysis under visible light irradiation, which was greatly enhanced compared to the control conditions of photocatalysis without PMS (3.5%) or without light irradiation (78.1%). It also demonstrated excellent stability and functioned well across a wide pH range (3–11). The quenching experiments revealed that ·OH and h + were the main reactive species for MNZ oxidation. The mechanism analysis further confirmed that the transfer of photogenerated carriers was consistent with the type-II mode. This study is expected to provide new insights into design and application of type-II heterojunction in PMS activation for efficient wastewater treatment. Graphical abstract