Z-scheme S, B co-doped g-C3N4 nanotube@MnO2 heterojunction with visible-light-responsive for enhanced photodegradation of diclofenac by peroxymonosulfate activation

In this study, the manganese dioxide (MnO2) nanosheets were successfully embedded onto boron and sulfur co-doped g-C3N4 (CNBS) nanotubes to construct the flower-like core–shell CNBS@MnO2 heterojunction with Z-scheme structure for the enhanced photodegradation of diclofenac (DCF) in the presence of peroxymonosulfate (PMS) and 460-nm visible light. The CNBS@MnO2 provides large specific surface area and reduced interfacial resistance for rapid electron transport. Moreover, the redox cycling of Mn species effectively activates PMS to produce sulfate radicals for DCF photodegradation. The PMS-based photodegradation of DCF over CNBS@MnO2 displays the excellent photodegradation performance after 15 min of irradiation, and the efficiency is highly dependent on initial pH, ion species, and concentrations of PMS and DCF. The CNBS@MnO2 also shows its excellent stability and reusability over ten cycles. Besides, h+, O2●− and SO4●− are the dominantly reactive species for the enhanced degradation of DCF over Z-scheme CNBS@MnO2 heterojunction. The possible reaction mechanism as well as the degradation pathway of DCF over CNBS@MnO2 in the presence of PMS is also proposed. Results clearly highlight the superior photoactivity of Z-scheme CNBS@MnO2 toward micropollutant degradation by PMS activation, which can open an avenue to fabricate the g-C3N4 nanotube@metal oxide structure as an effective activator for water and wastewater purification.