Spinel ZnMn2O4 nanosphere for the efficient Sulfamethazine degradation under visible light irradiation and photoelectrochemical study

Abstract

This study assessed the efficacy of ZnMn2O4 (ZMO) spinel structure, synthesized via the solvothermal method, as a photocatalyst for the efficient photocatalytic degradation of Sulfamethazine (SMT) under visible light conditions. Comprehensive analyses involving FESEM, TEM, EDX, XRD, Raman, FTIR, XPS, and BET have been conducted, and the results strongly supported the successful preparation of ZMO. The optical characteristics of the as-synthesised sample was assessed using UV–VIS DRS, which indicated a band gap that was conducive to the effective absorption of visible light. Mott-Schottky (M-S) plot, Electrochemical Impedance Spectroscopy (EIS) analysis and photocurrent study have been utilised for knowing the type of semiconductor, kinetic charge transfer and charge separation and transfer within the on and off areas respectively. Degradation of SMT has been done in a suitable photochemical reactor and reaction rate constant has been evaluated. The study employed RSM modelling with Box-Behnken design to optimise various operational parameters in a photocatalytic reaction. These parameters included solution pH, dosage of ZMO, and initial concentration of SMT. Following a duration of 60 minutes under ideal circumstances, the residual concentration of SMZ declined to a level that is no longer detectable. The utilisation of tandem mass spectrometry has been employed to discover the transition products and their existence has been subsequently utilised to propose a degradation pathway.