Novel MIL-53(Fe)/ZnO nanocomposite mediated by persulfate in photocatalytic degradation of sulfamethazine under visible light

This work aims to address some significant restrictions on the use of photocatalysis, including high e-/h+ recombination rate, and semiconductors with wide-band energy resulting in limited visible-light harvesting. Herein, we apply a novel hierarchical MIL-53(Fe)/ZnO nanocomposite for the degradation of sulfamethazine in the presence of persulfate under visible light irradiation. The ultrafine nanocomposite MIL-53(Fe)/ZnO was obtained by synthesizing Zn-free MIL-53Fe and employing it as a reactive template under a hydrothermal process. A set of experiments with a Box Behnken design was conducted to optimize the operating parameters by response surface method (RSM). Complete degradation of 10 mg/L of SMZ was attained after 30 min under the optimum operational conditions (catalyst dose = 0.2 g/L, pH = 3, and persulfate loading = 0.39 g/L). The SMZ degradation followed the Langmuir-Hinshelwood model. In addition, about 78% TOC removal was observed under the optimum conditions. Also, it was proven that MIL-53(Fe)/ZnO had high photostability after being reused for five successive cycles. A possible degradation pathway of SMZ was proposed based on the detection results of intermediates by LC-MS/MS, suggesting that the cleavage of the S-N bond and subsequent removal of sulfone moiety was the primary degradation pathway.