Photocatalytic degradation of sulfamethoxazole by hierarchical magnetic ZnO@g-C3N4: RSM optimization, kinetic study, reaction pathway and toxicity evaluation

Amir Mirzaei; Laleh Yerushalmi; Zhi Chen; Fariborz Haghighat

doi:10.1016/j.jhazmat.2018.07.077

Photocatalytic degradation of sulfamethoxazole by hierarchical magnetic ZnO@g-C₃N₄: RSM optimization, kinetic study, reaction pathway and toxicity evaluation

J Hazard Mater. 2018 Oct 5:359:516-526. doi: 10.1016/j.jhazmat.2018.07.077. Epub 2018 Jul 21.

Authors

Amir Mirzaei¹, Laleh Yerushalmi¹, Zhi Chen², Fariborz Haghighat¹

Affiliations

¹ Department of Building, Civil and Environmental Engineering (BCEE), Faculty of Engineering & Computer Sciences, Concordia University, Montreal, Canada.
² Department of Building, Civil and Environmental Engineering (BCEE), Faculty of Engineering & Computer Sciences, Concordia University, Montreal, Canada. Electronic address: zhichen@alcor.concordia.ca.

PMID: 30086522
DOI: 10.1016/j.jhazmat.2018.07.077

Abstract

The degradation of sulfamethoxazole (SMX) by a synthesized hierarchical magnetic zinc oxide based composite ZnO@g-C₃N₄ (FZG) was examined. Hierarchical FZG was synthesized by using Fe₃O₄ nanoparticle as the magnetic core and urea as the precursor for in situ growth of g-C₃N₄ on the surface of petal-like ZnO. The effect of catalyst dosage (0.4-0.8 g/L), solution pH (3-11) and airflow rate (0.5-2.5 L/min) on the SMX removal efficiency and the optimization of process was studied by response surface methodology (RSM) based on central composite design (CCD). The obtained RSM model with R² = 0.9896 showed a satisfactory correlation between the predicted values and experimental results of SMX removal. Under the optimum conditions, i.e. 0.65 g/L photocatalyst concentration, pH = 5.6 and airflow rate = 1.89 L/min, 90.4% SMX removal was achieved after 60 min reaction. The first-order kinetic rate constant for SMX removal by using FZG was 0.0384 min^-1 while the rate constant by commercial ZnO was 0.0165 min^-1. Moreover, under the optimum conditions, about 64% COD removal and 45% TOC removal and a considerable reduction in toxicity were observed. The analysis of generated intermediates during the photocatalytic degradation of SMX was conducted by LC-HR-MS/MS method and a degradation pathway was proposed.

Keywords: By-product; Hierarchical photocatalyst; Response surface methodology; Sulfamethoxazole; Toxicity.