Degradation of diclofenac sodium using UV/biogenic selenium nanoparticles/H2O2: Optimization of process parameters

Abstract

The resistance of diclofenac (DCF), one of the most popular nonsteroidal anti-inflammatory drugs, to biodegradation processes and its abundance in the aquatic environment made it an environmental concern. Degradation by ultraviolet (UV) irradiation in the presence of various catalysts has possibility to eliminate DCF from water resources. In the present study, optimization of DCF degradation under UV light irradiation using biogenic selenium nanoparticles (Se NPs) in the presence of H2O2 (assisted by central composite design) in a photoreactor followed by identification of the produced metabolites (using GC-MS (EI) technique) was evaluated. To assess the influence of parameters on the UV/Se NPs/H2O2-assisted degradation efficiency of DCF, four main factors including light intensity (W/m2), Se NPs concentration (μg/mL), pH, and H2O2 concentration (mM) were chosen. Predicted values of degradation efficiency were found to be in good agreement with experimental values (Pre-R2 = 0.9982 and Adj-R2 = 0.9953). Optimization results showed that maximum degradation efficiency (97.43%) was achieved at the optimum conditions including Se NPs concentration of 32 μg/mL, UV light intensity of 30 W/m2, pH 7.5, and H2O2 concentration of 0.05 mM. 1-(2, 6-dichlorophenyl)-2-indolinone was found to be the main product among several peaks in the GC-MS chromatogram of the DCF treated sample.