Hybridized advanced oxidation processes involving UV/H2O2/S2O 8 2- for photooxidative removal of p-nitrophenol in an annular continuous-flow photoreactor

Abstract

In this paper, photooxidative removal of p-nitrophenol (PNP) as a model organic pollutant was investigated in the presence of UV/inorganic oxidants system in an annular continuous-flow photoreactor. The aim of this study was to evaluate the photooxidative efficiency of hybrid oxidant system including persulfate (UV/H2O2/S2O 8 2- ) and hydrogen peroxide (H2O2), under UV–C light irradiation. The effects of operational variables including UV/H2O2/S2O 8 2- and H2O2 concentrations, the initial PNP concentration, and residence time on the removal efficiency of UV/H2O2/H2O2/S2O 8 2- system were studied. It was found that the operational variables affected the removal efficiency of UV/H2O2/H2O2/S2O 8 2- system. Operating conditions were optimized using response surface methodology (RSM). Simulation approach showed that the predicted values of removal efficiency are in good agreement with the experimental results with a correlation coefficient (R 2) of 0.95. Optimization results showed that the maximum degree of removal (98%) was achieved by using the UV/H2O2/H2O2/S2O 8 2- system under the following operation conditions: concentration of H2O2 = 10 mmol/L, concentration of UV/H2O2/S2O 8 2- = 10 mmol/L, initial concentration of PNP = 35 mg/L, and residence time = 8 min. The obtained results clearly demonstrated that RSM is one of the useful and cost-effective methods for modeling and optimizing the efficiency of UV/H2O2/UV/H2O2/S2O 8 2- system.