Investigating the Performance of UV/PS/Tio2nps and UV/PI/Tio2nps Processes on Paraquat Herbicide Degradation in Aqueous Media: Statistical Optimization, Kinetic Study, and Estimation of Electrical Energy Consumption

Abstract

Background: In this work, the performance of UV/PS/TiO2NPs and UV/PI/TiO2NPs as hybrid advanced oxidation processes for degradation of the herbicide paraquat in aqueous solution is studied.Results: The effects of several factors such as the UV irradiation, initial oxidant concentration, TiO2 nanoparticles dosage, and pH on the degradation efficiency are investigated. The process optimization is performed by the central composite design and the response surface methodology for 30 mg L-1 of the herbicide at 25 ˚C and 40 min. Based on the results, a degradation efficiency of 77 % and 90 % have been obtained for the UV/PS/TiO2NPs and UV/PI/TiO2NPs processes respectively, in the optimum conditions. The mineralization efficiency of the paraquat solution using UV/PS/TiO2NPs and UV/PI/TiO2NPs processes are about 32 % and 55%, respectively, after 40 min. The kinetic studies show that both processes follow a pseudo-first-order kinetic model, and the kinetic constants are 0.0299 min-1 for the PS process and 0.0604 min-1 for the PI process. The electrical energy consumption has been estimated to be about 481.60 kWh/m3 for the PS process and 238.41 kWh/m3 for the PI process.Conclusions: The degradation and mineralization efficiency of the paraquat solution using UV/PI/TiO2NPs process are more than UV/PS/TiO2NPs process in the optimum conditions after 40 min.