Comparasion of Photochemical Oxidation Process Efficiency Based on Hydrogen Peroxide and Persulfate for the Removal of Paraquat from Aqueous Solutions

Introduction and purpose: One of the most important factors in the contamination of aquatic ecosystems is agricultural pesticides. Paraquat is a water-soluble and non-selective herbicide, which has adverse health effects, such as respiratory distress and even death. This study aimed to evaluate the degradability of paraquat toxins using photochemical oxidation processes based on hydrogen peroxide (UV/HP) and persulfate (UV/NaPS/Fe2 +). Methods: This experimental study investigated the effects of pH variables, concentrations of UV/HP and UV/NaPS/Fe2+, as well as the initial concentration of the pollutant on paraquat toxicity removal in a laboratory scale using a batch reactor of one liter. Moreover, the concentration of the residual paraquat and the amount of organic carbon removal were measured using High Performance Liquid Chromatography equipped with a visible Ultraviolet (UV) detector at 259 nm and a Total Organic Carbon (TOC) meter.    Results: The UV/HP and UV/NaPS/Fe2 + processes were able to remove 87.75% and 92.31% paraquat, respectively, at 120 min under optimum conditions. In addition, the amount of TOC removal in the UV/HP and UV/NaPS/Fe2 + processes  were 77.29% and 82.16%, respectively. The results showed that the kinetics of the UV/HP and UV/NaPS/Fe2 + processes  followed the first-order reaction. Conclusion: The UV/NaPS/Fe2 + process was more effective than that of UV/HP regarding paraquat removal. As a result, the studied processes are proposed as effective, fast, and efficient methods to remove paraquat from aqueous solutions, which is economically feasible due to the low reaction time. The use of this process is also recommended as a complete refinement or pre-treatment process.