Using H2O2-Based Photochemical Oxidation (UV/ H2O2) in Eliminating Paraquat from Aqueous Solutions

About 40% of pesticide production in the world is related to herbicides. Herbicides are one of the major contaminants of aquatic ecosystems. Paraquat (PQ) is a noble, non-selective, and solvent-free herbicide in aqueous solutions. In this study, degradation of paraquat was investigated using the UV/H2O2 process.
In the present study, variables, including initial concentration of toxin, contact time, pH, and H2O2 concentration on paraquat removal in a laboratory scale were investigated. The concentration of the residual paraquat was determined using HPLC. The amount of mineralization under optimal conditions was measured by measuring the amount of TOC removal according to the standard method 5310- B.
The optimum removal efficiency of PQ by UV/H2O2 process was 87.75% with H2O2 concentration of 33 mmol/L, pH of 5, initial PQ concentration of 25 mg/L, and reaction time of 120 minutes. Moreover, 77.29% of the Total Organic Carbon (TOC) was removed under similar conditions. In addition, the data was found to follow the first-order kinetics.
Considering the growing use of UV radiation in water treatment processes and the considerable efficiency of UV/ H2O2 process in removing PQ, this method can be proposed for the elimination of PQ after performing cost-benefit analyses.
This research showed that according to purification goals and standards for wastewater treatment, UV/ H2O2 process can be used as a past or final treatment.