Efficacious Degradation of 2,4-Dichlorophenoxyacetic Acid by UV–H₂O₂ Advanced Oxidation and Optimization of Process Parameters Using Response Surface Methodology

Abstract

The concentration of persistent organic compounds, including pesticides, in aquatic environments is gradually increasing due to industrial discharge and uncontrolled runoff from agricultural fields. The advanced oxidation process is considered the most effective treatment method for the mineralization of persistent compounds. This research focused on the degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) herbicide by a homogeneous process involving ultraviolet irradiation and H2O2 (UV–H2O2) and utilized response surface methodology (RSM) to analyzed influences of key factors involved in processes like 2,4-D concentration, H2O2 dose, pH, and nitrate amount in wastewater. Results showed that 90% of the 2,4-D herbicide was degraded within 5 min of UV-C radiation (253.7 nm wavelength) corresponding to the peroxide dose of 2 mol H2O2/mol 2,4-D at pH 5 and a nitrate concentration of 0.25 mM. A polynomial quadratic equation was developed to envisage both time- and fluence-based rate constants. All process parameters were found to significantly affect the degradation of the herbicide. Results indicated that an increase in initial 2,4-D and nitrate concentration in solution decreases the 2,4-D degradation rate. Higher H2O2 dosages and pH levels indicated an intensification in the rate constant up to an optimum value. Further, an increase in H2O2 dosage and pH resulted in a decrease in degradation rate. Further, the optimum conditions for 2,4-D degradation by the UV–H2O2 process were estimated. The findings of the present work will help to design the treatment process in real field conditions with variable water matrices.