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

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. [ABSTRACT FROM AUTHOR]