Electro-Fenton approach for highly efficient degradation of the herbicide 2,4-dichlorophenoxyacetic acid from agricultural wastewater: Process optimization, kinetic and mechanism

2,4-Dichlorophenoxyacetic acid (2,4-DPAA) as a commonly used herbicide in agricultural farms causes severe contamination of groundwater and surface water. Herein, a treatment process based on the electro-Fenton (EF) technique was developed for efficient removal of 2,4-DPAA from agricultural wastewater. Response surface methodology (RSM) was employed to optimize the operation conditions and modeling the developed process. The best removal efficiency of 99.2% was achieved at solution pH of 3, initial 2,4-DPAA concentration of 2.6 mg L-1, H2O2 dosage of 470 mL L-1, the current density of 3.5 mA cm(-2), and reaction time of 7.5 min, which is in good accordance with the predicted removal efficiency of 98.6% by the model. The developed process was applied successfully for removal of 2,4-DPAA from agricultural wastewater with the actual removal efficiency of 93.7%. The values of coefficients of determination (R-2), predicted R-2 and adjusted R-2 were found to be 0.9775, 0.9268, and 0.9690, respectively. Analysis of variance (ANOVA) was conducted to evaluate the competence of the developed model. The obtained high F-value of 114.14 and the very low P-value of <0.0001 confirm that the model is highly significant. The electrical energy consumption was found to be 0.058 kWh.m(-3). Employing the radical scavengers and the control experiments based on electrocoagulation and the Fenton process, the main mechanism for 2,4-DPAA degradation is revealed by the in-situ generation of hydroxyl radical throughout the EF treatment process. The kinetic of the developed model followed a pseudo-first-order reaction with a rate constant of 0.4746 min(-1). (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

An EF technique was developed for efficient removal of 2,4-DPAA from agricultural wastewater, achieving a removal efficiency of 93.7%. The model predicted removal efficiency of 98.6% closely matched the actual result, demonstrating the effectiveness of the developed process.