Enhanced electrocatalytic elimination of fenitrothion, trifluralin, and chlorothalonil from groundwater and industrial wastewater using modified Cu-PbO2 electrode

Abstract

In this study, fenitrothion (FTH), trifluralin (TRL), and chlorothalonil (CHT) pesticides were studied as simultaneous degradation candidates for the anodic oxidation (AO) process. Characterization experiments including FE-SEM, XRD, cyclic voltammetry, electrochemical impedance spectroscopy, linear polarization, and accelerated service lifetime test (ASLT) were performed to evaluate the effect of Sn@Sb, PbO2, and PbO2/Cu electrodes. The doping of Cu into PbO2 electrode played an important role in improving the electro-catalytic activity of the electrode and can further increase the •OH generation capacity. Simultaneous removal FTH, TRL, and CHT using the AO process was optimized by response surface methodology. Analysis of variance revealed that the R2 of removal efficiency for FTH, TRL, and CHT were 0.9848, 0.9791, and 0.9770, respectively. Moreover, the adjusted R2 for degradation of FTH, TRL, and CHT were 0.9822, 0.9756, and 0.9738, and the predicted R2 were 0.9770, 0.9694, and 0.9685, respectively. The complete removal efficiency for FTH, TRL, and CHT was achieved under the optimal condition including FTH concentration 8.0 mg L−1, TRL concentration 12.0 mg L−1, CHT concentration 16.0 mg L−1, pH 6.0, current density 6.0 mA cm−2, and oxidation time of 60 min. In the optimum condition COD removal efficiency and energy consumption were 74.3% and 4.4 kWh m−3 using PbO2/Cu electrode, respectively. The kinetic of FTH, TRL, and CHT degradation on Sn@Sb, PbO2, and PbO2/Cu electrodes best fitted on a pseudo-first-order kinetic model. The oxygen evolution overpotential was 1.914, 1.983, and 2.138 V vs. SCE for Sn@Sb, PbO2, and PbO2/Cu electrodes, respectively. The ASLT of PbO2/Cu electrode is 344 h, which is 2.3 and 4.2 times longer than that of PbO2 and Sn@Sb electrodes. The degradation mechanism was evaluated using GC–MS technique and a possible degradation pathway for the anodic oxidation of FTH, TRL, and CHT was proposed based on the identified intermediates. As a result, the AO technology using PbO2/Cu electrode could be considered a nice solution to the treatment of pesticides-polluted wastewater.