Electrocatalytic degradation of diuron herbicide using three-dimensional carbon felt/β-PbO2 anode as a highly porous electrode: Influencing factors and degradation mechanisms

Traditional planar PbO2 anodes have been used extensively for the electrocatalytic degradation process. However, by using porous PbO2 anodes that have a three-dimensional architecture, the efficiency of the process can be significantly upgraded. In the current study, carbon felt (CF) with a highly porous structure and a conventional planar graphite sheet (G) were used as electrode substrate for PbO2 anodes. Both CF/beta-PbO2 and G/beta-PbO2 anodes were prepared by the anodic deposition method. The main properties of the electrodes were characterized by XRD, EDX-mapping, FESEM, and BET-BJH techniques. The electrocatalytic degradation of diuron using three-dimensional porous CF/beta-PbO2 anode was modeled and optimized by a rotatable central composite design. After optimizing the process, the ability of porous CF/beta-PbO2 and planar G/beta-PbO2 anodes to degrade and mineralize diuron was compared. The electrocatalytic degradation of the diuron was well described by a quadratic model (R-2 > 0.99). Under optimal conditions, the kinetics of diuron removal using CF/beta-PbO2 anode was 3 times faster than the G/beta-PbO2 anode. The energy consumed for the complete mineralization of diuron using CF/beta-PbO2 anode was 2077 kWh kg(-1) TOC. However, the G/beta-PbO2 anode removed only 65% of the TOC by consuming 54% more energy. The CF/beta-PbO2 had more stability (115 vs. 91 h), larger surface area (1.6287 vs. 0.8565 m(2) g(-1)), and higher oxygen evolution potential (1.89 vs. 1.84 V) compared to the G/beta-PbO2. In the proposed pathways for diuron degradation, the aromatic ring and groups of carbonyl, dimethyl urea, and amide were the main targets for HO center dot radical attacks. (C) 2021 Elsevier Ltd. All rights