Coal gasification wastewater (CGW) contains a large amount of toxic pollutants , which seriously affects the subsequent biochemical treatment. In order to investigate the efficiency of electrocatalytic oxidation on pretreatment of CGW, lead dioxide electrodes doped with PEG and Bi were successfully prepared. Scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction were comprehensively used to characterize the lead dioxide electrode and the electrochemical performance was also tested by linear sweep voltammetry curve, cyclic voltammetry curve and AC impedance. Biodegradability and toxicity of CGW were evaluated by dehydrogenase activity and acute toxicity, respectively. Results showed that the doping of PEG and Bi significantly improved the electrochemical performance and catalytic oxidation performance of lead dioxide electrodes. The degradation rate of phenol by Sn–Sb/PbO 2 (PEG + Bi) electrode were 1.57 times of that by pure lead dioxide electrode. The removal of TOC and total phenols were 53.2% and 82.7%, respectively at 120 min under 40 mA cm −2 by Sn–Sb/PbO 2 (PEG + Bi) electrode. The changes of biodegradability, biological toxicity and by-products were analyzed. Furthermore, 3,5-dimethylphenol was used as characteristic pollutant to study the degradation mechanism of phenolic pollutants in electrocatalytic system. According to the intermediate products detected by GC-MS, possible degradation pathways in electrocatalytic system were proposed.
Qiuyang Yu,Ziyi Jiang,Jinlong Yin,Shengli Chen,Xiaohong Hu
Because of its metal-like conductivity, excellent catalytic activity, and acid resistance, lead dioxide (PbO2) is the most used electrocatalyst for the practical electrochemical ozone production (EOP) technique. Introducing fluorine (F) into PbO2 electrodes or electrolytes can significantly improve EOP activity. However, there is still lack of valid evidence on understanding the role of doping F in the PbO2 electrode. In this work, we report a comprehensive study on the effect of F on EOP activity on electrochemically prepared PbO2 electrodes. F doping suppresses the side reaction of dioxygen (O2) evolution by inhibiting the formation of an α phase impurity of PbO2 electrodes. The more hydrophobic surfaces by doping F promote O2 adsorption as evidenced by low-temperature O2-temperature-programmed desorption experiments and thus are more favorable for ozone (O3) generation. The in situ isotope labeling oxygen (18O2) experiment proves that at room temperature, O2 can adsorb and dissociate on the operando PbO2 electrode surface and participate in the formation of O3 molecules. This work provides a comprehensive understanding of doping F for enhanced EOP.
In this study, La and Ce doped PbO2 electrodes were prepared and the characteristic of the electrodes were discussed with the help of structure analysis. The catalytic effects of the doped electrodes were explored through the degradation of para-aminophenol wastewater. The results showed that the para-aminophenol removal was 96.96%, 89.34%, and 77.55% after 180 min treatment with Ce-PbO2, La-PbO2, and PbO2, respectively. The para-aminophenol enhanced degradation mechanism was discussed with rare earth element doping electrodes and a kinetic model was established based on radical reactions mechanism with genetic algorithm (GA) calculation. The reaction constants of these electrodes were calculated and the results showed that the reaction constant of Ce-PbO2 electrode was the highest, which indicated that Ce-PbO2 electrode could have a better treatment effect. The EE/O was used as the index of energy consumption efficiency and the results were calculated and compared. This paper could provide basic data and technique reference of the prediction the oxidation reaction process of different electrodes for the electrochemical oxidation application in wastewater treatment.
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