Preparation of Pb/biochar composite as particle electrode for three-dimensional electrochemical oxidation of chemical oxygen demand from chemical wastewater

The use of three-dimensional (3D) electrochemical oxidation has become a popular method for treating water pollutants. In this study, the degradation of real wastewater discharged by the chemical industry was conducted using Pb loaded biochar (Pb/BC) as a particle electrode. The properties of Pb/BC were characterized by scanning electron microscopy, X-ray diffraction, energy-dispersive X-ray spectroscopy, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, and Brunauer–Emmett–Teller. The impact of various factors, including Pb loading, pH, dosage of Pb/BC, and working voltage, on chemical oxygen demand (COD) elimination were examined, and the best results were obtained on pH 7 and working voltage of 14 V, with 25 g/L Pb/BC (8% Pb loaded on BC) added in 3D reaction system. The degradation process was well fitted with the first-order kinetic. COD removal efficiency was 67.60% after 90 min reaction with only 6.21 kW·h/kg COD of energy consumption. The presence of tert-butanol had a significant impact on decreasing the efficiency of COD removal, suggesting that the hydroxyl radicals produced during the reaction were the primary means of degrading COD, rather than direct electro-oxidation. Toxic results indicated that the treated wastewater was less toxic than the original water. The use of Pb/BC may have practical applications in the treatment of actual chemical wastewater.