Efficient degradation of COD from coking wastewater by corncob biochar-modified particles using a three-dimensional electrode reactor

Abstract

Fe–Mn/BC particle electrodes with different loading ratios were prepared by a sol–gel method using corncob biochar (BC) as a carrier. The particle electrodes were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), Brunauer–Emmett–Teller (BET), X-ray diffraction (XRD) and cyclic voltammetry (CV). Using the chemical oxygen demand (COD) removal efficiency of coking wastewater as an indicator of electrocatalytic oxidation performance, the influencing factors of the electrocatalytic oxidation performance by a three-dimensional electrode system are discussed and the analysis of the degradation mechanism was carried out. The results show that the Fe–Mn particle electrodes with a load ratio of 1 : 1 obtained after carbonization at 500 °C for 3 h had a COD removal rate of 81.26% under the optimum conditions of pH 7, a current density of 25 mA cm⁻² and electrolysis time of 120 min. The three-dimensional electrode reactor (3DER) filled with Fe–Mn-modified BC particle electrodes showed superior performances. The three-dimensional fluorescence spectra results of the coking wastewater before and after treatment in the 3DER indicated that the refractory organics in the coking wastewater were degraded into degradable organic substances, and most of the soluble organic compounds were degraded and transformed. Moreover, the tert-butanol quenching experiment confirmed that the electrocatalytic process was mainly based on the indirect oxidation of hydroxyl radicals (˙OH) to achieve the removal of pollutants. This novel strategy realized the synergistic production of valuable corncob biochar particle electrodes and the remediation of pollutants with remarkable environmental and ecological benefits.