Study on the degradation performance of coking wastewater using an in-situ enhanced Fe2+/Fe3+ cycle dual-cathode Electro-Fenton system

Abstract

Coking wastewater, characterized by its complex composition, high pollutant concentration, and poor biodegradability, poses a significant challenge for wastewater treatment. In this study, a chitosan-based mesoporous carbon (CPC) and microporous carbon (ZPC) dual-cathode Electro-Fenton system was developed to enhance the in-situ Fe2+/Fe3+ cycle efficiency for the degradation of coking wastewater. The optimal preparation conditions for both electrodes were investigated, as well as the primary factors affecting the degradation performance of the dual-cathode Electro-Fenton system. When the functional carbon loading was 17.5 mg/cm2 and a current of 600 mA was applied, the CPC electrode produced 842 mg/L of H2O2 within 30 min, and the Fe2+/Fe3+ cycle efficiency of the ZPC electrode reached 85.23 %. The initial pH and current intensity had the most significant impact on the degradation efficiency of coking wastewater, achieving a COD degradation rate of 78 % at an initial pH of 3.5 and a current intensity of 600 mA. GC-MS analysis indicated that under 600 mA, nitrogen-containing organics, ethers, and alcohols in the coking wastewater were completely removed. The degradation of simulated wastewater showed that the presence of oxygen-containing compounds inhibited the degradation of nitrogen-containing organics. However, the dual-cathode system experienced significant electrode wear, with reduced hydrophobicity and agglomeration of Fe3+ on the electrode surface impacting its cyclic stability.