Dual-activated biochar with a multichannel structure enhanced electrosorption capacity of capacitive deionization for sulfate removal from mining wastewater

Electrode material is the key factor for improving the electrochemical performance of capacitive deionization. In this study, a multichannel electrode material derived from soybean straw was prepared by pyrolytic carbonization and dual-activation, characterized, and used as an electrode material in capacitive deionization (CDI) cells to remove sulfate. The results showed that the sulfate adsorption capacity of dual-activated CA-NPSSC-1 of 17.16 mg/g was higher than that of pristine SSC (3.28 mg/g) due to its larger specific surface area, suitable pore structure, superior conductivity, and larger specific capacitance. The electrosorption mechanism of CA-NPSSC-1 electrode included EDL ion storage and pseudocapacitance storage. The EDL contribution and pseudocapacitance contribution were 72.06 % and 27.94 %, respectively, at a scan rate of 5 mV/s. Actual wastewater experiments have shown that the sulfate concentration in mining wastewater was reduced to 158.85 mg/L after recycling treatment, which meets the relevant standards. This work provides new ideas and methods for the treatment of high-salinity mining wastewater.