Advanced Cr(VI) removal from wastewater using migrating electric field-assisted electrocoagulation combined with capacitive deionization technology

The remediation of hexavalent chromium (Cr(VI)) in wastewater is paramount due to increasingly stringent environmental regulations governing the discharge of pollutants. This study developed an advanced capacitive deionization-assisted electrocoagulation (CDEC) system, which is enhanced wastewater Cr(VI) removal using migrating electric-field assisted electrocoagulation with a capacitive electrode. The capacitive electrode was explicitly incorporated into this hybrid system to capitalize on its adsorption and desorption capabilities and concentrate and eliminate Cr(VI). The CDEC reduced Cr(VI) effluent to 0.05 mg L⁻¹ at 1–20 mg L⁻¹ influent, below the Cr(VI) discharge standard for municipal wastewater treatment plants. The CDEC is a promising approach for removing Cr(VI), requiring only 0.0042–0.086 kWh m⁻³ at 1–20 mg L⁻¹ influent, 23.89–43.9 % less than the control when the CDEC and control achieved the same effluent. The CDEC incorporates capacitive adsorption electrodes (CAE) to facilitate electro-adsorption and electro-desorption phenomena during electrochemical treatment. This hybrid system has demonstrated excellent performance in high treatment efficiency, low sacrificial anode consumption, and low energy consumption. The CDEC can attain high Cr(VI) removal efficiencies through this synchronized electro-adsorption and desorption mechanism. The Cr(VI) removal mechanism of CDEC was found to involve four pathways: 1) Cr(VI) reduction to Cr(III) at the cathode; 2) Fe²⁺ produced at sacrificial anode slide reduces Cr(VI); 3) complexation of hydroxide precipitation with Cr(VI); 4) adsorption onto the CAE. This work provides an innovative and efficient approach for advanced Cr(VI) removal from wastewater via capacitive deionization with electrocoagulation.