Electrochemical CO2 mineralization for red mud treatment driven by hydrogen-cycled membrane electrolysis

Abstract

CO 2 mineralization as a promising CO 2 mitigation strategy can employ industrial alkaline solid wastes to achieve net emission reduction of atmospheric CO 2 . The red mud is a strong alkalinity waste residue produced from the aluminum industry by the Bayer process which has the potential for the industrial CO 2 large scale treatment. However, limited by complex components of red mud and harsh operating conditions, it is challenging to directly mineralize CO 2 using red mud to recover carbon and sodium resources and to produce mineralized products simultaneously with high economic value efficiently. Herein, we propose a novel electrochemical CO 2 mineralization strategy for red mud treatment driven by hydrogen-cycled membrane electrolysis, realizing mineralization of CO 2 efficiently and recovery of carbon and sodium resources with economic value. The system utilizes H 2 as the redox-active proton carrier to drive the cathode and anode to generate OH − and H + at low voltage, respectively. The H + plays as a neutralizer for the alkalinity of red mud and the OH − is used to mineralize CO 2 into generate high-purity NaHCO 3 product. We verify that the system can effectively recover carbon and sodium resources in red mud treatment process, which shows that the average electrolysis efficiency is 95.3% with high-purity (99.4%) NaHCO 3 product obtained. The low electrolysis voltage of 0.453 V is achieved at 10 mA·cm −2 in this system indicates a potential low energy consumption industrial process. Further, we successfully demonstrate that this process has the ability of direct efficient mineralization of flue gas CO 2 (15% volume) without extra capturing, being a novel potential strategy for carbon neutralization.