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

CO2 mineralization as a promising CO2 mitigation strategy can employ industrial alkaline solid wastes to achieve net emission reduction of atmospheric CO2. 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 CO2 large scale treatment. However, limited by complex components of red mud and harsh operating conditions, it is challenging to directly mineralize CO2 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 CO2 mineralization strategy for red mud treatment driven by hydrogen-cycled membrane electrolysis, realizing mineralization of CO2 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 CO2 into generate high-purity NaHCO3 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%) NaHCO3 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 CO2 (15% volume) without extra capturing, being a novel potential strategy for carbon neutralization. (C) 2022 The Chemical Industry and Engineering Society of China, and Chemical Industry Press Co., Ltd. All rights reserved.

Automated summary

This study proposes a novel electrochemical CO2 mineralization strategy for red mud treatment, driven by hydrogen-cycled membrane electrolysis, to efficiently mineralize CO2 and recover carbon and sodium resources while producing mineralized products with economic value. The system effectively recovers carbon and sodium resources in the red mud treatment process, with an average electrolysis efficiency of 95.3% and high-purity (99.4%) NaHCO3 product. It also demonstrates the ability to directly and efficiently mineralize flue gas CO2 without the need for additional capturing, presenting a potential strategy for carbon neutralization.