Enhancement of electricity generation in CO2 mineralization cell by using sodium sulfate as the reaction medium

CO2 mineralization is a promising option for mitigating CO2 emissions because it is thermodynamically favorable. Recently, we developed a new CO2 mineralization cell (CMC) that mineralizes CO2 with Ca(OH)2 in the presence of NaCl to generate electricity and produce NaHCO3. In order to simplify the cell structure, N2SO4 was used as the reaction medium instead of NaCl, which lowered the Ca2+ concentration in the anolyte chamber. The two layers of membrane separator inside the cell were replaced with a mono-layer separator, which significantly reduced the electronic inner-resistance due to the improvement of mass transfer. With Na2SO4 being used as the reaction medium, Ca2+ reacted with SO42− and formed a CaSO4 precipitate outside of the cell, which increased the pH of the feed stream in the anolyte chamber. As a result, the open circuit voltage (OCV) of the cell increased from 0.452 V to 0.552 V, and the maximum power density increased from 5.5 W/m2 to 34.5 W/m2. Experiments were also conducted to investigate the ability of the newly designed CO2 mineralization cell to generate electricity and produce chemicals. Based on the experimental results, it was estimated that mineralizing a metric ton of CO2 could produce 1.9 t of 99.4% purity sodium bicarbonate, generate 137.3 kW h of electricity, and consume 1.23 t of carbide slag.