A novel technology of carbon dioxide adsorption and mineralization via seawater decalcification by bipolar membrane electrodialysis system with a crystallizer

Seawater carbon sequestration can not only reduce the greenhouse effect by carbon dioxide mineralization but also achieve seawater calcium removal. Generally, this process requires the addition alkaline reagents to make a high pH environment. This study developed a novel seawater carbon sequestration technology using a bipolar membrane electrodialysis system with a crystallizer. The results showed the new system had excellent synergistic effects. Water dissociation, CO2 adsorption and precipitation reactions between CO32− and seawater could be carried out in the system without the membrane contamination. With the electric-field, water dissociation occurred on the bipolar membrane and the alkalinity was used to enhance the absorption and ionization of CO2 in the chamber. Based on the ions selective mobility through the anionic membrane, weak base ions combined with seawater in the salt chamber. However, the cations in seawater, calcium and magnesium ions, could not pass through the anionic membrane, which prevented the pollution of the bipolar membrane. Meanwhile, the ion concentrations of CO32− was controlled and primary nucleation of CaCO3 could not occur in the salt chamber. The seeded crystallization in the crystallizer increased the reaction area and consumed the supersaturation degree of CaCO3. This study examined the effects of CO2 access mode of the membrane stack and the induced crystal seeds in the crystallizer on membrane fouling, seawater decalcification, carbon sequestration and energy consumption. This new system indicated the direction of bipolar membrane application in the adsorption and reactive crystallization of acid gas.