Solvent-Free CO2 Capture Using Membrane Capacitive Deionization

Capture of CO2, originating from both fossil fuels, such as coal combustion, and from renewables, such as biogas, appears to be one of the greatest technological challenges of this century. In this study, we show that membrane capacitive deionization (MCDI) can be used to capture CO2 as bicarbonate and carbonate ions produced from the reaction of CO2 with water. This novel approach allows capturing CO2 at room temperature and atmospheric pressure without the use of chemicals. In this process, the adsorption and desorption of bicarbonate ions from the deionized water solution drive the CO2(g) absorption-desorption from the gas phase. In this work, the effects of the current density and the CO2 partial pressure were studied. We found that between 55 and 75% of the electrical charge of the capacitive electrodes can be directly used to absorb CO2 gas. The energy requirement of such a system was found to be ≈40 kJ mol-1 at 15% CO2 and could be further improved by reducing the ohmic and non-ohmic energy losses of the MCDI cell.