Towards the Electrochemical Retention of CO2: Is it Worth it?

This work focuses on the use of NaOH produced cathodically by reduction of water to retain gaseous CO2 in a combined electrolyzer-absorber device. The process deals with two relevant environmental concerns: desalination and carbon sequestering, using only electricity and heat, which can be provided using green sources. Results demonstrate that technology is feasible, and the composition of the final product depends on the operation conditions applied. Removal rates of 130 mmol CO2/h were obtained at 7.5 A with coulombic efficiency in the removal of CO2 of 47.63 %. Efficiency in the production of chlorine, hydrogen and NaOH decreases at large current densities because of the promotion in the oxidation of water and the promoted transport of protons from the anodic to the cathodic compartment of the cell. Low current densities should be used to promote the formation of NaHCO3 and avoid scaling problems (formation of deposits of Na2CO3) in the spray column. The use of heated air to evaporate the product of the absorption column produces evaporated water with higher quality (in terms of lower conductivity) from the product of the absorption column.