Direct Air Capture Using Electrochemically Regenerated Anion Exchange Resins.

Direct air capture (DAC) aims to remove CO 2 directly from the atmosphere. In this study, we have demonstrated proof-of-concept of a DAC process combining CO 2 adsorption in a packed bed of amine-functionalized anion exchange resins (AERs) with a pH swing regeneration using an electrochemical cell (EC). The resin bed was regenerated using the alkaline solution produced in the cathodic compartment of the EC, while high purity CO 2 (>95%) was desorbed in the acidifying compartment. After regenerating the AERs, some alkaline solution remained on the surface of the resins and provided additional CO 2 capture capacity during adsorption. The highest CO 2 capture capacity measured was 1.76 mmol·g -1 dry resins. Moreover, as the whole process was operated at room temperature, the resins did not show any apparent degradation after 150 cycles of adsorption-desorption. Furthermore, when the relative humidity of the air source increased from 33 to 84%, the water loss of the process decreased by 63%, while CO 2 capture capacity fell 22%. Finally, although the pressure drop of the adsorption column (5 ± 1 kPa) and the energy consumption of the EC (537 ± 33 kJ·mol -1 at 20 mA·cm -2 ) are high, we have discussed the potential improvements toward a successful upscaling.