Direct Air Capture Using Electrochemically Regenerated Anion Exchange Resins.

Direct air capture (DAC) aims to remove CO directly from the atmosphere. In this study, we have demonstrated proof-of-concept of a DAC process combining CO 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 (>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 capture capacity during adsorption. The highest CO capture capacity measured was 1.76 mmol·g 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 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 at 20 mA·cm) are high, we have discussed the potential improvements toward a successful upscaling.