Carbon Dioxide-Mediated Desalination

Conventional desalination membrane technologies, although offer portable drinking water, are still energy-intensive processes. This paper proposes a potentially new approach for performing water desalination and purification by utilizing the reversible interaction of carbon dioxide (CO₂) with nucleophilic amines─reminiscent of the Solvay process. Based on our model studies with small molecules, CO₂-responsive amphiphilic insoluble diamines were prepared, characterized, and applied in the formation of soda and ammonium chloride upon exposure to ambient CO₂ (1 atm), thus removing chloride ions from model and real seawater. This ion-exchange process and separation of chloride from the aqueous phase are spontaneous in the presence of CO₂ without the need for external energy sources. We demonstrate a flow system to envisage energy-efficient CO₂-mediated desalination and simultaneous carbon capture and sequestration.