Enabling Light-Driven CO<sub>2</sub> Removal from Seawater using Metastable Photoacids
Partha Saha, Jeremy R. Meeder, Siddhant Singh, Swamenathan Ramesh, Michael Nippe, David G. Kwabi
Abstract
The world’s oceans capture large amounts of atmospheric carbon dioxide (CO 2 ). Consequently, sustainable and scalable carbon removal from seawater could mitigate atmospheric CO 2 when coupled with subsequent sequestration. The pH-dependent speciation of CO 2 in aqueous media (CO 2 (aq), HCO 3 – (aq), and CO 3 2– (aq)) and the low solubility of CO 2 (aq) have previously motivated the utilization of pH swings to remove dissolved inorganic carbon (DIC) from aqueous and organic solutions. We show for the first time that light-driven DIC removal from seawater can be achieved in a two-compartment flow reactor utilizing metastable photoacids (PAs) to trigger pH swings across a membrane. Whereas some PAs have been previously reported to facilitate CO 2 ( g ) removal if dissolved and irradiated in bicarbonate solutions, our current work validates the feasibility of sustainable carbon removal from seawater without requiring “direct contact” between seawater and PAs. Furthermore, our findings support recent mechanistic investigations of the formation of CO 2 ( g ) from DIC by merocyanine-derived PAs.