Rapid Carbon Dioxide Capture and Short-Term Biocompatible Sequestration in Aquatic Environments by Monoethanolamine Scrubbing within Calcium Alginate Gel

Abstract

Alginate is a biopolymer extracted from the cell walls of algae, and can crosslink with divalent cations to form an insoluble hydrogel. In this paper, we develop a method to immobilize monoethanolamine, an amine CO2 scrubber, within calcium alginate gel. By mixing monoethanolamine into an alginate solution as the gel was formed, we suspended the compound in the gel, facilitating a means to capture carbon dioxide directly from aquatic environments into the gel, while tethering monoethanolamine and the products formed from CO2 capture to the gel. To delay the eventual diffusion of monoethanolamine out of the gel, we investigated (1) the effect of increasing alginate concentration and (2) the effect of additional alginate layers on the outward diffusion of dye placed in the center of the bead. Using ultraviolet-visible spectroscopy to quantify diffusion rates over time, we determined that increased alginate concentration paired with increased layering significantly decreased the rate of outward diffusion. Finally, we prepared beads using North Atlantic seawater as a solvent and compared the rate of dye leakage in seawater and distilled water to that in beads prepared in distilled water. Expectedly, we concluded that beads prepared with solvents isotonic to their environments would exhibit less leakage as well as greater mechanical stability, resisting swelling, bursting, or splitting behaviors.