Towards green carbon capture and storage using waste concrete based seawater: A microfluidic analysis.

Carbon capture and utilization technology is the research stream dedicated to mitigating the pressing effect of rising atmospheric carbon dioxide (CO). The present study investigates a potential environmentally conscious solvent to capture and utilize CO using waste concrete and seawater under reactor conditions. Although seawater's CO soubility is low due to salinity, waste concrete raises seawater's pH and alkalinity, acting as a feedstock for CO dissolution and offsetting the adverse effects of salinity. To evaluate the performance of the novel natural seawater-concrete solutions for CO capture, time-dependent pH changes of solutions exposed to CO were measured in a microchannel using fluorescence microscopy. The concentration of dissolved CO in the solution was derived from pH change, revealing a 4-fold increase in the total dissolved carbon from 0.034 to 0.13 M and a 57.54% increase in the CO dissolution coefficient from 530 to 835 μm/s in seawater upon concrete addition. Electrolysis further enhanced the CO capture capacity of the seawater-concrete solution by increasing the pH, enabling the solid precipitation of carbonate minerals. Raman spectroscopy and scanning electron microscopy showed that electrolysis-driven precipitates are mainly amorphous calcium carbonates, useful building blocks for seashells and coral reefs.