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 (CO₂). The present study investigates a potential environmentally conscious solvent to capture and utilize CO₂ using waste concrete and seawater under reactor conditions. Although seawater's CO₂ soubility is low due to salinity, waste concrete raises seawater's pH and alkalinity, acting as a feedstock for CO₂ dissolution and offsetting the adverse effects of salinity. To evaluate the performance of the novel natural seawater-concrete solutions for CO₂ capture, time-dependent pH changes of solutions exposed to CO₂ were measured in a microchannel using fluorescence microscopy. The concentration of dissolved CO₂ 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 CO₂ dissolution coefficient from 530 to 835 μm²/s in seawater upon concrete addition. Electrolysis further enhanced the CO₂ 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.