Single-step, low temperature and integrated CO2 capture and conversion using sodium glycinate to produce calcium carbonate

Our unabated reliance on carbonaceous fuel sources and the rising concentration of atmospheric CO2 motivate the design of integrated thermodynamically downhill CO2 capture and conversion pathways. Carbon mineralization which involves converting CO2 to inorganic carbonates is a representative example. In this study, we investigate the integrated CO2 capture and conversion to produce calcium carbonate with CaO and CaSiO3 as the precursors. To overcome the rate limiting step of CO2 hydration, sodium glycinate is used for CO2 capture. Bicarbonate ions resulting from CO2 capture accelerate carbon mineralization. Carbon mineralization behavior in coupled capture and conversion processes is sensitive to the concentration of Na-glycinate, temperature, and reaction time. In this single step CO2 capture and mineralization pathway, highest conversions of CaO and CaSiO3 were achieved in 1.0 M Na-glycinate at 75 degrees C and with a reaction time of 3 h in a system comprising 15 wt% solid and at a stirring rate of 300 rpm. Extents of carbon mineralization with CaO and CaSiO3 are 94.2% and 31.0%, respectively. These data suggest that Na-glycinate undergoes multiple CO2 capture and regeneration cycles in the aqueous phase facilitating greater availability of aqueous carbon species for carbonate precipitation. Calcite is the dominant crystalline phase with CaO as the precursor, while aragonite, calcite and vaterite are present in materials with CaSiO3 as the precursor. These results demonstrate the effectiveness of Na-glycinate as a CO2 capture agent for integrated capture and mineralization with inherent regeneration in the aqueous phase.