A sustainable temperature-swing process for CO2 capture and mineralization at below 100 °C using a recyclable chelating agent and bottom ash

Abstract

Industrial waste utilization for carbon dioxide (CO2) mineralization offers a highly promising approach to significantly reduce CO2 emissions; however, it faces the challenge of consumption of huge amounts of chemicals without their recovery. This study proposes an improved CO2 mineralization process that employs a highly recyclable solution of environmentally friendly chelating agent, N,N-Dicarboxymethyl glutamic acid (GLDA) enriched with NaHCO3 and involves the temperature swing-facilitated dissolution and carbonation of Ca-bearing industrial wastes under ambient pressure and low temperature (<100 °C). Using bottom ash collected from plastic incineration as a representative solid waste, this study emphasizes the significance of temperature control during the Ca extraction and carbonation processes. Ambient temperatures prove favorable for efficient Ca extraction from incinerator bottom ash, while a relatively higher temperature (95 °C) is recommended for subsequent Ca carbonation; the carbonation process was then self-promoted due to the pH increase from carbonation. Subsequently, the solution was efficiently regenerated after use for CO2 capture. Across five CO2 mineralization cycles using the same solution, a comparable CaCO3 generation efficiency was demonstrated, suggesting the high recyclability of the solvent and sustainability of this approach. Although heavy metal accumulation was observed in the extraction solution during cycling, it did not negatively affect the Ca extraction and heavy metal-free CaCO3 was successfully produced. Overall, the proposed CO2 mineralization process utilizing the recyclable GLDA solution has significant potential as a green technology crucial for the global pursuit of CO2 mitigation.