CO2 sequestration and recovery of high-purity CaCO3 from bottom ash of masson pine combustion using a multifunctional reagent—amino acid

Abstract

The indirect pH-swing process is a potential approach to achieving a waste-to-resource supply chain by integrating mineral carbonation, element recovery, and valuable material production. However, the extensive consumption of various reagents made this process very complex and economically unviable. In this study, an all-in-one strategy using amino acids as multifunctional reagents for CO2 mineralization and CaCO3 production from biomass ash was proposed. The technical feasibility and process mechanism of this process were investigated at key operating parameters, including amino acid types, amino acid concentrations, and solid to liquid ratio. Results show that the biomass ash used in this study contained several active Ca-bearing phases, including portlandite (Ca(OH)2), lime (CaO), and composite oxide (Ca2SiO4). Selective preparation of vaterite from this biomass ash associated with promising Ca utilization efficiency was realized under ambient temperature and pressure. Amino acids functioned as proton donors, pH buffers, and chelating ligands during the Ca2+ leaching and as proton acceptors in the carbonation. About 19.9% of the active Ca-bearing phases were dissolved by glycine, and 76.8% of the leached Ca2+ was precipitated as vaterite CaCO3 under the optimal conditions of 2.0 mol/L glycine and 300 g/L biomass ash concentration. In addition, metastable vaterite CaCO3 products were obtained from the leaching and mineralization of biomass ash by three amino acids, including arginine, glycine, and L-alanine. The thermogravimetric results revealed that by incorporating the CaCO3 crystals, these amino acids stabilized vaterite and prevented vaterite from transforming to calcite.