CO2 mineralization of double decomposition suspension of Ca-leached wollastonite solutions

Abstract

Present study discusses the viability of relatively simple CO2 mineralization as a possible technology for carbon capture, utilization, and storage representing the detailed performances of the process. CaCO3 is precipitated as a CO2 fixed material in the process by carbonation of a double decomposition suspension, in which Ca(OH)2 is precipitated by adding NaOH into a leachate of wollastonite (CaSiO3) with a 0.46 M acetic acid solution. The leaching efficiency of Ca from CaSiO3 is 42.1% and the precipitates were produced by the double decomposition at a ratio of 0.51 g Ca(OH)2/g NaOH. In the carbonation, the CO2 fixing sources in double decomposition suspension are excessive OH–, precipitated and aqueous Ca(OH)2, free Ca2+, Na+, and physical absorption. More CO2 is fixed with increasing NaOH input and the CO2 is fixed at an average ratio of 0.80 g CO2/g NaOH, which is 27% less than the theoretical ratio of 1.10 g CO2/g NaOH. The difference is attributed to loss of NaOH in the neutralization of the remaining acetic acid after leaching and the increase of pH for carbonation. However, the process permanently fixes CO2 by producing CaCO3 as a precipitate (0.40 g CO2/g wollastonite), even though NaOH is used in the carbonation.