Indirect CO2 mineral sequestration that involves two separate steps,with acetic acid as the recycling medium,was limited by a crystallization conversion of only 20% in the second gas-liquid reactive crystallization step.In this paper,the second carbonation step was greatly improved by coupling reactive crystallization and solvent extraction with the introduction of an organic solvent,tributyl phosphate(TBP),to the process.The effect of the initial concentration of calcium acetate in the aqueous solution on the crystallization conversion was studied experimentally.The obtained calcium conversion was above 40%,which was one time higher than that reported in the literature.Based on the mechanism discussion and thermodynamic equilibrium calculation analysis,it can be concluded that adding TBP to the step can consume the produced acetic acid,and it is in favor of the precipitation of calcium carbonate.While the challenge presented by the strong interaction between calcium ions and acetate ions for further improving crystallization conversion cannot be solved only by the addition of TBP.
