Indirect Carbonation by a Two-Step Leaching Process Using Ammonium Chloride and Acetic Acid

Indirect carbonation as an efficient CO2 sequestration strategy has received extensive attention in recent years. This study proposes a two-step leaching indirect carbonation process using NH4Cl and CH3COOH in order to combine the advantages of the two leaching agents to obtain a better experimental outcome. The experimental results show that NH4Cl has a high pH buffering capacity, which can increase the pH of the mixed leachate to an alkaline level. Among the 21 groups of mixed leachate, 17 were alkaline (pH > 7). The mixed leachate has a high Ca2+ ions carbonation rate under low CH3COOH concentration conditions, and the carbonation rate of steel slag with a particle size of < 38 mu m can reach 60% when the CH3COOH concentration is 0.1 M. SEM imaging showed that the CaCO3 formed by the reaction exists in a hexagonal calcite crystal form.