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

Indirect carbonation as an efficient CO 2 sequestration strategy has received extensive attention in recent years. This study proposes a two-step leaching indirect carbonation process using NH 4 Cl and CH 3 COOH in order to combine the advantages of the two leaching agents to obtain a better experimental outcome. The experimental results show that NH 4 Cl 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 Ca 2+ ions carbonation rate under low CH 3 COOH concentration conditions, and the carbonation rate of steel slag with a particle size of < 38 μm can reach 60% when the CH 3 COOH concentration is 0.1 M. SEM imaging showed that the CaCO 3 formed by the reaction exists in a hexagonal calcite crystal form.