Calcium carbonate synthesis from Kambara reactor desulphurization slag via indirect carbonation for CO 2 capture and utilization.

In this work, industrial Kambara reactor desulphurization slag (KR slag) was indirectly carbonated. The effects of leaching time, leaching temperature, leaching agent types, and leaching agent concentration on the leaching ratio of calcium from KR slag were investigated. Subsequently, precipitated calcium carbonate (PCC) was synthesized by bubbling CO ₂ gas (flow rate of 15 mL/min) into 400 mL leaching solutions at 40 °C for 120 min with magnetic stirring at 300 rpm. It is found that calcium in KR slag can be selectively extracted using a diluted solution of ammonium acetate (CH ₃ COONH ₄ ) or ammonium chloride (NH ₄ Cl), while ammonium sulfate ((NH ₄ ) ₂ SO ₄ ) solution is not suitable as leaching agent due to the formation of slightly soluble calcium sulfate (CaSO ₄ ). The leaching ratio of calcium is improved by extending the leaching time or increasing the leaching solvent concentration. However, leaching temperature has little effect on calcium extraction. After carbonating the NH ₄ Cl- and CH ₃ COONH ₄ -leachate for 120 min, calcite and vaterite type PCC with a purity of 99% is synthesized. Each gram of KR slag can produce 0.794 g and 0.803 g PCC using NH ₄ Cl and CH ₃ COONH ₄ leaching agents respectively. Calculations show that 349.6 kg CO ₂ is captured by per ton of KR slag. The CO ₂ capture capacity of KR slag is significantly higher compared with previously studied materials.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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