Study on CO₂ Adsorption Performance of High-Calcium-Based Materials Originating from Modified Steel Slag

Steel slag is a prospective CO₂ capture material due to its substantial yield and calcium-rich mineral content. Numerous scholars have researched methods to enhance CO₂ adsorption capabilities, including fine-tuning adsorption process parameters and modifying the steel slag. However, the limited presence of active CaO within the slag constrains its carbonation rate. This study utilized converter steel slag as a raw material and employed a ‘melting-leaching-precipitation’ approach to produce a high-calcium-based material with enhanced CaO activity. After investigating the impact of steel slag particle size, solid–liquid ratio, leaching temperature, and precipitation pH on CaO recovery potential, a physicochemical analysis of the high-calcium-based material was conducted. The findings revealed that leaching temperature, solid–liquid ratio, and precipitation pH significantly affect Ca²⁺ leaching effectiveness, while steel slag particle size had a marginal effect on Ca²⁺ leaching. XRF analysis indicated that the highest CaO content in the high-calcium-based material reached 58.6%, marking a 22% increase compared to the original steel slag, with a maximum CaO recovery potential of 97.6%. XRD analysis demonstrated a substantial structural transformation from phases like C₂S and C₂F in the original steel slag to CaO, Fe₂O₃, Fe₃O₄, and CaF₂ post-modification. In an atmosphere of CO₂ and water vapor, a maximum CO₂ uptake of 10.1 wt% under normal pressure corresponds to 29 wt% of CO₂ uptake per unit mass of CaO. This research serves as a reference for the valorization of steel slag and aids steel industry efforts to mitigate CO₂ emissions.