Effects of operating conditions on CO2 absorption and carbonation using steel-making slag leaching solution

Steel production poses dual environmental challenges: significant CO 2 emissions and the generation of steel-making slag (SS), a major solid waste. Meanwhile, the low value utilization of SS results in the loss of calcium (Ca) resources. Utilizing Ca-containing SS to mineralize and solidify CO 2 is expected to achieve dual benefits of carbon reduction and solid waste utilization. In this paper, the feasibility of SS CO 2 absorption was investigated using an indirect mineralization method. A leaching solution was prepared by dissolving SS with ammonium chloride (NH 4 Cl), which was then used for CO 2 absorption, with bubbling absorption as the primary carbonation method. The variation in outlet CO 2 concentration during carbonation was monitored to characterize the reaction behavior at different stages. The effects of CO 2 concentration, leaching solution pH, gas flow rate, and absorption configuration on CO 2 absorption behavior were systematically investigated. Among the tested bubbling configurations, the two-stage system exhibited the best overall performance, achieving a cumulative CO 2 uptake of 0.38 g CO 2 ·L⁻¹ of leaching solution. In addition, a spray-assisted carbonation method was explored, demonstrating enhanced gas–liquid contact characteristics and potential for further process development.