Exploring the potential of steel slag waste for carbon sequestration through mineral carbonation: A comparative study of blast-furnace slag and ladle slag

Abstract

Steel slag is a by-product of steelmaking which has emerged as a potential CO₂ sequestration material due to its high reactivity and abundance. This research investigates the use of steel slag waste for the direct capture of carbon from air and its storage through mineral carbonation. Two abundant wastes, blast-furnace slag (BFS) and ladle slag (LS), were tested for their carbon sequestration potential, and the effects of operational parameters such as reaction time between CO₂ and slag waste, temperature, liquid-solid ratio, and pressure on CO₂ sequestration were determined. Quantitative and qualitative results reveal that much higher CO₂ sequestration was achieved using LS compared to BFS after exposure to CO₂ for 1 day at room temperature. By increasing the exposure time to four days, levels of CO₂ sequestration increased gradually from 2.71% to 4.19% and 23.46%-28.21% for BFS and LS respectively. Increasing the temperature from 20 ± 2 °C to 90 ± 2 °C positively influenced CO₂ sequestration in BFS, resulting in an enhancement from 3.45% to 13.21%. However, the impact on LS was insignificant, with sequestration levels rising from 27.72% to 29.90%. Moreover, better CO₂ sequestration was observed for BFS than LS when the liquid-to-solid ratio increased from 3:1 to 4:1, whereupon the sequestration potential reached approximately 15% for BFS and 30% for LS at 90 ± 2 °C. Meanwhile, higher pressure reduced the sequestration potential of slag. The results of this study suggest that there is potential for scaling up the process to industrial applications and contributing to the reduction of CO₂ emissions in the steelmaking industry.

Keywords: Blast furnace slag; CO(2) sequestration; Ladle slag; Mineral carbonation; Steel slag waste.