Efficient Leaching and Separation of Iron, Aluminum, and Calcium from Carbon-Rich Components in Coal Gasification Fine Slag Using Organic Acids

• • IDS-4Na achieves a single leaching yield of 41.2% for Fe3+ while suppressing Ca2+ and Al3+ to <4%, with a selectivity ratio of 10.73, enabling high-purity iron recovery from CGFS-H for downstream metal extraction. • • Tartaric acid co-leaches Fe3+ (38.7%) and Al3+ (33.5%) with Ca2+ yield below 5%, achieving a selectivity of 14.73 for Fe/Al over Ca, which is critical for separating iron and aluminum from calcium in complex slag matrices. • • Citric acid preferentially leaches Ca2+ with a single yield of 71.5%, but also extracts Fe3+ (35.2%) and Al3+ (39.1%), yielding a low Ca selectivity ratio of 0.96, indicating the need for stepwise processing to achieve efficient calcium separation. • • Sequential leaching with IDS-4Na, tartaric acid, and citric acid yields cumulative extractions of 79.8% Fe3+, 65.08% Al3+, and 78.6% Ca2+, demonstrating a green, scalable route for recovering valuable metals from coal gasification slag, which is essential for producing hydrotalcite materials and reducing waste.