Selective separation of Fe and Ga from Al-rich HNO3 leach liquor using sequential solvent extraction

Ga exhibits enrichment in coal-based solid waste, establishing it as a promising alternative source for Ga recovery. The HNO 3 pressure leaching process effectively achieves simultaneous leaching of Al and Ga while retaining most of the Fe in the residue. However, separating Ga from acidic solutions containing Fe and Al remains a persistent challenge in hydrometallurgy due to their similar physicochemical properties. Herein, a simplified and effective two-stage sequential solvent extraction process using acid phosphorus extractants (P507 and P204) for selective Ga recovery was proposed. Under optimized conditions, P507 removed 97.2 % of Fe from coal gangue HNO 3 leach liquor with limited co-extraction of Ga (10.1 %) and Al (5.7 %). Subsequent P204 extraction recovered 99.2 % Ga with only 9.1 % Al co-extraction from the Fe raffinate. Stripping with 2 mol·L –1 H 2 SO 4 yielded 88.0 % Ga recovery, with the extractants showing excellent regeneration and cycling performance. Mechanistic studies including FT-IR, UV-Vis, ESI-MS, and stoichiometric analysis confirmed coordination through both P = O and P–O–H groups, forming Fe(HA)A 3 and Ga(HL)L 3 complexes (A = P507; L = P204 ligands), respectively. This study presents a highly efficient approach for the separation of Fe/Ga/Al and Ga recovery from HNO 3 leach liquor, featuring exceptionally low acid depletion.