Gallium recovery from red mud: Integration of solvent extraction and siderophore assisted technologies.

Gallium (Ga) recovery from the red mud, though important has never been successful due to several technical and economic reasons such as contaminant interference and the high cost of membranes due to their faster saturation resulting in the clogging of membranes with contaminants. This study demonstrated the recovery of Ga by a combination of HCl-based leaching, Fe/Al/Ti separation, and recovery of Ga using Cyphos IL 104-based solvent extraction and complexation of Ga with desferrioxamine B as a proof-of-principle of the GaLIophore technology. The main leaching parameters such as concentrations of acids, time and temperature of the reaction, and solid-to-liquid ratio have been systematically investigated. The optimal leaching conditions were determined as 4 mol/L HCl, 2 h time, 80 °C temperature, and solid-to-liquid ratio 1:20 (g/mL) attaining a more than 90% leaching of Ga. Subsequently, more than 99% Ga was extracted from the leachate using 0.05 mol/L Cyphos IL 104 at A:O ratio 1 and stripped by 0.01 mol/L HSO at O:A ratio 1 from the organic phase. Desferrioxamine B (DFOB) demonstrated selectivity by complexing with more than 90% Ga in a stripped solution. The interaction between extractable species of Ga and Cyphos IL 104 was studied by Density Functional Theory (DFT) calculations and infrared spectroscopy. The whole process demonstrated the recovery of Ga by more than 80% present in the red mud. Further, the preliminary economic analysis suggests that the process can be profitable when Fe, Al, Sc, and Ga are recovered at a minimum rate of 50, 50, 75, and 75%.