Surfactant-Enhanced Leaching of Gallium from Red Mud Waste: Toward a Sustainable and Economically Viable Extraction Process

Gallium (Ga) is a critical metal used in semiconductors, LEDs, and photovoltaic technologies, yet its recovery remains limited due to low natural abundance and dependence on bauxite processing residues. This study investigates the surfactant-assisted leaching of gallium from red mud using sulfuric acid (H 2 SO 4 ) and cetyltrimethylammonium bromide (CTAB) as a cationic surfactant to enhance metal recovery efficiency. The influence of CTAB dosage, temperature, and leaching time on gallium extraction was systematically examined under controlled conditions. The results demonstrate that the optimal CTAB dosage (0.1 g) increases Ga recovery from 62.7% (without surfactant) to 82.6%, attributed to improved interfacial contact and reduced particle agglomeration. Kinetic analysis based on the shrinking core model revealed a mixed-control mechanism involving both diffusion and surface chemical reactions, with apparent activation energies of 47.79 kJ mol −1 (non-surfactant) and 79.25 kJ mol −1 (low-surfactant) systems. Characterization of residues using XRD, SEM–EDS, and XRF confirmed partial dissolution of Fe-bearing phases and the persistence of quartz as the dominant inert component. An economic evaluation indicated that surfactant-assisted leaching reduced overall operating costs by approximately 9%. These findings highlight the potential of surfactant-assisted acid leaching as a promising and economically viable route for sustainable gallium recovery from red mud waste.