Recovery of La from Red Mud Through Roasting, Water Leaching, and Subsequent Adsorption Processes

Abstract

Rare earth elements (REEs) are critical raw materials due to their rapidly expanding applications. Red mud, a by-product of aluminum production via the Bayer process, represents a promising secondary source of REEs, particularly lanthanum (La). This study investigates the recovery of La from red mud using an integrated sulfating-roasting-water leaching (SRWL) process followed by adsorption. Mineralogical and chemical analyses confirmed that REEs were dispersed within the matrix rather than concentrated in a separate mineral phase. Water leaching studies of treated (sulfation-roasting) red mud at room temperature showed that leaching time was the dominant parameter, and up to 90% REE recovery could be achieved after 96 h. In adsorption studies with leaching solutions obtained under optimum conditions, a commercial ion exchange resin (Lewatit MonoPlus SP112) and bio-based microcapsules (chabazite and chitosan) were evaluated for La removal. The effects of adsorbent dosage, pH, temperature, and contact time were systematically investigated. The results show that the commercial resin provides rapid and almost complete La removal, while the microcapsules exhibit slower kinetics due to their heterogeneous structure. Overall, the integrated SRWL-adsorption approach provides an effective way to enrich REEs and recover La from red mud, highlighting the potential for the utilization of industrial wastes.