Closed‐Loop Synthesis of High‐Purity FePO₄ from Red Mud: A Sustainable Route to Battery Materials

Red mud (RM), an iron‐rich industrial residue generated from alumina refining, poses significant environmental challenges while offering untapped potential for value‐added utilization. This study presents a closed‐loop hydrometallurgical strategy for converting RM into battery‐grade FePO 4 through a process‐optimized leaching–precipitation route. Iron was selectively extracted using a synergistic HCl–H 3 PO 4 acid system under optimized conditions (pH ∼ 1.8, 70 °C, L/S = 7:1), achieving over 80% recovery. Controlled precipitation yielded FePO 4 ·2H 2 O with a purity exceeding 99.5% and a near‐stoichiometric Fe/P molar ratio of ∼0.995. Subsequent thermal treatment and secondary purification jointly enhanced the purity of the final anhydrous FePO 4 product, yielding a phase‐pure material that meets industrial specifications. Multi‐technique characterizations including XRD, SEM‐EDS, TEM, and XPS confirmed the formation of phase‐pure FePO 4 with well‐defined structure and chemical state. This work highlights a scalable and environmentally responsible route for RM valorization, contributing to the sustainable production of energy materials and advancing circular economy practices in metallurgical industries.