来源：Science Direct
Fluoride in ionic rare earth ore leachate readily induces three-phase emulsification during rare earth solvent-extraction process, severely worsening separation efficiency and product quality. Conventional defluoridation of terminal high-concentration rare earth chloride (RECl3) liquor encounters serious technical bottlenecks: complex fluoride-bearing species (REFn(3-n)+, AlFn(3-n)+) hinder deep fluoride removal. Herein, we proposed a fluoride source-controlled strategy using a novel hydroxyl-rich zirconium-aluminum-phosphate composite (HZAP) for deep defluoridation of neutralized ionic rare earth ore leachate. HZAP was synthesized via co-precipitation coupled hydrothermal aging, featuring a large specific surface area (177.4 m2/g) and abundant surface hydroxyl groups. Under optimized conditions (initial F = 2.63 mg/L, HZAP dosage = 1.5 g/L, pH = 5.4, 298 K, 120 min), the residual fluorine concentration decreased to <0.5 mg/L, satisfying the fluoride threshold for industrial rare earth extraction. Kinetic and thermodynamic results indicated that fluoride adsorption onto HZAP followed the pseudo-second-order model, which was a spontaneous, endothermic and entropy-increasing chemisorption process with auxiliary electrostatic attraction. Spectroscopic characterizations and DFT calculations verified that surface hydroxyl groups served as dominant active sites for ligand exchange, forming Al–F and Zr–F bonds to achieve fluoride capture. After four adsorption-regeneration cycles, HZAP maintained ∼90% defluoridation capacity with negligible structural degradation, exhibiting outstanding recyclability. Practical tests using real neutralized industrial rare earth ores leachate further validated its engineering defluoridation capability. This work provides a promising material and source-controlled defluoridation strategy for green hydrometallurgy of ionic rare earth ores.v