Excessive fluoride and complex Al-F complex-ions severely impede the efficient extraction of rare earth elements (REEs) from rare earth chloride (RECl3) solution. Herein, hydrated calcium chloroaluminate (Ca2Al(OH)6Cl·2H2O) was prepared via a facile neutralization precipitation method and applied as a defluoridant to remove fluoride and aluminum to address the challenges in RECl3 solution. Under the optimized conditions (initial pH=2.0, 15 g/L dosage, 2 hours), the F concentration was reduced to 15.3 mg/L, achieving a defluoridation yield of 96.4% and a dealumination yield of 85.4% by using Ca2Al(OH)6Cl·2H2O. X-ray diffraction (XRD), Fourier transform infrared spectrometer (FTIR) and X-ray photoelectron spectroscopy (XPS) analyses reveal that the defluoridation mechanism primarily involves in-situ hydrolysis coprecipitation of Al-F complex-ions. Based on the study of reaction kinetics, the defluoridation rate equation was -d[F]/dt=7.389exp(-2.96/RT)CF00.916CCA0.972. The activation energy of the hydrolysis coprecipitation defluoridation was 2.96 kJ/mol, indicating a relatively rapid reaction rate. This work provides an effective strategy for the simultaneous removal of fluoride and aluminum, eliminating their hazards in REEs extraction and facilitating the recovery of aluminum resources.

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