Study on REEs leached in phosphate concentrate with phosphoric acid

A new hydrometallurgical leaching process, which dissolves REES with phosphoric acid, was proposed and investigated. It studied the effects of H₃PO₄ concentration, temperature, reaction time, and liquid-solid ratio on REES leached. The results showed that an extraction of about 90% was achieved under the leaching conditions: 25% H₃PO₄, 65°C, liquid-solid ratio 10, and reaction time of 8 hours. SEM and XRD analysis indicated that no new reaction solid product was formed on the surface of leaching residue particles. The dissolution kinetics of REES with phosphoric acid solution was found to fit the shrinking core model. The kinetic study indicated that REES leached was controlled by the interfacial chemical reaction in the whole leach process. The apparent activation energy was 46.6 kJ/mol and a semi-empirical rate equation was obtained to describe the process.