Thermal phase transformation behavior of florencite and implications on the leaching recovery of rare earth elements (REEs)

Florencite-(Ce) was synthesized to investigate its thermal phase transformation behavior. The XRD results showed that florencite-(Ce) started to dehydroxylate in the temperature range of 400–500 °C, and the crystal structure was decomposed at 600–700 °C, while further elevating the calcination temperature to over 900 °C resulted in the recrystallization of CePO₄. TGA-DTA showed that the complete decomposition and the recrystallization occurred at around 677 °C and 971 °C, respectively. Acid leaching tests were performed on the materials to investigate the effect of calcination on the Ce recovery. It was found that the gradual decomposition of florencite resulted in the increase in the solubility of Ce. To reveal the potential effects of kaolinite and coal coarse refuse on the thermal phase transformation, the mixtures were calcined at 700 °C and 1000 °C, respectively. XRD, DTA, and acid leaching test results showed that the phase transformation of florencite-(Ce) was an independent reaction.