Influence of microwave heating on the extractions of fluorine and Rare Earth elements from mixed rare earth concentrate

A novel process was proposed to treat the mixed rare earth concentrate by utilizing the microwave radiation. The influences of microwave heating on the mechanism of decomposition, microstructure of mixed rare earth concentrate, the behavior of fluorine leaching by water and the rare earth elements(REEs) leaching by hydrochloric acid were investigated. The results showed that bastnaesite and monazite were decomposed efficiently to rare earth oxide, and fluorine containing compounds were converted to fluoride after the microwave treatment. However, the bastnaesite and monazite were partly decomposed to REEs hydrate after treating with the conventional heating (convective heating). The recoveries of fluoride in the solutions of water and REEs in the solution of hydrochloric add by leaching the concentrate treated with microwave radiation reached 67.1% and 82.5%, which were much higher than for those with conventional heating process (38.5% and 47.4% respectively). The increase in the recovery of fluorine and REEs is attributed to the phase transformation of REEs minerals due to the microwave characteristics of the rapid internal heating and energy transfer. (C) 2016 Elsevier B.V. All rights reserved.