Thermal decomposition mechanism of low-content-fluorite Bayan Obo rare earth concentrate roasted with sodium carbonate and its consequent separation study

Thermal decomposition and phase transformation for the mixture of Bayan Obo rare earth concentrate (BORC) and sodium carbonate (Na2CO3) roasted at different temperatures with weight ratio of 100:20 were studied in detail in our study. The aim of our study is to reveal the nature of roasting reaction between BORC and Na2CO3 and thus providing a new method for processing BORC. The results indicate that BORC can be decomposed completely with Na2CO3 at around 600 degrees C after 3 h. During the calcination process, Ce0.5Nd0.5O1.75, NaF, Na3PO4, and a rare earth double phosphate phase Na3RE(PO4)(2) are formed after the decomposition of BORC with Na2CO3. In addition, the thermal decomposition mechanism is determined in the paper. Based on these facts, a clean technique processing BORC was developed. And a CeF3 powder, whose composition was measured and stability was also evaluated, was obtained for some potential application from the new technique. This research is of significance in terms of the Na2CO3-roasting BORC solid reaction study and sheds a light on a potential clean technique for BORC. (C) 2020 Published by Elsevier B.V. on behalf of Chinese Society of Rare Earths.