Sulfurization of rare-earth oxides with CS2

In the scheme of spent fuel reprocessing by using sulfides, selective sulfurization of rare-earths in the fuel is considered followed by either magnetic separation or selective leaching of rare-earth sulfides from uranium oxides such as UO2. In this paper, sulfurization behavior of rare-earth oxides was investigated by XRD and TG methods in the presence of CS2. From the results of thermogravimetric study the sulfurization of europium proceeds as follows; sulfurization from Eu2O3 to Eu3S4 occurs at ca. 400 deg. C, then the Eu3S4 decomposes to EuS via non-stoichiometric sulfides at temperatures between 450 and 700 deg. C. From the results of thermogravimetry for Nd2O3, it was found that the weight curve showed monotonic increase from ca. 600 to 1000 deg. C. At 1000 deg. C, the value of weight increase was close to that for the formation of Nd2S3 from Nd2O3. The XRD result of the 1000 deg. C product showed a formation of a single phase of Nd2S3 which is compared with the thermogravimetric result as well as our previous results. The selective sulfurization of rare-earths in the mixture of rare-earth and uranium oxides was discussed by both experimental results and thermodynamical consideration