Separation of Naturally Occurring RE Elements

Most reserves of RE that are distributed in China occur in the south of China. The minerals contain all the RE elements except Pm. Their abundances vary in the different mineral sources. The RE composition of the sample used in the separation example summarized in Table 10 is presented in this table. 

The sample described in Table 10 has been separated by employing the following conditions dictated by the results of earlier fundamental studies. The five-column system was employed for the separation. Neutral salt added to 0.075 mol/L EDTA at a pH value of 7.3 was used as the ion displacer. The column ratio was 1 2. The temperature of the process was fixed at 75°C. All products exited from the last column. Yb-(169, 175) was used to define the boundary curves of Lu-Yb and Tm-Yb, while Tb-160 was used to define the boundary curves of Tb-DY and Tb-Gd. In addition, Tm-170 and Gd-(153, 159) were used to determine the displacement curves of Tm and Gd. Other element boundaries were defined by using spectrophotometry. The results obtained are shown in Fig. 9. 

It is immediately apparent that the elements can be separated in a single operation of the five-column system. Even though Lu, Tm, and Pm, elements present at the lower percentages, were not completely separated they were directed to their respective zones. It can be predicted on the basis of this result that, if large amounts of sample are separated, and the cross section of the last column is properly defined, these pure elements will emerge as products. 

With one sequence of operations the separation of elements such as Yb, Er, Ho, Dy, Tb, Gd, Sm, and Nb with the five-column system have yielded 

Re oxide Y2O3 La,0, CeOj PfeOn NdjO, SrajOj EujOj 

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