Rare Metals Recovery from the Sorbents of the Sorption Conversion of Eudialyte Concentrate

In order to develop the technology of eudialyte concentrate processing based on the use of sorption conversion, the patterns of metal extraction from sulphocationites saturated in the process and the regeneration of sulphoca-tionite and solutions used for desorption for reuse are investigated. The compositions of saturated sorbents con-taining alkaline metals (sodium, potassium), alkaline earth and rare earth metals, titanium, zirconium (hafnium), niobium (tantalum), aluminium, iron, manganese, natural radionuclides are presented. Desorption with various solutions is investigated. It is found that niobium (tantalum) is most difficult to desorb. It is recommended to carry out two-stage desorption at a temperature of 20 degrees C: at first, with a 5 M NaCl solution, in which the majority of metals contained in the sorbent are converted into solution, and then desorption of zirconium and niobium with a 1 M H2C2O4 solution. The issues of further processing of the obtained desorbates are considered. In accordance with previous studies, the impurity cake containing thorium, iron, aluminium, titanium is precipitated and sepa-rated from desorbates based on a 5 M NaCl solution through fractional neutralization, initially to pH 4, then the concentrate of rare earth elements is separated by neutralization to pH 7.5, and, finally, at pH >= 10, alkaline earth metals and manganese. Zirconium (hafnium) - niobium concentrate is precipitated from desorbates based on 1 M H2C2O4 solution through neutralization with NaOH to pH 10, and then zirconium (hafnium) is leached from it using Na2CO3 solution. It is stressed that the sorbent in the H+-form is formed after desorption with a 1 M H2C2O4 solution, which allows using it repeatedly to decompose eudialyte concentrate by sorption conversion. It is shown that the 1 M H2C2O4 solution can be regenerated by electrodialysis from the Na2C2O4 solution obtained by precipitation of the collective zirconium (hafnium) - niobium concentrate.