The paper presents the results of studies on a hydrometallurgical process that includes the separation of a cerium concentrate in the form of Ce(IV) hydroxide from a nitrate solution of total rare earth elements (∑REE) obtained by dissolving a rare earth concentrate in nitric acid; dissolution of the separated Ce(IV) hydroxide in nitric acid to obtain a feed solution for purification extraction; purification of cerium from other rare earth elements and impurities by liquid–liquid extraction using 100% tributyl phosphate; precipitation of cerium oxalate from the re-extract of the purification extraction followed by washing and calcination of the cerium oxalate, resulting in the production of high-purity cerium dioxide with a CeO₂ content of at least 99.95%.

The objective of the present work was to determine optimal conditions for the separation of cerium from a mixture of rare earth elements and its subsequent deep purification by extraction using 100% TBP.

Rare earth metal carbonates were used as the initial raw material, with a typical composition presented in Table 1. In addition, a rare earth concentrate obtained in the form of rare earth hydroxides from the re-extract of a cascade for extraction purification of a phosphate rare earth concentrate, recovered as a by-product during apatite processing via a nitric acid route, was used. The composition of this concentrate, recalculated to the calcined product, was (%): ∑REO > 98.0, P₂O₅ < 0.01, Ca < 0.01, Fe < 0.01.

The technological scheme for cerium separation and purification begins with dissolution of rare earth concentrates in nitric acid solution. The resulting solution, which is a nitrate solution of total REEs, is then fed to the cerium concentrate separation stage by precipitation.

All methods currently used for separating cerium from other rare earth elements are based on the ability of cerium to be oxidized to the tetravalent state. Tetravalent cerium compounds differ significantly in their properties from trivalent lanthanides, which facilitates separation.

Hydrogen peroxide is the most convenient and effective oxidizing agent, particularly for the production of high-purity cerium, and is widely used in industrial practice.