Cerium Separation from Light Rare Earth Concentrate by Liquid-Liquid Extraction

Abstract

This work presents an investigation of solvent extraction parameters in order to obtain high purity cerium from a mixture containing other rare earths elements, as an alternative to oxidation and selective precipitation or dissolution. The study was carried out using a sample of sulfuric liquor obtained from the leaching of monazite rich in light rare earth elements (La, Ce, Pr, Nd) provided by INB (Indústrias Nucleares do Brasil S.A.). Experiments were carried out in chloridric, nitric and sulfuric media. The nitric and hydrochloric solutions were prepared by precipitation of the REE from the sulfuric liquor as rare earths oxalate, calcining the precipitate and dissolving it with nitric or hydrochloric acid. The separation of cerium was investigated in its trivalent and tetravalent forms. The parameters investigated were: type and concentration of extractant, type and amount of the oxidizing agent, liquor acidity, and volumetric ratio between organic and aqueous phases. The preference of the organic phase to extract cerium in its oxidized form (IV) over the other rare earths elements was confirmed, allowing the obtainment of a high purity cerium solution. The best results were achieved in nitric medium, with cerium in its tetravalent form, using cationic extractants (P507 or D2EHPA) and a mixture of potassium persulfate and silver chloride as oxidizing agents, yielding over 99% of cerium extraction with over 99% of purity.

Dissolution of Rare Earth Elements Concentrate from Xenotime Sand with Strong Acids

“…In general, HNO3 and H2SO4 can be oxidizing agents, so the Ce ions in the solution can change from valence 3 to valence 4. Ce at valence 4 only dissolves in sulfate solution [16], so the solubility of light REE in this study can be quite high with H2SO4. However, the oxidizing agent factor was not really affected in this study because most REE is stable in valence 3, and it needed a very strong oxidizing agent such as peroxodisulfate or bismuthate is required to oxidize REE ions [15].…”

Gibbs Energy Minimization Model for Solvent Extraction with Application to Rare-Earths Recovery

“…We applied the GEM approach to the separation of REE mixtures relevant to recycling (NiMH) batteries (Neodymium, Nd; Praseodymium, Pr; Cerium, Ce; and Lanthanum, La). For this study, we collected a set of single-component and multicomponent REE extraction equilibrium isotherm data from the literature, ,− reported for M REE – HCl – PC88A systems, over a range of pH values, extractant fractions, and rare-earth concentrations (see Supporting Information S0-B for data sources). Having set up the problem, we first use visualization experiments to gain insight on the least-squares solution space, given the chemistry implicit in the experimental data sets.…”

Amidophosphonate ligands as cerium extractants in supercritical CO2

“…3). The cotton pads containing the amidophosphonate compounds were placed in a reactor (38 cm 3 The solubility was determined (mol/mol) by weighing the amount of extractant collected in the collector (± 0.1 mg), using Eq. (1):…”

“…The extractants for liquid-liquid extraction processes described in the literature are generally organophosphorus compounds with extraction capacities of 10-300 mmol Ce per mol (mmol/mol). For example, Cyanex ® 272, Cyanex ® 301 and D2EHPA have been used to extract up to 98 mmol/mol of cerium from monazite and Indian red mud ore [3,4]. Elsewhere, Lu et al.…”