Extraction of Scandium from Various Media with Triisoamyl Phosphate: 1. Extraction of Sc and Impurity Metals from Aqueous Nitric Acid Solutions

Abstract

The main features of extraction of Sc from aqueous nitric acid solutions with triisoamyl phosphate (TIAP) were studied. It was shown that Sc passes into the organic phase in the form of Sc(NO 3 ) 3 . 3TIAP. The extraction isotherms of Sc from its aqueous HNO 3 solutions and from those containing salting-out agents (LiNO 3 , NH 4 NO 3 ) with TIAP in dodecane were obtained. The distribution factor of Sc was studied in relation to the concentrations of TIAP, salting-out agent, and HNO 3 . The extraction of Sc and impurity metals (Zr, Th, REE) with TIAP was studied at widely varied HNO 3 concentration in the aqueous phase. The separation factors of Sc from impurity metals were determined. Scandium, a rare metal, finds application in various modern branches of science and industry. However, high price of scandium caused by complicated technique of its recovery from very lean ores hinders wide-scale application of this metal. Therefore, the development of techniques ensuring the efficient recovery and purification of this metal is an urgent problem.It is known that the main industrial process for recovery of rare metals, among them scandium, is extraction. This technique is characterized by high performance, relative simplicity of equipment and process control, high selectivity, and other advantages.As a rule, rare metals are extracted with neutral organophosphorus compounds (mainly TBP) and organophosphorus acids, e.g., di(2-ethylhexyl) hydrogen phosphate (HDEHP).A new organophosphorus reagent, triisoamyl phosphate (TIAP), recently became available. It was reported [1, 2] that, in extraction of REEs and other metals, this extractant shows certain advantages.TIAP in inert solvents ensures higher stability of the organic extract with respect to its separation into two organic phases in recovery of metals and acids from their concentrated aqueous solutions. The solubility of TIAP in water is approximately twenty times lower than that of TBP. Low solubility of TIAP in water is especially important in preparing high-purity scandium and other metals, since it decreases the contamination of raffinate with phosphorus and facilitates the regeneration of solutions to be discharged and evaporated.No data have been reported on extraction of Sc and impurity metals with TIAP. In this work we studied these questions to estimate the suitability of TIAP for extractive recovery and purification of scandium to obtain high-purity metal. EXPERIMENTALIn our experiments we used commercial triisoamyl phosphate, TU (Technical Specification) 6-02-13-203 83. This reagent contained more than 98% main compound, 0.06% isoamyl alcohol, and less than 0.002% isoamyl hydrogen phosphate. The density of this reagent was 0.952 g cm !3 . Before extraction, TIAP was triply treated with aqueous Na 2 CO 3 and then washed with distilled water to neutral reaction. Dodecane (pure grade) was used as diluent.The Sc-containing salt solutions were prepared by dissolving scandium oxide (99.9% purity) in the required amount of aqueous mineral acid. The mineral acids ...

Solvent Extraction and Conformation Rigidity: Actinide(IV) and Actinide(VI) Come Together

“…The distribution ratios ranged from low to moderate through the entire range of nitric acid concentrations for trace and millimolar quantities of radionuclides. Moreover, above 4.46 M nitric acid, the D values decreased for Eu­(III) because of the competing nitric acid extraction, which was typical for the separation of light and medium lanthanides by neutral phosphororganic compounds . Slope analysis of the nitrate groups showed that the three nitrate anions were present in the complexes with both metals (Figure S22).…”

“…Moreover, above 4.46 M nitric acid, the D values decreased for Eu(III) because of the competing nitric acid extraction, which was typical for the separation of light and medium lanthanides by neutral phosphororganic compounds. 59 Slope analysis of the nitrate groups showed that the three nitrate anions were present in the complexes with both metals (Figure S22). Notably, the competitive extraction of nitric acid does not affect the actinide (Np, Pu, U, Th, and Am) extraction over the entire studied range of nitric acid concentrations.…”

Scandium Recovery Methods from Mining, Metallurgical Extractive Industries, and Industrial Wastes

“…The scandium hydrated ions are Pearson’s hard acids, which mean that they prefer to form complexes with hard ligands, including hydroxide, fluoride, sulfate, and phosphate ions, due to their high charge [ 6 ]. Scandium is primarily used to produce aluminum–scandium alloys, which typically contain 2% scandium by weight [ 7 ]. These alloys are significantly stronger than the conventional high-strength alloys, with great grain refinement, high strength, no hot cracking in welds, and exceptional corrosion resistance [ 8 ].…”