G. V. Kostikova

Extraction methods in development of Gd-loaded liquid scintillators for detection of low-energy antineutrino: 1. gadolinium extraction with carboxylic acids

A comparison was made of the properties of solvents meeting the requirements posed on Gd-loaded organic liquid scintillators (transparency, light output, compatibility with the structural materials of the detector). The optical properties of the solvents were examined in relation to various factors (purity of the initial reagents, concentrations of Gd and scintillation additives). Extraction of Gd with C4 C8 carboxylic acids was examined. The composition of the extractable Gd complexes with 2-methylvaleric and 2-ethylhexanoic acids, GdR3·3HR·mH2O (where m = 1–2, depending on the solvents used), was determined. The solubility of water in 2-ethylhexanoic and 2-methylvaleric acids was examined. Scintillators based on Gd 2-methylvalerates have better parameters than those based on the other carboxylic acids tested. The instability of the optical properties of the Gd carboxylate solutions is presumably due to the presence of water in the scintillator. Possible methods of water removal from the organic phase were discussed.

Scintillators Based on Ytterbium Chloride Adducts with Neutral Organophosphorus Extractants for Detecting Solar Neutrino for LENS (Low-Energy Neutrino Spectroscopy) Experiment

The main features of extraction of ytterbium chloride with dibutyl butylphosphonate (DBBP) and triisoamylphosphine oxide (TIAPO) were studied. The effects of temperature, DBBP and TIAPO concentrations in 1,2,4-trimethylbenzene (TMB), and concentrations of salting-out agents LiCl and NH4Cl and mineral acid (HCl) on the ytterbium distribution coefficient were determined. The isotherms of extraction of HCl and YbCl3 with 50% DBBP and TIAPO in TMB were obtained. The composition of the extractable complexes of ytterbium chloride with DBBP and TIAPO (S), YbCl3·3S, was determined by saturation and dilution methods. The saturation of 50% solutions of DBBP and TIAPO in TMB with ytterbium chloride was modeled. Two samples of scintillators with ytterbium concentration of 90 g l-1 were prepared, and their physical parameters were measured. The stability of sample properties was tested for 18 months.

Extraction of Sc from various media with triisoamyl phosphate: 2. Extraction of Sc from aqueous perchloric and hydrochloric acid solutions

The extraction of Sc from aqueous perchloric and hydrochloric acid solutions with triisoamyl phosphate (TIAP) was studied. The stoichiometry of the extractable complexes (ScA3 · 3TIAP, A = ClO4/− and Cl−) was determined by the saturation and dilution technique. The isotherms of extraction of Sc from aqueous HClO4 and HCl solutions were obtained. The extraction of impurity metals (Zn, Fe, Mo, Zr, Th, REE) was studied over wide HClO4 and HCl concentration ranges.

Extraction of Scandium and Concomitant Elements with Triisoamyl Phosphate from Aqueous Solutions Containing HNO3 and LiCl

Extraction of Sc, Zr, Th, Fe, and Eu with triisoamyl phosphate from aqueous solutions containing HNO3 and LiCl has been studied. Extraction system efficient for scandium purification from concomitant admixture elements has been revealed. Prevalent Sc, Zr, Th, Fe, and Eu species that transfer to organic phase have been determined.

Scandium Extraction with Benzo-15-crown-5 from Neutral Nitrate–Trichloroacetate Solutions

A systematic study for scandium extraction with benzo-15-crown-5 in chloroform from trichloroacetate solutions has been performed. The presence of free trichloroacetic acid in extraction system has been found to prevent scandium transfer into organic phase. Scandium is extracted from neutral trichloroacetate solutions as partially hydrolyzed trichloroacetate complexes, the extracted compound includes two crown ether molecules. The presence of nitrate anions has no effect on scandium distribution ratios and nitrate anion is not involved in extracted compound composition. Optimal process conditions for selective scandium recovery from concentrated solutions of rare-earth nitrates in the presence of lithium trichloroacetate with high separation factors (>100) on the use of B15C5 as extractant have been determined.

Use of carboxylic acids in the extractive conversion of rare earth chlorides into nitrates

The main characteristics of extraction system for the conversion of total rare earth chlorides into nitrates with the use of higher isomeric carboxylic acids as extractants have been determined. Laboratory simulation of the process shows that two simplest manipulations: extraction and back extraction, allows conversion of total rare earth chlorides into nitrates with their simultaneous preconcentration by factor larger 40 without evaporation stage. These results can be further used in practice, for example, in the processes of extractive separation of rare earth elements.

Application of a semicountercurrent extraction method to waste solution treatment

General data and methods for calculations of the principal parameters of semicountercurrent extraction processes are presented. Examples of solving practical problems, based on application of the semicountercurrent extraction method to treatment of waste solutions containing various valuable components, are given. Deep purification of concentrated zinc chloride solutions to remove iron impurity with the aim of utilization of fluxing solutions was carried out. The process was performed in two semicountercurrent steps filled with VIK-II extractant in the form of zinc soap, through which the initial solution containing 250 g l−1 ZnCl2 and 0.25 g l−1 FeCl3 was passed (βFe/Zn ≥ 1500). The 100-fold amount of the solution relative to the working volume of the extractor was passed. The Fe concentration in the purified solution did not exceed 0.0025 g l−1 (<10−5%). A scheme of treatment of electrolytic chromic acid solution to remove iron was developed. Technical-grade HDEHP was used as extractant (βFe/Cr > 200). The process was performed in one semicountercurrent step filled with a solution containing 250 g l−1 chromic acid, 8.4 g l−1 Cr(III), and 13 g l−1 Fe(III), through which the extractant was passed in a volume equal to 0.66 of the initial aqueous solution volume. The Fe recovery was 98.5%. With Wo = Va, the Fe recovery was as high as 99.9%. A minor fraction of Cr (<8%) coextracted with Fe can be returned to the process.

Linear alkylbenzene (LAB) as diluent for extractants. Extraction of rare-earth elements with solutions of neutral organophosphorus compounds in LAB

Extraction of REE with solutions of neutral organophosphorus compounds (TBP, TIAP, DIOMP) in a new diluent, linear alkylbenzene (LAB), was studied. LAB exhibits significant advantages over known diluents: high flash point (+147°C), nontoxicity, absence of odor, low cost, availability, and good compatibility with polymeric structural materials. LAB is well compatible with TBP, TIAP, and DIOMP. Extraction of HNO3 and REE nitrates is not accompanied by precipitation of extractable complexes or by formation of a second organic phase in a wide concentration range, up to saturation of the extractant. The major extractable complex in extraction of REE nitrates is Ln(NO3)3·3NOPC, where NOPC = TBP, TIAP. The main parameters of extraction systems (distribution ratios, separation factors) with LAB are similar to those of the related systems with paraffin hydrocarbons as diluents. Experiments on group separation of REEs on a 56-step extraction installation gave results agreeing with the calculation data.

Extraction of Scandium from Various Media with Triisoamyl Phosphate: 3. Development of Extractive Refining of Scandium

Scandium refining to remove both more and less extractable impurity metals from hydrochloric acid solutions using semicountercurrent and countercurrent extraction with triisoamyl phosphate is modeled. A process for preparing high-purity scandium is developed, involving removal of more and less extractable impurity metals by semicountercurrent extraction and full countercurrent extraction, respectively, at a limited number of separation steps. From the initial scandium oxide (98% purity), 99.97% scandium oxide was prepared (99.995% purity with respect to REEs), i.e., the decontamination factors from both REEs and other impurity metals exceed 100.