RU2596245C1 - Method for extraction separation of rare-earth elements - Google Patents

Abstract

FIELD: technological processes.

SUBSTANCE: invention relates to extraction separation of rare-earth elements from nitrate solutions. Method involves extraction of initial solution containing nitrates of rare-earth elements and salting-out agent with tributyl phosphate, washing and re-extraction with acidified water. At that, re-extraction agent relative to initial solution is divided into two flows at ratio of initial solution:first flow:second flow is equal to 1 : (0.3-0.4) : (0.5-1.0), after which first flow is evaporated to concentration of 280-320 g/l and delivered for washing out organic phase, and second flow is treated with ammonium hydroxide or ammonium carbonate and hydroxide is separated by filtration of rare-earth elements, and filtrate is delivered for preparation of initial solution.

EFFECT: invention provides efficient extraction of rare-earth elements and reduced power consumption.

1 cl, 1 tbl, 3 ex

Description

The invention relates to a technology for the extraction separation of rare earth elements (REE) from nitric acid solutions using tributyl phosphate (TBP).

In industrial practice, the separation of REE by extraction of TBP is mainly carried out from nitric acid solutions. Known methods for the separation of REE by extraction of TBP from nitric acid solutions containing 8 mol / l of nitric acid [Korpusov GV, Eskevich IV, Zhirov EP Group separation of rare earth elements by countercurrent extraction // Sat. Extraction. Theory, application, equipment. - M.: Gosatomizdat, 1962, issue. 1. S. 126]. Also, REEs are well extracted by TBP from weakly acid nitrate solutions in the presence of salting out agents - aluminum, sodium, calcium, lithium nitrates, for example, from REE nitrate solutions containing 0.2-0.3 mol / L nitric acid and aluminum nitrate [G. Korpusov ., Eskevich I.V., Zhirov E.P. Patterns of the extraction distribution of rare-earth elements in neutral solutions // Sat. Extraction. Theory, application, equipment. - M.: Gosatomizdat, 1962, issue. 2]. The disadvantages of these processes is the presence of a large number of washing solutions that require disposal.

Closest to the technical solution to the proposed method is a method of extraction separation of rare earth elements [RU No. 2058938, C01F 17/00. Otub. 04/27/1996], adopted as a prototype. REE separation is carried out from neutral or slightly acidic solutions using neutral organophosphorus extractants, mainly TBP, in a countercurrent cascade consisting of extraction, washing and re-extraction parts. The method involves re-extraction with 6-8.5 M nitric acid, while the extraction part of the cascade to the 16th stage is supplied with a salting out solution in an amount ensuring their concentration in the aqueous phase until saturation and the raffinate is selected from the stage following salting out stage. To the extraction part from the outlet side of the raffinate or from the outlet side of the extract, the containers filled with the initial solution are alternately connected, from which the products are alternately selected. In the proposed method, one stripped re-extract is used as a washing solution.

The disadvantage of this method is the need to evaporate the entire re-extract, which leads to high energy consumption and, accordingly, increases the cost of the final product.

The aim of the invention is to reduce the energy consumption for evaporation of the washing solution for washing by reducing the volume of the evaporated solution.

This object is achieved in that the method of separation of rare-earth elements by extraction with tributyl phosphate stock solution containing nitrates of rare-earth elements (REE) and a salting out agent includes extraction, washing and re-extraction with acidified water, and the resulting re-extract with respect to the initial solution is divided into two streams in the ratio of the original solution: 1st stream: 2nd stream = 1: (0.3-0.4) :( 0.5-1.0), after which the 1st stream is evaporated to a concentration of 280-320 g / l and sent to the washing of the organic phase, and the 2nd stream is treated with hydra ammonium oxide or ammonium carbonate, REE hydroxides are separated by filtration as a finished product, and the filtrate is sent to prepare the initial solution.

Example 1 (prototype).

The separation of REEs isolated from apatite was carried out along the neodymium-samarium line. Extractant - 100% TBP. The initial solution contained 300 g / l REE (calculated as oxides) and 350 g / l ammonium nitrate. The organic phase was washed with a solution containing 300 g / l REE nitrates. After washing, the concentration of REE in the organic phase was in the range of 145-155 g / l. With the obtained organic phase, experiments were carried out to simulate the back extraction mode. The countercurrent process of stripping was modeled at 12 steps. Reextracting solution - a solution of nitric acid with a concentration of 0.3 mol / L. An organic phase containing 150 g / l REE (calculated as oxides) was fed into the first stage. In step 12, a stripping solution was applied. The organic phase was introduced in a volume of 20 ml, the stripping solution was 14 ml. The concentration of REE in the reextract was 212 g / L. A 50 ml re-extract was evaporated to 302-305 g / l. The volume of condensate from the distilled off steam was 4.2 ml.

Example 2 (the proposed method).

The countercurrent process of stripping was modeled at 12 steps. Extractant - 100% TBP. Reextracting solution - a solution of nitric acid with a concentration of 0.3 mol / L. An organic phase containing 150 g / L REE (calculated as oxides) was supplied to the first stage, the first stripping solution was fed to the 6th step, and the second stripping solution was fed to the 12th step. The organic phase was introduced in a volume of 20 ml, the first stream of stripping 7 ml, the second stream of stripping 12 ml. The concentration of REE in the first stream of reextract was 251 g / l, in the second stream of reextract 104 g / l. The first stream of stripping was evaporated to 300 g / l. The volume of condensate from the distilled off steam was 1.2 ml. 40 ml of a second stream of stripping was added and 7 ml of concentrated ammonium hydroxide was added to a pH of 7-8, the precipitate was filtered off and washed. The filtrate was combined with washing to obtain 62 ml of a solution of ammonium nitrate, which was sent to prepare the initial solution for the repulpation of REE carbonates or for evaporation.

Example 3 (selection of optimal flow ratios).

The experiments were carried out as in examples 1 and 2, but the phase ratio was changed at the stage of stripping. The experimental results are given in table. one.

The number of selected, i.e. Derived from the process, REE at the first reextraction depends on a given sampling value, which in turn is determined by the separation coefficients. For the processes under consideration, the separation coefficient ranges from 1.9-2.5, the amount of selection in the finished product is 0.35-0.5, and the amount of REE returned to the washing stage is 0.5-0.65. This circumstance determines the phase ratio on the 1st reextraction. The second reextraction is not so fixed and the main task for it is to extract all REEs without leaving even their traces in the organic phase.

The positive effect of the proposed method for the separation of rare earth elements by extraction is to reduce the amount of evaporated reextract and, accordingly, reduce energy consumption when obtaining rare earth elements, which allows to reduce the cost of the final product.

Claims (1)

The method of separation of rare earth elements by extraction with tributyl phosphate stock solution containing nitrates of rare earth elements (REE) and a salting out agent, including extraction, washing and re-extraction with acidified water, characterized in that the re-extract with respect to the initial solution is divided into two streams in the ratio of the initial solution: 1st flow: 2nd flow = 1: (0.3-0.4) :( 0.5-1.0), after which the 1st flow is evaporated to a concentration of 280-320 g / l and sent to the washing of the organic phase and the 2nd stream is treated with ammonium hydroxide or ammonium carbonate Nia, rare earth hydroxides is separated by filtration, and the filtrate is directed to the preparation of the starting solution.