RU1786162C - Method of separating yttrium group rare-earth metal concentrates in solutions of nitrates - Google Patents

Abstract

Usage: rare earth metal (REM) hydrometallurgy and can be used for group separation of the rare earth metals of the yttrium group. Essence: using as a extractant a mixture of diisooctyl methylphosphonate and tri-n-butyl phosphate in their molar ratio (5-15): 1, and extraction is carried out from solutions containing REM nitrates from 0.1 to 1.0 mol / dm nitric acid from 10 to 1.0 mol / dm and a salting out agent, for example ammonium nitrate, from up to 6.0 mol / dm3. 1 C.p. f-crystals, 1 tab.

Description

The present invention relates to the field of hydrometallurgy of rare earth metals (REM) and can be used to obtain compounds of individual REM of the yttrium group and yttrium.

Currently, to obtain compounds of the individual rare-earth metals of the yttrium group and yttrium, for the purpose of complex processing of mineral raw materials, various extraction systems of preliminary group separation into a concentrate of medium rare-earth metals (from samarium to holmium) and yttrium and heavy rare-earth metals (from erbium to lutetium) with subsequent isolation of individual rare-earth metals and yttrium.

The concentrate of medium rare-earth metals is processed according to the technological scheme, which provides for the separation of europium (II) by the deposition of double sulfates, followed by extraction or sorption separation of individual secondary rare-earth metals, the content of europium in the initial

concentrate of medium rare-earth metals should be at least 6 wt.% of the amount of rare earth metals.

A known method for the extraction separation of sharp-earth metals by extraction of light rare-earth metals (from lanthanum to neodymium) with a solution of a tertiary amine or quaternary ammonium base in an inert diluent, followed by separation of yttrium and heavy rare-earth metals using organic acids as an extractant.

The main disadvantages of this method are the use of extractants of various classes, which leads to the necessity of purifying aqueous solutions of organic substances before subsequent extraction steps and significant material costs, as well as a low separation factor between holmium and yttrium, that is, between separation is carried out, not more than 1.6.

With

with

A method for the single-stage isolation of yttrium from rhodanide chloride solutions is known using oil sulfoxides in polyacrylbenzene as an extractant at a temperature of 40 ° C. The minimum value of the separation factor when using this method is 2.7.

The main disadvantages of this system are the use of a fire-explosive and toxic diluent in the organic phase and toxic rhodanide ion in the aqueous phase, the need to thermally stabilize the extraction process, and the impossibility of further processing of the obtained rare-earth concentrates according to the existing technological schemes with the aim of complex processing of raw materials and obtaining individual REM.

The closest in technical essence is the frequency used in industry for the extraction separation of rare-earth metals of the yttrium group from nitrate solutions using tri-n-butyl phosphate and a washing solution containing ethylenediamine tetraacetate (EDTA) 3 as an extractant.

The main disadvantages of this method are: low productivity of the process and a large number of stages of the extraction cascade, which is due to the low value of the separation factor of the erbium-yttrium pair (1.35-1.50).

The aim of the invention is to increase the productivity of the process and reduce the number of stages of the extraction stage, while maintaining the degree of purification.

According to the invention, the goal is achieved by using in a known method a mixture of diisooctyl methylphosphonate and tri-n-butyl phosphate in the molar ratio of (5-15): 1, respectively, and carrying out the process from a solution containing REM nitrates from 0.1 up to 1.0 mol / dm, nitric acid from 10 to 1.0 mol / dm43 and salting out agent 6.0 mol / dm. Sodium nitrate or ammonium nitrate or other reagents may be used as a salting out agent.

The method is based on the formation of extractable complexes of medium rare-earth metals, including erbium, with diisooctylmethylphosphonate in the specified concentration range of rare-earth metals, nitric acid and salting out agent under the action of tri-n-butylphosphate as a sensitizing additive.

New is the use of a mixture of phosphonic acid ester (diisooctylmethylphosphonate) and tri-n-butylphosphate for

group separation of rare-earth metals of the yttrium group from nitrate solutions. The proposed technical solution has not been used anywhere before.

New significant features ensure the achievement of a positive effect - an increase in the productivity of the process and a reduction in the number of stages of the extraction cascade while maintaining the degree of purification.

The set of essential features corresponds to the criterion of significant differences, since it gives the system as a whole a new property, namely, the possibility of carrying out a continuous process of separation of rare-earth metals of the yttrium group with higher productivity at a smaller number of stages of the extraction cascade while maintaining the degree of purification.

A decrease in the content of TBP in the organic phase of less than 5 vol% leads to a decrease in the productivity of the process due to an increase in the phase separation time. An increase in the proportion of TBP over 15 vol% leads to an increase in the number of stages of the extraction cascade due to a decrease in the separation factor of the erbium-yttrium pair.

A decrease in the concentration of nitric acid in the aqueous phase of less than 10 mol / dm0 leads to the precipitation of REM hydroxides. An increase in its concentration above 1.0 mol / dm leads to a decrease in the productivity of the process by reducing the capacity of the organic phase.

A decrease in the concentration of rare-earth nitrates in the aqueous phase below 0.1 mol / dm; leads to a decrease in the productivity of the process due to the small use of the capacity of the extractant. An increase in the concentration of REM nitrates in the aqueous phase above 1.0 mol / dm leads to an increase in the number of stages of the extraction cascade due to a decrease in the separation factor of the erbium-yttrium pair.

Carrying out the process with a concentration of rare-earth nitrates in the aqueous phase up to 0.2 mol / dm involves the use of a salting out agent, for example ammonium nitrate. The concentration of salting out agent should not exceed 6.0 mol / dm. An increase in the concentration of salting out agent above 6.0 mol / dm leads to an increase in the number of stages of the extraction cascade due to a decrease in the value of the separation factor of the erbium – yttrium pair.

When using the developed technological process, the productivity is 25-32 kg of REM oxides / h, the number of steps is from 30 to 60. In the prototype

productivity is 15-18 kg of REM oxides / h, the number of steps is 85.

The data on examples are given in the table.

EXAMPLE 1. During the experiment, an aqueous solution was taken with a concentration of REM nitrates of 1.0 mol / dm3, nitric acid 0.6 mol / dm and an ammonium nitrate salting out agent of 0.01 mol / dm. The organic phase was 90 vol% diisooctyl methylphosphonate and 10 vol% tri-n-butyl phosphate. The phases were contacted at a ratio of 1: 1 for 0.5 h, after which the phase separation time, analytical concentrations of individual rare-earth metals and yttrium and nitric acid in the aqueous and organic phases were determined. The partition coefficient was calculated as the ratio of the concentration of the component in the organic phase to its concentration in the aqueous phase. The separation factor was calculated as the ratio of the distribution coefficients of erbium and yttrium.

The initial mixture of rare-earth metals had the following composition, wt.%: Samarium 6.1; europium 2.4; gadolinium 9.3; terbium 1.8; dysprosium 10.6; holmium 1.9; erbium 5.6; thulium 0.7; ytterbium 2.5; lutetium 0.5; yttrium 58.4.

The separation factor between erbium and yttrium is 1.85.

Based on this value, the number of stages of the extraction cascade necessary for the group separation of rare-earth metals was calculated. The calculation was carried out according to the well-known method of Alders A. Liquid extraction. // M .: Inostrlit. 1957. According to the calculation results, the extraction part of the cascade should consist of 20, and the washing part of the cascade of 15 steps.

Examples 2-22. The initial mixture of rare-earth metals the same composition as in example 1. We used solutions with a concentration of rare-earth nitrates from 0.05 to 1.5 mol / dm3, nitric acid from 10 to 1.5 mol / dm and a salting out agent of ammonium nitrate or NaNOa from 0 up to 7.0 mol / dm3. The concentration of tri-n-butyl phosphate in the organic phase varied from O to 25 vol%. The experimental results are shown in the table.

Example 23. The proposed method for the extraction separation of rare-earth metals of the yttrium group was tested at the Irtysh KhMZ in 1990

A solution of rare-earth nitrates with a total concentration of 0.85 mol / dm3, nitric acid 0.3 mol / dm without a salting out agent was chosen as the initial one. The concentration of tri-n-butyl phosphate in the organic phase was 10 vol%. The tests were performed on an extraction cascade consisting of 33 mixer-settler extractors with a mixing chamber volume of 9

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dm, and the camera is behind 23 dm. The extraction part of the cascade consisted of 23, and the washing part of 10 steps. The cascade productivity in terms of total flows was 97 dm3 / h.

From the initial mixture of the composition, wt.%: Samarium 6.1; europium 2.4; gadolinium 9.3; terbium 1.8; dysprosium 10.6; holmium 1.9; erbium 5.6; thulium 0.7; ytterbium 2.5; lutetium 0.5;

yttrium 58.4, were obtained:

1) a concentrate of medium rare-earth metals of the composition, wt.%: Samarium 16.2; europium 6.2; gadolinium 25.5; terbium 4.6; dysprosium 31.0; holmium 5.7; erbium 9.3; thulium 0.2; ytterbium 0.01; lutetium 0.001; yttrium 1.5;

2) a concentrate of yttrium and heavy rare-earth metals of the composition, wt.%: Samarium 0.01; europium 0.001; gadolinium 0.01; terbium 0.001; dysprosium 0.001; holmium 0.001; Erbium 1.5: Thulium

0.6; ytterbium 5.8; lutetium 0.6; yttrium 91.5.

Claims (2)

From the above examples it follows that the use of the proposed method will increase the productivity of the process and reduce the number of stages of the extraction cascade while maintaining the degree of purification. This result is achieved due to the higher (compared with the prototype) value of the separation factor of the erbium-yttrium pair. SUMMARY OF THE INVENTION 1. A method for separating concentrates of rare-earth metals of the yttrium group from nitrate solutions, including extraction of medium rare-earth metals: from samarium to erbium from a solution of a mixture of rare-earth metal nitrates and yttrium tri-n-butyl phosphate, characterized in that, in order to increase productivity and reduce the number of stages of the extraction cascade while maintaining the degree of purification, a mixture of di-isooctylmethylphosphonate and tri-n-butylphosphate with their molar ratio (5-15): 1, and extraction is carried out from solutions containing rare earth nitrates from 0.1 to 1.0 mol / dm3, nitric acid from 10 to 1.0 mol / dm3 and salting out agent from up to 6.0 mol / dm3. 2. The method according to claim 1, with the fact that sodium nitrate or ammonium nitrate is used as a salting out agent. Continuation of the table Examples outside the scope of the present.