RU2406772C1 - Procedure for extraction of rubidium from hydrochloric acid solutions - Google Patents

Abstract

FIELD: metallurgy. ^ SUBSTANCE: procedure for extraction of hydrochloric acid solutions consists in sedimentation of rubidium and in crystallising sediment in form of rubidium hexa-chlorid-tellurite. Sedimentation from hydrochloric solutions is performed with normality of hydrochloric acid within the range 6-12 n with solid tellurium dioxide. The process is carried out at 20-25C with mixing during 3 hours. ^ EFFECT: improved separation and increased degree of rubidium extraction. ^ 1 tbl, 1 ex

Description

The invention relates to the field of metallurgy of rare alkali metals and can be used in technology and analytical chemistry of rare alkaline elements.

Known methods are based on the extraction of rubidium and cesium from solutions with a large salt background, their deposition in the form of metal halides of metals such as platinum, antimony, tin, lead and others. The least studied from this group of coordination compounds of rubidium are halogen chalcogenates, including rubidium hexachlortellurite.

A known method of producing hexachlorotellurite rubidium (Brower G. Guide to preparative inorganic chemistry. M .: Publishing house of Foreign literature, 1956, p.225). A solution of TeCl ₄ in hydrochloric acid, necessary for precipitating rubidium, is prepared by treating powdered tellurium with aqua regia, evaporating this solution to dryness and dissolving the residue in exactly the right amount of concentrated hydrochloric acid.

The disadvantage of this method is that when a precipitating solution is added to the hydrochloric acid solution, the initial solution is diluted, thereby reducing the concentration and degree of separation of rubidium from the solution.

Another disadvantage of this method is the difficulty of preparing a precipitating solution for the precipitation of rubidium.

The closest to the implementation method is the method of deposition of cesium from hydrochloric acid solutions (Sat. Rare alkaline elements. Perm, Publishing House of the Perm Polytechnic Institute, 1969, p.306), adopted as a prototype. The cesium precipitation reaction is carried out by adding a reagent (hexachlorotelluric acid) to a solution of cesium salt in 11-12 N. hydrochloric acid. The reagent is prepared by dissolving tellurium dioxide in concentrated hydrochloric acid, evaporating to a small volume and diluting the cooled residue with a solution of 11-12 N. of hydrochloric acid.

The disadvantage of this method is the difficulty of preparing a precipitating solution for the deposition of cesium.

Compared with the well-known version of the synthesis of H ₂ TeCl ₆ from powdered tellurium, the use of tellurium dioxide greatly simplifies the technology, especially since it is an industrially produced reagent that is very stable and can be stored for a long time without compromising its properties. However, the solution used for the precipitation of rubidium must be prepared, stored and analyzed in advance, and when used, it dilutes the process stock solution and thus reduces the extraction of rubidium from the solution, especially for rubidium-rich solutions.

The aim of the invention is to increase the extraction of rubidium, cost-effectiveness and ease of implementation of the method.

The technical result consists in improving separation, increasing the degree of extraction of rubidium and reducing the residual concentration of rubidium in solution after precipitation.

The technical result is achieved by the fact that in the method of extracting rubidium from hydrochloric acid solutions, including its precipitation and crystallization in the form of rubidium hexachlorotellurite, according to the invention, the precipitation is carried out from hydrochloric solutions with a norm of hydrochloric acid in the range of 6-12 N. solid tellurium dioxide at 20-25 ° C with stirring for 3 hours.

Precipitation of Rb ₂ TeCl _{6 is} carried out in hydrochloric acid solutions with a normality in the range of 6-12 N. at room temperature (20-25 ° C), adding solid tellurium dioxide with stirring for 3 hours. Three hours is enough for the most complete extraction of rubidium and the formation of a well-filtered precipitate of crystals of Re ₂ TeCl ₆ by reaction 1:

Rb ₂ TeCl ₆ crystals have a bright yellow color and a pronounced monoclinic structure. The obtained crystals of Rb ₂ TeCl _{6 were} filtered off, washed with ethanol and then dried in an oven at 100 ° С for 1 h.

The identification of crystals of Rb ₂ TeCl _{6 was} carried out by the methods of crystal optical and chemical analysis (with the determination of tellurium and chlorine). With a theoretical content of Te of 24.94% and Cl of 41.63%, tellurium was practically diagnosed as 23.6-24.8% and chlorine as 41.8-42.4%. Tellurium was determined by iodometric titration, and chlorine was determined by potentiometry.

Typically, potassium compounds concomitant with rubidium can also form a precipitate of potassium hexachlorotellurite (K ₂ TeCl ₆ ), but due to the significantly greater solubility of this compound in hydrochloric acid solutions of potassium coprecipitation with rubidium is practically not observed. This is probably also due to the fact that K ₂ TeCl _{6 is} not isomorphic to the corresponding rubidium compound and, in addition, the potassium compound dissolves incongruently.

The method of extracting rubidium from hydrochloric acid solutions by precipitation in the form of rubidium hexachlorotellurite allows to obtain especially pure rubidium salts, purified not only from impurities of similar alkaline elements (K and Na), but also from such as Mg, Al, Fe, and some others.

The method was tested in laboratory conditions with respect to solutions in which potassium, sodium and rubidium were in the form of chlorides.

Example 1. The initial hydrochloric acid solution had chloride concentrations:

RbCl = 70 g / dm ³ ;

KCl = 15 g / dm ³ ;

NaCl = 8 g / dm ³ ,

and was 5.7 n. on hydrochloric acid.

When solid tellurium dioxide was introduced into it (a reagent of the “h” grade was used) in an amount of 150% of the theoretically necessary for the separation of rubidium in the form of Rb ₂ TeCl _{6, the} extraction of rubidium from solution into crystals was 75.6% with a residual concentration of rubidium in solution 11, 96 g / dm ³ .

When used to precipitate rubidium from the same portion of the initial solution of the precipitating solution (prepared by dissolving solid TeO ₂ in 10 N HCl to a tellurium concentration of 100 g / dm ³ ) containing the same amount of tellurium as in the tellurium dioxide used for precipitation, the above, the recovery of rubidium in crystals was 60.6% with a residual concentration of rubidium in solution of 14.2 g / DM ³ .

The results of similar experiments carried out with solutions with the same alkali metal chloride content but different hydrochloric acid concentrations with the same amount of tellurium in the used tellurium dioxide or precipitating solution (180% of the theoretically necessary amount for the precipitation of all rubidium) are shown in the table.

Typically, as expected, the extraction of rubidium in both cases increases with increasing acidity of the medium. With any acidity, when the precipitation of rubidium occurs, the option of using solid tellurium dioxide in comparison with the precipitating solution gives a higher recovery of rubidium. This increase in recovery cannot be explained only by diluting the solution with the introduction of the precipitant in the form of a solution, since in this case (according to the conditions of the experiments), an increase in the residual concentration of rubidium for the precipitating solution would be at the level of 1.2-1.3 times in comparison with the solid tellurium dioxide. It can be assumed that during the reaction with TeO ₂ , fresh active hexachlorotelluric acid is formed, which reacts more fully with rubidium in solution.

The decrease in the acidity of hydrochloric acid medium to a concentration of HCl to 5 N. and less leads to the impossibility of isolating rubidium due to the high solubility of Rb ₂ TeCl ₆ in relatively weakly acidic solutions. In the corresponding experiments, Rb ₂ TeCl ₆ precipitates were not precipitated.

The results of experiments on the precipitation of rubidium from hydrochloric acid solutions of various acidity when using solid tellurium dioxide or precipitating solution to isolate rubidium Experience number The composition of the initial solution, g / l Normality HCl Extraction of rubidium in crystals of Rb ₂ TeCl ₆ ,% The residual concentration of rubidium in solution, g / DM ³ Rbcl Kcl NaCl Introduction TeO ₂ The introduction of a precipitating solution Introduction TeO ₂ The introduction of a precipitating solution one 70 fifteen 8 7 88.7 80.3 5.54 7.07 2 70 fifteen 8 8 93.1 86.1 3.38 4.99 3 70 fifteen 8 9 95 88.5 2.45 4.12 four 70 fifteen 8 10 96.9 92 1,5 2.9 5 70 fifteen 8 11,4 97.6 93.5 1,2 2,3 6 70 fifteen 8 5 - - 49 49

The invention allows to increase the extraction of rubidium by 5-10% from hydrochloric acid solutions in the form of rubidium hexachlorotellurite, to reduce the residual concentration of rubidium in the solution after precipitation of Rb ₂ [TeCl ₆ ] and to improve the separation of rubidium and potassium. The invention allows to simplify and reduce the cost of the method by eliminating the stage of preparation of the precipitating solution.

Claims (1)

A method for extracting rubidium from hydrochloric acid solutions, including its precipitation and crystallization in the form of rubidium hexachlorotellurite, characterized in that the precipitation is carried out from hydrochloric solutions with normal hydrochloric acid in the range of 6-12 N. solid tellurium dioxide at 20-25 ° C with stirring for 3 hours