SU1000470A1 - Method for recovering europium - Google Patents

Description

(54) METHOD OF ALLOCATION OF EUROPE

one

The invention relates to the rare metal industry and the industrial density of chemical reagents and can be used in nonferrous metallurgy, rare metal production, nuclear technology, in the production of chemical reagents, etc.

Methods are known for isolating individual rare earth elements from mixtures by ion exchange, extraction, phase exchange of solutions of salts of rare earth elements with alkali metal amalgams, electrolysis on liquid and solid cathodes f l Also known is a method of separating europium from a solution of a mixture of salts of rare earth elements by electrolysis on a liquid cathode. The process is conducted from sulphate solutions at the mercury cathode 2.

The disadvantage of this method is the use of metallic mercury, the vapors of which are toxic and harmful to the body. In addition, during the electrolysis of salt solutions r.z. elements, along with europium, partial recovery of samarium and ytterbium ions to a bivalent state occurs, which also form poorly soluble compounds

with sulfate ions and precipitate, thereby preventing the process of complete separation of europium from mixtures of rare earth elements.

The purpose of the invention is to improve working conditions, speeding up the process while maintaining a high degree of European emission.

The goal is achieved

10 in accordance with the method of separating europium from a solution of a mixture of salts of rare-earth elements by electrolysis on a liquid cathode as a solution of a mixture of salts of rare-earth elements

15 elements use citrate solution and the process is carried out in the presence of a phosphate-containing compound; an indium-gallium cathode and electrolysis are used as a liquid cathode.

20 is carried out at a cathode potential of −1.9 V relative to a saturated calomel electrode.

A phosphate-containing compound is used in an amount that ensures the ratio of europium ions and phosphate ions (1-1.5): (1-3).

The method is carried out in an electrolytic cell, which is a housing divided by a permeable diffractor into a cathode and anode space. 25 ml of a decimolar citrate solution of r.s. elements and potassium phosphate with a pH of 8, and the ratio should be in the range of (1-1.5) :( 1-3). At smaller ratios, an incomplete distribution of europium from a mixture of r.s. elements due to the lack of PO ions; at large, the degree of use of electricity for side processes (thermal heating of the electrolyte, etc.) increases dramatically. An indium gallium eutectic is used as the cathode. and, as an anode, a platinum wire. The area of an indium gallium cathode is 12.4 cm. Nitrogen O, CO2, is sparged to stir the electrolyte. and H2O, through a solution placed in the cathode gap. The potential of the indium-gallium cathode is kept constant, equal to 1, 9 in a relatively saturated calomel electrode (N.C.E.) during the entire time of electrolysis. At more positive potentials of the indium gallium cathode, the recovery rate Eu is significantly reduced. At more negative potentials, the concomitant effect of the hydrogen reduction process at the cathode increases, thereby significantly reducing the yield. As a result of electrolysis, the reduction of Eu occurs, which forms a poorly soluble salt with ions present in the solution in the form of a fine suspension, which does not block indium-gallium the cathode and thus does not prevent the complete recovery process to go to It. Others elements, including samarium and ytterbium, remain in solution and can be separated from Eu, (PO4) i by filtration. The efficiency of the process can be characterized by two parameters: the degree of completeness of the desired product, in this case Europe, or the selectivity of the process, which is achieved in the proposed invention by the rapid release of the desired product, i.e. time spent in the selection of the target product. The fulfillment of the target task according to the first parameter is also possible at other cathode potentials, namely from -1.7 to -2.2 V relatively n .k more positively and more negatively than which the process is restored, 1 and Ei almost ceases. However, with a more positive potential of the indium gallium cathode than -1.9 V relative to BC, the recovery rate is significantly reduced. A decrease in the rate of recovery of Eu leads to an increase in the time required for the release of a certain amount of europium. A similar result is obtained when the cathode potentials are more negative than -1-, 9 V relative to the ke ke, with the only difference that in this case the decrease in the E yield is explained by an increase in the recovery rate of hydrogen ions on indium carbon dioxide. gallium cathode. Thus, the choice of the potential of the cathode as a single value is dictated by the experimental results obtained. Citrate solutions were chosen because the reduction of the r.z. ions from solutions of simple salts on the indium gallium cathode practically do not flow due to the low pH value (rJl,}., as a result of which only hydrogen ions are reduced. An increase in pH leads to the precipitation of hydroxides of the elements of the earth. Rz. ions in an aqueous solution can be in the alkaline region () only in the presence of a complexing agent, which citric acid in this case performs. As for the possibility of using other complexing agents, it should be noted that As a result of ethylenediaminoacetic acid, nitrilotriacetic acid, sodium pyrophosphate, etc., the reduction rate of Eu decreases to the release of the latter in the form of Eiz (PO4). Therefore, the proposed complexing agent, citric acid, allows in this case to achieve the optimal recovery rate by isolating the latter in in the form of Eu-bCPO;) The use of PO4 as a precipitator is based on its property to form, under these conditions in the electrolyte, a fine suspension that does not block indium gallium first cathode and thereby prevents leakage Eu complete reduction process when using other precipitants RZ ions in the divalent state, for example C.7P4 Co | etc., it is not possible to achieve complete isolation of Europe. In one case, this is coupled with the formation of a precipitate on the surface of the cathode, in connection with which it is blocked, as observed in the presence of ions. When used, for example, a poorly soluble compound is formed.

Eu, which is probably due to the inability to achieve the solubility of the compound under these conditions. Thus, the use of ions as a precipitator in this case corresponds to the purpose of the invention.

The invention has the following advantages. Instead of toxic mercury, a liquid indium-gallium alloy is used as the cathode, thereby improving occupational safety. In contrast to the prototype on the indium-gallium cathode, only the restoration of It takes place, while the others. The ions do not undergo changes, which allows increasing the selectivity of the separation of euphPI from other s. elements in citrate solutions. For example, during the electrolysis of citrate solutions of Eu containing ions in the presence of an indium gallium electrode for 10 min. isolate Eu (PO4) 7. with the content of trace impurities of other rivers. elements less than 0.1%. To achieve the same result in the prototype method, it is necessary to at least twice carry out the process of electrolytic separation of these elements.

Isolation of europium from a mixture of r. elements of the proposed method occurs with significantly less time. Thus, electrolysis of citrate solutions (C 16 g / l Lrf) of a gadolinium concentrate containing, according to spectral analysis data, 5.1% europium, 0.22 g Eit, (ROF) was separated off on an indium gallium cathode, which it is 28.8% europium (in terms of metal) from the original. A similar result in the prototype method is achieved in 3540 minutes of electrolysis.

Electrolysis of Europium Citrate Solutions in Mix with Others the elements on the indium gallium cathode make it possible to more completely isolate europium, since the resulting europium (II) phosphate is in solution in suspension and does not block the indium gallium cathode. During electrolysis using the prototype method, europium sulphate, precipitating on the mercury cell, blocks its surface, the more it prevents further, more

complete restoration of Ei to Her

Claims (2)

1. A method for separating a europium from a solution of a mixture of salts of the earth-like elements by electrolysis. liquid cathode, characterized in that, in order to improve working conditions, increase the selectivity of the release of the target product and accelerate the process, citrate solution is used as a solution of a mixture of salts of rare-earth elements and indium is used as a liquid cathode. Gallium cathode and electrolysis are carried out at a cathode potential of –1.9 V relative to a saturated calomel electrode. 2, the method according to claim 1, characterized by the fact that the phosphate-containing compound is used in an amount that ensures the ratio of ions europium and phosphate ions (1-1,5): (1-3). Sources of information taken into account in the examination 1. Zelikman A.N. and others. Metallurgists of rare metals. M., Metallurgists, 1978, p. 514-529. 2.Serebrennikov V.V. Chemistry of rare-earth elements, Tomsk, Tomsk University Press, 1961, Vol. 2, p. 408, 424, 425.