DD298762A5 - METHOD FOR PRODUCING PURE EUROPA OXIDE - Google Patents

Abstract

The invention relates to the production of pure europium oxide in Leuchtstoffqualitaet from rare earth mixtures with 0.01 to 1% Eu2O3 / SE2O3. The erfindungsgemäaesze method is characterized by the enrichment of Eu3 by extraction with acidic phosphoric acid esters, in particular di (2-ethylhexyl) -phosphorsaeure, to 5% Eu2O3 / SE2O3, 2-stage precipitation of * for concentration to 95% Eu2O3 / SE2O3 and subsequent fine cleaning by Ausfaellung According to this method, europium oxide is obtained with 99.99% Eu2O3 / SE2O3, the impurities on other rare earths being in each case 0.002% per element. {pure europium oxide; Fluorescent quality; Seltenerdgemische; Extraction; acidic phosphoric acid esters; *}

Description

Field of application of the invention

The invention relates to the production of pure europium oxide in luminescent quality from rare earth mixtures of natural composition with 0.01-1% Eu ₂ (VSEjOa.

For the production of red phosphors based on Eu ³⁺ activated yttrium oxide or yttrium oxysulfide, europium oxide with> 99.99% Eu ₂ O ₃ ZSE ₂ O _{3 is} required, which simultaneously contains a maximum of 10 ppm Ca, Fe, Mn, Mg, Pb, Ni, Cr may contain.

Characteristic of the known state of the art

Europium is present in most rare earth minerals, which are processed industrially to rare earth compounds or rare earth metals, only in very small amounts. So included

monazite (Australia) 0.07% Eu ₂ CVSE ₂ O ₃ Bastnäsit (UNITED STATES) 0.11% EujO ₃ / SE ₂ O ₃ Rastnäsit (People's Republic of China) 0.2% Eu ₂ O ₃ / SE ₂ O ₃ xenotime (Malaysia) 0.01% Eu ₂ O ₃ / SE ₂ O ₃ apatite (USSR / Kola) 0.5% Eu ₂ O ₃ / SE ₂ O ₃

It is known that europium can be separated in the bivalent state both by precipitation aid and by ion exchange or liquid-liquid extraction of other trivalent rare earths. The properties of the Eu ²⁺ (insoluble sulfate, soluble hydroxide, lower adsorption on cation exchangers, lower extraction by acidic phosphoric acid esters) resembling the alkaline earth metals are exploited.

The separation of europium as europium amalgam by treating solutions with sodium amalgam or by electrolytic reduction at a mercury cathode is also known.

It is known that pure europium oxide can be produced from rare europium-containing rare earth mixtures practically not in one step, but only by many repeated operations or by combining different methods. The separation of traces of trivalent rare earths and the production of pure europium oxide is usually complicated at the end of the process combinations and is associated with sometimes considerable losses in yield.

According to RCVickery, Chemistry of the Lanthanone, London 1953, p. 132, Eu ³⁺ in rare earth chloride solutions containing 0.5% Eu ₂ O ₃ / SE ₂ O _{3 is} reduced with zinc dust and precipitated together with the isomorphous barium sulfate. Concentration to 10% Eu ₂ O ₃ / SE ₂ O _{3 is} achieved. By repeated repetition of the operation further enrichment is achieved, the separation of the last residues of mitausgefällten SE ³⁺ (<0.1%) can not be achieved. In RJ Callow, The Industrial Chemistry of the Lanthanone, Yttrium, Thorium and Uranium, Oxford 1967,158, the separation of europium-D-sulfate / barium sulfate mixtures from rare earth chloride solutions with 300 g / l SE ₂ O ₃ and 0.2 g / l Eu ₂ O ₃ described; although the europium is completely recovered, but only as a concentrate with low Eu content. at

Repetition of reduction and precipitation of europiumdD sulfate is achieved by enrichment to 20% Eu ₂ O ₃ ZSE ₂ O ₃ . By

Concentration to 70% Eu ₂ O ₃ ZSE ₂ O _{3 is} achieved 1-2 repetitions of the operation. The further purification can be carried out by repeated crystallization of EuCl ₂ .2H ₂ O from concentrated hydrochloric acid. However, the last residues of SE ³⁺ can not be separated in this way either.

By A. I. Mikhailichenko, E. B. Michlin and Ju. B. Patrikeyev, rare earth metals (russ.) Moscow 1987,130, the production of Europium oxide with 99.9% Eu ₂ O ₃ described, from the starting material first a rare earth chloride solution with 3-5% Eu ₂ O ₃ ZSE ₂ O _{3 is} produced. By reduction with zinc and precipitation of europium (II) sulfate then enrichment occurs

75-95% Eu ₂ O ₃ ZSE ₂ O ₃ . After conversion to chloride solution (via oxalate to oxide) then reduction with zinc to Eu ²⁺ and

Separation of the SE ³⁺ by precipitation of the latter with ammonia as Seltenero'IIIIJ hydroxides. In the AT-PS 266782, from Seitenerdsulfatlösung with 57g SE ₂ O ₃ ZI, 0.25% Eu ₂ O ₃ ZSE ₂ O ₃ by reduction with zinc and Precipitation of europium (II) sulfate zStrontiumsulfat a concentrate with 26% Eu ₂ O ₃ ZSE ₂ O ₃ obtained. By digesting with 4% Sulfuric acid according to AT-PS 273887 parts of SE ³⁺ dissolved out and enriched concentrate with 58% Eu ₂ O ₃ ZSE ₂ O ₃

to be obtained. By converting the concentrate to chloride solution, reducing it with zinc and precipitating with ammonium sulfate, quite pure europium can be obtained with (II) sulfate. According to US-PS 3,524,723 is from rare earth chloride solution with 100-175g

SE ₂ O ₃ ZI, 0.20-0.25% Eu ₂ O ₃ ZSE ₂ O ₃ by liquid-liquid extraction with solution of 10% di- (2-ethylhexyl) phosphoric acid

(MDEIP) and 90% kerosene and Reextraktion with 4-5 η HCl a europium concentrate with about 7-15% Eu ₂ O ₃ ZSE ₂ O ₃ prepared, the.Dai .ι via reduction and precipitation of europium (II) sulfate to Europium oxide is processed.

C.G. Brown and L.G. Shorrington, Chem. Techn. Biotechnol. 1979, 29, 193-209 describe the enrichment of europium

by extraction from rare earth chloride solution with 20OgZi SE ₂ O ₃ , 0.08% Eu ₂ O ₃ ZSE ₂ O ₃ with solution of 50% VERSATIC ACID (synthetic synthetic tertiary carboxylic acids having 9-11 C atoms) and 50% SHELLSOL A ( Mixture of trimethylbenzenes) and jckextraktion with 3.7 η HCl on concentrate with 5% Eu ₂ O ₃ ZSE ₂ O ₃ . For the separation of 3wertigen rare earth is after

Reduction of Eu ³⁺ to Eu ²⁺ the precipitation of SE (OH) ₃ by boiling with MgO is recommended according to GB-PS 1,143,501. According to GB-PS 1,143,501 becomes from concentrate with 49.5% Eu ₂ O ₃ ZSE ₂ O ₃ pure europium oxide with 30 ppm Nd ₂ O ₃ and presumably

comparable amounts of other impurities to SE oxides. According to US-PS 3,153,571 is from

Rare earth chloride solutions containing at least 11% Eu ₂ O ₃ ZSE ₂ O ₃ by reduction with zinc, sodium amalgam or electrolytic Reduction and treatment with SO ₄ ^2- rare earth contaminated europiumdD sulphate precipitated, this to EuCl ₂ solution

reacted with alkali at pH 8-9.5, the contaminating SE ³⁺ are deposited as hydroxides. From the filtrate, europium oxide is recovered with 99.9% Eu ₂ O ₃ .

According to SU-PS 159811 is in a rare earth nitrate solution with 15OgZI SE ₂ O ₃ , 10% Eu ₂ O ₃ ZI containing 6m LiNO ₃ , EU ³⁺ with zinc to Eu ^{2+ is} reduced, whereupon the trivalent rare earths are extracted by extraction with 100% tributyl phosphate. In DD-PS 261178 traces of europium from rare earth acetate solution are separated by the reduction of Eu ³⁺

takes place electrolytically in the presence of freshly precipitated, finely dispersed, sparingly soluble alkaline earth metal compound. The content of

Europium could be reduced from 0.0026% Eu ₂ O ₃ ZSE ₂ O ₃ to 0.00009% Eu ₂ O ₃ ZSE ₂ O ₃ . The known methods have various shortcomings. Because of the sensitivity of the Eu ²⁺ against oxidation by air must

most operations are carried out under inert gas such as CO ₂ or N ₂ . In the known methods, the

Accessibility of purities of the recovered europium oxides of only 99.9% documented, with impurity

single other rare earths of & 30ppm are given. The processes utilizing the precipitation of europium (II) sulfate for purification require many repetitions to remove the last contaminants. Benivielen method zinc amalgam is used as a reducing agent. This allows traces of mercury to be hauled into all intermediate, end and waste products. Even with the reduction with sodium amalgam there is a risk of carryover of

Mercury. In the process where reduction-precipitation operation on the starting solutions with low levels of Eu ³⁺ directly

is a complete recovery of Eu ³⁺ as a concentrate because of the not insignificant solubility of europium (II) sulfate even in the presence of alkaline earth sulfates !! difficult possible.

The process according to SU-PS 159811 is questionable because Eu ^{2+ is} known to be very easily oxidized by NO ₃ ^- and therefore

legitimate doubts suggest whether reduction of Eu ³⁺ in the presence of large amounts of NO ₃ ^- by zinc is possible at all.

Object of the invention

The aim of the invention is to propose a process for the preparation of pure europium oxide in phosphor quality from rare earth mixtures with 0.01-1% Eu ₂ O ₃ ZSE ₂ O ₃ , which largely avoids the disadvantages associated with the known processes.

Explanation of the essence of the invention The invention has for its object to develop a method which is the production of europium from Rare earth mixtures with low proportions of Eu ₂ O _{3 in} high yields, significantly improved purity and simplified Execution possible. The inventive method for the production of pure europium oxide in phosphor quality from rare earth mixtures

natural composition is characterized by the following process steps:

- From a concentrated rare earth chloride solution having at least 20OgZI SE ₂ O ₃ is by multistage liquid-liquid extraction with extraction agents based on acidic phosphoric esters, especially di (2-ethylhexyllphosphorsäure, the Eu ³⁺ together with Sm ³⁺ and don rare earths with extracted from the atomic numbers 64-71 and Y ³⁺ and separated from the rare earths with the atomic numbers 57-60. From the loaded extractant the Eu ³⁺ together with a part of the co-extracted other rare earths with 2,5-3,5n hydrochloric acid In this process, a rare earth chloride mixture with 5 5% Eu ₂ O ₃ ZSE ₂ O _{3 is} recovered and other SE ³⁺ are reextracted from the extracting agent with 6-8 η hydrochloric acid.

- From the rare earth mixture with ä5% Eu ₂ O ₃ ZSE ₂ O ₃ is by reduction with iron or zinc powder and precipitation of europiumüO sulfate barium sulfate or europiumdD sulfate strontium sulfate mixtures with barium chloride or strontium chloride and ammonium sulfate or sulfuric acid at S 3O ⁰ C. the Eu ³⁺ completely separated and recovered as a concentrate with 80% EujO ₃ / SE ₂ O ₃ .

After working up the europiumdD sulphate concentrate with S80% Eu ₂ O ₃ ZSE ₂ O ₃ to corresponding europium chloride solution is reduced with zinc powder at 7O-80 ° C, being adjusted by hydrochloric acid addition, a pH of S4. By addition of sulfuric acid at 25 ^° C., europium (II) sulfate with 95 95% Eu ₂ O ₃ ZSE ₂ O ₃ , preferably S 98% Eu ₂ O ₃ , is precipitated. From the filtrate containing the trivalent rare earths and Zn ²⁺ , the SE ³⁺ precipitated as oxalates.

The europiumdD sulphate with a 95% Eu ₂ O ₃ ZSE ₂ O ₃ is converted by treatment with sodium carbonate to europium (II, III) carbonate, which is dissolved to give the corresponding europium chloride solution in hydrochloric acid. After reduction of the Eu ³⁺ with zinc with addition of hydrochloric acid at pH S 4 and 60-70 ⁰ C, the trivalent rare earths are precipitated with excess ammonia as hydroxides and separated from the ammoniacal solution of europium (II) chloride and zinc chloride. From this solution, the europium (III) hydroxide is precipitated after oxidation of the Eu ²⁺ with air, hydrogen peroxide or nitric acid, which can be burned in a known manner directly or via the isolation of europium oxalate to europium.

The inventive method is carried out so that to ensure the secure prevention of reoxidation of the Eu ²⁺ in all sub-stages, an overlay of the aqueous reaction solutions with inert organic liquids takes place, which are not miscible with uen aqueous solutions. For this purpose, in particular high-boiling (Kp 3 18O ⁰ C) are suitable paraffinic hydrocarbons such as decane, white spirit or paraffin paraffin.

The recovery of zinc in the process according to the invention is achieved by precipitating europium (III) hydroxide from the filtrate and precipitating rare earth oxalates Zn ²⁺ from the filtrates by addition of the stoichiometrically required amount of phosphoric acid at pH values of 7. 8 is precipitated as zinc ammonium phosphate.

Ausführungsbelsplel

In a 20-stage mixer-settler extractor cascade, a weakly acidic rare earth chloride solution (pH = 2) with 20OgZi SE ₂ O ₃ (15.4% La ₂ O ₃ , 57.7% CeO ₂ , 3.8% Pr ₆ O ₁₁ , 13.4% No ₂ O _3, 2.2% Sm ₂ O _3, 0.53% of Eu ₂ O _3, ⁰ 1.4 AGd ₂ O _3, 0.16 ⁰ ATb ₄ O _7, 0.69% of Dy ₂ O ₃ , 0.10% Ho ₂ O ₃ , 0.17% Er ₂ O ₃ , 2.7% Y ₂ O ₃ ) with a 50% solution of di (2-e <hylhexyl) phosphoric acid in one Treated paraffinic hydrocarbon mixture (Kp = 185-22O ⁰ C) in such a way that in 6 stages in countercurrent medium and heavy rare earths extracted by washing) with 1 η HCl from the organic phase in 4 stages with extracted light rare earths reextracted and the main amount of europium were reextracted by washing with 3n HCl from the organic phase in a further 4 stages. When washing with 3N HCl, a rare earth chloride solution with 5OgZi SE ₂ O _{3 was} obtained, which based on the sum of the rare earth oxides 0.15% La ₂ O ₃ , 19.2% CeO ₂ , 3.8% Pr ₆ O ₁₁ , 22, 7% Nd ₂ O ₃ , 23.0% Sm ₂ O ₃ , 6.0% Eu ₂ O ₃ , 15.4% Gd ₂ O ₃ , 1.8% Dy ₂ O ₃ , 0.17% Ho ₂ O ₃ , 0.14% Er ₂ O ₃ and 1.85% Y ₂ O ₃ . Thus, 96.7% of the Eu contained in the starting material was recovered as a concentrate. In a further 5 stages, the rare earths remaining in the organic phase were reextracted with 7 η HCl to give an yttrium concentrate which contained only 0.15% Eu ₂ O ₃ ZSE ₂ O ₃ . The obtained hydrochloric rare earth chloride solution with 50g SE ₂ O ₃ /! and 6.0% Eu ₂ O ₃ in SE ₂ O ₃ was largely evaporated to remove the excess hydrochloric acid. By dissolving in water, 4500 ml of solution with 680g SE ₂ O ₃ were prepared. The solution was added under stirring at 3O ⁰ C with 30 g of iron powder.

Within 60 min 110 ml of 25% hydrochloric acid were added dropwise, over the surface of the solution, an N ₂ atmosphere was maintained. Undissolved portions of iron powder were then separated and the solution was added under inert gas within 20 min while stirring with 510 ml of 10% ammonium sulfate solution. Subsequently, 365 ml of a 10% solution of BaCl ₂ .2H ₂ O were added dropwise with stirring. The precipitated mixture of europium-D-sulfate-potassium sulfate was filtered off and washed with 100 ml of water. With 10% nitric acid, the europiumdD sulfate was oxidized and dissolved; undissolved barium sulfate was filtered off. From the solution (2000 ml) crude Europiumoxalat was precipitated after blunting the excess acid with oxalic acid, which was subsequently filtered off and burned to oxide. 47.5 g of rare earth oxide with 84.3% Eu ₂ O _{3 were obtained} . In the filtrate after separation of the europium-D-sulfate / barium sulfate mixture 0.026% Eu ₂ O ₃ ZSE ₂ O ₃ were still included. Thus,> 99% of the Eu contained in the used and enriched in Eu ²⁺ rare earth erythroid solution was obtained as 84.3% europium oxide. "-

The rare earth oxide (47.5 g SE ₂ O ₃ , 84.33% Eu ₂ O ₃ ) was dissolved in hydrochloric acid and diluted to 850 ml with water. After the solution had settled to pH 4.0, it was filtered off from deposited Fe (OH) ₃ . The Fütrat was added at 65 ⁰ C under exclusion of air with 20g zinc dust (<0.5mm). Within 30 min 25 ml of 25% HCl were stirred with stirring. The solution was then overlaid with 30 ml of n-decane to prevent ingress of air and cooled to 25 ° C with slow stirring. The solution was then added at 25 ⁰ C with 40 ml of 65% sulfuric acid within 25min. The precipitated europiumdD sulfate was filtered off and washed with 2 x 50 ml of water. Obtained were 80 g of wet europiumdD sulfate with 40.5 g of SE ₂ O ₃ with 98.3% Eu ₂ O ₃ . The filtrate contained 6.7 g of SE ₂ O ₃ with 3.2% Eu ₂ O _3. The 80 g of the europium sulfate with 98.3% of Eu ₂ O ₃ in SE ₂ O ₃ were slurried in 200 ml of water and heated to 1500 ml 92 ⁰ C hot solution of 60g technical soda and 60ml 50% sodium hydroxide solution registered. Then it was heated to boiling for 30 min. The resulting mixture of Europiumdl) -Europium (III) carbonate was filtered off, washed with 2 x 100 ml of water, slurried in 500 ml of water and brought into solution by adding 95 ml of 25% HCl. The acid solution (pH = 1.1) was added to complete reduction of the Eu ³⁺ to Eu ²⁺ at 65 ⁰ C with 15g zinc dust and stirred for 20 min. Then 15 ml of 25% hydrochloric acid were added dropwise within 30min. The solution was then overlaid with 30 ml of n-decane. Undissolved zinc was filtered off. The filtrate with the floating n-decane was added at 72 ⁰ C with gentle stirring with 200ml of 25% ammonia water. After standing for 15 minutes, the precipitated hydroxides of the trivalent rare earths were removed very quickly by filtration. In the filtrate was oxidized by introducing air at 80 ⁰ C Eu ²⁺ and precipitated as europium (lll) hydroxide. The europium (III) hydroxide was filtered off and washed well with deionized water.

After drying, the following were obtained:

45.8% europium (III) hydroxide with 66.0% sum of the SE ₂ O ₃ ,> 99.99% Eu ₂ O ₃ ZSE ₂ O ₃ , <0.001% La ₂ O ₃ , <0.0018% CeO ₂ , <0.0007% Pr ₆ O ₁₁ , <0.0006% Nd ₂ O ₃ , <0.0005% Sm ₂ O ₃ , <0.002% Gd ₂ O ₃ , <0.002% Tb ₄ O ₇ , <0.001 % Dy ₂ O ₃ , <0.0005% Ho ₂ O ₃ , <0.002% Tm ₂ O ₃ , <0.001% Yb ₂ O ₃ , <0.002% Y ₂ O ₃ , <0.0001% Fe ₂ O ₃ , <0.001% Cu, Mn, Mg, Pb, Ni, Cr

The precipitated hydroxides of the trivalent rare earths contained 5.0 g of SE ₂ O ₃ with 77.9% Eu ₂ O ₃ . All filtrates containing Zn ²⁺ were made by adding stoichiometric amounts of phosphoric acid and ammonia

to pH 7.5 this as zinc ammonium phosphate (ZnNH ₄ PO ₄ ) won.

Claims (2)

1. A process for the preparation of pure europium oxide in Leuchstoffqualität from rare earth mixtures with ^ 1% Eu ₂ O ₃ , characterized by the process steps - Enrichment by liquid-liquid extraction with extractants based on acidic phosphoric acid esters from chloride solution and reextraction of the gone into the organic phase Eu ³⁺ with 2,5-3,5η hydrochloric acid to obtain a rare earth chloride mixture with S 5% Eu ₂ (VSE ₂ O ₃ Reduction of Eu ³⁺ in the obtained rare earth chloride mixture with iron or zinc powder and precipitation of europium (II) sulfate and boronium sulfate by addition of ammonium sulfate and barium chloride solution to obtain europium concentrate with 80 80% Eu ₂ O ₃ ZSE ₂ O ₃ Reduction of Eu ³⁺ in the europium concentrate in chloride solution with zinc powder and precipitation of europium O-sulfate with sulfuric acid to obtain europium (II) sulfate with δ 95% Eu ₂ O ₃ / SE ₂ O ₃ - Implementation of the europium (II) sulfate on europium carbonate to Europiumohloridlösung, reduction of Eu ³⁺ to Eu ²⁺ with zinc powder, precipitation of SE ³⁺ with ammonia as rare earth (III) hydroxides, separation of hydroxides from the ammoniacal europium (II ) chloride solution, oxidation of Eu ²⁺ with precipitation of europium (III) hydroxide and separation of the latter from the ammoniakalisohen I ohloridlösung - Implementation of europium (III) hydroxide in a known manner to europium oxide with> 99.99% Eu ₂ O ₃ / SE ₂ O ₃ 2. The method according to claim 1, characterized in that is used as the phosphoric acid ester di (2-ethylhexyl) phosphoric acid.