FI70693B - FOER FARING FOER RENING AV EN GALLIUMLOESNING - Google Patents

Description

70693

The present invention relates to a process for the purification of gallium hydrochloric acid-aqueous solution, which contains e.g. ferrous iron, for purification by liquid-liquid extraction using an extractant to obtain a highly pure gallium chloride solution.

In various applications of gallium, especially in the field of electronics, it is necessary to obtain gallium in a very pure form. Thus, it proves necessary to have methods which, from gallium solutions which do not meet the desired purity requirements, make it possible to obtain gallium solutions with a purity of more than 99.99%, from which gallium oxide or gallium metal of the required purity can be obtained very easily.

It is known to carry out the separation of gallium from certain metal cations using certain solvents, e.g. tertiary amines. However, the separation of gallium from various elements, and especially from ferric iron, has so far proved impossible without first reducing iron to ferrous form / (Chemical Abstracts Volume 92 (1979) 94 35c7 ·

Disproving the technical assumption that the separation of gallium from ferric iron in particular by solvent extraction using solvents is very difficult in the preparation of very pure gallium, the present invention has developed a method for purifying gallium solutions which allows excellent purification of these solutions in various elements, especially ferric iron. . This method provides for the selective extraction of gallium from a solution containing various elements, especially ferric iron, using gallium extractants which are insoluble in water, such as alcohols or quaternary ammonium salts.

The process according to the invention is characterized in that 1) an aqueous solution of gallium hydrochloric acid having a free acid content of between 1 and 8 N is contacted with an organic phase containing an extractant containing quaternary ammonium chloride or an alcohol having up to 10 carbon atoms, 2) the resulting organic the phase containing gallium and the extractant is separated from the aqueous phase containing impurities, 3) the separated organic phase is washed to remove residual impurities with a solution of gallium hydrochloric acid having an acid content of 5-8 N when the extractant is quaternary ammonium chloride and quaternary ammonium chloride, , having an acid content of less than 6 N when the extractant is an alcohol, 4) the gallium is transferred from the obtained organic phase to the water phase by contacting the organic phase with water, and 5) the aqueous phase containing purified gallium chloride is recovered by separation.

According to the process of the invention, the gallium solution is contacted with an organic phase containing a water-insoluble gallium extractant and, if necessary, an inert diluent, so that the gallium is selectively extracted into the organic phase.

The gallium hydrochloric acid solutions which can be purified by the process according to the invention to produce very pure solutions can be of quite different origins. They have a free hydrochloric acid content of between 1 and 8 N, preferably between 2 and 6 N. They may also contain mixtures of hydrochloric acid with other acids such as sulfuric acid or perchloric acid.

Il 3 70693 The nature and quantity of impurities contained in these solutions can vary widely and may consist of cations of various metals of the Periodic Table of the Elements, in particular the following metals: calcium, magnesium, aluminum, vanadium, chromium, copper, manganese, sodium, zinc, cobalt, nickel, lead, cadmium, indium, barium, strontium, potassium, titanium, lanthanides, yttrium, arsenic, iron (especially in ferric form), phosphorus, tin, boron and the like cations.

In addition, the gallium content of these solutions can vary within very wide limits, for example from about 500 mg / l to about 300 g / l.

The alcohols used in the process of the invention preferably contain from 4 to 10 carbon atoms, being substantially immiscible in water and sufficiently fluid to prevent problems in the process. Examples of such alcohols are pentanol, n-butanol, isobutanol, cyclohexanol, n-hexan-1-ol, 2-ethylhexanol, n-heptanol, n-octanol, iso-octanol, n-decanol and isohexanol. Most preferably, 2-ethylhexanol alone is used, i.e. undiluted.

The quaternary ammonium salts which can be used as an extractant in the process according to the invention are in particular those of the formula R 1 N-CH 2 Cl, in which R is a hydrocarbon radical containing 8 to 10 carbon atoms. Such preparations are available in particular under the trademarks Adogen 464 and Aliquat 336.

The relative proportion of extractant in the organic phase is not critical and can vary within wide limits. In general, however, it is preferred that this proportion be as high as possible. Thus, in the case of quaternary ammonium salts, a proportion of between 3 and 30% by volume of the organic phase results in preferred hydrodynamic purification conditions. In the case of alcohols, the least viscose can be used in the organic phase alone, i.e. undiluted, and this is particularly advantageous because it can lead to quite considerable extraction capacities and keep the liquid volumes and thus the size of the equipment to a minimum. The relative proportion of alcohols generally ranges from 10 to 100% by volume of the volume of the organic phase.

If necessary, the organic phase may also contain a diluent. Among the diluents commonly used in the field of liquid-liquid extraction, mention may be made of aliphatic compounds (particularly suitable in connection with the use of an alcoholic extractant) such as heptane, dodecane, hexane and petroleum fractions, aromatic compounds such as benzene, toluene, ethylbenzene, and Solvesso-type fractions (Solvesso is a registered trademark of Exxon) and halogen derivatives of said compounds such as chloroform and carbon tetrachloride.

The aqueous phase is separated from the gallium-containing organic phase, and this organic phase is subjected to a selective wash to remove residual impurities which have been present in small amounts with the gallium.

Depending on the extractant used, this selective washing is preferably carried out as follows:

If the extractant is an alcohol, the organic phase is contacted with water or a hydrochloric acid solution, preferably at a concentration of less than about 6 M. The impurities then transfer to the washing solution, while the organic phase retains the purified gallium.

If the extractant is quaternary ammonium chloride, the organic phase is contacted with a hydrochloric acid wash solution having an IlCl content of 5 M to 8 M and containing 1 to 50 g / l of gallium, 3 to 10 g / l of suitable pyramine. the molten solution may be, for example, a mixture comprising, on the one hand, a hydrochloric acid solution, preferably at a concentration of between 7 M and 12 M, and, on the other hand, a part of the final purified aqueous solution of gallium chloride.

The spent wash solution, which contains impurities and a small amount of gallium, can be suitably recycled together with the original hydrochloric acid solution of gallium to bring it back under purification measures.

The purified gallium is then transferred from the organic phase to the aqueous solution by contacting the purified organic phase with water in the selective washing step described above.

Finally, the organic phase is separated from the aqueous phase. The resulting aqueous phase contains pure gallium in the form of gallium chloride with a purity of even more than 99.99%.

Extraction, selective washing, and gallium recovery can be performed in conventional equipment used in liquid-liquid extraction processes. Such devices generally comprise a plurality of zones of mixer-beaker systems or packed and / or stirred columns arranged to perform extraction, selective washing and recovery of the extracted element from the aqueous phase.

In a preferred embodiment, the gallium solution treated in the above-mentioned step (1) is the product of the purification itself, starting from the aqueous gallium solution. The treatment comprises: a) adjusting the concentration of chloride ions in an acidic aqueous solution of gallium to a value between about 3.5 M and 8 M, if necessary; b) contacting the gallium solution with a strongly basic type of ion exchange resin, the resin attaching the gallium; c) washing the resin, if necessary, with a hydrochloric acid solution having a concentration greater than or equal to about 5 M; d) eluting gallium from the resin with water to provide a concentrated aqueous solution of gallium chloride; and e) adjusting the concentration of chloride ions in the resulting solution to a value between about 4 M and 6 M.

The most efficient methods for separating gallium from impurities have previously used ion exchange resins. However, the separation of gallium from certain metal ions such as calcium, magnesium, aluminum, cobalt, vanadium, copper, manganese, sodium, zinc and especially ferric iron ions proves to be deficient when using selective attachment of gallium from the solution to be purified to the anion exchange resin. 21974 IV /. To solve the purification problem in the presence of ferric iron, it has been proposed to reduce iron to ferric form before transporting the solution over the resin (Chemical Abstracts, Volume 55 (1961) 21974 V and Volume 74 (1971) 108688 k). However, such a procedure has the fundamental disadvantage that it does not allow adequate purification of the gallium solution.

By treating impure gallium solutions according to steps (a) to (e) and then according to steps (1) to (5), it is possible to achieve excellent purity in the presence of various elements, especially iron. This method comprises a combination of essentially the following steps: attaching gallium in solution to an ion exchange resin which provides a first purification, then concentrating the gallium solution eluted from 7,70693 resin, and finally steps (1) to (5) of the present invention to purify the resulting solution from liquid-liquid. by extraction using a solvent which is insoluble in water and which selectively extracts the galum.

Aqueous gallium acid solutions that can be purified according to the preferred method of this invention to provide solutions of very high purity can be of very different origins. They are preferably solutions of at least one sour acid: hydrochloric acid, sulfuric acid and perchloric acid.

The nature and amount of impurities contained in these solutions can vary widely and can consist of ions from different metals of the Periodic Table of the Elements, as exemplified above in the case of aqueous solutions of gallium hydrochloric acid. In addition, the concentration of gallium in these solutions can vary within very wide limits. However, this process according to the invention is particularly advantageous for the purification of dilute gallium solutions with a concentration of, for example, less than about 10 g / l.

This preferred process of the invention is particularly suitable for the purification of aqueous solutions produced by a process for recovering gallium from sodium aluminate solutions prepared by the Bayer process, as described in particular in FR Patents 2,277,897, 2,307,047 and 2,307,882, FR Patent Application 76 / 29009 and in FI patent application 78222 and in European patent application 78/4 002 222.

In step (a), the concentration of chloride ions in the gallium solution is adjusted, if necessary, to a value between about 3.5 M and 8 M, preferably between 4.5 M and 6 M. This concentration is best adjusted by adding hydrochloric acid to the gallium solution. It is also possible to perform this adjustment on β 70693 by adding any chloride that is not attached to the resin in the next step. Suitable chlorides include alkali metal and alkaline earth metal chlorides.

In step (b), the gallium solution is contacted with an ion exchange resin of a strong base type and gel-like or macrorross-linked in nature, the resin attaching the gallium very selectively, probably substantially in the form of an anionic complex GaCl 2. Resins that can be used are especially those containing the formula ^ (CH3) 2 1 + R-N, or the formula

--CH_-OH

L ^ _ ”+ R-N -CH3 ^ CH3 where R is, for example, a styrene / divinylbenzene or acrylic / divinylbenzene copolymer. Examples of products to be used are products available under the trademarks: Dowex 1, Duolite A 101 D, Duolite A 42, Lewatit M 500, Amberlite IRA 400, Amberlite IRA 410, Amberlite IRA 900, Amberlite IRA 910 and Permutit ESB (A) .

These generally have an attachment capacity of about 80 to 120 g of gallium per liter of resin. After attachment, the gallium-loaded resin is washed in step (c), if necessary, with a hydrochloric acid solution, preferably at a concentration of greater than or equal to 5 M, to remove impurities retained by the resin with gallium.

The gallium is then recovered in step (d) by eluting the resin with water. This produces a concentrated and purified solution of 9,70693 gallium chloride, usually with a gallium content of about 40-60 g / l and a free acid content of about 1 M -2 M.

Despite a fairly substantial purification, the gallium is considerably concentrated compared to the original impure solution. This concentration is particularly advantageous for the subsequent solvent extraction purification as well as for the purification efficiency and the size reduction of the equipment allowed by the concentration.

The concentration and purification step with the resin can be carried out in conventional equipment and in particular by placing the resin on columns connected in series.

In step (e), the concentration of chloride ions in the resulting solution is adjusted to about 4 M to 6 M in the same manner as described above, preferably by adding hydrochloric acid to the solution. The product can then be treated according to steps (1) to (5) of the present invention.

The following examples illustrate the invention without limiting its scope.

Example 1

Gallium chloride solution (G) having the following composition:

Ga: 40 g / l

HCl: 5.6 N

Ai: 5 mg / l

Na: 3 mg / l

Fe 3+: 800 mg / l

Ca: 10 mg / l

Mg: 2 mg / l

Cr: 1 mg / l V: 1 mg / l

Cu: 0.4 mg / l

Mn: 1 mg / l

Zn: 2 mg / l is purified.

xo 70693 This solution is contacted with the organic phase (S) in 2-ethylhexanol. This step is carried out, according to the apparatus shown in Figure 1, in a multistage liquid-liquid extractor (A) which operates on the countercurrent principle and contains 30 theoretical stages. 2-Ethylhexanol is fed to the apparatus in stage 1 at a flow rate of 100 ml / h. The gallium solution is introduced into the apparatus at stage 11 at a flow rate of 145 ml / h. Selective washing is performed by passing a 0.5 N hydrochloric acid solution (HCl) at 30 degrees at a flow rate of 45 ml / h.

The aqueous phase (E) emptied from stage 1 contains impurities and less than 100 mg / l gallium, which corresponds to an extraction rate greater than 99.5%.

The gallium-loaded 2-ethylhexanol leaving device (A) is fed to a 5-stage device (B), where gallium chloride (GaCl 2) is recovered in aqueous solution by contacting (S) with water (water) on a countercurrent basis at a flow rate of 95 ml / h. This produces a GaCl solution having the following composition:

Ga: 59.6 g / l

Ai ^ 0.2 mg / l

Na (0.05 mg / l

Fe (0.1 mg / l

Ca (0.05 mg / l

Mg (0.05 mg / l

Cr (0.1 mg / l

Cu (0.1 mg / l

Mn (0.05 mg / l

Zn (0.05 mg / l

The purity of the resulting solution is thus greater than 99.99%. Example 2 In this example, reference is made to Figure 2.

tl 70 69 3

Gallium chloride solution (G) having the following composition:

Ga: 53 g / l

HCl: 6 N

Ai: 3 mg / l

Na: 25 mg / l

Fe 2+: 650 mg / l Ca: 1.5 mg / l

Mg: 1 mg / l

Cr: 0.6 mg / l V: 0.2 mg / l

Cu: 0.4 mg / l

Mn: 0.4 mg / l

Zn: 1.6 mg / l

Pb: 0.1 mg / l is purified.

This solution (G) is contacted with an organic phase (S) consisting of a 6% solution of tricaprylmethylammonium chloride (available under the trademark Aliquat 336 in the form of chloride) in Solvesso 150 (registered trademark of Exxon).

This step is carried out in a multistage liquid-liquid extractor (A), which operates on the countercurrent principle and comprises 12 theoretical stages. The organic phase (S) is fed to the apparatus in stage 1 at a flow rate of 2540 ml / h. The gallium solution (G) is introduced into the apparatus in stage 6 at a flow rate of 300 ml / h. Selective washing of the charged organic phase is performed in steps 6-12 with the washing solution (W) described below.

The organic phase leaving the device (A) containing purified gallium is then fed to stage 1 of a apparatus (B) of 5 theoretical degrees, in which the gallium is re-extracted with water entering stage 5 at a flow rate of 1270 ml / h of a gallium chloride solution containing 14 g / l of gallium. in terms of.

70693 12 This solution is removed at 635 ml / h and forms the product, while 635 ml of solution / h is combined with a 12 M HCl solution at a flow rate of 635 ml / h to form a washing solution (W) which is fed to stage (A) 12.

The solution (E) emptied from the device (A) contains impurities and less than 50 mg / l of gallium, so that more than S9% of the gallium has been extracted.

The purified gallium solution has the following composition:

Ga: 14 g / l

Ai (0.2 mg / l

Na (0.05 mg / l

Fe (0.1 mg / l

Ca (0.05 mg / l

Mg (0.05 mg / l

Cr (0.1 mg / l V <0.05 mg / l

Cu (0.1 mg / l

Mn (0.05 mg / l

Zn 0.05 mg / l

Pb (0.05 mg / l corresponding to a purity of more than 99.99% with respect to gallium.

Example 3 126 liters of a gallium sulfuric acid solution produced by a process for recovering gallium from sodium aluminate solutions prepared by the Bayer method according to the process described in European Patent Application 78/4222222.

This solution has the following composition and contains various impurities in the following concentrations: 70693 13

Ga: 3.2 g / l

H2SO4: 4 M

A1: 4.1 g / l

Na: 1.8 g / l

Fe 3+: 350 mg / l

Ca: 60 mg / l

Mg: 30 mg / l

Cr: 7 mg / l V: 280 mg / l

Cu: 80 mg / l

Mn: 3 mg / l

Zn: 4 mg / l

Pb: 2 mg / l

The concentration of chloride ions in this solution is adjusted to 4.5 M by adding 76 liters of 12 M hydrochloric acid.

Two columns, each containing 2.25 liters of quaternary ammonium resin (supplied by Dia-Prosim under the trademark Duolite A 101 D), are then continuously fed with the resulting solution at a flow rate of 1.2 l / h.

After the first column is saturated with gallium, i.e. after 202 liters of feed solution have passed through it, it is isolated and washed with 10 liters of 6 M hydrochloric acid solution.

The gallium attached to the resin is then eluted with 3.8 liters of water at a flow rate of 1 l / h to give a solution of gallium chloride (GaCl 2) having the following composition:

Ga: 53 g / l V: 0.2 mg / l HCl: 1.1 M Cu: 0.4 mg / l

Ai: 3 mg / l Mn. 0.4 mg / l

Na: 25 mg / l Zn. i, 6 mg / l

FeJ: 640 mg / l

Pb: 0.1 mg / l

Ca: 1.5 ml / l

Mg: 1 mg / l

Cr: 0.6 mg / 1,70693 14 Concentration of the original gallium solution and considerable initial purification have thus been achieved. The main remaining impurity is ferric iron (Fe 2+).

The concentration of chloride ions in the resulting solution is adjusted to 5.4 M by adding 2.5 liters of 12 M hydrochloric acid.

This solution is then contacted with the organic phase of 2-ethylhexanol. This step is carried out, according to the apparatus shown in Figure 3, in a multi-stage liquid-liquid extractor (A) operating according to the counter-current principle and comprising 40 theoretical stages. 2-Ethylhexanol (S) is fed to the apparatus in stage 1 at a flow rate of 510 ml / h. The gallium solution (G) is introduced into the apparatus at stage 10 at a flow rate of 300 ml / h.

Selective washing is performed by passing to 40 degrees 2 M hydrochloric acid solution (HCl) at a flow rate of 90 ml / h.

The aqueous phase (E) leaving stage 1 contains all impurities and less than 100 mg / l gallium, which corresponds to an extraction ratio of more than 99.5%.

The gallium-loaded 2-ethylhexanole leaving the device (A) is fed to a 5-stage device (B), where the gallium is recovered in aqueous solution by contacting (S) with water on a countercurrent basis at a flow rate of 320 ml / h. This gives a solution of gallium chloride (GaCl 2) having the following composition:

Ga: 30 g / l V (0.05 mg / l

Ai (0.2 mg / l Cu (0.1 mg / l

Na (0.05 mg / l Mn (0.05 mg / l

Fe (0.1 mg / l Zn (0.05 mg / l

Ca (0.05 mg / l Pb (0.05 mg / l

Mg (0.05 mg / l

Cr (0.1 mg / l

II

15 70693

Thus, the purity of gallium in the resulting solution is greater than 99.99%.

Example 4

The solution obtained according to Example 3 is used after passing it over the resin. Its composition is:

Ga: 53 g / l

HCl: 1.1 M

Ai: 3 mg / l

Na: 25 mg / l

Fe 2+: 650 mg / l

Ca: 1.5 mg / l

Mg: 1 mg / l

Cr: 0.6 mg / l V: 0.2 mg / l

Cu: 0.4 mg / l

Mn: 0.4 mg / l

Zn: 1.6 mg / l

Pb: 0.1 mg / l

Reference is now made to Figure 4. The chloride ion concentration is adjusted to 6 M by adding 3 liters of 12 M HCl solution to give a gallium chloride solution (G). This solution is contacted with an organic phase (S) consisting of a 6% solution of tricaprylmethylammonium chloride (available under the trademark Aliquat 336 in the form of chloride) in Solvesso 150 (registered trademark of Exxon1).

This step is carried out in a multistage liquid-liquid extractor (A), which operates on the countercurrent principle and comprises 12 theoretical stages. The organic phase (S) is fed to the apparatus in stage 1 at a flow rate of 2540 ml / h. The gallium solution (G) is introduced into the apparatus in stage 6 at a flow rate of 300 ml / h. Selective washing of the charged organic phase is performed in steps 6-12 with the washing solution (W) described below.

16 70693

The organic phase leaving the apparatus (A) containing purified gallium is then fed to stage 1 of a apparatus (B) of 5 theoretical degrees, in which the gallium is re-extracted with water entering stage 5 at a flow rate of 1270 ml / h of a gallium chloride solution containing 14 g / l of gallium. in terms of.

This solution is removed at 635 ml per hour and forms the product, while the 635 ml / h solution is combined with a 12 M HCl solution derived at a flow rate of 635 ml / h to form a washing solution (W) which is fed to stage 12 of the apparatus (A).

The solution (E) emptied from the device (A) contains all the impurities and less than 50 mg / l of gallium, so that more than 99% of the gallium has been extracted.

The purified gallium solution has the following composition:

Ga: 14 g / l

Ai \ 0.2 mg / l

Na (0.05 mg / l

Fe (0.1 mg / l

Ca (0.05 mg / l

Mg (0.05 mg / l

Cr (0,1 mg / l V (0,05 mg / l

Cu (0.1 mg / l

Mn (0.05 mg / l

Zn (0.05 mg / l

Pb (0.05 mg / l corresponding to a purity of more than 99.99% with respect to gallium.

Il

Claims (7)

17 Claims 7 0 6 9 3 A process for the preparation of an aqueous solution of gallium hydrochloric acid, comprising e.g. ferric iron, for purification by liquid-liquid extraction using an extractant to obtain a highly pure gallium chloride solution, characterized in that an aqueous solution of gallium hydrochloric acid having a free acid content of 1 to 8 N is contacted with an organic phase containing an extractant containing is quaternary ammonium chloride or an alcohol having up to 10 carbon atoms, 2. the resulting organic phase containing gallium and extractant is separated from the aqueous phase containing impurities, 3. the separated organic phase is washed to remove residual impurities with a solution of gallium hydrochloric acid N , when the extractant is quaternary ammonium chloride and with water or a hydrochloric acid solution with an acid content of less than 6 N when the extractant is alcohol, 4. gallium is transferred from the organic phase obtained to the water phase by contacting the organic phase with water, and 5. ve the siphase containing purified gallium chloride is recovered by separation. Process according to Claim 1, characterized in that the free acid content of the aqueous solution of gallium hydrochloric acid is between 2 and 6 N. Process according to Claim 1 or 2, characterized in that the alcohol used as extractant is 2-ethylhexanol. Process according to Claim 1 or 2, characterized in that the quaternary ammonium chloride used as extractant has the formula R 3 NCH 3 + Cl, in which R is a hydrocarbon radical containing 8 to 10 carbon atoms. Process according to Claim 4, characterized in that the quaternary ammonium chloride is present in the organic phase in an amount of 3 to 30% by volume of the organic phase. 18 70693 Process according to one of Claims 1, 2, 4 or 5, characterized in that the washing solution is an aqueous hydrochloric acid solution having an acid content of between 5 and 8 N and containing 1 to 50 g / l of gallium, preferably 3 to 10 g / l. . Process according to Claim 6, characterized in that the washing solution is a mixture consisting of a hydrochloric acid solution, preferably at a concentration of between 7 and 12 N, and a part of the final purified aqueous solution of gallium chloride.