IE59640B1

IE59640B1 - Process for the recovery of gallium by liquid-liquid extraction

Info

Publication number: IE59640B1
Application number: IE233287A
Authority: IE
Original assignee: Rhone Poulenc Chimie
Priority date: 1987-05-06
Filing date: 1987-08-31
Publication date: 1994-03-09
Also published as: FR2614887A1; IN170892B; AU606153B2; EP0290318B1; NO881951L; PT87418B; CN88102672A; ATE85035T1; KR930003637B1; KR880014123A; AU1561588A; CN1017215B; FR2614887B1; DE3877813T2; JPS6465023A; BR8802170A; EP0290318A1; JPH0463811B2; PT87418A; DE3877813D1

Abstract

The process consists in extracting, in a liquid-liquid extractor 1, the gallium present in a basic solution of sodium aluminate (Bayer liquor) by means of an extractant known under the tradename of Kelex, dissolved in an organic solvent. The organic phase containing the gallium is subjected to a first liquid-liquid extraction 2 by means of an acidic solution to remove, to at least a large extent, aluminium and sodium and then to a second liquid-liquid extraction 3 by means of another acidic solution to recover gallium. This acidic gallium solution is purified by extraction of gallium with an extractant at 4. After the extraction of gallium the acidic solution is recycled to the extractor 2 to reduce the usage of acid in the process.

Description

PROCESS FOR THE RECOVERY OF GALLIUM BY LIQUI 0-L I QU I D EXTRACTION The present invention relates to a profess for the recovery of gallium by liquid-liquid extraction, from very basic aqueous solutions containing gallium, such as, for example, sodium aluminate liquors from the BAYER process for the manufacture of alumina.

A process for the recovery of gallium present in alkaline aqueous solutions by liquid-liquid extraction using an organic phase containing an extractant and an organic solvent, and a process for the purification of the gallium solution which enables, in particular, some of the cations such as, for example, the aluminium and sodium cations coextracted with gallium, to be removed from the aluminate liquors mentioned above, are known, in particular, from French Patent Applications No. 2,277,897, 2,307,047, 2,307,882, 2,495,601, 2,532,295, 2,532,296.

This process consists in causing the gallium contained in the strongly basic solution to move into the organic extraction phase by a liquid-liquid extraction process. In a second stage, this organic phase is treated with a first acid solution in order to extract selectively at least a part of the aluminium ana sodium cations coextracted with gallium. This stage enables the organic phase to be impoverished for cations other than gallium and therefore to reduce the concentration of impurities in the acid solution of gallium obtained in the third stage. This third stage is an extraction or recovery of gallium contained in the organic phase by treating with a second acid solution.

The acid solution of gallium thereby obtained also contains other metal ions and in particular, for example, aluminium and sodium ions which were not extracted during the treatment of the organic phase with the first ac id solut ion.

Many processes have been proposed for the removal of these metal ions and especially, by way of example, the processes described in French Patent Nos. 2,495,599, 2,495,600 and 2,495,601 of the Applicant Company.

These processes consist either in treating the gallium solution by passing it through a strongly basic type of ion exchange resin, or in extracting the gallium by a liquid-liquid extraction, it being possible for the extractants to be, for example, quaternary ammonium salts and alcohols.

The gallium solution obtained may then be subjected to further purification stages.

The final solution of gallium is then treated by different processes in order to produce gallium metal with a very high purity or alloys of gallium with other compounds .

The process described above enables a gallium solution with a very high purity to be obtained with very good extraction and recovery yields. However, the second „ stage of the process, viz. the treatment of the organic phase with an acid solution, requires the consumption of / < a large quantity of acid solution which is discarded as effluent after use, as is the acid solution recovered 5 after selective extraction of gallium. These large volumes of liquid effluents are a disadvantage as they require a treatment before their disposal and this increases the cost of the process.

The object of the present invention is, in par10 ticular, to overcome these disadvantages by providing a process which enables, on the one hand, acid consumption to be reduced and on the other hand, the quantity of effluents discarded to be reduced significantly. Thus, the invention enables the economic value of the process to be improved substantially.

To this end, the invention provides a process for the recovery of gallium contained in very basic aqueous solutions by liquid-liquid extraction using an organic phase mainly consisting of an extractant and an organic solvent, which consists of the following stages: (i) extracting gallium from the very basic solution with the organic phase mentioned above, (ii) washing the said organic phase containing / gallium with a first acid solution inorder to extract thereby the cations present in the organic solution at least partially and selectively with respect to gallium. (iii) extracting gallium from the said organic phase washed with a second acid solution, (iv) adjusting the concentration of hali'de ions in the acid solution of gallium obtained in stage (iii), (v) selectively extracting gallium from this acid solut ion and (vi) recovering the gallium thereby extracted, characterized in that the first acid solution employed in stage (ii) consists of at least a part of the acid solution recovered in stage (v) after the selective extraction of gallium.

The different stages (i) to (vi) have already been described in many patents and in particular in French Patent Application Nos. 2,277,897, 2,307,047, 2,307,882, 2,495,601, 2,532,295 and 2,532,296, the specifications of which form an integral part of the present application.

Thus, the washing of the organic solution containing gallium (stage ii) is carried out according to a Z0 countercurrent liquid-liquid extraction process with a first acid solution having a H+ ion concentration and a feed rate such that the H+ ion concentration of the acid solution in contact with the organic solution entering the countercurrent extraction stage (ii) is less than approximately 1, preferably between 0.1 and 1 and advantageously between approximately 0.2 to 0.7.

As acids suitable for implementing the invention, there may be mentioned, by way of examples, inorganic acids such as sulphuric acid, phosphoric -acid, nitric acid and hydrochloric acid.

However, when the extraction is carried out in 5 the presence of chloride ions, a H+ ion concentration greater than 1N may be chosen on condition that the concentration of chloride ions is at least equal to 4 M.

Thus, the chloride ion concentration may be between 4 and 12 M, advantageously between 4 and 6 M, the H+ ion concentration advantageously being between 4 and 6 N.

In stage (iii) consisting of the extraction of gallium from the organic phase with a second acid solution, the extraction is also carried out according to a counter15 current liquid-liquid extraction process. As in stage (ii) above, the feed rate and the H+ ion concentration of the second acid solution are fixed so as to have a fixed H+ ion concentration in the acid solution in contact with the organic solution entering stage (iii).

Thus, this H+ ion concentration must be greater than 1.5 N, preferably between approximately 1.5 and 6 N and advantageously between approximately 3.5 and 4.5 N.

However, if the acid solution contains chloride ions, the chloride ion concentration must be less than approximately 2.5 M.

The stage Cv) consisting of the selective extraction of gallium from the acid solution may be carried ~2» out according to many processes already described in ' patents and publications.

There may be mentioned, by way of example, liquidliquid extraction processes which employ, as extractant, one or more solvating agents such as, for example, ethers, ketones, alcohols, esters or organophosphorus compounds, or anionic extractants such as, for example, amines or quaternary ammonium salts.

It is also possible to extract gallium selectively by passing the acid solution of gallium through an ion exchange resin. The resins suitable for implementing the invention are those of the basic type which are capable of retaining gallium certainly in the form of the anionic z _ complex GaX , X representing halogen, preferably chlorine or bromine and advantageously chlorine.

There may be mentioned, by way of example, the resins described in French Patent No. 2,495,601 and which contain the units of formulae: (CH,), R-H CH,-CH,-QK or ZCH3 R-N—CH. \ 3 CH3 in which R represents, for example. a styrene/divinylbenzene or acrylic/divinylbenzene copolymer. For example. the products marketed under the names: Dowex 1, Dowex 2, Dowex 3, Duolite A 101 D, Duolite A 42, Lewatit M 500, Amberlite IRA 400, Amberlite IRA 410, Amberlite' IRA 900, Amberlite IRA 910, Duolite A 14, Amberlite IR 45 are em5 ployed.

The organic phase employed in stage (i) comprises an extractant which is preferably a substituted hydroxyquinoline, for example 7-(5,5,7>7-tetramethyl-1-octen3-yl)-8-hydroxyquinoline, the hydroxyquinolines marketed under the names Kelex 100 by Schering or LIX 26 by HENKEL Those described in particular in French Patent Nos. 2,277,897, 2,307,047, 2,307,882, 2,532,295 and 2,532,296, Japanese Patent No. 60,042,234, 59,186,683 and 59,500,24 and European Patent No. 199,905 may also be employed as the organic phase. More generally, the invention may be implemented with any organic phase which enables gallium to be extracted according to a process comprising stages (i) to (vi) mentioned above.

Briefly, the organic phase comprises the extrac20 tant, a solvent, for example kerosine, one or more compounds containing alcohol groups such as higher alcohols or higher phenols as well as other solvating compounds such as some phosphoric esters. It is also advantageous to add compounds which accelerate the speed of extraction of gallium, such as compounds containing at least one carboxylic acid group, organophosphorus compounds or sulphates or substituted sulphonates.

The concentration of extracting agent is not critical and it is generally of the order of 10%.

It is also possible to employ, as organic phase, a polymer filled with a substituted hydroxyquinoline as described in Japanese Application No. 6,042,234, stages (ii) and (iii) of the process becoming operations of eluting the filled polymer.

Japanese Application No. 59,186,683 describes the use of a mixture of substituted hydroxyquinolines, viz. a mixture of 7-alkyl-8-hydroxyquinoline and 7-(5,5,7,7tetramethyl-1-octen-3-yl)-8-hydroxyquinoline.

Therefore, the invention enables acid introduction in stage (ii) to be reduced or even completely avoided.

In fact, at least the major part of the solution for washing the organic phase consists of the acid solution recovered in stage (v).

This reduction in total acid consumption enables the profitability of the process to be improved and the quantity of liquid effluents discarded to be reduced significantly.

The recycling of the acid solution in stage (ii) does not affect the extraction yield, in particular, of the aluminium and sodium-cations, in this stage.

According to another feature of the invention, the adjustment of the halide ion concentration in stage (iv) is carried out by adding a metal halide, either in the solid form or as a solution, advantageously concentrated, or hydrochloric acid in the gaseous form or • as a concentrated solution.

Advantageously, and in particular, when- the adjustment of chloride concentration is carried out by ad5 ding a metal halide, the entire acid solution recovered after the selective extraction of gallium (stage v) is recycled in stage (ii) which consists of washing the organic phase.

In this variant, liquid effluent output is re10 stricted to the minimum and only occurs in stage (ii).

In stage (iv), the concentration of halide ions » is adjusted to a value of between approximately 3.5 M and M.

This adjustment is carried out, in a known manner, 15 either by adding a halogenated acid in the gaseous form or as a concentrated solution, or by adding metal halides, advantageously alkali metal or alkaline earth metal halides.

As halide ions preferred for implementing the invention, there may be mentioned chlorides and bromides, the chloride ion being advantageously preferred.

Sodium chloride is preferably chosen as the metal * halide, particularly when the strongly basic solution containing gallium is a sodium aluminate solution originating from the BAYER process for the preparation of alumina.

According to another feature of the invention, the concentration of H+ and Cl~ ions and the rate of recycling of the acid solution recovered in stage (v) are monitored and adjusted if required in order to comply with the values for the concentration of H+ and Cl"'ions in stage (ii) described above.

The figure attached and the examples given below illustrate the invention.

The single figure shows a block diagram sketch of the process of the invention.

Example 1 A countercurrent liquid-liquid extraction battery 1 is supplied, through the pipe 6, with 1/000 I of an organic phase with the following composition by weight: Kelex 100 8Z n-decanol 10Z versatic acid 5X keros in 77Z 1,000 I of a decomposed solution of sodium aluminate resulting from a Bayer process for the manufacture of alumina is also supplied. This solution contains, in particular:A12°3 82 g/i Na,0 166 g/i Ga 240 mg/1 The decomposed solution, after mixing with the organic phase and separating the latter, is drawn off through the pipe 11, for example, in order to recycle it into the BAYER process. After treatment,- this solution has the following composition: Al203 80 g/l 5 Na20 156 g/l G 3 80 mg/l The concentrations of gallium, alumina and sodium oxide in the organic phase are as follows: AI2O3 2 g/l NajO 10 g/l Ga 160 mg/l The organic phase is then fed into a countercurrent liquid-liquid extractor 2 through the pipe 6a.

The washing of the organic phase is carried out 15 with an acid solution supplied through the pipe 16 and originating from stage (v) implemented in the extractor 4.

In this extractor 2, 1,000 I of the organic phase mentioned above is brought into contact with 60 I of the acid solution originating from the extractor 4 and 40 I of water.

This acid solution has an H2SO4 concentration of 2 moles/litre and an HCl concentration of 4 moles/litre.

After stirring and separating the phases, the organic phase recovered through the pipe 6b contains: 160 mg/l G 3 A12O3 N320 0.05 g/l 0.1 g/l The acid solut ion evacuated through the pipe 12 contains: - - G a 10 mg/l - A12O3 13.9 g/l Na20 70.7 g/l LH*] 0.4fr N LC l"] 2.9 M The organic phase collected at the outlet of the extractor 2 is supplied through the pipe 6b into an ex- tractor 3 in which it is mi xed wi th 100 I of an acid sol ution supplied through the pipe 7 and having an H2SO4 concentration of 4 moles/l.

After stirring and separating the phases, the organic phase is evacuated through the pipe 6c towards a liquid-liquid extractor battery 5 in which it will undergo several washings with water before being recycled into the extractor 1 through the pipe 6, after adding fresh organic solvent through the pipe 6d if required.

The acid solution recovered contains: Ga 1.6 g/L AI2O3 0.5 g/L Na20 1 g/L CH*] 4N This solution also contains many other metal cations, the concentrations of which are of the order of 10 to 200 mg/l.

Before extracting gallium from this solution in the extractor 4, the chloride ion concentration in the latter is adjusted to a value of 4 M by a-d ding hydrochloric acid through the pipe 8.

This solution is supplied through the pipe 15 at a rate of 1l/h into columns containing 0.6 I of Duolite A 101 resin which is of the quaternary ammonium type.

The acid solution recovered through the pipe 16 contains: Ga 10 mg/l H2SO4 2 moles/l HCl 4 moles/l A12Ο3 0.5 g/ I Na20 0.1 g/L 60% of this acid solution is recycled through the pipe 16 into the extractor 2, this solution thus forming the solution for washing the organic phase.

Thus, the major part cf the acid supplied in the process of the invention is first used for extracting gallium from the organic phase (extractor 3) and then for washing the organic phase by the extraction, in particular, of aluminium and sodium in the extractor 2 before being evacuated as effluent through the pipe 12. This dual use of the acid solution represents a significant saving for the process, both in terms of the consumption of acid reagents and in terms of effluent treatment.

The gallium retained on the resin in the extractor 4 is recovered by eluting the resin with water (1 l/h) supplied via the pipe 13 and recovered via the pipe 14.

The solution obtained contains: G 3 52 g/l ai2o3 5‘mg/I Na20 20 mg/l Fe 100 mg/l other metal cations of the order of a few mg/l This concentrated solution of gallium may then be subjected to successive purifications according to known methods such as, for example, liquid-liquid extraction and treatment with resins.

These purification operations are of a very low cost as the volume of solution to be treated is low because of the high gallium concentration.

Example 2 This example is identical to Example 1 except that the acid solution supplied through the pipe 7 into the extractor 3 contains 5 moles/l of sulphuric acid.

The solution collected at the exit of the ex- tractor 3 contains: Ga 1.6 g/l AI2O3 0.8 g/l » Na20 1.5 g/l H2S04 2.5 moles/l 1 The chloride concentration in this solution is adjusted to a value of Cl of 4 H by adding a sodium chloride solution.

The new solution contains: G a Al203 1.33 g/l 0.67 g/l 1.2 g/l Na20 5 H2S04 2.1 moles/l NaCl 4 M This solution is supplied to the ion exchange resin columns in a manner identical to that in Example 1. The acid solution collected at the column outlet 10 conta ins : G a < 10 mg/l H2S04 2.1 moles/ I NaCl 4 M Al203 0.8 g/l 15 Na20 0.15 g/l The whole of the solution is recycled in stage (ii) into the extractor 2 in order to wash the organic phase and to extract aluminium and sodium therefrom at least part ially.

The acid solution collected through the pipe 12 contains: Ga < 10 mg/t AI2O3 16 g/l Na20 83 g/l [ H + J 0.3 N c c 1 "□ 3.8 M The solution containing gallium collected after ·' eluting the resin contains: Ga 50 AI2O3 5 NajO 15 Fe 150 other metal cations of Example 3 g/t mg/l mg/l mg/l the order of a few mg/l.

This example differs from Examples 1 and 2 in that the acid solution supplied to the extractor 3 has a hydrochloric acid concentration of 1.8 N.

The aqueous phase collected from the outlet of the extractor 3 contains: Ga 0.64 g/l Al203 0.2 g/i NaaO 0.4 g/i HCl 1.8 N Fe 0.1 g/i Gallium is extracted from this solution by a liquid-liquid extraction process using, as extractant, a quaternary ammonium salt marketed by HENKEL under the name Aliquat 336, dissolved in a solvent marketed under the name Solvesso 150, at a concent rat ion of 0.1 M.

This extraction is carried out in a battery of liquid-liquid extractors assembled in series.

The acid solution of gallium is fed into an intermediate extractor simultaneously with a 12 N hydrochloric acid solution. The extractant solvent is washed on exit from the battery with a 6 N hydrochloric acid solution.

The gallium is re-extracted from the extractant solvent by washing with water.

The aqueous solution leaving the extractor battery has a hydrochloric acid concentration of 6 N. 60Z of this solution is recycled into stage (ii) through the pipe 16 in order to wash the organic phase. The acid solution collected through the pipe 12 contains: Ga < 10 mg/l AI2O3 8 g/l Na^O 40 g/l CH+] 5.1 N CCI] 5.9 M Thus as in Examples 1 and 2, the acid solution employed for extracting gallium from the organic phase (stage iii) is also employed for washing this organic phase in order to extract aluminium and sodium therefrom.

Claims

1. A process for the recovery of gallium contained in very basic aqueous solutions by liquid-liquid extraction using an organic phase mainly comprising an organic extractant and an organic solvent, which comprises the following stages: (i) extracting the gallium from the very basic solution with the organic phase mentioned above, (ii) washing the said organic phase containing gallium with a first acid solution in order to extract therefrom at least partially and selectively with respect to gallium the cations present in the organic solution, (iii) extracting gallium from the said organic phase washed with a second acid solution, (iv) adjusting the concentration of halide ions in the acid solution of gallium obtained in stage (iii), (v) selectively extracting gallium from this acid solution and (vi) recovering the gallium thereby extracted wherein the first acid solution employed in stage (ii) consists of at least a part of the acid solution recovered in stage (v) after the selective extraction of gallium.

2. A process according to claim 1, in which the first acid solution comprises the whole of the acid solution recovered in stage (v).

3. A process according to claim 1 or 2, in which the concentration of halide ions in stage (iv) is adjusted to a value of between 3.5 M and 8 M.

4. A process according to claim 1, 2 or 3 in which the adjustment of the halide ion concentration in stage (iv) is carried out by adding hydrochloric acid in the gaseous form or as a solution, or metal halides in the pure form or as a solution.

5. A process according to claim 4, in which the metal halides are alkali metal chlorides or alkaline earth metal chlorides.

6. A process according to claim 5, in which the metal halide is sodium chloride.

7. A process according to one of the preceding claims, in which the acid solution of gallium leaving stage (iii) has a H + ion concentration greater than 1.5 N, the halide ion concentration is not greater than 2.5 N and the acid solution leaving stage (ii) has a H + ion concentration less than 1 N.

8. A process according to one of claims 1 to 6, in which the acid solution of gallium leaving stage (iii) has a H + ion concentration greater than 1.5 N, the halide ion concentration is not greater than 2.5 N and in that the acid solution leaving stage (ii) has an H + ion concentration greater than 1 N and a halide ion concentration not less than 4 M. I - 20 Jr

9. A process according to claim 8 in which the acid solution leaving stage (ii) has a halide ion concentration i, between 4 and 6 M.

10. A process according to claim 7, 8 or 9 in which 5 the acid solution leaving stage (iii) has a H + ion concentration of between 1.5 and 6 N.

11. A process according to any one of claims 7 to 10, in which the H + ion concentration in the acid solution of gallium leaving stage (iii) is between 3.5 and 4.5 N. 10

12. A process according to any one of claims 1 to 11, in which the concentration of H + and halide ions in the acid solution is monitored after stage (v) before it is recycled into stage (ii).

13. A process according to any one of claims 1 to 12 15 in which the extractant is a substituted hydroxyquinoline, a derivative thereof or a mixture of the latter.

14. A process according to any one of claims 1 to 13 in which the selective extraction of gallium in stage (v) is carried out by passing the acid solution of gallium through a basic ion exchange resin.

15. A process according to one of claims 1 to 13, in which the selective extraction of gallium in stage (v) is carried out by liquid-liquid extraction, and the extractant » is an anionic agent or solvating agent. ί 25

16. A process for recovery of gallium substantially as hereinbefore described in any of Examples 1 to 3.

17. Gallium when recovered by the process of any one of claims 1 to 16.