FR2670803A1 - Process for extracting gallium with substituted hydroxyquinoline - Google Patents

Abstract

Process for extracting gallium with a substituted hydroxyquinoline from basic solution. This extraction is carried out by bringing the basic solution into contact with a water-insoluble material containing a substituted hydroxyquinoline as extractant for gallium. This contact is brought about in the presence of a reducing agent such as hydroquinone, which has a redox potential lower than that of hydroxyquinoline in the mixture considered.

Description

GA LLI UM EX TRA C TI ON PROCESS
SUBSTITUTED llYDROXYQUINOLEIN
The present invention relates to a process for the extraction of gallium using, as extracting agent, a substituted hydroxyquinoline or one of these derivatives.

 It relates more particularly to a process for extracting gallium from a basic solution, such as for example a sodium aluminate solution, from the process for manufacturing alumina.

 We know in particular, from French patents No. 2,277,897, 2,307,407, 2,307,882, 2,495,601, 2,532,295, 2,532,296 a process for recovering gallium present in aqueous alkaline solutions by liquid extraction / liquid by means of an organic phase containing an extractant and an organic solvent, and re-extraction of the gallium by washing the charged organic phase with an acidic aqueous solution.

 It has also been proposed to use a resin to support the extracting agent and extract the gallium by passing the alkaline solution over this resin. Similarly, the gallium is recovered by washing the resin loaded with gallium with an acid solution. Thus, Japanese patent applications No. 60042234 and No. 5896831, European Nos. 258146 and 265356 cite examples of resins which can be used as a support for an extraction agent identical to that used in the liquid / liquid extraction process.

 These liquid / liquid extraction or passage processes on resin containing the extracting agent consist, roughly, in passing the gallium contained in the basic solution, in the medium (organic phase or resin) containing the extracting agent by setting contact of these two environments. In a second stage, the gallium is re-extracted by bringing the medium (organic phase or resin) loaded with gallium into contact with an acidic aqueous solution. The acid solution thus collected can then be purified by numerous methods to remove cations coextracted with gallium, such as for example sodium and aluminum.

By way of example, mention may be made of the purification methods described in French patents Nos. 2,495,599, 2,495,600 and 2,495,601 of the applicant.

 The purified solution is then used as a raw material for the production of gallium metal or compounds containing gallium.

 In these methods, it has been found that the prolonged use of substituted hydroxyquinoline in a gallium extraction unit leads to progressive degradation due in particular to the basic nature of the extraction medium.

 To limit this drawback, it has been proposed to choose a substituted hydroxyquinoline having a saturated hydrocarbon substituent.

 It has also been proposed, in the certificate of addition n02 397 464, to carry out the extraction of gallium under a nitrogen atmosphere to avoid the oxidation of the components of the organic phase, in particular of the substituted hydroxyquinoline.

 The object of the present invention is in particular to propose a process which makes it possible to limit the degradation of the substituted hydroxyquinoline in the processes for extracting gallium, making it possible to complete the result obtained under a nitrogen atmosphere, or even to avoid the use of a nitrogen atmosphere.

 To this end, the invention provides a method of extracting gallium contained in a basic aqueous solution by bringing the aqueous solution into contact with a water-insoluble material mainly comprising at least one hydroxyquinoline substituted as a gallium extracting agent by passage of gallium from the aqueous phase into said material, characterized in that bringing said material into contact with the basic aqueous phase containing gallium is carried out in the presence of a reducing agent having a lower redox potential than that of the extracting agent , substituted hydroxyquinoline, in the medium under consideration, that is to say the basic aqueous solution or the material / basic aqueous solution mixture.

 According to a first embodiment of the invention, the reducing agent is contained in the basic aqueous solution. Thus, this reducing agent can preferably be added to the basic aqueous solution, before it is brought into contact with the material containing the extracting agent.

 According to a second embodiment of the invention, the reducing agent is contained in the material containing the extracting agent.

 In this embodiment, the extracting agent is introduced either in the pure state, or advantageously in the form of a solution produced with a water-soluble solvent such as light alcohols such as methanol, ethanol, for example .

 It is also possible to add this reducing agent directly to the basic aqueous solution / material mixture, or a combination of the various embodiments described above.

 Thus, the reducing agent traps the oxygen present in the system and therefore limits the degradation of the extracting agent.

 The reducing agents suitable for the invention must have a stronger reducing character than that of the extractant in the extraction medium, but also must not disturb or only insignificantly the process for extracting gallium, for example the kinetics of extraction.

The reducing agents suitable for the invention are in particular organic compounds having a redox potential of less than approximately 0.5 V, under the standard conditions of the following reference test.
- "5 mg of test compound are added to acetonitrile containing tetraethylammonium perchlorate at a concentration of 0.1 M and cerium hydroxide at 10-2 M. The zero current potential of the solution is measured with a platinum electrode with respect to a reference electrode Ag / Ag + ".

 They are advantageously chosen from the group comprising hydroxyquinone, pyrogallol, thiobenzamide, phenylhydrazine or a mixture of these.

 When the reducing agent is added to the basic solution containing the gallium, it is advantageously added in an amount sufficient to consume in particular the oxygen contained in the basic solution.

 However, this concentration is preferably between 10-2 mol / l and 0.25 mol / l to, for example, avoid disturbing the gallium extraction conditions. This concentration is also limited by the solubility of the reducing agent in the aqueous solution.

 The substituted hydroxyquinolines suitable for the invention are those which can extract the gallium by complexing under the conditions of the process of the invention, that is to say, in particular in basic medium, and moreover must be soluble in organic medium and insoluble, or significantly less soluble in an aqueous medium.

dans laquelle R1, R2, R3, R4, R5, R6 identiques ou différents sont choisis parmi le groupe constitué par l'hydrogène, les halogènes, les radicaux alkyle, alcényle, alicyclique, aryle ; R1, R2, R3, R4, Rg, R6 ne pouvant représenter simultanément l'hydrogène. Parmi ces hydroxyquinoléines substituées, celles convenant particulièrement bien aux fins de l'invention sont notamment les a-alcényl hydroxy-8 quinoléines, les ss-alcényl hydroxy-8 quinoléines et les alkyl hydroxy-8 quinoléines.Thus, the substituted hydroxyquinolines suitable for the purposes of the invention are in particular those of the following general formula

wherein R1, R2, R3, R4, R5, R6 identical or different are chosen from the group consisting of hydrogen, halogens, alkyl, alkenyl, alicyclic, aryl radicals; R1, R2, R3, R4, Rg, R6 cannot simultaneously represent hydrogen. Among these substituted hydroxyquinolines, those which are particularly suitable for the purposes of the invention are in particular α-alkenyl hydroxy-8 quinolines, ss-alkenyl hydroxy-8 quinolines and alkyl hydroxy-8-quinolines.

dans laquelle R1, R2, R3 représentent un hydrogène ou un groupement hydrocarboné. Parmi celles-ci on utilisera notamment celles de formule générale

The preferred alkenyl hydroxy-8-quinolines according to the invention have the general formula

in which R1, R2, R3 represent a hydrogen or a hydrocarbon group. Among these we will use in particular those of general formula

dans laquelle R1, R2, R3, R4, R5 représentent un hydrogène ou un groupement hydrocarboné.The ss 8-alkenyl hydroxy-quinolines preferred according to the invention have the general formula

in which R1, R2, R3, R4, R5 represent a hydrogen or a hydrocarbon group.

dans laquelle n est compris entre 1 et 20, et, de préférence, entre 5 et 15.The preferred 8 hydroxy alkyl quinolines according to the invention have the formula

in which n is between 1 and 20, and preferably between 5 and 15.

 These hydroxyquinolines can be used according to the invention, alone or as a mixture.

 These extracting agents may be contained in a material formed either by an organic solvent in which the extractant is dissolved, the extraction being carried out according to the process called "liquid / liquid extraction", or by a porous substrate retaining the extracting agent, the extraction being carried out by passing the solution containing the gallium over this porous substrate loaded with extracting agent.

 In the first variant of the process, the extraction solvent is an organic phase containing an organic diluent immiscible with water and one or more extracting agents as defined above.

 Suitable organic diluents usually used are, for example, diluents used in liquid / liquid extraction, used alone or as a mixture. Among these, there may be mentioned aliphatic hydrocarbons such as, for example, heptane and petroleum fractions of the kerosene type; aromatic hydrocarbons such as, for example, benzene, toluene, xylene and cuts of the SOLVESSO type (trademark registered by the company EXXON) and, finally, the halogenated derivatives of these compounds such as, for example, chloroform and tetrachloride carbon, dichloroethane and trichloropropane.

 The proportion of extracting agents in the organic phase is not critical and can vary within wide limits.

 However, a concentration of between 1% and 50% by volume based on the organic phase is generally suitable.

 The organic phase can also contain various additives such as, for example, accelerators of the gallium extraction speed, particulate surfactants. This list is not exhaustive and is given for information only.

 In the second variant of the method, the material consists of a solid and porous substrate on which is chemically or physically fixed, the extracting agent.

 Generally, this substrate can be a synthetic adsorbent or ion exchange resin, such as the resins marketed under the trade names: "Amberlite", the "caged" resins marketed by the company Bayer under the brand "LEWATIT", active carbon or analogues.

 Examples of resins are given in particular in Japanese patents Nos. 60042234, 5896831, European patents 258146, 265356.

 The conditions of concentration, phase ratio, temperature and pH of the extraction of gallium from the basic solution (A) in the extraction material are usual and in particular described in the patents and patent applications cited above.

 The term “basic solution containing gallium” means any basic solution, either artificial or originating from chemical processes such as the treatment of natural minerals.

Thus, the basic solution generally used as a source of gallium is a sodium aluminate solution also called "Detergent
Bayer from the Bauxite ore processing circuit to extract alumina, according to the so-called Bayer process. This basic solution is recycled in the Bayer process circuit after the extraction of the gallium.

 Other objects, characteristics and advantages of the invention will appear more clearly in the light of the examples given below only for information.

Comparative example 1
A basic solution of sodium aluminate containing 93 g / l of aluminum expressed in
Al203 and 79g / l of sodium expressed as Na20, and an extraction solvent comprising 17% by volume of a substituted hydroxyquinoline marketed by the Schering company under the name "Kelex 100" (compound of formula V with n = 11) with a flow rate of 11 / h, 10% decanol and 10.5% versatic acid, the balance consisting of kerosene.

 The system is brought to 700C.

 After 166 hours of operation, the concentration of "KELEX" in the extraction solvent is 11.5%, ie a degradation rate of 30%.

 The concentration of "KELEX" is determined by gas chromatography (GC).

Example 2
Example 1 is repeated, but an aqueous hydroquinone solution at 44 g / l is added to the basic sodium aluminate solution at a flow rate of 0.1 l / h.

 The Kelex concentration did not change after 290 hours of operation.

Example 3
Example 1 is repeated, but an aqueous solution of pyragallol at 15 g / l is added to a basic solution of sodium aluminate at a flow rate of 0.4 l / h.

 The concentration of KELEX in the extraction solvent remained constant after 290 hours of operation.

Example 4
Example 1 is repeated, but adding to the extraction solvent an alcoholic solution (ethanol) of thiobenzamide at 50 g / l at a flow rate of 0.1 l / h.

 Also in this case, it can be seen that the concentration of KELEX remains constant after 290 hours of operation.

Example 5
Example 4 is repeated, but by replacing the alcoholic solution of thiobenzamide with an alcoholic solution of phenylhydrazine at 38 g / l, the same result is observed.

Example 6
In an apparatus consisting of a column filled with resin containing 14.5% by weight (relative to the dry resin) of "KELEX 100", a basic solution identical to that of Example 1 is fed continuously with a flow rate of 100 ml / h.

 The column is brought to 600C.

 After 130 hours of operation, the charge capacity of the resin decreased by 13.8%.

 This load capacity is determined after elution of the resin with a sulfuric acid solution to remove the gallium and regenerate it, then determination of the load capacity with a solution containing copper.

Example 7
Example 6 is repeated, but adding to the basic solution a basic solution an aqueous solution of hydroquinone at 44 g / l at a flow rate of 0.1 l / h.

 The load capacity of the resin determined according to the method described in Example 6 did not decrease after 130 hours of operation.

Claims (14)

R E V E N D I C A T I O N S 1- Method for extracting gallium contained in basic aqueous solutions, consisting in bringing the aqueous solution into contact with a material insoluble in water containing at least one substituted hydroxyquinoline as extracting agent to pass the gallium ions from the phase aqueous in said material, characterized in that the contacting of the material containing the extractant and the basic aqueous phase is carried out in the presence of a reducing agent having a redox potential lower than that of the substituted hydroxyquinoline in the medium considered . 2- A method according to claim 1, characterized in that the reducing agent has a redox potential of less than 0.5 V under the standard conditions of the reference test. 3- A method according to claim 1 or 2, characterized in that the reducing agent is added to the basic aqueous phase. 4- A method according to claim 3, characterized in that the concentration of the reducing agent in the basic solution is between 10-2 mole / l and 0.25 mole / l. 5- Method according to one of claims 1 or 2, characterized in that the reducing agent is added to the material containing the extractant. 6- A method according to claim 5, characterized in that the reducing agent is added in the form of a solution, the solvent being soluble in water. 7- Method according to one of the preceding claims, characterized in that the reducing agent is chosen from the group comprising hydroquinone, pyrogallol, thiobenzamide and phenylhydrazine. 8- Method according to one of claims 1 to 7, characterized in that the material is an organic solvent immiscible with water and comprising an organic diluent in which the extractant is dissolved. 9- Method according to one of Claims 1 to 6, characterized in that the material comprises a porous support into which the gallium extracting agent is introduced. 10- A method according to claim 9, characterized in that the porous support is selected from the group of synthetic resins, activated carbon. 11- Process according to claim 10, characterized in that the synthetic resins are chosen from the group comprising adsorbent or ion exchange resins. 12- Method according to one of claims 1 to 11, characterized in that the extracting agent is a compound belonging to the family of substituted hydroxyquinolines. 13- Process according to claim 12, characterized in that the extracting agent is a substituted hydroxyquinoline whose substituent comprises at least one ethylenic bond. 14- A method according to claim 12, characterized in that the extracting agent is a substituted hydroxyquinoline whose substituent is saturated. 15- Method according to one of claims 12 to 14, characterized in that the extracting agent is a mixture of substituted hydroxyquinolines.