FI68421B - FOERFARANDE FOER SEPARERING AV JAERN FRAON ETT ORGANISKT EXTRAKTIONSMEDIUM - Google Patents

Description

NOTICE OF PUBLICATION 684 21

l J '1Ί ^ UTLÄGG NI N GSSKRIFT

C ¢ 45) Patent granted 10 C9 1985 Patent meddelat * (51) Kv.lk. * / Lnt.CI.4 C 22 B 3/00, 23/04 FINLAND * —FINLAND (21) Patent application - Pitenunsöknlng 792679 (22) Application date - Amökningidag 29 08 79 (Fl) * '(23) Starting date - Giltighetjdag 29 08 79 (41) Made public - Blivit offentlig g ^ g ^ gg

National Board of Patents and Registration Date of sight and publication. -,. ‘No’

Patent-och registerstyrelsen '' Ansökan utlagd och utl.skriften publicerad Jl.Up.öb (32) (33) (31) Privilege requested - Begird priority 08.09.78 09.1 1.78 Japan-Japan (jp) 53-109603, 53-137283 (71) Nippon Mining Co., Ltd., 2-10-1 Toranomon, Minato-ku, Tokyo 107, Japan-Japan (JP) (72) Takashi Ogata, Ibaragi, Teruo Tamanoi, Saitama, Japan-Japan (JP) (74) Oy Jalo Ant-Wuorinen Ab (54) The present invention relates to a process for treating an organic extraction medium for a liquid extraction process, in particular to a process for separating iron from an organic extraction medium, in which an organic extraction medium is used. an extractant containing essentially a monoalkyl ester of an alkylphosphonic acid wherein the alkyl group contains 8 to 10 carbon atoms.

The liquid extraction process is used for the selective extraction of certain metals in hydrometallurgy. With regard to the extractant, it must be taken into account that the extractant is less soluble in the aqueous solution containing the metal to be extracted and that it can selectively and efficiently extract the metal in question from the aqueous solution. The extractant must be highly soluble in the diluent as the extractant is diluted with the diluent for use as an organic extraction medium.

Di-2-ethylhexylphosphoric acid (D2HPA) is known as a cobalt extractant, which has the disadvantage that it is only poorly able to selectively extract cobalt and nickel, as shown below: Cobalt remains in aqueous solution with nickel during cobalt extraction, preventing

68421 2

On the other hand, nickel also becomes extracted in the organic extraction medium together with cobalt when the cobalt is completely extracted from the aqueous solution. Thus, nickel and cobalt cannot be efficiently separated by liquid extraction in the prior art.

In contrast to the prior art, the present invention relates to a process wherein the extractant of the organic extraction medium is an alkylphosphonic acid monoalkyl ester having 8 to 10 carbon atoms in the alkyl group.

The liquid obtained by dissolving said extractant in a diluent such as kerosene, mineral oil or the like is hereinafter referred to as an "organic extraction medium".

This organic extraction medium has excellent extraction properties when selectively extracting cobalt from solutions containing cobalt and nickel, such as extraction solutions, process effluents or the like. The aqueous phase containing cobalt and nickel and the organic extraction medium are contacted with each other in a stirred settler, extractor, centrifugal extractor or the like, which acts as a step prior to the process of the present invention. The optimum contact temperature varies between 20 and 80 ° C and the volume ratio between the aqueous phase and the organic extraction medium varies between 10: 1 and 1:10.

In the liquid extraction process, the organic extraction medium is used repeatedly until its extraction properties deteriorate, as a small amount of iron dissolved in the aqueous phase or from the equipment accumulates in the organic extraction medium. On the other hand, it has been found that such accumulation of iron causes a considerable reduction in the cobalt extraction capacity in relation to the amount of iron accumulated. On the other hand, there is a considerable increase in viscosity when the ferrous organic extraction medium extracts cobalt, which is a more serious drawback. This increase in viscosity causes various difficulties and obstacles in the process, such as during pumping, mixing or pipeline transport, e.g. for valves. For this reason, the iron accumulated in the organic extraction media of the extraction process must be removed in order to maintain uniform extraction properties and uniform extraction capacity.

It is an object of the present invention to provide a new method for separating iron from an organic extraction medium capable of selectively extracting cobalt.

It is also an object of the present invention to provide an improvement in the extraction process in which the organic extractant can be regenerated and reused.

According to the present invention, the organic extraction medium is contacted with an alkali hydroxide solution or a mixed solution of an alkali hydroxide and a monosaccharide, a disaccharide, a polyhydric alcohol and / or the like. This invention relates to a process for the separation of iron from an organic extraction medium comprising a diluent and an extractant, the main part of which is an alkylphosphonic acid monoalkyl ester of the formula O, P, OH (I)

1 I

R 2 wherein R 1 and R 2 represent one or two alkyl groups having 8 to 10 carbon atoms, wherein said organic extractant is contacted with an alkali hydroxide solution.

Iron that has passed from the extraction medium to the alkaline aqueous solution tends to precipitate to form iron hydroxide, which often causes operational difficulties, but the presence of a saccharide or the like in the alkaline aqueous solution can effectively prevent precipitation by forming a chelate. Accordingly, the present invention relates to a process for separating iron from an organic extraction medium comprising a diluent and an extractant substantially containing a monoalkyl ester of an alkylphosphonic acid of formula I, which process comprises contacting said organic extraction medium with a mixed solution of a polyhydric acid, an alkali hydroxide and a monosaccharide .

It has been shown that the amount of cobalt remaining in the organic extraction medium affects the separation efficiency of iron and the separation of iron is accelerated if cobalt is removed beforehand. Thus, the present invention relates to a process for separating iron from an organic extraction medium as described above, wherein said organic extraction medium is first contacted with a mineral acid solution to remove cobalt therefrom, then said organic extraction medium is contacted with an alkali hydroxide solution and a mixed solution of an alkali hydroxide or the like.

The accompanying figure shows graphically the relationship between chelating power and sucrose content when the organic starting extraction medium, if any, is treated with a mixed solution of 68421 4 sodium hydroxide and sucrose. The ordinate shows the chelating power (%) of iron as a defined ratio (chelated iron content in the filtrate) / (iron content in the organic starting extraction medium), the abscissa shows the sucrose content of the mixed solution of alkali hydroxide and sucrose. Each curve corresponds to the iron concentrations in a given organic starting extraction medium.

The present invention uses an organic extraction medium consisting essentially of monoalkyl esters of alkylphosphonic acid of formula I, wherein R 1 and R 2 represent an alkyl group having 8 to 10 carbon atoms. As R 1 and R 2, i.e. as the alkyl group having 8 to 10 carbon atoms, one or two alkyl groups belonging to the following examples or combinations thereof may be used: (C8 as an alkyl group) 2-ethyl-1-hexyl-, 4-methyl-1-heptyl-, 1-octyl- , 3-ethyl-2-methyl-3-pentyl group or the like; (C 8 as alkyl group) 3,5,5-trimethyl-3-hexyl, 3-ethyl-5-methyl-3-hexyl, 1-nonyl, 2-methyl-2-ethyl group or the like; (C 1-4 alkyl group) isodecyl, 1-decyl, 4-propyl-4-heptyl, 5-methyl-2-isopropyl-1-hexyl, 3,7-dimethyl-1-octyl, 3 -ethyl-3-octyl group or the like.

In addition, other known alkyl groups or their derivatives can be used as R 1 and R 2 having 8 to 10 carbon atoms and having similar chemical and physical properties such as viscosity, boiling point and extraction capacity and properties mainly determined by the number of carbon atoms. In the present invention, 2-ethyl-1-hexyl, 3,5,5-trimethyl-3-hexyl and / or isodecyl can be used as R1 and R2.

Thus, said extractants comprise, for example: 2-ethyl-1-hexylphosphonic acid mono-2-ethyl-1-hexyl ester, 3,5,5-trimethyl-3-hexylphosphonic acid mono-3,5,5-trimethyl-3-hexyl ester, isodecylphosphonic acid monoisodecyl ester, 2-ethyl-1-hexylphosphonic acid mono-3,5,5-trimethyl-3-hexyl ester, 2-ethyl-1-hexylphosphonic acid monoisodecyl ester, 3,5,5-trimethyl-3-hexylphosphonic acid monoisodecyl ester . A mixture thereof can also be used.

According to the present invention, the iron removal treatment is applied to an organic extraction medium when an unfavorable amount of iron (usually 1 <2 g / l) has accumulated therein for practical purposes.

If the accumulated amount of iron increases to e.g. 2 g / l, then the practical extraction capacity with respect to cobalt decreases by a corresponding amount or more. During such an iron collection, the viscosity of the organic extraction medium rises to several hundred or one thousandth of a centistokes' 68421 when the cobalt is extracted to its maximum extraction capacity. This increase in viscosity, on the one hand, makes it difficult to pump and transport the organic extraction medium through the pipelines and thus overloads the agitator blades and, on the other hand, significantly reduces the extraction rate, which is even more serious. Thus, the accumulation of iron causes various problems when it exceeds the allowable limit, as mentioned above.

For the iron removal treatment, the organic extraction medium is completely or partially removed, if necessary, from the liquid extraction system. The removed organic extraction medium is poured into a mixing tank together with the alkali hydroxide solution, where it is mixed thoroughly, then the aqueous phase is separated from the organic phase, after which the phase-separated organic extraction medium is recovered to complete the iron removal treatment. The room temperature during this treatment is satisfactory. The volume ratio between the organic extraction medium and the aqueous solution ("0 / A ratio" from now on) need not be particularly limited. However, a 0 / A ratio of about 1 is recommended to avoid contamination of the organic phase due to precipitation.

Different reaction times are used in the treatment depending on the miscibility, O / A ratio, etc. where a reaction of at least two minutes is sufficient when using vigorous stirring. As the alkali hydroxide, sodium hydroxide, potassium hydroxide or the like can be used.

With respect to the concentrations of alkali hydroxides used, the organic extraction medium is partially soluble in aqueous solution and a rare low iron removal efficiency is obtained when less alkali hydroxide is present than is required for the reaction with the extractant.

An iron removal efficiency of 97.8% or higher can be obtained by maintaining an alkali metal hydroxide content of not less than 16 g / l in the aqueous solution after treatment. The iron removal efficiency is determined as follows: Ä · "S. x 100 (%)

A

wherein A is iron in the organic extraction medium before treatment, and B is the iron therein after treatment.

In some cases, with an alkali hydroxide content remaining in the aqueous solution of about 16 g / l after treatment, foaming on the surface has been observed, which may cause operational difficulties. This foam dose can be prevented by adding to the aqueous solution a salt such as sodium sulfate, which is inert to the alkali hydroxide, e.g. to a salt content of 30 g / l. When the residual alkali hydroxide content does not fall below 50 g / l 6 68421 in aqueous solution after treatment, no such foaming is observed when said salt is not added.

The resulting organic extraction medium, which has been treated as mentioned above, remains separated in two phases, and the extractant is converted into an alkali salt such as the sodium salt, which can sometimes cause processing difficulties when this alkali salt is returned to the liquid extraction system. Therefore, the organic extraction medium obtained after the above treatment is preferably contacted with a solution containing a mineral acid, whereby an alkali such as sodium in the obtained organic extraction medium dissolves in an aqueous solution and the biphasic organic extraction medium becomes monophasic. As the mineral acid, sulfuric acid having a concentration high enough to neutralize the alkali contained in said obtained organic extraction medium is preferably used. However, a sulfuric acid content of not less than 100 g / l is preferred in order to obtain a high iron removal efficiency and to prevent re-extraction of iron into the organic extraction medium, since iron usually remains therein as iron hydroxide or the like.

In the iron removal treatment process described above, iron transferred to an aqueous solution from an organic extraction medium tends to precipitate as iron hydroxide. Such precipitation often causes functional difficulties in the liquid-liquid reaction. The organic extraction medium forms the upper layer and the aqueous solution the lower layer, whereby precipitation in the latter makes it difficult to remove the solution through the bottom of the tank.

According to the present invention, it has been found that the addition of a monosaccharide, a disaccharide, a polyhydric alcohol and / or the like to an alkali hydroxide solution prevents the precipitation of iron, forming an iron Calate, whereby the iron is converted to soluble iron. Glucose, fructose, corn syrup, sucrose, molasses, sorbitol, mannitol or a mixture thereof can be used as said monosaccharide, disaccharide, polyhydric alcohol and / or the like.

The figure shows the results obtained from chelation experiments using an extractant consisting primarily of 2-ethyl-1-hexylphosphonic acid mono-2-ethyl-1-hexyl ester. The figure shows the relationship between the sucrose content and the chelating power obtained by treating a starting extraction medium with a variable iron content with a mixed solution of sucrose and sodium hydroxide with a constant sodium hydroxide content of 80 g / l. It is shown in the figure that a chelating efficiency of not less than 80% at a sucrose content of 60 g / l and of about 100% / 68421 at a sucrose content of 100 g / l can be achieved without a greater effect of iron content at a sodium hydroxide content of 80 g / l. . Here, the chelating power is defined as the percentage of dissolved iron according to the following diagram:

Chelated iron ion content (g / l) in solution_χ ^ qq (%)

Iron ion content in the organic starting extraction medium

High chelation efficiency can be achieved by selecting an optimal sodium hydroxide content corresponding to a lower sucrose content even when the sucrose content is lower than 60 g / l. The above-mentioned chelated iron means the iron in the filtrate which, in the filtration treatment, passes through the filter paper No. 3.

The resulting organic extraction medium treated with a mixed solution of sodium hydroxide and sucrose or the like is also phase separated and contains large amounts of sodium. Thus, it is treated with mineral acid before being returned to the extraction system.

The organic starting extraction medium subjected to said treatment with alkali hydroxide or a mixed solution of alkali hydroxide and sucrose or the like is usually a substance obtained after the stripping process, but often retains metal ions other than iron as a result of incomplete stripping. If cobalt ions remain there, the iron removal efficiency is greatly reduced. Table I shows the results of iron removal in which five different test solutions were prepared by adding 3.0 g / l iron and 0.05 * 16 g / l cobalt to an organic extraction medium containing 20% by volume of 3,5,5-trimethyl 3-Hexylphosphonic acid mono-3,5,5-trumethyl-3-hexyl ester with the remainder being kerosene.

Table I

Sample No. concentration before treatment concentration after treatment

_ (q / lj (g / D

Co Fe Fe 1 16.00 3.00 2.00 2 1.00 "0.18 3 0.50" 0.082 4 0.05 "0.009 8

Example 1. 68421

To the organic extraction medium containing 22% by volume of 2-ethyl-1-hexylphosphonic acid mono-2-ethyl-1-hexyl ester with kerosene to form the remainder was added with stirring 0.64 g / l of iron ions. This organic extraction medium was contacted with sodium hydroxide solutions at the concentrations shown in Table II. Sample No. 5 had previously been added with 30 g / L sodium sulfate to prevent foaming. The contact treatments were performed at an O / A rate of 1/1, each time 100 ml was shaken in a separatory funnel at 25 ° C for 5 minutes.

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Under conditions where sodium hydroxide was little present in the aqueous solution after treatment (e.g., in Samples No. 1 and 5), the organic extraction medium did not separate into two phases, resulting in a very low iron removal efficiency. Conversely, in samples No. 2-4 with 16, 56 and 90 g / l of sodium hydroxide remaining in the aqueous solutions after treatment, iron was removed to a concentration of 10 mg / l, which corresponds to an iron removal efficiency of more than 97.8%.

Example 2.

0.65 g / l of iron ion was added to an organic extraction medium containing 20% by volume of 3,5,5-trimethyl-3-hexyl ester and the remainder being kerosene. This organic extraction medium was treated with sodium hydroxide solution at the concentration shown in Table III.

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Example 3

Organic extraction media numbered 1-4 were prepared each containing 22% of the following extractant with the remainder consisting of kerosene:

Well. 1; 2-ethyl-l-heksyylifosforihappo mono-3,5,5-trimethyl-3-hexyl ester,

Well. 2; 2-ethyl-l-heksyylifosfonihappo mono-isodekyyliesteri,

Well. 3; 3,5,5-Trimethyl-3-hexyl-phosphonic acid mono-isodecyl ester,

Well. 4; isodekyylifosfonihappomonoisodekyyliesteri.

To each of the above-mentioned organic extraction media, 0.65 g / l of iron was added, each of which was then treated with a sodium hydroxide solution having a concentration of 80 g / l. Each treatment was performed in the same manner as the treatments of Example 1. The results of iron removal efficiency are shown in Table IV.

Table IV

organic extraction medium iron removal efficiency (%) 1 97.80 2 98.10 3 98.00 4 97.85

Example 4.

The organic extraction medium containing 22% by volume of 2-ethyl-1-hexyl-phosphonic acid mono-2-ethyl-hexyl ester, 1.90 g / l of iron ion with the remainder of the kerosene being treated, was treated with five different mixed solutions of sucrose and sodium hydroxide. The treatments were carried out in the same manner as in Example 1. The resulting iron removal power and chelation power are shown in Table V. In these experiments, the iron content reached a maximum of 28 mg / l and a good iron removal power exceeding 98% was obtained. Combinations of sucrose and sodium hydroxide in aqueous solution after treatment, each at 60 g / l and 56 g / l and 30 g / l and 16 g / l, gave a high chelating power.

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Example 5.

An organic extraction medium containing 1.90 g / l of iron and 22% by volume of isodecylphosphonic acid mono-2-ethylhexyl ester was treated with five different mixed solutions shown in Table VI containing sucrose and sodium hydroxide. Each treatment was similar to Example 1. The resulting iron removal and chelating powers are indicated in Table VI.

The maximum iron content in the organic extraction medium was at most 29 ng / l, and high iron removal efficiencies exceeding 98.5% were achieved. Combinations of sucrose and sodium hydroxide in aqueous solution after treatment, each at 60 g / l and 56 g / l and at 30 g / l and 16 g / l, gave high chelating powers.

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Example 6

Five different samples of organic extraction medium containing 20% by volume of each extractant were prepared with the remainder consisting of kerosene as follows:

Sample of Organic Extraction Medium No._ EXTRACTOR__ 1 3,5,5-Trimethyl-3-hexyl-phosphonic acid mono-3,5,5-trimethyl-3-hexyl ester 2-Isodecyl-phosphonic acid monoisodecyl-ester 3 2-Ethyl-1-hexyl-phosphonic acid mono-2-ethyl-1-hexyl ester 4 isodecylphosphonic acid mono-2-ethyl-1-hexyl ester 5 isodecylphosphonic acid mono-3,5,5-trimethyl-3-hexyl ester.

2.00 g / l of iron was added with stirring to each sample. Each sample was then treated with a mixed solution of 60 g / l sucrose and 80 g / l sodium hydroxide in the same manner as in Example 1. The resulting iron removal power and chelation power are shown in Table VII.

Table VII

organic extraction medium iron removal power chelation power 1 98.73 93.60 2 98.78 93.58 3 98.88 93.81 4 98.81 93.70 5 98.82 93.72 According to the present invention there is thus provided a simple process for an organic extraction medium, with an alkylphosphonic acid monoalkyl ester to remove accumulated iron. Thus, it has been possible to prevent deterioration of the organic extraction medium during its recycling and to eliminate the difficulties encountered in handling. In order to further reduce the iron content in the organic extraction medium to a few mg / l ^ 1 mg / l, the above-described treatment can be repeated two or more times.

Claims (6)

68421 17 A process for the separation of iron from an organic extraction medium comprising a diluent and an extractant, characterized in that it essentially comprises an alkylphosphonic acid monoalkyl ester of the formula 0 R 1 - P - OH 6 * 2 wherein R j and R e represent an alkyl group in which has 8 to 10 carbon atoms, said organic extraction medium being contacted with an alkali hydroxide solution. Process according to Claim 1, characterized in that the alkylphosphonic acid monoalkyl ester in which one or two alkyl groups R 1 and R 2 are selected from the group consisting of: 2-ethyl-1-hexyl-, 4-methyl-1-heptyl-, 1-octyl- , 3-ethyl-2-methyl-3-pentyl, 3,5,5-trimethyl-3-hexyl, 3-ethyl-5-methyl-3-hexyl, 1-nonyl, 2-methyl -2-octyl, isodecyl, 1-decyl, 4-propyl-4-heptyl, 5-methyl-2-isopropylhexyl, 3,7-dimethyl-1-octyl and 3-ethyl -3-octyl group, or a mixture thereof is used as said extractant. Process according to Claim 1, characterized in that the alkylphosphonic acid monoalkyl ester having one or two groups R 1 and R 2 selected from the group consisting of 2-ethyl-1-hexyl, 3,5,5-trimethyl-3-hexyl and isodecyl or the mixture is used as said extractant. Process according to any one of claims 1 to 3, characterized in that said organic extraction medium is contacted with a mixed solution of an alkali hydroxide and a monosaccharide, a disaccharide and / or a polyhydric alcohol. Process according to Claim 4, characterized in that glucose, fructose, maize syrup, sucrose, molasses, sorbitol, mannitol or a mixture thereof are used as said monosaccharide, disaccharide and / or polyhydric alcohol. Process according to any one of claims 1 to 5, characterized in that said organic extraction medium is first contacted with a mineral acid solution to remove cobalt therefrom and then in contact with an alkali hydroxide solution or a mixed solution of an alkali metal hydroxide and a monosaccharide, disaccharide and / or polyhydric alcohol.