JPS605652B2 - Method for removing iron from organic solvents - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for treating organic solvents used in solvent extraction methods, and in particular to a method for treating organic solvents used in solvent extraction methods, and in particular for extracting cobalt from solutions containing nickel and cobalt. Deletion of an organic solvent consisting of an extractant and a diluent whose main component is an alkyl ester (however, the alkyl group is selected from C8 to C, o alkyl groups, excluding the combination of C8-C8). It concerns the iron method.

In the field of hydrometallurgy, a process known as solvent extraction is used for the selective extraction of some metals. When selecting an extractant, consider that the extractant has low solubility in the aqueous solution containing the target metal, and that it has the ability to selectively and efficiently extract the target metal ion from the aqueous solution. must be done. Furthermore, since the extractant is diluted with a diluent and used as an extraction solution, it needs to be well soluble in the diluent. As an extractant for selectively extracting cobalt from acidic leachate or waste liquid containing nickel and cobalt, in the present invention, an extractant whose main component is an alkylphosphonic acid monoalkyl ester having the following structural formula is used. :(R, is an alkyl group selected from C, o alkyl groups from C8,
And R2 is an alkyl group selected from C8 to C, o alkyl groups.

However, combinations in which R is C8 and R2 is C8 are excluded. ) The liquid obtained by dissolving this extractant in a diluent such as mineral oil or kerosene is hereinafter simply referred to as an organic solvent. Such an organic solvent exhibits an excellent extraction capacity for selectively extracting cobalt from aqueous solutions such as leachate and waste liquid containing nickel and cobalt.

In the extraction step, an aqueous phase containing nickel and cobalt and an organic solvent are contacted and mixed using a mixer settler, an extraction tower, a centrifugal extractor, or the like. The mixing temperature is generally 20
o to 80°C, and the volume ratio of the aqueous phase to the organic solvent is approximately 10:1 to 1:1.
In solvent extraction operations, organic solvents are recycled until their performance deteriorates, but during this time iron present in large amounts in the liquid and iron eluted from equipment etc. gradually accumulates.

As iron accumulates in the organic solvent, the actual extraction capacity decreases accordingly, and more importantly, when the iron-containing organic solvent extracts cobalt, its viscosity increases significantly.
When this increase in viscosity occurs, various troubles occur during the transfer and mixing process using pumps, valves, mixers, etc. Therefore, when performing solvent extraction using such an organic solvent, it is essential to remove iron accumulated in the organic solvent in order to obtain stable extraction ability and performance. The present inventor has previously specified an effective iron removal method for 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester corresponding to the combination of R,:C8 and R2:C8 among alkylphosphonic acid monoalkyl esters. Gansho 5
It was proposed in No. 3-109603.

In the method proposed here, an organic solvent consisting of an extractant and a diluent containing 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester as a main component is mixed with an aqueous solution of alkali hydroxide or alkali hydroxide and carbohydrates. It is characterized by cleaning with a mixed solution of. Subsequent research confirmed that the above iron removal method could be widely applied to alkylphosphonic acid monoalkyl esters having C8 to C, o alkyl groups in addition to 2-ethylhexylphosphonic acid mono-2-ethylhexyl esters. Ta.

Thus, the present invention provides an organic solvent which is characterized in that an organic solvent consisting of an extractant and a diluent containing an alkylphosphonic acid monoalkyl ester represented by the following formula as a main component is washed with an aqueous solution of alkali hydroxide. Provides a method for removing iron from a solvent; (R, represents an alkyl group selected from C8 to CM alkyl groups; R2 represents an alkyl group selected from C8 to C, o alkyl groups;

However, the combination of R,3C8 and R2:C6 is excluded. ) As stated in Japanese Patent Application No. 53-109603, in the iron removal method for the 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester extractant, the iron transferred from the organic solvent to the aqueous solution is treated as iron hydroxide. Precipitation occurs, which makes the operation difficult, but by adding carbohydrates to the aqueous alkali hydroxide solution, a chelation reaction occurs and precipitation can be effectively prevented.

It has been found that this precipitation prevention method is equally applicable to the alkylphosphonic acid monoalkyl esters which are the subject of the present invention. From this point of view, the present invention also provides an organic solvent consisting of an extractant and a diluent containing an alkylphosphonic acid monoalkyl ester as a main component as defined above as a subject of the present invention, and an alkali hydroxide and a carbohydrate. Provided is a method for removing iron from an organic solvent, which is characterized by washing with a mixed solution of iron. Furthermore, it was discovered in Samurai Sho 53-109603 that cobalt remaining in the organic solvent has a large effect on the iron removal rate, and that iron removal is promoted by removing cobalt in advance. This fact also falls under the scope of the present invention.

Thus, the present invention further provides the steps of: washing an organic solvent consisting of an extractant and a diluent based on an alkylphosphonic acid monoalkyl ester as defined above with a mineral acid to previously remove cobalt; The present invention also provides a method for removing iron from an organic solvent, which comprises washing with an aqueous solution of alkali hydroxide or a mixed solution of alkali hydroxide and bran. The present invention will be explained in detail below.

As mentioned above, the extractant targeted by the present invention is one which excludes the C8-C8 combination among alkylsulfonic acid monoalkyl esters containing two C8 to C, o alkyl groups.

Specifically, 2-ethylhexylphosphonic acid mono 3.
5,5-trimethylhexyl ester "2-ethylhexylphosphonic acid monoisodecyl ester, 3.5.5
-trimethylhexylphosphonic acid mono 2-ethylhexyl ester, 3,5,5-trimethylhexylphosphonic acid mono 315,5-trimethylhexyl ester, 3
・515-trimethylphosphonic acid monoisodecyl ester, isodecylphosphonic acid mono-2-ethylhexyl ester, isodecylphosphonic acid mono-3,5,5-trimethylhexyl ester, and isodecylphosphonic acid monoisodecyl ester Includes Esther. According to the present invention, when the accumulated iron content of the organic solvent increases to a concentration that is unfavorable in actual operation (usually 1 to 2 evenings/night), iron removal treatment is performed.

When the iron content increases, for example, by 2 days/day, the actual amount of cobalt extracted decreases by 2 to 3 times. Furthermore, when cobalt is extracted to near maximum capacity, its viscosity increases to hundreds to thousands of centistokes, which not only impedes the smooth transfer of organic solvents through pumps and piping, but also increases the viscosity of cobalt in mixing equipment. This places too much load on the vanes and, more importantly, significantly reduces the reaction rate. Accumulation of iron content above acceptable levels is thus the root of the problems mentioned above. In the iron removal treatment, the organic solvent is partially or completely extracted from the solvent extraction system as required.

The extracted organic solvent is put into a tank together with an aqueous alkali hydroxide solution, mixed thoroughly and left to separate into an aqueous phase and an organic phase, and then the separated organic solvent is recovered. Iron treated. Room temperature is sufficient for this treatment, and there is no need to limit the volume ratio of the organic solvent to the aqueous solution (hereinafter referred to as ○/A), but in order to reduce the mixing of the precipitate into the organic phase, It is desirable that ○/A=1. The reaction time varies depending on the strength of the rope, the 0 no A ratio, etc., but under strong fly Azusa, 2 minutes or more is sufficient. As the alkali hydroxide, commonly used sodium hydroxide, potassium hydroxide, etc. are sufficient. Regarding the concentration of alkali hydroxide used, if the amount of alkali hydroxide used is less than the amount required to react with the extractant, a part of the organic solvent will dissolve in the aqueous solution, and furthermore, the iron removal rate will be significantly reduced. was recognized.

Preferably, the alkali hydroxide concentration in the cleaning solution is 16 ta'.
By maintaining the iron content above the limit, a high iron removal rate of 97.8% or more can be achieved. Here, the iron removal rate is the amount of iron in the organic solvent l before cleaning - the amount of iron in the monthly bleaching process after cleaning the board.

〇 Expressed as the amount of iron in the organic solvent before washing.

If the concentration of alkali hydroxide remaining in the solution after cleaning is around 16 ta, bubbles may form on the surface and handling may become somewhat difficult. By adding it to an aqueous solution at such a concentration, the generation of bubbles can be prevented.

Furthermore, if the concentration of residual alkali hydroxide in the solution after cleaning is set to 50 m/kg or more, such foaming will not occur even without the use of additives. The organic solvent that has been deironated according to the above method is separated into two phases, and all the extractants are alkali salts such as sodium salts. In some cases,

Therefore, the organic solvent obtained by the above treatment is preferably subjected to a contact treatment with an aqueous solution containing a key acid. By this contact treatment with the key acid aqueous solution, alkali such as sodium in the organic solvent returns to the aqueous solution, and by this treatment, the organic solvent which had been separated into phases returns to one phase. Sulfuric acid is a typical example of hydric acid, and its concentration may be sufficient as long as it neutralizes the sodium in the organic solvent, but usually a small amount of iron remains in the form of hydroxide etc. in the organic solvent. Therefore, in order to maintain a high actual iron removal efficiency, for example, 1
It is desirable to use sulfuric acid at a concentration of 0.00 mg/mL or higher to prevent re-extraction of iron into organic solvents. In the iron removal treatment method using an aqueous solution of alkali hydroxide, the iron transferred from the organic solvent to the aqueous solution is precipitated as iron hydroxide.

In liquid-liquid reactions, the presence of precipitates can make the operation even more difficult. After iron removal treatment, an organic solvent as an upper layer and an aqueous solution as a lower layer exist in the wastewater tank, and the formation of precipitates in the aqueous solution becomes an obstacle to extracting the liquid from the bottom of the tank. In Tokuiso Sho 53-1093603, 2-
For organic solvents that use extractants whose main component is ethylhexylphosphonic acid mono-2-ethylhexyl ester, such substances can be removed by adding lees such as bear sugar, glucose, and fructose to the alkaline hydroxide solution. It was disclosed that precipitation is effectively prevented. That is, iron can be chelated to become water-repellent iron. This precipitation prevention method is also useful in the method of the present invention. For example, when we conducted a chelation test using an extractant containing isodecylphosphonic acid monoisodecyl ester as the main component, the results were almost the same as in the case of 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester. was gotten. The results are shown in FIG. 1st
The figure shows the relationship between the fluorescing sugar concentration and the chelation rate when stock solutions with various iron concentrations were treated using a sodium hydroxide monosaccharide mixed aqueous solution with a constant sodium hydroxide concentration of 80 tons. It shows. As is clear from Figure 1,
The xylation of iron is ``unaffected by the iron concentration, and when sodium hydroxide is added to 80% of sodium hydroxide, the concentration of maize sugar is 60%, which is more than 80%, and the concentration of competitive sugar is 100%, which is almost 100%. 100% is achieved.Here, the chelation rate is the iron ion concentration (data) in the chelated liquid.
.

〇 It is the percentage value of iron in the dissolved state expressed as the concentration of iron ions in the stock solution.

Note that the amount of organic solvent does not change before and after washing. Even when the concentration of brown sugar is as low as 60 ta' or less, it is possible to achieve a very high chelation rate by selecting a sodium hydroxide concentration commensurate with the sugar concentration.

Here, the chelated iron is No. 1 in the above washing. 3
refers to the iron in the furnace liquid that has been filtered through the furnace paper. The organic solvent treated by the washing method using the alkali hydroxide-saccharide mixed solution also separates into two phases as described above, and also contains a large amount of sodium.

Therefore, in order to return it to the extraction system, it must be treated with mineral acids as before. The organic solvents used for the above-mentioned washing treatment with aqueous solutions of alkali hydroxide and alkali hydroxide-saccharides are generally those that have been subjected to back extraction, but due to insufficient back extraction, iron may not be present in this organic solvent. Other metal ions often remain.

As in the case of 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester, when this residual metal ion is cobalt, the iron removal rate is significantly reduced.

3,5,5-trimethylhexylphosphonic acid mono-3.
Five types of test solutions were prepared by adding 3.0 t' of iron and 0.05 to 16 t' of cobalt to an organic solvent in which 5,5-trimethylhexyl ester was diluted to 20% with kerosene. The results of iron removal treatment using an aqueous solution containing Yu/Yu are shown below.

Table 1 It is clear from Table 1 that the higher the cobalt concentration, the worse the iron removal rate.

In order to make the iron ion concentration in the organic solvent after iron removal less than 9/10, it is necessary to make the cobalt concentration in the organic solvent less than 0.05/less. Removal of cobalt can be effectively carried out by contacting with a mineral acid at a concentration equal to or higher than that used for back extraction, for example, if sulfuric acid is used, a concentration of 50 or higher is preferred. Example 1 3.5.5-trimethylhexylphosphonic acid mono-3.
Iron ions were added to an organic solvent prepared by dissolving a 20% 5,5-trimethylhexyl ester extractant in kerosene for 0.65 pm/day.

This organic solvent was used as a washing liquid and was washed with an aqueous sodium hydroxide solution having a concentration shown in Omotegawa. Sho No. In No. 5, sodium sulfate was added in advance for 30 minutes to prevent foaming. Washing was carried out by placing 100' of each in a 0/A:1/1 ratio into a separating funnel and shaking for 5 minutes at a temperature of 25°C. After the reaction, the organic solvent separated into two phases. The average iron concentration in the organic solvent in the table represents the average iron concentration calculated by analyzing samples taken from each phase with a pipette and taking into account the difference in volume. Front stop No. No. 1 and No. 2 had bubbles on the surface, but no. In samples 3 and 4, no bubbles were observed.

If the NaOH concentration in the aqueous solution after the test is high, no foaming occurs. In addition, No. 1 to which sodium sulfate had been added in advance was used. No. 5 produced no bubbles. When there was almost no sodium hydroxide in the aqueous solution after the test (Nos. 1 and 5), the organic solvent did not separate into two phases, and the iron removal rate was extremely low.

On the other hand, No. 1, in which 1,050,96 days of sodium hydroxide remained in the aqueous solution after the test. In samples 2 to 4, iron was removed to the extent of 9/10, achieving an iron removal rate of 98% or more. Example 2 2-ethylhexylphosphonic acid mono-3,5,5-trimethylhexyl ester extractant, 2-ethylhexylphosphonic acid mono-isodisyl ester extractant, 315,5-
Organic solvents prepared by dissolving trimethylhexylphosphonic acid monoisodecyl ester extractant and isodecylphosphonic acid monoisodecyl ester extractant in kerosene at a concentration of 100% were sequentially used as organic solvents 1, 2, and 3. and 4.

0.65 ta' of iron ions were added to these organic solvents. The organic solvent was washed with an aqueous sodium hydroxide solution for 80 minutes. The cleaning method was the same as in Example 1. The organic solvent after washing was separated into two phases. The results of the iron removal rate obtained are shown in Table m below. Table m Example 3 For an organic solvent of isodecylphosphonic acid mono-2-ethylhexyl ester containing 1.90% iron and diluted with kerosene to a concentration of 22%, five types of A cleaning treatment was carried out using a futuristic sugar-sodium hydroxide aqueous solution as a cleaning liquid.

The washing conditions are the same as in Example 1. The obtained iron removal rate and chelation rate are shown in the same table. Table W The iron concentration in the organic solvent after iron removal was at most 29.9', and the iron removal rate was a good result of 98.5% or more.

The combination of sucrose and sodium hydroxide in the aqueous solution after the test at 60 to 56 degrees and 30 to 16 degrees showed a high chelation rate. Example 4 3.5.5-trimethylhexylphosphonic acid mono-3.
5,5-trimethylhexyl ester, isodecylphosphonic acid monoisodecyl ester, 2-ethylhexylphosphonic acid mono-3,5,5-trimethylhexyl ester, 3,5,5-trimethylhexylphosphonic acid mono2
- Ethylhexyl ester and isodecylphosphonic acid mono-3,5,5-trimethylhexyl ester An organic solvent diluted with kerosene to a concentration of 20% was prepared as an extractant.

These organic solvents are named organic solvents 1, 2, 3, 4, and 5 in order. Iron was added to these at 2.00 m/kg and washed with an aqueous sodium hydroxide solution of 60 mtg/80 mt/g. The cleaning treatment was the same as in Example 1. The iron removal rate and chelation rate obtained are as shown in the following table.
As shown in Table V, the present invention has established an extremely simple method for removing iron accumulated in an organic solvent consisting of a monoalkyl ester of alkylphosphonate defined herein and a diluent. According to the present invention, the problems of deterioration in the quality of organic solvents and adverse effects in handling during the cyclic use of organic solvents can be solved.

If it is necessary to remove the iron concentration in the organic solvent to a level of several nines to one nines, this can be easily accomplished by repeating the above-mentioned washing two or more times.

[Brief explanation of drawings]

Figure 1 shows that the organic solvent using isodecylphosphonic acid monoisodecyl ester has a concentration of 80% when washed with an aqueous sodium hydroxide monosucrose solution with a sodium hydroxide concentration of 80%. This is a graph showing the relationship between chelation rate and chelation rate.

Claims (1)

[Scope of Claims] 1. An organic solvent comprising an extractant and a diluent containing an alkylphosphonic acid monoalkyl ester represented by the following formula as a main component, which is washed with an aqueous solution of alkali hydroxide. How to remove iron. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (R_1 represents an alkyl group selected from C_8 to C_1_0 alkyl groups, R_2 represents an alkyl group selected from C_8 to C_1_
represents an alkyl group selected from 0 alkyl groups. However, the combination of R_1:C_8 and R_2:C_8 is excluded. ). 2. From an organic solvent characterized by washing an organic solvent consisting of an extractant and a diluent whose main components are alkylphosphonic acid monoalkyl esters represented by the following formula with a mixed solution of alkali hydroxide and carbohydrates. How to remove iron. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (R_1 represents an alkyl group selected from C_8 to C_1_0 alkyl groups, R_2 represents an alkyl group selected from C_8 to C_1_
represents an alkyl group selected from 0 alkyl groups. However, the combination of R_1:C_8 and R_2:C_8 is excluded. ). 3. An organic solvent consisting of an extractant and a diluent containing an alkylphosphonic acid monoalkyl ester represented by the following formula as a main component is washed with mineral acid to remove cobalt in advance, and then an aqueous solution of alkali hydroxide or water is used. A method for removing iron from an organic solvent, which comprises washing with a mixed solution of alkali oxide and carbohydrates. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (R_1 represents an alkyl group selected from C_8 to C_1_0 alkyl groups, R_2 represents an alkyl group selected from C_8 to C_1_
represents an alkyl group selected from 0 alkyl groups. However, the combination of R_1:C_8 and R_2:C_8 is excluded. ).