JPH0480335A - Method for separating tin in solution of platinum group metal - Google Patents

Abstract

PURPOSE:To recover platinum group metals at a high recovering rate at low cost by mixing the hydrochloric acid of platinum group metals including tin with an organic solvent including alkyl phosphonic monoester, stirring this mixture and extracting the tin into the organic solvent layer. CONSTITUTION:The hydrocloric acid soln. of platinum group metals including tin and subjected to the regulation of acidity is mixed with an organic solvent including alkyl phosphonic monoester which is not mingled with water, and this mixture is stirred. In this way, the tin is extracted into the organic solvent layer. Next, the hydrochloric acid soln. layer of the platinum metals is separated from the above organic solvent layer. In this way, the tin in the platinum group metals is separated. By this method, the platinum group metals can simply be isolated in a short time from the mixture or mixed soln. of the platinum group metals and tin. Furthermore, the organic solvent layer with the above extracted tin is washed by a hydrochloric acid having high concn. of >=9 normal, by which the tin can be extracted and separated into the above hydrocloric acid soln. Moreover, as the above platinum group metals, platinum, palladium, rhodium or the like can be used, and as the alkyl phosphonic monoester, 2-ethylhexyl phosphonic monoacid-2-ethylhexyl can be used.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a method for separating tin contained in a solution of a platinum group metal such as platinum, palladium, or rhodium from the platinum group metal, and In particular, the present invention relates to a method for separating tin in a highly safe manner while making effective use of the organic solvent used for separation.

(Prior art and its problems) Platinum group metals are used in various industries as useful metal materials with a wide range of applications. Used platinum group metals are rarely recovered as pure single items, but are often recovered as a mixture with base metals and the like. In this case, various separation methods have been proposed in order to recover and reuse expensive platinum group metals with high purity.

For example, when aqua regia containing palladium contains base metals such as tin, ammonium chloride is added to form a precipitate as a palladium compound, and after filtration, the precipitate is dissolved as an ammine complex salt by adding aqueous ammonia to remove impurities. There is a method in which the hydroxide is separated by filtration, and the impurities are removed by adding hydrochloric acid to a palladium ammine complex salt solution to precipitate it and filtering it.

In addition, rhodium is reduced by adding sodium nitrite to a hydrochloric acid solution, filtered to separate impurities as a precipitate, ammonium chloride is added to the filtrate to form a precipitate as a rhodium compound, and the precipitate is filtered. There is a method for removing impurities that involves repeating the steps of dissolving in hydrochloric acid and then adding the aforementioned sodium nitrite for reduction.

However, this conventional method requires a long process (recovery rate tends to decrease and a filtration process is required, making continuous operation difficult.
Another disadvantage is that the settling rate of the tin hydroxide is slow, which becomes a bottleneck in speeding up the entire process.

(Objective of the Invention) The present invention has been made to eliminate the drawbacks of these conventional techniques, and aims to achieve high recovery rate and low cost by shortening or making the separation process of platinum group metal and tin continuous. An object of the present invention is to provide a method for separating tin in a platinum group metal solution, which makes it possible to recover the platinum group metal.

(Means for Solving the Problems) The present invention first provides an acidity-adjusted hydrochloric acid solution of a platinum group metal containing tin with an organic solvent containing mono-2-ethylhexyl 2-ethylhexylphosphonate that is immiscible with water. This is a method for separating tin in a platinum group metal solution, in which tin is extracted into an organic solvent layer by mixing and stirring, and a hydrochloric acid solution layer of a platinum group metal is separated from the organic solvent layer.Secondly, following this first step, , a second step of washing the organic solvent layer from which the tin has been extracted with a high concentration hydrochloric acid solution, preferably 9N or more, and extracting and separating the tin in the hydrochloric acid solution. This is a method for separating tin in a metal solution.

The present invention will be explained in detail below.

The first step of the method for separating tin from a platinum group metal solution according to the present invention is to separate the platinum group metal by extracting it into a hydrochloric acid solution and the tin into an organic solvent layer, and the second step is They are intended to separate the tin from the organic solvent layer by washing the organic solvent layer from which tin has been extracted with a highly concentrated hydrochloric acid solution, and in the first step, the platinum group metal is substantially separated from the tin. be done.

The platinum group metals targeted by the present invention include platinum, palladium,
Tin is separated from a solution containing rhodium and one or more of these metals.

If this solution does not contain hydrochloric acid, the acidity is adjusted to be acidic with hydrochloric acid, and then the mixture is mixed with the organic solvent layer of the alkylphosphonic acid monoester and stirred to perform extraction. This alkylphosphonic acid monoester and organic solvent are used to almost selectively extract only tin out of the platinum group metal and tin into the organic solvent layer, and almost selectively extract the platinum group metal into the hydrochloric acid solution that is the extraction residue. It is preferable to use mono-2-ethylhexyl 2-ethylhexylphosphonate as the alkylphosphonic acid monoester, and the organic solvent is water that functions as a diluent for the alkylphosphonic acid monoester. Any aliphatic or aromatic solvent that is immiscible with the solvent can be used, such as 5hellsol D70.

Extraction conditions are not particularly limited, but it is sufficient to stir the organic solvent and hydrochloric acid solution at room temperature for about 1 to 3 hours and then allow to stand. The ratio of the organic solvent to the hydrochloric acid solution is preferably 1:1.

Through this extraction operation, most of the tin is extracted into the organic solvent layer containing the alkylphosphonic acid monoester, and a small amount of tin is extracted into the extraction residue, which is a hydrochloric acid solution containing almost all of the platinum group metals. It's just being done. This extraction residue is usually discarded after the platinum group metals are recovered.

A high concentration hydrochloric acid solution, preferably 9N or more, preferably 12N or more, is mixed into the organic solvent layer and extracted by stirring. The tin that was not extracted by the relatively low concentration hydrochloric acid solution mentioned above is extracted by this high concentration hydrochloric acid solution, and only a small amount of tin remains in the organic solvent layer.

If this organic solvent layer is preferably recycled and reused in the first step, not only will it be possible to reduce costs, but also the extraction operation can be carried out using only a small amount of solvent, thereby ensuring safe operation. It becomes possible.

(Example) Next, an example of the method for separating platinum group metal and tin according to the present invention will be described, but the present invention is not limited to this example.

Example 1 50 g/f palladium and 5 g/I! 100 ml of hydrochloric acid solutions of three concentrations, respectively I, 3 and 6N, containing tin of 1 mole of mono-2-ethylhexyl 2-ethylhexylphosphonate were added to
After mixing with 100 ml of the solution and stirring for 1 hour, the phases were separated into an organic solvent layer and an extraction residue. The respective concentrations of tin and palladium in the organic solvent layer and the extraction residue were detected as shown in Table 1 when each of the three types of hydrochloric acid solutions were used. Table 1 also shows the results of calculating the distribution ratio [(weight of tin in the organic solvent layer)/(weight of tin in the extraction residue)] in this extraction operation.

Table 1 Organic solvent layer from a solution with an initial hydrochloric acid concentration of 1N (100 ml of tin weight 4.9 g/I was mixed with 100 ml of 12 N hydrochloric acid, stirred for 2 hours, and then phase separated) an organic solvent layer containing 0.1 g/I! of tin;
．． 8g/I! was separated from the residual hydrochloric acid containing tin.

From this result, 2-ethylhexylphosphonic acid mono-2-
100 by extraction with an organic solvent layer containing ethylhexyl.
% of palladium is separated, and tin in the organic solvent layer is extracted with the highly concentrated hydrochloric acid solution by a subsequent extraction operation with a highly concentrated hydrochloric acid solution, and an organic solvent layer containing almost no tin is recovered; It can be seen that palladium and tin can be separated best when the concentration of the hydrochloric acid solution is about 1 normal.

Example 2 Tin was separated from a hydrochloric acid solution of platinum and tin under the same conditions as in Example 1, except that platinum was used instead of palladium in Example 1. The respective concentrations of tin and platinum in the organic solvent layer and extraction residue when each of the three types of hydrochloric acid solutions were used were detected and were as shown in Table 2. The results of calculating the distribution ratio are shown in Table 2.

Initial hydrochloric acid solution concentration: The organic solvent layer (tin weight 4.9 g/I) from a solution with a specified concentration was mixed with 100 ml of 12 N hydrochloric acid, stirred for 2 hours, and then phase-separated to obtain 0.1 g/I. 4. an organic solvent layer containing tin of I!;
8g/I! was separated from the residual hydrochloric acid containing tin.

From this result, 2-ethylhexylphosphonic acid mono-2-
100 by extraction with an organic solvent layer containing ethylhexyl.
% of platinum is separated, and through a subsequent extraction operation with a highly concentrated hydrochloric acid solution, tin in the organic solvent layer is extracted with the highly concentrated hydrochloric acid solution, and an organic solvent layer containing almost no tin is recovered; It can be seen that the separation of platinum and tin is best achieved when the concentration of the hydrochloric acid solution is about 1 normal.

Table 2 Example 3 Tin was separated from a hydrochloric acid solution of rhodium and tin under the same conditions as in Example 1 except that rhodium was used instead of palladium in Example 1. The respective concentrations of tin and rhodium in the organic solvent layer and the extraction residue were detected as shown in Table 3 when each of the three types of hydrochloric acid solutions were used. The results of calculating the distribution ratio are shown in Table 3.

Table 3 100 ml of organic solvent layer (tin weight 4.9 g/I!) from a solution whose initial hydrochloric acid solution concentration is 1N
After mixing with 100 ml of 2N hydrochloric acid and stirring for 2 hours,
When the phase was separated, it was 0.1g/I! The solution was separated into an organic solvent layer containing 4.8 g/l of tin and a hydrochloric acid residue containing 4.8 g/l of tin.

From this result, 2-ethylhexylphosphonic acid mono-2-
100 by extraction with an organic solvent layer containing ethylhexyl.
% of rhodium is separated, and tin in the organic solvent layer is extracted into the highly concentrated hydrochloric acid solution by a subsequent extraction operation with a highly concentrated hydrochloric acid solution, and an organic solvent layer containing almost no tin is recovered; It can be seen that rhodium and tin can be separated best when the concentration of the hydrochloric acid solution is about 1N.

(Effects of the Invention) The present invention involves mixing and stirring a hydrochloric acid solution of a platinum group metal containing tin with adjusted acidity with an organic solvent containing an alkylphosphonic acid monoester that is immiscible with water, extracting tin into an organic solvent layer, and then producing platinum metal. A method for separating tin in a platinum group metal solution (claim 1), characterized in that a hydrochloric acid solution layer of a group metal is separated from the organic solvent layer.

According to this method, tin can be separated from a mixture or mixed solution of platinum group metals and tin by only an extraction operation, and platinum group metals can be separated from platinum group metals without the need for long-time sedimentation operations or complicated filtration operations. can be isolated.

Further, in the present invention, following the operation of claim 1, the organic solvent layer from which the tin has been extracted can be washed with a highly concentrated hydrochloric acid solution to extract and separate tin into the hydrochloric acid solution (claim 2).
As a result, as in claim 1, it is not only possible to separate tin by only an extraction operation, but also to recover an organic solvent containing almost no tin, for example, by recycling the organic solvent to the separation step and reusing it. This not only makes it possible to reduce costs (extraction operations can be performed using only a small amount of solvent, making it possible to perform safe operations).

Although the platinum group metal used is not particularly limited, the effect is remarkable when platinum, palladium, and rhodium are used (claim 3).

The alkylphosphonic acid monoester to be used is not particularly limited as long as it is a compound that can extract tin to the organic solvent layer side, but when mono-2-ethylhexyl 2-ethylhexylphosphonate (claim 4) is used, tin can be extracted at a high distribution ratio. can be separated.

Furthermore, in claim 2, the concentration of the hydrochloric acid solution is at least 9N, and in claim 5), an organic solvent containing almost no tin can be recovered within a range above the concentration range.

Claims (5)

[Claims] (1) A hydrochloric acid solution of a platinum group metal containing tin whose acidity has been adjusted is mixed and stirred with an organic solvent containing an alkylphosphonic acid monoester that is immiscible with water, and tin is extracted into an organic solvent layer. A method for separating tin in a platinum group metal solution, the method comprising separating tin from the organic solvent layer. (2) A hydrochloric acid solution of a platinum group metal containing tin whose acidity has been adjusted is mixed and stirred with an organic solvent containing an alkylphosphonic acid monoester that is immiscible with water to extract tin into an organic solvent layer, and the platinum group metal hydrochloric acid solution layer is mixed and stirred. a first step of separating tin from the organic solvent layer; and a second step of washing the organic solvent layer from which the tin has been extracted with a highly concentrated hydrochloric acid solution and extracting and separating tin into the hydrochloric acid solution. A method for separating tin in a platinum group metal solution. (3) The method according to claim 2, wherein the platinum group metal is at least one metal selected from the group consisting of platinum, palladium, and rhodium. (4) The method according to claim 2 or 3, wherein the alkylphosphonic acid monoester is mono-2-ethylhexyl 2-ethylhexylphosphonate. (5) The method according to any one of claims 2 to 4, wherein the concentration of the highly concentrated hydrochloric acid solution is 9 normal or more.