JP2001107157A - Method for recovering platinum of high purity - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for efficiently separating palladium from an aqueous solution containing palladium and platinum and recovering platinum of high purity. SOLUTION: The pH of an aqueous solution containing platinum and palladium is adjusted to >8 and, dimethylglyoxime is added thereto, by which palladium is separated. This method is made more effective by controlling the amount of dimethylglyoxime to be added to >=2 by the molar ratio to palladium in the aqueous solution.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for obtaining high-purity platinum. More specifically, the present invention relates to a method for separating palladium from an aqueous solution containing palladium and platinum to obtain high-purity platinum. Further, the present invention relates to a method for obtaining high-purity platinum by separating palladium from an extract containing platinum obtained in a smelting process.

[0002]

2. Description of the Related Art Platinum obtained in a smelting process includes tellurium,
Conventionally, sponge platinum containing impurities such as palladium and iron could not satisfy the standards. In particular, palladium is difficult to separate from platinum because of its similar chemical properties to platinum.

[0003] As a method for separating platinum and palladium, a solvent extraction method is known (JP-A-3-25352).
No. 4, JP-A-11-229052).
JP-A-3-253524 describes a solvent extraction method using a dialkylethane as an extractant.
In this method, it is suggested that palladium and platinum can be separated by adjusting the hydrochloric acid concentration and the extraction time, but usually, palladium and platinum are simultaneously extracted and recovered. JP-A-11-229052 discloses a nitric acid solution containing platinum and palladium,
A method for separating palladium from platinum, which involves extracting palladium with a hydroxime-based solvent and then contacting it with an octylamine-based solvent to extract platinum, which requires two-stage extraction.

[0004] Also, allyl alcohol is added to a mixed hydrochloric acid solution of platinum and palladium to reduce palladium to a metal form, the filtrate after washing by filtration is made alkaline with sodium hydroxide, and formic acid is added to heat the platinum to remove the platinum. In the form of
A method for separating platinum and palladium by filtration is also provided (JP-A-6-287654), but the process is complicated.

As described above, at present, there is no satisfactory method capable of efficiently and simply separating palladium from a platinum-containing aqueous solution containing palladium.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to efficiently separate palladium from an aqueous solution containing palladium and platinum and to recover high-purity platinum. Another object is to provide a method for separating palladium from a palladium-containing platinum extract obtained from a smelting process and recovering high-purity platinum.

[0007]

Means for Solving the Problems On the other hand, the present applicant has noticed that dimethylglyoxime is used in a method for quantitative analysis of palladium, and added dimethylglyoxime to a gold electrolyte containing palladium. And a method for purifying a gold electrolyte for separating a palladium by forming and precipitating a palladium complex (JP-A-11-12778). The present inventors have focused on the fact that this precipitation method using dimethylglyoxime can be used to separate palladium in the smelting process of platinum, and as a result of intensive research, added dimethylglyoxime under specific conditions. As a result, the present inventors have found that palladium can be separated at a high removal rate, thereby leading to the present invention.

That is, the present invention provides a method for removing palladium from an aqueous solution containing platinum and palladium by adjusting the pH of an aqueous solution containing platinum and palladium to a pH exceeding 8, and then adding dimethylglyoxime. It has been found that separation and removal can be performed efficiently at a high rate. further,
It was also found that when the amount of dimethylglyoxime added was 2 or more in molar ratio to the amount of palladium in the liquid, palladium could be removed at a higher removal rate. Also,
The present invention is more useful when the aqueous solution containing platinum and palladium is an aqueous solution obtained from a platinum extraction step in a smelting step. Furthermore, the present invention also provides a method for recovering high-purity platinum using the aqueous platinum solution from which palladium has been removed in this way.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described with reference to FIGS.
This will be described along the flowchart shown in FIG. FIG. 1 is a flowchart showing a step (Pt step) of recovering platinum from an extract containing palladium, platinum and the like obtained from a copper smelting step and the like. FIG. 2 shows a process from back-extraction of tributyl phosphate (TBP) (hereinafter referred to as chloroplatinic acid solution) to crystallization of Pt in the Pt process as a palladium removal process (Pd removal process).

[0010] The outline of the palladium removal step is as follows. First, the pH of the chloroplatinic acid solution is adjusted to neutralize the solution, iron and the like are precipitated in the neutralization step, and then dimethylglyoxime (DMG)
Is added to remove palladium.

The present inventors have now found that the pH of the neutralization step affects the Pd removal rate due to the addition of DMG. When the pH of the neutralization step is 8 or less,
The effect of removing Pd is poor, and if the pH exceeds 8, the effect of removing Pd is significantly increased. In addition, the present inventors have proposed that DMG
It has also been found that in the addition step, the amount of DMG added affects the removal of Pd. That is, when 2 or more of DMG is added in a molar ratio to the amount of Pd in the solution, the Pd removal rate further increases.

Hereinafter, the effects of the pH in the neutralization step and the amount of DMG added on the Pd removal rate will be described in detail with reference to Examples 1 and 2.

Example 1 A chloroplatinic acid solution was adjusted to pH 1 with a NaOH solution.
Then, the mixture was filtered with a 5C filter paper, and a part of the filtrate was used as an analysis sample. The filtrate was collected in 300 ml portions and NaO
After each neutralization pH (5-10) with H solution, 1
The solution was filtered through a μ membrane filter. 25 of this filtrate
0 ml was collected and the molar ratio (DMG / Pd in the solution after pH adjustment) =
After adding DMG to 2 and stirring for 1 hour, the mixture was again filtered through a 1 μm membrane filter, and the amount of filtrate and the amount of residue were measured.

Table 1 shows the concentration of each component in the solution after the treatment at each neutralization pH and after the addition of DMG.

[Table 1] Concentrations in solution after neutralization and after addition of DMG

Further, the neutralization pH, the concentration in the solution after neutralization and the DM
FIG. 3 shows the relationship between the Pd and Pt concentrations in the solution after the addition of G.

As shown in Table 1 and FIG. 3, the Pd concentration was 55 to 12 when neutralized at a pH exceeding 8 and DMG was added.
It can be seen that it decreases from 5 mg / L to several mg / L. On the other hand, when DGM is added in a region lower than pH 8, the Pd concentration is reduced only to about 21 mg / L.

[0016]

Example 2 In order to test the effect of the amount of DMG added, p
H was set to 8.5, and the addition molar ratio of DMG (DMG / p
The same method as in Example 1 was repeated and analyzed except that Pd) in the solution after H adjustment was changed. The results are shown in Table 2 and FIG.

[Table 2] DMG addition amount and Pd concentration Table 2 and FIG. 4 show that after adjusting the pH to above 8, DMG
Is added so that the molar ratio (Pd in the DMG / pH adjusted solution) is 2 or more, the removal rate of Pd is further increased.

Next, an example of recovering Pt from a chloroplatinic acid solution by the method of the present invention will be described as Example 2.

Example 3 A high-purity Pt-containing solution from which Pd was removed was obtained by the method of Example 1. At this time, the pH at the time of adding DGM was adjusted to 8.5. High purity Pt obtained
46 L of concentrated hydrochloric acid is added to 460 L of the containing solution to make a 1 M hydrochloric acid solution. Add 200g / L ammonium chloride aqueous solution and add P
Crystallize t as ammonium chloroplatinate. The purity of the platinum sponge obtained by firing this ammonium chloroplatinate is 9
9.95% or more.

[0018]

As described above, in the present invention, the aqueous solution containing platinum and palladium is adjusted to a pH of more than 8, and then dimethylglyoxime is added to thereby remove Pd from the aqueous Pt solution at a high rate. Was able to be separated. Further, the amount of DMG to be added was adjusted in a molar ratio (DMG /
By setting Pd 2 in the solution after pH adjustment to 2 or more, the effect of separating Pd at a higher removal rate could be obtained. This Pd separation method is particularly effective for separating Pd from a Pd-containing aqueous Pt solution obtained by a smelting process. Further, high-purity Pt can be obtained by crystallizing Pt from the aqueous solution of Pt from which Pd has been separated by the method of the present invention.

[Brief description of the drawings]

FIG. 1 is a flowchart showing a step of recovering platinum (Pt step) in a smelting step.

FIG. 2 is a flowchart showing a palladium removal step (Pd removal step) of the present invention.

FIG. 3 is a graph showing the effect of neutralization pH on Pd removal.

FIG. 4 is a graph showing the effect of the amount of DMG added on Pd removal.

Claims (4)

[Claims] An aqueous solution containing platinum and palladium is adjusted to a pH of more than 8, and then dimethylglyoxime is added to separate the palladium. How to separate. 2. The method according to claim 1, wherein the amount of dimethylglyoxime added is 2 or more in molar ratio to palladium in the liquid. 3. The method according to claim 1, wherein the aqueous solution containing platinum and palladium is an aqueous solution obtained from a platinum extraction step in a smelting step. 4. A method for recovering high-purity platinum from an aqueous solution containing platinum after separating palladium by the method according to claim 1.