JP3229218B2 - Platinum purification method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for extracting a noble metal, and more particularly to a method for remarkably increasing the purity of platinum.

[0002]

2. Description of the Related Art Japanese Patent Publication No. 1-30896 discloses a chloride aqueous solution containing gold and a platinum group metal as valuables.
A method is disclosed for continuously and selectively removing gold, platinum, ruthenium, osmium, palladium, and iridium. The separation method by this method is summarized for each metal. (A) Ruthenium and osmium: chloride-containing aqueous solution is oxidized and removed as a precipitate; (b) Gold: (a)
(C) Palladium: dialkyl sulfide (DHS-di-n-octyl sulfide, di-n-sulfide) after treatment with (b)
Solvent extraction into hexyl, methyl-n-decyl sulfide, etc.); (d) Platinum: After treatment with (b), the platinum is solvent extracted with tributyl phosphate (TBP) and oxidized to platinum (IV). Is converted to ammonium chloroplatinate, and platinum is recovered by igniting the salt. The specific conditions of the platinum extraction (d) are as follows: the platinum-containing organic phase is scrubbed with 5N hydrochloric acid, then the scrubbed organic phase is stripped with 0.2N hydrochloric acid, and the stripping solution is oxidized with chlorine gas. To platinum (IV), and then ammonium chloride platinate is precipitated with an ammonium chloride solution.

Incidentally, hexachlorohydrochloric acid-H ₂ [PtCl
_6] - to cause a reaction of the following equation by adding NH ₄ Cl -containing aqueous hydrochloric acid solution, thereby crystallizing the hexachloro ammonium salts are well known, crystallization of platinum also by this method supra Publication manner Are getting things. H ₂ [PtCl ₆ ] + 2NH ₄ Cl → (NH ₄ ) ₂ [P
tCl ₆ ] + 2HCl

[0004]

SUMMARY OF THE INVENTION In the treatment process described in the above-mentioned publication, tellurium is contained in the liquid before ruthenium removal in an amount of 2.1 g / l.
L and copper are contained at 0.2 g / L, and the degree of removal of these impurities in the subsequent processing shows that the following concentration (g / L) is obtained in the platinum extraction step. Raw material solution Raffinate scrubbing solution Stripping solution Te 0.6 0.23 <0.005 0.06 Cu 0.06 0.05 0.02 <0.01 In the method of the above-mentioned publication, tellurium and copper are used in addition to organic solvent extraction. No method has been implemented to remove.

However, the present inventors have studied the behavior of these impurity elements in the process of extracting and recovering noble metals, and found that trace amounts of impurities were precipitated by hydrolysis at the time of adding an aqueous ammonium chloride solution at the stage of platinum crystallization. For example, it has been found that tellurium precipitates as TeO ₂ and copper precipitates as copper hydroxide, lowering the purity of platinum.

The present invention eliminates the above-mentioned reduction in purity due to tellurium in a method for purifying platinum including a step of precipitating platinum as an ammonium chloride salt by bringing an aqueous solution containing H ₂ PtCl ₆ into contact with ammonium chloride. First, H ₂ Pt
In a method for purifying platinum comprising a step of precipitating platinum as an ammonium chloride salt by contacting an aqueous solution containing Cl ₆ with ammonium chloride, the aqueous solution containing H ₂ PtCl ₆ is brought to pH 9 prior to contacting with the ammonium chloride.
~ 11, then neutralization to pH 5 ~ 7, filtration after each treatment, and the acid concentration of the filtered solution after the neutralization treatment is 0.05N or more Secondly, in a method for purifying platinum comprising a step of precipitating platinum as an ammonium chloride salt by contacting an aqueous solution containing H ₂ PtCl ₆ with ammonium chloride, wherein the ammonium chloride Prior to contact with water, the aqueous solution containing H ₂ PtCl ₆ (hereinafter referred to as “aqueous chloroplatinic acid solution”) is adjusted to pH 9 to 11, and then adjusted to pH 9 to 11.
Neutralizing to 5-7, filtering after each treatment, and adjusting the acid concentration of the ammonium chloride aqueous solution to 0.07.
The point is that there is a step of adjusting the number to 5 or more. Hereinafter, the present invention will be described in detail with reference to the flowchart shown in FIG.

A tin ore smelting distillation residue containing a noble metal,
Anode slime and other raw materials during electrolytic smelting of copper are subjected to chloride leaching, and silver chloride and lead chloride are separated as leaching residues from precious metals.

Subsequently, dibutyl carbitol (DBC)
Extract gold from the chloride leaching solution, extract palladium from the remaining leaching solution with n-hexyl sulfide (DHS), and subsequently extract platinum from the chlorinating leaching solution with tributyl phosphate (TBP). TBP with extracted platinum
Is scrubbed with hydrochloric acid to obtain C contained in TBP.
Impurities such as u, Se and Pb are removed in hydrochloric acid. Thereafter, back extraction is carried out from the TBP with water or a highly diluted acid or alkali solution to take out a chloroplatinic acid solution.

Subsequently, in order to remove impurities such as Cu and Te, the chloroplatinic acid solution is adjusted to pH 9-11, and then p
Neutralize to H5-7 and filter after each neutralization. If the pH for neutralization is too low, the impurities do not precipitate, and if the pH is too high, the impurities are redissolved and cannot be separated from platinum. Further, it is difficult to remove a plurality of impurities by one-stage neutralization because the pH at which precipitation occurs differs depending on the impurities. For example, tellurium has a minimum solubility at pH = 6 and remains in the platinum solution whether the pH is too high or too low. For copper, pH
= 3, precipitation starts as hydroxide, but pH = 1
If it exceeds 1, the hydroxide is redissolved. For this reason, the pH range is determined as described above. PH 9-1
Precipitating and removing copper by neutralization at 1 and subsequent filtration, then precipitating and removing tellurium by neutralization at pH 5-7 and subsequent filtration, greatly reducing these grades Can be.

As described above, the chloroplatinic acid solution is neutralized once from the alkali side, and the HC is adjusted to 0.05N or more.
Adjust the acid concentration with 1 or the like. At this time, a preferable acid concentration is 0.05 to 1 normal. Adjustment of the acid concentration is performed on the filtrate of the second-stage filtration or on an aqueous ammonium chloride solution. In the subsequent step of adding ammonium chloride, in a solution in which the acid concentration has not been adjusted, the pH locally increases and precipitation of TeO ₂ or the like occurs, but the local pH increase is prevented by adjusting the acid concentration in advance. And Te
Precipitation of O _{2 and the} like can be prevented.

Subsequently, when platinum is precipitated by adding ammonium chloride, the tellurium concentration in the precipitate becomes very low. By preliminarily adjusting the acid concentration of the aqueous solution of ammonium chloride to be added at this time to be 0.05N or more, precipitation of TeO ₂ or the like can be prevented for the above-described reason. The precipitate of ammonium chloroplatinate is thermally decomposed by strong heat to obtain sponge platinum. Hereinafter, the present invention will be described in more detail with reference to examples.

[0012]

EXAMPLE Noble metals were extracted according to the flow chart of FIG. 1 under the following conditions. Distillation residue (Pd content: 33%, Pt content: 1.3%, Au content: 15.6%, Te content: 44.5%, Cu content: 2.0%, total of other impurities Content: 3.6%;
The solution leached with 4 L of chloride leaching solution was brought into contact with 0.2 L of DBC to extract and remove gold. Liquid from which gold has been removed and sulfide-n
0.189 L of hexyl was contacted to extract and remove palladium. Liquid with palladium removed and TBP 0.38
After contact with L, the TBP is replaced with 5N HCl-0.42 L
And then back-extracted with 1.24 L of water.
The back-extracted hydrochloric acid solution was adjusted to pH 10 with an aqueous NaOH solution.
And filtered. Next, the filtrate was neutralized to pH = 6 with an aqueous HCl solution and filtered. In each of the two filtration operations before and after, roughing was performed using filter paper, and then fine substances were removed using a membrane filter.

Then, as an embodiment of the present invention, ammonium chloride was dissolved in water in a liquid whose concentration was adjusted to 0.1 N by adding hydrochloric acid to a filtrate from which impurities were separated by filtration after pH adjustment, and HCl was added. Platinum crystallization was performed using a solution adjusted to a concentration of 0.1N. For comparison, Comparative Examples 6 to 8
Performs crystallization of platinum in a solution in which ammonium chloride is dissolved in water. Comparative Example 9 eliminates filtration of impurities by pH adjustment, and adds ammonium chloride in a solution dissolved in water to crystallize platinum. went. After filtration with filter paper, filtration was performed with a membrane filter. Table 1 shows the quality of the finally obtained platinum. (Below)

[0014]

[Table 1]

From Table 1, it can be seen that when the acid concentration is adjusted, the final grades of Te and Cu are remarkably low at less than 10 ppm.

After that, heating was performed at 600 ° C.
95% or more of sponge platinum was recovered.

[0017]

As described above, according to the present invention, platinum in which the concentrations of tellurium and copper are on the order of ppm can be obtained, and this performance can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a main part of a flowchart of the method of the present invention.

Claims (2)

(57) [Claims] 1. A method for purifying platinum, comprising the step of contacting an aqueous solution containing H ₂ PtCl ₆ with ammonium chloride to precipitate platinum as an ammonium chloride salt.
Prior to contact with the ammonium chloride, the H ₂ PtCl
_The aqueous solution containing ₆ is adjusted to pH 9 to 11, and then adjusted to pH 5 to 11.
7, neutralizing and filtering after each treatment;
And the acid concentration of the filtered solution after the neutralization treatment is 0.05
A method for refining platinum, comprising a step of adjusting the content to a value exceeding a specified value. 2. A method for purifying platinum, comprising the step of contacting an aqueous solution containing H ₂ PtCl ₆ with ammonium chloride to precipitate platinum as an ammonium chloride salt.
Prior to contact with the ammonium chloride, the H ₂ PtCl
_The aqueous solution containing ₆ is adjusted to pH 9 to 11, and then adjusted to pH 5 to 11.
7, neutralizing and filtering after each treatment;
And a step of adjusting the acid concentration of the aqueous ammonium chloride solution to 0.05 N or more.