JP2879582B2 - Purification method of cyanuric diaurate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to potassium cyanide diaurate, sodium cyanide diaurate and the like used as a gold source in a gold plating bath employed in a gold plating step. Cyanodiaurate, ie, tetracyanoaurate (III), M ^I [Au (CN) ₄ ] (M
^I is a monovalent cation).

[Prior Art] Potassium cyanide diaurate is obtained by replacing potassium dichloroaurate with potassium cyanide. Also, sodium cyanide diaurate is obtained by replacing sodium diaurate chloride with sodium cyanide. These reactions can be represented by the following equations.

M [AuCl ₄ ] + 4MCN → MAu (CN) ₄ + 4MCl (M in the formula represents K or Na) (1) As can be seen from the formula (1), potassium chloride is used as a by-product of this reaction. Or sodium chloride forms. In order to remove these by-products, a method of crystallizing potassium diaurate potassium KAu (CN) ₄ or sodium cyanide diaurate NaAu (CN) ₄ in an aqueous solution and performing solid-liquid separation, A method of extracting potassium cyanide diaurate or sodium cyanide diaurate with ethanol has been used.

[Problems to be Solved by the Invention] In the prior art method of crystallizing potassium cyanide diaurate or sodium cyanide diaurate in an aqueous solution carried out according to the above formula (1), these second methods are used. Since gold salts are easily soluble in water, a considerable amount of gold remains in the aqueous solution without crystallization. Therefore, the liquid obtained by solid-liquid separation after crystallization is returned to the substitution reaction system according to the above formula (1) and reused. If this is repeated many times, potassium chloride or sodium chloride is contained in the solution. As a result, the amount of potassium chloride or sodium chloride mixed into the crystallized product increases, resulting in the product having a low purity that does not meet its intended purpose. For this reason, in the above-mentioned conventional method, the solution after the crystallization step cannot always be returned to the substitution reaction step and reused, and at least a part of the solution is separately treated to remove gold in the solution. It is absolutely necessary to provide a recovery step. As described above, the increase in the number of the secondary recovery steps, the low yield of gold in the recovery step, and the reduction in the direct yield of gold due to this increase are one of the important factors that increase the product cost.

On the other hand, the solvent extraction method using ethanol of the prior art
The solubility of potassium chloride in ethanol is 0.08KCl / C ₂ H ₅ OH
Because of the relatively high value of 100ml (Atherton Seidel
l, “Solubilities”, 1953, D. Van Nosthrand Company p.
776, p.780), and it is difficult to completely remove potassium chloride.

[Means for Solving the Problems] As a result of earnest studies to solve the above problems, the present inventor has found that acetone is used as a solvent for potassium cyanide diaurate or sodium cyanide diaurate. The inventors have found that the purification of these cyanuric diaurates can be advantageously performed, and have reached the present invention.

[Action] The following has been found by the study of the present inventors.

Potassium cyanide diaurate [KAu (CN) ₄ ] and sodium cyanide diaurate [NaAu (CN) ₄ ] are both easily dissolved in acetone and have high solubility. On the other hand, potassium chloride (KCl) and sodium chloride (N
aCl) has very low solubility in acetone,
Nearly 0. Therefore, by utilizing this property of acetone, crude KAu (CN) containing KCl as an impurity
₄ or crude NaAu (CN) ₄ containing NaCl as an impurity is dissolved in acetone to perform solid-liquid separation, and acetone is evaporated and removed from the obtained liquid by means of reduced pressure or the like, so that highly pure KAu ( CN) ₄ or NaAu (CN) ₄ can be obtained.

If the solvent extraction method using acetone as the organic phase is used, the liquid after the completion of the substitution containing the cyanuric diaurate, which cannot be returned to the substitution reaction system of the above formula (1), is used. Goldate can be easily recovered.

[Example 1] Potassium cyanide second aurate reagents, KAu (CN) ₄ · 0.5
H ₂ O (300.0 g in gold) and reagents potassium chloride and KCl (300
g) was used to perform a purification test on the mixed sample according to the following procedure.

The mixed sample was dissolved in reagent grade acetone 2 and insoluble KCl was removed by filtration. Further, this insoluble content was sufficiently washed with acetone, and the washing solution was combined with the filtrate. The filtrate was transferred to an evaporator, and the pressure was reduced to remove acetone by evaporation. The remaining solid was dried at 80 ° C. for several minutes until the weight became constant, and purified cyanide
The results are shown in Table 1 below, which were analyzed by using potassium aurate.

[Effect of the Invention] As is clear from the course of Example 1, in the purification of the crude cyanide diaurate, the direct yield of gold was almost 10%.
It is close to 0%, and the chlorine content of the impurity is almost 0. It is evident that acetone is a very good solvent for the purification of potassium diaurate cyanide or sodium diaurate cyanide.

Claims (3)

(57) [Claims] 1. A cyanide comprising dissolving a cyanuric diaurate containing impurities in acetone, separating the solids and liquids to remove impurities as solids, and evaporating and removing acetone from the obtained liquid fraction. A method for purifying an activated secondary gold salt. 2. The method according to claim 1, wherein said dicyanoaurate is potassium diaurate, KAu (CN) ₄ and the main impurity is KCl. 3. The cyanuric diaurate is sodium cyanide diaurate, NaAu (CN) ₄ , and the main impurity is NA.
2. The method according to claim 1, wherein Cl is Cl.