JPH03164428A - Method for purifying cyanoaurate - Google Patents

Abstract

PURPOSE:To produce high purity cyanoaurate in a high yield by dissolving cyanoaurate contg. impurity in acetone, separating the impurity as solid matter and removing the acetone from the resulting soln. by evaporation. CONSTITUTION:Potassium cyanoaurate contg. KCl as impurity (or sodium cyanoaurate contg. NaCl as impurity) is dissolved in acetone, solid-liq. separation is carried out and the impurity is removed as solid matter. The acetone is then removed from the resulting soln. by evaporation. High purity potassium cyanoaurate (or sodium cyanoaurate) nearly free from impurities is obtd. in a high yield.

Description

Detailed Description of the Invention [Industrial Application Field J] The present invention is directed to potassium cyanauric acid, sodium cyanauric acid, etc., which are used as a gold source in a gold plating bath employed in a gold plating process. cyanauric acid salt, i.e., tetracyanoauric acid salt M' [Au (CN
) 4 (M' is a monovalent cation) Relating to a method for purifying a crude product.

[Prior Art] Potassium cyanauric acid is obtained by replacing potassium cyanauric acid with potassium cyanide.

Moreover, sodium cyanauric acid is obtained by replacing sodium cyanauric acid with sodium cyanide. These reactions can be expressed by the following equations.

M CA u Cl 4 ko 1,4MCN
→MA u (CN) 4 + 4 MCρ(
M in the formula represents K or Na. )...As can be seen from the ω0 equation, potassium chloride or sodium chloride is produced as a byproduct of this reaction. In order to remove these by-products, a method of solid-liquid separation by crystallizing potassium cyanauric acid KAu(CN)4 or sodium cyanauric acid NaAu(CN)4 in an aqueous solution, A method of solvent extraction of potassium cyanauric acid or sodium diauric cyanide using normal ethanol has been used.

Problems to be Solved by E-Hatsushi] In the prior art method of crystallizing potassium cyanauric acid or sodium chloride cyanide in an aqueous solution, which is carried out according to the above formula (1), Since these auric acid salts are easily soluble in water, there is an equivalent amount of gold remaining in the aqueous solution without crystallizing. Therefore, the solid-liquid fraction ML after crystallization. The solution obtained in step 0 is returned to the substitution reaction system according to formula 0 and reused, but if this is repeated many times, potassium chloride or sodium/lium chloride will accumulate in the molten phase. Since the amount of potassium chloride or sodium chloride mixed into the crystallized product increases, the product becomes a product of low purity that does not meet the original characteristics. For this reason, in the conventional method described above, the solution after the crystallization step cannot always be returned to the substitution reaction step 1 and reused, and at least a part of this solution must be separately processed to remove the It is absolutely necessary to set up a process to recover the gold. The increase in the number of secondary recovery processes, the low yield of gold in the recovery process, and the resulting decrease in the direct yield of gold are among the important causes of increasing product cost. There is.

On the other hand, in the conventional method of solvent extraction with ethanol, the solubility of potassium chloride in ethanol is 0.08 gKCf.
t/(,2 Hs OHIOO-, which is a relatively high value (Atherton Seldell."So
lubilities-. 1953. D.Van
Nothrand Company p. 77B. p
．． 780), it is difficult to completely remove potassium chloride.

[Means for solving the problem] In order to solve the above problem, we conducted intensive research 1, and as a result,
The present inventor has advantageously carried out the purification of potassium cyanauric acid salts or sodium cyanauric acid salts by using acetin as a solvent ε for potassium cyanauric acid salts or sodium cyanauric acid salts. We have discovered what we can do (7) and have arrived at the present invention.

[Work] Through research conducted by the present inventor, the following was discovered.

Potassium cyanide [KA u (CN) a
] and sodium 1.lium cyanide [N a A
u(CN)4] are both easily dissolved in acetone and have high solubility. On the other hand, potassium chloride (KCL)
) and sodium chloride (NaCff) have extremely low solubility in acetone, almost close to O. Therefore, by utilizing this property of acetone, KC
Crude KAu (CN)4 with impurity I, or NaCf! Crude NaAu (CN
) 4 in acetone to give a solid-liquid content of
u(CN). can be obtained.

By using the above-mentioned solvent extraction method using acetone as the 14m phase, it is possible to extract ferric cyanide from the liquid containing ferric cyanide, which cannot be returned to the substitution reaction system of formula D. The acid salt can be easily recovered.

[Example 1] Reagent potassium cyanauric acid, KAIJ(CN)4
・Q. Using test f4, which is a mixture of 5H2 0 (300.0 g in gold) and reagents potassium chloride and KCN (300 g), a purification test was conducted on the mixed sample according to the following procedure.

The mixed sample was dissolved in 2 g of reagent grade Acerol, and insoluble KCj was removed by filtration. Furthermore, this insoluble matter was thoroughly washed with acetone, and the washing liquid was combined with the previous filtrate. This filtrate was transferred to an evaporator (1) and the pressure was reduced to remove acetone by evaporation. The remaining solid content was dried at 80° C. for several minutes until the weight became constant, and purified potassium cyanaurate was obtained.The resulting product was analyzed to obtain the results shown in Table 1 below.

(Margin below.) Table 1 [Effects of the invention] As is clear from the results of Example 1, in the purification of crude cyanauric acid salt, the direct yield of gold was approximately 10%.
It is close to 0%, and the chlorine content of impurities is almost 0. It is clear that acetone is an excellent solvent for purifying potassium cyanauric acid or sodium cyanauric acid.

Claims (3)

[Claims] (1) A cyanide solution containing impurities is dissolved in acetone, followed by solid-liquid separation to remove impurities as a solid substance, and acetone is removed by evaporation from the resulting liquid. Method for purifying diaurate. (2) The cyanauric acid salt is potassium cyanauric acid acid, KAu(CN)_4, and the main impurity is KC.
2. The method according to claim 1, wherein: l. (3) The method according to claim 1, wherein the cyanauric acid salt is sodium cyanauric acid salt, NaAu(CN)_4, and the main impurity is NaCl.