JPS58210129A - Production of high-purity gold - Google Patents

Abstract

PURPOSE:To produce high-purity gold having >=99.99% purity efficiently, by reducing the greater part of gold from a cyanoauric acid soln. contg. impurities with a reducing agent and filtering the same, reducing the remaining gold together with the impurities, mixing the resulted impure gold with the above-mentioned soln. and melting the same. CONSTITUTION:A reducing agent such as Al is added to a cyanoauric acid soln. contg. impurities such as silver, copper, Ni, Pt or the like to reduce the greater part of gold. The reduction curve 2 of impurities in this case rises sharply when the rate of reduction in a reduction curve 1 for gold exceeds 95% as shown in the figure; therefore, the reduction is stopped just before the curve rises. The greater part of high-purity gold having >=99.99% purity is filtered and recovered from said soln., whereafter the impure gold is fully reduced from the soln. contg. gold in a decreased concn., to obtain impure gold. The impure gold is then remelted to prepare a cyanoauric acid soln. Said soln. is mixed with the next cyanoauric acid soln. and the soln. is subjected again to the reduction treatment. Gold having high purity is recovered in succession by repeating the above-mentioned operations.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing high-purity gold, and in particular a method for efficiently producing high-purity gold from a cyanauric acid solution, including silver, copper, nickel, and iron.

This is a method for producing high-purity gold with a purity of 99.99% or more from a solution containing elements other than gold, such as platinum and palladium.

Generally, high-purity gold with a purity of 99.99% or higher is produced using an electrolytic refining method known as the wall will method, but this electrolytic refining method usually contains 40 to 80 g(1)/e of gold. It requires an electrolytic solution and a high-purity gold plate for the cathode, and also requires liquid management such as impurities in the electrolytic solution, which is a disadvantage in terms of efficiency in producing high-purity gold at 5F. On the other hand, as a method for reducing a solution of gold cyanide and auric acid using a reducing agent, zinc and conogel are used. A method is known that uses a metal such as aluminum. However, with reducing agent '1
In method A7c, other impurities are also reduced at the same time as gold is reduced, so it was not possible to produce high purity gold with a purity of 99.99% or higher.

The material of the present invention was created as a result of intensive research in view of the above-mentioned drawbacks and the discovery of a method for efficiently producing high-purity gold.

The present invention provides a method for producing high-purity gold from a cyanauric acid solution containing impurities. After most of the gold is reduced and filtered out using a reducing agent, the remaining gold is reduced together with the impurities to make it impure. This is a method for producing high-purity gold, which is characterized in that the impure gold is made into pure gold, and then the impure gold is dissolved as cyanauric acid and mixed into the subsequent cyanauric acid solution.

(2) The present invention is based on the fact that when reducing with a reducing agent, gold is reduced first in a cyanauric acid solution, and then impurities are rapidly reduced. 4' In other words, in Figure 1, the gold reduction curve 1 shows that the amount of gold reduced is approximately proportional to the amount of reducing agent added, but the impurity reduction curve 2 shows that the amount of gold reduced is 95%.
When it exceeds , it rises rapidly. Therefore, the purity is 99.
To produce high purity gold of 99% or higher, the impurity tolerance is O.
, 1%, which is extremely low, so it is necessary to stop just before standing up. In the present invention, most of the gold is separated by reduction filtration.

First, obtain high-purity gold. Then, all the gold is reduced from the solution whose concentration has decreased (to obtain impure gold. After that, the impure gold is redissolved to obtain a cyanide-auric acid solution, and this is mixed into the cyanide-auric acid solution. The reduction curve 2 of impurities is determined by the type and concentration of impurities, but since the reduction curve 1 of gold is almost a straight line, the amount of impurities reduced can be calculated by assuming the amount of reducing agent added. Therefore, even if the method for applying M according to the present invention is carried out continuously, the concentration of impurities will not accumulate and increase.

(3) Examples and conventional examples will be explained below.

[Example 1] 5 kg of ornamental scraps containing 75% gold were dissolved in a potassium cyanide solution and the If! A gold-containing solution was obtained. 336 g of aluminum was added to this solution to reduce most of the gold. When one clear liquid was analyzed, the gold concentration was 3.
．． 1g/j! Met. In addition, when the reduced gold was filtered, washed and dried, it turned out to be 3673.41! I got gold powder. When the purity of this gold powder was analyzed, it was found to be 99.996% pure. On the other hand, when the U:Ki solution was further reduced with 8 g of aluminum, 73.4 gold powder was obtained. When this was analyzed, it was 99.70%. As described above, according to the manufacturing method of the present invention, gold with a high purity of 99.996% can be produced with a purity of 98%.
could be produced with a yield of .

[Conventional Example 1] 344 g of aluminum was added to the same solution as in Example 1 to completely reduce and precipitate gold. When the reduced gold was filtered, washed and dried, it yielded 3747.4g of gold powder. Also.

When this gold powder was analyzed, the purity was 99.97% (
4) Ta. The gold recovery rate at this time was 99.9V6.

[Example 2] 5 kg of crude gold containing 99.62% gold, 0.34% copper, 0.03% string and other trace amounts of iron and palladium was dissolved in an aqueous solution of sodium chloride. I got a hotspot.

This liquid was divided into 9E portions, and 823g of auxiliary ship was added to one of the liquids, yielding 2477.2g of gold powder. When the purity of this gold powder was analyzed, it was found to be 99.992% pure.

[Conventional Example 2] The other 91! When 832g of zinc was added to the solution, 25
Obtained 00.6g of gold powder. When this gold powder was analyzed, 9
The purity was 9.94%.

As described above, according to the manufacturing method of the present invention, 99.992
Gold with a purity of 4% could be produced with a yield of 99%.

As detailed above, in the production method of the present invention, if L is 9.
High-purity gold of 9.99% or higher can be efficiently produced regardless of the LI4 degree of impurities, and it can be repeatedly produced.

However, if the concentration of impurities does not accumulate, then There is a stray J result.

[Brief explanation of drawings]

Figure 1 is a diagram showing the content of gold and impurities relative to the amount of reducing agent added. l - Reduction curve of gold, 2 - Reduction curve of impurities Applicant: UL Naka Kikinzoku Kogyo Co., Ltd. (6)

Claims (1)

[Claims] In a method for producing high-purity gold from a cyanide-auric acid solution containing impurities, most of the gold is reduced and filtered using a reducing agent, the remaining gold is reduced together with impurities to make impure gold, and then the impure gold is cyanated. A method for producing high-purity gold, characterized by dissolving it as gold acid and mixing it into a subsequent cyanide-auric acid solution.