JPH0555575B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to an improvement in a gold refining method. (Conventional techniques and problems) Traditionally, gold purification methods have been using aqua regia or HCl.
−Cl ₂ A method of dissolving low-grade gold in water and selectively reducing only the gold with a reducing agent such as hydrazine, HCl
The method of electrolyzing low-grade gold in acidic conditions is well known. However, the former method requires equipment and personnel for exhaust gas treatment, and the latter method uses hydrochloric acid as the electrolyte, which generates Cl ₂ gas at the anode, resulting in low electrolysis efficiency. For this reason, the present inventor considered using a halogen instead of hydrochloric acid as an electrolytic solution and tried an iodine electrolysis method, but this iodine electrolysis method was unable to increase the purity of gold. Therefore, the present inventor conducted research based on the above-mentioned electrolytic method using iodine, and developed a method that can efficiently refine low-grade gold into high-grade gold. (Means for Solving the Problems) In order to solve the above problems, the gold refining method according to the present invention uses a potassium iodide solution or a sodium iodide solution as an electrolytic solution when refining low-grade gold. Then, low-grade gold is directly dissolved by electrolytic oxidation on the anode of an electrolytic cell with a cation exchange membrane as a diaphragm, and the resulting iodoauric acid solution is heated to a pH of 12.5 or higher in the reaction layer.
It is characterized in that only gold powder is precipitated by self-reduction under controlled conditions. (Function) As described above, the method for refining gold according to the present invention can dissolve gold without depositing it on the cathode using the diaphragm electrolysis method, and the iodoauric acid solution obtained thereby can be dissolved at a pH of 12.5 or higher. By adjusting the pH to , it precipitates as gold powder through self-reduction. The gold thus obtained is of high grade of 99.991 wt% or more in the case of low-grade gold of 99.4 wt%. (Example) An example of the gold refining method according to the present invention will be described. After adjusting the pH to 11-12 using a 3M potassium iodide (KI) solution as the electrolyte, it is placed in the anode chamber 3 of the electrolytic cell 1 with the cation exchange membrane 2 as a diaphragm as shown in the drawing, Pure water was placed in chamber 4. Next, electricity was applied at 60 A/d to dissolve the gold anode with a grade of 99.4 wt%, and then the solution was sent to the reduction reaction tank 7. On the other hand, a KOH alkaline solution is generated in the cathode chamber 4.
This KOH alkali solution was sent to the reduction reaction tank 7 using the pump 6. Next, in the reduction reaction tank 7, the anode chamber solution and the KOH alkaline solution are mixed and stirred.
Adjust the pH to 12.5 or higher to self-reduce Au, and
Only powder was precipitated. Since this precipitated Au powder is separated from the solution, the precipitated Au powder in the reduction reaction tank 7
The powder is discharged from the bottom, and the Au powder floating in the liquid is
The solution was sent to the filtration tank 9 by the pump 8, the Au powder was centrifugally filtered, and the filtered Au powder was discharged outside the tank and further discharged from the bottom of the reduction reaction tank 7.
It was placed in a cleaning tank 10 together with Au powder, washed in countercurrent with washing water, and dried in a dryer 11 to obtain Au powder.
The liquid discharged from the filter tank 9 is returned to the electrolytic cell 1 by a pump 12. Gold with a grade of 99.4wt% was deposited on the Au powder obtained in this way using a conventional iodine electrolysis method.
When the quality of the Au powder was measured, the results shown in Table 1 below were obtained.

[Table] In addition, when we measured the quality of Au powder obtained by refining 90.5wt% Au using the method described above of the present invention and the conventional iodine electrolysis method, we obtained the results shown in Table 2 below. Ta.

[Table] Furthermore, when we measured the quality of Au powder obtained by refining 75wt% Au using the method described above of the present invention and the conventional iodine electrolysis method, we obtained the results shown in Table 3 below. .

[Table] As is clear from Tables 1, 2, and 3 above, the method of the example can significantly increase the purity of Au compared to the conventional method, indicating that the purification efficiency is high. (Effects of the Invention) As detailed above, the gold refining method of the present invention has the effect of efficiently refining low-grade gold into high-purity gold, which is superior to conventional refining methods. It can be said to be an innovative method that can be replaced.

[Brief explanation of drawings]

The figure is a diagram showing means for carrying out the gold refining method of the present invention.

Claims (1)

[Claims] 1. When refining low-grade gold, low-grade gold is dissolved by electrolytic oxidation directly on the anode of an electrolytic cell with a cation exchange membrane as a diaphragm using a potassium iodide solution or a sodium iodide solution as an electrolyte. A method for refining gold, which comprises adjusting the pH of the obtained iodized gold acid solution to 12.5 or higher in a reaction tank to precipitate only gold powder by self-reduction.