JPH06192866A - Production of potassium dicyanoaurate - Google Patents

Abstract

PURPOSE:To improve dissolution efficiency by using a granular gold bullion put in a titanium vessel as the anode and setting a cathode plate through a diaphragm in an electrolytic cell of a potassium cyanide soln. CONSTITUTION:When potassium dicyanoaurate is produced, a granular gold bullion is placed in a titanium vessel and set as an anode in the electrolytic cell of a potassium cyanide soln., and a cathode plate is set through a diaphragm. Consequently, the surface area of the anode is increased, the time until the passivation potential is reached is prolonged because the surface area is not decreased due to dissolution, continuous operation is attained only by adding and replenishing granular gold, the conventional work for attachment and detachment of gold are not needed, and the dissolution efficiency is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing potassium dicyanoaurate used as a chemical for supplying gold for various gold plating and gold alloy plating.

[0002]

2. Description of the Related Art Potassium dicyanoaurate has been conventionally produced by an electrolytic method. In this method, a metal plate is used as a plate-shaped anode, an insoluble metal is made to face as a cathode through a diaphragm made of an ion exchange resin or ceramic, and electrolysis is performed in a potassium cyanide solution.

According to this method, the current to be applied is determined based on the magnitude of the current with respect to the surface area of the anode plate, that is, the current density, and by maintaining this current density, the anodic dissolution reaction of gold is carried out. It is something that progresses and is retained. Therefore, when the electrolysis progresses and the surface area of the anode plate is reduced to passivate the anode surface, the current value is reduced and the generation of oxygen gas is started.

Therefore, if the voltage is increased to maintain a constant current in order to secure the anodic dissolution reaction, the current value increases, but the supplied current is consumed in the oxygen generation reaction. As a result, when a plate-shaped anode is used, the entire amount of the electrode cannot be dissolved, and the current dissolution rate is about 60 to 65%.

[0005]

Therefore, the current-voltage curve when potassium cyanide is used as the electrolytic solution and the gold plate is used as the anode is shown in the experimental results in FIG. 1, and the current increases as the voltage gradually increases, Gold dissolves in potassium cyanide increasing until point a is reached. When the voltage is further increased, the current decreases and reaches point b. Then, when the voltage is increased, the current also increases, but the generation of oxygen becomes more intense, but gold is not dissolved.

In addition, the current when changing the surface area of the anode
As shown in FIG. 2, the voltage curve shows that the current value is larger as the surface area is larger at the same potential. Therefore, in the production of potassium dicyanoaurate by the electrolysis method, a constant current device is used to constantly maintain a constant current, and when the surface area becomes small due to dissolution, the voltage is increased to maintain the current value. Therefore, an electrode with a small surface area is more likely to reach the passivation potential than an electrode with a large surface area, and there is a problem that the dissolution reaction is likely to stop.

It is an object of the present invention to increase the surface area of the anode and to improve the dissolution efficiency by lengthening the time required to reach the passivation potential due to the reduction of the surface area due to dissolution.

[0008]

Therefore, according to the present invention, a granular metal ingot is placed in a titanium container, set as an anode in an electrolytic cell of a potassium cyanide solution, and a cathode plate is set via a diaphragm. Is characterized by. The container may have any shape such as a dish or a bowl, and may be a mesh or a perforated container having a high solution passing property.

The cathode plate is not limited to gold, but may be any material such as titanium or stainless steel. By doing so, the amount of gold input can be kept low and the surface area can be increased, which improves the material management and improves the dissolution efficiency.
I was able to raise 20%.

The granular processing method can be performed by pouring molten metal into water.

[0011]

[Examples] 21.5 Kg of bare metal is melted by heating in a graphite crucible, and the molten metal is gradually poured into water to produce granular gold. This is evenly placed in four titanium baskets (150 × 300 × 25 mm) to form an anode.

As the cathode, a metal plate (150 × 300 × 1 mm)
Two sheets were prepared and electrolyzed in a 20% potassium cyanide solution through a birefringent membrane at 60 ° C. and 160 A for 18 hours. As a result, 18.6
Kg was dissolved, and the dissolution rate was 86.5%. This solution was subjected to the steps of general filtration-concentration-cooling-crystal collection-drying to obtain crystals of potassium dicyanoaurate.

Next, as a comparison, an example of the conventional technique will be described below. 27.8 kg of gold metal is heated and melted in a graphite crucible, and four electrode plates of 150 × 300 × 8 mm are produced by casting, which is used as an anode. As the cathode, a gold plate (150 x
Two sheets (300 × 1 mm) were prepared and electrolyzed in a 20% potassium cyanide solution through a birefringent membrane at 60 ° C. and 160 A for 18 hours.

As a result, 17.4 Kg was dissolved and the dissolution rate was 62.3.
% Met. This solution was subjected to the steps of general filtration-concentration-cooling-crystal collection-drying to obtain crystals of potassium dicyanoaurate.

[0015]

According to the present invention described in detail above, the granular metal ingot is placed in a titanium container, set as an anode in an electrolytic bath of a potassium cyanide solution, and a cathode plate is set via a diaphragm. As a result, it has the effect of greatly improving the melting efficiency compared to the conventional anode of the plate material, and it becomes possible to work continuously just by adding additional granular gold, and the work of attaching and detaching the conventional metal plate is unnecessary. There is an effect.

Further, the anode has the effect that the expensive gold bullion can be economically operated because the number of manufacturing steps of the granular material is smaller than that of the conventional plate material.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between current and voltage when a gold plate is used as an anode in an electrolytic solution.

FIG. 2 is a graph showing the relationship between current and voltage when the surface area of an anode metal plate is changed.

Claims (1)

[Claims] 1. A process for producing potassium dicyanoaurate characterized in that a granular metal ingot is placed in a titanium container, set as an anode in an electrolytic bath of a potassium cyanide solution, and a cathode plate is set through a diaphragm. Method.