JPS63186898A - Treatment of plating bath solution incorporating gold cyanide - Google Patents

Abstract

PURPOSE:To perform the purifying treatment of a plating bath soln. incorporating gold cyanide quickly with high efficiency, by regulating the pH of the plating bath soln. to specified value and pressurizing this soln. and passing it through a reverse osmosis membrane. CONSTITUTION:A plating bath soln. incorporating recovered gold cyanide is transferred to a raw liquid tank 1 and the pH is regulated to 4-7. This plating bath is pressurized at about 25-40kg/cm<2>-G with a high-pressure pump 5 and passed through a reverse osmosis membrane 2 and separated into concentrate 4 and permeated liquid 3 and the concentrate 4 is returned to the raw liquid tank 1, circulated and treated. Further as the reverse osmosis membrane, a cellulose acetate-base membrane and a nylon-base membrane are used. Impurities incorporated in the raw liquid tank 1 are concentrated as the return of the concentrate is repeated and the operation is finished at a point of time wherein the osmotic pressure of the raw liquid is made equal to the operation pressure and permeated liquid 3 is not drawn out. Thereby the purification of the plating bath soln. incorporating gold cyanide is easily performed in a short time and it can be reutilized.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention enables reuse as a plating bath solution by treating and purifying a plating bath solution containing gold cyanide used for gold plating. Regarding how to.

[Conventional technology]

Impurities such as iron, nickel, and chromium brought in from objects to be plated during the plating process are accumulated in the gold plating bath solution containing gold cyanide, so that they do not adversely affect the plating process. In order to avoid this, it is necessary to periodically renew the plating bath solution. Conventionally, the plating bath solution contaminated with impurities is collected by a collection company, and the oxidation and reduction processes are repeated to convert the gold cyanide to pure gold. After refining, the raw processing method involves processing gold cyanide again and reusing it as a raw material for plating, which has the problem of metal loss occurring during refining and requiring a large amount of expense and processing time.

[Problems that the invention attempts to solve]

The present invention solves this problem and provides a method for easily processing a plating bath solution containing gold cyanide contaminated with impurities etc. so that it can be reused.

[Means for solving problems]

The present invention improves the pH value of gold cyanide-containing gold bath solution to 4.
After adjusting the temperature to ~7, the plating bath solution containing gold cyanide is passed through a reverse osmosis membrane (hereinafter referred to as OA membrane) while pressurizing, so that the gold cyanide is efficiently left in the permeate as it is. It is characterized by being able to be collected and chopped efficiently and quickly so that it can be reused as a raw material.

It is known that when an aqueous solution is passed through an OA membrane, most of the solutes are blocked from passing through the membrane surface, so that the solution that has passed through the CA membrane has properties close to pure water.

After adjusting the pH value of the plating bath solution containing gold cyanide stored in the stock solution tank of the present inventor to 4 to 7, the solution was made to pass through the CA membrane while being pressurized to 25 to 40 ψ.
The plating bath solution containing gold cyanide that has passed through the A membrane and the OA
By separating the concentrated liquid that does not pass through the membrane and circulating the concentrated liquid that does not pass through the OA membrane into a stock solution tank, impurities such as iron, nickel, and chromium that are harmful to plating work are removed. CA the removed clean plating bath solution.
We have discovered a method for treating solutions containing gold cyanide that are collected as permeate through membranes.

In the present invention, the impurities in the stock solution tank are concentrated as the circulation continues, and the osmotic pressure of the stock solution gradually increases, so that the osmotic pressure of the stock solution becomes equal to the operating pressure, and no permeate is produced. Finish your work in time.

[Function] In the present invention, the pH value of the plating bath solution containing gold cyanide is 4 to 4.
The reason for limiting the value to 7 is that the recovery rate of gold cyanide is hardly affected by the pH value, but the range in which the OA membrane is used is when the pH value is 4 to 7.
This is because the sufficient effect of CA exhibition cannot be found outside this range.

In addition, commercially available cellulose acetate-based membranes and nylon-based membranes are usually used as CA membranes, both of which operate under the operating pressure shown in Figure 2.
As shown in the gold cyanide bath material permeability curve and the operating pressure-permeated liquid amount curve in FIG. 3, there are only slight differences in the transmittance and permeated liquid amount with respect to the operating pressure.

〔Example〕

Example 1 The solution in the recovery tank of a factory that has a collection tank for metsa bath solution containing gold cyanide installed next to the gold plating bath was transferred to the stock solution tank 1 shown in Figure 1, and while stirring. The pressure was increased to 35 mm using a high-pressure pump 5, and the liquid was passed through a cellulose acetate reverse osmosis membrane.

The plating bath solution containing gold cyanide sent out from the stock solution tank 1 is separated into a concentrated solution 4 and a permeated solution 3, and the osmotic pressure of the solution reaches the operating pressure within 45 minutes from the start of liquid flow. became equal. At that point, the outflow of the permeate stopped. When we analyzed the composition of the concentrate and permeate, as shown in Table 1, the impurities iron, nickel, and chromium in permeate 3 were significantly reduced, and the recovery rate of gold as gold cyanide was significantly reduced. reached 99.5%.

Table 1 Example 2 Using waste liquid from an electroless gold plating bath as the treatment solution,
The results when the degree of pressurization of the solution was set to 3C19, Kay-〇 are as shown in Table 2, and as in Example 1, the removal rate of impurities is high and the gold recovery rate as the target gold cyanide is achieved. Mo9
It was 7.9%.

The time required for this treatment was 60 minutes.

Table 2 Comparative Examples The gold cyanide recovery rate using the oxidation-reduction method was 96%. Further, the processing time required 150 hours for processing 1001.

〔Effect of the invention〕

By implementing the present invention, a plating bath solution containing gold cyanide can be purified quickly and with high efficiency. Furthermore, in addition to significantly extending the renewal period of the plating bath solution, this method is also effective in eliminating the causes of plating defects, and provides significant economic benefits compared to conventional redox treatment methods. .

[Brief explanation of the drawing]

Figure 1 shows a schematic diagram of the process of implementing the present invention, Figure 2 shows changes in solute permeability due to changes in operating pressure due to the permeable membrane material, and Figure 3 shows changes in permeated liquid amount due to changes in operating pressure due to the permeable membrane material. FIG.

Claims (1)

[Claims] (1) The pH value of the plating bath solution containing gold cyanide is 4 to 7.
1. A method for treating a plating bath solution containing gold cyanide, which comprises adjusting the solution to a plating bath solution and then passing the solution through a reverse osmosis membrane under pressure.