JPS58741B2 - How to collect money - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for efficiently recovering gold contained in gold plating cleaning wastewater by adsorbing it onto a polymeric substance such as nylon.

In the gold plating industry, gold in gold plating cleaning wastewater is
Concentrated solutions are recovered by entrusting them to a processing company, but when a large amount of dilute solutions with a concentration of 5 ppm or less are produced, ion exchange resins are usually used to recover them.

However, generally a strongly basic ion exchange resin is used to adsorb gold as a complex compound of cyanide, which has a strong adsorption force, and no eluent suitable for desorbing it has yet been found, and the regeneration process is difficult. It was difficult to put on and take off.

Currently, gold is recovered by incinerating the ion exchange resin that has adsorbed gold in an electric furnace, high-frequency furnace, etc.

In addition, gold is adsorbed using a weakly basic ion exchange resin,
Some attempts have been made to elute it, but in this case,
Since a concentrated solution containing sodium hydroxide and potassium cyanide had to be used for elution, processing of the solution after gold desorption became a challenge.

As a result of intensive research to overcome the difficulties of these conventional methods, the inventors of the present invention have succeeded in efficiently removing gold even from a dilute solution by using a polymeric material with acid amide bonds as an adsorbent. It has been discovered that gold can be adsorbed and then easily desorbed to achieve reduced gold recovery, and based on this knowledge, the present invention has been accomplished.

Plating cleaning wastewater containing gold as Au(CN)2 is brought into contact with a polymeric material having acid amide bonds as at least a part of its constituent units under acidic conditions, and the gold contained in the wastewater is transferred to the polymeric material. Recovery of gold from gold plating washing wastewater, which is characterized by adsorbing gold onto a substance and then contacting the polymeric substance adsorbed with plating with an alkaline aqueous solution to desorb the gold adsorbed to the polymeric substance. The present invention provides a method.

Nylon is preferable as the polymeric substance having an acid amide bond as a structural unit in at least a portion thereof used in the present invention.

The form of this polymer substance is not particularly limited and may be used in any form such as fibrous, pellet, or membrane, but fibrous is most preferred from the viewpoint of adsorption amount.

The following table shows the results of adsorption tests using various polymeric substances as adsorbents.

In this test, an aqueous solution of pH 3 containing 1100 pp of gold as (1-)potassium dicyanoaurate was used, and the adsorbent 1
The test was carried out at a temperature of 25°C.

In the method of the invention, adsorption of gold in waste water is carried out under acidic conditions.

When using 1-1 nylon fiber, the total concentration in the aqueous solution is 50
If the amount is around ppm, almost all of the gold contained in 100ml can be adsorbed.

Gold in gold plating cleaning wastewater is usually gold cyanide complex Au (CN
)2 and is quite stable, and there is no risk of generating cyan gas in a dilute acid aqueous solution, but the p
If H becomes too low, the gold-cyanide complex may be decomposed.In terms of the adsorption amount of 31 to 2 gold to the polymeric substance, the lower the pH, the better.

Therefore, when gold is adsorbed onto a polymeric substance having an acid amide bond, the pH is preferably kept at about 3, preferably within the range of pH 3 to 5.

In the present invention, the adsorption rate of gold increases with temperature;
Although the adsorption rate at 50°C is approximately twice that at 25°C, the final amount of adsorption does not change much.

In the present invention, C is this.

The gold can be concentrated and eluted by eluting the polymer substance having at least a part of the acid amide bond as a structural unit, on which gold has been adsorbed, according to a conventional method.

Usually, as the eluent, use an aqueous solution of ANO-L-hI, preferably an alkaline aqueous solution with a pH of 1 to 14.

The eluent contains several whites to several ppm of shea]
/ When ions coexist, the desorption rate increases.

The influence of the preparation during desorption is similar to that during adsorption; the desorption speed becomes more difficult as the operating temperature rises.

Although the method of the present invention can be carried out batchwise, it is more efficient to carry it out continuously using the Kasim method.

According to the method of the present invention, gold can be efficiently recovered from gold plating washing waste water having a relatively low gold content.

The polymer 4, such as nylon, used as an adsorbent.
The i-quality material is easy to regenerate and remove, and can be used repeatedly.

Moreover, since the adsorbent of the present invention is cheaper than the ion exchange resin, it is sufficiently profitable to use one or more adsorbents to recover gold after adsorption treatment.

Next, the present invention will be explained to Kiraniminamigumi based on Examples 3.
) Cut the IOP to a length of about 3 mm, and cut the IOP into a 2-diameter column (
(with thermal jacket).

When gold plating wash waste water of pH 3 containing 5 ppm gold was passed through this column at a temperature of 50° C. and a rate of 30 ml/ynin, no gold was detected in the solution until 7°51 of the solution had flowed out.

Next, like this 1. 1000 ppp of cyanide (as KCN) at pH 10 was added to a column that had completely adsorbed gold.
m at a temperature of 50°C and a flow rate of 30 m1/
When flowing at vtin, all the gold is eluted by the time 300ml flows out, and the average concentration of gold in the eluate is 260p.
It was pm.

Claims (1)

[Claims] Plating cleaning wastewater containing gold as Au(CN)2- is brought into contact with a polymeric material having a monoacid amide bond as a part of its constituent units under acidic conditions to remove the gold contained in the wastewater. After adsorbing the plating onto the polymeric material, the polymeric material adsorbed with the plating is brought into contact with an alkaline aqueous solution to desorb the gold adsorbed onto the polymeric material. How to collect money.