JP2005139483A - Method for collecting noble metal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for simply, continuously, and repeatedly performing a step of liquating a noble metal into an eluent from an ion-exchange resin, and a step of collecting valuable metal from the eluent. <P>SOLUTION: The method for collecting a noble metal comprises eluting the noble metal in the eluent by contacting the ion-exchange resin having adsorbed the noble metal with the eluent which is an aqueous solution of a thiocyanic acid compound, and then collecting the noble metal from the eluent by electrolysis. It is preferable to continuously circulate the eluent to a liquation tank in which the eluent is contacted with the ion-exchange resin, and to an electrolytic collection tank in which the noble metal is electrolytically collected from the eluent containing the eluted noble metal. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for recovering noble metals (gold, silver, platinum, palladium) using an ion exchange resin.

  Conventionally, for the purpose of selectively concentrating and recovering valuable metals, in particular noble metals such as gold, silver, platinum, and palladium, from wastewater treatment or dilute valuable metal-containing solutions, as described in, for example, Japanese Patent Publication No. 8-5666, Exchange resin is used. In order to separate and recover the precious metal adsorbed on the ion exchange resin used for such a purpose, a method of bringing an eluent into contact with the ion exchange resin and a method of incinerating the ion exchange resin are performed.

  In order to recover the precious metal from the eluent containing the precious metal in contact with the ion exchange resin, there are a method of separating from the eluent by electrolysis and a method of reducing by a chemical method. However, in both methods, the operation is not continuously performed until the noble metal is separated and recovered from the ion exchange resin, and the process of eluting the noble metal from the ion exchange resin into the eluent and the recovery of the noble metal from the eluent are performed. Two steps with the step were independent. This is because only the precious metal cannot be recovered from the eluent as a solid unless the ion exchange resin and the eluent are once filtered.

  In the method of recovering a noble metal from an ion exchange resin using an eluent, the noble metal is desorbed from the eluent by bringing the eluent into contact with the ion exchange resin. The amount of eluent required to process this ion exchange resin is determined by the type, concentration and amount of precious metal of the eluent, and in many cases, an elution facility for processing a large amount of eluent is required. Necessary.

  Furthermore, noble metals must be separated and recovered from the large amount of eluent by electrolysis. Therefore, in order to carry out a large amount of treatment, there has been a problem that the electrolytic equipment must be made large or the storage equipment must be made large in order to divide it into small portions.

  Further, in the recovery method in which the reduction is performed by a chemical method, since the amount of the liquid is further increased due to the addition of a reducing agent or the like, there has been a problem that it is necessary to process a larger amount of the eluent than the electrolytic treatment.

  Furthermore, both methods have a problem that the eluent after separation and recovery of the noble metal becomes waste liquid, and the load of waste water treatment is large.

On the other hand, the method of incinerating the ion exchange resin also cannot be continuously processed, and further generates toxic gas, so that there is a problem that a facility for removing the toxic gas is required.
Japanese Patent Publication No. 8-5666

  The present invention provides a method in which a step of eluting a noble metal from an ion exchange resin into an eluent and a step of recovering the noble metal from the eluent can be carried out simply and continuously.

  In the method for recovering a noble metal of the present invention, an eluent composed of an aqueous solution of a thiocyanate compound is brought into contact with an ion exchange resin that has adsorbed the noble metal to elute the noble metal in the eluent, and then the noble metal is removed from the eluent. When recovering by electrolysis, the eluent is continuously circulated between an elution tank in which the eluent is brought into contact with an ion exchange resin, and an electrolytic recovery tank in which the precious metal is electrolyzed from the eluent eluted from the precious metal. Let

  According to the method of the present invention, the eluent can be used any number of times, and noble metals can be electrolytically recovered at a high recovery rate.

  In the method of the present invention, the amount of the eluent is not enormous as in the conventional method, and it becomes possible to recover the noble metal continuously and easily, the processing equipment can be downsized, and the recovery loss of the noble metal can be realized. And a higher recovery rate can be obtained. Thereby, the collection cost can be significantly reduced.

  The method of the present invention is particularly advantageous when the purpose is to separate and recover valuable metals from an ion exchange resin on which precious metals are adsorbed.

  A schematic diagram of a valuable metal recovery system according to the method of the present invention is shown in FIG.

  In the present invention, the noble metal is separated and recovered from the elution tank (2) in which the ion exchange resin (1) and the aqueous solution of the thiocyanate compound as the eluent (3) are contacted, and the eluent (3) containing the noble metal. By providing an electrolytic recovery tank (6) and devising a method for circulating the eluent, an aqueous solution of the thiocyanate compound as the eluent (3) is separated into the elution tank (2) and the electrolytic recovery tank (6). The eluent (3) is circulated by arranging so as to pass sequentially. In addition, there is no restriction | limiting in particular in the property of an ion exchange resin (1).

  The elution tank (2) may be a commercially available column tower for ion exchange resin or a cartridge type container, but may be a container designed to prevent the ion exchange resin (1) from flowing out of the tank.

The aqueous solution of the thiocyanate compound as the eluent (3) is preferably adjusted to a pH of 3 or more and 50 g / liter or more at a normal temperature (25 ° C.). If the pH is less than 3 or less than 50 g / liter, the elution amount of the noble metal is reduced or no elution occurs. The amount of the eluent (3) is 0.3 m ³ , which is recycled.

  The electrolytic recovery tank (6) uses an inexpensive insoluble electrode such as carbon for the anode (4), and the cathode (5) uses an insoluble electrode that is easy to collect, such as stainless steel or titanium, with weak adhesion of electrodeposits. Then, the anode (4) and the cathode (5) are alternately arranged, and a DC power supply such as a general rectifier (8) that is commercially available is used. Furthermore, equipment for removing dust and solid impurities in the ion exchange resin (1) may be disposed before or after the elution tank (2).

The electrolytic current density for separation and recovery is preferably 0.2 A / dm ^{2 to} 5.0 A / dm ² , and only the noble metal is efficiently recovered, so it can be used repeatedly as the eluent (3), and no large amount of waste liquid is generated. .

  In this way, the ion exchange resin (1) that has finished collecting the noble metal can be used again through steps such as washing with water and regeneration.

(Example 1)
By using the recovery system shown in FIG. 1, 14 kg (Au: 17.54 g / kg) of ion exchange resin (1) on which valuable metal of Au: 245.6 g has been adsorbed is dissolved in an elution tank comprising a column tower for ion exchange resin ( 2), and the eluent (3) consisting of 200 g / l aqueous solution of ammonium thiocyanate is maintained at pH 7 in the elution tank (2), electrolytic recovery tank (6) and filtration equipment (not shown). Then, the liquid was circulated through the magnet pump (7) at a circulation rate of 20 liters / minute for 24 hours. As the ion exchange resin (1), a product obtained by adsorbing a noble metal to an ion exchange resin manufactured by Sumitomo Chemical was used.

The electrolytic conditions were a DC power supply (8), the anode (4) was carbon, the cathode (5) was a stainless steel plate, the electrolysis current density was 1.0 A / dm ² , and circulation collection was performed for 24 hours. The amount of Au, the amount of Au in the eluent, the concentration of the eluent, and the amount of recovered (electrodeposition) Au were analyzed, and the Au recovery rate was calculated.

The measurement results are shown in Table 1. As shown in Table 1, Au in the ion exchange resin could be electrodeposited 99.0% on the cathode in 24 hours, the recovery rate was high, and the eluent concentration was hardly decreased. Further, the Au quality of the collected electrodeposits was 99.99% as measured by fluorescent X-ray.

(Comparative Example 1)
The ion exchange resin (1) used in Example 1 (14) (Au: 238.2 g) was used with 1,000 liters of an eluent (3) consisting of an aqueous solution of ammonium thiocyanate 200 g / liter, and the pH was maintained at 7. Then, the solution was passed through the magnet pump (7) at a circulation rate of 20 L / min, then allowed to stand, reduced with a reducing agent, and Au was collected. The amount of Au in the resin, the amount of Au in the eluent, and the amount of precipitated recovered Au were analyzed, and the Au recovery rate was calculated.

The measurement results are shown in Table 2. As described above, compared with Example 1, a large amount of eluent was required, and the Au recovery rate was also lower.

(Example 2)
The apparatus shown in FIG. 1 was used. Ion exchange resin (1) 14 kg (Au: 1.08 g / kg, Ag: 0.18 g / kg) on which valuable metals of Au: 15.12 g and Ag: 2.52 g are adsorbed is used as a column for ion exchange resin. The elution tank (2) consisting of a tower is filled, and the desorption liquid (3) 40 consisting of an aqueous solution of ammonium thiocyanate 200 g / liter is added to the elution tank (2), the electrolytic recovery tank (6) and the filtration equipment (not shown). The liter was maintained at pH 7 and circulated through the magnet pump (7) at a circulation rate of 20 liters / minute. The ion exchange resin (1) and the cathode (5) were changed three times every 24 hours. The eluent (3) was used continuously without being exchanged, but when the eluent concentration was 150 g / liter or less, ammonium thiocyanate was added until the eluent concentration was 250 g / liter.

The electrolytic conditions were a DC power supply (8), the anode (4) was carbon, the cathode (5) was a stainless steel plate, the electrolysis current density was 1.0 A / dm ² , and circulation collection was performed for 24 hours. The amount of Au, the amount of Au in the eluent, the amount of Ag, the recovery (electrodeposition) Au and the amount of Ag were analyzed, and the recovery rate and the total recovery rate were calculated. The measurement results are shown in Table 3.

  The recovery rate increases every time the ion exchange resin is replaced because the eluent is not exchanged. The reason why the recovery rate of Ag exceeds 100% is that elution from the ion exchange resin into the eluent. This is because there was more silver electrodeposited from the eluent to the cathode than Ag.

  As shown in Table 3, high recoveries of Au: 98.7% and Ag: 98.9% were obtained, and the eluent could be used repeatedly.

It is the schematic which shows the collection | recovery system of a noble metal by the method of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ion exchange resin 2 Elution tank 3 Eluent 4 Anode 5 Cathode 6 Electrolytic recovery tank 7 Pump for eluent circulation 8 Rectifier

Claims (1)

In the method for recovering a noble metal, the ion exchange resin adsorbing the noble metal is brought into contact with an eluent comprising an aqueous solution of a thiocyanate compound to elute the noble metal in the eluent, and then the noble metal is recovered from the eluent by electrolysis. The eluent is continuously circulated between an elution tank in which the eluent is brought into contact with an ion exchange resin, and an electrolytic recovery tank that performs electrolytic recovery of the noble metal from the eluate from which the noble metal has been eluted. How to recover precious metals.