JP2013181181A - Method for recovering gold - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable recovering of gold with high quality from a sample including gold used for various parts.SOLUTION: A method for recovering gold from a sample including gold and metal other than gold includes a first separation step of causing the sample to be soluble in an acid mixture to separate an insoluble element therefrom; and a second separation step of causing the insoluble element obtained by the first separation method to be soluble in aqua regia to separate an insoluble element therefrom.

Description

  The present invention relates to a method for recovering gold.

  Gold is widely used for decorative items and electronic parts, but since it is an expensive material, it is industrially impossible to recover gold in a reusable state from processing waste and waste generated during processing and manufacturing. It has become a very important issue.

  In a conventional gold recovery method, gold-plated electronic components are pulverized, sieved, or further baked to recover metal scraps including gold. Next, metal scraps are immersed in aqua regia containing potassium cyanide to dissolve gold. Furthermore, after filtering insoluble residues such as ceramics and glass, the solution containing gold is neutralized and reduced to obtain crude gold. This crude gold is further processed by electrolytic refining and melting to be processed into a gold bullion and collected.

  Patent Document 1 describes a technique for recovering gold from gold-plated electronic components without using aqua regia or cyanide compounds. Specifically, the conductor or base metal interposed between the gold plating and the electronic component is dissolved in a heated acid to remove the gold, and the collected gold is roasted to remove organic matter. A technique is described in which the remaining gold is heated and melted at a high temperature, poured into a mold to obtain crude gold, and then the crude gold is recovered as gold bullion through electrolytic purification and melting.

  Patent Document 2 describes a technique in which low-grade gold is dissolved in an organic solvent containing a halide and a halogen simple substance, and then cooled to precipitate high-grade gold.

  In Patent Document 3, when gold is recovered from a metal substrate coated with gold, the metal substrate is used as an anode, and a fluoride solution is used as an electrolytic solution. A technique for stripping is described. Further, Patent Document 3 describes that since the peeled gold does not dissolve in the fluorinated solution, the gold can be recovered by filtering the post-electrolysis solution after the electrolytic treatment.

Japanese Patent Laid-Open No. 08-013051 Japanese Patent Laid-Open No. 07-003351 Japanese Patent Application Laid-Open No. 07-109594

  By the way, the techniques described in Patent Documents 1 and 3 are techniques for peeling the gold coated or plated on the surface of the substrate, and there are restrictions on the form of gold to be collected, so gold is used in various parts. In view of the recovery of gold from the sample being processed. That is, in the techniques described in Patent Documents 1 and 3, gold exposed on the surface can be peeled off, but recovery of gold not exposed on the surface is not assumed.

  Patent Document 2 describes a technique in which low-grade gold is dissolved and high-grade gold is deposited. However, even though it is high-grade, the embodiment that can be realized specifically is at most an example. 9 is about 45%, and it is unclear whether higher-grade gold can be deposited.

  The present invention has been made in view of the above circumstances, and provides a gold recovery method that enables gold to be recovered in high quality from samples including gold and used for various parts. With the goal.

The present invention is shown in the following (1) to (8).
(1) In a method for recovering gold from a sample containing gold,
A first separation step of dissolving the sample in an acid mixture other than aqua regia and collecting insoluble components;
A second separation step of dissolving the insoluble component obtained in the first separation step in aqua regia and removing the insoluble component.
(2) In the method according to (1),
A method in which the metal other than the gold is used for an electronic component.
(3) In the method according to (1) or (2),
A precipitation step of reducing the dissolved component obtained in the second separation step to deposit gold.
(4) In the method according to any one of (1) to (3),
The method, wherein the acid mixture is a mixed acid of sulfuric acid and nitric acid.
(5) In the method according to any one of (1) to (4),
The method in which the reaction in the first separation step is performed under a temperature of 50 to 100 ° C. and under no pressure.
(6) In the method according to any one of (1) to (5),
The method in which the reaction in the second separation step is performed under a temperature of 50 to 100 ° C. and under no pressure.
(7) In the method according to (3),
A method using sodium nitrite in the reduction treatment in the precipitation step.
(8) In the method according to (7),
In the deposition step, a reducing agent is added while measuring the oxidation-reduction potential, and when the potential is stabilized, the method is allowed to stand for a predetermined time to deposit gold.

  According to the present invention, gold can be collected with high quality from samples containing gold and used for various parts.

It is a flowchart which shows one Embodiment of the collection | recovery method of the gold | metal | money of this invention.

  A basic process flow showing an example of the present invention is shown in FIG. 1, and the present invention will be specifically described below.

  In this embodiment, in a method of recovering gold from a sample containing gold (Au) and a metal other than gold (hereinafter referred to as “gold-containing sample”), the sample is dissolved in an acid mixture (S1), and insoluble components are removed. A first separation step (S2) to be collected and a second separation step (S4) for dissolving the insoluble component obtained in the first separation step in aqua regia (S3) and removing the insoluble component.

  Here, the gold-containing sample includes electronic components such as substrates used in communication devices and electronic devices, components such as chips, connection portions of general printed boards, and the like. A characteristic of these samples is that they contain gold in high quality. Such gold-containing samples also contain metals other than gold, typically copper (Cu), lead (Pb), tin (Sn), nickel (Ni), iron (Fe), for example. , Aluminum (Al), zinc (Zn), chromium (Cr), cobalt (Co), and the like.

Returning to FIG. 1, in step (S1), a mixed acid other than aqua regia is added to the gold-containing sample to dissolve the sample.
Here, as the mixed acid other than aqua regia, there are usually those composed of a mixture of acids, and there is no particular limitation as long as metal components other than gold can be dissolved. And mixed acid obtained by mixing with the above. The ratio of each component of the mixed acid is, for example, in the case of a mixture of sulfuric acid and nitric acid, sulfuric acid: nitric acid (volume ratio) is preferably 1: 1 from the viewpoint of preventing the generation of passive state.
The acid dissolution reaction is preferably carried out under the conditions of a temperature of 50 to 100 ° C., a pressure near atmospheric pressure, and a time of 0.5 to 5 hours.

  In step (S2), insoluble components are collected from the dissolved gold-containing sample obtained in step (S1) by filtration. The filtrate (dissolved component) contains metal components other than gold.

In step (S3), aqua regia is added to the insoluble component collected in step (S2) to dissolve it. “Aqua regia” is a mixed acid of hydrochloric acid: nitric acid in a volume ratio of 3: 1 and dissolves gold.
The acid dissolution reaction is preferably carried out under the conditions of a temperature of 50 to 100 ° C., a pressure near atmospheric pressure, and a time of 0.5 to 5 hours.

  In step (S4), insoluble components are removed by filtration from the lysate obtained in step (S3). Examples of the insoluble component include a resin constituting the base material of the component. Thereby, a leachate containing gold with high purity is obtained.

In step (S5), a reducing agent is added to the leachate containing gold obtained in step (S4), and reduction treatment is performed to precipitate gold. Examples of the reducing agent include sodium sulfite. Further, in step (S6), the reduced post-reaction solution is filtered to recover the deposited gold.
As one aspect of the reduction treatment in step (S5), for example, a reducing agent is added while measuring the oxidation-reduction potential, and from the state of oxidation-reduction potential 700 to 800 mV in the standard state with respect to the silver | silver chloride standard electrode A method of depositing gold by allowing it to stand for a certain period of time, for example, about one hour, after confirming that it has decreased to a state of 300 to 450 mV, for example, from 700 mV to a state of 373 mV, has been confirmed to be stable. .

  Through this process, even when recovering gold from recycled materials that contain a lot of metals other than gold, this recycled material is used to remove metals other than gold and components other than metals before leaching the gold. Even without pretreatment such as crushing and incineration of gold, gold can be taken out with high quality.

  Although one embodiment of the present invention has been described above, various modifications can be made without departing from the object of the present invention.

EXAMPLES The present invention will be specifically described with reference to examples, but the present invention is not limited to these examples.
Example 1
A mixed acid composed of 1500 ml of concentrated sulfuric acid and 1500 ml of concentrated nitric acid is added to 2900 g of a gold-containing sample derived from electronic parts containing 16.9 g of gold, 1500 ml of pure water is further added, and heated at 90 ° C. for 2 hours in a sand bath. did.
The obtained acid-treated solution was No. It filtered with the filter of 3 and the gold containing residue was filtered.
The metal species remaining in the filtrate were examined and found to be metal components other than Au, such as Cu, Pb, Sn, Ni, and Fe.

Aqua regia consisting of 900 ml of concentrated hydrochloric acid and 300 ml of concentrated nitric acid was added to the gold-containing residue, 1000 ml of pure water was further added, and the mixture was heated in a sand bath at 90 ° C. for 2 hours.
The insoluble component of this post-reaction solution was designated as No. It filtered and removed with the filter of No. 3, and obtained the liquid after gold | metal | money leaching.
When the residue on the filtered side was examined, it was confirmed that the resin component was not decomposed with aqua regia.

After leaching gold, sodium sulfite is added to the solution to reduce the redox potential from 700 to 800 mV to 350 to 450 mV. After confirming that the solution is stable, leave it at room temperature. Then, gold reduction treatment was performed.
The total residue obtained was 16.51 g, of which gold was 16.01 g. The gold quality was 97% by mass, confirming that the quality was high.

Claims (8)

In a method for recovering gold from a sample containing gold and a metal other than gold,
A first separation step of dissolving the sample in an acid mixture other than aqua regia and collecting insoluble components;
A second separation step of dissolving the insoluble component obtained in the first separation step in aqua regia and removing the insoluble component. The method of claim 1, wherein
A method in which the metal other than the gold is used for an electronic component. The method according to claim 1 or 2, wherein
A precipitation step of reducing the dissolved component obtained in the second separation step to deposit gold. In the method as described in any one of Claims 1-3,
The method, wherein the acid mixture is a mixed acid of sulfuric acid and nitric acid. In the method as described in any one of Claims 1-4,
The method in which the reaction in the first separation step is performed under a temperature of 50 to 100 ° C. and under no pressure. In the method as described in any one of Claims 1-5,
The method in which the reaction in the second separation step is performed under a temperature of 50 to 100 ° C. and under no pressure. The method of claim 3, wherein
A method using sodium nitrite in the reduction treatment in the precipitation step. The method of claim 7, wherein
In the deposition step, a reducing agent is added while measuring the oxidation-reduction potential, and when the potential is stabilized, the method is allowed to stand for a predetermined time to deposit gold.

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