JP2022042946A - Method for recovering gold - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method that can recover gold with improved safety and reduced cost.

SOLUTION: A method for recovering gold includes the step of recovering gold, with a gold recovery agent, from a gold solution having gold, iodine, a salt of iodine, and a reductant dissolved therein. The gold recovery agent includes at least one selected from the group consisting of cells of microorganisms belonging to Cyanidiales and cell derivatives, and processed products of them, and artifacts simulating them.

SELECTED DRAWING: None

COPYRIGHT: (C)2022,JPO&INPIT

Description

The present invention relates to a method for collecting gold.

Small scale mining is a term used to describe the poor people in developing countries mining valuable minerals individually or in groups. In small-scale gold mining, for example, mercury is added to crushed gold ore to obtain gold amalgam, and then the gold amalgam is heated to vaporize the mercury to obtain the remaining crude gold. (For example, Non-Patent Document 1).

UNEP, 2013, Global Mercury Assistance 2013: Sources, Missions, Releases and Environment Transport. , UNEP Chemicals Branch, Geneva, Switzerland

Small-scale mining of gold using mercury has problems such as adverse effects on the health of workers and environmental pollution by mercury released into the environment. Even if small-scale mining itself is prohibited, it is not effective due to the economic circumstances of workers, and there is a problem that alternative methods will not spread unless they can be implemented at low cost.

In view of the above circumstances, it is an object of the present invention to provide a method for recovering gold more safely and cheaply.

The present invention comprises a step of recovering gold from a gold solution in which gold, iodine, a salt of iodine, and a reducing agent are dissolved by a gold recovery agent, wherein the gold recovery agent is a cell of a microorganism belonging to the order Cyanidiophyceae. It relates to a method for recovering gold, which comprises at least one selected from the group consisting of cell-derived products, processed products thereof, and artificial products imitating them.

Since the method for recovering gold according to the present invention is to recover gold from a gold solution in which gold, iodine, a salt of iodine, and a reducing agent are dissolved, a gold recovery agent containing cells of microorganisms belonging to the order Cyanidium is used. Gold can be collected safely without the need to use materials that are harmful to workers and the environment. Further, in the method for recovering gold according to the present invention, essential materials can be procured at low cost, and the recovery rate of gold is high and the cost for mining can be reduced, so that gold can be recovered at low cost. be able to.

Although it is not clear why the gold recovery method according to the present invention has a high recovery rate, a microorganism belonging to the order Cyanidium is caused by the dissolution of gold, iodine, a salt of iodine, and a reducing agent in a gold solution. The present inventor presumes that this is because gold is dissolved in a form that is easily adsorbed by the gold recovery agent containing the cells and the like. As shown in Examples and Comparative Examples described later, even if a gold recovery agent containing cells of microorganisms belonging to the order Cyanidium is used for a gold solution in which gold, iodine and a salt of iodine are dissolved, gold is used. Recovery rate is extremely low.

In the method for recovering gold, the iodine salt may be at least one selected from a salt of iodine and an alkali metal and a salt of iodine and an alkaline earth metal. As a result, the above-mentioned effect according to the present invention becomes more remarkable.

In the gold recovery method, the iodine content may be 0.01 wt% or more and 12 wt% or less based on the total amount of the gold solution. As a result, the above-mentioned effect according to the present invention becomes more remarkable.

In the gold recovery method, the iodine salt content may be 0.005 wt% or more and 8 wt% or less based on the total amount of the gold solution. As a result, the above-mentioned effect according to the present invention becomes more remarkable.

In the method for recovering gold, the processed product may be a dried product, a pulverized product, or a dry powder of a cell of a microorganism belonging to the order Cyanidiophyceae and a cell-derived product.

In the method for recovering gold, the cell-derived product may be a part of cells of a microorganism belonging to the order Cyanidiophyceae.

In the method for recovering gold, the reducing agent may contain ascorbic acid. As a result, the above-mentioned effect according to the present invention becomes more remarkable.

In the gold recovery method, the content of the reducing agent may be 0.2 w / v% or more and 8 w / v% or less based on the total amount of the gold solution. As a result, the above-mentioned effect according to the present invention becomes more remarkable.

The present invention is also a kit for recovering gold from a gold solution in which gold, iodine and a salt of iodine are dissolved, which comprises at least a gold recovery agent, wherein the gold recovery agent is a microorganism belonging to the order Cyanidiophyceae. Also related to a kit comprising at least one selected from the group consisting of cells and cell-derived products thereof, processed products thereof, and artificial products imitating these cells.

The kit may further contain a reducing agent in addition to the gold recovery agent.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a method for recovering gold more safely and cheaply. The method for recovering gold according to the present invention may become widespread as an alternative method for small-scale mining of gold using mercury, which adversely affects the health of workers, pollutes the environment with mercury released into the environment, and the like. The problem is expected to be solved.

Hereinafter, embodiments for carrying out the present invention will be described in detail. However, the present invention is not limited to the following embodiments.

[Gold collection method]
The method for recovering gold according to the present embodiment includes a step (recovery step) of recovering gold from a gold solution in which gold, iodine, a salt of iodine, and a reducing agent are dissolved, using a gold recovery agent. The gold recovery agent used in the recovery step is at least one selected from the group consisting of cells and cell-derived products of microorganisms belonging to the order Cyanidiophyceae, processed products thereof, and artificial products imitating these (at least one type). Collectively, it also includes "cells of microorganisms belonging to the order Cyanidium").

In the recovery step, gold is recovered from a gold solution in which gold, iodine, a salt of iodine, and a reducing agent are dissolved, using a gold recovery agent. The gold recovery agent according to the present embodiment contains cells of microorganisms belonging to the order Cyanidium. Therefore, since the gold dissolved in the gold solution is adsorbed on the gold recovery agent, the gold can be recovered together with the gold recovery agent.

The gold recovery method according to the present embodiment may further include a step (purification step) of purifying the gold adsorbed on the gold recovery agent after the recovery step.

The purification step can be carried out by applying, for example, a method of refining gold by burning the gold recovery agent on which gold is adsorbed and burning the gold recovery agent. Further, for example, a method of immersing a gold recovery agent on which gold is adsorbed in a metal elution solution to elute gold to purify gold can also be applied. Examples of the metal elution solution include an acidic thiourea solution, a mixed solution containing ammonia and an ammonium salt, an acid solution (for example, hydrochloric acid solution, royal water), an alkaline solution (for example, KOH solution), or a metal chelate solution (for example). , EDTA solution).

In the recovery step, it is important that the gold solution in which gold, iodine, the salt of iodine, and the reducing agent are dissolved is in contact with the gold recovery agent. By further dissolving the reducing agent in a solution in which gold, iodine and a salt of iodine are dissolved, a gold solution in which gold is dissolved in a form that is easily adsorbed by a gold recovery agent containing cells of microorganisms belonging to the order Cyanidium is obtained. Conceivable. Therefore, the order of adding the reducing agent and the gold recovery agent to the solution in which gold, iodine, and the salt of iodine are dissolved is arbitrary. Thus, for example, the gold recovery agent may be added to a gold solution in which a reducing agent is further dissolved in a solution in which a salt of gold, iodine, and iodine is dissolved, or a salt of gold, iodine, and iodine is added. It may be added to the dissolved gold solution together with the reducing agent.

As the solvent of the gold solution, for example, water, a lower alcohol (for example, methanol, ethanol, etc.), an organic solvent such as acetonitrile, or a mixed solvent in which two or three or more of these are mixed can be used. The solvent is preferably a mixed solvent of water and a lower alcohol, and more preferably a mixed solvent of water and ethanol (aqueous ethanol solution) because of its excellent handleability. When an aqueous ethanol solution is used, the concentration of ethanol in the aqueous ethanol solution may be, for example, 50 to 90 vol%, preferably 60 to 80 vol%.

The iodine salt may be any compound that releases iodide ions in a solvent, and examples thereof include a salt of iodine and an alkali metal, and a salt of iodine and an alkaline earth metal. Specific examples of the salt of iodine include lithium iodide, sodium iodide, potassium iodide, magnesium iodide, calcium iodide, barium iodide, rubidium iodide, and cesium iodide. The iodine salt may be used alone or in combination of two or more.

The reducing agent may be an organic reducing agent or an inorganic reducing agent.

Examples of the organic reducing agent include ascorbic acid, sodium ascorbic acid, erythorbic acid (isoascorbic acid), sodium erythorbate, formic acid, oxalic acid, calcium oxalate, sodium oxalate, citric acid and the like. If an optical isomer is present in the organic reducing agent, any optical isomer may be used. Examples of the inorganic reducing agent include thiocyanate, thiosulfate, sodium sulfide, sulfurous acid, sulfite, iron powder and the like.

As the reducing agent, an organic reducing agent is preferable because the effect of the present invention can be exerted more remarkably, ascorbic acid (L-ascorbic acid, D-ascorbic acid and a mixture thereof), sodium ascorbic acid (sodium L-ascorbic acid). , D-sodium ascorbic acid and mixtures thereof) are more preferred. The reducing agent may be used alone or in combination of two or more.

The iodine content may be, for example, 0.01 wt% or more and 12 wt% or less based on the total amount of the gold solution. From the viewpoint of further increasing the recovery rate of gold, the iodine content is preferably 0.1 wt% or more and 6 wt% or less, and 0.3 wt% or more and 3 wt% or less, based on the total amount of the gold solution. It is more preferably 0.5 wt% or more and 1.5 wt% or less.

The content of the iodine salt may be, for example, 0.005 wt% or more and 8 wt% or less based on the total amount of the gold solution. From the viewpoint of further increasing the recovery rate of gold, the iodine salt content is preferably 0.05 wt% or more and 4 wt% or less, and 0.1 wt% or more and 2 wt% or less, based on the total amount of the gold solution. Is more preferable, and 0.2 wt% or more and 1 wt% or less is further preferable.

The content of the reducing agent may be, for example, 0.2 w / v% or more and 8 w / v% or less based on the total amount of the gold solution. From the viewpoint of further increasing the recovery rate of gold, the content of the reducing agent is preferably 0.3 w / v% or more and 6 w / v% or less, preferably 0.4 w / v% or more, based on the total amount of the gold solution. It is more preferably 4 w / v% or less, and further preferably 0.5 w / v% or more and 3 w / v% or less.

The concentration of gold in the gold solution is not particularly limited as long as the gold is dissolved, but is usually 0.00002 w / v% or more and 0.2 w / v% or less based on the total amount of the gold solution. From the viewpoint of further increasing the recovery rate of gold, the concentration of gold in the gold solution is preferably 0.0002 w / v% or more and 0.1 w / v% or less, preferably 0.001 w, based on the total amount of the gold solution. It is more preferably / v% or more and 0.05 w / v% or less.

The gold recovery agent according to the present embodiment contains at least one selected from the group consisting of cells and cell-derived products of microorganisms belonging to the order Cyanidium, processed products thereof, and artificial products imitating them.

Examples of the microorganisms belonging to the order Cyanidios include microorganisms belonging to the genus Galdia, the genus Cyanidium, and the genus Cyanidioschyzon. Among these, microorganisms belonging to the genus Gardieria are preferable, and Galdia sulphuraria is more preferable. Microorganisms belonging to the order Sianidium are characterized in that they can selectively adsorb and recover gold from a metal solution in cells or on the cell surface.

The cells of the microorganism belonging to the order Sianidium may be live cells (proliferable cells) or dead cells (non-proliferable cells).

Further, the microorganism belonging to the order Cyanidium may be a recombinant microorganism that has been genetically modified by a gene recombination technique as long as the above-mentioned characteristics are not lost.

The cell-derived product of the microorganism belonging to the order Cianidium may be a part of the cells of the microorganism belonging to the order Cyanidium. As described above, since microorganisms belonging to the order Cyanidium can selectively adsorb and recover gold from a metal solution in the cell or on the cell surface, the cell-derived product is an intracellular-derived product (for example, a cell). It may be a cytoplasm containing an internal small organ) or a cell surface-derived product (for example, a cell wall or a cell membrane).

The processed product of the cell or cell-derived product of the microorganism belonging to the order Cianidium may be, for example, a dried product, a pulverized product and a dry powder of the cell or cell-derived product of the microorganism belonging to the order Cyanidium.

The dried product can be obtained by subjecting cells of microorganisms belonging to the order Cyanidium or cell-derived products to a drying treatment. The method of the drying treatment is not particularly limited, and for example, a known method such as a spray drying treatment, a freeze drying treatment, a high temperature drying treatment, or a vacuum drying treatment can be used.

The pulverized product can be obtained by subjecting cells or cell-derived substances of microorganisms belonging to the order Cyanidium to a pulverization treatment. The method of the pulverization treatment is not particularly limited, and for example, a known method such as a ball mill treatment can be used.

The dry powder can be obtained by subjecting the cells or cell-derived substances of microorganisms belonging to the order Cyanidium to the above-mentioned drying treatment and then performing the powdering treatment. As a method of pulverization treatment, for example, a method of performing the above-mentioned pulverization treatment on a dried product can be used.

Examples of the cells of microorganisms belonging to the order Sianidium, cell-derived products, or artificial products imitating these processed products include artificial products produced by organic synthesis, 3D printing, etc. imitating these.

The gold recovery agent according to the present embodiment may be used alone or in combination of two or more.

〔kit〕
The invention also relates to a kit for recovering gold. The kit according to the present embodiment is a kit for recovering gold from a gold solution in which gold, iodine, and a salt of iodine are dissolved, and contains at least a gold recovery agent. The kit may further contain a reducing agent in addition to the gold recovery agent. The kit according to this embodiment can be used to dissolve low-purity gold (for example, solid gold such as gold ore) in a solution containing iodine and a salt of iodine, and to recover higher-purity gold. ..

In the kit according to the present embodiment, as the specific embodiment of the reducing agent and / or the gold recovery agent, the specific embodiment of the reducing agent and / or the gold recovery agent in the above-mentioned gold recovery method can be applied. When the kit according to the present embodiment contains a reducing agent and a gold recovery agent, the reducing agent and the gold recovery agent may be separately contained in the kit or mixed (for example, the reducing agent and the gold recovery agent). May be included in the kit (as a mixed powder of).

The kit according to the present embodiment may further include a solution (iodine solution) in which iodine and a salt of iodine are dissolved in the above-mentioned solvent, in addition to the reducing agent and the gold recovery agent. As the iodine solution, for example, commercially available iodine tincture, dilute iodine tincture, or the like may be used.

Hereinafter, the present invention will be described in more detail based on Examples. However, the present invention is not limited to the following examples.

[Example 1]
(Preparation of dry powder of G. sulfuraria)
G. grown to a steady state. Sulfuraria cells were harvested by centrifugation. The collected cells were dried at 80 ° C. for 12 hours, and then pulverized using a mortar and pestle. A dry powder of sulphuraria was obtained.

(Preparation of gold solution)
1 mL of commercially available iodine tincture (6 wt% iodine, 4 wt% potassium iodide, 60-80 vol% ethanol aqueous solution) diluted 2-fold with 70-80 vol% ethanol aqueous solution for 1 mg of gold (Au) Was dropped and stirred to dissolve the gold. 40 mg of a commercially available vitamin C supplement (food additive grade, 100% vitamin C (L-ascorbic acid)) and 4 mL of water were added to this solution and reduced to obtain gold solution 1.

The gold concentration of the gold solution 1 was calculated by measuring the emission intensity at a wavelength of 242.794 nm with an inductively coupled plasma emission spectrophotometer (manufactured by Agilent). A calibration curve prepared by diluting a standard gold solution with an acid solution was used to calculate the gold concentration. As a result, the gold concentration of the gold solution 1 was 185.6 ppm (mg / L). The gold concentration in this example was measured by this procedure.

(Gold recovery test)
20 mg of G.I. Sulfuraria (dry powder) was added and incubated for 30 minutes at room temperature with vortex stirring. Then, the cells were precipitated by centrifugation, and the supernatant (supernatant 1) was collected. The gold concentration of supernatant 1 was 39.4 ppm (mg / L).

(result)
The recovery rate calculated by the following formula was 78.8%.
Recovery rate = [{(gold concentration of gold solution)-(gold concentration of supernatant)} / (gold concentration of gold solution)] × 100 (%)
In addition, G. The amount of gold recovered per 1 g of sulphuraria (dry powder) was 7.3 mg.

[Example 2]
(Preparation of dry powder of G. sulfuraria)
In the same procedure as in Example 1, G. A dry powder of sulphuraria was prepared.

(Preparation of gold solution)
1 mL of commercially available iodine tincture (6 wt% iodine, 4 wt% potassium iodide, 60-80 vol% ethanol aqueous solution) was added dropwise to 1 mg of gold (Au), and the mixture was stirred to dissolve gold. To this solution, 100 mg of reagent grade ascorbic acid (L-ascorbic acid) and 4 mL of water were added and reduced to obtain a gold solution 2. The gold concentration of the gold solution 2 was 202.2 ppm (mg / L).

(Gold recovery test)
Using gold solution 2 instead of gold solution 1, G.M. A gold recovery test was carried out in the same procedure as in Example 1 except that the amount of sulphuraria (dry powder) added was changed to 10 mg, and the gold concentration of the recovered supernatant (supernatant 2) was measured. As a result, the gold concentration of the supernatant 2 was 80.6 ppm (mg / L).

(result)
The recovery rate calculated in the same manner as in Example 1 was 60.1%. In addition, G. The amount of gold recovered per 1 g of sulphuraria (dry powder) was 12.2 mg.

[Example 3-1]
(Preparation of dry powder of G. sulfuraria)
In the same procedure as in Example 1, G. A dry powder of sulphuraria was prepared.

(Preparation of gold solution)
1 mL of commercially available iodine tincture (6 wt% iodine, 4 wt% potassium iodide, 60-80 vol% ethanol aqueous solution) diluted 2-fold with 70-80 vol% ethanol aqueous solution for 1 mg of gold (Au) Was dropped and stirred to dissolve the gold. 40 mg of a commercially available vitamin C supplement (food additive grade, 100% vitamin C (L-ascorbic acid)) and 4 mL of water were added to this solution and reduced to obtain a gold solution 3-1. The gold concentration of the gold solution 3-1 was 198.6 ppm (mg / L).

(Gold recovery test)
20 mg of G.I. Sulfuraria (dry powder) was added and incubated for 30 minutes at room temperature with vortex stirring. The cells were then precipitated by centrifugation and the supernatant (supernatant 3-1) was collected. The gold concentration of the supernatant 3-1 was 26.6 ppm (mg / L).

(result)
The recovery rate calculated in the same manner as in Example 1 was 86.6%. In addition, G. The amount of gold recovered per 1 g of sulphuraria (dry powder) was 8.6 mg.

[Example 3-2]
(Preparation of dry powder of G. sulfuraria)
In the same procedure as in Example 1, G. A dry powder of sulphuraria was prepared.

(Preparation of gold solution)
1 mL of commercially available iodine tincture (6 wt% iodine, 4 wt% potassium iodide, 60-80 vol% ethanol aqueous solution) diluted 2-fold with 70-80 vol% ethanol aqueous solution for 1 mg of gold (Au) Was dropped and stirred to dissolve the gold. 4 mL of water was added to this solution to dilute it to give a gold solution 3-0.

(Gold recovery test)
40 mg of commercially available vitamin C supplement (food additive grade, 100% vitamin C (L-ascorbic acid)) and G. 20 mg of sulphuraria (dry powder) was mixed to prepare premix powder 1.

Premix powder 1 was added to 1 mL of gold solution 3-0 and incubated for 30 minutes at room temperature with vortex stirring. The cells were then precipitated by centrifugation and the supernatant (supernatant 3-2) was collected. The gold concentration of supernatant 3-2 was 32.8 ppm (mg / L).

(result)
The recovery rate calculated in the same manner as in Example 1 from the gold concentration of the gold solution 3-1 (see Example 3-1) and the gold concentration of the supernatant 3-2 was 83.5%. In addition, G. The amount of gold recovered per 1 g of sulphuraria (dry powder) was 8.3 mg.

[Example 3-3]
(Preparation of dry powder of G. sulfuraria)
In the same procedure as in Example 1, G. A dry powder of sulphuraria was prepared.

(Preparation of gold solution)
Gold solution 3-0 was prepared in the same procedure as in Example 3-2.

(Gold recovery test)
Commercially available vitamin C supplements (food additive grade, 100% vitamin C (L-ascorbic acid)) 8 mg and G. 20 mg of sulphuraria (dry powder) was mixed to prepare a premix powder 2.

Premix powder 2 was added to 1 mL of gold solution 3-0 and incubated for 30 minutes at room temperature with vortex stirring. The cells were then precipitated by centrifugation and the supernatant (supernatant 3-3) was collected. The gold concentration of the supernatant 3-3 was 28.5 ppm (mg / L).

(result)
The recovery rate calculated in the same manner as in Example 1 from the gold concentration of the gold solution 3-1 (see Example 3-1) and the gold concentration of the supernatant 3-3 was 85.6%. In addition, G. The amount of gold recovered per 1 g of sulphuraria (dry powder) was 8.5 mg.

In Examples 3-1 and 3-2, the addition of vitamin C to the gold solution was carried out by G.M. It differs in that it is carried out before or at the same time as the addition of the dry powder of sulphuraria. Since there was no significant difference in the recovery rate between the two, it can be seen that the addition timing is arbitrary.

[Comparative Example 1]
(Preparation of dry powder of G. sulfuraria)
In the same procedure as in Example 1, G. A dry powder of sulphuraria was prepared.

(Preparation of gold solution)
1 mL of commercially available iodine tincture (6 wt% iodine, 4 wt% potassium iodide, 60-80 vol% ethanol aqueous solution) was added dropwise to 1 mg of gold (Au), and the mixture was stirred to dissolve gold to obtain gold solution 4. rice field. Vitamin C and water were not added to the gold solution 4. The gold concentration of the gold solution 4 was 910 ppm (mg / L).

(Gold recovery test)
Using gold solution 4 instead of gold solution 1, G.M. A gold recovery test was conducted in the same procedure as in Example 1 except that the amount of sulphuraria (dry powder) added was changed to 10 mg, and the gold concentration of the recovered supernatant (supernatant 4) was measured. As a result, the gold concentration of the supernatant 4 was 950 ppm (mg / L), and no gold was recovered.

The results of each example and comparative example are summarized in Table 1.

Claims (1)

The invention described herein.