Noble metal solution production method

Abstract

To provide a method for producing a noble metal solution capable of improving a handling of waste solution.SOLUTION: A method of producing a noble metal solution includes a process of leaching gold into a liquid by supplying an oxidant containing oxygen and ozone and an object containing gold or silver to a liquid containing a cyanide compound as a complexing agent, and in the process, an excess of the oxidant over the amount required to leach the gold or silver is supplied to the liquid.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for producing a precious metal solution. [Background technology]

[0002] Conventionally, complexing agents such as cyanide compounds have been used as leaching agents in the refining, leaching, and recovery of precious metals. As shown in Patent Document 1 below, oxidizing agents such as oxygen and hydrogen peroxide are generally used in the leaching treatment of precious metal solutions. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 01-52456 Summary of the Invention [Problem to be solved by the invention]

[0004] The waste liquid generated in the above-mentioned refining and leaching processes of precious metals has a large environmental impact, and strict detoxification treatment is often required. When the precious metal is gold or silver, the waste liquid may contain a large amount of components such as cyanide compounds that require strict management not only in terms of environmental impact but also in terms of toxic substances. Therefore, since the handling of the waste liquid, such as storage and transportation, is difficult, it is desired to make the handling of the waste liquid easier.

[0005] An object according to one aspect of the present invention is to provide a method for producing a precious metal solution that allows for easy handling of waste liquid. [Means for solving the problem]

[0006] One aspect of the present invention provides a method for producing a precious metal solution as described in the following [1] to [9]. Each embodiment is as follows. [1] A method for producing a liquid containing a cyanide complexing agent, comprising the steps of: supplying an oxidizing agent containing oxygen and ozone, and an object containing gold or silver, to the liquid containing a cyanide complexing agent, thereby leaching the gold into the liquid; A method for producing a precious metal solution, wherein in said step an excess of said oxidant is provided to said liquid over the amount required to leach said gold or said silver. [2] The method for producing a gold solution according to [1], wherein the object is in powder form. [3] The method for producing a precious metal solution described in [1], wherein the object is a foil containing the gold. [4] The method for producing a precious metal solution described in [1], in which, in the above process, the object is used as an anode, a cathode is placed in the liquid, and a partition wall separating the anode and the cathode is placed therein, thereby performing electrolysis. [5] The method for producing a precious metal solution according to any one of [1] to [4], wherein in the step, a ratio of an amount of ozone consumed in association with the leaching of the gold or silver to an amount of ozone consumed in association with a decomposition reaction of the cyanide compound decreases over time. [6] The method for producing a precious metal solution according to any one of [1] to [5], wherein in the step, an average leaching rate of the gold or silver is 20 g / (L·h) or more with respect to the total amount of the liquid. [7] A method for producing a precious metal solution described in any of [1] to [6], wherein a container in which the object and the liquid are contained is provided with an agitator, and a supply section for the oxidizing agent to the container is located directly below the agitator. [8] The method for producing a precious metal solution according to any one of [1] to [7], wherein in the step, the ozone is supplied to the liquid as bubbles. [9] The method for producing a precious metal solution described in [8], wherein in the step, the diameter of the bubbles when supplied to the liquid is greater than 250 μm. Effect of the Invention

[0007] According to one aspect of the present invention, it is possible to provide a method for producing a precious metal solution that allows for easy handling of waste liquid. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram of a manufacturing apparatus for a precious metal solution according to an embodiment. [Diagram 2] FIG. 2(a) is a graph showing the change in the amount of gold leached over time in Experimental Examples 1 and 2, and FIG. 2(b) is a graph showing the change in the amount of gold leached over time in Experimental Examples 2 to 4. [Diagram 3] FIG. 3(a) is a graph showing the change in potassium cyanide concentration over time in Experimental Examples 1 and 2, and FIG. 3(b) is a graph showing the change in potassium cyanide concentration over time in Experimental Examples 2 to 4. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Preferred embodiments of the present invention will be described below with reference to the drawings. Note that the present invention is not limited to these examples, but is indicated by the claims, and is intended to include all modifications within the meaning and scope of the claims. In the following description, the same elements in the description of the drawings are given the same reference numerals, and duplicate descriptions are omitted.

[0010] Fig. 1 is a schematic diagram of a manufacturing apparatus for a precious metal solution according to this embodiment. As shown in Fig. 1, the manufacturing apparatus 100 is an apparatus for manufacturing a precious metal solution by leaching a precious metal, such as gold or silver, from an object containing the precious metal into a liquid (precious metal leaching process). In this embodiment, the manufacturing apparatus 100 is an apparatus for manufacturing a gold solution by leaching gold, which is a type of precious metal, from an object containing the gold into a liquid (gold leaching process). Note that the precious metal in this specification is not limited to gold or silver.

[0011] The object containing a precious metal is a single precious metal or a solid containing a precious metal. The object containing a precious metal may include a recycled raw material. The recycled raw material may be, for example, industrial scrap containing a precious metal-plated portion, an ornament containing a precious metal, a concentrate of a factory waste liquid containing a precious metal, or the like. The recycled raw material may be a high-purity precious metal obtained by pretreating the above-mentioned industrial scrap, ornament, concentrate, or the like. Hereinafter, the precious metal derived from the recycled raw material is also simply referred to as a recycled precious metal. For example, when an object containing gold is used as in the present embodiment, the object is a single gold or a solid containing gold, and may include a recycled raw material. The recycled raw material may be, for example, industrial scrap containing a gold-plated portion, an ornament containing gold, a concentrate of a factory waste liquid containing gold, or the like. Hereinafter, the gold derived from the recycled raw material is also simply referred to as recycled gold. Similarly, the silver derived from the recycled raw material is also simply referred to as recycled silver.

[0012] A part or the whole of the object containing the precious metal dissolves during the production of the precious metal solution. In this embodiment, a part or the whole of the object containing the gold dissolves during the production of the gold solution. The shape of the object containing the precious metal is not particularly limited, but may be, for example, a plate (foil), a rod, or a powder. Alternatively, the object containing the precious metal may be a laminate including a precious metal film and a base material. In this embodiment, the object containing the precious metal is in a powder or granular form from the viewpoint of the leaching rate of the precious metal. The powdery form follows the definition of a so-called powder, but is not limited to this definition. The powdery object may be, for example, a collection of solids having an average particle size in the range of 0.1 μm to 100 μm. From the viewpoint of dispersibility, the average particle size may be 0.1 μm to 10 μm. The granular object is, for example, an object having an average particle size of 300 μm to 2000 μm. The object containing the precious metal may be in a state in which the powder form and other forms are mixed. For example, the object containing a precious metal may contain both powdered precious metal and foil-shaped precious metal. The precious metal solution is a precious metal aqueous solution that is a raw material for a precious metal plating solution. When the precious metal solution is a gold solution, the gold solution contains, for example, an anionic gold complex. For example, the gold solution taken out of the manufacturing apparatus 100 is purified in a post-process to obtain a gold solution from which impurities have been removed, a compound containing gold, and the like. Note that the gold solution and silver solution obtained by one embodiment of the present invention can each have a low concentration of impurities derived from a complexing agent. Therefore, the purification process in the post-process for the gold solution and the silver solution can be simplified.

[0013] The manufacturing apparatus 100 may be a batch type apparatus or a continuous type apparatus. In this embodiment, the manufacturing apparatus 100 includes a reaction tank 1, a thermostatic tank 2, a temperature control unit 3, an oxygen supply unit 4, an ozone generator 5, a bubble generator 6, an ozone concentration meter 7, and an ozone treatment tower 8.

[0014] The reaction tank 1 is a member that leaches the precious metal from an object containing the precious metal into the liquid. For example, an object containing the precious metal, a complexing agent, and an oxidizing agent are supplied to the liquid contained in the reaction tank 1, thereby leaching the precious metal from the object into the liquid. The complexing agent is a chemical for complexing the precious metal, for example, a cyanide compound. The cyanide compound is potassium cyanide, calcium cyanide, sodium cyanide, etc. The oxidizing agent is for oxidizing the precious metal, for example, oxygen, hydrogen peroxide, ozone, etc. From the viewpoint of oxidation performance and performing both the decomposition process of excess cyanide and the leaching process of the precious metal into the liquid described later in the reaction tank 1, the oxidizing agent may contain at least ozone. In this embodiment, the oxidizing agent is a gas containing oxygen and ozone.

[0015] An excess amount of oxidizing agent (particularly, at least an excess amount of ozone) that exceeds the amount required for leaching the precious metal is supplied to the reaction tank 1. This allows both the leaching of the precious metal into the liquid and the decomposition of cyanide, which will be described later, to be completed efficiently. The excess amount of oxidizing agent that exceeds the amount required for leaching the precious metal is, for example, 5 times or more and 1000 times or less of the molar equivalent of the oxidizing agent used for leaching the precious metal, but is not limited thereto. The excess amount of oxidizing agent may be 10 times or more, 20 times or more, 500 times or less, or 100 times or less of the molar equivalent. Alternatively, even after the leaching of the precious metal is completed or almost completed, the supply of the oxidizing agent is maintained for, for example, at least 10 minutes, 30 minutes, or 60 minutes, so that an excess amount of oxidizing agent that exceeds the amount required for leaching the precious metal is supplied to the reaction tank 1. Here, the timing of completion of the precious metal leaching process may be the point at which the increase in the concentration of the precious metal in the solution or the weight loss of the object containing the precious metal reaches within 1.0% per 30 minutes, and the timing of near completion of the leaching process may be the point at which the increase in the concentration or the weight loss reaches within 3.0% per 30 minutes.

[0016] When the precious metal is gold, a cyanide compound is used as the complexing agent, and ozone is used as the oxidizing agent, the leaching of gold into the liquid (i.e., the production of a gold complex) is achieved, for example, by a chemical reaction according to the following chemical formula 1. The chemical reaction is, for example, a three-phase gold complexing reaction carried out in a mixed phase of a solid phase (i.e., gold), a liquid phase (i.e., water in which the complexing agent is dissolved), and a gas phase (i.e., ozone). When oxygen is supplied to the reaction vessel 1 in addition to ozone, or when part of the ozone becomes oxygen in the reaction vessel 1, the chemical reaction shown in the following chemical formula 2 may also occur. Note that when the precious metal is silver, a chemical reaction in which "Au" in the following chemical formulas 1 and 2 is replaced with "Ag" may occur. Chemical formula 1:2Au+4CN - +O3+H2O→2[Au(CN)2] - +O2+2OH - Chemical formula 2:4Au+8CN - +O2+2H2O→4[Au(CN)2] - +4OH -

[0017] Although not all are shown, the reaction vessel 1 includes, for example, a main vessel that contains a liquid, a complexing agent, an object containing a precious metal, etc., a material supplying section that supplies the liquid, the complexing agent, the object containing a precious metal, etc., into the main vessel, an agitator that stirs the liquid in the main vessel, an oxidizing agent supplying section that supplies ozone into the main vessel, a liquid recovery section that feeds back the liquid in the main vessel to the bubble generating device 6, a gas recovery section that recovers the gas discharged outside the main vessel, and a discharge section that discharges the precious metal solution from the main vessel, etc. The reaction vessel 1 may also include a power source, electrodes, etc. for performing electrolysis.

[0018] The material supply unit has, for example, a first portion connected to the foam generating device 6 and supplying a liquid in which a complexing agent is dissolved in advance, and a second portion supplying an object containing a precious metal. The agitator has an agitator that at least agitates the liquid in the main container. As the agitator, for example, a propeller type, a paddle type, or a rotor type may be used, or a turbine type such as a pitched turbine type or a disk turbine type may be used. From the viewpoint of agitating not only the liquid but also the object containing a precious metal, a bladeless agitator that is easy to obtain a lifting effect of the object may be used. From the viewpoint of dispersibility of the oxidizer in the liquid, the oxidizer supply unit may be located directly below the agitator. The oxidizer supply unit may be located directly below the agitator of the agitator. In this embodiment, when the oxidizer supply unit can overlap at least a part of the agitator in a plan view, the oxidizer supply unit is interpreted as being located directly below the agitator. The liquid recovery unit has a portion that supplies the liquid in the main container to the foam generating device 6. The liquid recovered by the liquid recovery section is returned (circulated) to the reaction tank 1 via the material supply section. Thus, the liquid supplied from the material supply section to the reaction tank 1 may contain dissolved precious metals. The liquid recovery section may be provided with a filter or the like that prevents recovery of solids such as objects containing precious metals. The gas recovery section has, for example, a section that supplies the recovered gas to the ozone treatment tower 8. The discharge section may discharge only the precious metal solution, or may discharge substances that are not dissolved in the precious metal solution in addition to the precious metal solution. When the manufacturing apparatus 100 is of a continuous type, the discharge section may have a section that discharges the supernatant liquid of the precious metal solution.

[0019] A liquid containing cyanide is a poisonous substance. Therefore, when cyanide remains in a precious metal solution, it is necessary to detoxify the waste liquid (cyanide liquid) obtained by recovering precious metals from the precious metal solution. As a method for detoxifying the cyanide liquid, decomposition of cyanide using ozone can be mentioned. In this embodiment, in the reaction tank 1, both a leaching process of the precious metal into the liquid and a decomposition process such as a reduction process or detoxification process of the excess cyanide are performed. The method for treating the cyanide liquid (liquid phase) using ozone (gas phase) is performed, for example, by chemical reactions according to the following chemical formulas 3 and 4. For example, when the concentration of cyanide ions in the reaction tank 1 becomes 0.2 mol / L or less, 0.15 mol / L or less, or 0.1 mol / L or less, it can be determined that the decomposition process of the excess cyanide is completed. From the viewpoint of preventing the precipitation of the precious metal, the decomposition process may be performed so that the cyanide ions in the reaction tank 1 become 0.10 times, 0.075 times, or 0.05 times the molar equivalent required for leaching the precious metal. The supply of ozone, stirring, and the like may be set so that the chemical reaction represented by Chemical Formula 1 above takes precedence over the chemical reactions represented by Chemical Formulas 3 and 4 below. Chemical formula 3:CN - +O3→OCN - +O2 Chemical formula 4:2OCN - +3O3+2H + →2CO2+N2+H2O+3O2

[0020] The thermostatic bath 2 is a member that maintains the temperature of the liquid in the reaction tank 1 within a predetermined range. The temperature control unit 3 is a member (heater, chilling unit, etc.) that adjusts the temperature of the liquid (e.g., water) contained in the thermostatic bath 2. In one example, the temperature of the liquid in the reaction tank 1 is maintained at 30° C. or higher or 40° C. or higher and 70° C. or lower or 60° C. or lower by the thermostatic bath 2 and the temperature control unit 3. The manufacturing apparatus 100 includes the thermostatic bath 2 and the temperature control unit 3, but is not limited thereto. A device that maintains the temperature of the liquid in the reaction tank 1 within a predetermined range may be included in the manufacturing apparatus 100 instead of the thermostatic bath 2 and the temperature control unit 3.

[0021] The oxygen supply unit 4 is a member, such as an oxygen cylinder, that supplies oxygen to the ozone generator 5. A flow meter FM that measures the flow rate of oxygen supplied from the oxygen supply unit 4 to the ozone generator 5 is attached to a path (such as a pipe) that connects the oxygen supply unit 4 and the ozone generator 5. The presence of the flow meter FM makes it possible to efficiently replace the oxygen supply unit 4, for example.

[0022] The ozone generator 5 is a device that converts the oxygen supplied from the oxygen supply unit 4 into ozone. The ozone generated by the ozone generator 5 is supplied to the bubble generator 6. In this embodiment, the ozone is also supplied to an ozone concentration meter 7 in addition to the bubble generator 6. This makes it easy to check the concentration of ozone generated by the ozone generator 5.

[0023] The bubble generator 6 is a device that supplies ozone supplied from the ozone generator 5 as bubbles into the liquid recovered from the liquid recovery section. The liquid discharged from the bubble generator 6 is supplied to the reaction tank 1 through the first part of the material supply section. Therefore, the liquid supplied to the reaction tank 1 through the first part contains ozone in the form of bubbles (bubble ozone). Therefore, in this embodiment, at least a part of the ozone exists in the liquid (i.e., in the water) in the reaction tank 1 in the form of bubbles. The bubbles contain at least one of ozone and oxygen. That is, the bubbles 1 may contain both ozone and oxygen. The bubbles may also be called, for example, microbubbles, nanobubbles, etc. The diameter of the bubbles supplied from the bubble generator 6 into the reaction tank 1 corresponds to the bubble diameter when the gas containing ozone is supplied from the ozone generator 5 into the liquid, and is, for example, 0.1 μm to 3000 μm, 1.0 μm to 1000 μm, or 10 μm to 250 μm. In this embodiment, from the viewpoint of prioritizing the chemical reaction shown in the above chemical formula 1 over the chemical reactions shown in the above chemical formulas 3 and 4, the diameter may be larger than 50 μm, larger than 100 μm, or larger than 250 μm. From this viewpoint, bubbles having a diameter of 500 μm or more may be supplied into the reaction tank 1, or bubbles having a diameter of 1000 μm or more may be supplied into the reaction tank 1. On the other hand, when the object containing the precious metal is plate-shaped or the like, the diameter may be 100 μm or less. The diameter may be controlled by a conventionally known method. For example, the diameter of the bubbles may be controlled by providing a foaming filter in the foam introduction section. The diameter can be changed depending on the pore size, material, wettability with liquid, and other characteristics of the foaming filter.

[0024] As described above, in order to prioritize the leaching process of precious metals (three-phase chemical reaction) over the decomposition process of cyanide (two-phase chemical reaction) in the reaction tank 1, it is possible to increase the contact opportunity between the bubbles and the object containing precious metals in the reaction tank 1. Specific examples include appropriately selecting the diameter of the bubbles, the introduction position of the bubbles, and the shape of the object containing precious metals. The smaller the diameter of the bubbles, the greater the contact opportunity of the bubbles supplied to the reaction tank 1 with the object containing precious metals, while the bubbles tend to dissolve easily in the liquid phase immediately after introduction, promoting the decomposition of cyanide. On the other hand, the larger the diameter of the bubbles, the lower the diffusibility of the bubbles in the reaction tank 1, and the lower the leaching rate of gold. For this reason, for example, the diameter of the bubbles in the reaction tank 1 may be adjusted by introducing large bubbles into the reaction tank 1 and breaking up the large bubbles in the reaction tank 1. For example, the bubbles are broken up by a stirrer in the reaction tank 1, an object containing precious metals, or the like. In one example, bubbles having a diameter of 100 μm to 300 μm are introduced into the reaction tank 1, and the bubbles are disintegrated to a diameter of less than 100 μm in the reaction tank 1. By adjusting the diameter of the bubbles as described above, the decomposition process of cyanide becomes less likely to proceed, and the utilization efficiency of the complexing agent for leaching of precious metals can be improved.

[0025] Which of the cyanide decomposition process and the precious metal leaching process is prioritized may be influenced by, for example, the shape of the object containing the precious metal. For this reason, the shape of the object containing the precious metal may be determined in addition to the diameter of the bubbles. Also, from the viewpoint of prioritizing the leaching process of the precious metal and ensuring the reaction rate of the leaching process, the specific surface area of ​​at least one of the object containing the precious metal and the bubbles may be increased. For example, when the diameter of the bubbles is large (for example, when the diameter of the bubbles is 250 μm or more and 3000 μm or less), the object containing the precious metal may have a fine shape such as a powder shape. On the other hand, when the diameter of the ozone is small (for example, when the diameter of the bubbles is 0.1 μm or more and less than 250 μm), the object containing the precious metal may have a coarse shape such as a foil shape or a plate shape. Not limited to the above, as long as the leaching process of gold is prioritized, the diameter of the bubbles may be reduced and the object containing the precious metal may have a fine shape in order to increase the contact opportunity between the bubbles and the object containing the precious metal. The progress of the precious metal leaching process and the cyanide decomposition process can be calculated from the weight change of the object containing the precious metal, the complex concentration in the reaction tank 1, the concentration of the cyanide compound, etc. For example, if the leaching rate of the precious metal in the reaction tank 1 is 20g / (L·h) relative to the total amount of liquid, it can be said that there are many opportunities for the air bubbles to come into contact with the precious metal, and that the leaching process of the precious metal is taking priority. If the leaching rate is 24g / (L·h) or more or 26g / (L·h) or more relative to the total amount of liquid, it can be said that the gold leaching process is taking priority.

[0026] The ozone concentration meter 7 is a device that measures the concentration of ozone generated by the ozone generator 5 and the concentration of ozone in the gas discharged from the reaction tank 1. Depending on the measurement results of the ozone concentration meter 7, adjustments of the ozone generator 5 are made. The ozone treatment tower 8 is a device that treats the ozone discharged from the ozone concentration meter 7.

[0027] Next, a description will be given of an example of a method for producing a gold solution using the production apparatus 100 according to this embodiment. In this example of the production method, a batch method is adopted.

[0028] First, liquid is supplied into the reaction tank 1. At this time, water in which a complexing agent is dissolved in advance is supplied as the liquid into the reaction tank 1, but this is not limited thereto. Ozone is generated by supplying oxygen from the oxygen supply unit 4 to the ozone generator 5. The ozone and the liquid collected from the reaction tank 1 are supplied to the bubble generator 6, and bubbles (oxidizing agent) containing the ozone are supplied to the liquid. Then, the liquid containing the bubbles is supplied into the reaction tank 1. An object containing gold is also supplied into the reaction tank 1. As described above, the complexing agent, the oxidizing agent containing ozone, and the object containing gold are supplied to the liquid, and leaching of gold into the liquid (for example, a chemical reaction according to the above chemical formula 1) is performed. As a result, a gold solution is produced in the reaction tank 1. Here, an excess amount of oxidizing agent (particularly ozone) that exceeds the amount required for leaching of gold is supplied into the reaction tank 1. For example, ozone is supplied into the reaction tank 1 for about 15 to 120 minutes with respect to the expected completion time of the gold leaching process. This completes the leaching of gold. The same is true for precious metals other than gold (e.g., silver), but the ratio of the amount of ozone consumed by the leaching of gold to the amount of ozone consumed by the decomposition reaction of cyanide compounds decreases over time. In addition, mainly after the production of the gold solution, a decomposition process of excess cyanide (e.g., chemical reactions according to the above chemical formulas 3 and 4) is also performed. Therefore, in addition to the production of the gold solution, the decomposition process of excess cyanide may also be performed in the reaction tank 1. The decomposition process of excess cyanide may also be performed outside the reaction tank 1. For example, when gold is always retained in the reaction tank 1, when the supply of objects containing gold and the discharge of the produced gold solution are continuously performed, the gold solution, which is the supernatant liquid discharged from the reaction tank 1, is subjected to the above decomposition process outside the reaction tank 1.

[0029] After the gold solution is produced, it is collected from the reaction vessel 1. If any residue remains in the reaction vessel 1, the residue is discharged so as to be separated from the gold solution. After the above steps, the gold solution is discharged. If a complexing agent is not dissolved in the liquid, a complexing agent is supplied to the reaction vessel 1 in addition to the above objects.

[0030] Gold may be re-recovered as a solid from the recovered gold solution. In one example, a gold cyanide compound is produced that is purified by a known method. For example, the gold cyanide compound is crystallized from the recovered gold solution. Waste liquid generated during purification or the like is treated by an appropriate method. Since the gold solution has a reduced amount of surplus cyanide in advance, the waste liquid can also be treated more efficiently.

[0031] Next, the effects achieved by the method for producing a precious metal solution according to the present embodiment described above will be described.

[0032] According to the method for producing a precious metal solution using the production apparatus 100 of this embodiment, a step of supplying an oxidizing agent containing oxygen and ozone and an object containing gold to a liquid containing a cyanide compound as a complexing agent is carried out, thereby leaching gold into the liquid. When the oxidizing agent contains ozone, the oxidizing power of the oxidizing agent is strong, so that the leaching of gold into the liquid is promoted. In addition, since ozone is easily decomposable, the environmental load caused by the oxidizing agent can be reduced. Here, as shown in the above chemical formulas 3 and 4, when ozone and cyanide coexist, cyanide is decomposed by ozone. However, the present inventors have found that when a cyanide compound, ozone, and an object containing gold are allowed to coexist in a liquid, the leaching of gold into the liquid tends to take precedence over the decomposition of cyanide by ozone. According to this embodiment, the reduction of the complexing agent due to the reaction between the complexing agent and the oxidizing agent, which is a side reaction, can be suppressed. Therefore, according to this embodiment, the utilization efficiency of the cyanide compound is less likely to decrease, and an increase in the total amount of the cyanide compound used can be suppressed. Then, an excess of the oxidizing agent exceeding the amount required for leaching gold is supplied to the reaction vessel 1. As a result, after the gold leaching process is completed, the excess cyanide can also be decomposed in the reaction tank 1. This makes it easier to store, transport, and otherwise handle the waste liquid generated in the further processing of the precious metal solution.

[0033] In this embodiment, the gold-containing object may be in powder form, in which case the gold contained in the object is more likely to chemically react with the complexing agent and the oxidizing agent, thereby improving the efficiency of gold leaching.

[0034] In this embodiment, an oxidizing agent containing ozone is supplied to the liquid as bubbles controlled to a predetermined diameter, which allows the balance of ozone consumption for gold leaching and cyanide decomposition to be controlled.

[0035] In this embodiment, the average gold leaching rate may be 20 g / (L·h) or more relative to the total amount of liquid. In this case, the gold leaching reaction is said to be dominant, and the cyanide compound can be used efficiently.

[0036] In this embodiment, the main vessel in which the gold-containing object and the liquid are stored is provided with an agitator, and the oxidant supply section for the main vessel may be located directly below the agitator. In this case, the oxidant supplied as bubbles is easily disintegrated by the agitator or the like. In addition, the gold-containing object is dispersed in the liquid by the agitator, facilitating contact between the oxidant (particularly ozone) and the gold. This improves the efficiency of gold leaching in the reaction vessel 1.

[0037] In this embodiment, the diameter of the air bubbles when supplied to the liquid may be greater than 250 μm. In this case, the air bubbles are unlikely to dissolve in the liquid phase immediately after being introduced into the liquid, so that the cyanide decomposition reaction is unlikely to occur.

[0038] In this embodiment, the diameter of the bubbles supplied to the liquid may be 250 μm or less, which can improve the leaching rate of gold.

[0039] The above embodiment describes one aspect of the present invention. Therefore, the present invention can be modified as appropriate without being limited to the above embodiment. For example, in the above embodiment, the precious metal solution is produced using the production apparatus shown in FIG. 1, but the present invention is not limited to this.

[0040] In the above embodiment, the object containing a precious metal is in a powder form, but is not limited thereto. The object containing a precious metal may be a foil containing a precious metal, a plate containing a precious metal, a laminate containing a precious metal film and a substrate, or the like.

[0041] In the above embodiment, the precious metal is leached from the liquid by a contact chemical reaction between the complexing agent, the oxidizing agent, and the precious metal, but this is not limited to the above. For example, an object containing the precious metal may be used as an anode, a cathode may be placed in the liquid, and a partition wall separating the anode and the cathode may be placed therein to perform electrolysis. In this case, an insoluble electrode may be used as the cathode, and an ion exchange membrane may be used as the partition wall, which is a member that prevents the precious metal from being re-deposited on the cathode. The shape of the anode may be, for example, a plate shape, a rod shape, or the like.

[0042] In the above embodiment, the manufacturing apparatus includes a foam generating device, but is not limited thereto. For example, the manufacturing apparatus may supply a gas containing ozone generated in an ozone generator to a reaction tank. In this case, a foaming filter or the like may be provided at a supply port to which the gas is supplied in the reaction tank. In addition, the manufacturing apparatus includes an ozone concentration meter and an ozone treatment tower, but is not limited thereto. The ozone concentration meter and the ozone treatment tower may be included in an oxidizer device or the like downstream of the manufacturing apparatus. EXAMPLES

[0043] The present invention will be described in more detail below by way of examples, but the present invention is not limited to these examples.

[0044] (Experimental Example 1) A titanium beaker (Ti beaker) was charged with 3 L of water, potassium cyanide (manufactured by Nippon Soda Co., Ltd., 453 g), and gold (manufactured by Asahi Pretec Co., Ltd., powdered recycled gold, particle size: 2 to 10 μm, purity: 95% or more, 600 g). The gold was processed into powder beforehand and charged into the Ti beaker. In the Ti beaker, the amount of potassium cyanide was 1.14 relative to the molar equivalent of gold. Next, a silent discharge ozone generator (manufactured by Ebara Jitsugyo Co., Ltd., OZSD-3000D) was used to supply gas containing oxygen and ozone into the Ti beaker at a rate of 0.2 L / min (ozone concentration: 0.6 g / hr). At this time, the liquid temperature in the Ti beaker was maintained at 49°C using a thermostatic bath. The gas supplied into the Ti beaker turned into bubbles, and the diameter of the bubbles was 500 μm. Then, while supplying the bubbles into the Ti beaker, the Ti beaker was stirred for 7 hours using a stirrer (IKA Japan KK, propeller-type mechanically controlled stirrer) set at 840 rpm. Here, 800 ml of water was supplied to the Ti beaker within 7 hours, 4 hours after stirring the liquid in the Ti beaker. The gold concentration of the gold solution produced by the above was 171 g / L, the KCN concentration was 6.1 g / L, and the remaining gold was 3.7 g. From the above, 87.0 mass% of the total potassium cyanide was consumed for gold leaching. In addition, of the remaining amount (13.0 mass%), 8.3 mass% was decomposed by ozone, etc., and 4.7 mass% remained in the liquid. The average gold leaching rate was 28 g / (L·hr) based on the amount of liquid charged (total amount of liquid).

[0045] (Experimental Example 2) A gold solution was produced in the same manner as in Experimental Example 1, except that a polypropylene mug was used instead of a Ti beaker, the liquid temperature in the mug was maintained at 50°C, and 800 ml of water was added to the mug after stirring. The gold concentration of the gold solution was 164 g / L, the KCN concentration was 7.8 g / L, and the remaining gold was 13.2 g. From the above, 85.6 mass% of the total potassium cyanide was consumed in gold leaching. Furthermore, of the remaining amount (14.4 mass%), 8.4 mass% was decomposed by ozone, etc., and 6.0 mass% remained in the liquid. The average gold leaching rate was 28 g / (L·hr) based on the amount of liquid charged (total amount of liquid).

[0046] (Experimental Example 3) A gold solution was produced in the same manner as in Experimental Example 1, except that a polypropylene mug was used instead of a Ti beaker, the liquid temperature in the mug was maintained at 52°C, 800 ml of water was supplied to the mug after stirring, and gas was supplied to the mug at 0.3 g / hr. The gold concentration of the gold solution was 173 g / L, the KCN concentration was 5.2 g / L, and the remaining gold was 2.3 g. From the above, 87.2 mass% of the total potassium cyanide was consumed in gold leaching. In addition, of the remaining amount (12.8 mass%), 8.8 mass% was decomposed by ozone, etc., and 4.0 mass% remained in the liquid. The average gold leaching rate was 28 g / (L·hr) based on the amount of liquid charged (total amount of liquid).

[0047] (Experimental Example 4) A gold solution was produced in the same manner as in Experimental Example 1, except that a polypropylene mug was used instead of a Ti beaker, the liquid temperature in the mug was maintained at 50°C, a commercially available disk turbine was used as the agitator and its rotation speed was set to 851 rpm, and water was not supplied after the start of agitation. In Experimental Example 4, the air bubbles were well crushed and finely divided. (Introducing: diameter 500 μm, after crushing: diameter 10 μm or less). On the other hand, the gold remained at the bottom of the mug and was not sufficiently stirred. As a result, gold leaching hardly progressed, and only a certain amount of cyanide decomposition was observed. For this reason, in Experimental Example 4, the production of the gold solution was stopped two hours after the start of agitation.

[0048] Fig. 2(a) is a graph showing the progress of the amount of gold leached over time for Experimental Examples 1 and 2. Fig. 2(b) is a graph showing the progress of the amount of gold leached over time for Experimental Examples 2 to 4. In each of Figs. 2(a) and (b), the horizontal axis represents the stirring time, and the vertical axis represents the amount of gold leached. In Fig. 2(a), graph 11 shows the progress of Experimental Example 1, and graph 12 shows the progress of Experimental Example 2. In Fig. 2(b), graph 13 shows the progress of Experimental Example 3, and graph 14 shows the progress of Experimental Example 4.

[0049] FIG. 3(a) is a graph showing the change in potassium cyanide concentration over time in Experimental Examples 1 and 2. FIG. 3(b) is a graph showing the change in potassium cyanide concentration over time in Experimental Examples 2 to 4. In each of FIG. 3(a) and (b), the horizontal axis indicates the stirring time, and the vertical axis indicates the potassium cyanide concentration. In FIG. 3(a), graph 21 indicates the change in Experimental Example 1, and graph 22 indicates the change in Experimental Example 2. In FIG. 3(b), graph 23 indicates the change in Experimental Example 3, and graph 24 indicates the change in Experimental Example 4.

[0050] As shown in Figures 2(a) and (b), in Experimental Examples 1 to 3, the leaching of gold was almost complete after about 6 hours of stirring. On the other hand, in Experimental Example 4, the leaching of gold was hardly performed. This is presumably mainly because the gold was not stirred in the liquid. Also, as shown in Experimental Example 3, when the gas supply amount was 0.3 g / L or more, no difference was observed in the average leaching rate of gold and the amount of gold leached. In addition, as shown in Figures 3(a) and (b), in Experimental Examples 1 to 4, the concentration of potassium cyanide decreased even after the leaching of gold was almost complete. From the above, it is presumed that when gold is present in the liquid, the leaching of gold takes precedence over the decomposition of cyanide. Also, by continuing to supply gas (ozone) after the leaching of gold is completed, the decomposition of cyanide is achieved.

[0051] (Experimental Example 5) In a polypropylene mug, 3 L of water, potassium cyanide (manufactured by Nippon Soda Co., Ltd., 405 g), powdered gold (manufactured by Asahi Pretec Co., Ltd., powdered recycled gold, particle size: 2 to 10 μm, purity: 95% or more, 600 g), and 1.3 L of water were placed. Then, a silent discharge ozone generator (manufactured by Ebara Jitsugyo Co., Ltd., OZSD-3000D) was used to supply a gas containing oxygen and ozone into the mug at 0.2 L / min (ozone concentration: 0.3 g / hr). At this time, the liquid temperature in the mug was maintained at 51°C using a thermostatic bath. In addition, a PTFE filter with a diameter of φ10 μm was placed at the gas supply port of the mug. Then, while supplying ozone into the mug, the contents in the mug were stirred for 7 hours using a stirrer (manufactured by IKA Japan KK, propeller-type mechanically controlled stirrer) set at 844 rpm. After stirring the liquid, 800 ml of water was added to the mug. The gold concentration of the gold solution produced by the above was 63 g / L, and 219.5 g of gold remained. From the above, 35.8 mass% of the total potassium cyanide was consumed for gold leaching. In addition, of the remaining amount (64.2 mass%), 9.5 mass% was decomposed by ozone, etc., and 54.7 mass% remained in the liquid. The consumption rate of potassium cyanide was 40%, and the average gold leaching rate was 12 g / (L·hr). Here, the diameter of the air bubbles supplied to the mug in Experiment 5 exceeded 3000 μm. In Experiment 5, the air bubbles were crushed to a certain extent after introduction, but the contact opportunity between the air bubbles and the gold was insufficient, so the gold leaching rate was slow and the decomposition of cyanide was preferentially performed.

[0052] (Effect of the presence or absence of ozone on oxidizing agents) Potassium cyanide (manufactured by Nippon Soda Co., Ltd., 30 g) and gold (manufactured by Asahi Pretec Co., Ltd., powdered recycled gold, particle size: 2-10 μm, purity: 95% or more, 78 g) were placed in 300 ml of water in a Ti beaker (500 ml). Next, a mixed gas consisting of oxygen and ozone, which are oxidizing agents, was supplied into the beaker using a silent discharge ozone generator (manufactured by Ebara Jitsugyo Co., Ltd., OZSD-3000D) under the conditions of a flow rate of 0.2 L / min and an ozone introduction rate of 0.6 g / h. At this time, the diameter of the bubbles when the gas was introduced into the liquid was 1000 μm or more and 1500 μm or less. In addition, the liquid in the beaker was stirred while maintaining the temperature at 42-45°C using a hot stirrer (manufactured by IKA Japan KK, "C-MAG HS7"). Gold leaching continued, and the average gold leaching rate after 4 hours was 29.6 g / (L h). On the other hand, when the same conditions as above were used except that ozone was not used as an oxidizing agent and oxygen gas was supplied to the beaker at a flow rate of 0.2 ml / min, the average gold leaching rate was 9.7 g / (L h) relative to the amount of liquid charged (total amount of liquid).

[0053] (Gold leaching capacity per oxidizer) Here, in order to minimize fluctuations in the elution conditions due to changes in the surface area of ​​gold, etc., a gold plate measuring 15 cm x 10 cm was prepared as a sample for elution. Next, the sample was immersed in a sodium cyanide solution (10 L, pH: 11, sodium cyanide dosage: 7.6 g / L) adjusted to 27°C to 37°C. At this time, the immersed surface of the gold plate was 10 cm x 10 cm (exposed area: 200 cm). 2), the gold plate was masked with tape so that the area of ​​the gold plate was 100 μm. Then, mixed gas, oxygen gas, air, or hydrogen peroxide solution was supplied as an oxidant to the sodium cyanide solution. The mixed gas was obtained by supplying oxygen gas (flow rate: 1.0 L / min) to an ozone generator. When the oxidant was mixed gas, oxygen gas, or air (oxygen concentration: 21%), the oxidant was converted into microbubbles using a microbubble generator (Kansai Automated Instruments Co., Ltd., MBLL-102-S) and supplied to the sodium cyanide solution for 4 hours using a circulation system. When the oxidant was mixed gas, the ozone input concentration was 108 g / m 3 The oxidant was adjusted to a concentration of 40 mmol / L and the liquid flow rate was 11 L / min. When the oxidant was oxygen gas or air, the oxidant input concentration was 1.0 L / min and the liquid flow rate was 11 L / min. When the oxidant was hydrogen peroxide water, the oxidant concentration was adjusted to 40 mmol / L and the oxidant was first fed to the sodium cyanide solution at once. The concentration of hydrogen peroxide water was adjusted to 80 g / m3 based on the concentration of ozone. 3 is equivalent to.

[0054] The gold leaching rate was evaluated based on the amount of reduction in the thickness direction of the sample. When the oxidizing agent was a mixed gas, the gold leaching rate was 5.1 μm / h. When the oxidizing agent was oxygen gas, the gold leaching rate was 0.8 μm / h. When the oxidizing agent was air, the gold leaching rate was 0.9 μm / h. When the oxidizing agent was hydrogen peroxide, the gold leaching rate was 1.6 μm / h. From the above, it can be said that the gold leaching rate is higher when a mixed gas containing ozone is used as the oxidizing agent than when oxygen gas, air, or hydrogen peroxide is used as the oxidizing agent. Therefore, when a mixed gas is used as the oxidizing agent, productivity can be improved even if a cyanide decomposition process is performed in addition to gold leaching.

[0055] (Effect of gold shape) The elution behavior of the gold samples A to D shown below was compared through the experiment described below. In this comparison, in order to compare the elution rates, the reaction was observed not at the time when the gold elution was completed, but until the gold concentration in the solution reached a predetermined level. All of the gold samples A to D were made from the same raw material. Gold sample A: Shape: Granules, Particle size: 500μm~2000μm, 10g Gold sample B: Shape: powder, particle size: 2μm~10μm, 10g Gold sample C: Shape: foil (gold foil and SUS plate laminate), total thickness: 0.3 mm, 15 cm x 10 cm, 20 sheets Gold sample D: Shape: plate, 15cm x 10cm, immersion surface: 10cm x 10cm (exposed area: 200cm 2 ), Thickness: 0.72mm

[0056] [Experimental conditions] A stirrer and a glass diffuser were placed in a 1L beaker and placed on a hot stirrer. The diffuser was connected to an ozone introduction tube from the top of the beaker and was held at a height such that ozone bubbles could reach the bottom of the beaker. Next, 0.8L of water, 7.6g / L of sodium cyanide, and one of the gold samples A to D were poured into the beaker. The entire amount of gold samples A and B was poured into the beaker. Gold samples C and D were immersed in the liquid while hanging. Bubbles containing ozone (diameter: approximately 1000μm) were introduced into the beaker with an ozone input concentration of 0.89g / h, and immersion of the gold was started. At this time, the liquid in the beaker was stirred at a constant speed using a stirrer, and the temperature of the liquid was maintained between room temperature and 37℃.

[0057] Gold sample A accumulated at the bottom of the beaker and barely moved. The gold concentration in the liquid was 7.3 g / L 2 hours after the start of the immersion, 7.5 g / L after 4 hours, and 7.7 g / L after 6 hours. Even after 6 hours, gold sample A had not completely dissolved. From the above, when gold sample A was used, the gold concentration in the liquid gradually increased over time, but reached equilibrium in approximately 2 hours. Below, the time it took for the gold concentration in the liquid to reach 7.3 g / L was measured for each of gold samples B to D.

[0058] After the gold immersion began, gold sample B was rolled up to the top of the liquid. In addition, the air bubbles introduced into the liquid were broken down by contact with gold sample B, and as a result, the diameter of the air bubbles in the liquid became 50 μm or less. When gold sample B was used, the gold concentration in the liquid reached 7.3 g / L before 1 hour had passed since the start of the gold immersion. On the other hand, when either gold sample C or D was used, the gold concentration in the liquid did not reach 7.3 g / L even 10 hours had passed since the start of the gold immersion.

[0059] From the comparison results of gold samples A to D, when the gold was in powder form, the bubbles introduced into the liquid were finely broken down by the shear force of the rolled up gold itself, and the gold leaching reaction tended to proceed preferentially. On the other hand, when the gold was in the form of a foil or plate, the gold leaching did not proceed sufficiently to reach substantial concentration equilibrium. This is presumably because the cyanide decomposition reaction took precedence over the gold leaching reaction, and as a result, the cyanide was consumed earlier than the gold concentration equilibrium was reached. In addition, when the gold was in granular form (i.e., when the gold particle size was excessively large), the gold leaching rate tended to decrease significantly over time. This tendency is presumably due in part to the fact that the gold was not rolled up, and the cyanide decomposition proceeded preferentially. From the above, when gold in a form different from powdered gold is used, it is possible that the reaction rate can be further improved by making the ozone bubble diameter smaller from the time of introduction, or by using electrolytic treatment with gold as the anode in combination. [Explanation of symbols]

[0060] 1... reaction tank, 2... thermostatic chamber, 3... temperature control unit, 4... oxygen supply unit, 5... ozone generator, 6... bubble generator, 7... ozone concentration meter, 8... ozone treatment tower, 11-14, 21-24... graphs, 100... manufacturing equipment.

Claims

1. The method comprises the step of supplying an oxidizing agent containing oxygen and ozone, and an object containing gold or silver, to a liquid containing a cyanide compound as a complexing agent, thereby leaching the gold into the liquid; A method for producing a precious metal solution, wherein in said step an excess of said oxidant is provided to said liquid over the amount required to leach said gold or said silver.

2. The method for producing a precious metal solution according to claim 1 , wherein the object is in a powder form.

3. The method for producing a precious metal solution according to claim 1 , wherein the object is a foil containing the gold.

4. 2. The method for producing a precious metal solution according to claim 1, wherein in the step, electrolysis is performed by accommodating the object as an anode, a cathode with respect to the liquid, and a partition wall separating the anode and the cathode.

5. 5. The method for producing a precious metal solution according to claim 1, wherein in the step, a ratio of an amount of ozone consumed in association with the leaching of the gold or silver to an amount of ozone consumed in association with a decomposition reaction of the cyanide compound decreases over time.

6. 5. The method for producing a precious metal solution according to claim 1, wherein in the step, an average leaching rate of the gold or silver is 20 g / (L·h) or more with respect to a total amount of the liquid.

7. a container in which the object and the liquid are contained is provided with an agitator; The method for producing a precious metal solution according to any one of claims 1 to 4, wherein a supply section for the oxidizing agent to the container is located immediately below the stirrer.

8. The method for producing a precious metal solution according to claim 7 , wherein in the step, the oxidizing agent is supplied to the liquid as gas bubbles.

9. The method for producing a precious metal solution according to claim 8 , wherein in the step, the diameter of the bubbles when supplied to the liquid is greater than 250 μm.

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