Electrolytic collection apparatus of precious metal or rare metal

Abstract

To provide an electrolytic collection apparatus and a collection method for collecting precious metals or rare metals by dissolving precious metals or rare metals in an urban mine or an ore in a manner of no stirring, no liquid adjustment, and short time, using an electrolyzer having a much simpler structure than that of a diaphragm electrolyzer or non-diaphragm electrolyzer.SOLUTION: An electrolytic collection apparatus for collecting precious metals or rare metals comprises an anode unit provided in the central part of a container and a cathode 5 provided in the vicinity of a container body or a container inner wall. The anode unit is composed of an anode material and a water-permeable bag body 4 arranged to encapsulate the bag. In the bag body, crushed precious-metal or rare-metal-containing materials 3 are accommodated. In the container, aqueous salt solution is filled. Hypochlorite ions generated by electrolyzing salt while applying voltage to both electrodes discharge the precious metals or rare metals dissolved as ions out of the bag body, so that the dissolved ions of the metals are deposited on a conducting cathode surface and in the vicinity thereof.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a hydrometallurgical method for dissolving precious metals or rare metals in crushed electronic device circuit boards or ores (hereinafter referred to as the workpiece) using hypochlorite ions generated by electrolysis of an aqueous chloride solution, and simultaneously depositing the metals on or near the surface of a cathode. [Background technology]

[0002] In many cases, precious metals contained in ores form strong solid solutions with iron sulfide, and they cannot be extracted unless this solid solution is destroyed. In the traditional cyanidation method, ore is roasted as a pretreatment to turn it into a porous oxide. During this process, the sulfide is oxidized and sulfurous acid gas is generated. Cyanide compounds are then used to extract the precious metals. These methods cause environmental pollution, and there is a demand for safer refining methods that place less of a burden on the environment.

[0003] A method for refining gold ore that does not use cyanide is known as electrolytic refining, which uses a water-soluble chloride as the electrolyte. This uses a diaphragm-type electrolytic cell or a diaphragm-less electrolytic cell. In the former, the cell is divided into two or more chambers by a diaphragm, filled with an aqueous chloride solution, an insoluble anode is installed in at least one of the chambers, ore powder is added, stirred, dispersed and suspended, and a titanium, stainless steel or iron cathode is installed in the other chamber and electricity is passed through. In the latter, the entire cell is a single chamber, filled with an aqueous chloride solution, ore powder is added, an anode and a cathode are installed, and electricity is passed through while stirring.

[0004] This type of electrolytic refining method is called electrochlorination and was first proposed in the United States at the end of the 19th century. Since then, several technical proposals have been made.

[0005] A method is known in which chlorine obtained by electrolysis of an aqueous solution of an alkali metal chloride is directly reacted electrochemically with the ore to dissolve precious metals (Patent Document 1). The electrolytic cell is divided by a porous asbestos plate, with an anode on one side and a cathode on the other. This is known as a diaphragm electrolytic cell. Ore is placed in the anode chamber, and a positive voltage is applied to the electrode to generate chlorine, which is then vigorously stirred. The asbestos plate acts as a filter, preventing impurities from entering the cathode chamber, and gold is deposited on the cathode.

[0006] There is a method in which a membrane is used in a diaphragm-type electrolytic cell to extract gold from ore as gold chloride. [Patent Document 2]

[0007] There is a technology to extract gold and silver from ores and concentrates using a diaphragm electrolytic cell. A mixture of ore mud (300g / L) and concentrated sodium chloride electrolyte (250g / L) is made, and the liquid temperature is kept just below boiling to dissolve the silver and gold. In this case, the pH is kept within the range of 3.0-8.0 and the ORP is kept within the range of 750-850 mV. Metals are deposited on the cathode. In this method, chlorine is supplied as gas or hypochlorous acid, and the electrode system is used only to deposit metals from the liquid [Patent Document 3].

[0008] The invention that is methodologically closest to the present invention consists of a stage in which powdered raw material is electrolytically treated in a chloride solution, followed by a stage in which precious metals are extracted, both of which are carried out in a single-chamber membrane-free electrolytic cell. In the electrolytic stage, the ground raw material and an aqueous solution with a chloride ion concentration of 60-180 g / L are mixed together to prepare muddy water with a solid:liquid ratio of 1:(1-20), which is then adjusted to a pH of 0.2-1.0 and electrolytic treatment is carried out. In the first stage of the electrolytic stage, the volumetric current density is increased to 1000-10000 A / m while stirring. 3 An electrolytic voltage of 2-5 V was applied and maintained. The end of the electrical treatment of the muddy water was determined when the change in the current value over time exceeded its maximum value and the pH value reached 1-2, and the treatment time was 29 hours.

[0009] After the treatment, the muddy water is sent to the precious metals or rare metals extraction stage. Here, the current density of the cathode of the electrolytic cell is set to 50-200A / m 2The end of the extraction stage is determined when the pH value reaches 3-7. The electrical treatment stage takes 29 hours, the extraction stage takes 149 hours, and both stages take a total of 169 hours [Patent Document 4]. [Prior art documents] [Patent documents] [Patent documents] .

[0010] [Patent Document 1] US 351576,Cassel,26.10.1886(paragraph number 0005) [Patent Document 2] US 3957603, Rhodes, 18.05.1976 (paragraph no. 0006) [Patent Document 3] EP 0115500 A,AVERETT,DEXTEC MATALLURG,15.08.1984(paragraph number 0007) [Patent Document 4] (RU2510669 10.04.2014 BARBOIARE (paragraph number 0009) Summary of the Invention [Problem to be solved by the invention]

[0011] The refining of precious metal ores by electrochlorination does not require roasting of the ores, so there is no generation of sulfur dioxide gas, and it is possible to refine without using cyanide compounds, and it is technically simple. However, the electrochemical dissolution of sulfides and precious metals requires extremely large current densities (several thousand A / m 2 For this reason, the above invention brings the chloride ion concentration of the electrolyte close to that of a saturated aqueous solution, i.e., increases the charge carrier concentration, and obtains a large current by applying a low voltage (several volts). On the other hand, it is possible to increase the current value by increasing the applied voltage, but this increases the power consumption and is economically disadvantageous. Therefore, with the electrolytic cell structure proposed in the above invention, it is extremely difficult to increase the size of the device, as it is hindered by the current value.

[0012] In response to this, the inventors propose an electrolytic device that is composed of an anode unit placed in the center of the container and a cathode placed in the container body or near the container inner wall, as an electrolytic cell structure that maximizes the current density around the anode. In this device, a fabric made of a chemically stable and mechanically strong material, such as a filter cloth or nonwoven fabric, is made into a cylindrical or spherical bag, which simultaneously contains an insoluble anode material and the material to be treated. The insoluble anode material is placed in the center of the ore or urban mine powder, and the aperture is closed to prevent the formation of voids inside the bag, and the lead from the insoluble anode material is brought out through the closed aperture. In this way, the insoluble anode material and the ore powder are unitized.

[0013] The cathode is a hemisphere or cylinder made of titanium, stainless steel, iron, etc., and if it is a thin plate, it can also serve as the main body of the electrolytic cell. Alternatively, if it is a mesh, it is housed in an insulating container made of glass or plastic. The anode unit integrated with the workpiece is placed in the center (optical focus) of the cathode. When the cell is filled with electrolyte and voltage is applied to both electrodes, the current converges on the anode unit integrated with the workpiece, resulting in a large current density and forming an active spot for the electrochemical reaction.

[0014] At the electrochemical reaction spot, sulfides, precious metals, and rare metals are oxidized and dissolved by hypochlorite ions generated by electrolysis of salt water, and are transferred to the electrolyte through the membrane of the anode unit. At this time, the inside of the bag becomes strongly acidic (reaction formula (1)

[0025] ) due to the electrochemical reaction, and the electrolyte outside the bag becomes a strongly alkaline reducing liquid (reaction formula (5)

[0025] ), and the metal ions transferred from the membrane of the bag become hydroxides and precipitate, or are captured by the cathode and deposited.

[0015] The gold contained in the workpiece dissolves as tetrachloridoaurate ions in the bag of the anode unit, and is discharged through the bag membrane cloth into the electrolyte. The tetrachloridoaurate ions are reduced to gold in the reducing electrolyte around the cathode, and are captured by hydroxides of iron and other metals and precipitated. If the electrolyte is adjusted to an acidic state using hydrochloric acid or the like and then electrolysis is performed, the electrolyte does not become alkaline, and therefore the hydroxides of base metals such as iron contained in the workpiece do not precipitate, and gold precipitates on the surface of the cathode. Silver precipitates as silver chloride. Whether or not to adjust the electrolyte's acidity is selected based on the isolation method used for precious or rare metals. [Means for solving the problem]

[0016] The present invention optimizes the shape and arrangement of the electrodes, and by concentrating the current on the workpiece accumulated in a small area, forms an electrochemical reaction spot where the electrochemical reaction becomes extremely active, thereby providing a means for the precious metal or rare metal of the workpiece to be efficiently oxidized and dissolved, and at the same time precipitated on the cathode or in a reduction area near the cathode. Effect of the Invention

[0017] The present invention dissolves precious metals or rare metals in urban mines or ores in a short time without stirring or adjusting the liquid properties, using an electrolytic cell with a simpler structure than diaphragm or non-diaphragm electrolytic cells.

[0018] Since the material to be treated is accommodated in a bag, treatment residues do not become mixed into the electrolyte or the cathode deposit and can be easily separated from the electrolyte. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0020] Test 1 The anode unit was fabricated as follows. A bag 50 mm wide and 100 mm long was made from nonwoven polyester fabric about 0.5 mm thick, 40 g of ore powder (200 mesh) was placed inside it, and a graphite rod (φ6 × 150 L) was inserted into the center of the ore powder layer, with the bottom end of the electrode rod at the center of the layer. The bag with the powder and graphite rod set was then pressed down to prevent any voids from forming, and the top end was tied together with the graphite rod with a cable tie to form a sphere, creating an anode unit (Figure 1.3). The cathode was a round-bottomed stainless steel thin plate vessel with a capacity of 200 mL.

[0021] The test was carried out in the following procedure. The electrolyte is made by dissolving purified salt in water to make a 1.0% aqueous solution, and 150 mL of this solution is placed in the cathode container, and the anode unit is submerged in its optical focus, taking care not to let the anode unit touch the wall of the cathode container and to make sure that its upper end is at the electrolyte level (Figure 1).

[0022] The positive output of a DC power supply (voltage DC19V, current 3.4Amax) was connected to the lead wire of the anode unit, and the negative output was connected to the cathode container, and a voltage was applied and the current value was measured over time.

[0023] The pH of the electrolyte was 6.8 when the voltage application started, and 10.5 when it was stopped. Approximately 10 minutes after the start of the current application, a white amorphous-like precipitate was observed around the anode unit, and after another 10 minutes, a brownish-brown amorphous-like precipitate was observed.

[0024] Qualitative detection of gold during the test was performed by adding ascorbic acid to the sample and observing the color of the resulting gold colloid (Chemical Handbook 2021, p. 72, edited by BP Nikolsky). The end of the electrolytic dissolution reaction of metal sulfides and oxides contained in the minerals was determined when the electrolytic current value exceeded its maximum value (Patent Document 4).

[0025] The reason why the electrolytic current value reaches a maximum value can be explained as follows. Let us consider the case of electrolytic dissolution of gold ore containing iron sulfide (pyrite). Anodic reaction: FeS 2 +8H2 O→Fe 3+ +2SO 4 2- +16H + +15e - (1) 2Cl - →Cl 2 +2e - (2) Au+4Cl - →AuCl 4 - +3e - (3) Cathode reaction: AuCl 4 - +3e - →Au+4Cl - (4) 2H 2 O+2e - →H 2 +2OH - (5) The electrochemical reactions at the anode and cathode are shown above in (1), (2), (3), (4), and (5). The left side of (1), (2), and (3) is before anodization, and the right side is after anodization, while the left side of (4) and (5) is before cathode reduction, and the right side is after cathode reduction. As is clear from the reaction equation, new charge carriers are generated as a result of the anodization reaction in (1), which reduces the internal resistance of the electrolytic cell, and so the current value increases when the voltage is constant.

[0026] As electrolysis progresses and the oxidation dissolution reaction is completed, reaction (2) becomes dominant, the increase in charge carriers stops, the internal resistance of the electrolytic cell increases, and the electrolysis current value decreases (Figure 2). In this test, the volume current density inside the anode unit bag was approximately 83,000 A / m at the peak current value. 3 reached.

[0027] Test 2 The same sample as in Test 1 was used to attempt electrolytic dissolution in a membrane-less electrolytic cell. Electrolytic cell Polyethylene 2.5L container Anode Platinum mesh (plated) Cathode Graphite plate Stirring Magnetic stirrer DC power supply voltage 19V (constant) Current 3.4A(max)

[0028] The test was carried out in the following procedure. Put 2L of 5% sodium chloride solution into a polyethylene container, add 40g of 200 mesh ore powder, stir with a magnetic stirrer, and adjust the rotor speed so that the powder is dispersed throughout without settling. Connect the lead wires from the power supply to the electrodes, apply a voltage, and record the change in current value over time. In Test 2, after the current had been applied, detection of gold in the filtrate using ascorbic acid did not reveal any presence of gold, and the change in current value over time did not reveal any peaks indicating the dissolution of components (Figure 3). However, the current value was increasing, which is thought to indicate that the electrolytic dissolution of ore components was proceeding, albeit very slowly.

[0029] Looking at the change in current value over time in Test 1 and Test 2, gold elution took 35 minutes in Test 1, whereas no elution was observed even after 255 minutes in Test 2. This shows the superiority of the electrolysis device structure according to the present invention, and it can be said that this invention has dramatically improved the efficiency of the hydrometallurgy method (electrochlorination) by electrolysis of urban mines and ores containing gold and rare metals. [Brief description of the drawings]

[0030] [Figure 1] 1 is a diagram illustrating the principle of an electrolysis device according to the present invention. [Diagram 2] 1 is a graph showing the change over time in electrolysis current value in Test 1. [Diagram 3] 1 is a graph showing the change over time in electrolysis current value in Test 2. [Explanation of symbols]

[0031] 1. Anode lead wire. 2. Insoluble anode 3. Urban mine crushed material or ore powder (material to be processed) 4. Bag for containing material to be treated 5. Mesh cathode (if thin, it also serves as the tank body) 6. Electrolyte 7.Electrolyzer body

Claims

1. An electrolytic recovery device for precious metals or rare metals, comprising an anode unit disposed at the center of a container and a cathode disposed near the container body or the container inner wall, The anode unit is composed of an anode material and a water-permeable bag provided to enclose the anode material, The bag contains crushed precious metals or rare metal-containing materials, and the container is filled with a saline solution. By applying a voltage to both electrodes, This electrolytic recovery device for precious metals or rare metals is characterized in that hypochlorite ions produced by electrolysis of salt dissolve precious metals or rare metals and are extracted from the bag as precious metal ions or rare metal ions, and the extracted precious metals or rare metals are deposited on the surface of the cathode or in its vicinity.

2. The container has a spherical, semi-spherical or cylindrical shape; The anode unit is an insoluble material and a bag made of a nonwoven fabric or a filter fabric arranged to enclose the insoluble material, 2. An electrolytic recovery device for precious or rare metals according to claim 1, wherein the cathode is a thin plate or mesh of titanium, stainless steel, iron or the like.

3. The electrolytic recovery device for precious metals or rare metals as described in claim 1 or 2, characterized in that the electrolytic recovery device is a chemical reactor that oxidizes and dissolves materials containing precious metals or rare metals, and an anode unit is placed at the optical focus of the cathode, so that electric current converges thereto to form an electrochemical reaction spot.

4. A method for electrolytically recovering precious metals or rare metals, comprising: an anode unit disposed in the center of a container; and a cathode disposed in the container body or in the vicinity of the container inner wall, the anode unit being constituted by an anode material and a water-permeable bag provided to enclose the anode material; The crushed precious metal or rare metal-containing material is placed in the bag, the container is filled with a saline solution, and a voltage is applied to both electrodes. This electrolytic recovery method for precious metals or rare metals is characterized in that hypochlorite ions produced by electrolysis of salt dissolve precious metals or rare metals, leading to their removal from the bag as precious metal or rare metal ions, and the derived precious metal or rare metal ions are deposited on or in the vicinity of a cathode surface and recovered.

5. 5. The method for electrolytically recovering precious metals or rare metals according to claim 4, wherein the crushed material containing precious metals or rare metals contained in the bag is urban mine or ore powder containing precious metals or rare metals.

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