A device and method for recovering low-concentration precious metals in cyanide solution

Abstract

The present invention discloses a device and method for recovering low-concentration precious metals in cyanide solution. The device comprises a reaction tank, wherein an anion exchange membrane is arranged in the reaction tank, wherein the anion exchange membrane separates the reaction tank into an anode chamber and a cathode chamber, and an anode and a cathode respectively arranged in the anode chamber and the cathode chamber; the anode is a three-dimensional nanoporous electrode, and the cathode is a three-dimensional noble metal-philic catalytic electrode. The present invention arranges an anion exchange membrane in the reaction tank, so that impurity metal cations are blocked in the anode chamber during the movement of target ions to the cathode, thereby avoiding competitive reduction of impurity metals and target metals, and improving the recovery rate of precious metals; by using a three-dimensional noble metal-philic catalytic electrode and a three-dimensional nanoporous electrode, the effective enrichment of low-concentration precious metal ions at the cathode is accelerated, and low-concentration or even trace amounts of precious metal ions can be efficiently reduced and recovered without an additional enrichment process.

Description

Technical Field

[0001] The invention belongs to the technical field of precious metal recovery, and in particular relates to a device and method for recovering low-concentration precious metals in cyanide solution. Background Art

[0002] Cyanide gold extraction has been widely used in gold extraction production since the end of the 18th century. It can be said that cyanide gold extraction has played a very important role in the gold industry for a century, with relatively low cost and mature technology. Gold concentrate is leached with cyanide to obtain gold cyanide. The concentration of gold cyanide is low and cannot be effectively directly replaced and electrodeposited, so an enrichment process is required. In the latest cyanide gold extraction process, activated carbon is often used to adsorb gold from the cyanide leached ore pulp. This gold extraction process is called "carbon slurry method". The so-called carbon slurry method is to put activated carbon into cyanide ore pulp, adsorb the gold dissolved in it onto the activated carbon, and then desorb the gold from the gold-loaded carbon to obtain a precious gold liquid, and then use the replacement method or electrolysis method to recover gold from the desorbed gold-containing precious liquid, regenerate the desorbed carbon, and remove impurities. The above-mentioned entire "carbon slurry method" process requires three steps of "adsorption-desorption-reduction" to reduce the precious metal deposit to a single substance, and the process steps are relatively complicated.

[0003] The replacement method is to add metal elements to the precious metal leaching solution and use the replacement reaction to precipitate the precious metal. However, due to the serious co-precipitation phenomenon, the replaced gold elements need to be cremated and refined to obtain high-purity gold products. For the electrolysis method, under the condition of external DC power supply, anode and cathode will be formed. Due to the mass transfer effect, Au(CN)2 - It will move to the cathode, where it will be enriched with electrons and reduced to elemental gold. However, the electrolysis method has certain requirements for the concentration of gold complex ions. When the concentration of the gold solution is not too high, it cannot be effectively reduced. When multiple metals coexist, metal cations will compete with precious metals such as gold and silver for reduction, affecting the recovery of low-concentration precious metals.

[0004] Chinese patent CN113621995A proposes a method for recovering precious metals in a short process, in which a porous material is coated on the surface of the plate, and the target metal ions can be enriched on the cathode surface without the need for an "adsorption-desorption" process under the action of an electric field, and the enriched metal ions can be effectively reduced to precious metal elements at the cathode. However, this method is only applicable to high-concentration precious metal leachates, and has poor recovery effects on low-concentration or trace precious metal leachates. In addition, the concentration of impurity metal cations (copper, iron, zinc ions) contained in the actual gold concentrate cyanide leachate is much higher than the target metal ion concentration, and they will compete with the target metal ions for reduction at the cathode, thereby reducing the recovery rate of the target metal. Therefore, it is urgent to provide a short process recovery method that can effectively reduce low-concentration or even trace precious metal ions. Summary of the invention

[0005] In view of the problem that the existing technology cannot effectively recover low-concentration / trace precious metals in a short process, the purpose of the present invention is to provide a device and method for recovering low-concentration precious metals in cyanide solution. The present invention uses membrane separation technology to isolate impure metal cations in the anode chamber, and uses a three-dimensional precious metal-philic catalytic electrode at the cathode, which accelerates the enrichment and reduction of low-concentration precious metals at the cathode and improves the recovery rate of precious metals.

[0006] To achieve the above object, the present invention is implemented through the following technical solutions:

[0007] On the one hand, the present invention provides a device for recovering low-concentration precious metals in cyanide solution, comprising a reaction tank, in which an anion exchange membrane is arranged, the anion exchange membrane separates the reaction tank into an anode chamber and a cathode chamber, and an anode and a cathode are respectively arranged in the anode chamber and the cathode chamber; wherein the anode is a three-dimensional nanoporous electrode, and the cathode is a three-dimensional precious metal-philic catalytic electrode.

[0008] Preferably, the device further comprises a convection disturbance device disposed inside the anode chamber or outside the anode chamber, which accelerates the diffusion of target ions toward the cathode by convection disturbance. The convection disturbance device of the present invention is any device capable of disturbing the solution in the anode chamber, such as a peristaltic pump or a magnetic stirrer.

[0009] Preferably, the preparation method of the three-dimensional noble metal catalytic electrode is as follows: the sulfide material is fully mixed with the conductive material and ethylene glycol, and then diammonium phosphate is added to obtain a mixed solution; after the mixed solution is gelled, it is freeze-dried to obtain a three-dimensional noble metal catalytic electrode.

[0010] Preferably, the conduction band value of the sulfide material is below -0.6V.

[0011] Preferably, the sulfide material is one or more of cadmium sulfide, zinc sulfide and molybdenum sulfide.

[0012] Preferably, the preparation method of the three-dimensional nanoporous electrode is as follows: the nanoporous material is fully mixed with the conductive material and ethylene glycol, and then ammonium dihydrogen phosphate is added to obtain a mixed solution; after the mixed solution is gelled, freeze-dried to obtain a three-dimensional nanoporous electrode.

[0013] Preferably, the nanoporous material is one or more of zeolite, diatomaceous earth and activated carbon.

[0014] On the other hand, the present invention also provides a method for recovering low-concentration precious metals in cyanide solution, which is implemented based on the above-mentioned device and comprises the following steps:

[0015] S1. Pour the cyanide leaching solution containing precious metals into the anode chamber and the electrolyte solution into the cathode chamber;

[0016] S2. Connect the cathode and anode to an external power source;

[0017] S3. Start the convection disturbance device and the power supply, and illuminate the cathode surface with a light source, so that the precious metals in the cyanide leaching solution are deposited on the cathode and recovered.

[0018] Preferably, in step S1, the concentration of precious metals in the cyanide leaching solution is 0.01-5 mg / L.

[0019] Preferably, in step S3, the disturbance flow rate of the solution by the convection disturbance device is 2-10 L / h or 400-800 rpm, the voltage of the power supply is 0.8-1.2 V, and the light source is visible light or ultraviolet light.

[0020] The beneficial effects of the present invention are:

[0021] The present invention provides a device and method for recovering low-concentration precious metals in cyanide solution. By arranging an anion exchange membrane in a reaction tank, impurity metal cations are blocked in an anode chamber during the movement of target ions to the cathode, thereby avoiding competitive reduction between impurity metals and target metals and improving the recovery rate of precious metals. By using a three-dimensional nanoporous electrode, the mass transfer of the solution is accelerated. The three-dimensional precious metal-philic catalytic electrode makes the low-concentration precious metal ions (Au(CN)2 - and / or Ag(CN)2 - ) is easier to effectively enrich at the cathode, and low concentrations or even trace amounts of precious metal ions can be efficiently reduced and recovered without the need for additional enrichment processes. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solution of the embodiment of the present invention, the drawings of the embodiment are briefly introduced below.

[0023] Figure 1 It is a schematic diagram of a device for recovering low-concentration precious metals in cyanide solution according to the present invention;

[0024] Figure 2 It is the effect of electrode on precious metal recovery rate;

[0025] Figure 3 This is a graph showing the effect of convective disturbance on precious metal recovery;

[0026] Figure 4 This is a graph showing the effect of anion exchange membrane on precious metal recovery;

[0027] In the figure, 1, reaction tank; 2, anion exchange membrane; 3, anode chamber; 4, cathode chamber; 5, anode; 6, cathode; 7, convection disturbance device; 8, stabilized DC power supply. DETAILED DESCRIPTION

[0028] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] Example 1

[0030] See also Figure 1 The device for recovering low-concentration precious metals in cyanide solution provided in the first aspect of the embodiment of the present invention comprises an anode chamber 3 and a cathode chamber 4, which are connected through a reaction tank 1, and an anion exchange membrane 2 is arranged in the reaction tank 1. An anode 5 and a cathode 6 are respectively arranged in the anode chamber 3 and the cathode chamber 4, and the anode 5 and the cathode 6 are connected to a regulated DC power supply 8 through a wire; a convection disturbance device 7 is also arranged at the bottom of the anode chamber 3, wherein the anode 5 is a three-dimensional nanoporous electrode, and the cathode 6 is a three-dimensional precious metal-philic catalytic electrode.

[0031] Specifically, the anion exchange membrane of this embodiment is commercially available from Fumasep, model: FAA-3-50.

[0032] Specifically, the preparation method of the cathode three-dimensional noble metal catalytic electrode is as follows: zinc sulfide, conductive carbon black and ethylene glycol are fully stirred and mixed in a ratio of 8g:1g:200ml for 1h, and then 15mL of diammonium dihydrogen phosphate (concentration: 0.67mol / L) is added and stirred for 60s (speed 500rpm) to obtain a mixed solution; after the mixed solution is gelled, it is transferred to a freeze dryer for freeze drying (freeze drying temperature: -50°C) to obtain a three-dimensional noble metal catalytic electrode.

[0033] Specifically, the preparation method of the three-dimensional anode nanoporous electrode is as follows: zeolite (particle size: 200nm) and conductive carbon black and ethylene glycol are fully stirred and mixed in a ratio of 8g:1g:200ml for 1h, and then 15mL of diammonium phosphate (concentration: 0.67mol / L) is added and stirred for 60s (speed 500rpm) to obtain a mixed solution; after the mixed solution is gelled, it is transferred to a freeze dryer for freeze drying (freeze drying temperature: -50°C) to obtain a nanoporous electrode.

[0034] Specifically, the convection disturbance device is a magnetic stirrer purchased from Shanghai Meiyingpu Instrument Manufacturing Co., Ltd., model: H01-1B.

[0035] The method for recovering low-concentration precious metals in cyanide solution provided in the second aspect of the present invention is implemented based on the device of the first aspect, specifically as follows:

[0036] 200 mL of cyanide leaching solution (lean solution, initial gold concentration: 0.036 ppm, initial silver concentration: 1.404 ppm) was poured into the anode chamber 3, and 200 mL of sodium chloride solution was added to the cathode chamber 4. The cathode and anode were connected to the negative electrode and the positive electrode of the stabilized DC power supply 8 respectively through wires, the power supply voltage was adjusted to 1.2 V, a xenon lamp light source (power: 50 W) was used to irradiate the three-dimensional zinc sulfide electrode surface, and the convection disturbance device 7 (rotation speed 500 rpm) and the stabilized DC power supply 8 (voltage 0.8-1.2 V) were turned on to allow the precious metals in the cyanide leaching solution to be deposited on the cathode.

[0037] Example 2

[0038] The same apparatus and method as in Example 1 are used to recover the cyanide leaching solution containing precious metals, except that the initial gold concentration in the cyanide leaching solution is 3.611 ppm, and the initial silver concentration is 6.606 ppm.

[0039] Example 3

[0040] The same apparatus and method as in Example 1 are used to recover the cyanide leaching solution containing precious metals, except that the precious metals in the cyanide leaching solution only contain gold, and the initial gold concentration is 3.768 ppm.

[0041] Comparative Example 1

[0042] The cyanide leaching solution containing precious metals was recovered using a device and method basically the same as in Example 1 (lean solution, initial gold concentration: 0.036 ppm, initial silver concentration: 1.404 ppm); the difference was that the positive and negative electrodes of the electrolysis device were both ordinary smooth titanium plates.

[0043] Comparative Example 2

[0044] The cyanide leaching solution containing precious metals (initial gold concentration: 3.611 ppm, initial silver concentration: 6.606 ppm) was recovered using substantially the same apparatus and method as in Example 2; the difference being that no convection disturbance device was provided in the electrolysis apparatus.

[0045] Comparative Example 3

[0046] The cyanide leaching solution containing precious metals (initial gold concentration is 3.768 ppm) is recovered using a device and method substantially the same as in Example 3; the difference being that no anion exchange membrane is provided in the electrolysis device.

[0047] The recovery effects of precious metals in the examples and comparative examples were evaluated.

[0048] The evaluation method is as follows:

[0049] In the electrolytic recovery process of the embodiment and the comparative example, samples were taken from the solution at 10h and 23h (sampling was taken from the cathode and anode chambers at the same time), and the insoluble solids were filtered out with a filter head. The filtrate was tested by atomic absorption spectroscopy to obtain the gold and silver concentrations in the solution at different time points, and the Au(CN)2 - and Ag(CN)2 - Recovery rate.

[0050] The recovery rate is calculated as follows:

[0051]

[0052] Where: R 金、银 ——Recovery rate of gold cyanide or silver cyanide, %;

[0053] c 阳 ——Concentration of gold cyanide or silver cyanide in the anode chamber solution, mg / L;

[0054] V 阳 ——The volume of the solution in the anode chamber, L;

[0055] c 阴 ——Concentration of gold cyanide or silver cyanide in the cathode chamber solution, mg / L;

[0056] V 阴 ——The volume of the solution in the cathode chamber, L;

[0057] c0——initial concentration of gold cyanide or silver cyanide in the anode chamber solution, mg / L;

[0058] V0——initial volume of the anode chamber solution, L.

[0059] The evaluation results are shown in Table 1 and Figures 2 to 4 shown.

[0060] Table 1 Precious metal recovery rates of the embodiments and comparative examples at different times

[0061]

[0062] It can be seen from Table 1 that the device and method provided by the embodiment of the present invention can significantly improve the recovery rate of low-concentration / trace precious metals. This is because after the power supply is turned on, an electric field is generated between the electrode materials. - The concentration is Au(CN)2 - or Ag(CN)2 - Thousands of times, so in the electric field CN - As mass transfer ions, they are enriched towards the anode under the action of the electric field force; impurity metal cations will migrate towards the cathode. Under the blocking effect of the anion exchange membrane, these cations can only be stored in the anode chamber.- and / or Ag(CN)2 - In the presence of a concentration gradient, the forces generated by adsorption and diffusion will be greater than the electric field force on the precious metal Au(CN)2 - and / or Ag(CN)2 - Therefore, under the action of solution disturbance and Donnan dialysis, Au(CN)2 - and Ag(CN)2 - The anion exchange membrane is enriched in the cathode chamber and combined with metal cations, CN - Separation, then the sulfur atoms on the surface of the noble metal catalytic electrode material will react with Au(CN)2 in the cathode chamber - and Ag(CN)2 - - further enriched on its surface. Under the irradiation of the xenon lamp, the noble metal catalytic material excites electrons and the electric field cathode gives out electrons to the Au(CN)2 on its surface. - 、Ag(CN)2 - Reduce to gold and silver, thereby realizing the recovery of low-concentration precious metals in the cyanide leaching solution.

[0063] Combination Figure 2 Compared with Comparative Example 1, it can be seen that the ordinary smooth titanium plate electrode has no recovery effect on low concentration / trace gold and silver, while the three-dimensional noble metal catalytic electrode can promote the effective enrichment and reduction of target ions at the cathode, and the three-dimensional nanoporous electrode can adsorb CN migrating to the anode. - It also accelerates the mass transfer of the solution, thereby achieving efficient reduction and recovery of low-concentration / trace amounts of gold and silver.

[0064] Combination Figure 3 As can be seen from Comparative Example 2, the introduction of convective disturbance can accelerate the diffusion of target ions toward the cathode, thereby improving the recovery rate and recovery rate of gold and silver.

[0065] Combination Figure 4 As can be seen from Comparative Example 3, the addition of anion exchange membrane can avoid competitive reduction between impurity metal cations and target metals, and significantly improve the recovery rate of low-concentration / trace precious metals.

[0066] It should be noted that the above embodiments all belong to the same inventive concept, and the description of each embodiment has its own focus. For matters that are not described in detail in some embodiments, reference may be made to the description in other embodiments.

[0067] The above-mentioned embodiments only express the implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A device for recovering low-concentration precious metals in cyanide solution, characterized in that: The invention comprises a reaction tank, wherein an anion exchange membrane is arranged in the reaction tank, wherein the anion exchange membrane separates the reaction tank into an anode chamber and a cathode chamber, and an anode and a cathode are arranged in the anode chamber and the cathode chamber respectively; the anode is a three-dimensional nanoporous electrode, and the cathode is a three-dimensional noble metal catalytic electrode; Among them, the preparation method of the three-dimensional noble metal catalytic electrode is as follows: the sulfide material, the conductive material and ethylene glycol are fully mixed, and then diammonium phosphate is added to obtain a mixed solution; after the mixed solution is gelled, it is freeze-dried to obtain a three-dimensional noble metal catalytic electrode; the conduction band value of the sulfide material is lower than -0.6V.

2. The device according to claim 1, characterized in that It also includes a convection disturbance device disposed inside the anode chamber or outside the anode chamber for accelerating the diffusion of target ions in the anode chamber toward the cathode.

3. The device according to claim 1, characterized in that The sulfide material is one or more of cadmium sulfide, zinc sulfide and molybdenum sulfide.

4. The device according to claim 1, characterized in that The preparation method of the three-dimensional nanoporous electrode is as follows: the nanoporous material is fully mixed with the conductive material and ethylene glycol, and then ammonium dihydrogen phosphate is added to obtain a mixed solution; after the mixed solution is gelled, freeze-dried to obtain the three-dimensional nanoporous electrode.

5. The device according to claim 4, characterized in that The nanoporous material is one or more of zeolite, diatomaceous earth and activated carbon.

6. A method for recovering low-concentration precious metals in cyanide solution, characterized in that: The method is implemented based on the device according to any one of claims 1 to 5, comprising the following steps: S1. Pour the cyanide leaching solution containing precious metals into the anode chamber and the electrolyte solution into the cathode chamber; S2. Connect the cathode and anode to an external power source; S3. Start the convection disturbance device and the power supply, and illuminate the cathode surface with a light source, so that the precious metals in the cyanide leaching solution are deposited on the cathode and recovered.

7. The method for recovering low-concentration precious metals in cyanide solution according to claim 6, characterized in that: In step S1, the concentration of precious metals in the cyanide leaching solution is 0.01-5 mg / L.

8. The method for recovering low-concentration precious metals in cyanide solution according to claim 6, characterized in that: In step S3, the disturbance flow rate of the solution by the convection disturbance device is 2-10 L / h or 400-800 rpm, the voltage of the power supply is 0.8-1.2 V, and the light source is visible light or ultraviolet light.

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