Electrochemical separation and recovery method for multiple metals

Abstract

The invention discloses an electrochemical separation and recovery method for multiple metals. The method comprises the following steps: providing an electrolytic bath with a cation exchange membrane; the electrolytic cell is divided into a cathode chamber and an anode chamber by the cation exchange membrane; providing a cathode and an anode; preparing an electrolyte solution; placing a multi-metal-containing thiosulfate leachate, a chlorate and an anode in the anode chamber, and placing the electrolyte solution and a cathode in the cathode chamber; and voltage is applied to the cathode and the anode, and after the reaction is completed, base metal deposited on the cathode and precious metal deposited on the anode are recycled respectively. The electrolysis device provided with the cation exchange membrane is adopted, precious metal complex ions and other metal ions are separated and stored in different electrolysis chambers under the action of an electric field, precious metal is recycled at the anode and other metal is recycled at the cathode by further combining chemical and electrochemical actions, and the separation and purification process of the metal recycling process can be shortened.

Description

Technical Field

[0001] The present invention belongs to the technical field of hydrometallurgy, and particularly relates to a method for electrochemically separating and recovering multi-metals. Background Art

[0002] With the exhaustion of world natural resources, metal shortage has become an imminent problem, which requires more efficient metal extraction and recovery technologies. At present, hydrometallurgical technologies such as leaching, precipitation, and electrodeposition have become industrial methods for metal refining. Especially for electrodeposition, sodium metal was first obtained by electrolyzing molten sodium hydroxide in 1807, and now it has become the dominant technology for recovering elemental metals from solutions. The separation and purification of metals are either through leaching-electrodeposition to purify from the metal anodes of pyrometallurgy (such as Cu, Ni, Pb, Sn, etc.), or through electrodeposition of hydrometallurgical leaching solutions (such as Cu, Au, Ag, Zn, etc.), and all involve the electrodeposition process.

[0003] The electrodeposition process has high requirements for solution concentration. Usually, the leaching solution needs to be concentrated. For example, the solution concentration for copper electrodeposition is usually 20 - 50 g / L, and the nickel concentration is usually 90 - 140 g / L. When electrodepositing in dilute metal solutions, affected by mass transfer hindrance, the electrodeposition efficiency will be greatly reduced. For example, for precious metal leaching solutions, their concentrations are very low. Usually, adsorbents such as activated carbon and resins are required for multiple adsorption and concentration, and then after desorption, a high-concentration precious solution is obtained to extract precious metals through electrodeposition. However, as the concentration of precious metals in the solution continues to decrease, when it drops to a certain level, the problem of electrodeposition will appear again, and at this time, the reaction solution needs to be concentrated again or multiple times, and the treatment process is relatively complex. In addition, due to the coexistence of precious metals and other base metal ions in the solution, the working voltage used in industrial electrodeposition is relatively large (>3V), and multi-metal co-deposition is inevitable on the cathode, which increases the subsequent separation and purification process.

[0004] In response to the problems existing in the above electrodeposition, research scholars have also carried out targeted research. When the concentration of the leaching solution is low, the recovery efficiency can be improved by adjusting equipment parameters, such as increasing the working voltage / current density, increasing the number of working electrodes, and accelerating the solution flow, but the optimization ability is still limited, and there are still residual precious metal ions in the solution (concentration <mg / L or <μg / L). Regarding the problem of co-deposition of base metals such as copper in the leaching solution, some scholars have proposed to selectively deposit precious metals by controlling the potential according to the different reduction potentials of metal ions, such as Au(S 2 O 3 ) 2 3- / Au (0.153V), Ag(S 2 O 3 ) 23- / Ag (0.01V) and Mn 2+ / Mn (-1.185V), Cr 3+ / Cr (-0.744V) and other reduction potentials are quite different, which can avoid the deposition of manganese and chromium and obtain high-grade precious metals by reducing the working potential, but it is different from Cu 2+ / Cu (0.342V),Fe 3+ / Fe (-0.037V), Pb 2 + / Pb (-0.126V) and so on, and even some base metal ions will precipitate better than precious metals. It can be seen that the actual operation by controlling the potential is difficult.

[0005] Therefore, it is of great significance to develop an electrochemical separation and recovery method for multi-metals. Summary of the invention

[0006] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a method for electrochemical separation and recovery of multiple metals to solve the problems that precious metals and base metals cannot be effectively separated in traditional electrodeposition processes, the purification process is long, and the grade of precious metals is low.

[0007] To achieve the above object, the present invention is implemented through the following technical solutions: The present invention provides a method for electrochemical separation and recovery of multiple metals, comprising the following steps: Providing an electrolytic cell having a cation exchange membrane; the cation exchange membrane separates the electrolytic cell into a cathode chamber and an anode chamber; providing a cathode and an anode; preparing electrolyte solution; placing a polymetallic thiosulfate leachate, a chloride salt and an anode in an anode chamber, and placing an electrolyte solution and a cathode in a cathode chamber; Voltage is applied to the cathode and anode, and after the reaction is completed, the base metal deposited on the cathode and the precious metal deposited on the anode are recovered separately.

[0008] Preferably, both the cathode and the anode are electrode plates coated with an adsorption material layer.

[0009] Preferably, the adsorption material includes one or more of activated carbon, graphite, graphene, graphene oxide, molybdenum disulfide, and cadmium sulfide.

[0010] Preferably, the electrode plate is one of a stainless steel plate, a titanium plate, a graphite felt, a carbon felt, a carbon paper, and a carbon cloth.

[0011] Preferably, the concentration of the electrolyte solution is 0.1-0.5 mol / L, and the pH is 3-10.

[0012] Preferably, the electrolyte solution is one or more of sodium chloride solution, potassium chloride solution, ammonium chloride solution, sodium sulfate solution, potassium sulfate solution, and ammonium sulfate solution.

[0013] Preferably, the concentration of thiosulfate in the polymetallic thiosulfate leachate is 0.1-0.5 mol / L, the concentration of precious metals is 2-100 mg / L, and the concentration of base metals is 50-2000 mg / L.

[0014] Preferably, the ratio of the polymetallic thiosulfate leaching solution to the chloride salt is 150 mL: (0.01-0.5) mol / L. The chloride salt includes one or more of sodium chloride, potassium chloride and ammonium chloride.

[0015] Preferably, the voltage applied to the cathode and the anode is 1.4-4.0V.

[0016] Preferably, the precious metal includes gold and / or silver; the base metal includes one or more of copper, iron, lead, manganese and chromium.

[0017] The beneficial effects of the present invention are: The present invention adopts an electrolysis device equipped with a cation exchange membrane to separate the noble metal complex ions from other base metal ions under the action of an electric field and store them in different electrolysis chambers, and further combines chemical and electrochemical effects to recover the noble metals at the anode and other metals at the cathode, thereby shortening the separation and purification process of the metal recovery process.

[0018] In the present invention, the recovery rate of precious metals at the anode reaches 78.8%, and the purity of precious metals reaches 92.6%, which is much higher than the purity of precious metals of only 0.9% in the traditional electrodeposition process; at the same time, the recovery rate of other metals (such as base metals such as copper) at the cathode is 77.2%, and the metal purity is 100%. The present invention can not only simplify the precious metal recovery process and realize the one-step efficient recovery of multiple metals, but also improve the recovery purity of each metal and promote the green, efficient and high-quality extraction of metals. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a gold recovery effect diagram in Example 1, Comparative Example 1 and Comparative Example 2; Figure 2 1 is a diagram showing the recovery effect of copper in Example 1 and Comparative Example 1; Figure 3 This is the SEM-EDS characterization image of the electrode material after the reaction in Example 1; Figure 4 This is a SEM-EDS characterization image of the electrode surface deposit after the reaction in Comparative Example 2; Figure 5 is a diagram showing the recovery effect of precious metals and base metals in Example 2; Figure 6This is the SEM-EDS characterization picture of the electrode material after the reaction in Example 2 is completed. DETAILED DESCRIPTION

[0020] 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.

[0021] The present invention provides a method for electrochemical separation and recovery of multiple metals, comprising the following steps: (1) An electrolytic cell having a cation exchange membrane is provided; the cation exchange membrane separates the electrolytic cell into a cathode chamber and an anode chamber.

[0022] (2) Grind and mix 20-100 mg of adsorption material (including but not limited to activated carbon, graphite, graphene, graphene oxide, molybdenum disulfide, cadmium sulfide), 1-10 mg of conductive material (conductive carbon black, acetylene black, etc.) and 0.3-0.6 mL of binder (prepared by dissolving 0.1 g of vinylidene fluoride in 8 mL of NN-dimethylacetamide organic solvent) thoroughly, and evenly coat them on a conductive carrier (including but not limited to stainless steel plate, titanium plate, graphite felt, carbon felt, carbon paper, carbon cloth), and obtain the cathode and anode after drying.

[0023] (3) Weigh an inorganic salt (one or more of sodium chloride, potassium chloride, ammonium chloride, sodium sulfate, potassium sulfate, and ammonium sulfate) and dissolve it in pure water to prepare an electrolyte solution with a concentration of 0.1-0.5 mol / L, and adjust the solution pH to 3-10 with saturated sodium hydroxide or hydrochloric acid.

[0024] (4) Mix the polymetallic thiosulfate leachate and chloride salt at 150 mL: (0.01-0.5) mol / L and place them in the anode chamber, and place the electrolyte solution and cathode in the cathode chamber. The concentration of thiosulfate in the polymetallic thiosulfate leachate is 0.1-0.5 mol / L, the concentration of precious metals is 2-100 mg / L, the concentration of base metals is 50-2000 mg / L, and the chloride salt includes one or more of sodium chloride, potassium chloride, and ammonium chloride; then apply a voltage of 1.4-4.0 V to the cathode and the anode, and after the reaction is completed, recover the base metals deposited on the cathode and the precious metals deposited on the anode.

[0025] The principle of the present invention to realize the reduction of precious metals at the anode and the reduction of other metals at the cathode is as follows: driven by the electric field and the concentration difference, other metal cations such as base metals (such as copper ions) and their complexes (such as copper ammine complex ions) in the leachate pass through the cation exchange membrane to leave the anode chamber, reducing the interference of high-concentration metal cations in the anode chamber with low-concentration precious metal thiosulfate coordination ions; at the same time, after the metal cations pass through the cation exchange membrane to reach the cathode chamber, they are captured by the cathode and obtain electrons from the cathode to undergo a reduction reaction, thereby realizing the recovery of other metals at the cathode. Since the precious metal coordination ions are negatively charged and are retained in the anode chamber by the cation exchange membrane, a chloride ion adsorption layer is formed on the anode by the added chloride salt, and the thiosulfate ions are continuously consumed to induce the precious metal coordination ions to undergo a disproportionation reaction, thereby realizing the recovery of the precious metals on the anode in the form of a single substance.

[0026] The present invention is described in detail below with reference to specific embodiments.

[0027] Example 1 (1) Leaching of precious metals: Dissolve copper sulfate pentahydrate in pure water, add 3% mass concentration ammonia water and stir for 20 min, then add ammonium thiosulfate to dissolve and prepare a solution, then add 20 mg of gold powder at a liquid-to-solid ratio of 40:1, stir and leach for 5 h at room temperature, filter after leaching to obtain 150 mL of precious metal leachate, wherein the concentration of thiosulfate in the precious metal leachate is 0.1 mol / L, the concentration of precious metal gold is 18 mg / L, and the concentration of base metal copper is 302 mg / L.

[0028] (2) Electrode preparation: 40 mg of activated carbon, 5 mg of conductive carbon black and 0.4 mL of binder (prepared by dissolving 0.1 g of vinylidene fluoride in 8 mL of NN-dimethylacetamide organic solvent) were thoroughly ground and mixed, and evenly coated on a titanium plate. The plate was placed in a 60°C oven for drying, and then taken out and soaked in pure water for 8 h to remove any loose materials. The plate was then dried again to obtain a coated electrode for use.

[0029] (3) Preparation of electrolyte: Weigh 2.236 g potassium chloride and dissolve it in 149 mL pure water to prepare 150 mL of 0.2 mol / L electrolyte, and adjust the solution pH to 7 with saturated sodium hydroxide.

[0030] (4) Separation and recovery of multiple metals: Based on a double-chamber ion membrane electrolysis device, the two chambers of the electrolytic cell are separated by a cation exchange membrane. 150 mL of electrolyte solution is poured into the cathode chamber, and an equal volume of precious metal leaching solution is placed in the anode chamber. A certain amount of potassium chloride solid is added and stirred to dissolve. At this time, the potassium chloride concentration in the precious metal leaching solution is 0.1 mol / L. The anode chamber solution is magnetically stirred at a speed of 500 rpm. The prepared coated electrodes are placed on both sides of the electrolytic cell, and a voltage of 2.5 V is applied (with the leaching solution side as the anode). The metal recovery test is started, and it is observed that gold is reduced at the anode and copper is reduced at the cathode.

[0031] like Figure 1~2 As shown in Figure 2, after 48 hours, the recovery rate of anode precious metal gold was 78.8%, and the recovery rate of cathode copper was 77.2% ( Figure 2 a). SEM-EDS characterization of the electrode material after reaction, such as Figure 3 As shown, it can be seen that 100% of the metal on the cathode is copper; among the metals on the anode, precious metals account for 92.6%, and there is a small amount of copper on the anode material, which may be due to the electrode material having a certain adsorption effect on the high-concentration copper complex ions in the solution. In general, the present invention realizes the efficient separation and recovery of precious metals and other metals in the solution.

[0032] Comparative Example 1 The metal separation and recovery test was carried out using the same method and apparatus as in Example 1, except that the electrodes were replaced with clean, uncoated titanium plates. After the test, the recovery rate of precious metals was calculated to be only 0.5% ( Figure 1 ), the copper recovery rate is 49.7% ( Figure 2 b), showing that the use of coated electrodes has a significant impact on metal recovery.

[0033] Comparative Example 2 The metal separation and recovery test was carried out using the same method and device as in Example 1, except that no cation exchange membrane was placed in the electrolytic device, that is, the device did not have a cathode and an anode chamber, and the electrolytic cell contained a mixture of precious metal leaching solution and electrolyte solution. At the same time, the electrodes were replaced with clean titanium plates that were not coated with adsorbent materials (compared with Comparative Example 1, only the cation exchange membrane was removed). After the test, the recovery rate of precious metals was calculated to be 90.1% ( Figure 1 ), the copper recovery rate was 91.7%. The electrode material after reaction was characterized by SEM-EDS, such as Figure 4As shown, it can be seen that no precious metals were found on the anode. Except for the titanium plate substrate, the only metal present was copper. This may be due to a small amount of copper complex ions adhering to the anode that was not rinsed clean. The precious metal mass on the cathode accounted for only 0.9% and copper accounted for 99.1%, indicating that although traditional electrodeposition can achieve a higher precious metal recovery rate, there is a serious problem of multi-metal co-deposition, resulting in extremely low precious metal grade, thereby increasing the separation and purification process in the subsequent metal extraction process.

[0034] Example 2 (1) Leaching of precious metals: Dissolve copper sulfate pentahydrate in pure water, add 5% mass concentration ammonia water and stir for 20 min, then add ammonium thiosulfate to dissolve and prepare a solution, then add 20 mg of silver powder at a liquid-to-solid ratio of 10:1, stir and leach for 2 h at room temperature, filter after leaching to obtain 150 mL of precious metal leachate, wherein the concentration of thiosulfate in the precious metal leachate is 0.1 mol / L, the concentration of precious metal silver is 49 mg / L, and the concentration of base metal copper is 274 mg / L.

[0035] (2) Electrode preparation: 36 mg of activated carbon, 4 mg of conductive carbon black and 0.4 mL of binder (prepared by dissolving 0.1 g of vinylidene fluoride in 8 mL of NN-dimethylacetamide organic solvent) were thoroughly ground and mixed, and evenly coated on a titanium plate. The plate was placed in a 60°C oven for drying, and then taken out and soaked in pure water for 8 h to remove any loose materials. The plate was then dried again to obtain a coated electrode for use.

[0036] (3) Preparation of electrolyte: Weigh 2.236 g potassium chloride and dissolve it in 149 mL pure water to prepare 150 mL of 0.2 mol / L electrolyte, and adjust the solution pH to 6 with saturated sodium hydroxide.

[0037] (4) Separation and recovery of multiple metals: Based on a double-chamber ion membrane electrolysis device, the two chambers of the electrolytic cell are separated by a cation exchange membrane. Pour 150mL of electrolyte solution into the cathode chamber, put an equal volume of precious metal leaching solution into the anode chamber, and add a certain amount of potassium chloride solid and stir to dissolve. At this time, the potassium chloride concentration in the precious metal leaching solution is 0.1mol / L. The anode chamber solution is magnetically stirred at a speed of 500rpm. The prepared coated electrodes are placed on both sides of the electrolytic cell, and a voltage of 2.5V is applied (with the leaching solution side as the anode), and the anode recovery test of precious metals is started.

[0038] After the test, the recovery rate of precious metal silver was 100%, and the recovery rate of copper was 77.2% ( Figure 5 ). SEM-EDS characterization of the electrode material after reaction ( Figure 6), the results showed that the metal on the cathode was only copper (100% copper); the metal on the anode was 68.1% precious metal, of which a small amount of copper was also on the anode material, which may be due to the adsorption of a small amount of copper complex ions on the electrode material. It can be seen that this method can achieve the separation and recovery of precious metals and base metals in precious metal leachate.

[0039] In summary, the electrochemical separation and recovery method of multiple metals provided by the present invention: anode reduction of precious metals - cathode reduction of other metals, realizes the one-step separation and reduction recovery of precious metals and other metals, which can not only shorten the metal recovery process, but also promote the efficient and high-quality extraction of precious metals.

[0040] 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.

[0041] 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 method for electrochemical separation and recovery of multiple metals, characterized in that: The steps include: Providing an electrolytic cell having a cation exchange membrane; the cation exchange membrane separates the electrolytic cell into a cathode chamber and an anode chamber; providing a cathode and an anode; preparing electrolyte solution; placing a polymetallic thiosulfate leachate, a chloride salt and an anode in the anode chamber, and placing the electrolyte solution and a cathode in the cathode chamber; A voltage is applied to the cathode and the anode, and after the reaction is completed, the base metal deposited on the cathode and the precious metal deposited on the anode are respectively recovered.

2. The electrochemical separation and recovery method of multiple metals according to claim 1, characterized in that: The cathode and the anode are both electrode plates coated with an adsorption material layer.

3. The electrochemical separation and recovery method of multiple metals according to claim 2, characterized in that: The adsorption material includes one or more of activated carbon, graphite, graphene, graphene oxide, molybdenum disulfide, and cadmium sulfide.

4. The electrochemical separation and recovery method of multiple metals according to claim 2, characterized in that: The electrode plate is one of a stainless steel plate, a titanium plate, a graphite felt, a carbon felt, a carbon paper, and a carbon cloth.

5. The electrochemical separation and recovery method of multiple metals according to claim 1, characterized in that: The concentration of the electrolyte solution is 0.1-0.5 mol / L, and the pH is 3-10.

6. The electrochemical separation and recovery method of multiple metals according to claim 1, characterized in that: The electrolyte solution is one or more of a sodium chloride solution, a potassium chloride solution, an ammonium chloride solution, a sodium sulfate solution, a potassium sulfate solution, and an ammonium sulfate solution.

7. The electrochemical separation and recovery method of multiple metals according to claim 1, characterized in that: The concentration of thiosulfate in the polymetallic thiosulfate leachate is 0.1-0.5 mol / L, the concentration of precious metals is 2-100 mg / L, and the concentration of base metals is 50-2000 mg / L.

8. The electrochemical separation and recovery method of multiple metals according to claim 1, characterized in that: The dosage ratio of the polymetallic thiosulfate leaching solution to the chloride salt is 150mL: (0.01-0.5) mol / L; the chloride salt includes one or more of sodium chloride, potassium chloride, and ammonium chloride.

9. The electrochemical separation and recovery method of multiple metals according to claim 1, characterized in that: The voltage applied to the cathode and the anode is 1.4-4.0V.

10. The electrochemical separation and recovery method of multiple metals according to claim 1, characterized in that: The precious metals include gold and / or silver; the base metals include one or more of copper, iron, lead, manganese and chromium.

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