A method for recovering precious metals based on the combination of porous materials and electrochemical reduction method

Abstract

The present invention discloses a method for recovering precious metals based on a combination of porous materials and electrochemical reduction. The method comprises the following steps: preparing a porous electrode using a porous material; using the two porous electrodes as a cathode and an anode respectively, placing them in an electrolytic cell containing a precious metal solution, connecting them to an external power source, and recovering the precious metals through the combined electrochemical reduction of the porous materials. The present invention combines porous materials and the electrochemical reduction method, uses the porous material as the electrode material, and different pores play the roles of transmitting, adsorbing and amplifying the current effect, realizing the integration of adsorption and reduction. The precious metal ions are recovered in the form of elemental substances. Compared with the traditional adsorption method and electroplating method, not only the process flow is simplified, but also the efficient recovery of precious metals is realized, and the recovery rate reaches 100%.

Description

Technical Field

[0001] The present invention relates to the technical field of precious metal recovery, and particularly to a method for recovering precious metals based on a porous material combined with an electrochemical reduction method. Background Art

[0002] Precious metals such as gold and silver are widely used in fields such as aviation, aerospace, military industry, jewelry, new energy, and electronic information technology due to their high melting points, good electrical conductivity, etc. However, precious metal resources are limited, with low mineral reserves and non-renewability in nature, and they are expensive. Therefore, the resource-based recovery and utilization of precious metals is a trend of sustainable development.

[0003] Currently, precious metals mainly exist in metallurgical wastewater and secondary resources. After the precious metals are oxidized to precious metal ions, it is necessary to separate and extract the precious metal ions in the solution. Methods for recovering precious metals from solutions include displacement method, precipitation method, ion exchange method, solution extraction method, adsorption method, etc. The displacement method realizes separation and purification by adding active metal ions to displace precious metal ions, but the cost is relatively high; the precipitation method obtains relevant solid products by reacting a precipitating agent with a metal salt solution, but the precipitating agent and reducing agent added during the operation process will cause secondary pollution; the ion exchange method uses the freely moving ions in the ion exchanger to exchange with the precious metal ions in the solution to achieve separation and enrichment, but its operation is complex and it is not conducive to secondary utilization; the solution extraction method transfers the metal ions in the aqueous phase to the organic phase by selecting a suitable extractant, but the organic extractant seriously pollutes the environment and the operation process is relatively complex; the adsorption method is one of the methods with relatively simple operation and low operating cost, and plays a certain role in the recovery of precious metal resources. However, after adsorbing precious metal ions based on this method, steps such as desorption and reduction are still required, and the overall process is relatively cumbersome, and traditional carbon materials have a small specific surface area and insufficient adsorption capacity.

[0004] Therefore, it is very important to develop new technologies for highly efficient and pollution-free enrichment and recovery of precious metal resources both economically and environmentally. Summary of the Invention

[0005] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a method for recovering precious metals based on a porous material combined with an electrochemical reduction method, so as to solve the problems of cumbersome operation and low recovery rate in the current recovery of precious metals from solutions.

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

[0007] The present invention provides a method for recovering precious metals based on a porous material combined with an electrochemical reduction method, including the following steps:

[0008] Preparing a porous electrode using a porous material;

[0009] Use the two porous electrodes as the cathode and anode respectively, place them in an electrolytic cell containing a precious metal solution, connect them to an external power supply, and recover the precious metal through combined electrochemical reduction by the porous material.

[0010] Preferably, the concentration of the precious metal solution is a low-concentration precious metal solution at the ppm level or ppb level.

[0011] Preferably, the precious metal is gold or silver.

[0012] Preferably, the preparation method of the porous electrode includes:

[0013] Provide a substrate;

[0014] Provide a slurry containing a porous material and a binder, coat the slurry on the surface of the substrate, and obtain the porous electrode after drying.

[0015] Preferably, the slurry includes a conductive material.

[0016] Preferably, the preparation method of the porous material includes:

[0017] Provide a carbon precursor;

[0018] Physically or chemically activate the carbon precursor to obtain the porous material.

[0019] The beneficial effects of the present invention are:

[0020] The present invention combines a porous material and an electrochemical reduction method, uses the porous material as an electrode material, and different pores play the effects of transporting, adsorbing, and amplifying current, realizing the integration of adsorption and reduction. The precious metal ions are recovered in the form of a single substance. Compared with the traditional adsorption method and electroplating method, not only the process flow is simplified, but also the efficient recovery of precious metals is realized, and the recovery rate reaches 100%. Description of the Drawings

[0021] Figure 1 It is the silver recovery effect diagram in Examples 1 to 3 and Comparative Example 1;

[0022] Figure 2 It is the gold recovery effect diagram in Examples 4 to 5 and Comparative Example 2. Detailed Embodiments

[0023] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0024] Existing methods for recovering precious metals from solutions include displacement method, precipitation method, ion exchange method, solution extraction method, adsorption method, etc. During the operation of the displacement method, the precipitants and reducing agents added will cause secondary pollution; the operation of the ion exchange method is complex and not conducive to secondary utilization; the organic extractants of the solution extraction method cause serious environmental pollution, and the operation process is relatively complex; after the adsorption method adsorbs precious metal ions, steps such as desorption and reduction are still required, and the overall process is relatively cumbersome, and it is difficult to achieve efficient recovery of multiple precious metals with the current adsorbents.

[0025] Based on this, the present invention proposes a method for recovering precious metals based on a porous material combined with an electrochemical reduction method, including the following steps:

[0026] S1. Prepare a porous electrode using a porous material;

[0027] S2. Use the two porous electrodes as the cathode and anode respectively, place them in an electrolytic cell containing a precious metal solution, connect them to an external power source, and recover the precious metal through the combined electrochemical reduction of the porous material.

[0028] Further, in some embodiments, the concentration of the precious metal solution is a low-concentration precious metal solution at the ppm level or ppb level. The concentration of the precious metal solution includes but is not limited to 0.01 - 100 mg / L, and is further preferably 1 - 10 mg / L; for example, it can be 0.01 mg / L, 1 mg / L, 5 mg / L, 10 mg / L, etc.

[0029] Further, in some embodiments, the voltage of the electrochemical reduction is ≥0.4V, preferably 0.4 - 1.6V; for example, it can be 0.4V, 0.5V, 0.8V, 1.0V, 1.2V, 1.4V, 1.6V, etc.

[0030] Further, in some embodiments, the preparation method of the porous electrode includes:

[0031] Provide a substrate; provide a slurry containing a porous material and a binder, coat the slurry on the surface of the substrate, and obtain the porous electrode after drying.

[0032] Further, in some embodiments, the substrate is a metal-based or carbon-based electrode plate, such as a titanium plate, a platinum plate, a stainless steel plate, a nickel foam plate, etc.

[0033] Further, in some embodiments, the slurry includes a porous material, a conductive material, and a binder. The conductive material includes but is not limited to conductive carbon black, and the binder includes but is not limited to polyvinylidene fluoride.

[0034] Further, in some embodiments, the porous material is a porous activated carbon material. The preparation method of the porous material is to provide a carbon precursor; physically or chemically activate the carbon precursor to obtain the porous material. For example, acid or alkali vapor activation is performed on the carbon precursor.

[0035] Further, in some embodiments, the preparation method of the porous activated carbon material includes: crushing and screening walnut shells, followed by high-temperature calcination to obtain a carbon precursor; mixing the carbon precursor with potassium hydroxide, grinding, and then performing high-temperature calcination. After washing and drying, the porous activated carbon material is obtained. The temperature of the high-temperature calcination is not limited, and preferably is 500 - 800 °C.

[0036] The present invention will be described in detail below with reference to specific embodiments.

[0037] Example 1

[0038] A method for recovering precious metals based on a porous material combined with an electrochemical reduction method includes the following steps:

[0039] Preparation of porous activated carbon: Crush and screen walnut shells to obtain a powder product, calcine it in a tubular furnace at 400 °C for 1 h under a nitrogen atmosphere. After cooling, wash it with ethanol and water, and then freeze-dry to obtain a carbonized product; then grind and mix the carbonized product with potassium hydroxide in a ratio of 1:3, calcine it at 700 °C for 2 h under a nitrogen atmosphere, wash it with hydrochloric acid and water, and freeze-dry to obtain a porous activated carbon material.

[0040] Preparation of porous activated carbon electrode: Mix the porous activated carbon material, conductive carbon black, and polyvinylidene fluoride in a ratio of 8:1:1 and grind to obtain a slurry, coat it on the surface of a titanium plate, and dry it to prepare a porous activated carbon electrode.

[0041] Recovery of precious metals: Prepare 200 mL of a 1 mg / L silver nitrate solution, pour the silver nitrate solution into an electrolytic cell, insert two electrode plates coated with a porous activated carbon material layer into the solution in the electrolytic cell, and make the sides coated with the porous activated carbon material layer face each other. Connect the two electrode plates to the positive and negative poles of a DC power supply through wires respectively. After adjusting the power supply voltage to 1.2 V, turn on a peristaltic pump to circulate the aqueous solution. After 22 h, take a sample from the solution and filter out insoluble solids with a filter head. The concentration of silver in the filtrate is measured by atomic absorption spectrometry, and the silver recovery rate is calculated to be 93.67%.

[0042] Example 2

[0043] The precious metals are recovered by using a method substantially the same as that in Example 1, except that the concentration of silver nitrate in the electrolytic cell is 5 mg / L. After 22 h, the silver recovery rate is 100%.

[0044] Example 3

[0045] The precious metals were recovered by a method basically the same as that in Example 1, except that the concentration of silver nitrate in the electrolytic cell was 10 mg / L. After 22 h, the silver recovery rate was 100%.

[0046] Comparative Example 1

[0047] A method for recovering precious metals by traditional electrochemistry reduction method includes the following steps:

[0048] Prepare 200 mL of silver nitrate solution and pour it into the electrolytic cell. Insert two electrode plates (pure titanium plates) without coated porous activated carbon electrode materials into the solution in the electrolytic cell. Connect the two electrode plates to the positive and negative poles of the DC power supply through wires respectively. After adjusting the power supply voltage to 1.2 V, turn on the peristaltic pump to circulate the aqueous solution. After 22 h, take a sample from the solution and filter off the insoluble solids with a filter head. The concentration of silver in the solution was obtained by atomic absorption spectroscopy test of the filtrate.

[0049] As Figure 1 shown, the electrochemistry reduction of silver nitrate with concentrations of 1 mg / L, 5 mg / L, and 10 mg / L was carried out by traditional electrochemistry reduction method respectively. After 22 h, the measured silver recovery rates were 55.21%, 52.38%, and 53.45% respectively.

[0050] Comparative Example 2

[0051] A method for recovering precious metals by traditional adsorption method includes the following steps:

[0052] Prepare 200 mL of silver nitrate solution with a concentration of 5 mg / L and pour it into the electrolytic cell. Insert two electrode plates coated with a porous activated carbon material layer into the solution in the electrolytic cell and make the sides coated with the porous activated carbon material layer face each other. Connect the two electrode plates to the positive and negative poles of the DC power supply through wires respectively. Adjust the power supply voltage to 0 V, turn on the peristaltic pump to circulate the aqueous solution. After 22 h, take a sample from the solution and filter off the insoluble solids with a filter head. The concentration of silver in the solution was obtained by atomic absorption spectroscopy test of the filtrate. The calculated silver recovery rate was 22%.

[0053] Example 4

[0054] A method for recovering precious metals based on the combined electrochemistry reduction method of porous materials prepares a porous activated carbon electrode by the same method as in Example 1.

[0055] Prepare 200 mL of aurothiosulfate solution with a concentration of 1 mg / L, pour the aurothiosulfate solution into an electrolytic cell, insert two electrode plates coated with a porous activated carbon material layer into the solution in the electrolytic cell, and make the sides coated with the porous activated carbon material layer face each other. Connect the two electrode plates to the positive and negative electrodes of a DC power supply respectively through wires. After adjusting the power supply voltage to 1.2 V, turn on the peristaltic pump to circulate the aqueous solution. After 22 h, take a sample from the solution and filter out the insoluble solids with a filter head. The concentration of gold in the solution is obtained by atomic absorption spectroscopy test, and the gold recovery rate is calculated to be 100%.

[0056] Example 5

[0057] The precious metals were recovered by a method substantially the same as that of Example 4, except that the concentration of aurothiosulfate in the electrolytic cell was 5 mg / L. After 22 h, the gold recovery rate was 100%.

[0058] Example 6

[0059] The precious metals were recovered by a method substantially the same as that of Example 4, except that the concentration of aurothiosulfate in the electrolytic cell was 10 mg / L. After 22 h, the gold recovery rate was 100%.

[0060] Comparative Example 3

[0061] The method for recovering precious metals by the traditional electrochemical reduction method includes the following steps:

[0062] Prepare 200 mL of aurothiosulfate solution, pour the aurothiosulfate solution into an electrolytic cell, insert two electrode plates without coated porous activated carbon electrode materials (pure titanium plates) into the solution in the electrolytic cell, connect the two electrode plates to the positive and negative electrodes of a DC power supply respectively through wires. After adjusting the power supply voltage to 1.2 V, turn on the peristaltic pump to circulate the aqueous solution. After 22 h, take a sample from the solution and filter out the insoluble solids with a filter head. The concentration of gold in the solution is obtained by atomic absorption spectroscopy test.

[0063] Electrochemical reduction was carried out on aurothiosulfate with concentrations of 1 mg / L, 5 mg / L, and 10 mg / L respectively. After 22 h, as Figure 2 shown, the measured gold recovery rates were 61.79%, 50.89%, and 35.16% respectively.

[0064] Comparative Example 4

[0065] The method for recovering precious metals by the traditional adsorption method includes the following steps:

[0066] Prepare 200 mL of aurothiosulfate solution with a concentration of 5 mg / L, pour the aurothiosulfate solution into an electrolytic cell, insert two electrode plates coated with a porous activated carbon material layer into the solution in the electrolytic cell, and make the sides coated with the porous activated carbon material layer face each other. Connect the two electrode plates to the positive and negative poles of a DC power supply through wires respectively, adjust the power supply voltage to 0 V, turn on the peristaltic pump to circulate the aqueous solution, take a sample from the solution after 22 h and filter off the insoluble solids with a filter head, and the concentration of gold in the filtrate is obtained by atomic absorption spectrometry. The recovery rate of gold is calculated to be 27%.

[0067] Example 7

[0068] The precious metals are recovered by a method basically the same as that in Example 2, except that the voltage of the external power supply is 0.4 V, and the recovery rate of silver is measured to be 80%.

[0069] Example 8

[0070] The precious metals are recovered by a method basically the same as that in Example 2, except that the voltage of the external power supply is 0.8 V, and the recovery rate of silver is measured to be 96%.

[0071] Example 9

[0072] The precious metals are recovered by a method basically the same as that in Example 5, except that the voltage of the external power supply is 0.4 V, and the recovery rate of gold is measured to be 85%.

[0073] Example 10

[0074] The precious metals are recovered by a method basically the same as that in Example 5, except that the voltage of the external power supply is 0.8 V, and the recovery rate of gold is measured to be 100%.

[0075] In summary, the method of combining porous materials with electrochemical reduction in the present invention realizes the efficient recovery of low-concentration precious metals gold and silver. Compared with the low recovery rate of the traditional adsorption method for low-concentration precious metal solutions, the present invention can achieve a recovery rate of 100%.

[0076] It should be noted that the above embodiments all belong to the same inventive concept. The descriptions of the embodiments have their own emphases. For the parts not described in detail in individual embodiments, reference can be made to the descriptions in other embodiments.

[0077] The above-described embodiments only represent the implementation manners of the present invention. The descriptions are relatively specific and detailed, but should not be construed as limiting the scope of the invention patent. It should be pointed out that for those of ordinary skill in the art, without departing from the inventive concept of the present invention, several deformations and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent should be subject to the appended claims.

Claims

1. A method for recovering precious metals based on the combination of porous materials and electrochemical reduction method, characterized in that, It includes the following steps: Provide a slurry containing a porous material and a binder, coat the slurry on the surface of a substrate, and obtain a porous electrode after drying; Use the two porous electrodes as the cathode and anode respectively, place them in an electrolytic cell containing a precious metal solution, make the sides coated with the porous activated carbon material layer face each other, connect them to an external power supply, and recover the precious metal through combined electrochemical reduction of the porous material; Among them, the porous material is a porous activated carbon material, and the preparation method of the porous material includes: Provide a carbon precursor; Physically or chemically activate the carbon precursor to obtain the porous material.

2. The method according to claim 1, characterized in that, The concentration of the precious metal solution is a low-concentration precious metal solution at the ppm or ppb level.

3. The method according to claim 1, wherein The precious metal is gold or silver.

4. The method according to claim 1, wherein The slurry includes a conductive material.

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