Metal recovery method using nitric acid leaching and electrolysis

Abstract

The present invention relates to a metal recovery method using nitric acid leaching and electrolysis, and has the effect of providing a metal recovery method that is environmentally friendly by diluting high-concentration nitric acid (HNO3) used in a metal recovery process to a predetermined concentration for use, and that is economical and has improved process efficiency by recycling the nitric acid (HNO3) to enable resource circulation. In addition, the present invention has the effect of providing a metal recovery method using nitric acid leaching and electrolysis, in which electrolysis is performed while stirring at an appropriate speed, thereby increasing the recovery speed and significantly reducing the recovery time, and improving the recovery rate to 99.0% or more.

Description

Metal recovery method using nitric acid leaching and electrolysis

[0001] The present invention relates to a method for recovering metal using nitric acid leaching and electrolysis, and more specifically, to a method for recovering metal using nitric acid leaching and electrolysis characterized by not only being able to recover metal with high purity and recovery rate, but also enabling resource recycling by recycling nitric acid (HNO3) generated during the metal recovery process and improving process efficiency.

[0002]

[0003] According to the Ministry of Environment, the volume of discarded solar panels is projected to reach 988 tons in 2023, 1,223 tons in 2025, and 2,645 tons in 2027, and is expected to approach 28,153 tons in 2033. The global recycling market for discarded solar panels is also expected to grow from $205 million (260 billion won) in 2022 to $478 million (600 billion won) in 2026, according to the Korea Institute of Science and Technology Information, with an average annual growth rate of 20.2%, leading to the anticipated release of large amounts of waste solar cells.

[0004] As mentioned above, waste solar cells released in large quantities not only cause serious environmental pollution, but also, since expensive materials are used to increase photoelectric conversion efficiency, if these materials are discarded without recovery, it can cause serious environmental pollution in addition to the problem of resource waste. However, conventional methods of extracting and recovering valuable metals such as silver from waste that have been studied so far have problems in terms of recycling costs and energy consumption, as they require high-temperature conditions and long extraction processes.

[0005] Accordingly, as seen in the prior art, various research and development efforts are underway to recover valuable metals from spent solar cells. Conventional methods for leaching valuable metals from spent cells include acid leaching and alkaline leaching. In the case of acid leaching, valuable metals are recovered via electrolytic extraction after leaching using sulfuric acid (H2SO4); however, this method has disadvantages, such as difficulty in selectively recovering high-purity metals because large amounts of other components—including zinc, iron, and manganese—are leached out in addition to the metals intended for selective recovery, and the subsequent processes are complex or require multiple types of procedures. Furthermore, solutions mixed with hydrochloric acid, NaOH, hydroxide, and hydrofluoric acid exhibit rapid and violent reactions, resulting in high metal loss rates and the release of harmful gases, which continue to pose environmental challenges during the recovery process.

[0006] Accordingly, the inventor has completed the present invention by developing a technology capable of recovering high-purity valuable metals using only nitric acid and electrolytic extraction methods.

[0007]

[0008] The present invention aims to provide a metal recovery method that is not only environmentally friendly but also economical and has improved process efficiency by recycling nitric acid (HNO3) to enable resource circulation, by diluting the high-concentration nitric acid (HNO3) used in the metal recovery process to a predetermined concentration.

[0009] In addition, the present invention aims to provide a method for recovering metal using nitric acid leaching and electrolysis, which increases the recovery rate by stirring at an appropriate speed and significantly reduces the recovery time, and improves the recovery rate to over 99.0%.

[0010]

[0011] The present invention, for achieving the above objective, provides a method for recovering a metal using nitric acid leaching and electrolysis, characterized by comprising the steps of: leaching a metal-containing substance into an aqueous nitric acid (HNO3) solution to produce a leaching solution containing the metal; diluting the produced leaching solution; electrolyzing the diluted leaching solution to recover the metal; and filtering and drying the leaching solution from which the metal has been recovered.

[0012] In one embodiment of the present invention, the concentration of the aqueous nitric acid (HNO3) solution is characterized as being 40 to 70 weight%.

[0013] In one embodiment of the present invention, the metal-containing material is silver powder, waste solar cell, waste silver oxide battery, waste lithium-ion battery, or waste display panel, and is characterized by being in powder form.

[0014] In one embodiment of the present invention, the leaching solution is characterized by comprising an aqueous silver nitrate (AgNO3) solution.

[0015] In one embodiment of the present invention, the step of preparing the leaching solution is characterized by magnetic stirring at 400 to 800 rpm for 20 to 28 hours at 15 to 35°C.

[0016] In one embodiment of the present invention, in the step of recovering the metal, the concentration of silver dissolved in the diluted leaching solution is characterized as being 1.0 to 7.0 mg / mL.

[0017] In one embodiment of the present invention, the step of diluting the prepared leaching solution is characterized by diluting the prepared leaching solution with distilled water 5 to 15 times.

[0018] In one embodiment of the present invention, the apparatus for electrolysis may include an electrode portion comprising a cathode and an anode; and a power supply portion electrically connected to the electrode portion to apply voltage.

[0019] In one embodiment of the present invention, the cathode electrode is characterized by using an insoluble electrode coated with at least one component of titanium (Ti), palladium (Pd), iridium (Ir), ruthenium (Ru), and tantalum (Ta); a silver electrode; or an electrode made of stainless steel.

[0020] In one embodiment of the present invention, the cathode electrode is characterized by having a plate shape, a rod shape, a wire structure, a foil, a plate, a cylinder, or a bowl shape.

[0021] In one embodiment of the present invention, the electrolysis is characterized by applying a variable voltage of 0.8 to 5.0 V for 30 to 80 minutes.

[0022]

[0023] The present invention provides a metal recovery method that is not only environmentally friendly but also economical and has improved process efficiency by recycling nitric acid (HNO3) to enable resource circulation, by diluting the high-concentration nitric acid (HNO3) used in the metal recovery process to a predetermined concentration.

[0024] In addition, the present invention has the effect of providing a metal recovery method using nitric acid leaching and electrolysis that increases the recovery speed by stirring at an appropriate speed and significantly reduces the recovery time, and improves the recovery rate to over 99.0%.

[0025] The effects of the present invention are not limited to those mentioned above, and other unmentioned effects will be clearly understood by those skilled in the art from the description in the claims.

[0026]

[0027] FIG. 1 is a process block diagram illustrating a method for recovering metal using nitric acid leaching and electrolysis according to a preferred embodiment of the present invention.

[0028] Figure 2 is a photograph showing a copper electrode reacted with nitric acid (HNO3).

[0029] Figure 3 is a photograph showing the results of metal precipitation.

[0030] Figure 4 is a photograph showing the metal recovery process according to Example 1 of the present invention.

[0031] Figure 5 shows the XRD analysis results according to Example 1 of the present invention.

[0032] Figure 6 is a photograph showing the metal recovery process according to Example 5 of the present invention.

[0033] Figure 7 shows the SEM-EDS analysis results according to Example 4 of the present invention.

[0034] Figure 8 shows the SEM-EDS analysis results according to Example 4 of the present invention.

[0035] Figure 9 shows the SEM-EDS analysis results according to Example 5 of the present invention.

[0036]

[0037] The present invention will be described in detail below according to preferred embodiments with reference to the attached drawings, but specific descriptions of configurations and operations that are readily known to those skilled in the art will be omitted. Furthermore, it should be noted that the present invention is not necessarily limited by the following embodiments, and that those skilled in the art can make various modifications to the invention within the scope of the technical concept of the invention without departing from it.

[0038] The terms used in this specification have been selected based on currently widely used general terms whenever possible, taking into account their functions in the present invention; however, these terms may vary depending on the intent of those skilled in the art, case law, the emergence of new technologies, etc. Additionally, in specific cases, terms have been arbitrarily selected by the applicant, and in such cases, their meanings will be described in detail in the relevant description of the invention. Therefore, the terms used in this invention should be defined not merely by their names, but based on their meanings and the overall content of the invention.

[0039] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as generally understood by those skilled in the art to which the present invention pertains. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and should not be interpreted in an ideal or overly formal sense unless explicitly defined in this application.

[0040] Numerical ranges include the values ​​defined in the above ranges. All maximum numerical limits given throughout this specification include all lower numerical limits as clearly written. All minimum numerical limits given throughout this specification include all higher numerical limits as clearly written. All numerical limits given throughout this specification will include all better numerical ranges within a wider numerical range, as clearly written.

[0041]

[0042] The present invention provides a method for recovering valuable metals with high purity that is economical and capable of reducing carbon emissions as part of a method for recovering valuable metals.

[0043]

[0044] Hereinafter, a method for recovering metal using nitric acid leaching and electrolysis according to a preferred embodiment of the present invention will be described.

[0045]

[0046] A method for recovering metal using nitric acid leaching and electrolysis according to the present invention may include the steps of: leaching a metal-containing substance into an aqueous nitric acid (HNO3) solution to produce a leaching solution containing the metal; diluting the produced leaching solution; electrolyzing the diluted leaching solution to recover the metal; and filtering and drying the leaching solution in which the metal has been recovered.

[0047]

[0048] First, the present invention may include the step of preparing a leaching solution containing the metal by leaching a metal-containing material into an aqueous nitric acid (HNO3) solution.

[0049]

[0050] The concentration of the above aqueous nitric acid (HNO3) solution may be 40 to 70 weight%, more preferably 50 to 65 weight%, and most preferably 60 weight%.

[0051]

[0052] The metal-containing material may be silver powder, waste solar cells, waste silver oxide batteries, waste lithium-ion batteries, or waste display panels. The metal-containing material may be in the form of powder after being physically crushed through a crushing device. Through this, a leaching solution containing the metal can be prepared.

[0053]

[0054] The above metal may contain one or more selected from the group consisting of gold, silver, platinum, copper, manganese, nickel, cobalt, palladium, and zinc, but it is more preferable to contain silver.

[0055] The above leaching solution may include an aqueous solution of silver nitrate (AgNO3) which serves as a silver ion source.

[0056]

[0057] The step of preparing the above-mentioned leachate may be prepared by magnetic stirring at 400 to 800 rpm for 20 to 28 hours at 15 to 35°C, and most preferably by magnetic stirring at 600 rpm for 24 hours at 30°C.

[0058]

[0059] The concentration of silver dissolved in the above diluted leaching solution may be 1.0 to 7.0 mg / mL, more preferably 2.0 to 5.0 mg / mL, and most preferably 3.0 to 6.0 mg / mL. That is, by setting the concentration of silver dissolved in the above diluted leaching solution to 1.0 mg / mL or higher, the precipitation rate of silver can be increased to a level that is industrially satisfactory. In addition, by setting the concentration of silver to 7.0 mg / mL or lower, silver particles having a desired crystal shape can be obtained smoothly.

[0060]

[0061] Next, the present invention may include a step of diluting the prepared leaching solution. At this time, the prepared leaching solution may be diluted with distilled water 5 to 15 times.

[0062] The present invention is characterized by the technical feature of preparing a leaching solution using a high-concentration aqueous nitric acid solution so that a metal-containing material can be dissolved with a higher solubility, and then diluting the leaching solution with distilled water.

[0063]

[0064] Next, the present invention may include a step of recovering the metal by electrolyzing the diluted leaching solution.

[0065] The present invention may include an electrode section comprising a cathode electrode and an anode electrode as a device for electrolysis; and a power supply section electrically connected to the electrode section to apply voltage. In this case, the cathode electrode and the anode electrode may be immersed in the diluted leaching solution, and voltage may be applied using a power supply. That is, the present invention is characterized by preparing a leaching solution with an aqueous nitric acid (HNO3) solution, diluting it, and then precipitating a valuable metal on the cathode electrode by electrolysis.

[0066]

[0067] For the above cathode electrode, a material that does not affect the reduction of silver ions may be selected. For example, an insoluble electrode coated with at least one component of titanium (Ti), palladium (Pd), iridium (Ir), ruthenium (Ru), and tantalum (Ta); a silver electrode; or an electrode made of stainless steel may be used, and more preferably, an electrode made of SUS 304, SUS 316, or SUS 430.

[0068] The above cathode electrode may be formed in a plate shape, a rod shape, a wire structure, a foil, a plate, a cylinder, or a bowl shape, and more preferably may be formed in a cylinder or bowl shape. In one embodiment of the present invention, when the cathode electrode is formed in the cylinder or bowl shape, it not only has a large surface area but also has the effect of excellent electrical stability by allowing a natural electrolytic flow without being affected by the gap between electrodes.

[0069]

[0070] The above anode electrode may use a copper electrode or a copper plate having a wire structure. That is, the diluted leaching solution may be diluted 5 to 15 times based on the prepared leaching solution. If diluted to a range less than this, nitric acid (HNO3) remains, so the copper (Cu) electrode of the anode may react preferentially with the nitric acid rather than reacting with the silver nitrate (AgNO3) aqueous solution to be substituted with Ag. In other words, the copper (Cu) electrode may react with the nitric acid as shown in FIG. 2 simply by the process of inserting the copper electrode before applying current.

[0071]

[0072] In the case of silver (Ag) deposited on the above cathode electrode, it may be deposited according to the following chemical formula.

[0073]

[0074] Chemical formula (1)

[0075] 3Ag(S) + 4HNO3(ag) → 3AgNO3(ag) + NO(g) + 2H2O(l)

[0076] Chemical formula (2)

[0077] 2HNO3(ag) + Cu(s) → Cu(NO3)2(ag) + 2Ag(S)

[0078]

[0079] In other words, when voltage is applied, the copper (Cu) of the anode electrode undergoes substitution with the Ag in the AgNO3 aqueous solution, causing the solution to change into CuNO3, and Ag + It may be deposited by adhering to the cathode electrode. At this time, the color of the solution may be transparent (AgNO3) and then change to sky blue as it becomes CuNO3 over time.

[0080]

[0081] Under the above electrolysis conditions, the applied current may be applied as a constant current in the range of 300 to 600 mA, and most preferably as a constant current in the range of 500 mA.

[0082]

[0083] The above voltage may be applied by varying it in the range of 0.8 to 5.0 V, and more preferably by varying it in the range of 0.9 to 1.6 V.

[0084] When applying voltage exceeding the above range, as shown in FIG. 3, silver is deposited on the cathode electrode, and if this continues for more than 10 minutes after the end of electrolysis, the electrode area is too small, so the deposited silver may dissolve back into the leaching solution; therefore, the process is characterized by being performed within the above range.

[0085]

[0086] That is, by applying voltage and current within the above range, the temperature rise of the electrolyte can be suppressed, thereby stabilizing the shape of the silver particles, and the precipitation rate of silver can be increased, thereby suppressing the coarsening of the silver particles.

[0087]

[0088] The above electrolysis time may be 30 to 80 minutes, more preferably 40 to 70 minutes, and most preferably 60 minutes.

[0089] If the above reaction conditions fall below the range specified above, there is a risk that the metal will not be sufficiently reduced, and if they exceed the range specified above, there is a risk that the amount of reduction will decrease.

[0090]

[0091] Meanwhile, the present invention is characterized by the technical feature of stirring the leaching solution using a magnetic bar during the precipitation process in which AgNO3 is substituted with CuNO3 through the electrolysis.

[0092] The stirring speed may be 60 to 100 rpm, and most preferably 80 rpm. By stirring the leaching solution at an appropriate speed in this way, the rate at which AgNO3 is substituted with Cu(NO3)2 is increased, thereby increasing the recovery rate and drastically reducing the recovery time.

[0093]

[0094] By carrying out electrolysis under the above conditions, the desired silver can be recovered by scraping off the precipitated silver particles from the cathode. The metal recovered in this way may be washed with distilled water three or more times.

[0095]

[0096] Furthermore, the present invention may further include the step of stopping the application of voltage after the electrolysis reaction of 30 to 80 minutes is completed and recovering the metal, and then immediately diluting it 2 to 3 times with distilled water, before washing the recovered metal to prevent further dissolution of the silver precipitated in the remaining solution.

[0097]

[0098] Next, the present invention may include the step of filtering and drying the leaching solution in which the metal has been recovered. The Cu(NO3)2 solution remaining after the metal has been recovered may be filtered, and then the filtered solution may be heated in a vacuum oven at a temperature of 100 to 140°C for 4 to 10 hours to further recover the metal present in the Cu(NO3)2 solution.

[0099] For reference, the above drying conditions can be appropriately adjusted depending on the amount of solvent to be evaporated after washing, so they are not necessarily limited to the above conditions.

[0100]

[0101] The recovery rate of the metal recovered through the above electrolysis can be 99.0% or higher.

[0102]

[0103] The recovered metal may include silver (Ag), nickel, or copper.

[0104]

[0105] Furthermore, the present invention has the effect of improving resource recycling and process efficiency by reintroducing Cu(NO3)2 generated by using a copper electrode as the anode electrode into the Cu process. That is, it has the effect of recycling nitric acid (HNO3) according to the following chemical formula.

[0106]

[0107] (Chemical Formula 3)

[0108] 3Cu(s) + 8HNO3(ag) → 3Cu(NO3)2(ag) + 2NO2(g) + 4H2O(l)

[0109] (Chemical Formula 4)

[0110] 3Cu(NO3)2(ag) + H2SO4(ag) → CuSO4(ag) + 2HNO3(ag)

[0111]

[0112] Hereinafter, a method for recovering metal using nitric acid leaching and electrolysis according to the present invention will be specifically explained through the following examples, and the present invention is not necessarily limited to the following examples.

[0113]

[0114] Example 1.

[0115] An aqueous solution of nitric acid (HNO3) with a concentration of 60 wt% was prepared. Subsequently, 1.0 g of silver powder was mixed into 30 ml of the aqueous nitric acid solution and dissolved by magnetic stirring at 600 rpm for 24 hours at 30°C. Through this process, an aqueous solution of silver nitrate (AgNO3) was prepared as a leachate. Distilled water was added to the aqueous solution of silver nitrate (AgNO3) to dilute it tenfold to a total volume of 300 ml, thereby preparing a diluted leachate.

[0116] The above-mentioned diluted leaching solution was placed in a SUS304 bowl and electrolyzed under the following conditions using a variable power supply. At this time, the SUS304 bowl was used as the cathode electrode, and a copper electrode with a wire structure was used as the anode electrode. After the electrolysis was completed, distilled water was added to the remaining solution to dilute it to a total volume of approximately 2.3 times (700 mL), and the metal precipitated through electrolysis was washed three times with distilled water. In addition, the Cu(NO3)2 solution remaining after the metal was recovered was filtered and heated in a vacuum oven at a temperature of 120°C for 6 hours to recover silver (Ag). For reference, Figure 4 is an actual photograph showing the metal recovery process according to Example 1.

[0117] · Anode: Copper wire

[0118] · Cathode: SUS304 Bowl

[0119] · Electrolysis time: 60 minutes

[0120] · Current: 500mA

[0121] · Voltage range: 0.9 to 1.6V

[0122] · Stirring speed: 80 rpm

[0123]

[0124] Example 2.

[0125] An aqueous silver nitrate (AgNO3) solution was prepared by mixing 0.25 g of silver powder with 8 ml of the above aqueous nitric acid (HNO3) solution, and a diluted extract was prepared by adding distilled water to make a total of 80 ml. The procedure was carried out in the same manner as in Example 1.

[0126]

[0127] Comparative Example 1.

[0128] An aqueous silver nitrate (AgNO3) solution was prepared by mixing 1.5 g of silver powder with 90 ml of the above aqueous nitric acid (HNO3) solution, and a diluted extract was prepared by adding distilled water to make a total of 900 ml. The procedure was carried out in the same manner as in Example 1 above.

[0129]

[0130] Experimental Example 1.

[0131] In order to compare the recovery rates according to the concentration of silver dissolved in a diluted aqueous silver nitrate solution, silver was recovered using the methods of Examples 1 and 2 and Comparative Example 1. The respective recovery rates are shown in Table 1.

[0132] The results of Table 1 below demonstrate that the recovery rate of silver (Ag) is much higher when the leaching solution is prepared as in Examples 1 and 2 compared to when the leaching solution is prepared as in Comparative Example 1. For reference, Figure 5 shows the results of XRD analysis on the silver recovered by the method of Example 1, and it is determined that the recovered Ag and the reference Ag peaks match.

[0133]

[0134] Parameter Initial Mass(g) Recovery mass(g) Recovery rate(%) Example 11G_V300 1.00 460.96 96 96.51 Example 20.25G_V800 0.25 200 0.24 6 97.62 Comparative Example 11.5G_V900 1.54 97 1.38 83 89.59

[0135]

[0136] Example 3.

[0137] The procedure was carried out in the same manner as in Example 1 above, but electrolyzed for 40 minutes.

[0138]

[0139] Comparative Example 2.

[0140] The procedure was carried out in the same manner as in Example 1 above, but electrolyzed for 70 minutes.

[0141]

[0142] Comparative Example 3.

[0143] The procedure was carried out in the same manner as in Example 1 above, but electrolyzed for 30 minutes.

[0144]

[0145] Experimental Example 2.

[0146] In order to compare the recovery rates according to the electrolysis time, silver was recovered using the methods of Example 1, Example 3, and Comparative Examples 2 and 3. The respective recovery rates are shown in Table 2.

[0147]

[0148] Parameter Initial Mass(g) Recovery mass(g) Recovery rate(%) Example 11G_V300_1H 1.00 46 0.9 69 69 6.51 Example 31G_V300_40M 1.01 30 0.8 79 78 6.84 Comparative Example 21G_V300_70M 1.00 95 0.9 58 19 4.91 Comparative Example 31G_V300_30M 1.02 47 0.8 158 79 6.1

[0149]

[0150] Example 4.

[0151] An aqueous silver nitrate (AgNO3) solution was prepared by mixing 1.0 g of silver powder with 20 ml of the above aqueous nitric acid (HNO3) solution, and a diluted leaching solution was prepared by adding distilled water to make a total of 200 ml. The diluted leaching solution was placed in a SUS304 bowl, and the procedure was carried out in the same manner as in Example 1.

[0152]

[0153] Example 5.

[0154] The procedure was carried out in the same manner as in Example 4 above, but the diluted leaching solution was placed in a SUS 316 cylinder. Otherwise, the procedure was carried out in the same manner as in Example 4 above.

[0155] For reference, Figure 6 shows a schematic diagram and an actual photograph illustrating the metal recovery process according to Example 5 above.

[0156]

[0157] Experimental Example 3.

[0158] In order to compare the recovery rates according to the type of cathode electrode, silver was recovered using the methods of Examples 4 and 5 above. The respective recovery rates are shown in Table 3.

[0159] Meanwhile, in the case of Example 4, Crystalline Ag was precipitated at the beginning of the electrolysis reaction, followed by the formation of gray Sludge Ag after 30 minutes, and it was observed that no more silver was precipitated from the Cu wire after 50 minutes. Meanwhile, upon washing, red (Cu) and gray sludge were identified. As a result of SEM-EDS analysis, as shown in Figure 7, elements were measured at 3 to 4 random points, and their average values ​​were calculated. As shown in Figure 8, it was found that the Ag composition was 95.86%, and the recovery rate was calculated based on this.

[0160] In addition, in the case of Example 5, Crystalline Ag was precipitated at the beginning of the electrolysis reaction, and Sludge Ag was formed starting from the bottom of the cathode electrode after 26 minutes. Meanwhile, during washing, not only gray Sludge but also a slight red color was observed, and as a result of SEM-EDS analysis, it was found that the composition of Ag was 79.68% as shown in Figure 9, and the recovery rate was calculated based on this.

[0161]

[0162] ParameterInitial Mass(g)Recovery mass(g)Recovery rate(%)Example 4SUS 304 Bowl(D10_V200_1hr)0.973941.0256100.94Example 5SUS 316Cylinder(D10_V200_1hr)0.973941.183396.81

[0163]

[0164] Although a method for recovering metal using nitric acid leaching and electrolysis according to a preferred embodiment of the present invention has been described as above, this is merely an example, and those skilled in the art will understand that various changes and modifications are possible within the scope of the technical spirit of the present invention.

Claims

1. A step of preparing a leaching solution containing the metal by leaching a metal-containing substance into an aqueous nitric acid (HNO3) solution; A step of diluting the above-mentioned leachate; A step of recovering the metal by electrolyzing the above diluted leachate; and A method for recovering metal using nitric acid leaching and electrolysis, characterized by including the step of filtering and drying the leaching solution from which the metal has been recovered.

2. In Paragraph 1, The concentration of the above aqueous nitric acid (HNO3) solution is, A method for recovering metal using nitric acid leaching and electrolysis, characterized by being 40 to 70 weight% 3. In Paragraph 1, The above metal-containing material is, It is silver powder, waste solar cells, waste silver oxide batteries, waste lithium-ion batteries, or waste display panels, and A method for recovering metal using nitric acid leaching and electrolysis, characterized by being in powder form 4. In Paragraph 1, The above leaching solution is, A method for recovering metal using nitric acid leaching and electrolysis, characterized by including an aqueous solution of silver nitrate (AgNO3).

5. In Paragraph 1, The step of preparing the above leaching solution is, A method for recovering metal using nitric acid leaching and electrolysis, characterized by magnetic stirring at 400 to 800 rpm for 20 to 28 hours at 15 to 35°C.

6. In Paragraph 1, In the step of recovering the above metal, A method for recovering metal using nitric acid leaching and electrolysis, characterized in that the concentration of silver dissolved in the above-described diluted leaching solution is 1.0 to 7.0 mg / mL.

7. In Paragraph 1, The step of diluting the above-mentioned leachate is, A method for recovering metal using nitric acid leaching and electrolysis, characterized by diluting the above-prepared leaching solution with distilled water 5 to 15 times.

8. In Paragraph 1, As a device for the above-mentioned electrolysis, A method for recovering metal using nitric acid leaching and electrolysis, characterized by comprising: an electrode portion including a cathode and an anode; and a power supply portion electrically connected to the electrode portion to apply voltage.

9. In Paragraph 8, The above cathode electrode is, A method for recovering metal using nitric acid leaching and electrolysis, characterized by using an insoluble electrode coated with at least one component selected from titanium (Ti), palladium (Pd), iridium (Ir), ruthenium (Ru), and tantalum (Ta); a silver electrode; or an electrode made of stainless steel.

10. In Paragraph 8, The above cathode electrode is, A method for recovering metal using nitric acid leaching and electrolysis, characterized by having a plate shape, rod shape, wire structure, foil, plate, cylinder, or bowl shape.

11. In Paragraph 1, The above electrolysis is, A method for recovering metal using nitric acid leaching and electrolysis, characterized by applying a variable voltage of 0.8 to 5.0 V for 30 to 80 minutes.

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