Method for efficiently separating and recycling silver and dibutyl phthalate in silver-containing waste liquid

Abstract

The invention relates to a method for efficiently separating and recycling silver and dibutyl phthalate in silver-containing waste liquid. The method comprises the following steps: preparing a separating agent; performing liquid-solid separation on the collected laboratory silver-containing waste liquid to obtain filtrate and silver-containing precipitate; a separating agent is added into the obtained precipitate for heating separation, and silver precipitate, an organic phase and a water phase are obtained; ammonia water is added into the obtained precipitate for leaching, and a [Ag (NH3) 2] < + > solution and leaching residues are obtained; adding a reducing agent into the [Ag (NH3) 2] < + > solution to obtain sponge silver; adding an alkaline substance into the obtained organic phase to obtain regenerated dibutyl phthalate; and washing and smelting the sponge silver to obtain metal silver. According to the scheme provided by the invention, silver and dibutyl phthalate can be efficiently separated and recovered.

Description

Technical Field

[0001] The present application relates to the technical field of silver-containing wastewater recovery, and in particular to a method for efficiently separating and recovering silver and dibutyl phthalate in silver-containing wastewater. Background Art

[0002] Silver is a metal element with the symbol Ag. It is ductile and has good thermal and electrical conductivity. It has a metallic luster and is soft. Its melting point is 961.93°C, boiling point is 2212°C, and density is 10.5g / cm3 (20°C). The main uses of silver are based on three pillars: industry, photography, and jewelry silverware.

[0003] Dibutyl phthalate (DBP) is a colorless, oily liquid that is flammable and has an aromatic odor. Studies have shown that DBP is metabolized slowly in organisms and easily accumulates in organisms such as fish and shellfish. This may cause problems such as toxicity and reproductive disorders, and have adverse effects on aquatic organisms. DBP can enter the soil and water bodies through the soil and groundwater layers, causing pollution to the soil ecosystem and the water ecosystem. Long-term exposure to high concentrations of DBP may have an inhibitory effect on soil bacteria and microorganisms in groundwater. Environmental hormones are an important type of environmental pollutant problem, which are easily accumulated in the water environment and cause serious harm to aquatic organisms.

[0004] The method for determining the chloride ion content in zinc-containing materials is to dissolve the sample in dilute nitric acid, add an excess of silver nitrate solution to convert the chloride ions into silver chloride precipitates, wrap the precipitates with dibutyl phthalate, use ammonium ferric sulfate as an indicator, and titrate the excess silver nitrate with potassium thiocyanate standard solution to determine the chloride ions in the sample. The purpose of adding dibutyl phthalate is because the solubility products of silver thiocyanate and silver chloride at 25°C are 1.8×10 -10 , 1.0×10 -12 The solubility of silver thiocyanate is less than that of silver chloride. Therefore, when the remaining silver nitrate is titrated back with potassium thiocyanate standard solution to reach the equivalent point, a slightly excess of SCN - It may react with silver chloride to convert it into AgSCN, consuming more standard solution, resulting in a large difference between the titration endpoint and the equivalent point. For this reason, dibutyl phthalate is added to wrap the silver chloride precipitation before titration, which does not contact the titrant, thereby ensuring that the titration endpoint is equivalent to the equivalent point. In the process of determining the chloride ion content in the sample, many silver-containing precipitations wrapped by dibutyl phthalate will be produced. These silver-containing precipitations will be discharged into the collection pool together with the experimental waste liquid most of the time, which not only causes the difficulty of experimental waste liquid treatment, the depletion of precious metal resources, and the increase of recovery cost, but also is not conducive to environmental protection.

[0005] In the related technology "Recovering Silver and Dibutyl Phthalate from Silver-Containing Waste Liquid", the method is to recover the silver-containing waste liquid after the experiment of determining the chloride ion content in compound fertilizers. This method is only applicable to solutions with simple components and can be realized by simple treatment and filtration. It is not applicable to acidic silver-containing waste liquid containing a large amount of metal ions. Because zinc-containing materials contain metal elements such as zinc, lead, iron, manganese, indium, tin, and bismuth, after being dissolved in dilute nitric acid, the chloride ions in the sample are determined, and the experimental waste liquid produced contains a large amount of metal ions and some insolubles. During the experiment, when the silver chloride precipitate is wrapped with dibutyl phthalate, some metal ions and insolubles will be entrained. Using the above-mentioned related technology, it is impossible to separate the entrained metal ions and insolubles, the recovered silver has low purity, and some silver chloride will adhere to the surface of dibutyl phthalate, and it is impossible to achieve complete separation of dibutyl phthalate and silver.

[0006] Therefore, it is necessary to provide a method for efficiently separating metal ions, silver and dibutyl phthalate in experimental waste liquid generated by detecting chloride ion content in zinc-containing materials, as well as a method for recovering silver and dibutyl phthalate. Summary of the invention

[0007] In order to solve or partially solve the problems existing in the related art, the present application provides a method for efficiently separating and recovering silver and dibutyl phthalate in silver-containing waste liquid, which can achieve efficient separation of a large amount of metal ions, silver and dibutyl phthalate in experimental waste liquid generated by detecting chloride ion content in zinc-containing materials, and recovery of silver and dibutyl phthalate.

[0008] The present application provides a highly efficient separation method for silver and dibutyl phthalate in silver-containing waste liquid, wherein chloride, nitric acid and water are mixed to prepare a separation agent; the separation agent is prepared in the following proportions by weight: 15-20 parts of chloride, 5-10 parts of nitric acid and 70-80 parts of water, wherein the chloride comprises sodium chloride, potassium chloride or ammonium chloride.

[0009] Optionally, include the following steps:

[0010] The silver-containing waste liquid is subjected to liquid-solid separation to obtain a filtrate and a silver-containing precipitate; the separating agent in claim 1 is added to the silver-containing precipitate for separation to obtain a silver precipitate, an organic phase and an aqueous phase; ammonia water is added to the silver precipitate for leaching, and suction filtration is performed to obtain [Ag(NH3)2] + Solutions and leaching residues.

[0011] Optionally, during separation, the separation temperature is 40-80° C., the stirring speed is 60-90 rpm, and the separation time is 30-60 min.

[0012] Optionally, the mass concentration of the ammonia water is 26%-28%.

[0013] Optionally, the leaching temperature is 50-100°C, the stirring speed is 60-90rpm, and the leaching time is 10-30min.

[0014] The present application also provides a method for recovering silver and dibutyl phthalate from silver-containing waste liquid, comprising the following steps:

[0015] S1, [Ag(NH3)2] obtained in claim 2 + A reducing agent is added to the solution for reduction to obtain sponge silver;

[0016] S2, adding alkaline substances to the organic phase obtained in claim 2 to adjust the pH, stirring and standing to separate the organic phase and the aqueous phase, and washing the organic phase with acid, alkali and water to obtain regenerated dibutyl phthalate;

[0017] S3, the sponge silver is washed and smelted to obtain metallic silver.

[0018] Optionally, the reducing agent in step S1 includes hydrated hydrazine, glucose or formaldehyde; the reduction time in step S1 is 20-40 minutes, and the reduction temperature is 40-80°C.

[0019] Optionally, the alkaline substance in step S2 is sodium hydroxide, sodium carbonate or liquid alkali, and the pH is adjusted to 13-14. The adding method includes dissolving the sodium hydroxide or sodium carbonate and adding it in liquid form, or directly adding the solid to mix the filtrate and the alkali evenly.

[0020] Optionally, the pickling in step S2 uses 1%-5% dilute nitric acid, and the washing time is 2-5 minutes;

[0021] Alkaline washing uses 1%-5% alkaline solution, the alkaline solution includes liquid alkali, sodium hydroxide or sodium carbonate solution, and the washing time is 2-5 minutes;

[0022] The washing process uses secondary deionized water, and the washing time is 2-5 minutes.

[0023] Optionally, the smelting temperature in step S3 is 980-1100°C.

[0024] Dibutyl phthalate encapsulation principle: Dibutyl phthalate encapsulates silver chloride precipitate mainly through electrostatic adsorption, van der Waals force and steric hindrance effect.

[0025] Dibutyl phthalate separation principle:

[0026] 1) Ion exchange and competitive adsorption: Chloride ions (Cl - ) can exchange ions with cations that may be adsorbed on the surface of the coating (such as cations adsorbed on dibutyl phthalate by electrostatic adsorption). At the same time, the presence of a large amount of chloride ions will react with the silver ions (Ag+ ) forms a dissolution equilibrium ( According to Le Chatelier's principle, when the chloride ion concentration in the solution increases, the equilibrium will shift toward the dissolution of silver chloride, which helps to break the interaction between the precipitate surface and dibutyl phthalate formed by the adsorption of ions on the precipitate surface.

[0027] 2) Protonation and destruction of interactions: Hydrogen ions (H + ) can react with functional groups such as the ester group in the dibutyl phthalate molecule. The ester group may be protonated under acidic conditions. For example, the ester group (-COO-C4H9) in the dibutyl phthalate molecule may combine with hydrogen ions to form -COOH + -C4H9. This protonation changes the charge distribution and chemical properties of the dibutyl phthalate molecule, thereby weakening the electrostatic adsorption and van der Waals interactions between it and the silver chloride precipitate. At the same time, the stability and adsorption properties of the protonated molecule in the solution will also change, which is conducive to its detachment from the surface of the silver chloride precipitate.

[0028] 3) Dissolution and dispersion: The combined action of chloride and nitric acid gradually destroys the coating layer on the surface of the silver chloride precipitate, and the silver chloride precipitate will also dissolve to a certain extent. With the destruction of the coating layer, the silver chloride precipitate particles will gradually disperse in the solution, further reducing the degree of coating of dibutyl phthalate.

[0029] In summary, the present invention separates dibutyl phthalate from silver chloride by using a prepared separation agent, and the metal ions carried by the dibutyl phthalate enter the aqueous phase.

[0030] The technical solution provided by this application may have the following beneficial effects:

[0031] 1) The separation agent prepared in the present application can separate silver and dibutyl phthalate under heating. When silver and dibutyl phthalate are completely separated, the entrained metal impurities enter the water phase, thereby realizing the recovery of precious metal silver in the silver-containing waste liquid.

[0032] 2) In the related art, due to the lack of hydrogen ions (H + ), it is impossible to weaken the electrostatic adsorption and van der Waals force between dibutyl phthalate and silver chloride precipitation, and it is impossible to achieve complete separation of dibutyl phthalate and silver. In this application, a separating agent and an alkaline substance are added to separate dibutyl phthalate from silver chloride. + -H of C4H9 + With OH -The reaction generates H2O and -COO-C4H9, so that the charge distribution and chemical properties of the dibutyl phthalate molecule remain unchanged, thereby achieving regeneration. The regenerated dibutyl phthalate can replace analytically pure dibutyl phthalate and be used again for the detection of chloride ions.

[0033] It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The above and other objects, features and advantages of the present application will become more apparent through a more detailed description of exemplary embodiments of the present application in conjunction with the accompanying drawings, wherein the same reference numerals generally represent the same components in the exemplary embodiments of the present application.

[0035] Figure 1 The present invention is a flow chart of a method for efficiently separating and recovering silver and dibutyl phthalate from silver-containing waste liquid. DETAILED DESCRIPTION

[0036] The embodiments of the present application will be described in more detail below with reference to the accompanying drawings. Although the embodiments of the present application are shown in the accompanying drawings, it should be understood that the present application can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to make the present application more thorough and complete, and to fully convey the scope of the present application to those skilled in the art.

[0037] Example 1

[0038] S1, mixing sodium chloride, nitric acid and water in a certain proportion to prepare a separating agent, which includes 15 parts of sodium chloride, 5 parts of nitric acid and 80 parts of water by weight;

[0039] S2, separating the collected laboratory silver-containing waste liquid into liquid and solid to obtain a filtrate and a silver-containing precipitate, and the filtrate is collected and sent to water treatment;

[0040] S3, adding a separating agent to the silver-containing precipitate for heating and separation to obtain a silver precipitate, an organic phase and an aqueous phase. The liquid-to-solid ratio (L / S) is 1:1, the separation temperature is 70°C, the stirring speed is 70 rpm, and the separation time is 35 min;

[0041] The silver precipitate is silver chloride precipitate, the organic phase is dibutyl phthalate, and the aqueous phase contains a large amount of metal ions.

[0042] S4, ammonia water with a mass concentration of 26% and water in a volume ratio of 4:1 are mixed and added to the silver precipitate obtained in S3 for leaching, and then filtered to obtain [Ag(NH3)2] +solution and leaching residue, wherein the liquid-to-solid ratio (L / S) is 6:1, the leaching temperature is controlled at 60°C, the stirring speed is 70rpm, and the leaching time is 20min;

[0043] S5, to [Ag(NH3)2] + Hydrazine hydrate is added to the solution for reduction to obtain sponge silver, wherein the molar ratio of hydrazine hydrate to the amount of silver and other substances is 1:4, the reduction temperature is controlled to be 60° C., and the reduction time is 20 min;

[0044] S6, adding sodium hydroxide to the organic phase obtained in S3 to adjust the pH to 12, stirring and standing to separate the organic phase and the aqueous phase, collecting the aqueous phase and sending it to water treatment, washing the organic phase with 1% nitric acid solution for 2 minutes, 1% sodium hydroxide solution for 2 minutes, and pure water for 2 minutes to obtain regenerated dibutyl phthalate;

[0045] S7, the sponge silver is washed and smelted to obtain metallic silver, wherein the sponge silver is repeatedly washed with water until the pH value is 7, and the smelting temperature is 990° C. after the water is dried.

[0046] During the implementation process, the silver-containing precipitate (dry weight) was 105 g, containing 54.8% silver, [Ag(NH3)2] + The solution volume is 480 ml, containing 118.67 g / l of silver, the leached residue (dry weight) is 9.8 g, containing 5.87% of silver; the liquid volume after sponge silver reduction is 490 ml, containing 0.12 g / l of silver; the metallic silver product is 57.14 g, and the total amount of other metal impurities in the metallic silver is 0.00424% as detected by inductively coupled plasma emission spectroscopy, and the silver recovery rate is 98.89%. The chloride ion contents in the samples of analytically pure dibutyl phthalate and regenerated dibutyl phthalate are 7.18% and 7.22% respectively, and the results are consistent. The problem of efficient recovery of precious metal silver in laboratory silver-containing waste liquid and regeneration of dibutyl phthalate is solved, and the problem of replacing analytically pure dibutyl phthalate for the detection of chloride ions is solved.

[0047] Example 2

[0048] S1, potassium chloride, nitric acid and water are mixed in a certain proportion to prepare a separating agent, which includes 17 parts of potassium chloride, 8 parts of nitric acid and 75 parts of water by weight;

[0049] S2, performing liquid-solid separation on the collected laboratory silver-containing waste liquid to obtain a filtrate and a silver-containing precipitate, and the filtrate is collected and sent to water treatment;

[0050] S3, adding a separating agent to the silver-containing precipitate for heating and separation to obtain a silver precipitate, an organic phase and an aqueous phase. The liquid-to-solid ratio (L / S) is 2:1, the separation temperature is 60° C., the stirring speed is 80 rpm, and the separation time is 40 min;

[0051] The silver precipitate is silver chloride precipitate, the organic phase is dibutyl phthalate, and the aqueous phase contains a large amount of metal ions.

[0052] S4, ammonia water with a mass concentration of 27% and water in a volume ratio of 3:1 are mixed and added to the silver precipitate obtained in S3 for leaching, and then filtered to obtain [Ag(NH3)2] + solution and leaching residue, wherein the liquid-to-solid ratio (L / S) is 5:1, the leaching temperature is controlled at 70°C, the stirring speed is 80rpm, and the leaching time is 25min;

[0053] S5, to [Ag(NH3)2] + Formaldehyde is added to the solution for reduction to obtain sponge silver, wherein the molar ratio of formaldehyde to the amount of silver and other substances is 1:4, the reduction temperature is controlled to be 70° C., and the reduction time is 30 min;

[0054] S6, adding sodium carbonate to the organic phase obtained in S3 to adjust the pH to 13, stirring and standing to separate the organic phase and the aqueous phase, collecting the aqueous phase and sending it to water treatment, washing the organic phase with 2% nitric acid solution for 2 minutes, 2% sodium carbonate solution for 2 minutes, and pure water for 2 minutes to obtain regenerated dibutyl phthalate;

[0055] S7, the sponge silver is washed and smelted to obtain metallic silver, wherein the sponge silver is repeatedly washed with water until the pH value is 6, and the smelting temperature is 1000° C. after the water is dried.

[0056] During the implementation process, the silver-containing precipitate (dry weight) was 85 g, containing 50.28% silver, [Ag(NH3)2] + The solution volume is 300 ml, containing 141 g / l of silver, the leached residue (dry weight) is 7.2 g, containing 5.70% of silver; the liquid volume after sponge silver reduction is 310 ml, containing 0.0687 g / l of silver; the total amount of other metal impurities in the metallic silver is 0.0049% detected by inductively coupled plasma emission spectroscopy, the metallic silver product is 42.50 g, and the silver recovery rate is 98.94%. The chloride ion contents in the samples of analytically pure dibutyl phthalate and regenerated dibutyl phthalate are 3.58% and 3.54% respectively, and the results are consistent. The problem of efficient recovery of precious metal silver in laboratory silver-containing waste liquid and regeneration of dibutyl phthalate is solved, and the problem of replacing analytically pure dibutyl phthalate for the detection of chloride ions is solved.

[0057] Example 3

[0058] S1, taking ammonium chloride, nitric acid and water and mixing them in a certain proportion to prepare a separating agent, which includes 20 parts of ammonium chloride, 10 parts of nitric acid and 70 parts of water by weight;

[0059] S2, separating the collected laboratory silver-containing waste liquid into liquid and solid to obtain a filtrate and a silver-containing precipitate, and the filtrate is collected and sent to water treatment;

[0060] S3, adding a separating agent to the silver-containing precipitate for heating and separation to obtain a silver precipitate, an organic phase and an aqueous phase. The liquid-to-solid ratio (L / S) is 3:1, the separation temperature is 70°C, the stirring speed is 75 rpm, and the separation time is 50 min;

[0061] The silver precipitate is silver chloride precipitate, the organic phase is dibutyl phthalate, and the aqueous phase contains a large amount of metal ions.

[0062] S4, ammonia water with a mass concentration of 28% and water in a volume ratio of 2:1 are mixed and added to the silver precipitate obtained in S3 for leaching, and then filtered to obtain [Ag(NH3)2] + solution and leaching residue, wherein the liquid-to-solid ratio (L / S) is 4:1, the leaching temperature is controlled at 80°C, the stirring speed is 90rpm, and the leaching time is 30min;

[0063] S5, to [Ag(NH3)2] + Glucose is added to the solution for reduction to obtain sponge silver, wherein the molar ratio of the amount of hydrated hydrazine to the amount of silver and other substances is 1:2, the reduction temperature is controlled to be 75°C, and the reduction time is 40 minutes;

[0064] S6, adding liquid alkali to the organic phase obtained in S3 to adjust the pH to 14, stirring and standing to separate the organic phase and the aqueous phase, collecting the aqueous phase and sending it to water treatment, washing the organic phase with 3% nitric acid solution for 2 minutes, 3% liquid alkali solution for 2 minutes, and pure water for 2 minutes to obtain regenerated dibutyl phthalate;

[0065] S7, the sponge silver is washed and smelted to obtain metallic silver, wherein the sponge silver is repeatedly washed with water until the pH value is 6.5, and the smelting temperature is 1050° C. after the water is dried.

[0066] During the implementation process, the silver-containing precipitate (dry weight) was 92g, containing 49.58% silver, [Ag(NH3)2] +The solution volume is 280 ml, containing 161.25 g / l of silver, the leached residue (dry weight) is 8.5 g, containing 5.36% of silver; the liquid volume after sponge silver reduction is 290 ml, containing 0.207 g / l of silver; the total amount of other metal impurities in the metallic silver is 0.00461% detected by inductively coupled plasma emission spectroscopy, the metallic silver product is 45.30 g, and the silver recovery rate is 98.86%. The chloride ion contents in the samples of analytically pure dibutyl phthalate and regenerated dibutyl phthalate are 5.73% and 5.80% respectively, and the results are consistent. The problem of efficient recovery of precious metal silver in laboratory silver-containing waste liquid and regeneration of dibutyl phthalate is solved, and the problem of replacing analytically pure dibutyl phthalate for the detection of chloride ions is solved.

[0067] Comparative Example 1

[0068] The difference between Comparative Example 1 and Example 1 is that in step 1) of Comparative Example 1, sodium chloride is replaced by chlorides in the following table, and other conditions remain unchanged. The experimental results are shown in Table 1.

[0069] Table 1 Experimental results of comparative example 1

[0070]

[0071] As shown in Table 1, when chlorides such as calcium and iron that can generate precipitation with ammonia are used as separating agent components, their precipitation will adsorb silver ions, resulting in a lower recovery rate than the embodiment, and the silver impurity content recovered is higher than the embodiment; when chlorides such as zinc and copper that can complex with ammonia are used as separating agents, zinc and copper ions can be reduced, and the silver product recovered has a high impurity content, and the recovery cost is higher than the embodiment; although other alkali metal chlorides (such as cesium chloride, rubidium chloride, etc.) can achieve the separation and recovery of silver and dibutyl phthalate, the recovery cost is high. Therefore, considering the recovery rate, purity and recovery cost of silver, sodium chloride, potassium chloride or ammonium chloride is used as a separating agent in this application.

[0072] Comparative Example 2

[0073] The difference between Comparative Example 2 and Example 1 is that in step 1) of Comparative Example 2, the separation agent ratio is replaced with 10 parts of chloride or 30 parts of chloride, and other conditions remain unchanged. The experimental results are shown in Table 2.

[0074] Table 2 Experimental results of comparative example 2

[0075]

[0076] As shown in Table 2, 10 parts of chlorides are used as the separating agent component, because its chloride ion concentration is not enough, the separation effect of silver and dibutyl phthalate is not good, and the recovery rate is lower than that of the embodiment; 30 parts of chlorides are used as the separating agent component, although the chloride ion concentration is sufficient, the separation effect of silver and dibutyl phthalate is good, but the recovery cost is higher than that of the embodiment, and similarly, the effect of replacing the nitric acid ratio is also the same. Therefore, considering the separation effect and recovery cost of silver and dibutyl phthalate, 15-20 parts of chlorides, 5-10 parts of nitric acid, and 70-80 parts of water are used as the separating agent component in this application.

[0077] The embodiments of the present application have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The selection of terms used herein is intended to best explain the principles of the embodiments, practical applications, or improvements to the technology in the market, or to enable other persons of ordinary skill in the art to understand the embodiments disclosed herein.

Claims

1. An efficient separation method for silver and dibutyl phthalate in silver-containing waste liquid, characterized in that: The separation agent is prepared by mixing chloride, nitric acid and water; the separation agent is prepared in the following proportions: 15-20 parts of chloride, 5-10 parts of nitric acid and 70-80 parts of water by weight; the chloride includes sodium chloride, potassium chloride or ammonium chloride.

2. The efficient separation method according to claim 1, characterized in that: The following steps are involved: The silver-containing waste liquid is subjected to liquid-solid separation to obtain a filtrate and a silver-containing precipitate; the separating agent described in claim 1 is added to the silver-containing precipitate for separation to obtain a silver precipitate, an organic phase and an aqueous phase; ammonia water is added to the silver precipitate for leaching, and suction filtration is performed to obtain [Ag(NH3)2] + Solutions and leaching residues.

3. The efficient separation method according to claim 2, characterized in that: In the separation, the separation temperature is 40-80° C., the stirring speed is 60-90 rpm, and the separation time is 30-60 min.

4. The method according to claim 2, characterized in that: The mass concentration of the ammonia water is 26%-28%.

5. The method according to claim 2, characterized in that: The leaching temperature is 50-100°C, the stirring speed is 60-90rpm, and the leaching time is 10-30min.

6. A method for recovering silver and dibutyl phthalate from silver-containing waste liquid, characterized in that: The following steps are involved: S1, [Ag(NH3)2] obtained in claim 2 + A reducing agent is added to the solution for reduction to obtain sponge silver; S2, adding alkaline substances to the organic phase obtained in claim 2 to adjust the pH, stirring and standing to separate the organic phase and the aqueous phase, and washing the organic phase with acid, alkali and water to obtain regenerated dibutyl phthalate; S3, the sponge silver is washed and smelted to obtain metallic silver.

7. The recycling method according to claim 6, characterized in that: The reducing agent in step S1 includes hydrated hydrazine, glucose or formaldehyde; the reduction time in step S1 is 20-40 minutes, and the reduction temperature is 40-80°C.

8. The recycling method according to claim 6, characterized in that: In step S2, the alkaline substance is sodium hydroxide, sodium carbonate or liquid alkali, and the pH is adjusted to 12-14. The adding method includes dissolving sodium hydroxide or sodium carbonate and adding it in liquid form, or directly adding solid to mix the organic phase and the alkali evenly.

9. The recycling method according to claim 6, characterized in that: In step S2, the pickling is performed using 1%-5% dilute nitric acid for 2-5 minutes; Alkaline washing uses 1%-5% alkaline solution, the alkaline solution includes liquid alkali, sodium hydroxide or sodium carbonate solution, and the washing time is 2-5 minutes; The washing process uses secondary deionized water, and the washing time is 2-5 minutes.

10. The recycling method according to claim 6, characterized in that: The smelting temperature in step S3 is 980-1100°C.

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