Precious metal recovery method
By leaching with nitric acid, removing impurities with water, filtering and washing with water, and alkali precipitation to form silver oxide, silver can be directly smelted to form elemental silver. This solves the problem of high energy consumption in electrolytic refining in existing technologies and achieves low-energy and low-cost silver recovery.
Patent Information
- Application Number
- CN202511787732.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-01
- Publication Date
- 2026-01-23
AI Technical Summary
Existing silver recovery methods, particularly electrolytic refining, consume a lot of energy, resulting in high production costs.
By using nitric acid leaching, water purification, filtration and washing, alkali precipitation, and smelting and casting ingots, silver oxide is generated and can be directly smelted to form elemental silver without electrolytic refining.
It reduces energy consumption during recycling, lowers production costs, and increases the yield and purity of precious metals.
Smart Images
Figure CN121380583A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the technical field of metal recovery, and particularly relates to a precious metal recovery method. BACKGROUND
[0002] In the production process of silver-gallium-copper alloy target material, silver-indium alloy target material, silver-palladium-copper-germanium alloy target material and silver-palladium-copper alloy target material, scraps, risers, sawing wastes and the like are generated, and if discarded directly, a large amount of precious metal is wasted, so the wastes are usually recovered.
[0003] At present, the silver recovery method in China is usually a fire method and a wet method. The fire method is to smelt the wastes directly to obtain crude silver, and then the crude silver is refined by electrolysis to obtain silver powder. The wet method is to dissolve the wastes by using nitric acid as a leaching agent to form a silver ion solution, then remove impurities by adding lye to the silver ion solution, and then electrolyze the silver ion solution after the impurities are removed. In the current recovery method, the energy consumption of electrolytic refining is high, resulting in high production cost. SUMMARY
[0004] The technical problem to be solved by the application is that the energy consumption of electrolytic refining is high in the existing silver recovery method, resulting in high production cost. To solve the technical problem, a precious metal recovery method with low energy consumption is provided.
[0005] The technical scheme provided by the application is as follows: A precious metal recovery method, comprising: S110, nitric acid leaching: dissolving silver-containing wastes in a nitric acid solution; S120, hydrolysis and impurity removal: adding sodium hydroxide solution dropwise to the dissolved solution to obtain impurity precipitate and silver nitrate solution; S130, filtration and water washing: separating the impurity precipitate from the silver nitrate solution, and water washing the impurity precipitate, and the washing water enters the silver nitrate solution; S140, alkali precipitation: adding sodium hydroxide solution dropwise to the silver nitrate solution to form silver oxide precipitate; S160, smelting and ingot casting: smelting the silver oxide to form silver single element, and casting the silver single element into an ingot.
[0006] By using the above precious metal recovery method, after metal leaching is completed, metal impurities are removed by hydrolysis, then silver oxide is formed by alkali precipitation, after the silver oxide is washed and dried, the silver oxide is smelted to form silver single element, and then the silver single element is cast into silver ingots or anodes meeting the electrolysis requirements. Since the precious metal recovery method forms silver oxide, and then smelts the silver oxide to form silver single element, electrolytic refining is not needed, the energy consumption of recovery is reduced, and the production cost is low.
[0007] Further, step S110 comprises: S111, adding the waste material into a reaction kettle; S112, adding pure water and nitric acid into the reaction kettle; S113, heating the reaction kettle.
[0008] Further, in step S112, the waste material: nitric acid: pure water = 1 kg: 1 L: 3 L.
[0009] Further, step S120 comprises: S121, adding a 20% sodium hydroxide solution dropwise into the dissolved solution, while stirring and heating the solution for 1-1.5 h until the solution pH = 5-6; S122, stopping the stirring and continuing to heat the solution for 1-1.5 h.
[0010] Further, in steps S121 and S122, the solution heating temperature is 80-90°C.
[0011] Further, in step S140, a 20% sodium hydroxide solution is added dropwise.
[0012] Further, in step S140, the solution pH is controlled to be 8-10.
[0013] Further, step S160 comprises: S161, adding silver oxide into a medium frequency furnace in multiple times when the medium frequency furnace temperature is 200-300°C; S162, heating the medium frequency furnace to 500-600°C to convert the silver oxide into silver single element; S163, continuing to heat to 1000-1100°C to melt the silver single element; S164, casting the silver single element into ingots through a mold.
[0014] Further, between step S140 and step S160, there is also a step: S150, washing and drying: washing and drying the silver oxide.
[0015] Further, in steps S130 and S150, the washing is stopped when the conductivity of the washing water is <100 μs / cm. In step S150, the drying temperature of the silver oxide is 180°C, and the drying time is 1-1.5 h.
[0016] In summary, the precious metal recovery method provided by the present application has at least one of the following advantages: 1. After generating silver oxide, the silver oxide is smelted and cast into ingots, without the need for electrolytic refining, lower energy consumption, and lower production cost; 2. The precious metal recovery method provided by the application has high yield and high purity of recovered precious metal. BRIEF DESCRIPTION OF DRAWINGS
[0017] The accompanying drawings are included to provide a further understanding of the application, and are incorporated in and constitute a part of the specification, illustrate embodiments of the application, and together with the description serve to explain the application, but are not intended to limit the application.
[0018] Figure 1 A flow chart of the precious metal recovery method provided by an embodiment of the application. DETAILED DESCRIPTION
[0019] In order to make the above objectives, features and advantages of the application more apparent, specific embodiments of the application are described in detail below with reference to the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the application. However, the application can be practiced in a variety of ways other than those described herein, and skilled persons in the art can make similar improvements without departing from the spirit of the application, so the application is not limited to the specific embodiments disclosed below.
[0020] As shown in Figure 1 An embodiment of the application provides a precious metal recovery method, which comprises the following steps: S110, nitric acid leaching: dissolving silver-containing waste in a nitric acid solution.
[0021] S120, hydrolysis and impurity removal: adding sodium hydroxide solution dropwise to the dissolved solution to obtain impurity precipitate and silver nitrate solution.
[0022] S130, filtration and water washing: separating the impurity precipitate from the silver nitrate solution, and water washing the impurity precipitate, with the washing water entering the silver nitrate solution.
[0023] S140, alkali precipitation: adding sodium hydroxide solution dropwise to the silver nitrate solution to form silver oxide precipitate.
[0024] S150, washing and drying: filtering out the silver oxide and water washing and drying the silver oxide.
[0025] S160, smelting and ingot casting: smelting the silver oxide to form silver single element, and casting the silver single element into an ingot.
[0026] In other words, the waste material is first leached by a nitric acid solution to form a metal ion solution; then, a sodium hydroxide solution is added dropwise into the dissolved metal ion solution, and by controlling the pH, other metal impurities (e.g., one or more of copper, gallium, indium, palladium, germanium) are precipitated, and after filtration, a silver nitrate solution is obtained. Next, the sodium hydroxide solution is continuously added dropwise into the silver nitrate solution to generate a silver oxide precipitate. After the silver oxide precipitate is filtered out, the silver oxide is washed with water and dried, and then smelting is performed to convert the silver oxide into silver single substance and melt it, and finally, the silver single substance is cast into ingots.
[0027] By using the above-mentioned precious metal recovery method, after the metal leaching is completed, the metal impurities are removed by hydrolysis, and then the silver oxide is formed by alkaline precipitation. After the silver oxide is washed and dried, the silver oxide is smelted to form silver single substance, and then the silver single substance is cast into silver ingots or anodes that meet the electrolysis requirements. Since the precious metal recovery method forms silver oxide and then smelts the silver oxide to form silver single substance, it does not need to use electrolytic refining, thereby reducing the energy consumption of recovery and lowering the production cost.
[0028] It should be noted that the above-mentioned waste material is one or more of silver-gallium-copper alloy target material, silver-indium alloy target material, silver-palladium-copper-germanium alloy target material, and silver-palladium-copper alloy target material. In addition, in the case of low purity recovery requirements, after the silver oxide precipitate is formed, the silver oxide can be directly filtered out and smelted to form ingots.
[0029] The steps of the precious metal recovery method are described below.
[0030] S110 includes the following steps: S111, the waste material is added to the reaction kettle. For filamentous waste material or small block-shaped waste material, it can be directly put into the reaction kettle. For large block-shaped waste material, it needs to be cut into small pieces first, and then put into the reaction kettle.
[0031] S112, pure water and nitric acid are added to the reaction kettle. The ratio of waste material: nitric acid: pure water is 1 kg: 1 L: 3 L, so as to ensure sufficient reaction while avoiding waste of nitric acid. After the material is added, step S113 is performed.
[0032] S113, the reaction kettle is heated to ensure that the metal is dissolved. Specifically, the heating temperature is 80-90℃, and during the heating process, the stirring leaching is performed at a speed of 1-3 r / s, and the leaching time is 3-4 h. Alternatively, the heating temperature can be any temperature in 80℃, 81℃, 82℃, 83℃, 84℃, 85℃, 86℃, 87℃, 88℃, 89℃, 90℃ or between any two temperatures; the speed can be 1 r / s, 2 r / s, 3 r / s. After the leaching is completed, step S114 is performed.
[0033] S114, cooling the dissolved solution. The cooling method can be natural cooling or cooling through the jacket of the reactor outer wall. After cooling, step S120 is entered.
[0034] S120 includes the following steps: S121, adding a 20% sodium hydroxide solution dropwise to the dissolved solution, while stirring and heating the solution for 1-1.5h until the solution pH=5-6; S122, stopping stirring and continuing to heat the solution for 1-1.5h to ensure the hydrolysis reaction is complete, obtaining impurity precipitate and silver nitrate solution. In steps S121 and S122, the heating temperature is 80-90 degrees Celsius, which can be any temperature in the range of 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90 degrees Celsius or between any two temperatures. In addition, it can be determined that after heating is complete, the solution needs to be cooled after standing, and then step S130 is entered.
[0035] In S130, the impurity precipitate is first separated from the silver nitrate solution, and then the impurity is washed with water until the conductivity of the washing water is <100 μs / cm, and the water washing is stopped. The washing water produced by water washing is added to the silver nitrate solution to recover as much silver as possible and improve the yield. After water washing is complete, step S140 is entered.
[0036] In S140, a 20% sodium hydroxide solution is added dropwise until no brown-black silver oxide precipitate appears. In the preferred embodiment, after the silver oxide precipitate is complete, the solution pH=8-10, if the pH is too high, the concentration of hydroxyl ions will increase, causing silver to dissolve in the solution, resulting in a decrease in silver yield. In addition, in order to avoid waste of sodium hydroxide, when configuring the sodium hydroxide solution, the amount of sodium hydroxide used = silver content * 0.37 * 1.02 eq ~ silver content * 0.37 * 1.04 eq.
[0037] It needs to be explained that the silver content in the waste is known, and after leaching, hydrolysis and water washing, the silver content will not change much, so the amount of sodium hydroxide can still be calculated according to the silver content in the waste.
[0038] After the silver oxide precipitate is complete, step S150 is entered.
[0039] In S150, the silver oxide is first filtered out, and then washed with water until the conductivity of the washing water is <100 μs / cm, and the water washing is stopped to improve the purity of the silver obtained by subsequent smelting. After water washing is complete, the washing water is treated as industrial wastewater, and the silver oxide is placed in a drying box to dry at a temperature of 180°C for 1h. After drying is complete, step S160 is performed.
[0040] S160 includes steps of: S161, when the intermediate frequency furnace temperature is 200-300℃, the silver oxide is put into the intermediate frequency furnace for multiple times to remove water vapor at the temperature as much as possible; S162, the intermediate frequency furnace is heated to 500-600℃, so that the silver oxide is converted into silver single element; S163, the temperature is continuously increased to 1000-1100℃, so that the silver single element is melted; and S164, the silver single element is cast into ingot through a mold. Before the silver single element is introduced into the mold, the mold can be preheated at 200℃ for 2h.
[0041] In order to embody the advantages of the above process parameters, the following examples are provided for proof.
[0042] Example 1 25kg silver-indium alloy is put into a reaction kettle, and then nitric acid and pure water are added according to the ratio of waste material∶nitric acid∶pure water=1kg∶1L∶3L, heated to 85℃, and stirring is started at a speed of 2r / s. After 4h of heating and stirring, the stirring is stopped, and the solution is cooled. After cooling, a 20% sodium hydroxide solution is added to the solution for hydrolysis reaction, and the solution is heated to 85℃ while stirring, the pH of the solution is adjusted to 6, the stirring is stopped, but the heating temperature is maintained for 1h for aging to make the hydrolysis reaction sufficient. After the hydrolysis reaction is completed, the heating is stopped and the solution is cooled, to obtain a silver nitrate solution and a metal impurity precipitate. The silver nitrate solution and the metal impurity precipitate are filtered, and the precipitate is washed with water, and the washing water is added to the silver nitrate solution. The water washing is stopped when the conductivity of the washing water is <100μs / cm, to obtain a silver nitrate solution with a mass concentration of >10%. Next, sodium hydroxide is added dropwise to the silver nitrate solution at room temperature until no brown-black silver oxide precipitate is generated, at which time the pH of the solution is 8. The silver oxide is filtered out, and then the silver oxide is washed with water until the conductivity of the washing water is <100μs / cm, and then the silver oxide is placed in a drying oven for drying at a drying temperature of 180℃ for 1h. The above steps are performed twice before smelting. The obtained silver oxide is put into an intermediate frequency furnace for 3 times, 15-20kg each time, and the temperature is 250℃ during the feeding process. After the feeding is completed, the temperature is increased to 600℃, so that the silver oxide is converted into silver single element, and then the temperature is continuously increased to 1100℃, so that the silver single element is melted. Finally, the melted silver single element is introduced into a mold preheated at 200℃ for 2h to complete the ingot casting.
[0043] Example 2 41 kg of silver-indium alloy was put into a reaction kettle, and then nitric acid and pure water were added according to the ratio of waste material: nitric acid: pure water = 1 kg: 1 L: 3 L, heated to 85°C, and stirring was started at a speed of 2 r / s. After 4 h of heating and stirring, it was stopped and allowed to cool. After cooling, a 20% mass concentration sodium hydroxide solution was added to the solution to perform a hydrolysis reaction, and stirring was performed while heating to 85°C. The pH of the solution was adjusted to 5, and stirring was stopped, but the heating temperature was maintained for 1 h to allow aging, so that the hydrolysis reaction was sufficient. After the hydrolysis reaction was completed, the heating was stopped and allowed to cool, and a silver nitrate solution and a metal impurity precipitate were obtained. The silver nitrate solution and the metal impurity precipitate were filtered, and the precipitate was water washed, and the wash water was added to the silver nitrate solution. The water washing was stopped when the conductivity of the wash water was < 100 μs / cm, and a silver nitrate solution with a mass concentration of > 10% was obtained. Next, sodium hydroxide was added dropwise to the silver nitrate solution at room temperature until no brown-black silver oxide precipitate was formed, at which point the solution pH was 10. The silver oxide was filtered out, and then the silver oxide was water washed until the conductivity of the wash water was < 100 μs / cm, and then the silver oxide was placed in a drying oven and dried at a drying temperature of 180°C for 1 h. The above steps were performed twice before smelting. The obtained silver oxide was put into a medium frequency furnace in 4 times, 20-25 kg each time, and the temperature during the process was 250°C. After the feeding was completed, the temperature was raised to 600°C to convert the silver oxide into silver single element, and then the temperature was further raised to 1100°C to melt the silver single element. Finally, the melted silver single element was introduced into a mold preheated at 200°C for 2 h to complete the ingot casting.
[0044] Example 3 45 kg of silver-indium alloy was put into a reaction kettle, and then nitric acid and pure water were added in the ratio of waste material: nitric acid: pure water = 1 kg: 1 L: 3 L, heated to 85°C, and stirring was started at a rotation speed of 2 r / s. After 4 h of heating and stirring, the stirring was stopped, and the solution was allowed to cool. After the cooling was completed, a 20% by mass sodium hydroxide solution was added to the solution to perform a hydrolysis reaction, and the solution was stirred while being heated to 85°C. The pH of the solution was adjusted to 5, the stirring was stopped, but the heating temperature was maintained for 1 h to perform aging, so that the hydrolysis reaction was sufficiently performed. After the hydrolysis reaction was completed, the heating was stopped, and the solution was allowed to cool, so that a silver nitrate solution and a metal impurity precipitate were obtained. The silver nitrate solution and the metal impurity precipitate were filtered, and the precipitate was water-washed. The water used for the washing was added to the silver nitrate solution, and the water washing was stopped when the conductivity of the water was < 100 μs / cm, so that a silver nitrate solution having a mass concentration of > 10% was obtained. Next, sodium hydroxide was added dropwise to the silver nitrate solution at room temperature until no brownish black silver oxide precipitate was generated. At this time, the pH of the solution was 12. The silver oxide was filtered out, and then the silver oxide was water-washed until the conductivity of the water was < 100 μs / cm, and then the silver oxide was put into a drying oven and dried at a drying temperature of 180°C for 1 h. The above procedure was performed twice before smelting. The obtained silver oxide was put into a medium-frequency furnace in four times, 20-25 kg each time, and the temperature during the putting was 250°C. After the putting was completed, the temperature was raised to 600°C, so that the silver oxide was converted into silver single substance, and then the temperature was further raised to 1100°C, so that the silver single substance was melted. Finally, the melted silver single substance was introduced into a mold that was preheated at 200°C for 2 h, so that a silver ingot was completed.
[0045] Example 4 45kg silver-indium alloy is put into a reaction kettle, then nitric acid and pure water are added according to the ratio of waste material: nitric acid: pure water = 1kg: 1L: 3L, heated to 85℃, and stirring is started at a speed of 2r / s. After 4h of heating and stirring, the stirring is stopped, and the solution is cooled. After cooling, a 20% mass concentration sodium hydroxide solution is added to the solution to perform a hydrolysis reaction, and the solution is heated to 85℃ while stirring. The pH of the solution is adjusted to 5, the stirring is stopped, but the heating temperature is maintained for 1h to age, so that the hydrolysis reaction is sufficient. After the hydrolysis reaction is completed, the heating is stopped and the solution is cooled, obtaining a silver nitrate solution and a metal impurity precipitate. The silver nitrate solution and the metal impurity precipitate are filtered, and the precipitate is washed with water. The washing water is added to the silver nitrate solution, and the water washing is stopped when the conductivity of the washing water is <100μs / cm, obtaining a silver nitrate solution with a mass concentration of >10%. Next, sodium hydroxide is added dropwise to the silver nitrate solution at room temperature until no brown-black silver oxide precipitate is generated, at which time the pH of the solution is 14. The silver oxide is filtered out, and then the silver oxide is washed with water until the conductivity of the washing water is <100μs / cm. Then the silver oxide is placed in a drying oven and dried at a drying temperature of 180℃ for 1h. The above steps are performed twice before smelting. The obtained silver oxide is put into a medium-frequency furnace in 4 times, 20-25kg each time, and the temperature during the process is 250℃. After the feeding is completed, the temperature is raised to 600℃, so that the silver oxide is converted into silver single element, and then the temperature is continuously raised to 1100℃, and the silver single element is melted. Finally, the melted silver single element is introduced into a mold preheated at 200℃ for 2h to complete the ingot casting.
[0046] The relevant data of the above examples are shown in Table 1, and in Table 1, the batch is the number of silver oxide preparation in each example. It can be determined from Table 1 that, by using the precious metal recovery method provided in the present application and according to the process parameters in the above examples, the purity and yield of the recovered silver ingot can be ensured to be relatively high.
[0047] Table 1: Recovery data It should be explained that, in step S150, the silver oxide is dried to remove most of the water in the silver oxide, but not all the water is dried to avoid splashing of the silver oxide in the subsequent smelting process. Therefore, the weight of the silver oxide in the data in Table 1 still has a small amount of water.
[0048] In summary, the precious metal recovery method provided in the present application has at least one of the following advantages: 1. By generating silver oxide and then smelting and casting the silver oxide, electrolytic refining is not required, the energy consumption is low, and the production cost is low. 2. The precious metal recovery method provided in the present application has a high yield of precious metal and a high purity of recovered precious metal.
[0049] While embodiments of the application have been shown and described, it is to be understood that the embodiments described are merely exemplary and that changes can be made in detail without departing from the principles and spirit of the application. The scope of the application is therefore defined by the appended claims and their equivalents.
Claims
1. A method for recovering a noble metal, characterized by, Comprise: S110, nitric acid leaching: dissolving silver-containing waste in nitric acid solution; S120, hydrolysis and impurity removal: adding sodium hydroxide solution dropwise in the dissolved solution to obtain impurity precipitation and silver nitrate solution; S130, filtration and water washing: separating the impurity precipitation from the silver nitrate solution, and water washing the impurity precipitation, and the washing water enters the silver nitrate solution; S140, alkali precipitation: adding sodium hydroxide solution dropwise in the silver nitrate solution to form silver oxide precipitation; S160, smelting and ingot casting: smelting the silver oxide to form silver single element, and casting the silver single element into ingot.
2. The precious metal recovery process according to claim 1, characterized in that, The step S110 comprises: S111, adding waste into the reaction kettle; S112, adding pure water and nitric acid into the reaction kettle; S113, heating the reaction kettle.
3. The precious metal recovery process of claim 2, wherein, In step S112, waste:nitric acid: pure water = 1 kg: 1 L: 3 L.
4. The precious metal recovery process of claim 1, wherein, The step S120 comprises: S121, adding sodium hydroxide solution with a mass concentration of 20% dropwise in the dissolved solution, and stirring and heating the solution for 1-1.5 h until the solution pH = 5-6; S122, stop stirring, and continue heating the solution for 1-1.5 h.
5. The precious metal recovery process according to claim 4, characterized in that, In steps S121 and S122, the solution heating temperature is 80-90℃.
6. The precious metal recovery process of claim 1, wherein, In step S140, sodium hydroxide solution with a mass concentration of 20% is added dropwise.
7. The precious metal recovery process of claim 1, wherein, In step S140, the solution pH is controlled to be 8-10.
8. The precious metal recovery process of claim 1, wherein, The step S160 comprises: S161, when the intermediate frequency furnace temperature is 200-300℃, the silver oxide is put into the intermediate frequency furnace for multiple times; S162, the intermediate frequency furnace is heated to 500-600℃, so that the silver oxide is converted into silver single element; S163, continue to heat to 1000-1100℃, so that the silver single element is melted; S164, the silver single element is cast into ingot through a mold.
9. The precious metal recovery process of claim 1, wherein, Between steps S140 and S160, there is also a step: S150, washing and drying: water washing and drying the silver oxide.
10. The precious metal recovery process of claim 9, wherein, In steps S130 and S150, when the conductivity of the washing water is <100 μs / cm, the water washing is stopped; In step S150, the drying temperature of the silver oxide is 180℃, and the drying time is 1-1.5 h.