Process for purifying ag from the precipitate obtained by rinsing oled silver targets with hydrochloric acid
By reducing silver chloride with hydrochloric acid and iron blocks, combined with nitric acid dissolution and copper settling steps, the problems of high energy consumption, serious pollution, and low product purity in the existing silver extraction process have been solved, achieving the preparation of high-purity silver products and improving economic benefits.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SICHUAN UNIVERSITY OF SCIENCE AND ENGINEERING
- Filing Date
- 2023-05-15
- Publication Date
- 2026-06-02
AI Technical Summary
Existing technologies for silver extraction suffer from problems such as high energy consumption, severe pollution, cumbersome processes, low product purity, and the use of hydrazine hydrate, a potentially explosive and hazardous chemical, and the product quality is not high enough.
Silver chloride was reduced with hydrochloric acid and iron blocks. By controlling the temperature and stirring the reaction, the mixture was filtered and washed, then dissolved in nitric acid and copper was added and allowed to stand. After filtration and washing, a high-purity silver product was finally obtained.
This method enables the preparation of high-purity silver products, avoids contamination of the product due to incomplete reaction of iron powder, reduces the purity requirements of raw materials, improves economic efficiency, and generates CuFe2O4 products that can be used for wastewater treatment.
Smart Images
Figure CN116574917B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a process for refining Ag precipitates obtained by rinsing OLED silver targets with hydrochloric acid, belonging to the field of hydrometallurgical technology. Background Technology
[0002] Currently, the traditional processes for extracting silver from silver chloride are mainly divided into two types: pyrometallurgical and hydrometallurgical. Pyrometallurgical silver extraction involves adding sodium carbonate to silver chloride, while hydrometallurgical silver extraction involves replacing silver with iron powder, ammonia leaching, and hydrazine hydrate precipitation. The basic principle of pyrometallurgical silver extraction is: 4AgCl + 2Na₂CO₃ → 4Ag + 4NaCl + 2CO₂ + O₂. Its advantages are simple process and virtually no impurity generation; its disadvantages are high energy consumption and CO₂ production. In hydrometallurgical silver extraction, the basic principle of replacing silver with iron powder is: 2AgCl + Fe → 2Ag + FeCl₂. Using this method, to avoid the formation of hydroxide precipitates from the hydrolysis of iron salts and their mixing with silver chloride and silver powder, excess concentrated hydrochloric acid needs to be added. Simultaneously, if the iron powder reaction is incomplete, it can easily enter the product, making separation difficult and reducing product quality, often requiring refining steps, resulting in a cumbersome process and serious pollution. Furthermore, this method requires high purity of the raw material silver chloride; the presence of other metallic impurities will directly affect the purity of the product. The basic principles of ammonia leaching and hydrazine hydrate precipitation in wet silver extraction are: AgCl + 2NH3·H2O → [Ag(NH3)2]Cl + 2H2O; 4[Ag(NH3)2]Cl → AgCl + N2H4·H2O → 4Ag + N2 + 4NH3 +
[0003] The reaction is 4NH₄Cl + H₂O. The principle of silver extraction using hydrazine hydrate is: 2AgCl + 2N₂H₄·H₂O → 2Ag + N₂ + 2NH₄Cl + 2H₂O. Both methods require hydrazine hydrate, a potentially explosive and hazardous chemical that can cause harm to humans through the eyes, skin, or inhalation. Furthermore, it is highly toxic to aquatic life and may cause long-term adverse effects on the aquatic environment.
[0004] Patent application CN104032145B discloses a method for extracting and separating Ag and Cu from flotation silver concentrate. The specific steps of the method are as follows: Thiourea and urea are used for combined cyclic leaching. Thiourea Cu is cooled and crystallized. The crystals contain more than 15% Cu, about 2% Ag, 0.04% Pb, and about 1% Zn. Al plates replace the silver fluff, and thiourea is regenerated. Thiourea is then added again, followed by the addition of a catalyst, and the process is repeated for a second thiourea leaching. After 3-4 cycles of cyclic leaching, thiourea Cu produces saturated crystals, which are dissolved in dilute H2SO4. The Ag is then replaced with Cu, and Cu is replaced with Zn powder or CuSO4·5H2O is evaporated and crystallized. The crystallized liquid is then replaced with Al to replace the silver fluff, and combined with the Cu-replaced silver fluff. After calcination at 500℃, it is leached with H2SO4 or HNO3. The Ag is precipitated with HCl to form AgCl, and then reduced with a mixture of ammonia and hydrazine hydrate to obtain 99.95% Ag powder, which is then cast into Ag ingots. This method has the following drawbacks: the hydrazine hydrate used in this method is an easily explosive and hazardous chemical with high toxicity; in addition, the quality of the obtained Ag product is not high enough and there is considerable room for improvement. Summary of the Invention
[0005] The first technical problem to be solved by the present invention is to provide a process for refining Ag precipitate obtained by rinsing OLED silver target material with hydrochloric acid.
[0006] The present invention provides a process for refining Ag precipitate obtained by rinsing OLED silver targets with hydrochloric acid, comprising the following steps:
[0007] a. Pretreatment of raw material silver chloride: The raw material silver chloride is dried and pulverized; wherein, the content of each element in the raw material silver chloride is, by mass percentage, C 4.99~18.50wt.%, O 2.92~5.47wt.%, Al 0.58~0.40wt.%, Cl 22.81~18.94wt.%, Ag 68.70~56.70wt.%, the remainder being unavoidable impurities;
[0008] b. Crude processing: The pretreated raw material is mixed with hydrochloric acid, iron blocks are added, the temperature is controlled, and the mixture is stirred to react. After the reaction is completed, the mixture is filtered and washed, and the solid and liquid phases are collected separately. The solid-liquid ratio of the raw material to hydrochloric acid is 3:1, and the mass ratio of the raw material to the iron block is 5:1.
[0009] c. Refining: The solid product obtained in step b is dissolved in nitric acid, and the solid and liquid phases are collected separately. The solid phase is recycled into the silver chloride raw material from step a, and copper is added to the liquid phase. The mass ratio of copper to silver chloride raw material from step b is 1:2.8-3.2. After standing for a period of time, the mixture is filtered and washed, and the solid and liquid phases are collected separately. The liquid phase is recycled into the liquid phase obtained in step b, and the solid phase is filtered, washed, and dried to obtain the product.
[0010] In step a, the drying temperature during the raw material pretreatment is 100-110℃.
[0011] In step b, the volume concentration of the hydrochloric acid is 21.8%-36%.
[0012] In step b, the iron block is a 2cm*3cm*5cm rectangle with holes; the pretreatment process of the iron block before use is: grinding and acid washing to remove surface dirt.
[0013] In step b, the solid phase is Ag containing a small amount of Al impurities, and the liquid phase is FeCl2.
[0014] In step b, the temperature of the stirring reaction is 30-60℃.
[0015] In step c, the nitric acid concentration V 硝酸 :V 水 The ratio is 1:1.
[0016] In step c, copper is added to the liquid phase, and after standing for a period of time, it is filtered and washed to collect the solid and liquid phases respectively. The solid phase is pure Ag, and the liquid phase is Cu(NO3)2 containing a small amount of Al(NO3)3.
[0017] In step c, the copper is a 2cm*3cm*5cm rectangular piece with holes, containing no impurities other than Cu and C; the preferred mass ratio of copper to silver chloride in step b is 1:3.
[0018] The second technical problem to be solved by the present invention is to provide a refined Ag product obtained by a process of rinsing OLED silver target material with hydrochloric acid to obtain precipitated refined Ag.
[0019] In the refined Ag product, the mass percentage of Ag element is ≥99.9%.
[0020] Beneficial effects of this invention:
[0021] 1. The process for refining Ag precipitate obtained by rinsing OLED silver target material with hydrochloric acid provided by the present invention uses iron block as a reducing agent, which effectively avoids the contamination of the product by unreacted iron; in addition, Fe and Cu are generated in the form of CuFe2O4 product, which can be used in the field of wastewater treatment, and has good economic and environmental benefits.
[0022] 2. The process for refining Ag precipitate obtained by rinsing OLED silver target material with hydrochloric acid provided by the present invention has low requirements for raw materials, does not require excessive purification, can effectively reduce costs, and thus improve efficiency. Attached Figure Description
[0023] Figure 1This is a process flow diagram of the purification of Ag precipitate obtained by rinsing OLED silver target material with hydrochloric acid according to the present invention.
[0024] Figure 2 Comparison of the raw material composition of two batches of this invention
[0025] Figure 3 A comparison of the composition of the iron block used in this invention before and after treatment.
[0026] Figure 4 The present invention describes the process for refining Ag precipitate obtained by rinsing OLED silver target material with hydrochloric acid, and the solid phase composition and morphology after dissolving the crude product in nitric acid.
[0027] Figure 5 A comparison chart of raw materials, crude and refined product components of the purified Ag obtained by rinsing OLED silver targets with hydrochloric acid according to this invention.
[0028] Figure 6 The morphology comparison of the raw materials, crude and refined products of the purified Ag precipitate obtained by rinsing OLED silver targets with hydrochloric acid in this invention.
[0029] Figure 7 This invention discloses a process for refining Ag precipitate obtained by rinsing OLED silver target material with hydrochloric acid. The CuFe2O4 crystal structure and physical sample are also described (illustrated).
[0030] Figure 8 A schematic diagram of the purification reaction phenomenon of Ag precipitate obtained by rinsing OLED silver target material with hydrochloric acid according to the present invention. Detailed Implementation
[0031] The specific embodiments of the present invention will be further described below with reference to examples, but the present invention is not limited to the scope of the embodiments described herein.
[0032] Example 1
[0033] Weigh 10.0016 g of dried and pulverized raw material 1 and add it to 100 mL of hydrochloric acid (21.8%). Add an iron block with a mass of 75.0567 g. Maintain the temperature at 60 °C and stir continuously (309 r / min). Collect the generated gas with water. Stop the reaction when the white color completely turns gray, which takes 31 min. Collect the solid and liquid phases separately. After filtering and washing the solid phase, slowly add it to 100 mL of nitric acid. Appropriate heating can be used to promote its dissolution. Collect the solid and liquid phases separately after the solution stabilizes. The product quality and yield are shown in Table 1.
[0034] Example 2
[0035] Weigh 10.0007 g of dried and pulverized raw material 1 and add it to 100 mL of hydrochloric acid (24.7%). Add an iron block with a mass of 75.0567 g. Maintain the temperature at 60 °C and stir continuously (307 r / min). Collect the generated gas with water. Stop the reaction when the white color completely turns gray, which takes 16 min. Collect the solid and liquid phases separately. After filtering and washing the solid phase, slowly add it to 100 mL of nitric acid. Appropriate heating can be used to promote its dissolution. Collect the solid and liquid phases separately after the solution stabilizes. The product quality and yield are shown in Table 1.
[0036] Example 3
[0037] Weigh 10.0001 g of dried and pulverized raw material 1 and add it to 100 mL of hydrochloric acid (30.8%). Add an iron block with a mass of 75.0567 g. Maintain the temperature at 60 °C and stir continuously (322 r / min). Collect the generated gas with water. Stop the reaction when the white color completely turns gray, which takes 23 min. Collect the solid and liquid phases separately. After filtering and washing the solid phase, slowly add it to 100 mL of nitric acid. Appropriate heating can be used to promote its dissolution. Collect the solid and liquid phases separately after the solution stabilizes. The product quality and yield are shown in Table 1.
[0038] Example 4
[0039] Weigh 10.0069 g of dried and pulverized raw material 1 and add it to 100 mL of hydrochloric acid (35%). Add an iron block with a mass of 75.0567 g. Maintain the temperature at 60 °C and stir continuously (313 r / min). Collect the generated gas with water. Stop the reaction when the white color completely turns gray, which takes 66 min. Collect the solid and liquid phases separately. After filtering and washing the solid phase, slowly add it to 100 mL of nitric acid. Appropriate heating can be used to promote its dissolution. Collect the solid and liquid phases separately after the solution stabilizes. The product quality and yield are shown in Table 1.
[0040] Example 5
[0041] Weigh 10.0022 g of dried and pulverized raw material 1 and add it to 100 mL of hydrochloric acid (24.7%). Add an iron block with a mass of 75.0567 g. Maintain the temperature at 50 °C and stir continuously (287 r / min). Collect the generated gas with water. Stop the reaction when the white color completely turns gray, which takes 29 min. Collect the solid and liquid phases separately. After filtering and washing the solid phase, slowly add it to 100 mL of nitric acid. Appropriate heating can be used to promote its dissolution. Collect the solid and liquid phases separately after the solution stabilizes. The product quality and yield are shown in Table 1.
[0042] Example 6
[0043] Weigh 10.0011 g of dried and pulverized raw material 1 and add it to 100 mL of hydrochloric acid (24.7%). Add an iron block with a mass of 75.0567 g. Maintain the temperature at 40 °C and stir continuously (287 r / min). Collect the generated gas with water. Stop the reaction when the white color completely turns gray, which takes 38 min. Collect the solid and liquid phases separately. After filtering and washing the solid phase, slowly add it to 100 mL of nitric acid. Appropriate heating can be used to promote its dissolution. Collect the solid and liquid phases separately after the solution stabilizes. The product quality and yield are shown in Table 1.
[0044] Example 7
[0045] Weigh 10.0018 g of dried and pulverized raw material 1 and add it to 100 mL of hydrochloric acid (24.7%). Add an iron block with a mass of 75.0567 g. Maintain the temperature at 18°C and stir continuously (238 r / min). Collect the generated gas with water. Stop the reaction when the white color completely turns gray, which takes 72 min. Collect the solid and liquid phases separately. After filtering and washing the solid phase, slowly add it to 100 mL of nitric acid. Appropriate heating can be used to promote its dissolution. Collect the solid and liquid phases separately after the solution stabilizes. The product quality and yield are shown in Table 1 (the composition of raw material 1 is shown in Table 2).
[0046] Table 1
[0047]
[0048]
[0049] Example 8
[0050] Weigh 5.0005g of dried and pulverized raw material 2 and add it to 40mL of hydrochloric acid (24.7%). Add an iron block with a mass of 75.0567g. Maintain the temperature at 50℃ and stir continuously (287r / min). Collect the generated gas with water. Stop the reaction when the white color completely turns gray, which takes 44min. Collect the solid and liquid phases separately. After filtering and washing the solid phase, slowly add it to 90mL of nitric acid (1:1). Appropriate heating can be used to promote dissolution. Collect the solid and liquid phases separately after the solution stabilizes. Add a copper block to the liquid phase and let it stand for a period of time. Collect the solid and liquid phases separately. Filter, wash, and dry the solid phase to obtain the product. The composition and morphology of the raw material, crude product, and refined product are as follows. Figure 4 and Figure 5 As shown in Table 2, the yield and components of each segment are as follows.
[0051] Table 2
[0052]
[0053] This specific embodiment is merely an explanation of the present invention and is not intended to limit the present invention. After reading the specification of the present invention, those skilled in the art may make some modifications or improvements based on the present invention, but as long as they are within the scope of the claims of the present invention, they are protected by patent law.
Claims
1. A process for refining Ag precipitate obtained by rinsing OLED silver target material with hydrochloric acid, characterized in that, Includes the following steps: a. Pretreatment of raw material silver chloride: The raw material silver chloride is dried and pulverized; wherein, the content of each element in the raw material silver chloride is, by mass percentage, C, 4.99-18.50wt%, O, 2.92-5.47wt%, Al, 0.40-0.58wt%, Cl, 18.94-22.81wt%, Ag, 56.70-68.70wt%, and the remainder are unavoidable impurities; b. Crude processing: The pretreated raw material is mixed with hydrochloric acid, iron blocks are added, the temperature is controlled, and the mixture is stirred to react. After the reaction is completed, the mixture is filtered and washed, and the solid and liquid phases are collected separately. The solid-liquid ratio of the raw material to hydrochloric acid is 3:1, and the mass ratio of the raw material to the iron block is 5:
1. c. Refining: The solid product obtained in step b is dissolved in nitric acid, and the solid and liquid phases are collected separately. The solid phase is recycled into the silver chloride raw material from step a, and copper is added to the liquid phase. The mass ratio of copper to silver chloride raw material from step b is 1:2.8-3.
2. After standing for a period of time, the mixture is filtered and washed, and the solid and liquid phases are collected separately. The liquid phase is recycled into the liquid phase obtained in step b, and the solid phase is filtered, washed, and dried to obtain the product.
2. The process for refining Ag precipitate obtained by rinsing OLED silver target material with hydrochloric acid according to claim 1, characterized in that, In the raw material pretreatment described in step a, the drying temperature is 100-110℃.
3. The process for refining Ag precipitate obtained by rinsing OLED silver target material with hydrochloric acid according to claim 1, characterized in that, The volume concentration of hydrochloric acid in step b is 21.8%-36%.
4. The process for refining Ag precipitate obtained by rinsing OLED silver target material with hydrochloric acid according to claim 1, characterized in that, The iron block mentioned in step b is a rectangle with holes measuring 2cm*3cm*5cm; the pretreatment process for the iron block before use is: grinding and pickling.
5. The process for refining Ag precipitate obtained by rinsing OLED silver target material with hydrochloric acid according to claim 1, characterized in that, The solid phase in step b is Ag and contains Al impurities; the liquid phase is FeCl2.
6. The process for refining Ag precipitate obtained by rinsing OLED silver target material with hydrochloric acid according to claim 1, characterized in that, The temperature for stirring the reaction in step b is 30-60℃.
7. The process for refining Ag precipitate obtained by rinsing OLED silver target material with hydrochloric acid according to claim 1, characterized in that, In step c, the nitric acid concentration V 硝酸 :V 水 The ratio is 1:
1.
8. The process for refining Ag precipitate obtained by rinsing OLED silver target material with hydrochloric acid according to claim 1, characterized in that, In step c, copper is added to the liquid phase, and after standing for a period of time, it is filtered and washed to collect the solid and liquid phases separately. The solid phase is pure Ag, and the liquid phase is Cu(NO3)2 containing Al(NO3)3 impurities.
9. The process for refining Ag precipitate obtained by rinsing OLED silver target material with hydrochloric acid according to claim 1, characterized in that, The copper in step c is a 2cm*3cm*5cm rectangular shape with holes, containing no impurities other than Cu and C; the mass ratio of copper to silver chloride in step b is 1:
3.
10. The refined Ag product obtained by the process of precipitating and refining Ag obtained by rinsing OLED silver target material with hydrochloric acid according to any one of claims 1-9; wherein, The refined Ag product contains Ag element at a mass percentage of ≥99.9%.