Method for stripping silver-containing film coating and recovering silver
By heating and soaking with optimized bidding agents on the silver -containing film film, the efficient separation of coatings and bases were successfully achieved, solving the problem of low recovery efficiency and high processing costs of the existing technology, and achieved high efficiency and environmental protection. The recycling of silver resources.
Patent Information
- Application Number
- CN202411627287.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-14
- Publication Date
- 2025-01-28
Smart Images
Figure CN119372466A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of electronic waste treatment, and in particular to a method for stripping a silver-containing film coating to recover silver. Background Art
[0002] In the diversified and rapidly developing modern industrial system, many industries such as the manufacture of special chemical products, precision printing, the manufacture of electronic components and high-end electronic special materials, film and television program production, and photographic enlargement services are highly dependent on a series of advanced materials and processes. Among them, film, as a photosensitive material with a long history and excellent performance, occupies a pivotal position in the above industries. With its unique imaging quality and stability, it plays an irreplaceable role in many key links such as recording images, making printing plates, producing precision templates for electronic components, and film and television post-production.
[0003] However, with the widespread use of film in these industries, the problem of waste generated during its production and after use has become increasingly prominent. In particular, waste silver-containing film, due to its high-value silver element, its treatment and disposal has become an urgent challenge to the environment and resources. These wastes not only occupy valuable storage space and increase the operating costs of enterprises, but also may pollute the production environment if not handled properly, and even pose a potential threat to human health through infiltration, volatilization and other pathways.
[0004] In view of the preciousness of silver resources in waste silver-containing film, its efficient and environmentally friendly resource utilization has become a hot topic and focus of current research. However, the recycling of waste silver-containing film is not easy. The silver-containing coating on the film is closely combined with the film substrate through complex physical and chemical reactions, making it difficult to effectively separate the two. Although traditional recycling methods, such as incineration and chemical dissolution, can achieve silver recovery to a certain extent, they have many limitations. The incineration method is prone to cause air pollution, and the silver recovery rate is not high; while the chemical dissolution method requires the use of a large amount of chemical agents, and the processing steps are cumbersome, which not only increases the processing cost, but may also cause secondary pollution, such as wastewater, waste residue, etc., which imposes a new burden on the environment.
[0005] Therefore, developing an efficient, environmentally friendly, and economically feasible technology for recycling and processing waste silver-containing films to achieve high-value utilization of silver resources and reduce environmental pollution has become an urgent need for the current industry development. Summary of the invention
[0006] In view of the technical problems existing in the prior art, the present invention proposes a method for stripping silver-containing film coating to recover silver, which can achieve efficient separation of the silver-containing coating and the film substrate, thereby improving the silver recovery efficiency, reducing the processing cost, and reducing the impact on the environment.
[0007] A method for stripping a silver-containing film coating to recover silver comprises the following steps: cutting the silver-containing film into segments, adding a stripping agent thereto, heating and soaking the segments until the coating falls off, obtaining a silver-containing recovery liquid and film residues after solid-liquid separation, and recovering silver from the silver-containing recovery liquid.
[0008] Furthermore, the mass ratio of the silver-containing film to the stripping agent is 1 to 3:1.
[0009] Furthermore, the silver-containing film is cut into segments with a width of 0.5 to 2.5 cm.
[0010] Furthermore, the components of the stripping agent are composed of the following by weight: 3-10% alkali, 1-2% anionic surfactant, and 88-96% water.
[0011] Furthermore, the alkali is sodium hydroxide or potassium hydroxide.
[0012] Furthermore, the anionic surfactant is stearic acid or sodium dodecylbenzene sulfonate.
[0013] Furthermore, the soaking temperature is 25-70°C.
[0014] Furthermore, the method further comprises the following steps: continuously stirring during the soaking process.
[0015] Furthermore, the film waste is rendered harmless in a cement kiln.
[0016] Furthermore, the silver-containing film is selected from unqualified products and expired products generated in the manufacturing process of special chemical products; films and waste photographic paper generated in the printing process, films and waste photographic paper generated in the manufacturing process of electronic components and special electronic materials; films and waste photographic paper generated in the production process of film and television programs; and films and waste photographic paper generated in the process of photographic enlargement services.
[0017] In summary, the present invention has the following beneficial effects:
[0018] First, the process for recovering silver by peeling off the silver-containing film coating of the present invention is simple to operate but can effectively realize the efficient stripping of the silver-containing coating on the film, significantly reducing the amount of reagents required in the subsequent silver recovery process, simplifying the processing flow, and effectively reducing the overall processing cost.
[0019] Second, the coating stripper of the present invention introduces anionic surfactants, which significantly reduce the surface tension of the stripper, making it easier to penetrate into the coating, expand the contact area with the silver-containing coating, and accelerate the decomposition of the coating and the release of silver. At the same time, the anionic surfactant also enhances the emulsification and dispersion properties of the silver-containing recovery liquid, making the free silver more evenly dispersed therein, thereby greatly improving the recovery rate in the subsequent silver extraction process. BRIEF DESCRIPTION OF THE DRAWINGS
[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.
[0021] Figure 1 The present invention is a process diagram of stripping off the silver-containing film coating to recover silver. DETAILED DESCRIPTION
[0022] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.
[0023] A method for stripping a silver-containing film coating to recover silver comprises the following steps: Figure 1 As shown: the silver-containing film is cut into segments, a stripping agent is added thereto, and the film is heated and soaked until the coating falls off, and a silver-containing recovery liquid and film residues are obtained after solid-liquid separation, and silver is recovered from the silver-containing recovery liquid.
[0024] This solution is aimed at processing discarded silver-containing film. It is simple to operate but can effectively strip the silver-containing coating on the film, significantly reducing the amount of reagents required in the subsequent silver recovery process, simplifying the treatment process, and effectively reducing the overall treatment cost.
[0025] Furthermore, the mass ratio of the silver-containing film to the stripping agent is 1 to 3:1.
[0026] In this scheme, the mass ratio of silver-containing film to stripping agent is optimized to 1 to 3: 1. Only 1 / 3 of the film mass of stripping agent is needed to achieve coating stripping, thereby reducing the amount of reagent used, and reducing the cost of raw materials and reagent recovery and processing costs.
[0027] Furthermore, the silver-containing film is cut into segments with a width of 0.5 to 2.5 cm.
[0028] In the optimization of cutting size, this solution increases the contact area between the film coating and the stripping agent by setting an appropriate segment width, thereby improving the stripping efficiency of the coating.
[0029] Furthermore, the components of the stripping agent are composed of the following by weight: 3-10% alkali, 1-2% anionic surfactant, and 88-96% water.
[0030] This solution optimizes the composition and ratio of the stripper. The effective ingredients of the stripper are composed of alkali and anionic surfactants. The alkaline environment helps to neutralize the acidic substances in the film, promote the decomposition of the coating, and react with silver to free it from the film residue and the detached coating. Compared with simple alkali treatment, the addition of anionic surfactants can significantly reduce the surface tension of the stripper, making it easier to penetrate into the coating, expand the contact area with the silver-containing coating, and accelerate the decomposition of the coating and the release of silver. At the same time, anionic surfactants also enhance the emulsification and dispersion properties of the silver-containing recovery liquid, allowing the free silver to be more evenly dispersed therein, thereby greatly improving the recovery rate in the subsequent silver extraction process.
[0031] Furthermore, the alkali is sodium hydroxide or potassium hydroxide.
[0032] In the selection of alkali, this scheme adopts common raw materials such as sodium hydroxide or potassium hydroxide, which are not only low-cost but also highly environmentally friendly.
[0033] Furthermore, the anionic surfactant is stearic acid or sodium dodecylbenzene sulfonate.
[0034] In terms of the selection of anionic surfactants, this solution uses stearic acid and sodium dodecyl sulfate with high recovery efficiency and good biodegradability, which improves the safety and green environmental protection effect of the coating stripping process.
[0035] Furthermore, the soaking temperature is 25-70°C.
[0036] This solution optimizes the heating temperature of the silver film coating stripping process. Within this temperature range, the circuit board paint film can be effectively removed within 96 hours, and the fastest time is only 2 hours.
[0037] Furthermore, the method further comprises the following steps: continuously stirring during the soaking process.
[0038] In this solution, by adding stirring operation during the immersion process, the contact area between the film coating and the stripping liquid is further increased, thereby improving the stripping efficiency of the coating.
[0039] Furthermore, the film waste is rendered harmless in a cement kiln.
[0040] This solution uses cement kilns for harmless treatment, which not only effectively saves the fuel costs required for cement kilns, but also successfully avoids the secondary pollution problem that may be caused by discarded circuit boards, thereby achieving the dual benefits of energy saving and environmental protection.
[0041] Furthermore, the silver-containing film is selected from unqualified products and expired products generated in the manufacturing process of special chemical products; films and waste photographic paper generated in the printing process, films and waste photographic paper generated in the manufacturing process of electronic components and special electronic materials; films and waste photographic paper generated in the production process of film and television programs; and films and waste photographic paper generated in the process of photographic enlargement services.
[0042] The silver-containing films selected in this plan are selected from various types of discarded silver-containing films, which improves the level of reduction, harmless treatment and resource utilization of such wastes.
[0043] Example 1
[0044] The unqualified and expired silver-containing film produced in the manufacturing process of special chemical products was treated as follows: First, 10 kg of film was weighed and cut into segments with a width of 0.5 cm. Subsequently, 5 kg of stripping agent was added to these segments, in which the amount of sodium hydroxide added was 5% and the amount of sodium dodecylbenzene sulfonate added was 1%. After sufficient stirring, the mixture was immersed at 50°C until the silver-containing coating completely fell off. After the stripping was completed, the experiment carried out solid-liquid separation, and silver was recovered from the liquid phase of the silver-containing recovery liquid; the solid phase of the film residue was sent to the cement kiln for harmless treatment.
[0045] Example 2
[0046] The silver-containing film produced in the film and waste photo paper generated in the printing process, the film and waste photo paper generated in the manufacturing process of electronic components and special electronic materials was treated as follows: First, 10kg of film was weighed and cut into segments with a width of 1cm. Then, 5kg of stripping agent was added to these segments, and the amount of potassium hydroxide added to the stripping agent was 7% and the amount of stearic acid added was 1.5%. After sufficient stirring, the mixture was soaked at 25°C until the silver-containing coating completely fell off. After the stripping was completed, the experiment carried out solid-liquid separation to recover silver from the liquid silver-containing recovery liquid; the solid film residue was sent to a cement kiln for harmless treatment.
[0047] Example 3
[0048] The silver-containing film produced in the film and waste paper produced during the production of film and television programs was treated as follows: First, 10 kg of film was weighed and cut into segments with a width of 2.5 cm. Subsequently, 5 kg of stripping agent was added to these segments, in which the potassium hydroxide addition amount was 3% and the stearic acid addition amount was 1.5%. After sufficient stirring, the mixture was soaked at 30°C until the silver-containing coating completely fell off. After the stripping was completed, the experiment carried out solid-liquid separation to recover silver from the liquid phase of the silver-containing recovery liquid; the solid phase of the film residue was sent to a cement kiln for harmless treatment.
[0049] Example 4
[0050] The silver-containing film produced in the process of photographic enlargement service and waste paper was treated as follows: First, 10kg of film was weighed and cut into segments with a width of 1cm. Then, 5kg of stripping agent was added to these segments, in which the amount of sodium hydroxide added was 10% and the amount of sodium dodecylbenzene sulfonate added was 2%. After sufficient stirring, the mixture was immersed in 70℃ until the silver-containing coating completely fell off. After the stripping was completed, the experiment carried out solid-liquid separation, and silver was recovered from the liquid phase of the silver-containing recovery liquid; the solid phase of the film residue was sent to the cement kiln for harmless treatment.
[0051] Comparative Example 1
[0052] For the blank control group, the silver-containing film produced in the process of photographic enlargement service and waste paper was treated as follows: first, 10 kg of film was weighed and cut into pieces with a width of 1 cm. Then, 5 kg of water was added to these pieces. After sufficient stirring, the mixture was soaked at 70 ° C for 4 days, and then solid-liquid separation was performed to recover silver from the liquid silver-containing recovery liquid; the solid film residue was sent to the cement kiln for harmless treatment.
[0053] Comparative Example 2
[0054] Soda ash stripping group: The silver-containing film from the film and waste paper generated during the photographic enlargement service was treated as follows: First, 10 kg of film was weighed and cut into segments with a width of 1 cm. Subsequently, 5 kg of 10% sodium hydroxide solution was added to these segments. After sufficient stirring, the mixture was soaked at 70°C until the silver-containing coating completely fell off. After the stripping was completed, the test conducted solid-liquid separation to recover silver from the liquid silver-containing recovery liquid; the solid film residue was sent to a cement kiln for harmless treatment.
[0055] Comparative Example 3
[0056] Pure anionic active agent stripping group: The silver-containing film produced in the process of photographic enlargement service and waste paper was treated as follows: First, 10kg of film was weighed and cut into segments with a width of 1cm. Then, 5kg of 2% sodium dodecylbenzene sulfonate was added to these segments. After sufficient stirring, the mixture was soaked at 70℃ for 4d. After the stripping was completed, the test was carried out solid-liquid separation to recover silver from the liquid silver-containing recovery liquid; the solid film residue was sent to the cement kiln for harmless treatment.
[0057] The specific experimental conditions of each embodiment are shown in Table 1:
[0058] Table 1 List of experimental conditions corresponding to each embodiment and comparative example
[0059] Group Temperature ℃ Stripping agent and concentration % Cutting width cm Example 1 50 Sodium hydroxide 5%, sodium dodecylbenzene sulfonate 1% 0.5 Example 2 25 Potassium hydroxide 7%, stearic acid 1.5% 1.0 Example 3 30 Potassium hydroxide 3%, stearic acid 1.5% 2.5 Example 4 70 Sodium hydroxide 10%, sodium dodecylbenzene sulfonate 2% 1.0 Comparative Example 1 70 water 1.0 Comparative Example 2 70 Sodium hydroxide 10% 1.0 Comparative Example 3 70 Sodium dodecylbenzenesulfonate 2% 1.0
[0060] Test results and analysis
[0061] The present invention implements in detail and strictly verifies the technical solutions proposed in Examples 1 to 4 and Comparative Examples 1 to 4. The complete stripping time and silver recovery rate of the silver-containing coating of the film in each embodiment and comparative example are shown in Table 2:
[0062] Table 2: Complete stripping time and silver recovery rate of the silver-containing coating in each embodiment and comparative example
[0063] sample Silver coating complete peeling time h Silver recovery rate % Example 1 5 95 Example 2 96 96 Example 3 24 98 Example 4 2 98 Comparative Example 1 / 0 Comparative Example 2 5 83 Comparative Example 3 / 0
[0064] As shown in Table 2, in Comparative Example 1, since no stripping agent was added and only an equal amount of water was added, the silver-containing coating did not fall off after the silver-containing film was soaked for 4 days. Similarly, the stripping agent in Comparative Example 3 only contained 2% of anionic surfactant sodium dodecylbenzene sulfonate solution. Since the main function of the anionic surfactant in the stripping agent is to reduce the surface tension of the stripping agent itself, so as to promote the alkali in the stripping agent to effectively penetrate into the coating for neutralization and destruction, the anionic surfactant alone failed to effectively strip the silver-containing coating.
[0065] Compared with the above comparative examples, Examples 1 to 4 and Comparative Example 2 in which only 10% sodium hydroxide solution was added to the stripping agent all successfully achieved effective stripping of the silver-containing coating, but the performances were different. Specifically, the temperature added to the stripping agent showed an extremely significant positive correlation with the stripping effect of the silver-containing coating. As the temperature increased from 25°C (Example 2) to 70°C (Example 4), the time for the entire stripping of the silver-containing coating was shortened from 96h to only 2h.
[0066] The only difference between the experimental conditions of Example 4 and Comparative Example 2 is that 2% of anionic surfactant sodium dodecylbenzene sulfonate solution is added to the stripping agent. However, the silver-containing coating of Comparative Example 2 completely peeled off in 5 hours, which was delayed by 3 hours compared with 2 hours in Example 4. This fully demonstrates that the introduction of anionic surfactants in the stripping agent for the silver-containing coating can significantly improve the stripping efficiency of the silver-containing coating.
[0067] In terms of silver recovery efficiency, Examples 1 to 3 can achieve a high recovery rate of more than 95%, especially Example 4, whose recovery rate is as high as 98%. This remarkable achievement is mainly attributed to the fact that Examples 1 to 3 successfully removed the coating on the surface of the silver-containing film and made the silver in the film fully react and free in the silver recovery liquid. This step greatly reduces the physical obstacles in the silver extraction process, creates extremely favorable contact conditions for the subsequent extraction process, and thus significantly improves the silver recovery rate.
[0068] The only difference between the experimental conditions of Example 4 and Comparative Example 2 is that 2% of anionic surfactant sodium dodecylbenzene sulfonate solution is added to the stripping agent. Compared with the silver recovery rate of 83% in Comparative Example 2, the silver recovery rate of Example 4 is greatly improved to 98%. This is because sodium dodecylbenzene sulfonate enhances the emulsification and dispersion properties of the silver-containing recovery liquid, making the free silver more evenly dispersed therein, ensuring the uniformity and stability of the silver extraction chemical reaction, thereby further improving the silver recovery efficiency.
[0069] In summary, the anionic surfactant is introduced into the silver-containing coating stripper of the present invention, which significantly reduces the surface tension of the stripper, makes it easier to penetrate into the coating, expands the contact area with the silver-containing coating, effectively accelerates the decomposition process of the coating and the release of silver ions; it also significantly enhances the emulsification and dispersion performance of the silver-containing recovery liquid, ensures that the free silver particles can be evenly dispersed in the recovery liquid, and greatly improves the recovery efficiency in the subsequent silver extraction step. At the same time, the silver recovery process of the present invention is not only simple to operate, but also significantly reduces the amount of reagents required in the subsequent silver recovery process, effectively reducing the overall processing cost.
[0070] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.
Claims
1. A method for stripping silver-containing film coating to recover silver, characterized in that: The following steps are involved: The silver-containing film is cut into segments and immersed in a stripping agent, and heated and immersed until the coating falls off, and a silver-containing recovery liquid and film residues are obtained after solid-liquid separation, and silver is recovered from the silver-containing recovery liquid.
2. The method for recovering silver by stripping off the silver-containing film coating according to claim 1, characterized in that: The mass ratio of the silver-containing film to the stripping agent is 1 to 3:
1.
3. The method for recovering silver by stripping off the silver-containing film coating according to claim 1, characterized in that: The width of the segments cut from the silver-containing film is 0.5 to 2.5 cm.
4. The method for recovering silver by stripping off the silver-containing film coating according to claim 1, characterized in that: The components of the stripping agent are as follows by weight: 3-10% alkali, 1-2% anionic surfactant, and 88-96% water.
5. The method for recovering silver by stripping off the silver-containing film coating according to claim 4, characterized in that: The alkali is sodium hydroxide or potassium hydroxide.
6. The method for recovering silver by stripping off the silver-containing film coating according to claim 4, characterized in that: The anionic surfactant is stearic acid or sodium dodecylbenzene sulfonate.
7. The method for recovering silver by stripping off the silver-containing film coating according to claim 1, characterized in that: The soaking temperature is 25-70°C.
8. The method for recovering silver by stripping off the silver-containing film coating according to claim 1, characterized in that: The step of continuously stirring during the soaking process is also included.
9. The method for recovering silver by stripping off the silver-containing film coating according to claim 1, characterized in that: The film waste is rendered harmless in a cement kiln.
10. The method for recovering silver by stripping off the silver-containing film coating according to claim 1, characterized in that: The silver-containing film is selected from unqualified products and expired products produced in the manufacturing process of special chemical products; films and waste photo paper produced in the printing process, and films and waste photo paper produced in the manufacturing process of electronic components and special electronic materials; Film and waste paper generated during the production of film and television programs; film and waste paper generated during the photographic enlargement service process.