Method for separating and recycling silver-copper composite material through selective interface oxidation

Abstract

The invention discloses a method for separating and recycling a silver-copper composite material through selective interface oxidation. The method comprises the following steps that the material is crushed and sheared, and a crushed material is obtained; the crushed material is pretreated and then fed into an oxidation fluidized bed, an internal oxidation reaction is conducted in a gas phase at the temperature of 400-700 DEG C and the oxygen pressure of 0.2-0.6 MPa, the reaction time is 20-60 h, and a high-temperature material is obtained; quenching the high-temperature material to generate stress cracks on an oxidation interface to obtain a cooled material; and stripping the cooled material under the mechanical action to obtain a recycled copper material and a recycled silver material, oxidizing the electrical contact material or leftover materials of the electrical contact material in the oxygen atmosphere to oxidize an interface between the silver-copper composite materials to form an oxidation film, separating the two materials of the silver-copper composite materials under the quenching and mechanical actions, and then, obtaining the recycled copper material and the recycled silver material. The method is high in recovery rate, high in recovery purity and environment-friendly.

Description

Technical Field

[0001] The present application relates to a production process for electrical contact materials, and in particular to a method for selective interfacial oxidation separation and recovery of silver-copper composite materials. Background Art

[0002] Electrical contacts are commonly used components in existing electrical equipment, with the most common being silver-copper composite electrical contacts. These contacts consist of an electrical contact end and a fixed end. The electrical contact end is made of a silver alloy or silver-based material, while the fixed end is made of copper or a copper alloy. These silver alloys, silver-based materials, copper, or copper alloys are processed into strips or wires. The strips are then rolled and laminated to form silver-copper composite strips, which are then stamped to create silver-copper composite electrical contact products. Wires are then cold-forged to create silver-copper composite electrical contact products.

[0003] The scraps left after stamping or cold heading still contain a large amount of silver alloys or silver-based materials. Silver, as a precious metal, is expensive and requires reasonable recovery. Current technologies use electrolysis or acid leaching followed by reduction to recover precious silver.

[0004] This type of method cannot completely reduce the silver ions dissolved in the solution by electrolysis or reaction, and other metal ions are introduced and doped during the reduction process, resulting in a low recovery rate and unstable purity of the recovered silver. The overall recovery process is complicated, the energy and material consumption is large, and the waste liquid and waste residue generated are not environmentally friendly. Summary of the Invention

[0005] In order to reduce the cost in the production process and recover high-purity copper and silver alloy materials with high efficiency and high recovery rate, a method for selective interfacial oxidation separation and recovery of silver-copper composite materials is provided.

[0006] The above-mentioned object of the present invention is achieved through the following technical solutions: A method for selective interfacial oxidation separation and recovery of silver-copper composite materials, comprising the following steps: Crushing and shearing the material to obtain crushed material; The crushed material is pre-treated and sent to the oxidation fluidized bed for internal oxidation reaction in the gas phase at 400-700°C and oxygen pressure of 0.2-0.6MPa for 20-60h to obtain high-temperature material; The high-temperature material is rapidly cooled to generate stress cracks at the oxidation interface to obtain a cooled material; The cooled material is placed under mechanical action for stripping to obtain recovered copper material and recovered silver material.

[0007] By adopting the above technical solution, the silver-copper composite material is broken, so that the interface of the silver-copper composite material is partially exposed, thereby increasing the gas-solid contact area; Then, oxygen is passed through the fluidized bed to selectively oxidize copper at 400-700°C, using the oxidation potential difference between copper and silver to achieve precise interface oxidation. After high-temperature oxidation and rapid cooling, the difference in thermal expansion coefficients between CuO and Cu is used to generate interfacial shear stress, and then mechanical vibration is used to peel off the oxide layer; The copper recovery rate of the present application is greater than 90%, the silver purity is greater than 99.5%, and the silver recovery rate is greater than 98.5%. In addition, since the cyanide leaching step is omitted, the process is simplified and the energy consumption is reduced. Therefore, the recovery rate, recovery purity, environmental protection, cost, and stability are comprehensively superior to the existing technology.

[0008] Optionally, the method further includes placing the recovered copper material and the recovered silver material separately in a smelting furnace, embedding them with graphite powder or carbon powder, and then performing high-temperature smelting, refining, and impurity removal to obtain recovered silver alloy ingots and recovered copper ingots.

[0009] By adopting the above technical solution, the recovered copper materials and recovered silver materials are refined, and the copper oxides and silver oxides correspondingly generated during the reduction oxidation process are reduced, thereby improving the recovery rate and purity of the finally obtained recovered materials.

[0010] Optionally, the gas phase in the oxidation fluidized bed further includes carbon dioxide, and the molar ratio of carbon dioxide to oxygen is 0.9-0.95:1.

[0011] By adopting the above technical solution, CO2 is introduced into the oxidizing gas phase. During the copper oxidation process, due to the temperature and local oxygen concentration differences, oxidation intermediates are produced. Cuprous oxide is mixed into the copper oxide, resulting in a loose and thick oxide layer on the copper surface, which further affects the subsequent interface during mechanical stripping and makes it unsafe to peel. The weak reaction of CO2 with Cu2O (Cu2O+CO2→2CuO+CO) consumes surface oxygen vacancies, making the oxide layer denser, reducing the deviation in the oxide layer thickness, improving the copper metal retention rate, and avoiding the problem of incomplete stripping caused by local overoxidation, further improving the purity of silver recovery.

[0012] Optionally, the gas phase in the oxidation fluidized bed further comprises ozone, and the content of ozone is 1-3 vol%.

[0013] By adopting the above technical solution, 1~3% O3 is added to the oxidation fluidized bed, and its high oxidation potential can be used to induce copper interface oxidation more quickly at a lower temperature, shortening the oxidation time. The low temperature environment can inhibit oxygen oxidation, taking into account both speed and selectivity. In addition, the concentration should not be too high. If the concentration is too high, not only will the recovery rate of copper accelerated oxidation be reduced, but the high concentration of ozone will also oxidize copper and silver at the same time, destroying the selectivity, causing the advantage of copper preferential oxidation to be lost, and reducing the recovery rate and purity of silver.

[0014] Optionally, the pretreatment includes placing the crushed material in a reducing fluidized bed, using a mixture of hydrogen and nitrogen at 400° C. to remove impurity oxygen atoms at the interface of the copper-silver material.

[0015] By adopting the above technical solution, trace oxygen atoms will remain at the interface of the existing electrical contact material during the rolling composite process / stamping process due to the ambient atmosphere or impurities in the raw materials. These oxygen atoms will form non-stoichiometric CuO with copper. X Metastable compounds, and because there is already disordered oxygen occupying the lattice gap, it hinders the uniform diffusion of oxygen in the subsequent oxidation stage; In this application, the CuO at the interface is heated at 400 °C in a hydrogen and nitrogen mixed atmosphere. X The metastable compound is reduced, causing the interface to be reconstructed. The copper lattice defect density at the reduced interface is reduced, and the regular copper lattice can provide a more uniform oxygen diffusion channel. The removal of randomly distributed impurities allows the oxidation reaction to preferentially nucleate uniformly from active sites such as the lattice, reducing the thickness difference of the oxide film at the interface, shortening the time required for subsequent interface oxidation, and making it easier to completely strip the recovered silver and copper materials, thereby improving the purity of the recovered silver alloy materials.

[0016] Optionally, the hydrogen content in the mixture of hydrogen and nitrogen is 2 vol%, and the processing time is 10-11 minutes.

[0017] By adopting the above technical solution, the pretreatment effect obtained under the process parameters is better, and the energy consumption cost, the purity of the recovered silver and the recovery amount are better.

[0018] Optionally, the rapid cooling method is to spray liquid nitrogen onto the high-temperature material, and the contact time of the spraying liquid nitrogen is controlled to be 3 to 5 seconds.

[0019] By adopting the above technical solution, the cooling efficiency is 5 to 6 times that of water quenching, and the difference in thermal expansion coefficient between copper oxide and copper is more effectively utilized to generate greater interfacial stress and improve the stripping efficiency. In addition, it can also avoid the possibility of re-oxidation of the surface of copper and silver materials due to water quenching. Although the cost is relatively high, for high-purity silver materials, it can be recycled and reused faster, reducing the secondary smelting process.

[0020] Optionally, during the liquid nitrogen spraying, the high-temperature material is in a closed cabin, and argon gas is continuously introduced to replace the atmosphere in the cabin.

[0021] By adopting the above technical solution, the high-temperature material is in a closed cabin during liquid nitrogen spraying, and argon gas is continuously introduced to replace the atmosphere in the cabin.

[0022] In summary, this application has at least the following beneficial effects: The present application chooses to oxidize the electrical contact material or the scraps of the electrical contact material under an oxygen atmosphere, so that the interface between the silver-copper composite material is oxidized to form an oxide film, so that the junction of the two is separated, the stress at the interface is strengthened under the action of rapid cooling, and then the silver and copper materials are separated under mechanical action. The silver and copper materials can be purified and recovered separately. Therefore, compared with chemical recovery, the method of the present application does not require the silver and copper materials to be completely converted into an ionic state and then reduced, and no waste residue and waste liquid are generated. The recovery process is simpler and faster, and the recovery rate and purity of the recovered silver and copper materials are improved. DETAILED DESCRIPTION

[0023] The silver-copper composite material in the application is an electrical contact material and scraps of electrical contact materials, which are formed by stamping after rolling and compounding copper strips and silver alloy strips or silver-based material strips, or by cold heading of copper wires and silver alloy wires or silver-based material wires. It is a composite metal material with obvious interface distinction, one side of which is silver alloy or silver-based material, and the other side is copper or copper-based alloy.

[0024] The copper strips in Examples 1-17 were made of high-purity copper with a purity greater than 99.5% by weight, and the silver strips were made of high-purity silver with a purity greater than 99.96% by weight. After stamping, the copper strips had a thickness of 1.2 mm, and the silver strips had a thickness of 0.8 mm.

[0025] Example 1 A method for selective interfacial oxidation separation and recovery of silver-copper composite materials, the specific steps of which are as follows: Crushing and shearing the material to 5±2mm to obtain crushed material; The crushed material was fed into an oxidation fluidized bed and subjected to internal oxidation reaction at 500°C, an oxygen pressure of 0.4 MPa, and an air flow rate of 0.8 m / s for 50 hours to obtain a high-temperature material. The high-temperature material is transferred into the sealed cabin while it is still hot. Argon gas is continuously passed through the sealed cabin at a flow rate of 15 cm 3 / s, spray liquid nitrogen on the high-temperature material for rapid cooling, and the contact time between the high-temperature material and the sprayed liquid nitrogen is 4s to obtain a cooled material; The cooled material is placed under mechanical vibration for stripping, and then sorted to obtain recovered copper material and recovered silver material; 200-mesh graphite powder and 200-mesh charcoal are mixed in a mass ratio of 1:1 to obtain an embedding agent, the embedding agent is laid in a furnace, and then the recovered silver material is filled and then covered with the embedding agent. The amount of embedding agent used here is 5% of the mass of the recovered silver material. The furnace is heated and kept at 1100°C for 30 minutes, stirred every 10 minutes, and the rotation speed is 32 rpm. After the end of the heat preservation, it is allowed to stand for 15 minutes, the scum is skimmed off, and the temperature is cooled to 950°C and then poured to obtain a silver recovery ingot; Use 200-mesh carbon powder as an embedding agent, lay the embedding agent in the furnace, then fill in the recovered copper material, and then cover the recovered copper material with the embedding agent. The amount of embedding agent here is 3wt% of the recovered copper. Refine at 1200℃ for 20min, remove the slag, and cast to obtain a copper recovery ingot.

[0026] Comparative Example 1 A method for separating and recovering a silver-copper composite material, the specific steps are as follows: 65 wt % nitric acid and 98 wt % sulfuric acid were mixed in a volume ratio of 1:3 to obtain a mixed acid; The silver-copper composite material was added to the mixed acid at a solid-liquid ratio of 1:8, reacted at 25°C in an ice-water bath for 30 minutes, and filtered to obtain a filtrate and copper slag; A 10 wt% sodium chloride solution is added to the filtrate at a molar ratio of silver to chloride ion of 1:1.2, the pH is controlled at 1-3, and the mixture is stirred for 30 minutes, and the silver chloride precipitate is filtered to obtain a silver chloride precipitate; the silver chloride precipitate is washed and then pulped to obtain a silver chloride slurry with a solid content of 20%; an excess of 20 wt% hydrazine hydrate is added to the silver chloride slurry, the mixture is reacted at 80° C. and pH 10 for 1 hour, silver powder is obtained by filtration, and silver recovery ingots are obtained by pressing and smelting. The copper slag was dissolved in 5 mol / L sulfuric acid solution at 80 °C and then heated at a current density of 250 A / m 2 Electrolytic refining of copper to obtain recycled copper material.

[0027] Example 2 A method for selective interfacial oxidation separation and recovery of silver-copper composite materials is provided. The method differs from Example 1 in that the crushed material is fed into a reducing fluidized bed in a mixed atmosphere of hydrogen and nitrogen with a hydrogen content of 2 vol%, and is pretreated at 400°C for 10 min.

[0028] Example 3 A method for selective interfacial oxidation separation and recovery of silver-copper composite materials, which differs from Example 1 in that the crushed material is fed into a reducing fluidized bed, a mixed atmosphere of hydrogen and nitrogen is used, the hydrogen content is 2 vol%, and pretreatment is performed at 400°C for 10 minutes; and the reaction time in the oxidation fluidized bed is 45 hours.

[0029] Example 4 A method for selective interfacial oxidation separation and recovery of silver-copper composite materials is provided, which differs from Example 1 in that the rapid cooling method uses water cooling to directly put the high-temperature material into water at 20°C for direct cooling.

[0030] Example 5 A method for selective interfacial oxidation separation and recovery of silver-copper composite materials is provided, which differs from Example 1 in that the argon gas flow rate in the sealed chamber is 0 and the atmosphere is not actively updated.

[0031] The recovered silver materials and the recovered copper materials obtained in Examples 1 to 5 and Comparative Example 1 were tested for purity and recovery rate. The test results are shown in the following table.

[0032] Silver-based recovery rate = the mass of silver in the recovered silver ingots ÷ the mass of silver in the sample × 100%.

[0033] Copper-based recovery rate = the mass of copper in the recovered copper ingot ÷ the mass of copper in the sample × 100%.

[0034] Silver purity = the silver purity in the recovered silver ingots, expressed as a percentage by mass.

[0035] Copper purity = the copper purity in the recovered copper ingots, expressed as a percentage by mass.

[0036] Table 1. Purity and recovery rate of recycled materials in Examples 1 to 5 and Comparative Example 1

[0037] As shown in Table 1, the silver recovery rate, silver purity, copper recovery rate and copper purity of Example 1 of the present application are significantly better than those of Comparative Example 1.

[0038] In Comparative Example 1, since the actual dissolution rate of silver in the mixed acid does not reach 100%, and the precipitated silver chloride is doped with copper ions, multiple washings are required. The washing process will lead to the loss of silver chloride, reducing the silver recovery rate. At the same time, the washed silver chloride will inevitably still contain copper ions, which also limits the purity of silver. The passivation film of copper is not complete during the hot dissolution of sulfuric acid, and the copper ions remain in the electrolyte after electrolysis. Both of these will limit the copper recovery rate.

[0039] In addition, the process represented by Comparative Example 1 produces a large amount of waste liquid and waste residue, such as electrolytic sludge, copper slag residue, wastewater containing copper ions, and hydrazine-containing tail gas, and the treatment cost is relatively high.

[0040] In this regard, the present application uses gas phase oxidation to directly and selectively oxidize the copper interface, avoiding the multi-step loss of silver ionization and dissolution in the chemical method. At the same time, copper is recovered in a metallic state without the need for acid leaching and electrolysis, reducing the generation of copper slag residue, waste liquid, and waste gas. Therefore, the method is superior to the chemical method represented by Comparative Example 1 in terms of recovery rate, recovery purity, environmental protection, cost, and stability. The method of the present application is particularly suitable for the high-purity silver represented by electrical contact materials and large-scale continuous production requirements.

[0041] Comparing Examples 1 to 3, it can be seen that the silver recovery rate, silver recovery purity, copper recovery rate, and copper recovery purity of Example 2 are further improved on the basis of Example 1. For high-purity silver recovery technology, the improvement of silver recovery purity is a significant improvement.

[0042] In addition, the silver recovery rate, silver recovery purity, copper recovery rate, and copper recovery purity of Example 3 are further improved on the basis of Example 1.

[0043] Therefore, in Examples 2 and 3 of the present application, the silver-copper composite material was pretreated using a hydrogen-nitrogen mixed atmosphere to reduce the non-stoichiometric copper oxide compound at the interface of the silver-copper composite material, thereby reducing the copper lattice defect density at the interface, making the oxygen diffusion channel more uniform, and the oxide layer at the interface more uniform and thinner. After rapid cooling, the stress distribution was more concentrated, the silver and copper were separated more thoroughly after peeling, the amount of copper phase / copper oxide remaining on the silver was reduced, and the recovered purity of the silver was improved.

[0044] Furthermore, a comparison of the data of Examples 2 and 3 shows that the silver-copper composite material was pretreated with a hydrogen-nitrogen mixed atmosphere, which reduced the non-stoichiometric copper oxide compound at the silver-copper interface and effectively shortened the start-up time of the subsequent oxidation reaction. Therefore, the oxidation time of Example 3 was shorter than that of Example 1, and its silver recovery rate and copper recovery rate were higher and similar to those of Example 2.

[0045] Comparing Example 1 and Example 4, although the silver recovery rate and recovery purity and copper recovery rate of Example 4 are greater than those of Comparative Example 1, they are lower than those of Example 1.

[0046] The reasons are: In Example 4, the water cooling efficiency is low, and the difference in thermal expansion coefficients at the copper oxide / copper interface cannot be fully stimulated, resulting in incomplete stress cracking. During water quenching, the high-temperature copper is exposed to air, and a Cu2O / CuO mixed layer is formed on the surface. During mechanical stripping, more silver particles remain on the copper phase, resulting in a decrease in silver recovery rate. Water quenching causes partial dissolution of the copper surface, and copper ions are adsorbed on the silver surface. During rapid cooling, water vapor reacts with silver to produce trace amounts of Ag2O, resulting in a decrease in the purity of silver recovery. The water quenching stress is insufficient, and the bonding force between the oxide layer and the copper matrix is enhanced, resulting in copper oxide remaining in the copper phase and a decrease in the copper recovery rate.

[0047] Therefore, the present application adopts liquid nitrogen cooling, and the recovery rate and purity of the recovered materials are better.

[0048] Comparing Example 1 and Example 5, the silver recovery rate and recovery purity of Example 5 are lower than those of Example 1, and the copper recovery rate and recovery purity of Example 5 are lower than those of Example 1.

[0049] The reason is that Example 5 lacks argon protection, which causes the copper and silver surfaces to oxidize to form silver oxide and copper hydroxide, directly reducing the purity and yield.

[0050] In addition, in Example 1, argon is used. The density of argon is much higher than that of air. A high-density gas layer is formed in the closed chamber to cover the surface of the high-temperature material. During the liquid nitrogen spraying process, the density of nitrogen and argon is close, so there is no drastic density reversal during the nitrogen vaporization process, and the overall airflow is stable. On the other hand, the flowing replacement argon also ensures that the water content in the gas phase in the cabin is low, avoiding the ice crystals produced by the condensation of liquid nitrogen and the instantaneous vaporization of the high-temperature material to produce a micro-explosion effect, thereby reducing the possibility of turbulence during the rapid cooling of the high-temperature material and reducing the loss of copper and silver particles caused by turbulence.

[0051] Therefore, in the present application, argon flow protection is used for the liquid nitrogen spray quenching process, which is beneficial to improving the purity and recovery rate of the recovered materials.

[0052] Example 6 A method for selective interfacial oxidation separation and recovery of silver-copper composite materials is provided, which differs from Example 1 in that the gas phase in the fluidized bed reactor during the oxidation process also includes carbon dioxide, and the molar ratio of carbon dioxide to oxygen is 0.8:1.

[0053] Example 7 A method for selective interfacial oxidation separation and recovery of silver-copper composite materials is provided, which differs from Example 1 in that the gas phase in the fluidized bed reactor during the oxidation process also includes carbon dioxide, and the molar ratio of carbon dioxide to oxygen is 0.9:1.

[0054] Example 8 A method for selective interfacial oxidation separation and recovery of silver-copper composite materials is provided, which differs from Example 1 in that the gas phase in the fluidized bed reactor during the oxidation process also includes carbon dioxide, and the molar ratio of carbon dioxide to oxygen is 0.92:1.

[0055] Example 9 A method for selective interfacial oxidation separation and recovery of silver-copper composite materials is provided, which differs from Example 1 in that the gas phase in the fluidized bed reactor during the oxidation process also includes carbon dioxide, and the molar ratio of carbon dioxide to oxygen is 0.95:1.

[0056] Example 10 A method for selective interfacial oxidation separation and recovery of silver-copper composite materials is provided, which differs from Example 1 in that the gas phase in the fluidized bed reactor during the oxidation process also includes carbon dioxide, and the molar ratio of carbon dioxide to oxygen is 1.1:1.

[0057] Example 11 A method for selective interfacial oxidation separation and recovery of silver-copper composite materials, which differs from Example 1 in that the gas phase in the fluidized bed reactor also contains ozone during the oxidation process, the ozone content is 0.2 vol%, the oxidation time is 40 h, and the oxidation temperature is 450°C.

[0058] Example 12 A method for selective interfacial oxidation separation and recovery of silver-copper composite materials, which differs from Example 1 in that the gas phase in the fluidized bed reactor also contains ozone during the oxidation process, the ozone content is 1 vol%, the oxidation time is 40 h, and the oxidation temperature is 450°C.

[0059] Example 13 A method for selective interfacial oxidation separation and recovery of silver-copper composite materials, which differs from Example 1 in that the gas phase in the fluidized bed reactor also contains ozone during the oxidation process, the ozone content is 2.8 vol%, the oxidation time is 40 h, and the oxidation temperature is 450°C.

[0060] Example 14 A method for selective interfacial oxidation separation and recovery of silver-copper composite materials, which differs from Example 1 in that the gas phase in the fluidized bed reactor also contains ozone during the oxidation process, the ozone content is 3 vol%, the oxidation time is 40 h, and the oxidation temperature is 450°C.

[0061] Example 15 A method for selective interfacial oxidation separation and recovery of silver-copper composite materials, which differs from Example 1 in that the gas phase in the fluidized bed reactor also contains ozone during the oxidation process, the ozone content is 6 vol%, the oxidation time is 40 h, and the oxidation temperature is 450°C.

[0062] The recovery rate and purity of the recovered silver and copper obtained in Examples 6 to 15 were tested, and the test results are shown in Table 2 below.

[0063] Table 2. Recovery and purity test results of Examples 6 to 15

[0064] In combination with Table 1 and Table 2, comparing Example 1 and Example 8, the silver recovery rate, silver purity, copper recovery rate, and copper purity of Example 8 are all improved compared with Example 1. This is because a specific proportion of carbon dioxide is also added to the atmosphere during the oxidation process in Example 8. Carbon dioxide can react with cuprous oxide at high temperature to consume oxygen vacancies on the copper surface, making the oxide layer formed on the copper denser, reducing the thickness of the oxide layer, improving the retention rate of copper metal, and avoiding the problem of incomplete stripping due to local overoxidation, thereby further improving the recovery rate and purity of silver.

[0065] In addition, in combination with Examples 6 to 10, the purity and recovery rate of the recycled materials in Examples 7 to 9 are better than those in Examples 6 and 10, and Example 8 is the best. Therefore, in this application, when carbon dioxide is added to the gas phase during oxidation, the molar ratio of carbon dioxide to oxygen is 0.9 to 0.95:1, which is the best.

[0066] Comparing Example 1 and Example 13, the silver recovery rate, silver purity, copper purity, and copper recovery rate of Example 13 are all improved compared with Example 1, and the oxidation time of Example 13 is significantly reduced compared with Example 1 and Example 8, and the oxidation temperature is lowered; It can be seen from this that the present application adds ozone to the gas phase during the oxidation stage, which can utilize its high oxidation potential to trigger copper interface oxidation faster at a lower temperature to shorten the oxidation time, and inhibit silver oxidation in a low-temperature environment, taking into account both speed and selectivity, and is more suitable for high-speed and large-scale industrial production needs.

[0067] Compared with Examples 11 to 15, the ozone concentrations of Examples 11 to 15 are gradually increased. Combined with their data, the recovery rates and recovery purities of Examples 12 to 14 are better than those of Examples 11 and 15.

[0068] The recovery rate and recovery purity of Example 15 actually decreased in the opposite direction compared with Example 14. The reason is that the ozone concentration is too high, which not only accelerates the oxidation rate of copper, but also strengthens the oxidation of silver, resulting in selective destruction, and the loss of the advantage of preferential oxidation of copper, resulting in a decrease in the recovery rate and purity of copper and silver.

[0069] Therefore, in this application, the optimal ozone concentration in the gas phase during oxidation is 1-3 vol%.

[0070] In addition, this application has other preferred embodiments, such as embodiments 16 to 18.

[0071] Example 16 A method for selective interfacial oxidation separation and recovery of silver-copper composite materials is provided, which differs from Example 1 in that the temperature in the oxidation stage is between 400° C., the oxygen pressure is 0.6 MPa, and the reaction time is 60 h.

[0072] Example 17 A method for selective interfacial oxidation separation and recovery of silver-copper composite materials is provided, which differs from Example 1 in that the temperature in the oxidation stage is between 700° C., the oxygen pressure is 0.2 MPa, and the reaction time is 20 h.

[0073] Example 18 A method for selective interfacial oxidation separation and recovery of a silver-copper composite material, which differs from Example 1 in that the copper strip of the silver-copper composite material is high-purity copper with a purity greater than 99.5wt%; the silver strip is a silver-nickel alloy with a nickel content of 5wt% and the remainder being silver and unavoidable impurities.

[0074] Example 19 A method for selective interfacial oxidation separation and recovery of a silver-copper composite material, which differs from Example 1 in that the copper strip of the silver-copper composite material is high-purity copper with a purity greater than 99.5wt%; the silver strip is a silver tin oxide material, wherein the tin oxide content is 12wt%, and the remainder is silver and unavoidable impurities.

[0075] The recycled materials of Examples 16 to 19 were tested, and the test results are shown in Tables 3 and 4 below.

[0076] Silver content in silver base = silver content in recovered silver ingots, expressed as mass percentage (for composite silver-based materials).

[0077] Nickel content in silver base = nickel content in recovered silver ingots, expressed as a percentage of nickel by mass (for nickel-containing composite silver-based materials).

[0078] Tin content in silver base = tin content in recovered silver ingots, expressed as a percentage of tin by mass (for composite silver-based materials containing tin oxide).

[0079] Table 3. Test results of Examples 16 to 17

[0080] Table 4. Test results of Examples 18 to 19

[0081] Combining Table 1, Table 3, and Table 4, It can be seen from Examples 1 and 16 to 17 that in the process method of the present application, as the reaction temperature increases, the oxygen pressure increases and the corresponding reaction time can be shortened. When the oxidation temperature decreases and the oxygen pressure decreases, the corresponding reaction time needs to be extended. The final parameters control the temperature of the oxidation stage to be between 400 and 700°C, the oxygen pressure to be between 0.2 and 0.6 MPa, and the reaction time to be between 20 and 60 hours.

[0082] In combination with Examples 18 to 19, it can be seen that the recovered silver component is determined by the silver material components in the crushed material. The present application is not only aimed at the recovery of high-purity silver for silver materials, but also can be aimed at silver alloys or silver-based materials, such as pure silver, fine-grained silver, silver-cerium, silver-copper, silver-iron, silver-nickel, silver-magnesium-nickel and other silver alloys or silver-based materials such as silver cadmium oxide, silver copper oxide, silver zinc oxide, silver tin oxide, silver tin oxide indium oxide, etc.

[0083] This specific embodiment is merely an explanation of the present invention and is not a limitation of the present invention. After reading this specification, those skilled in the art may make non-creative modifications to this embodiment as needed. However, as long as the modifications are within the scope of protection required by the present invention, they will be protected by patent law.

Claims

1. A method for selective interfacial oxidation separation and recovery of silver-copper composite materials, characterized in that: The following steps are involved: Crushing and shearing the material to obtain crushed material; The crushed material is pre-treated and sent to the oxidation fluidized bed for internal oxidation reaction in the gas phase at 400-700°C and oxygen pressure of 0.2-0.6 MPa for 20-60 hours to obtain high-temperature material; The high-temperature material is rapidly cooled to generate stress cracks at the oxidation interface to obtain a cooled material; The cooled material is placed under mechanical action for stripping to obtain recovered copper material and recovered silver material.

2. The method for selective interfacial oxidation separation and recovery of silver-copper composite materials according to claim 1, characterized in that: The following steps are also included: The recycled copper and silver materials are placed separately in a furnace, embedded with graphite powder or carbon powder, and then smelted, refined and impurity-removed at high temperature to obtain recycled silver ingots and recycled copper ingots.

3. The method for selective interfacial oxidation separation and recovery of silver-copper composite materials according to claim 1, characterized in that: The gas phase in the oxidation fluidized bed also includes carbon dioxide, and the molar ratio of carbon dioxide to oxygen is 0.9-0.95:

1.

4. The method for selective interfacial oxidation separation and recovery of silver-copper composite materials according to claim 1, characterized in that: The gas phase in the oxidation fluidized bed also includes ozone, and the content of ozone is 1-3 vol%.

5. The method for selective interfacial oxidation separation and recovery of silver-copper composite materials according to claim 1, characterized in that: The pretreatment comprises placing the crushed material in a reducing fluidized bed, using a mixed gas of hydrogen and nitrogen at 400° C. to remove impurity oxygen atoms at the interface of the silver-copper composite material.

6. The method for selective interfacial oxidation separation and recovery of silver-copper composite materials according to claim 5, characterized in that: The hydrogen content in the mixed gas of hydrogen and nitrogen is 2 vol%, and the treatment time is 10-11 minutes.

7. The method for selective interfacial oxidation separation and recovery of silver-copper composite materials according to claim 1, characterized in that: The rapid cooling method adopts spraying liquid nitrogen to the high-temperature material, and the contact time of the spraying liquid nitrogen is controlled to be 3-5 seconds.

8. The method for selective interfacial oxidation separation and recovery of silver-copper composite materials according to claim 7, characterized in that: During the liquid nitrogen spraying, the high-temperature material is in a closed cabin, and argon gas is continuously introduced to replace the atmosphere in the cabin.

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