Method for recovering tin-antimony sludge

Abstract

The application discloses a tin-antimony mud recycling method, which comprises the following steps: step S1, tin-antimony mud ball milling, tin-antimony mud is ball milled in pure water and is subjected to a filtering and drying procedure to obtain tin-antimony mixed powder; step S2, carbon particle mixing, tin-antimony mixed powder obtained in step S1 is mixed with carbon particles to form mixed powder of tin-antimony mixed powder and carbon particles; step S3, acid atmosphere heating, the mixed powder of tin-antimony mixed powder and carbon particles obtained in step S2 is subjected to a heating reaction under an acid atmosphere, and after the heating reaction, a heat preservation and cooling process is performed; step S4, sieving, the mixture obtained in step S3 is sieved, the powder falling through the sieve is a lithium battery negative electrode inert metal mixture, and the powder obtained on the sieve is a tin-antimony-bismuth-carbon composite powder; the tin-antimony-bismuth-carbon composite powder comprises carbon particles with tin-antimony-bismuth oxide particles attached; the tin-antimony-bismuth-carbon composite powder is used for lithium ion battery negative electrode material; and the application can efficiently recycle tin-antimony mud.

Description

Technical Field

[0001] This invention relates to the field of tin-containing waste recycling, and more particularly to the field of methods for recycling tin-antimony sludge. Background Technology

[0002] Antimony is a common impurity in tin smelting. There are many methods for recovering metals from tin-antimony sludge, such as using a segmented carbothermal reduction method to volatilize antimony from the sludge, which has a high antimony removal rate, but requires large investment in vacuum equipment and has a small processing capacity. Another method is to recover valuable metals by distillation in a vacuum furnace based on the difference in metal boiling points. Although this method can recover tin and antimony separately, it has high energy consumption and low profitability. Another method is to use chemical methods to extract tin and antimony through acid leaching, followed by distribution replacement of tin and antimony. This method generates a large amount of wastewater containing heavy metals, and the method is gradually losing its application value. Therefore, the current approach to recovering valuable metals from tin-antimony sludge is to try to obtain elemental metals, such as tin, from the separation perspective, so that they can be used as raw materials for other industries. Summary of the Invention

[0003] To address the problems existing in the prior art, the present invention provides a method for recovering tin-antimony sludge, which includes the following steps:

[0004] Step S1: Ball milling of tin-antimony sludge. The tin-antimony sludge is ball milled in pure water and then filtered and dried to obtain tin-antimony mixed powder. Ball milling can break up agglomerated particles, making it easier to mix with carbon particles later. At the same time, it shortens the reaction time of the subsequent heating process. Because in the heating process of step S3, the contact between tin-antimony-bismuth particles and carbon tubes is a physical process. The finer the particles, the larger the effective contact area between tin-antimony-bismuth and carbon tubes, which is more conducive to the adhesion of tin-antimony-bismuth melt to the surface of carbon tubes. Overall, it also improves the recovery rate of tin-antimony-carbon composite powder. The filtration process can remove some water-soluble organic or inorganic impurities.

[0005] Step S2: Carbon particle mixing. The tin-antimony mixed powder obtained in step S1 is mixed with carbon particles to form a mixed powder of tin-antimony mixed powder and carbon particles. This step is to make the carbon particles and tin-antimony mixed powder as uniform as possible, thereby further increasing the effective contact area between the tin-antimony-bismuth melt and the carbon tube in step S3, thereby improving the efficiency of step S3.

[0006] Step S3: Heating in an acidic atmosphere. The tin-antimony mixture obtained in step S2 is heated and reacted with the carbon particles in an acidic atmosphere. After the reaction, a heat preservation and cooling process is performed. This step is carried out at a preset temperature, which is higher than the melting point of metallic tin but lower than the melting point of the inert metal of the lithium battery negative electrode in the tin-antimony mud. At this preset temperature, the principle of the reaction process is as follows: After heating in an acidic atmosphere, the oxide film on the surface of the metal or alloy in the tin-antimony mud breaks down. At the same time, the oxygen content is very low in the acidic atmosphere, and the tin, antimony, and bismuth in the tin-antimony mud melt to form a melt. The melt comes into contact with the carbon particles (at this time, the acidic atmosphere acts like a flux, but due to the absence of a surfactant, the acidic atmosphere has a weak ability to reduce the surface tension of the melt on the carbon particles. Stirring can make the melt contact the carbon particles but will not cause the melt to agglomerate on the surface of the carbon particles. At the same time, the presence of carbon particles also prevents the melt from self-agglomerating). As the acidic atmosphere disappears, oxygen begins to contact the melt, causing the edges of the melt in contact with the carbon particles to oxidize and form oxides or alloy oxides of tin, antimony, and bismuth. (Oxides of tin, antimony, and bismuth, as well as oxides of alloys between tin, antimony, and bismuth, can all be used as negative electrodes in lithium-ion batteries.) The generated tin oxide solidifies on the surface of the carbon particles. Due to the absence of the acidic atmosphere, the surface tension of the melt on the carbon particle surface increases, causing the melt on the carbon particle surface to tend to shrink and agglomerate. This shrinkage and agglomeration occurs simultaneously with the solidification process of the melt on the carbon particle surface, ultimately resulting in a large number of fine oxide particles solidified on the carbon particle surface. The inventors further discovered that as the volume of the carbon particles decreases, the oxide particles solidified on the carbon particle surface also become correspondingly finer and more uniform. If the carbon particle size reaches the micrometer or nanometer level, most of the oxide particles solidified on the carbon particle surface will also become nanoparticles. The role of stirring is twofold: firstly, to ensure more thorough contact between the melt and the carbon particles, allowing a large amount of melt to adhere to the carbon particle surface; and secondly, to prevent excessive self-agglomeration of the melt.

[0007] Step S4: Sieving. The mixture obtained in step S3 is sieved. The powder component that passes through is a mixture of inert metals for lithium battery negative electrodes, while the powder component obtained on the sieve is tin-antimony-bismuth-carbon composite powder. The tin-antimony-bismuth-carbon composite powder includes carbon particles with tin-antimony-bismuth oxide particles attached. The tin-antimony-bismuth-carbon composite powder is used as a negative electrode material for lithium-ion batteries.

[0008] The sieve size used in step S4 is between the median particle size of the carbon particles and the median particle size of the tin-antimony mixed powder obtained in step S1.

[0009] The median particle size of the tin-antimony mixed powder obtained by ball milling in step S1 is less than 10 μm, and the median particle size of the carbon particles is greater than 50 μm.

[0010] The carbon particles include carbon nanotubes, and multi-walled carbon nanotubes are preferred in this application.

[0011] The mixing process in step S2 is carried out using a powder mixer in a fume hood because carbon particles and tin-antimony mud metal powder are difficult to break down in the respiratory system when the particles are very small, which can easily cause respiratory diseases.

[0012] The heating process in step S3 is carried out at a preset temperature, which is higher than the melting point of metallic tin but lower than the ignition point of carbon nanotubes. The metal composition and content in the tin-antimony mud can be determined by X-ray fluorescence spectroscopy.

[0013] The preset temperature range is between 450°C and 500°C. The ignition point of the carbon tube is greater than 600°C. The more surface defects the carbon tube has, the lower the ignition point. Carbon tubes with fewer surface defects are preferred, so that the ignition point of the carbon tube can be greater than 600°C, and some carbon tubes can even reach 700°C or higher. Although the melting point of antimony metal is 630°C, due to the ball milling process in step S2, the size of the antimony particles is less than 10 μm. In tin-antimony mud, antimony mostly exists in the form of tin-antimony alloy. These factors combined result in the melting point of the antimony particles being lower than 450°C. Under this heating temperature range, the inert metal of the lithium battery negative electrode will not melt and will still exist as micron-sized powder.

[0014] The heat preservation and cooling process in step S3 is carried out in an air or oxygen atmosphere. Specifically, hydrogen chloride gas is introduced during the heating process, and when the temperature rises to the preset temperature, the supply of hydrogen chloride gas is stopped and replaced with the supply of air or oxygen.

[0015] The acidic atmosphere in step S3 can be achieved by premixing tin tetrachloride pentahydrate in step S2. Since tin tetrachloride pentahydrate generates hydrogen chloride gas during heating and tin dioxide is eventually generated during preheating, it will not interfere with the final tin dioxide.

[0016] The heating process, heat preservation process, and cooling process in step S3 are all accompanied by a stirring process.

[0017] The advantages of the method disclosed in this invention are as follows: This application changes the existing approach of attempting to separate metals from tin-antimony mud. It takes a holistic approach and utilizes the characteristics of tin, antimony, bismuth and other metals in tin-antimony mud as lithium battery anode materials. It comprehensively recovers the metals in tin-antimony mud to produce tin-antimony-bismuth and carbon composite materials for lithium-ion battery anodes, thereby achieving high-value utilization of waste. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below.

[0019] Figure 1 This is a schematic diagram of the method described in this application.

[0020] Figure 2 The image shows a scanning electron microscope (SEM) image of the tin-antimony-bismuth-carbon composite powder obtained after sieving in step S4.

[0021] Figure 3 Cyclic graph of negative electrode capacity measured after tin-antimony-bismuth-carbon composite powder was fabricated into a button-shaped lithium-ion battery. Detailed Implementation

[0022] The present invention will be further described in detail below with reference to specific embodiments. The terms "low-immersion" or "secondary low-immersion" in the present invention have the same meaning, as do "precision filtration solution" or "precision filtration solution". Unless otherwise specified in the following embodiments, the ratios between the components are mass ratios.

[0023] Existing tin-antimony sludge has a complex composition, but it generally contains metals such as tin, antimony, copper, and bismuth, with high levels of tin and antimony. The following table shows the compositional analysis of an existing type of tin-antimony sludge:

[0024]

[0025] The table above shows that tin has a melting point of 232 degrees Celsius, and its theoretical capacity as a negative electrode in lithium-ion batteries is 990 mAh / g.

[0026] Antimony has a melting point of 630 degrees Celsius, and its theoretical capacity as a negative electrode in lithium-ion batteries is 660 mAh / g.

[0027] Bismuth has a melting point of 271 degrees Celsius, and its theoretical capacity as a negative electrode in lithium-ion batteries is 3765 mAh / g.

[0028] Copper has a melting point of 1083 degrees Celsius, silver has a melting point of 962 degrees Celsius, and gold has a melting point of 1064 degrees Celsius. Copper, gold, and silver cannot be used as negative electrodes in lithium-ion batteries. In this application, metals that cannot be used as active materials for negative electrodes in lithium-ion batteries are designated as inert metals for negative electrodes in lithium batteries.

[0029] To address the problems existing in the prior art, the present invention provides a method for recovering tin-antimony sludge, which includes the following steps:

[0030] Step S1: Ball milling of tin-antimony sludge. The tin-antimony sludge is ball milled in pure water and then filtered and dried to obtain tin-antimony mixed powder. Ball milling can break up agglomerated particles, making it easier to mix with carbon particles later. At the same time, it shortens the reaction time of the subsequent heating process. Because in the heating process of step S3, the contact between tin-antimony-bismuth particles and carbon tubes is a physical process. The finer the particles, the larger the effective contact area between tin-antimony-bismuth and carbon tubes, which is more conducive to the adhesion of tin-antimony-bismuth melt to the surface of carbon tubes. Overall, it also improves the recovery rate of tin-antimony-carbon composite powder. The filtration process can remove some water-soluble organic or inorganic impurities.

[0031] Step S2: Carbon particle mixing. The tin-antimony mixed powder obtained in step S1 is mixed with carbon particles to form a mixed powder of tin-antimony mixed powder and carbon particles. This step is to make the carbon particles and tin-antimony mixed powder as uniform as possible, thereby further increasing the effective contact area between the tin-antimony-bismuth melt and the carbon tube in step S3, thereby improving the efficiency of step S3.

[0032] Step S3: Heating in an acidic atmosphere. The tin-antimony mixture obtained in step S2 is heated and reacted with the carbon particles in an acidic atmosphere. After the reaction, a heat preservation and cooling process is performed. This step is carried out at a preset temperature, which is higher than the melting point of metallic tin but lower than the melting point of the inert metal of the lithium battery negative electrode in the tin-antimony mud. At this preset temperature, the principle of the reaction process is as follows: After heating in an acidic atmosphere, the oxide film on the surface of the metal or alloy in the tin-antimony mud breaks down. At the same time, the oxygen content is very low in the acidic atmosphere, and the tin, antimony, and bismuth in the tin-antimony mud melt to form a melt. The melt comes into contact with the carbon particles (at this time, the acidic atmosphere acts like a flux, but due to the absence of a surfactant, the acidic atmosphere has a weak ability to reduce the surface tension of the melt on the carbon particles. Stirring can make the melt contact the carbon particles but will not cause the melt to agglomerate on the surface of the carbon particles. At the same time, the presence of carbon particles also prevents the melt from self-agglomerating). As the acidic atmosphere disappears, oxygen begins to contact the melt, causing the edges of the melt in contact with the carbon particles to oxidize and form oxides or alloy oxides of tin, antimony, and bismuth. (Oxides of tin, antimony, and bismuth, as well as oxides of alloys between tin, antimony, and bismuth, can all be used as negative electrodes in lithium-ion batteries.) The generated tin oxide solidifies on the surface of the carbon particles. Due to the absence of the acidic atmosphere, the surface tension of the melt on the carbon particle surface increases, causing the melt on the carbon particle surface to tend to shrink and agglomerate. This shrinkage and agglomeration occurs simultaneously with the solidification process of the melt on the carbon particle surface, ultimately resulting in a large number of fine oxide particles solidified on the carbon particle surface. The inventors further discovered that as the volume of the carbon particles decreases, the oxide particles solidified on the carbon particle surface also become correspondingly finer and more uniform. If the carbon particle size reaches the micrometer or nanometer level, most of the oxide particles solidified on the carbon particle surface will also become nanoparticles. The role of stirring is twofold: firstly, to ensure more thorough contact between the melt and the carbon particles, allowing a large amount of melt to adhere to the carbon particle surface; and secondly, to prevent excessive self-agglomeration of the melt.

[0033] Step S4: Sieving. The mixture obtained in step S3 is sieved. The powder component that passes through is a mixture of inert metals for lithium battery negative electrodes, while the powder component obtained on the sieve is tin-antimony-bismuth-carbon composite powder. The tin-antimony-bismuth-carbon composite powder includes carbon particles with tin-antimony-bismuth oxide particles attached. The tin-antimony-bismuth-carbon composite powder is used as a negative electrode material for lithium-ion batteries.

[0034] The sieve size used in step S4 is between the median particle size of the carbon particles and the median particle size of the tin-antimony mixed powder obtained in step S1.

[0035] The median particle size of the tin-antimony mixed powder obtained by ball milling in step S1 is less than 10 μm, and the median particle size of the carbon particles is greater than 50 μm.

[0036] The carbon particles include carbon nanotubes, and multi-walled carbon nanotubes are preferred in this application.

[0037] The mixing process in step S2 is carried out using a powder mixer in a fume hood because carbon particles and tin-antimony mud metal powder are difficult to break down in the respiratory system when the particles are very small, which can easily cause respiratory diseases.

[0038] The heating process in step S3 is carried out at a preset temperature, which is higher than the melting point of metallic tin but lower than the ignition point of carbon nanotubes. The metal composition and content in the tin-antimony mud can be determined by X-ray fluorescence spectroscopy.

[0039] The preset temperature range is between 450°C and 500°C. The ignition point of the carbon tube is greater than 600°C. The more surface defects the carbon tube has, the lower the ignition point. Carbon tubes with fewer surface defects are preferred, so that the ignition point of the carbon tube can be greater than 600°C, and some carbon tubes can even reach 700°C or higher. Although the melting point of antimony metal is 630°C, due to the ball milling process in step S2, the size of the antimony particles is less than 10 μm. In tin-antimony mud, antimony mostly exists in the form of tin-antimony alloy. These factors combined result in the melting point of the antimony particles being lower than 450°C. Under this heating temperature range, the inert metal of the lithium battery negative electrode will not melt and will still exist as micron-sized powder.

[0040] The heat preservation and cooling process in step S3 is carried out in an air or oxygen atmosphere. Specifically, hydrogen chloride gas is introduced during the heating process, and when the temperature rises to the preset temperature, the supply of hydrogen chloride gas is stopped and replaced with the supply of air or oxygen.

[0041] The acidic atmosphere in step S3 can be achieved by premixing tin tetrachloride pentahydrate in step S2. Since tin tetrachloride pentahydrate generates hydrogen chloride gas during heating and tin dioxide is eventually generated during preheating, it will not interfere with the final tin dioxide.

[0042] The heating process, heat preservation process, and cooling process in step S3 are all accompanied by a stirring process.

[0043] To further illustrate this application, the following preferred embodiments are disclosed: Example

[0044] The median particle size of the tin-antimony mud obtained after ball milling and drying in step S1 is 5 micrometers.

[0045] The carbon particles used in step S2 are graphite particles, and the median particle size of the graphite particles used is about 40 micrometers.

[0046] In step S3, an acidic atmosphere is provided by mixing tin tetrachloride pentahydrate. Specifically, tin tetrachloride pentahydrate is pre-mixed in step S2, or added at the beginning of heating in step S3. The amount of tin tetrachloride pentahydrate added accounts for 0.1%-1% of the tin-antimony mud. After heating, since the amount of tin tetrachloride pentahydrate is relatively small, it will decompose completely during the heating process. Therefore, there is no need to supply air or oxygen in the subsequent heat preservation and cooling stages. It is only necessary to keep the temperature and cool down in an open environment. At the same time, stirring is continuously carried out during the heat preservation and cooling process.

[0047] The sieve used in step S4 has a mesh size of 20 micrometers; the powder obtained on the sieve is a tin-antimony-bismuth-carbon composite powder; the tin-antimony-bismuth-carbon composite powder includes graphite particles with tin-antimony-bismuth oxide particles attached; the tin-antimony-bismuth-carbon composite powder is used as a negative electrode material for lithium-ion batteries.

[0048] Figure 2 The image shows a scanning electron microscope (SEM) image of the tin-antimony-bismuth-carbon composite powder obtained after sieving in step S4. The image clearly shows relatively uniformly attached nanoscale particles on the graphite surface. These particles are tin-antimony-bismuth oxide particles. Looking at the overall tin-antimony-bismuth-carbon composite powder, tin-antimony-bismuth oxide exists in various forms, including tin oxide, antimony oxide, bismuth oxide, and alloy oxides formed between tin, antimony, and bismuth. The fundamental reason is that this method is a physical process, relying on contact to achieve the reaction of oxides. Compared to chemical methods, it is more difficult to form a uniform substance. However, during electrochemical charge-discharge processes, these various forms of tin-antimony-bismuth oxide can all provide electrochemical lithium storage, meaning they all have electrochemical capacity. Graphite itself is currently the most widely used electrochemical anode material, with a theoretical capacity of 372 mAh / g.

[0049] Figure 3 The negative electrode capacity measured after the tin-antimony-bismuth-carbon composite powder was made into a button-shaped lithium-ion battery shows that the capacity of the tin-antimony-bismuth-carbon composite powder reaches 450-500mAh / g and can be stably cycled for more than 100 cycles. Compared with the existing commercial graphite negative electrode system, the capacity is greatly improved. If it is commercialized, it will greatly alleviate the capacity anxiety problem of existing lithium batteries.

[0050] The advantages of the method disclosed in this invention are as follows: This application changes the existing approach of attempting to separate metals from tin-antimony mud. It takes a holistic approach and utilizes the characteristics of tin, antimony, bismuth and other metals in tin-antimony mud as lithium battery anode materials. It comprehensively recovers the metals in tin-antimony mud to produce tin-antimony-bismuth and carbon composite materials for lithium-ion battery anodes, thereby achieving high-value utilization of waste.

Claims

1. A method for recovering tin-antimony sludge, characterized in that, The method includes the following steps: Step S1: Ball milling of tin-antimony mud. The tin-antimony mud is ball milled in pure water and then filtered and dried to obtain tin-antimony mixed powder. Step S2: Carbon particle mixing. The tin-antimony mixed powder obtained in step S1 is mixed with carbon particles to form a mixed powder of tin-antimony mixed powder and carbon particles. Step S3: Heating in an acidic atmosphere. The tin-antimony mixed powder and carbon particles obtained in step S2 are heated and reacted in an acidic atmosphere. After the heating reaction, a heat preservation and cooling process is carried out. The heating process in step S3 is carried out at a preset temperature, which is higher than the melting point of metallic tin but lower than the melting point of the inert metal of the lithium battery negative electrode in the tin-antimony mud. The heat preservation and cooling process in step S3 is carried out in an air or oxygen atmosphere. Step S4: Sieving. The mixture obtained in step S3 is sieved. The powder component that passes through is a mixture of inert metals for lithium battery negative electrodes, while the powder component obtained on the sieve is tin-antimony-bismuth-carbon composite powder. The tin-antimony-bismuth-carbon composite powder includes carbon particles with tin-antimony-bismuth oxide particles attached. The tin-antimony-bismuth-carbon composite powder is used as a negative electrode material for lithium-ion batteries.

2. The method for recovering tin-antimony sludge according to claim 1, characterized in that, The sieve size used in step S4 is between the median particle size of the carbon particles and the median particle size of the tin-antimony mixed powder obtained in step S1.

3. The method for recovering tin-antimony sludge according to claim 2, characterized in that, The median particle size of the tin-antimony mixed powder obtained by ball milling in step S1 is less than 10 μm, and the median particle size of the carbon particles is greater than 50 μm.

4. The method for recovering tin-antimony sludge according to claim 3, characterized in that, The carbon particles include carbon nanotubes.

5. The method for recovering tin-antimony sludge according to claim 4, characterized in that, The mixing process in step S2 is carried out using a powder mixer.

6. The method for recovering tin-antimony sludge according to claim 3, characterized in that, The metal composition and content in the tin-antimony mud can be determined by X-ray fluorescence spectroscopy.

7. The method for recovering tin-antimony sludge according to claim 4, characterized in that, The preset temperature range is between 450°C and 500°C, and the carbon tube ignition point is greater than 600°C.

8. The method for recovering tin-antimony sludge according to claim 7, characterized in that, The acidic atmosphere in step S3 can be achieved by premixing tin tetrachloride pentahydrate in step S2.

9. A method for recovering tin-antimony sludge according to claim 1, characterized in that, The heating process, heat preservation process, and cooling process in step S3 are all accompanied by a stirring process.

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