Method for cleaning and reprocessing of waste chrome tannery shavings and resource utilization and application thereof

Abstract

The application discloses a method for cleaning and reprocessing and resource utilization of waste chrome tanning scraps and application thereof, and belongs to the technical field of solid waste resource utilization. The method is to use a citric acid-EDTA composite cleaning agent to clean and process the leather scraps and separate chromium; a composite enzyme preparation is used to enzymatically hydrolyze the chromium-removed leather residue under high temperature and high pressure to extract collagen; the chromium-containing filtrate is alkalized, precipitated and calcined to recover chromium trioxide; and finally, the enzymatically hydrolyzed residue is blended with a thermoplastic polymer to extrude plastic fillers. The application realizes efficient recovery of chromium and efficient extraction of collagen, and the process is clean and environmentally friendly, without toxic and harmful emissions, so that full-component and high-value utilization of the waste is achieved.

Description

Technical Field

[0001] This invention belongs to the field of solid waste resource utilization technology, specifically the method and application of clean reprocessing and resource utilization of waste chrome tanned leather scraps. Background Technology

[0002] The leather industry generates a large amount of solid waste during production, among which waste chrome-tanned leather scraps account for a very high proportion. These waste chrome-tanned leather scraps contain rich collagen and also retain a certain amount of chromium, making them highly valuable for resource utilization.

[0003] However, existing methods for the resource utilization of waste chrome-tanned leather scraps have significant shortcomings. Currently, some technologies use chemical reagents such as acids and alkalis to treat waste chrome-tanned leather scraps to extract collagen. For example, Chinese invention patent application CN108570105A discloses an acid-based dechromic acid process using a mixed solution of oxalic acid and sulfuric acid. Although the reaction temperature is low, chromium loss is easily caused during the process, reducing the chromium recovery rate and potentially causing secondary pollution. Furthermore, the collagen extracted by these methods has low purity and poor performance, making it difficult to meet the production requirements of high-value-added products. The technology disclosed in Chinese invention patent application CN110904287B uses an alkaline swelling combined with enzymatic hydrolysis process. While it can simultaneously prepare industrial-grade collagen and chrome tannin retanning agents, the process route is lengthy, involving multiple pH adjustments and temperature controls, making operation complex and energy-intensive. These reprocessing technologies are complex, energy-intensive, and expensive, hindering large-scale industrial application.

[0004] Therefore, developing a clean, efficient, and low-cost technology for the reprocessing and resource utilization of waste chrome-tanned leather scraps has become a key issue that needs to be addressed in the leather industry and the environmental protection field. Summary of the Invention

[0005] The purpose of this invention is to provide a method for the clean reprocessing and resource utilization of waste chrome-tanned leather scraps and its application, so as to achieve precise control over the process.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for the clean reprocessing and resource utilization of waste chrome-tanned leather scraps includes the following steps performed sequentially: S1. Cleaning treatment: Take waste chrome tanned leather scraps and add them to the compound cleaning agent at a solid-liquid ratio of 1:8~12. Mix continuously for 2~4 hours, wash, and separate the filtrate and filter residue. S2. Collagen extraction: Take the filter residue and add water at a solid-liquid ratio of 1:10~15, then add 0.5~1.5% of the compound enzyme preparation by weight of the filter residue, and after high-temperature enzymatic hydrolysis, separate the supernatant and residue. The supernatant is freeze-dried to obtain collagen powder. S3. Chromium recovery: Adjust the pH of the filtrate to alkaline, let it stand, and calcine the precipitate obtained by filtration to obtain chromium trioxide. The remaining liquid is concentrated and crystallized to obtain sodium citrate. S4. Residue Recycling: The residue is extruded with a thermoplastic polymer substrate to obtain a plastic filler; The composite cleaning agent is composed of 2-5% citric acid, 1-3% disodium ethylenediaminetetraacetate, and the remainder water by mass. The compound enzyme preparation consists of protease and lipase in a mass ratio of 3 to 5:1.

[0007] Furthermore, the waste chrome-tanned leather scraps are obtained by taking waste chrome-tanned leather, removing impurities, crushing it to a particle size of 1-5 mm, and drying it.

[0008] As a limitation of the present invention, continuous mixing is carried out at 50~70°C and a stirring speed of 200~300 r / min.

[0009] As another limitation of the present invention, in step S1, the washing is performed until the pH of the washing solution is 6-7.

[0010] Furthermore, the high-temperature enzymatic hydrolysis reaction is carried out at a temperature of 60~100℃, a pressure of 0.1~0.2MPa, a rotation speed of 150~250r / min, and a reaction time of 3~5 h.

[0011] Furthermore, the supernatant is first concentrated under reduced pressure and then freeze-dried.

[0012] Furthermore, the calcination temperature is 500~600℃, and the calcination time is 3~5h.

[0013] As another limitation of the present invention, the mass ratio of the residue to the thermoplastic polymer substrate is 5:3; The thermoplastic polymer substrate includes at least one of polyethylene, polypropylene, polybutene, polyisobutylene, and ethylene-vinyl acetate copolymer.

[0014] As a further limitation of the present invention, the residue is dried, mixed with a thermoplastic polymer substrate and a plasticizer at a mass ratio of 5:3:2, and extruded at 150~180℃ and 10~15r / min.

[0015] The present invention also provides an application of the above-mentioned method for the clean reprocessing and resource utilization of waste chrome-tanned leather scraps in the preparation of collagen powder, chromium trioxide powder, sodium citrate crystals or plastic fillers.

[0016] By adopting the above technical solution, the technical progress achieved by this invention compared with the prior art is as follows: The present invention provides a method for the clean reprocessing and resource utilization of waste chrome-tanned leather scraps. Through a clean treatment process, chromium is gently removed using a composite cleaning agent, and the filtrate and residue are separated. Subsequent processes fully utilize both the filtrate and residue, respectively extracting collagen through compound enzymatic hydrolysis and recovering chromium through alkaline precipitation to obtain sodium citrate. The residue is reused by preparing plastic fillers. This integrated technical solution achieves the full-component, high-value, and clean resource utilization of waste chrome-tanned leather scraps.

[0017] Specifically, the method for the clean reprocessing and resource utilization of waste chrome-tanned leather scraps of the present invention uses a composite cleaning agent to clean the waste chrome-tanned leather scraps, which can effectively remove impurities and some residual chromium elements from the surface of the waste chrome-tanned leather scraps. Moreover, the composite cleaning agent has a mild composition and will not damage collagen. At the same time, the chromium element in the filtrate is recovered by adjusting the pH value. The chromium element recovery rate can reach more than 90%, realizing the efficient recycling of chromium element and avoiding chromium pollution to the environment. The present invention provides a method for the clean reprocessing and resource utilization of waste chrome-tanned leather scraps. This method employs high-pressure enzymatic hydrolysis to extract collagen. The use of a compound enzyme preparation can efficiently decompose collagen in the chrome-tanned leather scraps. High-pressure conditions further improve the hydrolysis efficiency and shorten the reaction time, achieving a collagen extraction rate of over 85%. Furthermore, the extracted collagen has high purity and excellent performance, making it suitable for use in food, cosmetics, and pharmaceutical fields, thus increasing the added value of waste chrome-tanned leather scraps. The present invention provides a method for the clean reprocessing and resource utilization of waste chrome-tanned leather scraps. The residue after collagen extraction is reused to prepare plastic fillers, realizing the full utilization of waste chrome-tanned leather scraps, with high resource utilization rate and reduced solid waste emissions. The reagents used in the entire process of this invention are all environmentally friendly, with no emissions of toxic or harmful gases, liquids, or solid waste, thus achieving clean production. At the same time, the process steps are simple, easy to operate, have low equipment requirements, low production costs, and are easy to promote and apply on a large scale. Detailed Implementation

[0018] The present invention will be further described in detail below through specific embodiments. It should be understood that the described embodiments are only for explaining the present invention and do not limit the present invention.

[0019] Unless otherwise specified, the experimental methods used in the following examples are conventional methods in the art. Unless otherwise specified, the materials and reagents used in the following examples are commercially available. Example 1

[0020] This embodiment describes a method for the clean reprocessing and resource utilization of waste chrome-tanned leather scraps, comprising the following steps performed sequentially: S0. Pretreatment: Screen the waste chrome-tanned leather scraps to remove impurities; put the screened waste chrome-tanned leather scraps into a crusher and crush them into particles with a particle size of 1mm; put the crushed particles into a forced-air drying oven and dry them at 60℃ for 6 hours to obtain dried chrome-tanned leather scrap particles. S1. Cleaning treatment: Take the dried chrome tanned leather scraps and add a composite cleaning agent consisting of 2% citric acid, 1% disodium EDTA, and the remainder deionized water at a solid-liquid ratio of 1:8; turn on the stirring device and stir continuously at a stirring speed of 200 r / min, while raising the temperature and maintaining it at 50℃ for 4 hours; after the reaction is completed, filter the residue and wash it three times with deionized water until the pH of the washing liquid is 6. Then put the residue into a forced-air drying oven and dry it at 60℃ for 3 hours to obtain clean chrome tanned leather scraps; collect the filtrate. S2. Collagen Extraction: Take the clean chrome-tanned leather scraps and filter residue, add deionized water at a solid-liquid ratio of 1:10, and then add 0.5% of a compound enzyme preparation consisting of protease and lipase at a mass ratio of 3:1, accounting for 0.5% of the filter residue mass. Place the mixture in a high-pressure reactor, seal it, heat it to 90°C, control the pressure at 0.1 MPa, and stir at a stirring speed of 150 r / min. Under these conditions, carry out a high-temperature enzymatic hydrolysis reaction for 5 hours. After the reaction is completed, perform cooling and depressurization treatment, and then centrifuge at 3000 r / min for 25 minutes to separate the supernatant and residue. Place the obtained supernatant at 50°C and 0.06 MPa for reduced pressure concentration to 1 / 5 of the original volume, and then transfer the concentrate to a freeze dryer and freeze dry at -40°C and 10 Pa for 16 hours to obtain collagen powder. S3. Chromium recovery: Take the filtrate obtained from S1, add a 10% sodium hydroxide solution to it, adjust the pH to 8, stir evenly, and let it stand for 3 hours to precipitate; then filter it, and the precipitate obtained is chromium hydroxide precipitate, wash it twice with deionized water, and then place the washed precipitate in a muffle furnace and calcine it at 500℃ for 5 hours to obtain chromium trioxide powder; the mother liquor obtained from filtration is evaporated and concentrated at 80℃ until crystals precipitate, and then cooled to crystallize to obtain sodium citrate crystals; S4. Residue Reuse: Take the residue obtained in S2, put it into a forced-air drying oven, and dry it at 60°C for 4 hours to obtain dried residue; mix the dried residue with polyethylene and plasticizer in a mass ratio of 5:3:2, and then put the mixture into an extruder and extrude it at a temperature of 150°C and a screw speed of 10r / min to obtain plastic filler.

[0021] According to the test results, the chromium recovery rate in this embodiment was 90.2%, the collagen extraction rate was 85.1%, the purity of the prepared collagen powder was 92.3%, and the performance of the plastic filler met the relevant industry standards. Example 2

[0022] This embodiment describes a method for the clean reprocessing and resource utilization of waste chrome-tanned leather scraps, comprising the following steps performed sequentially: S0. Pretreatment: Screen the waste chrome-tanned leather scraps to remove impurities; put the screened waste chrome-tanned leather scraps into a crusher and crush them into particles with a particle size of 3mm; put the crushed particles into a forced-air drying oven and dry them at 70℃ for 5 hours to obtain dried chrome-tanned leather scrap particles. S1. Cleaning treatment: Take the dried chrome tanned leather scraps and add a composite cleaning agent consisting of 3.5% citric acid, 2% disodium EDTA, and the remainder deionized water at a solid-liquid ratio of 1:10; turn on the stirring device and stir continuously at a stirring speed of 250 r / min, while raising the temperature and maintaining it at 60℃ for 3 hours; after the reaction, filter the residue and wash it 4 times with deionized water until the pH of the washing liquid is 6.5. Then put the residue into a forced-air drying oven and dry it at 70℃ for 2.5 hours to obtain clean chrome tanned leather scraps; collect the filtrate. S2. Collagen Extraction: Take the clean chrome-tanned leather scraps and filter residue, add deionized water at a solid-liquid ratio of 1:12, and then add 1% of the filter residue mass of a compound enzyme preparation composed of protease and lipase at a mass ratio of 4:1; place the mixture in a high-pressure reactor, seal it, heat it to 100℃, control the pressure at 0.15MPa, and stir at a stirring speed of 200r / min for 4 hours under these conditions; after the reaction, cool and depressurize it, and then centrifuge it at 4000r / min for 20 minutes to separate the supernatant and residue; place the obtained supernatant at 55℃ and 0.07MPa for reduced pressure concentration to 1 / 4 of the original volume, and then transfer the concentrate to a freeze dryer and freeze dry it at -35℃ and 15Pa for 14 hours to obtain collagen powder; S3. Chromium recovery: Take the filtrate obtained from S1, add a 12% sodium hydroxide solution to it, adjust the pH to 8.5, stir evenly, and let it stand for 2.5 hours to precipitate; then filter it, and the precipitate obtained is chromium hydroxide precipitate, which is washed three times with deionized water, and then placed in a muffle furnace and calcined at 550℃ for 4 hours to obtain chromium trioxide powder; the mother liquor obtained from filtration is evaporated and concentrated at 85℃ until crystals precipitate, and then cooled to crystallize to obtain sodium citrate crystals; S4. Residue Reuse: Take the residue obtained in S2, put it into a forced-air drying oven, and dry it at 70°C for 3.5 hours to obtain dried residue; mix the dried residue with polyethylene and plasticizer in a mass ratio of 5:3:2, and then put the mixture into an extruder and extrude it at a temperature of 165°C and a screw speed of 12r / min to obtain plastic filler.

[0023] According to the test results, the chromium recovery rate in this embodiment was 92.5%, the collagen extraction rate was 87.3%, the purity of the prepared collagen powder was 94.1%, and the plastic filler performance was good. Example 3

[0024] This embodiment describes a method for the clean reprocessing and resource utilization of waste chrome-tanned leather scraps, comprising the following steps performed sequentially: S0. Pretreatment: Screen the waste chrome-tanned leather scraps to remove impurities; put the screened waste chrome-tanned leather scraps into a crusher and crush them into particles with a particle size of 5mm; put the crushed particles into a forced-air drying oven and dry them at 80℃ for 4 hours to obtain dried chrome-tanned leather scrap particles. S1. Cleaning treatment: Take the dried chrome tanned leather scraps and add a composite cleaning agent consisting of 5% citric acid, 3% disodium EDTA, and the remainder deionized water at a solid-liquid ratio of 1:12; turn on the stirring device and stir continuously at a stirring speed of 300 r / min, while raising the temperature and maintaining it at 70℃ for 2 hours; after the reaction is completed, filter the residue and wash it 5 times with deionized water until the pH of the washing liquid is 7. Then put the residue into a forced-air drying oven and dry it at 80℃ for 2 hours to obtain clean chrome tanned leather scraps; collect the filtrate. S2. Collagen Extraction: Take the clean chrome-tanned leather scraps and filter residue, add deionized water at a solid-liquid ratio of 1:15, and then add 1.5% of a compound enzyme preparation consisting of protease and lipase at a mass ratio of 5:1, accounting for 1.5% of the filter residue mass. Place the mixture in a high-pressure reactor, seal it, heat it to 65°C, control the pressure at 0.2 MPa, and stir at a stirring speed of 250 r / min. Under these conditions, carry out high-temperature enzymatic hydrolysis for 3 hours. After the reaction is completed, perform cooling and depressurization treatment, and then centrifuge at 5000 r / min for 15 minutes to separate the supernatant and residue. Place the obtained supernatant at 60°C and 0.08 MPa for reduced pressure concentration to 1 / 3 of the original volume, and then transfer the concentrate to a freeze dryer and freeze dry at -30°C and 20 Pa for 12 hours to obtain collagen powder. S3. Chromium recovery: Take the filtrate obtained from S1, add a 15% sodium hydroxide solution to it, adjust the pH to 9, stir evenly, and let it stand for 2 hours to precipitate; then filter it, and the precipitate obtained is chromium hydroxide precipitate, which is washed with deionized water, and then the washed precipitate is placed in a muffle furnace and calcined at 600℃ for 3 hours to obtain chromium trioxide powder; the mother liquor obtained from filtration is evaporated and concentrated at 90℃ until crystals precipitate, and then cooled to crystallize to obtain sodium citrate crystals; S4. Residue Reuse: Take the residue obtained in S2, put it into a forced-air drying oven, and dry it at 80°C for 3 hours to obtain dried residue; mix the dried residue with polyethylene and plasticizer in a mass ratio of 5:3:2, and then put the mixture into an extruder and extrude it at 180°C and a screw speed of 15r / min to obtain plastic filler.

[0025] According to the test results, the chromium recovery rate in this embodiment was 93.8%, the collagen extraction rate was 88.5%, the purity of the prepared collagen powder was 95.2%, and the performance of the plastic filler met the relevant requirements.

[0026] In other embodiments, the method for clean reprocessing and resource utilization of waste chrome-tanned leather scraps includes step S0, in which the waste chrome-tanned leather scraps are crushed into particles with a particle size of 2 mm, 4 mm or 5 mm, and dried at 63°C, 78°C or 80°C for 4.5 hours or 5 hours to obtain dried chrome-tanned leather scrap particles.

[0027] In step S1, the dried chrome-tanned leather scraps can be added to a composite cleaning agent at a solid-liquid ratio of 1:9 or 1:11, wherein the mass fraction of citric acid can be 2.5%, 3.2%, or 4.8%, and the mass fraction of disodium ethylenediaminetetraacetate can be 1.2%, 2.5%, or 2.8%. The mixing reaction can be carried out at 55°C or 68°C with a stirring speed of 220 r / min or 280 r / min for 2.5 hours or 3.5 hours. After the reaction is completed, the residue is filtered, and the resulting filter residue can be washed 2 or 4 times with deionized water until the pH of the washing liquid is 6.2 or 6.8. Then, it is dried at 62°C or 78°C for 2.2 hours or 2.8 hours to obtain clean chrome-tanned leather scrap filter residue, and the filtrate is collected.

[0028] In step S2, the clean chrome-tanned leather shavings filter residue can be added to water at a solid-liquid ratio of 1:11 or 1:14, and then 0.7% or 1.3% of a compound enzyme preparation by weight of the filter residue can be added, wherein the mass ratio of protease to lipase can be 3.5:1 or 4.5:1; the high-temperature enzymatic hydrolysis reaction can be carried out at 92℃ or 60℃, pressure of 0.12 MPa or 0.18 MPa, and stirring conditions of 170 r / min or 230 r / min for 3.5 hours or 4.5 hours; after the reaction, the supernatant is centrifuged and concentrated under reduced pressure to 1 / 4.5 of the original volume at 52℃ or 58℃, 0.065 MPa or 0.075 MPa, and then freeze-dried for 13 hours or 15 hours to obtain collagen powder.

[0029] In step S3, the pH of the filtrate can be adjusted to 8.2 or 8.8 with a sodium hydroxide solution of 11% or 13.5% by mass, and filtered after standing for precipitation for 2.2 hours or 3.5 hours. The resulting precipitate can be washed and calcined at 520°C or 580°C for 3.2 hours or 4.6 hours to obtain chromium trioxide powder. The mother liquor is evaporated, concentrated and crystallized at 82°C or 88°C to obtain sodium citrate crystals.

[0030] In step S4, the residue after collagen extraction can be dried at 65°C or 78°C for 3.2 hours or 3.8 hours. The dried residue is then mixed with a thermoplastic polymer substrate (such as polypropylene or ethylene-vinyl acetate copolymer) and a plasticizer at a mass ratio of 5:3:2. The mixture is then extruded at 155°C or 175°C, 11 r / min or 14 r / min to obtain a plastic filler.

[0031] In another embodiment, to obtain high-purity collagen powder, the parameters of step S2 can be specifically controlled: deionized water is added at a solid-liquid ratio of 1:13, and a compound enzyme preparation is prepared with a protease to lipase mass ratio of 4:2:1, with the addition amount being 1.1% of the filter residue mass. The reaction is carried out at 102°C, 0.16 MPa pressure, and 210 r / min stirring for 3.8 hours. The supernatant is concentrated under reduced pressure at 56°C and 0.072 MPa, and then freeze-dried at -33°C and 16 Pa for 14.5 hours. The collagen powder obtained by this method has high purity and excellent functionality.

[0032] In another embodiment, to improve the chromium recovery efficiency, the parameters of step S3 can be specifically controlled: the pH of the filtrate is adjusted to 8.6 with a 13% sodium hydroxide solution, the filtrate is allowed to settle for 3 hours, then filtered, and the precipitate is washed and calcined at 560°C for 4.2 hours. Under these conditions, the chromium recovery rate is stable and the product purity is excellent.

[0033] In another embodiment, to optimize the performance of the plastic filler, the parameters of step S4 can be specifically controlled: the dried residue is mixed with polypropylene and plasticizer at a mass ratio of 5:3:2, and then extruded at 170°C and 13 r / min. The resulting filler achieves a good balance between mechanical properties and cost control.

[0034] It should be noted that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art can still modify the technical solutions described in the above embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for the clean reprocessing and resource utilization of waste chrome-tanned leather scraps, characterized in that, This includes the following steps performed sequentially: S1. Cleaning treatment: Take waste chrome tanned leather scraps and add them to the compound cleaning agent at a solid-liquid ratio of 1:8~12. Mix continuously for 2~4 hours, wash, and separate the filtrate and filter residue. S2. Collagen extraction: Take the filter residue and add water at a solid-liquid ratio of 1:10~15, then add 0.5~1.5% of the compound enzyme preparation by weight of the filter residue, and after high-temperature enzymatic hydrolysis, separate the supernatant and residue. The supernatant is freeze-dried to obtain collagen powder. S3. Chromium recovery: Adjust the pH of the filtrate to alkaline, let it stand, and calcine the precipitate obtained by filtration to obtain chromium trioxide. The remaining liquid is concentrated and crystallized to obtain sodium citrate. S4. Residue Recycling: The residue is extruded with a thermoplastic polymer substrate to obtain a plastic filler; The composite cleaning agent is composed of 2-5% citric acid, 1-3% disodium ethylenediaminetetraacetate, and the remainder water by mass. The compound enzyme preparation consists of protease and lipase in a mass ratio of 3 to 5:

1.

2. The method for clean reprocessing and resource utilization of waste chrome-tanned leather scraps according to claim 1, characterized in that, The waste chrome-tanned leather scraps are obtained by taking waste chrome-tanned leather, removing impurities, crushing it to a particle size of 1-5 mm, and drying it.

3. The method for clean reprocessing and resource utilization of waste chrome-tanned leather scraps according to claim 2, characterized in that, Continuous mixing is performed at 50~70℃ and 200~300r / min.

4. The method for clean reprocessing and resource utilization of waste chrome-tanned leather scraps according to claim 3, characterized in that, In step S1, washing continues until the pH of the washing solution reaches 6-7.

5. The method for clean reprocessing and resource utilization of waste chrome-tanned leather scraps according to claim 4, characterized in that, The high-temperature enzymatic hydrolysis reaction is carried out at a temperature of 60~100℃, a pressure of 0.1~0.2MPa, a rotation speed of 150~250r / min, and a reaction time of 3~5 h.

6. The method for clean reprocessing and resource utilization of waste chrome-tanned leather scraps according to claim 5, characterized in that, The supernatant is first concentrated under reduced pressure and then freeze-dried.

7. The method for clean reprocessing and resource utilization of waste chrome-tanned leather scraps according to claim 6, characterized in that, The calcination temperature is 500~600℃, and the calcination time is 3~5h.

8. The method for clean reprocessing and resource utilization of waste chrome-tanned leather scraps according to any one of claims 1 to 7, characterized in that, The mass ratio of the residue to the thermoplastic polymer substrate is 5:3; The thermoplastic polymer substrate includes at least one of polyethylene, polypropylene, polybutene, polyisobutylene, and ethylene-vinyl acetate copolymer.

9. The method for clean reprocessing and resource utilization of waste chrome-tanned leather scraps according to claim 8, characterized in that, The residue is dried, mixed with a thermoplastic polymer substrate and a plasticizer at a mass ratio of 5:3:2, and extruded at 150~180℃ and 10~15r / min.

10. The method for clean reprocessing and resource utilization of waste chrome-tanned leather scraps according to any one of claims 1 to 9 is used in the preparation of collagen powder, chromium trioxide powder, sodium citrate crystals or plastic fillers.