Preparation process of chrome tanning agent for leather processing

Abstract

The invention relates to the technical field of chrome tanning agent preparation, in particular to a preparation technology of a chrome tanning agent for leather processing. According to the technical scheme, the method comprises the steps of raw material preparation, mixing and dissolving, curing, filtering, storage, liquid waste treatment and solid waste treatment, wherein the raw material preparation comprises lomine, sulfuric acid and a reducing agent. According to the method, raw materials are prepared and purified before preparation, impurities in the raw materials can be effectively prevented from participating in the reaction, the situation of more pollutants is further produced, the purity of the raw material chromium ore can be improved through flotation and magnetic separation of the raw materials, the reaction is more complete in the dissolution and reduction process of the high-purity chromium ore, and the yield of the chromium ore is improved. The production efficiency can be improved, and the preparation time is shortened.

Description

Technical Field

[0001] The invention relates to the technical field of chrome tanning agent preparation, in particular to a chrome tanning agent preparation process for leather processing. Background Art

[0002] Chrome tanning agents mainly refer to compounds containing trivalent chromium ions, usually basic chromium sulfate or basic chromium chloride. These compounds react chemically with amino acids in the collagen fibers of the skin during the tanning process to form a stable cross-linked structure, thereby giving the leather the desired physical and chemical properties. Chrome tanning agents are widely used chemicals in the leather processing industry, mainly used in the tanning process of leather. Tanning is the process of converting animal skin into leather, with the goal of improving the skin's properties, such as durability, softness and elasticity.

[0003] During the preparation process of chrome tanning agent, the wastewater generated contains a large amount of chromium ions, especially trivalent chromium and hexavalent chromium. Hexavalent chromium is a highly toxic substance that is extremely harmful to aquatic ecosystems and human health. In addition, if the solid waste (chromium residue) generated during the production process of chrome tanning agent is directly piled up without treatment, it may penetrate into the soil and cause heavy metal pollution of the soil. In the entire preparation process, pollutants need to be effectively controlled to meet large-scale processing needs. Therefore, it is necessary to design a chrome tanning agent preparation process that is conducive to pollutant control. Summary of the invention

[0004] The object of the present invention is to provide a process for preparing a chrome tanning agent for leather processing, so as to solve the problems raised in the above-mentioned background technology.

[0005] To achieve the above object, the present invention provides the following technical solution: including raw material preparation, mixed dissolution, aging, filtration, storage, liquid waste treatment and solid waste treatment, the raw material preparation includes ore, sulfuric acid and a reducing agent, and the specific operation steps are:

[0006] S1. Raw material preparation: chromium ore is purified into powder, and a predetermined amount is weighed, and appropriate amounts of sulfuric acid and reducing agent are prepared;

[0007] S2, mixed dissolution: dissolve the chromium ore powder into a dissolution tank filled with a certain amount of water to fully dissolve it, then add sulfuric acid, slowly inject the acid solution under constant stirring, then add a reducing agent to adjust the pH value of the solution, and at the same time detect the degree of reduction of hexavalent chromium;

[0008] S3, aging: aging the chrome tanning liquid with adjusted pH value at a certain temperature for a period of time to stabilize the performance of the chrome tanning agent;

[0009] S4, filtration: filtering the dissolved chrome tanning agent solution to remove undissolved solid particles;

[0010] S5. Storage: The cooled chrome tanning agent solution is sealed and stored in a storage tank to avoid contact with air;

[0011] S6. Liquid waste treatment: Ensure that all waste liquids are properly treated, such as neutralization, sedimentation, flocculation, etc., to meet discharge standards;

[0012] S7. Solid waste treatment: Reduce the content of organic matter in sludge through biological methods, thereby reducing its putrefaction and impact on the environment.

[0013] Preferably, in the raw material preparation process, the pretreatment of the chromium ore comprises the following steps:

[0014] S1. Chrome ore washing: Use water or other solvents to wash the chrome ore to remove soluble impurities and some insoluble impurities;

[0015] S2. Flotation of chromium ore: The flotation method uses the differences in physical and chemical properties of the mineral surface to separate chromium ore from other minerals;

[0016] S3. Drying of chrome ore: Use drying equipment to quickly dry the chrome ore after flotation;

[0017] S4. Crushing of chromium ore: crushing the blocky chromium ore into fine powder structure by crushing equipment;

[0018] S5. Magnetic separation of chromium ore: Magnetic separation of chromium ore powder is used to separate chromium ore powder from other minerals by utilizing the physical and chemical properties differences on the surface of the minerals.

[0019] S6. Weighing of chromium ore: Weigh the powdered chromium ore to obtain the weight of the chromium ore powder required for preparation.

[0020] Preferably, in the mixed dissolution process, the specific operation steps are:

[0021] S1. Add chromium ore powder: add the chromium ore powder into a certain amount of water dissolution tank, and turn on the agitator to fully dissolve it;

[0022] S2. Add sulfuric acid: slowly add sulfuric acid while stirring continuously. Control the speed of adding sulfuric acid to prevent a sharp rise in temperature. Monitor the temperature in real time. The pH value of the solution will drop rapidly during the acidification process. Acidify the solution to generate chromium ions.

[0023] S3. Adding reducing agent: Under acidic conditions, adding reducing agent to reduce hexavalent chromium to trivalent chromium. During this process, the temperature of the solution is strictly monitored within the range of 40-60°C to ensure complete and uniform reaction. After the reduction reaction is completed, the pH value of the solution is adjusted to 3.8-4.2 by adding alkaline substances (such as sodium hydroxide, sodium carbonate, etc.).

[0024] S4. Sampling and testing: monitor the reduction degree of hexavalent chromium by colorimetry to see if it is within the qualified range;

[0025] S5. Collection of liquid waste: During the process of dissolving chromium salts and acidification, some unqualified liquid wastes are generated, such as unreacted chromium salt solution or excess acid. Such wastes are collected.

[0026] Preferably, the specific operation steps of the sampling and detection include:

[0027] S1. Sampling: After adjusting the pH value of the solution to 3.8-4.2, take a certain amount of the test solution sample;

[0028] S2. Acidification: Add an appropriate amount of dilute sulfuric acid or dilute nitric acid to the sample to keep the pH value of the solution below 2.0 to prevent trivalent chromium from being oxidized during the detection process;

[0029] S3, adding colorant and mixing: adding diphenylcarbohydrazide (DPC) reagent to the acidified sample, DPC reacts with hexavalent chromium under acidic conditions to form a purple-red complex;

[0030] S4, colorimetry: the sample with DPC reagent added is fully mixed and placed at room temperature for a certain time (usually 5-10 minutes) to complete the color reaction;

[0031] S5. Result comparison: Use a spectrophotometer to measure the absorbance of the sample solution at a wavelength of about 540nm. At the same time, prepare a series of hexavalent chromium standard solutions with known concentrations, and follow the same steps for color development and colorimetry to prepare a standard curve;

[0032] S6. Convert the absorbance of the sample into the concentration of hexavalent chromium according to the standard curve. If the concentration of hexavalent chromium in the sample is lower than the detection limit, it can be considered that the hexavalent chromium has been completely reduced to trivalent chromium.

[0033] Preferably, after the sampling and testing step S6, it is determined whether the test result is qualified. If it meets the requirements, it enters the next aging process. Otherwise, the reducing agent and alkaline solution are squeezed into the reaction again.

[0034] Preferably, the specific operation steps for treating the liquid waste generated in the mixed dissolution include:

[0035] S1. Adjust pH: Since chromium-containing wastewater is usually acidic, the pH value can be adjusted by adding alkaline substances (such as lime, sodium hydroxide, etc.) to make it suitable for subsequent treatment steps;

[0036] S2, flocculation precipitation: adding flocculants (such as polyferric sulfate, polyaluminium chloride, etc.) to help chromium ions form flocs to facilitate subsequent precipitation;

[0037] S3, reduction reaction: using reducing agents such as ferrous sulfate (FeSO4) and sodium sulfite (Na2SO3) to reduce hexavalent chromium (Cr(VI)) in the wastewater to trivalent chromium (Cr(III));

[0038] S4, precipitation: the reduced trivalent chromium is added with a precipitant (such as sodium hydroxide, lime, etc.) to form an insoluble chromium hydroxide precipitate;

[0039] S5, flocculation and clarification: With the help of flocculants, the sediment is flocculated into larger flocs, and then the solid-liquid separation is carried out in the clarification tank;

[0040] S6. Filtration: Suspended and dissolved matter in wastewater is further removed through sand filters, activated carbon filters and other equipment.

[0041] S7. Safe discharge of purified liquid: Safely discharge the filtered liquid and collect the filtered solid waste.

[0042] Preferably, the specific operation steps for treating the solid waste generated during the mixed dissolution include:

[0043] S1. Anaerobic digestion: The sludge is digested under anaerobic conditions (oxygen-free environment), and the organic matter is decomposed by anaerobic microorganisms to produce methane and carbon dioxide. The volume of the digested sludge can be reduced by about 50%, and the number of pathogens is significantly reduced.

[0044] S2. Aerobic digestion: aeration of sludge for a long time under aerobic conditions, using aerobic microorganisms to decompose organic matter. This can further reduce the volume of sludge and eliminate pathogens.

[0045] S3. Harmless detection and burial.

[0046] Preferably, the equipment for the steps of mixing, dissolving, aging, filtering and storing comprises a storage tank and a preparation tank, the preparation tank is fixed to the outside of the storage tank by a fixing frame, a slag discharge pipe is fixed to the bottom of the preparation tank, a connecting pipe is fixed above the side wall of the storage tank, the end of the connecting pipe is fixed to the slag discharge pipe through a three-way valve, an anti-corrosion lining is fixed to the inner side wall of the preparation tank, a stirring rod is rotatably connected to the center position of the preparation tank, a stirring motor for driving the stirring rod to rotate is fixed to the upper end of the preparation tank, a powder feed pipe, a sulfuric acid feed pipe and a reducing agent feed pipe are fixed above the side wall of the preparation tank, a sampling tube is fixed below the side wall of the preparation tank, a temperature sensor and a temperature control component are arranged in the preparation tank, the temperature control component comprises a radiator, a circulation pipe and a circulation pump, the radiator is fixed to the outside of the fixing frame, the circulation pipe is installed between the radiator and the preparation tank, the circulation pump is fixed to the fixing frame and its position is aligned with the circulation pipe, one end of the circulation pipe located in the preparation tank is a spring-mounted structure and is located outside the stirring rod, and one end of the circulation pipe located in the radiator is serpentine.

[0047] Preferably, an annular partition is fixed in the storage tank, a filter is installed on the annular partition, and a vacuum pump is fixed at the upper end of the storage tank.

[0048] Compared with the prior art, the present invention has the following beneficial effects:

[0049] 1. Prepare the raw materials and purify them before preparation, which can effectively prevent impurities in the raw materials from participating in the reaction, thereby producing less pollutants. By flotation and magnetic separation of the raw materials, the purity of the raw chromium ore can be improved, so that the high-purity chromium ore can react more completely during the dissolution and reduction process, which can improve production efficiency and shorten preparation time.

[0050] 2. Through the steps of neutralization, flocculation, reduction, precipitation, etc., chromium-containing wastewater is effectively treated to reduce pollution to the environment. In the preparation process, strict detection and control measures are taken to ensure that hexavalent chromium is completely reduced to trivalent chromium, reducing the harm to operators and the environment. At the same time, biological methods are used to reduce organic matter in sludge and reduce the impact on the environment, making the overall preparation process more environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 This is a schematic diagram of the overall process of a chrome tanning agent preparation process for leather processing according to the present invention;

[0052] Figure 2 This is a schematic flow diagram of a mixing and dissolving operation in a process for preparing a chrome tanning agent for leather processing according to the present invention;

[0053] Figure 3 This is a schematic diagram of a liquid waste treatment process in a chrome tanning agent preparation process for leather processing according to the present invention;

[0054] Figure 4 The present invention is a schematic diagram of a solid waste treatment process in a chrome tanning agent preparation process for leather processing.

[0055] Figure 5 The present invention is a schematic diagram of the front structure of a preparation device in a chrome tanning agent preparation process for leather processing.

[0056] Figure 6 The present invention is a schematic diagram of the internal flow of a preparation tank in a process for preparing a chrome tanning agent for leather processing.

[0057] In the figure: 1. Storage tank; 11. Annular partition; 12. Filter; 13. Vacuum pump; 2. Preparation tank; 21. Powder feed pipe; 22. Sulfuric acid feed pipe; 23. Reductant feed pipe; 24. Stirring motor; 25. Stirring rod; 26. Anti-corrosion lining; 3. Radiator; 31. Circulation pipe; 32. Circulation pump; 4. Sampling pipe; 5. Slag discharge pipe; 51. Three-way valve; 6. Fixing frame; 7. Connecting pipe. DETAILED DESCRIPTION

[0058] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0059] See also Figure 1-4 The present invention provides a technical solution: including raw material preparation, mixed dissolution, aging, filtration, storage, liquid waste treatment and solid waste treatment. The raw material preparation includes Luo ore, sulfuric acid and a reducing agent. The specific operation steps are:

[0060] S1. Raw material preparation: chromium ore is purified into powder, and a predetermined amount is weighed, and appropriate amounts of sulfuric acid and reducing agent are prepared;

[0061] S2, mixed dissolution: dissolve the chromium ore powder into a dissolution tank filled with a certain amount of water to fully dissolve it, then add sulfuric acid, slowly inject the acid solution under constant stirring, then add a reducing agent to adjust the pH value of the solution, and at the same time detect the degree of reduction of hexavalent chromium;

[0062] S3, aging: aging the chrome tanning liquid with adjusted pH value at a certain temperature for a period of time to stabilize the performance of the chrome tanning agent;

[0063] S4, filtration: filtering the dissolved chrome tanning agent solution to remove undissolved solid particles;

[0064] S5. Storage: The cooled chrome tanning agent solution is sealed and stored in a storage tank to avoid contact with air;

[0065] S6. Liquid waste treatment: Ensure that all waste liquids are properly treated, such as neutralization, sedimentation, flocculation, etc., to meet discharge standards;

[0066] S7. Solid waste treatment: Reduce the content of organic matter in sludge through biological methods, thereby reducing its putrefaction and impact on the environment.

[0067] During the raw material preparation process, the pretreatment of chrome ore includes the following steps:

[0068] S1. Chrome ore washing: Use water or other solvents to wash the chrome ore to remove soluble impurities and some insoluble impurities;

[0069] S2. Flotation of chromium ore: The flotation method uses the differences in physical and chemical properties of the mineral surface to separate chromium ore from other minerals;

[0070] S3. Drying of chrome ore: Use drying equipment to quickly dry the chrome ore after flotation;

[0071] S4. Crushing of chromium ore: crushing the blocky chromium ore into fine powder structure by crushing equipment;

[0072] S5. Magnetic separation of chromium ore: Magnetic separation of chromium ore powder is used to separate chromium ore powder from other minerals by utilizing the physical and chemical properties differences on the surface of the minerals.

[0073] S6. Weighing of chromium ore: Weigh the powdered chromium ore to obtain the weight of the chromium ore powder required for preparation.

[0074] During the mixing and dissolving process, the specific operation steps are as follows:

[0075] S1. Add chromium ore powder: add chromium ore powder into a certain water dissolution tank, and turn on the agitator to fully dissolve it;

[0076] S2. Add sulfuric acid: slowly add sulfuric acid while stirring continuously. Control the speed of adding sulfuric acid to prevent a sharp rise in temperature. Monitor the temperature in real time. The pH value of the solution will drop rapidly during the acidification process. Acidify the solution to generate chromium ions.

[0077] S3. Adding reducing agent: Under acidic conditions, adding reducing agent to reduce hexavalent chromium to trivalent chromium. During this process, the temperature of the solution is strictly monitored within the range of 40-60°C to ensure complete and uniform reaction. After the reduction reaction is completed, the pH value of the solution is adjusted to 3.8-4.2 by adding alkaline substances (such as sodium hydroxide, sodium carbonate, etc.).

[0078] S4. Sampling and testing: monitor the reduction degree of hexavalent chromium by colorimetry to see if it is within the qualified range;

[0079] S5. Collection of liquid waste: During the process of dissolving chromium salts and acidification, some unqualified liquid wastes are generated, such as unreacted chromium salt solution or excess acid. Such wastes are collected.

[0080] The specific operation steps of the sampling test include:

[0081] S1. Sampling: After adjusting the pH value of the solution to 3.8-4.2, take a certain amount of the test solution sample;

[0082] S2. Acidification: Add an appropriate amount of dilute sulfuric acid or dilute nitric acid to the sample to keep the pH value of the solution below 2.0 to prevent trivalent chromium from being oxidized during the detection process;

[0083] S3, adding colorant and mixing: adding diphenylcarbohydrazide (DPC) reagent to the acidified sample, DPC reacts with hexavalent chromium under acidic conditions to form a purple-red complex;

[0084] S4. Colorimetry: The sample with the DPC reagent added is mixed thoroughly and placed at room temperature for a certain period of time (usually 5-10 minutes) to complete the color reaction;

[0085] S5. Result comparison: Use a spectrophotometer to measure the absorbance of the sample solution at a wavelength of about 540nm. At the same time, prepare a series of hexavalent chromium standard solutions with known concentrations, and follow the same steps for color development and colorimetry to prepare a standard curve;

[0086] S6. According to the standard curve, convert the absorbance of the sample into the concentration of hexavalent chromium. If the concentration of hexavalent chromium in the sample is lower than the detection limit, it can be considered that the hexavalent chromium has been completely reduced to trivalent chromium.

[0087] After the step S6 of sampling and testing, it is determined whether the test result is qualified. If it meets the requirements, it enters the next aging process. Otherwise, the reducing agent and alkaline solution are squeezed into the reaction again.

[0088] The specific steps for treating liquid waste generated during mixed dissolution include:

[0089] S1. Adjust pH: Since chromium-containing wastewater is usually acidic, the pH value can be adjusted by adding alkaline substances (such as lime, sodium hydroxide, etc.) to make it suitable for subsequent treatment steps;

[0090] S2, flocculation precipitation: adding flocculants (such as polyferric sulfate, polyaluminium chloride, etc.) to help chromium ions form flocs to facilitate subsequent precipitation;

[0091] S3, reduction reaction: using reducing agents such as ferrous sulfate (FeSO4) and sodium sulfite (Na2SO3) to reduce hexavalent chromium (Cr(VI)) in the wastewater to trivalent chromium (Cr(III));

[0092] S4, precipitation: the reduced trivalent chromium is added with a precipitant (such as sodium hydroxide, lime, etc.) to form an insoluble chromium hydroxide precipitate;

[0093] S5, flocculation and clarification: With the help of flocculants, the sediment is flocculated into larger flocs, and then the solid-liquid separation is carried out in the clarification tank;

[0094] S6. Filtration: Suspended and dissolved matter in wastewater is further removed through sand filters, activated carbon filters and other equipment.

[0095] S7. Safe discharge of purified liquid: Safely discharge the filtered liquid and collect the filtered solid waste.

[0096] The specific operation steps for treating solid waste generated during mixed dissolution include:

[0097] S1. Anaerobic digestion: The sludge is digested under anaerobic conditions (oxygen-free environment), and the organic matter is decomposed by anaerobic microorganisms to produce methane and carbon dioxide. The volume of the digested sludge can be reduced by about 50%, and the number of pathogens is significantly reduced.

[0098] S2. Aerobic digestion: aeration of sludge for a long time under aerobic conditions, using aerobic microorganisms to decompose organic matter. This can further reduce the volume of sludge and eliminate pathogens.

[0099] S3. Harmless detection and burial.

[0100] See also Figure 5 and Figure 6The present invention provides a technical solution: the steps of mixing, dissolving, maturing, filtering and storing in the chrome tanning agent preparation process, the equipment comprises a storage tank 1 and a preparation tank 2, the preparation tank 2 is fixed to the outside of the storage tank 1 by a fixing frame 6, a slag discharge pipe 5 is fixed to the bottom of the preparation tank 2, a connecting pipe 7 is fixed above the side wall of the storage tank 1, the end of the connecting pipe 7 is fixed to the slag discharge pipe 5 through a three-way valve 51, an anti-corrosion lining 26 is fixed to the inner wall of the preparation tank 2, a stirring rod 25 is rotatably connected to the center position of the preparation tank 2, a stirring motor 24 for driving the stirring rod 25 to rotate is fixed to the upper end of the preparation tank 2, a powder feed pipe 21, a sulfuric acid feed pipe 22 and a reducing agent feed pipe 23 are fixed above the side wall of the preparation tank 2 The material pipe 23, a sampling tube 4 is fixed under the side wall of the preparation tank 2, a temperature sensor and a temperature control component are arranged in the preparation tank 2, the temperature control component includes a radiator 3, a circulation pipe 31 and a circulation pump 32, the radiator 3 is fixed on the outside of the fixing frame 6, the circulation pipe 31 is installed between the radiator 3 and the preparation tank 2, the circulation pump 32 is fixed on the fixing frame 6, and its position is aligned with the circulation pipe 31, one end of the circulation pipe 31 located in the preparation tank 2 is a spring-mounted structure, and is located on the periphery of the stirring rod 25, and one end of the circulation pipe 31 located in the radiator 3 is serpentine-shaped, an annular partition 11 is fixed in the storage tank 1, a filter screen 12 is installed on the annular partition 11, and a vacuum pump 13 is fixed on the upper end of the storage tank 1.

[0101] Specifically, when performing the steps of mixing, dissolving, aging, filtering and storing, firstly, the whole device is connected to an external power supply, and then the powder obtained after the purification of the chromium ore is put into the preparation tank 2 through the powder feed pipe 21, and then sulfuric acid is poured into the preparation tank 2 through the sulfuric acid feed pipe 22. In this process, the output end of the stirring motor 24 can drive the stirring rod 25 to rotate continuously to fully dissolve the powder, and then the reducing agent is added through the reducing agent feed pipe 23 to adjust the pH value of the solution. At the same time, the solution is sampled by the sampling tube 4 to detect the degree of reduction of the hexavalent chromium, until the hexavalent chromium is fully reduced, and then it is aged at a predetermined temperature. At this time, the temperature sensor can be used to To monitor the temperature of the solution, when the temperature is higher than the predetermined value, the circulation pump 32 can be used to drive the condensing agent in the circulation pipe 31 to circulate, absorb the heat in the solution, and enter the radiator 3 to dissipate it, so as to ensure the stability of the solution temperature. Finally, the vacuum pump 13 is used to discharge the air in the storage tank 1, and the three-way valve 51 is opened at the same time. The matured solution can be discharged into the storage tank 1 through the connecting pipe 7. The undissolved solid particles are removed by filtering through the filter screen 12, so that the solution can enter the storage tank 1 for safe storage. Finally, the three-way valve 51 is adjusted to discharge and collect the residual liquid from the slag discharge pipe 5, and collect the solid particles on the filter screen 12, and then carry out subsequent evolution treatment.

[0102] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0103] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A process for preparing a chrome tanning agent for leather processing, characterized in that: It includes raw material preparation, mixed dissolution, aging, filtration, storage, liquid waste treatment and solid waste treatment. The raw material preparation includes Luo ore, sulfuric acid and reducing agent. The specific operation steps are as follows: S1. Raw material preparation: chromium ore is purified into powder, and a predetermined amount is weighed, and appropriate amounts of sulfuric acid and reducing agent are prepared; S2, mixed dissolution: dissolve the chromium ore powder into a dissolution tank filled with a certain amount of water to fully dissolve it, then add sulfuric acid, slowly inject the acid solution under constant stirring, then add a reducing agent to adjust the pH value of the solution, and at the same time detect the degree of reduction of hexavalent chromium; S3, aging: aging the chrome tanning liquid with adjusted pH value at a certain temperature for a period of time to stabilize the performance of the chrome tanning agent; S4, filtration: filtering the dissolved chrome tanning agent solution to remove undissolved solid particles; S5. Storage: The cooled chrome tanning agent solution is sealed and stored in a storage tank to avoid contact with air; S6. Liquid waste treatment: Ensure that all waste liquids are properly treated, such as neutralization, sedimentation, flocculation, etc., to meet discharge standards; S7. Solid waste treatment: Reduce the content of organic matter in sludge through biological methods, thereby reducing its putrefaction and impact on the environment.

2. The process for preparing a chrome tanning agent for leather processing according to claim 1, characterized in that: In the raw material preparation process, the pretreatment of chromium ore includes the following steps: S1. Chrome ore washing: Use water or other solvents to wash the chrome ore to remove soluble impurities and some insoluble impurities; S2. Flotation of chromium ore: The flotation method uses the differences in physical and chemical properties of the mineral surface to separate chromium ore from other minerals; S3. Drying of chrome ore: Use drying equipment to quickly dry the chrome ore after flotation; S4. Crushing of chromium ore: crushing the blocky chromium ore into fine powder structure by crushing equipment; S5. Magnetic separation of chromium ore: Magnetic separation of chromium ore powder is used to separate chromium ore powder from other minerals by utilizing the physical and chemical properties differences on the surface of the minerals. S6. Weighing of chromium ore: Weigh the powdered chromium ore to obtain the weight of the chromium ore powder required for preparation.

3. The process for preparing a chrome tanning agent for leather processing according to claim 1, characterized in that: The specific steps of the mixed dissolution process are as follows: S1. Add chromium ore powder: add chromium ore powder into a certain water dissolution tank, and turn on the agitator to fully dissolve it; S2. Add sulfuric acid: slowly add sulfuric acid while stirring continuously. Control the speed of adding sulfuric acid to prevent a sharp rise in temperature. Monitor the temperature in real time. The pH value of the solution will drop rapidly during the acidification process. Acidify the solution to generate chromium ions. S3. Adding reducing agent: Under acidic conditions, adding reducing agent to reduce hexavalent chromium to trivalent chromium. During this process, the temperature of the solution is strictly monitored within the range of 40-60°C to ensure complete and uniform reaction. After the reduction reaction is completed, the pH value of the solution is adjusted to 3.8-4.2 by adding alkaline substances (such as sodium hydroxide, sodium carbonate, etc.). S4. Sampling and testing: monitor the reduction degree of hexavalent chromium by colorimetry to see if it is within the qualified range; S5. Collection of liquid waste: During the process of dissolving chromium salts and acidification, some unqualified liquid wastes are generated, such as unreacted chromium salt solution or excess acid. Such wastes are collected.

4. The process for preparing a chrome tanning agent for leather processing according to claim 3, characterized in that: The specific operation steps of the sampling detection include: S1. Sampling: After adjusting the pH value of the solution to 3.8-4.2, take a certain amount of the test solution sample; S2. Acidification: Add an appropriate amount of dilute sulfuric acid or dilute nitric acid to the sample to keep the pH value of the solution below 2.0 to prevent trivalent chromium from being oxidized during the detection process; S3, adding colorant and mixing: adding diphenylcarbohydrazide (DPC) reagent to the acidified sample, DPC reacts with hexavalent chromium under acidic conditions to form a purple-red complex; S4, colorimetry: the sample with DPC reagent added is fully mixed and placed at room temperature for a certain time (usually 5-10 minutes) to complete the color reaction; S5. Result comparison: Use a spectrophotometer to measure the absorbance of the sample solution at a wavelength of about 540nm. At the same time, prepare a series of hexavalent chromium standard solutions with known concentrations, and follow the same steps for color development and colorimetry to prepare a standard curve; S6. Convert the absorbance of the sample into the concentration of hexavalent chromium according to the standard curve. If the concentration of hexavalent chromium in the sample is lower than the detection limit, it can be considered that the hexavalent chromium has been completely reduced to trivalent chromium.

5. The process for preparing a chrome tanning agent for leather processing according to claim 4, characterized in that: After the sampling test step S6, it is determined whether the test result is qualified. If it meets the requirements, it enters the next aging process. Otherwise, the reducing agent and alkaline solution are squeezed into the reaction again.

6. The process for preparing a chrome tanning agent for leather processing according to claim 1, characterized in that: The specific operation steps for treating the liquid waste generated in the mixed dissolution include: S1. Adjust pH: Since chromium-containing wastewater is usually acidic, the pH value can be adjusted by adding alkaline substances (such as lime, sodium hydroxide, etc.) to make it suitable for subsequent treatment steps; S2, flocculation precipitation: adding flocculants (such as polyferric sulfate, polyaluminium chloride, etc.) to help chromium ions form flocs to facilitate subsequent precipitation; S3, reduction reaction: using reducing agents such as ferrous sulfate (FeSO4) and sodium sulfite (Na2SO3) to reduce hexavalent chromium (Cr(VI)) in the wastewater to trivalent chromium (Cr(III)); S4, precipitation: the reduced trivalent chromium is added with a precipitant (such as sodium hydroxide, lime, etc.) to form an insoluble chromium hydroxide precipitate; S5, flocculation and clarification: With the help of flocculants, the sediment is flocculated into larger flocs, and then the solid-liquid separation is carried out in the clarification tank; S6. Filtration: Suspended and dissolved matter in wastewater is further removed through sand filters, activated carbon filters and other equipment. S7. Safe discharge of purified liquid: Safely discharge the filtered liquid and collect the filtered solid waste.

7. The process for preparing a chrome tanning agent for leather processing according to claim 1, characterized in that: The specific operation steps for treating the solid waste generated in the mixed dissolution include: S1. Anaerobic digestion: The sludge is digested under anaerobic conditions (oxygen-free environment), and the organic matter is decomposed by anaerobic microorganisms to produce methane and carbon dioxide. The volume of the digested sludge can be reduced by about 50%, and the number of pathogens is significantly reduced. S2. Aerobic digestion: aeration of sludge for a long time under aerobic conditions, using aerobic microorganisms to decompose organic matter. This can further reduce the volume of sludge and eliminate pathogens. S3. Harmless detection and burial.

8. The process for preparing a chrome tanning agent for leather processing according to claim 1, characterized in that: The equipment for the steps of mixing, dissolving, maturing, filtering and storing comprises a storage tank (1) and a preparation tank (2), wherein the preparation tank (2) is fixed to the outside of the storage tank (1) by a fixing frame (6), a slag discharge pipe (5) is fixed at the bottom of the preparation tank (2), a connecting pipe (7) is fixed above the side wall of the storage tank (1), the end of the connecting pipe (7) is fixed to the slag discharge pipe (5) through a three-way valve (51), an anti-corrosion lining (26) is fixed to the inner side wall of the preparation tank (2), a stirring rod (25) is rotatably connected to the center position of the preparation tank (2), a stirring motor (24) for driving the stirring rod (25) to rotate is fixed at the upper end of the preparation tank (2), a powder feed pipe (21), a sulfuric acid feed pipe (22) and a reducing agent feed pipe (23) are fixed above the side wall of the preparation tank (2), a sampling tube (4) is fixed below the side wall of the preparation tank (2), and a temperature sensor and a temperature control component are arranged in the preparation tank (2); The temperature control assembly comprises a radiator (3), a circulation pipe (31) and a circulation pump (32); the radiator (3) is fixed on the outside of a fixing frame (6); the circulation pipe (31) is installed between the radiator (3) and the preparation tank (2); the circulation pump (32) is fixed on the fixing frame (6) and aligned with the circulation pipe (31); one end of the circulation pipe (31) located in the preparation tank (2) is a spring-mounted structure and is located outside the stirring rod (25); one end of the circulation pipe (31) located in the radiator (3) is serpentine-shaped.

9. A process for preparing a chrome tanning agent for leather processing according to claim 8, characterized in that: An annular partition (11) is fixed inside the storage tank (1), a filter screen (12) is installed on the annular partition (11), and a vacuum pump (13) is fixed at the upper end of the storage tank (1).

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