Method for leaching chromium in high-chromium tanning sludge

Abstract

The invention provides a method for leaching chromium in high-chromium tanning sludge, and belongs to the technical field of treatment of heavy metals in leather tanning sludge. The method comprises the following steps: mixing the high-chromium tannery sludge with dilute sulphuric acid, and carrying out acid leaching to obtain a chemical leaching solution and chemical leaching residues; diluting the chemical leaching residues, inoculating domesticated composite thiobacillus species, adjusting the pH value, adding a nutritional agent, and carrying out bioleaching to obtain a bioleaching solution and bioleaching residues; and finally, mixing the chemical leachate, the biological leachate, a sulfuric acid solution, a sodium dichromate solution and a glucose solution, adjusting the alkalinity, and stirring to obtain the chrome tanning agent. According to the method for leaching the chromium in the high-chromium tanning sludge, the removal rate of the chromium can reach 99% or above, the effect is remarkably superior to that of a single process, the method is a feasible and optimal process at the current stage, the chromium leaching solution is further processed and treated and enters a chromium tanning section to serve as a chromium tanning agent, and cyclic utilization is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of heavy metal treatment in leather tanning sludge, in particular to a method for leaching chromium from high-chromium leather tanning sludge. Background Art

[0002] More than 90% of leather production is tanned with chromium salts, but only 60% of the chromium can react with leather. The remaining chromium enters the tanning sludge through wastewater discharge, posing a potential risk of environmental pollution. Tanning sludge is composed of a variety of complex components, among which the content of heavy metal chromium far exceeds the maximum limit stipulated by the state. High concentrations of chromium can cause damage to soil, freshwater environment, aquatic life and human body. The treatment and disposal of high-chromium tanning sludge is a challenging topic. Although traditional physical and chemical treatment methods can achieve the removal of chromium, they are often accompanied by high costs and secondary pollution. Therefore, finding a chromium removal technology that is both environmentally friendly and efficient is a current research hotspot.

[0003] The chemical acid leaching method has low selectivity and stable removal rate. It can remove most of the heavy metals in the tannery sludge in a short time, and the Cr removal rate can reach 60-80%. However, it consumes a lot of acid, is costly, and produces secondary pollution during the treatment process. Bioleaching technology has the characteristics of low cost, low energy consumption and environmental friendliness, but it has the disadvantages of unstable removal rate, long time consumption and low leaching efficiency in the treatment of high-chromium tannery sludge. After single chemical acid leaching and bioleaching to treat high-chromium tannery sludge, the leaching toxicity of the residue cannot stably meet the general solid waste standard requirements, which limits its engineering promotion and application. Therefore, it is urgent to develop an economical, efficient and environmentally friendly chromium removal technology to solve the above-mentioned traditional technical problems. Summary of the invention

[0004] The object of the present invention is to provide a method for leaching chromium from high-chromium tannery sludge, so as to solve the problems of high cost of removing chromium from high-chromium tannery sludge, long leaching cycle and easy secondary pollution in the prior art.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a method for leaching chromium from high-chromium leather sludge, comprising the following steps:

[0007] (1) mixing high-chromium tanning sludge and dilute sulfuric acid and then performing acid leaching to obtain a chemical leaching solution and a chemical leaching residue;

[0008] (2) The chemical leaching residue is diluted and inoculated with the domesticated compound Thiobacillus species, the pH value is adjusted, and nutrients are added to perform bioleaching to obtain a bioleaching solution and a bioleaching residue.

[0009] (3) The chemical leaching solution, the biological leaching solution, the sulfuric acid solution, the sodium dichromate solution and the glucose solution are mixed, and the alkalinity is adjusted and then stirred to obtain a chrome tanning agent.

[0010] Preferably, in the step (1), the dosage ratio of high-chromium chromium-making sludge to dilute sulfuric acid is 1 g:10-30 mL; and the concentration of the dilute sulfuric acid is 0.25-1.2 mol / L.

[0011] Preferably, in step (1), the acid leaching temperature is 20-50° C., the acid leaching time is 30-140 min, and the acid leaching oscillation speed is 100-300 rpm.

[0012] Preferably, in the step (2), the solid content of the diluted chemical leaching residue is 0.5-5%; the acclimated composite Thiobacillus species comprises Thiobacillus ferrooxidans and Thiobacillus thiooxidans; and the inoculation amount of the acclimated composite Thiobacillus species is 5-25%.

[0013] Preferably, the inoculation ratio of Thiobacillus ferrooxidans to Thiobacillus thiooxidans is 1-4:1-3.

[0014] Preferably, in step (2), the adjusted pH value is 3-5; the nutrients are ferrous sulfide and elemental sulfur; the temperature of the bioleaching is 25-30°C, and the oscillation speed of the bioleaching is 160-200 rpm.

[0015] Preferably, in step (3), the concentration of the sulfuric acid solution is 0.2-0.4 mol / L, the concentration of the sodium dichromate solution is 0.06-0.15 mol / L, and the concentration of the glucose solution is 0.11-0.22 mol / L.

[0016] Preferably, in step (3), the amount of sulfuric acid solution added is 1-3% of the total volume of the chemical leaching solution and the biological leaching solution, the amount of sodium dichromate solution added is 1-2% of the total volume of the chemical leaching solution and the biological leaching solution, and the amount of glucose solution added is 0.1-1% of the total volume of the chemical leaching solution and the biological leaching solution.

[0017] Preferably, in step (3), the adjusted alkalinity is 18-25%.

[0018] Preferably, in step (3), the stirring temperature is 90-120° C., the stirring time is 90-120 min, and the shaking speed is 180-220 rpm.

[0019] Beneficial effects of the present invention:

[0020] (1) The present invention first adopts the method of chemical acid leaching to effectively destroy the chromium adsorption equilibrium and the chemical form of chromium, creating favorable conditions for the biological treatment stage. On the basis of chemical acid leaching, the domesticated composite thiobacillus is used for bioleaching, and its redox ability is used to further promote the dissolution and removal of Cr. The remaining chromium remains in a more stable form, realizing the transformation of hazardous waste with high heavy metal content into general solid waste. Through the method of coordinated leaching of chemical acid leaching and bioleaching, the surface morphology and particle structure of high-chromium leather sludge change significantly. The space left after acid leaching dissolves the chromium compounds further promotes bioleaching. Bioleaching further improves the leaching rate of chromium and reduces the potential toxicity to the environment by releasing metal ions and degrading organic matrices.

[0021] (2) The method for leaching chromium from high-chromium leather sludge of the present invention combines the rapid reaction of chemical acid leaching with the environmental friendliness of biological leaching, and the chromium removal rate can be as high as 99% or more. The effect is significantly better than that of a single process. It is a feasible and optimal process at the current stage. The chromium leachate is further processed and treated and enters the chrome tanning section as a chrome tanning agent to achieve recycling.

[0022] (3) The chromium leaching method of the present invention can reduce the potential threat of high-chromium leather sludge to the environment, and the leached residue meets the national standard requirements for general solid waste. The leaching toxicity of the sludge treated by the combined method can meet the concentration limit requirements of hazardous components in the "Hazardous Waste Identification Standard Leaching Toxicity Identification" (GB 5085.3-2007), realizing the transformation of hazardous waste with high heavy metal content into general solid waste, which can greatly save the cost of leather sludge hazardous waste treatment and realize the resource utilization of sludge. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The present invention is a process flow chart of chromium leaching from high-chromium leather sludge. DETAILED DESCRIPTION

[0024] The present invention provides a method for leaching chromium from high-chromium leather sludge, comprising the following steps:

[0025] (1) mixing high-chromium tanning sludge and dilute sulfuric acid and then performing acid leaching to obtain a chemical leaching solution and a chemical leaching residue;

[0026] (2) The chemical leaching residue is diluted and inoculated with the domesticated compound Thiobacillus species, the pH value is adjusted, and nutrients are added to perform bioleaching to obtain a bioleaching solution and a bioleaching residue.

[0027] (3) The chemical leaching solution, the biological leaching solution, the sulfuric acid solution, the sodium dichromate solution and the glucose solution are mixed, the alkalinity is adjusted and the mixture is stirred to obtain a chrome tanning agent.

[0028] In the present invention, the usage ratio of high-chromium chromium-making sludge and dilute sulfuric acid is 1g:10-30mL, preferably 1g:20-30mL; the concentration of the dilute sulfuric acid is 0.25-1.2mol / L, preferably 0.5-1.0mol / L, and more preferably 0.75-1.0mol / L.

[0029] In the present invention, in the step (1), the acid leaching temperature is 20 to 50°C, preferably 20 to 40°C, the acid leaching time is 30 to 140 min, preferably 60 to 120 min, more preferably 90 to 120 min, and the acid leaching oscillation speed is 100 to 300 rpm, preferably 150 to 250 rpm, more preferably 200 rpm.

[0030] In the present invention, in the step (2), the solid content of the diluted chemical leaching residue is 0.5-5%, preferably 1-4%; the domesticated composite Thiobacillus species comprises Thiobacillus ferrooxidans and Thiobacillus thiooxidans; the inoculation amount of the domesticated composite Thiobacillus species is 5-25%, preferably 5-15%, and more preferably 10%.

[0031] In the present invention, the inoculation ratio of Thiobacillus ferrooxidans to Thiobacillus thiooxidans is 1-4:1-3, preferably 2-4:1-2, and more preferably 2:1.

[0032] In the present invention, the Thiobacillus ferrooxidans and Thiobacillus thiooxidans are domesticated respectively, and the domestication method is preferably: (1) culturing and enriching fresh sludge in a culture medium until the enrichment is completed when the pH value is less than 2.0, and screening to obtain acidophilic Thiobacillus ferrooxidans or Thiobacillus thiooxidans; (2) inoculating bacterial liquid in high-chromium leather sludge for domestication and culturing until the pH value drops to 2.0 and the domestication is completed, and the domestication is repeated three times to obtain acidified sludge; (3) the bacterial liquid obtained from the acidified sludge is cultured again in a liquid culture medium to obtain domesticated Thiobacillus ferrooxidans or Thiobacillus thiooxidans, wherein the liquid culture medium used for domesticating Thiobacillus ferrooxidans is a 9k liquid culture medium, and the liquid culture medium used for domesticating Thiobacillus thiooxidans is a Waksman liquid culture medium.

[0033] In the present invention, in the step (2), the adjusted pH value is 3 to 5, preferably 4; the nutrients are ferrous sulfide and elemental sulfur; the temperature of the bioleaching is 25 to 30°C, preferably 26 to 29°C, and more preferably 27 to 28°C; the oscillation speed of the bioleaching is 160 to 200 rpm, preferably 170 to 190 rpm, and more preferably 180 rpm.

[0034] In the present invention, the addition amount of ferrous sulfide is preferably 2-6 g / L, preferably 3-5 g / L, and more preferably 4 g / L; the addition amount of elemental sulfur is preferably 1-5 g / L, preferably 2-4 g / L, and more preferably 3 g / L.

[0035] In the present invention, in step (3), the concentration of the sulfuric acid solution is 0.2-0.4 mol / L, preferably 0.25-0.38 mol / L, and more preferably 0.3-0.38 mol / L; the concentration of the sodium dichromate solution is 0.06-0.15 mol / L, preferably 0.08-0.12 mol / L, and more preferably 0.10-0.12 mol / L; the concentration of the glucose solution is 0.11-0.22 mol / L, preferably 0.12-0.20 mol / L, and more preferably 0.18-0.20 mol / L.

[0036] In the present invention, in the step (3), the amount of sulfuric acid solution added accounts for 1-3% of the total volume of the chemical leaching solution and the biological leaching solution, preferably 2%; the amount of sodium dichromate solution added accounts for 1-2% of the total volume of the chemical leaching solution and the biological leaching solution, preferably 1.2-1.8%, and more preferably 1.4-1.6%; the amount of glucose solution added accounts for 0.1-1% of the total volume of the chemical leaching solution and the biological leaching solution, preferably 0.3-0.8%, and more preferably 0.5-0.7%.

[0037] In the present invention, in step (3), the adjusted alkalinity is 18-25%, preferably 20-23%. In the embodiment of the present invention, sodium carbonate is preferably added to adjust the alkalinity.

[0038] In the present invention, in the step (3), the stirring temperature is 90-120°C, preferably 95-115°C, and more preferably 110-115°C; the time is 90-120min, preferably 95-110min, and more preferably 100-110min; the oscillation speed is 180-220rpm, preferably 190-210rpm, and more preferably 200rpm.

[0039] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0040] Example 1

[0041] In a 150mL conical flask, high-chromium leather sludge (chromium content of 20.51g / kg) and dilute sulfuric acid (concentration of 0.75mol / L) were added in a ratio of 1g:30mL. The conical flask was sealed and placed in a constant temperature water bath oscillator. The acid was leached for 120min at 40°C and an oscillation speed of 200rpm, followed by centrifugal separation and filtration to obtain a chemical leaching solution and a chemical leaching residue.

[0042] Fresh sludge was used as seed sludge for culture enrichment in sterilized 9k or Waksman liquid culture medium until the enrichment was completed when the pH value of the sludge was less than 2.0. Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans were obtained through screening, and then they were domesticated in high-chromium chromium-making sludge respectively: the pH value of 135mL high-chromium chromium-making sludge culture medium (solid content of 1%) was adjusted to 4, 15mL of bacterial solution was inoculated, and the culture was placed in a constant temperature water bath oscillator at 28°C and an oscillation speed of 180rpm for domestication and culture. During the process, the water loss caused by evaporation was supplemented by weighing method every two days. The pH value dropped to 2.0 as the end point of domestication. The above domestication process was repeated 3 times to finally obtain acidified sludge. 1mL of the bacterial solution after domestication was taken and cultured in 100mL of sterilized 9k or Waksman liquid culture medium to obtain domesticated Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans. Table 1 shows the components of 9k and Waksman liquid culture medium:

[0043] Table 19 Composition of K and Waksman liquid media

[0044]

[0045]

[0046] The chemical leaching residue was diluted with water to make the solid content of 1%, 135 mL of the diluted chemical leaching residue was placed in a 250 mL conical flask, and the acclimated composite thiobacillus was added according to an inoculum amount of 10% (the inoculum amount ratio of ferrous thiobacillus and thiothiobacillus oxidans was 2:1), the pH value was adjusted to 4, nutrients were added (the nutrients were ferrous sulfide and sulfur, wherein the addition amount of ferrous sulfide was 4 g / L and the addition amount of SO was 3 g / L), the conical flask was sealed with gauze and placed on a constant temperature shaker, and bioleaching was carried out at 28° C. and an oscillation speed of 180 rpm. During the process, the water loss caused by evaporation was supplemented by weighing method every two days, and the pH value and redox potential (ORP) were detected every two days until the pH value dropped below 2 and remained stable, and the reaction was considered to be completed, and then centrifuged at a speed of 10000 rpm for 10 min to obtain bioleaching residue and bioleaching solution.

[0047] The chemical leaching solution and the biological leaching solution are mixed, 100 mL of the mixed solution is placed in a 150 mL conical flask, 2 mL of 0.38 mol / L sulfuric acid solution is added, and then 1.4 mL of 0.12 mol / L sodium dichromate solution and 0.5 mL of 0.20 mol / L glucose solution are added, and after mixing, sodium carbonate is added to adjust the alkalinity to 20%, and then it is placed in a constant temperature water bath oscillator, stirred for 100 minutes at 115°C and an oscillation speed of 200 rpm to obtain a chrome tanning agent, which can enter the chrome tanning section for recycling.

[0048] Example 2

[0049] In a 150mL conical flask, high-chromium leather sludge (chromium content of 20.51g / kg) and dilute sulfuric acid (concentration of 0.75mol / L) were added in a ratio of 1g:20mL. The conical flask was sealed and placed in a constant temperature water bath oscillator. The acid was leached for 90min at 20°C and an oscillation speed of 200rpm, followed by centrifugal separation and filtration to obtain a chemical leaching solution and a chemical leaching residue.

[0050] The domestication process of the strains is the same as in Example 1.

[0051] The chemical leaching residue was diluted with water to make the solid content of 1%, 135 mL of the diluted chemical leaching residue was placed in a 250 mL conical flask, and the acclimated composite thiobacillus was added according to an inoculum amount of 5% (the inoculum ratio of thiobacillus ferrooxidans and thiobacillus thiooxidans was 4:1), the pH value was adjusted to 3, nutrients were added (the nutrients were ferrous sulfide and sulfur, wherein the addition amount of ferrous sulfide was 4 g / L and the addition amount of SO was 3 g / L), the conical flask was sealed with gauze and placed on a constant temperature shaker, and bioleaching was carried out at 28° C. and an oscillation speed of 180 rpm. During the process, the water loss caused by evaporation was supplemented by weighing method every two days, and the pH value and redox potential (ORP) were detected every two days until the pH value dropped below 2 and remained stable, and the reaction was considered to be completed, and then centrifuged at a speed of 10000 rpm for 10 min to obtain bioleaching residue and bioleaching solution.

[0052] The chemical leaching solution and the biological leaching solution are mixed, 100 mL of the mixed solution is placed in a 150 mL conical flask, 2 mL of 0.30 mol / L sulfuric acid solution is added, and then 1.4 mL of 0.10 mol / L sodium dichromate solution and 0.5 mL of 0.18 mol / L glucose solution are added. After mixing, sodium carbonate is added to adjust the alkalinity to 23%, and then it is placed in a constant temperature water bath oscillator, stirred for 110 minutes at 110°C and an oscillation speed of 200 rpm to obtain a chrome tanning agent, which can enter the chrome tanning section for recycling.

[0053] Example 3

[0054] In a 150mL conical flask, high-chromium leather sludge (chromium content of 20.51g / kg) and dilute sulfuric acid (concentration of 1.0mol / L) were added in a ratio of 1g:30mL. The conical flask was sealed and placed in a constant temperature water bath oscillator. The acid was leached for 120min at 20°C and an oscillation speed of 200rpm, followed by centrifugal separation and filtration to obtain a chemical leaching solution and a chemical leaching residue.

[0055] The domestication process of the strains is the same as in Example 1.

[0056] The chemical leaching residue was diluted with water to make the solid content of 1%, 135 mL of the diluted chemical leaching residue was placed in a 250 mL conical flask, and the acclimated composite thiobacillus was added according to an inoculum amount of 15% (the inoculum amount ratio of ferrous thiobacillus and thiothiobacillus oxidans was 1:2), the pH value was adjusted to 5, nutrients were added (the nutrients were ferrous sulfide and sulfur, wherein the addition amount of ferrous sulfide was 4 g / L and the addition amount of SO was 3 g / L), the conical flask was sealed with gauze and placed on a constant temperature shaker, and bioleaching was carried out at 28° C. and an oscillation speed of 180 rpm. During the process, the water loss caused by evaporation was supplemented by weighing method every two days, and the pH value and oxidation-reduction potential (ORP) were detected every two days until the pH value dropped below 2 and remained stable, and the reaction was considered to be completed, and then centrifuged at a speed of 10000 rpm for 10 min to obtain bioleaching residue and bioleaching solution.

[0057] The chemical leaching solution and the biological leaching solution are mixed, 100 mL of the mixed solution is placed in a 150 mL conical flask, 2 mL of 0.20 mol / L sulfuric acid solution is added, and then 1.4 mL of 0.08 mol / L sodium dichromate solution and 0.5 mL of 0.12 mol / L glucose solution are added. After mixing, sodium carbonate is added to adjust the alkalinity to 18%, and then it is placed in a constant temperature water bath oscillator, stirred for 105 min at 95°C and an oscillation speed of 200 rpm to obtain a chrome tanning agent, which can enter the chrome tanning section for recycling.

[0058] Comparative Example 1

[0059] The domestication process of the strains is the same as in Example 1.

[0060] In a 250mL conical flask, 135mL of high-chromium tannery sludge with a solid content of 1% (chromium content of 20.51g / kg) was added, and the domesticated composite thiobacillus was added according to an inoculum size of 10% (the inoculum size ratio of ferrous thiobacillus and thiothiobacillus oxidans was 2:1), the pH value was adjusted to 4, nutrients were added (the nutrients were ferrous sulfide and elemental sulfur, wherein the addition amount of ferrous sulfide was 4g / L and the addition amount of SO was 3g / L), the conical flask was sealed with gauze and placed on a constant temperature shaker, and bioleaching was carried out at 28°C and an oscillation speed of 180rpm. During the process, the water loss caused by evaporation was supplemented by weighing method every two days, and the pH value and redox potential (ORP) were detected every two days until the pH value dropped below 2 and remained stable, which was considered to be the end of the reaction, and then centrifuged at a speed of 10000rpm for 10min to obtain bioleaching residue and bioleaching solution.

[0061] The bioleaching residue was dried at 105°C, and the bioleaching residue and 0.75 mol / L dilute sulfuric acid (solid-liquid ratio of 1 g:30 mL) were added to a 150 mL conical flask. The conical flask was sealed and placed in a constant temperature water bath oscillator. The acid was leached for 120 min at 40°C and an oscillation speed of 200 rpm, followed by centrifugal separation and filtration to obtain a chemical leaching solution and a chemical leaching residue.

[0062] The leaching test of the final leaching residue in Examples 1 to 3 and Comparative Example 1 was carried out according to the national standard GB 5085.3-2007, i.e., Solid Waste—Leaching Toxicity Leaching Procedure, using the solid waste leaching toxicity method to measure the total Cr concentration and Cr 6+ The specific test results are shown in Table 2.

[0063] Table 2 Chromium concentration test results

[0064]

[0065]

[0066] It can be seen from Table 2 that the chemical leaching residues and biological leaching residues meet the standard limits of GB5085.3-2007 and meet the national standard requirements for general solid waste.

[0067] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for leaching chromium from high-chromium leather sludge, characterized in that: The steps include: (1) mixing high-chromium tanning sludge and dilute sulfuric acid and then performing acid leaching to obtain a chemical leaching solution and a chemical leaching residue; (2) diluting the chemical leaching residue and inoculating the acclimated composite Thiobacillus species, adjusting the pH value and adding nutrients, and performing bioleaching to obtain a bioleaching solution and a bioleaching residue; (3) The chemical leaching solution, the biological leaching solution, the sulfuric acid solution, the sodium dichromate solution and the glucose solution are mixed, the alkalinity is adjusted and the mixture is stirred to obtain a chrome tanning agent.

2. The method for leaching chromium from high-chromium tannery sludge according to claim 1, characterized in that: In the step (1), the usage ratio of high-chromium chromium-making sludge and dilute sulfuric acid is 1 g: 10-30 mL; and the concentration of the dilute sulfuric acid is 0.25-1.2 mol / L.

3. The method for leaching chromium from high-chromium leather sludge according to claim 2, characterized in that: In the step (1), the acid leaching temperature is 20 to 50° C., the acid leaching time is 30 to 140 minutes, and the acid leaching oscillation speed is 100 to 300 rpm.

4. The method for leaching chromium from high-chromium tannery sludge according to any one of claims 1 to 3, characterized in that: In the step (2), the solid content of the chemical leaching residue after dilution is 0.5-5%; the acclimated composite thiobacillus species comprises thiobacillus ferrooxidans and thiobacillus thiooxidans; and the inoculation amount of the acclimated composite thiobacillus species is 5-25%.

5. The method for leaching chromium from high-chromium tannery sludge according to claim 4, characterized in that: The inoculation ratio of Thiobacillus ferrooxidans to Thiobacillus thiooxidans is 1-4:1-3.

6. The method for leaching chromium from high-chromium tannery sludge according to claim 3 or 5, characterized in that: In the step (2), the adjusted pH value is 3-5; the nutrients are ferrous sulfide and elemental sulfur; the temperature of the bioleaching is 25-30° C., and the oscillation speed of the bioleaching is 160-200 rpm.

7. The method for leaching chromium from high-chromium tannery sludge according to claim 6, characterized in that: In the step (3), the concentration of the sulfuric acid solution is 0.2-0.4 mol / L, the concentration of the sodium dichromate solution is 0.06-0.15 mol / L, and the concentration of the glucose solution is 0.11-0.22 mol / L.

8. The method for leaching chromium from high-chromium tannery sludge according to claim 7, characterized in that: In the step (3), the amount of sulfuric acid solution added is 1-3% of the total volume of the chemical leaching solution and the biological leaching solution, the amount of sodium dichromate solution added is 1-2% of the total volume of the chemical leaching solution and the biological leaching solution, and the amount of glucose solution added is 0.1-1% of the total volume of the chemical leaching solution and the biological leaching solution.

9. The method for leaching chromium from high-chromium leather sludge according to claim 5 or 7, characterized in that: In the step (3), the adjusted alkalinity is 18-25%.

10. The method for leaching chromium from high-chromium tannery sludge according to claim 9, characterized in that: In the step (3), the stirring temperature is 90-120° C., the stirring time is 90-120 min, and the shaking speed is 180-220 rpm.

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