Method for coupling ethanol biorefinery and acid mine wastewater source tail end synchronous treatment

Abstract

The invention provides a method for coupling ethanol biorefinery and acid mine wastewater source end synchronous treatment, which comprises the following steps: 1) mixing lignocellulose biomass and acid mine wastewater, and carrying out solid-liquid separation on the treated slurry; (2) washing the solid residues obtained in the step (1) to be neutral, adding a buffer solution and cellulase, and performing solid-liquid separation after enzymolysis to obtain filter residues and filtrate capable of performing ethanol fermentation; and (3) the filter residues in the step (2) and a sodium hydroxide solution are mixed, solid-liquid separation is conducted after treatment, an obtained lignin solution and pyrite are subjected to passivating treatment, solid-liquid separation and freeze drying are conducted after reaction, and passivated pyrite is obtained. Lignocellulose biomass is pretreated by AMD to produce bioethanol, so that green cyclic utilization of resources is realized; the hemicellulose remaining in the AMD serves as an SRB carbon source, AMD sulfate reduction and heavy metal removal are achieved, lignin is used for passivating sulfide ore, and synchronous treatment of the source and the tail end of the AMD is achieved.

Description

Technical Field

[0001] The invention relates to the technical fields of wastewater treatment and ethanol biorefining, and in particular to a method for coupling ethanol biorefining with source-end synchronous treatment of acid mine wastewater. Background Art

[0002] Biofuels are attractive alternatives to fossil fuels due to their renewable properties, with bioethanol being the most common biofuel product. The first generation of bioethanol mainly used glucose extracted from edible starch as a feedstock, which would threaten food supply. To resolve this conflict, the focus has shifted to utilizing inedible and renewable lignocellulosic biomass as a feedstock. However, due to the recalcitrance of lignocellulosic biomass, its conversion into fermentable sugars usually requires a pretreatment step. Dilute acid pretreatment is highly efficient and relatively low cost, so it has been widely used at the industrial level. However, dilute acid pretreatment usually results in wastewater streams rich in H2SO4 and hemicellulose-derived sugars, which will incur huge wastewater treatment costs.

[0003] Acid mine drainage (AMD) is a highly acidic wastewater produced during the oxidation process of sulfide ores. It is characterized by high heavy metal and sulfate content. Improper management will cause serious pollution of soil and water resources and pose a serious threat to human health. The management of AMD is mainly divided into two categories, namely end-of-pipe treatment and source treatment. Among the end-of-pipe treatment technologies, bioremediation has become an effective way to treat AMD due to its good remediation ability. This method mainly relies on sulfate-reducing bacteria (SRB) to reduce sulfate in AMD to hydrogen sulfide, but often requires the input of expensive carbon sources. Among the source treatment technologies, the surface passivation method has a long-lasting preventive effect on AMD and has become a robust technology for preventing the occurrence of AMD. However, the high cost of passivators and passivation processes is the main obstacle to the application of surface passivation.

[0004] Co-processing of lignocellulose and acid mine drainage offers a new approach to waste management and value addition. Summary of the invention

[0005] In view of this, the purpose of the present invention is to provide a method for coupling ethanol biorefining with synchronous source-end treatment of acid mine drainage, which method uses lignocellulosic biomass as raw material, adopts acid mine drainage pretreatment, and then converts cellulose into bioethanol through biological transformation; the hemicellulose released during the pretreatment process can be used as a carbon source for AMD bioremediation; the remaining lignin is used as a passivator to achieve source control of AMD and full utilization of lignocellulosic biomass components.

[0006] The present invention provides a method for coupling ethanol biorefining with synchronous treatment of acid mine wastewater at the source and end, comprising the following steps:

[0007] 1) mixing lignocellulosic biomass and acidic mine wastewater, and performing solid-liquid separation on the treated slurry to obtain solid residues rich in cellulose and lignin and a filtrate rich in hemicellulose;

[0008] 2) washing the solid residue rich in cellulose and lignin in step 1) with water until it is neutral, adding a buffer and cellulase, performing solid-liquid separation after enzymolysis, and obtaining a filter residue and a filtrate rich in fermentable sugars; inoculating the filtrate rich in fermentable sugars with brewer's yeast to perform ethanol fermentation;

[0009] 3) mixing the filter residue in step 2) with a sodium hydroxide solution, treating the mixture and performing solid-liquid separation to obtain a lignin solution; passivating the lignin solution and pyrite, reacting the mixture and performing solid-liquid separation, and freeze-drying the mixture to obtain passivated pyrite.

[0010] Preferably, the treatment temperature in step 1) is 90-120° C. and the treatment time is 1-4 hours.

[0011] Preferably, the enzymatic hydrolysis time in step 2) is 46 to 50 hours; the enzymatic hydrolysis temperature is 45 to 55°C.

[0012] Preferably, the solid content of the mixed solution after adding the buffer and cellulase in step 2) is 10-15%;

[0013] The dosage of cellulase is 5-20 mg / g solid residue.

[0014] Preferably, the concentration of the sodium hydroxide solution in step 3) is 0.05-0.5 mol / L; the solid content of the filter residue after mixing with the sodium hydroxide solution is 5-15%;

[0015] The buffer solution is acetate or citrate buffer solution; the pH value of the buffer solution is 5.0 to 5.5.

[0016] Preferably, in step 3), the temperature of the post-treatment of the filtration residue and the sodium hydroxide solution is 115-125° C. and the time is 55-65 min.

[0017] Preferably, the temperature of the passivation treatment in step 3) is 25-30° C., and the time of the passivation treatment is 230-250 min.

[0018] Preferably, pyrite accounts for 1-2% of the mass of the lignin solution.

[0019] Preferably, the lignocellulosic biomass is selected from one or more of corn cobs, corn straw, wheat straw, rice straw, rape straw and sugarcane bagasse;

[0020] The lignocellulosic biomass accounts for 10-20% of the mass of the acid mine drainage.

[0021] Preferably, the filtrate rich in hemicellulose in step 1) is inoculated with sulfate-reducing bacteria for anaerobic culture treatment.

[0022] The invention provides a method for coupling ethanol biorefining with synchronous treatment of acid mine wastewater at the source and end, comprising the following steps: 1) mixing lignocellulosic biomass and acid mine wastewater, and performing solid-liquid separation on the treated slurry to obtain solid residues rich in cellulose and lignin and filtrate rich in hemicellulose; 2) washing the solid residue rich in cellulose and lignin in step 1) with water until neutral, adding buffer and cellulase, performing solid-liquid separation after enzymolysis, and obtaining filter residue and filtrate rich in fermentable sugar; inoculating brewer's yeast with the filtrate rich in fermentable sugar to perform ethanol fermentation; 3) mixing the filter residue in step 2) with sodium hydroxide solution, performing solid-liquid separation after treatment, and obtaining lignin solution; passivating the lignin solution and pyrite, performing solid-liquid separation after reaction, and freeze-drying to obtain passivated pyrite. The present invention uses acid mine wastewater and renewable lignocellulosic biomass as raw materials to produce bioethanol, thereby realizing green recycling of resources and low-cost management of AMD; the present invention uses cellulose in lignocellulosic biomass to produce ethanol, and uses hemicellulose remaining in AMD after AMD pretreatment of lignocellulosic biomass as a carbon source for SRB, thereby realizing AMD sulfate reduction and heavy metal removal; at the same time, waste lignin is used to passivate sulfide ore, thereby realizing source control of AMD; the full utilization of lignocellulosic biomass components is realized, the utilization rate of lignocellulosic biomass is improved, waste generation is reduced, a new way for AMD management is provided, and the cost of ethanol refineries is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic flow chart of a method for coupling ethanol biorefining with synchronous source-end treatment of acid mine wastewater in a specific embodiment of the present invention. DETAILED DESCRIPTION

[0024] The present invention provides a method for coupling ethanol biorefining with synchronous treatment of acid mine wastewater at the source and end, comprising the following steps:

[0025] 1) mixing lignocellulosic biomass and acid mine drainage (AMD), and performing solid-liquid separation on the treated slurry to obtain a solid residue rich in cellulose and lignin and a filtrate rich in hemicellulose;

[0026] 2) washing the solid residue rich in cellulose and lignin in step 1) with water until it is neutral, adding a buffer and cellulase, performing solid-liquid separation after enzymolysis, and obtaining a filter residue and a filtrate rich in fermentable sugars; inoculating the filtrate rich in fermentable sugars with brewer's yeast to perform ethanol fermentation;

[0027] 3) mixing the filter residue in step 2) with a sodium hydroxide solution, treating the mixture and performing solid-liquid separation to obtain a lignin solution; passivating the lignin solution and pyrite, reacting the mixture and performing solid-liquid separation, and freeze-drying the mixture to obtain passivated pyrite.

[0028] The present invention uses acid mine wastewater and renewable lignocellulosic biomass (such as corn cobs) as raw materials to produce bioethanol, thereby realizing green recycling of resources and low-cost management of AMD; the present invention uses cellulose in lignocellulosic biomass (such as corn cobs) to produce ethanol, and uses the hemicellulose remaining in AMD from AMD pretreatment of lignocellulosic biomass (such as corn cobs) as a carbon source for SRB, thereby realizing AMD sulfate reduction and heavy metal removal; at the same time, the waste lignin is used to passivate sulfide ores, thereby realizing source control of AMD; the full utilization of lignocellulosic biomass (such as corn cobs) is realized, the utilization rate of lignocellulosic biomass (such as corn cobs) is improved, the generation of waste is reduced, a new way of managing AMD is provided, and the cost of ethanol refineries is reduced.

[0029] The invention mixes lignocellulose biomass and acid mine wastewater, and performs solid-liquid separation on the treated slurry to obtain solid residues rich in cellulose and lignin and filtrate rich in hemicellulose.

[0030] The lignocellulosic biomass in the present invention is selected from one or more of corn cobs, corn stalks, wheat stalks, rice stalks, rape stalks and bagasse; the lignocellulosic biomass accounts for 10-20% of the mass of the acid mine drainage. The present invention uses acid mine drainage (AMD) instead of traditional dilute acid to pretreat the lignocellulosic biomass, thereby reducing the cost of pretreatment and subsequent treatment of H2SO4-rich wastewater.

[0031] In the present invention, the temperature of the mixed lignocellulosic biomass and acid mine wastewater treatment is 90-120°C for 1-4 hours. The treated slurry is subjected to solid-liquid separation to obtain solid residues rich in cellulose and lignin and a filtrate rich in hemicellulose.

[0032] The filtrate rich in hemicellulose is inoculated with sulfate-reducing bacteria for anaerobic culture treatment to reduce and remove sulfate and heavy metals in AMD. The inoculation amount of sulfate-reducing bacteria is 20-40% (v / v).

[0033] In the present invention, the solid residue rich in cellulose and lignin obtained in step 1) is washed with water until it becomes neutral, a buffer solution and cellulase are added, and solid-liquid separation is performed after enzymolysis to obtain a filter residue and a filtrate rich in fermentable sugars.

[0034] The solid content of the mixed solution after adding the buffer and the cellulase in the present invention is 10-15%; the buffer is an acetate or citrate buffer; the pH value of the buffer is 5.0-5.5. The dosage of the cellulase in the present invention is 5-20 mg / g solid residue; the cellulase is preferably Novozymes CTec 3. The enzymolysis time in the present invention is 46-50 hours; the enzymolysis temperature is 45-55°C. After the enzymolysis is completed, solid-liquid separation is performed to obtain a lignin-rich filter residue and a filtrate rich in fermentable sugars.

[0035] The filtrate rich in fermentable sugars in the present invention is inoculated with brewer's yeast to carry out ethanol fermentation. The brewer's yeast is Saccharomyces cerevisiae ATCC 26603.

[0036] The invention mixes the filter residue rich in lignin with a sodium hydroxide solution, separates the solid and the liquid after treatment, and obtains a lignin solution; passivates the lignin solution and pyrite, separates the solid and the liquid after reaction, and freeze-dries to obtain the passivated pyrite.

[0037] The concentration of the sodium hydroxide solution in the present invention is 0.05-0.5 mol / L, the solid content of the filter residue after mixing with the sodium hydroxide solution is 5-15%, and the temperature of the treatment after the filter residue and the sodium hydroxide solution are mixed is 115-125°C and the time is 55-65 minutes.

[0038] In the present invention, pyrite accounts for 1-2% of the mass of the lignin solution. The present invention uses lignin extracted from wood fiber biomass waste residue to passivate pyrite, thereby controlling the generation of AMD from the source. Lignin, as a passivating agent, forms a passivation film on the surface of pyrite, thereby reducing or preventing the corrosion of metal mineralization by oxygen or other oxidants, and reducing the formation of AMD. The temperature of the passivation treatment is 25-30°C, and the time of the passivation treatment is 230-250 minutes. After the passivation reaction, the solid and liquid are separated, and the solid residue obtained is freeze-dried to obtain the passivated pyrite.

[0039] The present invention preferably adds the passivated pyrite to a hydrochloric acid solution with a pH of 1 to carry out an acid leaching experiment to verify the passivation efficiency of the pyrite, and the addition amount of the passivated pyrite is 0.6 g / 100 ml of the hydrochloric acid solution.

[0040] Figure 1 FIG. 1 is a schematic diagram of a treatment process for coupling waste biomass straw and acid mine drainage in certain embodiments of the present invention, comprising Figure 1It can be seen that: the lignocellulosic biomass and AMD are mixed and pretreated at 90-120°C for 1-4h, and the solid-liquid is separated to obtain a filtrate and a residue, and the filtrate is subjected to SRB bioremediation; the residue is enzymatically hydrolyzed by cellulase at 55°C for 48h, and the product is subjected to solid-liquid separation to obtain a filtrate and a residue again, and the filtrate is subjected to ethanol fermentation; the residue obtained again is mixed with a 0.2 mol / L NaOH solution, treated at 120°C for 1h, and the solid-liquid is separated to obtain a lignin extract; the lignin extract and pyrite are passivated to obtain passivated pyrite.

[0041] To further illustrate the present invention, a method for coupling ethanol biorefining with synchronous source-end treatment of acid mine wastewater provided by the present invention is described in detail below in conjunction with embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0042] Example 1

[0043] In this embodiment, lignocellulosic biomass ethanol refining and AMD treatment are carried out according to the following steps:

[0044] Step 1: corn cobs are mixed with AMD, with the addition amount of corn cobs being 10%, and treated at 120° C. for 1 hour. The slurry obtained after the treatment is subjected to solid-liquid separation to obtain solid residues rich in cellulose and lignin and a filtrate rich in hemicellulose.

[0045] Step 2: After washing the solid residue in step 1 to neutrality, add buffer and cellulase Novozymes CTec3, so that the solid content in the mixed solution is 10%, and enzymolysis is performed for 48 hours; wherein the amount of cellulase is 20 mg / g solid residue; the buffer is 0.05M acetate buffer, pH is 5.5; the enzymolysis temperature is 50°C; after solid-liquid separation, a filter residue rich in lignin and a filtrate rich in fermentable sugars are obtained, and the filtrate is inoculated with Saccharomyces cerevisiae ATCC 26603 for ethanol fermentation. In this step, the concentration of fermentable sugars in the filtrate is 30 g / L, the ethanol yield is 15 g / L, and the yield is 93.2% of the theoretical yield.

[0046] Step three, the hemicellulose-rich filtrate in step one is inoculated with sulfate-reducing bacteria (inoculation amount is 30%) for anaerobic culture to reduce and remove sulfate and heavy metals in AMD. The sulfate removal rate is 97.2%, and the removal rates of major heavy metals (Mn, Cd, Co, Pb, Ni, Cu) are all over 60%, among which Cd has the highest removal rate of 88.8%.

[0047] Step four, mix the filter residue in step two with 0.2M sodium hydroxide solution with a solid content of 10%, treat at 120℃ for 1h, separate the solid and liquid, and the filtrate is the lignin solution; add pyrite to the lignin solution for passivation treatment for 4h, the pyrite content is 1%, after the reaction, separate the solid and liquid, and freeze-dry the solid residue to obtain the passivated pyrite. The passivated pyrite is added to a hydrochloric acid solution with a pH of 1 for an acid leaching experiment, and the amount of passivated pyrite added is 0.6g / 100ml hydrochloric acid solution. The results show that the passivation efficiency of lignin on pyrite reaches 74.4% calculated based on the total amount of iron released, while the released SO4 2- It was calculated that the passivation efficiency of lignin on pyrite was 74.6%.

[0048] Embodiment 2:

[0049] In this embodiment, lignocellulosic biomass ethanol refining and AMD treatment are carried out according to the following steps:

[0050] Step 1: corn cobs are mixed with AMD, with the addition amount of corn cobs being 15%, and treated at 90° C. for 4 hours. The slurry obtained after the treatment is subjected to solid-liquid separation to obtain solid residues rich in cellulose and lignin and a filtrate rich in hemicellulose.

[0051] Step 2: After washing the solid residue in step 1 to neutrality, add buffer and cellulase to make the solid content in the mixed solution 10%, and perform enzymolysis for 48 hours; wherein the amount of cellulase is 5 mg / g solid residue; the buffer is 0.05M acetate buffer, pH is 5.5; the enzymolysis temperature is 45°C; after solid-liquid separation, a filtrate rich in lignin and a filtrate rich in fermentable sugars are obtained, and the filtrate is inoculated with Saccharomyces cerevisiae ATCC 26603 for ethanol fermentation. In this step, the concentration of fermentable sugars in the filtrate is 28 g / L, the ethanol yield is 14 g / L, and the yield is 93.2% of the theoretical yield.

[0052] Step three, the hemicellulose-rich filtrate in step one was inoculated with sulfate-reducing bacteria (inoculation amount was 20%) for anaerobic culture to reduce and remove sulfate and heavy metals in AMD. The sulfate removal rate was 96.8%, and the removal rates of major heavy metals (Mn, Cd, Co, Pb, Ni, Cu) were all over 60%, among which the removal rate of Cd was the highest, at 86.7%.

[0053] Step four, mix the filter residue in step two with 0.05M sodium hydroxide solution with a solid content of 5%, treat at 120℃ for 1h, separate the solid and liquid, and the filtrate is the lignin solution; add pyrite to the lignin solution for passivation treatment for 4h, the pyrite content is 1%, after the reaction is completed, separate the solid and liquid, and freeze-dry the solid residue to obtain the passivated pyrite. The passivated pyrite is added to a hydrochloric acid solution with a pH of 1 for an acid leaching experiment, and the amount of passivated pyrite added is 0.6g / 100ml hydrochloric acid solution. The results show that the passivation efficiency of lignin on pyrite reaches 71.8% calculated based on the total amount of iron released, while the released SO4 2- It was calculated that the passivation efficiency of lignin on pyrite was 72.1%.

[0054] Embodiment 3:

[0055] In this embodiment, lignocellulosic biomass ethanol refining and AMD treatment are carried out according to the following steps:

[0056] Step 1: corn cobs are mixed with AMD, with the addition amount of corn cobs being 20%, and treated at 110° C. for 2 hours. The slurry obtained after the treatment is subjected to solid-liquid separation to obtain solid residues rich in cellulose and lignin and a filtrate rich in hemicellulose.

[0057] Step 2: After washing the solid residue in step 1 to neutrality, add buffer and cellulase to make the solid content in the mixed solution 15%, and perform enzymolysis for 48 hours; wherein the amount of cellulase is 15 mg / g solid residue; the buffer is 0.05M acetate buffer, pH is 5.5; the enzymolysis temperature is 55°C; after solid-liquid separation, a filtrate rich in lignin and a filtrate rich in fermentable sugars are obtained, and the filtrate is inoculated with Saccharomyces cerevisiae ATCC 26603 for ethanol fermentation. In this step, the concentration of fermentable sugars in the filtrate is 35 g / L, the ethanol yield is 17 g / L, and the yield is 95.1% of the theoretical yield.

[0058] Step three, the hemicellulose-rich filtrate in step one is inoculated with sulfate-reducing bacteria (inoculation amount is 40%) for anaerobic culture to reduce and remove sulfate and heavy metals in AMD. The sulfate removal rate is 97.6%, and the removal rates of major heavy metals (Mn, Cd, Co, Pb, Ni, Cu) are all over 60%, among which Cd has the highest removal rate of 83.2%.

[0059] Step four, mix the filter residue in step two with 0.5M sodium hydroxide solution with a solid content of 15%, treat at 120℃ for 1h, separate the solid and liquid, and the filtrate is the lignin solution; add pyrite to the lignin solution for passivation treatment for 4h, the pyrite content is 2%, after the reaction is completed, separate the solid and liquid, and freeze-dry the solid residue to obtain the passivated pyrite. The passivated pyrite is added to a hydrochloric acid solution with a pH of 1 for an acid leaching experiment, and the amount of passivated pyrite added is 0.6g / 100ml hydrochloric acid solution. The results show that the passivation efficiency of lignin on pyrite reaches 72.3% calculated based on the total amount of iron released, while the released SO4 2- It was calculated that the passivation efficiency of lignin on pyrite was 73.3%.

[0060] It can be seen from the above embodiments that the present invention provides a method for coupling ethanol biorefining with synchronous treatment of acid mine drainage at the source and end, comprising the following steps: 1) mixing lignocellulosic biomass and acid mine drainage, and performing solid-liquid separation on the treated slurry to obtain solid residues rich in cellulose and lignin and filtrate rich in hemicellulose; 2) washing the solid residue rich in cellulose and lignin described in step 1) with water until neutral, adding buffer and cellulase, performing solid-liquid separation after enzymolysis, and obtaining filter residue and filtrate rich in fermentable sugars; inoculating the filtrate rich in fermentable sugars with brewer's yeast to perform ethanol fermentation; 3) mixing the filter residue described in step 2) with sodium hydroxide solution, performing solid-liquid separation after treatment, and obtaining lignin solution; passivating the lignin solution and pyrite, performing solid-liquid separation after reaction, and freeze-drying to obtain passivated pyrite. The present invention uses the renewable lignocellulosic biomass obtained by acid mine wastewater pretreatment as raw material to produce bioethanol, thus achieving green recycling of resources and low-cost management of AMD. The present invention uses the cellulose in the lignocellulosic biomass to produce ethanol, and the hemicellulose remaining in the AMD of the AMD pretreated lignocellulosic biomass is used as the carbon source of SRB, thus achieving AMD sulfate reduction and heavy metal removal. Meanwhile, the waste lignin is used to passivate sulfide ores, thus achieving simultaneous source-end management of AMD. The full quantitative utilization of lignocellulosic biomass components is achieved, the utilization rate of lignocellulosic biomass is improved, waste generation is reduced, a new way of managing AMD is provided, and the cost of ethanol refineries is reduced. The experimental results show that the passivation efficiency of lignin on pyrite is 71.8-74.4% (in terms of released SO4 2- The theoretical yield of ethanol is 93.2-95.1%; the removal rate of Cd in AMD is 83.2-88.8%.

[0061] 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 coupling ethanol biorefining with synchronous head-end treatment of acid mine drainage, comprising the following steps: 1) mixing lignocellulosic biomass and acidic mine wastewater, and performing solid-liquid separation on the treated slurry to obtain solid residues rich in cellulose and lignin and a filtrate rich in hemicellulose; 2) washing the solid residue rich in cellulose and lignin in step 1) with water until it is neutral, adding a buffer and cellulase, performing solid-liquid separation after enzymolysis, and obtaining a filter residue and a filtrate rich in fermentable sugars; inoculating the filtrate rich in fermentable sugars with brewer's yeast to perform ethanol fermentation; 3) mixing the filter residue in step 2) with a sodium hydroxide solution, treating the mixture and performing solid-liquid separation to obtain a lignin solution; passivating the lignin solution and pyrite, reacting the mixture and performing solid-liquid separation, and freeze-drying the mixture to obtain passivated pyrite.

2. The method according to claim 1, characterized in that The treatment temperature in step 1) is 90-120° C. and the treatment time is 1-4 hours.

3. The method according to claim 1, characterized in that: The enzymatic hydrolysis time in step 2) is 46 to 50 hours; the enzymatic hydrolysis temperature is 45 to 55°C.

4. The method according to claim 1, characterized in that: The solid content of the mixed solution after adding the buffer in step 2) is 10-15%; The dosage of cellulase is 5-20 mg / g solid residue.

5. The method according to claim 1, characterized in that In step 3), the concentration of the sodium hydroxide solution is 0.05-0.5 mol / L; the solid content after the filter residue and the sodium hydroxide solution are mixed is 5-15%; The buffer solution is acetate or citrate buffer solution; the pH value of the buffer solution is 5.0 to 5.

5.

6. The method according to claim 1, characterized in that In step 3), the temperature of the treatment after the filtration residue and the sodium hydroxide solution are mixed is 115-125° C. and the time is 55-65 minutes.

7. The method according to claim 1, characterized in that The temperature of the passivation treatment in step 3) is 25-30° C., and the time of the passivation treatment is 230-250 min.

8. The method according to claim 1, characterized in that: Pyrite accounts for 1-2% of the mass of the lignin solution.

9. The method according to claim 1, characterized in that: The lignocellulosic biomass is selected from one or more of corn cobs, corn straw, wheat straw, rice straw, rape straw and sugarcane bagasse; The lignocellulosic biomass accounts for 10-20% of the mass of the acid mine drainage.

10. The method according to claim 1, characterized in that The filtrate rich in hemicellulose in step 1) is inoculated with sulfate-reducing bacteria at an inoculation amount of 20-40% and subjected to anaerobic culture treatment.

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