Preparation method and application of coal-based biochar

Abstract

The invention discloses a preparation method and application of coal-based biochar. Comprising the following steps: washing anthracite until the pH is neutral, and sequentially drying and sieving; placing the sieved anthracite in the activation solution for standing; after standing, drying the anthracite; the anthracite is placed in a heating furnace to be heated for the first time, and first heating is carried out; heating for the second time after the first heating is finished, and heating for the second time; and washing the anthracite heated for the second time until the pH value is 6.5-7.5, and then sequentially drying, crushing and sieving to obtain the coal-based biochar. According to the coal-based biochar, a layer of compact and stable passivation film can be constructed on the surface of pyrite, contact between water, dissolved oxygen and various positive ions and the surface of mineral is effectively blocked, and therefore the way of oxidation reaction is cut off from the source.

Description

Technical Field

[0001] This invention relates to the field of biochar technology, specifically to a method for preparing coal-based biochar and its application. Background Technology

[0002] The mining industry has made significant contributions to global economic development, but it has also generated a series of environmental risks, such as acid mine wastewater (AMD). During the oxidation process of pyrite (FeS2), it reacts with oxygen and water to produce sulfuric acid and sulfites, resulting in acidic wastewater. This acidic wastewater not only pollutes surface and groundwater but also dissolves heavy metals (such as iron, zinc, copper, and cadmium), damaging the ecological environment and causing serious human health problems. While the global production of AMD cannot be accurately estimated at present, every ton of ore mined generates one cubic meter of acidic wastewater, polluting surface and groundwater and surrounding soil, posing a significant ecological threat, and also contributing to SO4 production. 2- High concentrations and extreme difficulty in treatment constitute the most serious environmental pollution from mines. Even worse, high concentrations of sulfate ions enter the mineral processing system through wastewater, causing severe pipe scaling and corrosion, increasing water and energy consumption, and further restricting production activities. Therefore, the control and treatment of AMD generated during mining production is urgently needed.

[0003] Biochar is a porous carbonaceous material obtained through the thermochemical conversion of carbohydrate-rich biomass under oxygen-limited conditions. Due to its large specific surface area, porous structure, and abundant surface functional groups, biochar can not only adsorb large amounts of heavy metals and bacteria from wastewater but also catalyze some chemical reactions in wastewater, such as nitrogen and phosphorus removal. Furthermore, biochar's high specific surface area and excellent adsorption performance can effectively neutralize acidic components in wastewater and, through its physical barrier effect, inhibit sulfur oxidation, reducing the generation of acidic wastewater and further reducing the leaching of heavy metals.

[0004] In the area of ​​sulfur and acid reduction at the source of pyrite, reported passivating agents include silicates, phospholipids, phosphates, and triethylenetetramine. However, these materials all have significant limitations that restrict their practical application. For example, while phosphates, silicates, and phospholipids can form coatings on surfaces, their film-forming process relies on pre-oxidation of sulfide minerals with H2O2. This additional step significantly increases process complexity and operating costs, making large-scale engineering applications difficult. On the other hand, triethylenetetramine, due to its strong biotoxicity, may negatively impact surrounding ecosystems and microbial communities, exhibiting poor environmental compatibility and thus being unsuitable for field-scale use. In summary, existing passivating agent materials still have significant shortcomings in terms of feasibility, economy, and environmental safety, necessitating the development of more efficient, green, and easily implemented alternative technologies. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a method for preparing and applying coal-based biochar. The coal-based biochar of this invention can construct a dense and stable passivation film on the surface of pyrite, effectively blocking the contact between moisture, dissolved oxygen, and various cations and the mineral surface, thereby cutting off the oxidation reaction pathway at its source.

[0006] To achieve the above objectives, the technical solution designed by the present invention is as follows: This invention provides a method for preparing coal-based biochar, comprising the following steps: (1) Wash the anthracite until the pH is neutral, and then dry and sieve it in sequence; (2) Place the sieved anthracite in the activation solution and let it stand; (3) After standing, the anthracite is dried; (4) Place the anthracite from step (3) in a heating furnace for the first heating; (5) After the first heating is completed, a second heating is performed; (6) The anthracite after the second heating is washed until the pH is 6.5~7.5, and then dried, crushed and sieved in sequence to obtain coal-based biochar.

[0007] Furthermore, in step (1), the drying temperature is 100~105℃, the drying time is 12~13 h, and the sieve mesh size is <40 mesh; In step (2), the settling temperature is 25~30℃, and the settling time is 8~8.5h. The activation solution is any one of water, potassium hydroxide solution, and hydroxide solution. The mass ratio of potassium hydroxide in the anthracite and potassium hydroxide solution is 1:0.495~0.505. The hydroxide solution includes potassium hydroxide and sodium hydroxide, and the mass ratio of anthracite to potassium hydroxide and sodium hydroxide in the hydroxide solution is 1:0.495~0.505:0.495~0.505.

[0008] Furthermore, the activation solution is a hydroxide solution, and the mass ratio of potassium hydroxide to sodium hydroxide in the anthracite and hydroxide solution is 1:0.5:0.5.

[0009] Furthermore, in step (3), the drying temperature is 120~125℃ and the drying time is 12~12.5 h; In step (4), the heating rate of the first heating is 9~11℃ / min, the temperature is raised to 400~450℃, the temperature of the first heating is 400~450℃, and the time of the first heating is 1~1.5 h; In step (5), the heating rate of the second heating is 10~12℃ / min, the temperature is raised to 700~900℃, the temperature of the second heating is 700~900℃, and the time of the second heating is 2~2.5 h; In step (6), the drying temperature is 100~105℃, the drying time is 6~6.5 h, and the sieve mesh size is <100 mesh.

[0010] Furthermore, the heating rate for the second heating is 10℃ / min, the temperature is raised to 900℃, the temperature of the second heating is 900℃, and the heating time for the second heating is 2 hours.

[0011] The present invention also provides an application of the coal-based biochar prepared by the above preparation method in the preparation of pyrite sulfur-suppressing and acid-reducing reagents.

[0012] The present invention also provides a pyrite sulfur-suppressing and acid-reducing reagent, the reagent comprising coal-based biochar and ferrooxidizobacillus bacterial solution prepared by the preparation method described above; The bacterial count of the *Thiobacillus ferrooxidans* culture was 6.5 × 10⁻⁶. 7 ~7×10 7 pcs / ml; The mass-to-volume ratio of the coal-based biochar and the Thiobacillus ferrooxidans bacterial solution is 1:5~6 g / ml.

[0013] Furthermore, the bacterial count of the *Thiobacillus ferrooxidans* culture is 6.74 × 10⁻⁶. 7 pcs / ml; The mass-to-volume ratio of the coal-based biochar and the Thiobacillus ferrooxidans bacterial solution is 1:5 g / ml.

[0014] The present invention also provides a method for sulfur suppression and acid reduction of pyrite using the aforementioned reagent, comprising the following steps: 1) The pyrite is crushed and screened sequentially; 2) Add the crushed pyrite to the culture medium, along with the reagents and ferrous sulfate, and then dissolve and culture it.

[0015] Furthermore, in step 1), the mesh size of the sieve is <100 mesh; In step 2), the culture medium consists of 3 g / L (NH4)2SO4, 0.5 g / L MgSO4•7H2O, 0.15 g / L Na2SO4•10H2O, 0.1 g / L KCl, 0.05 g / L KH2PO4, and 0.014 g / L Ca(NO3)2•4H2O. The mass-to-volume ratio of pyrite, ferrous sulfate, culture medium, and the reagent is 1:0.45~0.55:20~30:2~3 g / ml.

[0016] Furthermore, the mass-to-volume ratio of the pyrite, ferrous sulfate, culture medium, and the reagent is 1:0.49:20:2 g / ml.

[0017] The beneficial effects of this invention are: 1. Experimental data from this invention show that the coal-based biochar material of this invention can significantly inhibit the oxidative dissolution process of pyrite. After treatment with coal-based biochar, the concentration of ferrous ions in the mixed solution decreased significantly by 50.6%, and the total iron ion concentration (including the sum of the concentrations of ferrous and ferric ions) also decreased by 49.8%, reflecting that its oxidative dissolution process was effectively inhibited. The core advantage of this invention is that coal-based biochar can construct a dense and stable passivation film on the surface of pyrite, effectively blocking the contact between moisture, dissolved oxygen, and various cations and the mineral surface, thereby cutting off the oxidation reaction pathway at its source.

[0018] 2. Compared with traditional passivation methods such as lime neutralization and physical covering, coal-based biochar not only avoids secondary pollution or frequent maintenance, but also possesses significant competitive advantages due to its wide availability, low cost, and good environmental compatibility. Furthermore, the resulting passivation film exhibits excellent chemical stability and long-term durability, significantly slowing down the weathering process of pyrite and achieving long-term control goals. Therefore, coal-based biochar passivation technology is not only efficient and economical, but also meets the requirements of green environmental remediation, possessing significant promotional value and application potential in the fields of mine pollution control and acid wastewater prevention.

[0019] 3. Coal-based biochar can significantly enhance the activity of *Thiobacillus ferrooxidans* on Fe in solution and on the surface of pyrite. 2+ The catalytic oxidation process rapidly converts it into Fe. 3+ And simultaneously promote S 2- To SO4 2- Oxidation. Furthermore, coal-based biochar can induce *Thiobacillus ferrooxidans* to secrete more extracellular polymers, which can act as Fe... 3+ With SO4 2- The effective adsorption sites on the pyrite surface promote the crystallization and nucleation process of potassium pyrite. These effects collectively accelerate the formation of the potassium pyrite passivation layer on the pyrite surface, thereby effectively inhibiting further oxidation and dissolution of pyrite. Attached Figure Description

[0020] Figure 1 SEM image of pyrite after treatment with sulfur-suppressing and acid-reducing reagents; Figure 2Figure showing the total iron ion concentration of the solution after pyrite was treated with a sulfur-suppressing and acid-reducing reagent for pyrite. Figure 3 The result of ferrous ion concentration in the solution after pyrite was treated with a sulfur-suppressing and acid-reducing reagent for pyrite; Figure 4 The figure shows the results of the determination of the effectiveness of the potassium ferruginous layer in inhibiting the oxidation of pyrite. Figure 5 A comparison chart showing the effects of pyrite sulfur-suppressing and acid-reducing reagents CAC9002 and CC9002. Detailed Implementation

[0021] The present invention will now be described in further detail with reference to specific embodiments, so that those skilled in the art can understand it.

[0022] Example 1 Preparation of coal-based biochar CAC9001 1. Wash the anthracite with water until the pH is neutral (pH is 7), dry it at 105℃ for 12 hours, and then sieve it to obtain the material under a sieve of <40 mesh for sample preparation; 2. Place 5g of sieved anthracite in 25ml of activation solution and let it stand at 25℃ for 8 hours; the activation solution in this example is ultrapure water; 3. Place the anthracite from step 2 in an electric drying oven at 120℃ and dry for 12 hours; 4. Spread a thin layer (1~2 mm) of dried anthracite on the bottom of the crucible, place it in a tube-type electronic heating furnace, and carry out the first heating under N2 atmosphere protection at a heating rate of 10℃ / min. After heating to 400℃, carry out the first heating for 1 hour. 5. After the first heating is completed, the second heating is carried out. First, the temperature is increased at a rate of 10℃ / min until it reaches 900℃, and then the second heating is carried out for 2 hours. 6. Wash the sample after the second heating with 5% HCl solution and distilled water to make the pH value 6.5~7.5. Then dry it in an electric heating drying oven at 100℃ for 6 hours. Finally, the carbon product is recorded as coal-based activated carbon, crushed, and screened to obtain the sample under a sieve of <100 mesh to obtain coal-based biochar CAC9001.

[0023] Example 2 Preparation of coal-based biochar CAC7001 The preparation method of coal-based biochar CAC7001 in this embodiment is the same as that in Example 1, except that in step 5, the temperature is raised to 700°C for heating.

[0024] Example 3 Preparation of coal-based biochar CAC9002 The preparation method of coal-based biochar CAC9002 in this embodiment is the same as that in Example 1, except that in step 2, the activation solution is a potassium hydroxide solution, and 25 ml of the activation solution contains 2.5 g of potassium hydroxide.

[0025] Example 4 Preparation of coal-based biochar CAC7002 The preparation method of coal-based biochar CAC7002 in this embodiment is the same as that in embodiment 3, except that in step 5, the temperature is raised to 700°C for heating.

[0026] Example 5 Preparation of coal-based biochar CAC9003 The preparation method of coal-based biochar CAC9003 in this embodiment is the same as that in Example 1, except that in step 2, the activation solution is a hydroxide solution, and 25 ml of the activation solution contains 2.5 g of KOH and 2.5 g of NaOH.

[0027] Example 6 Preparation of coal-based biochar CAC7003 The preparation method of coal-based biochar CAC7003 in this embodiment is the same as that in Example 5, except that in step 5, the temperature is raised to 700°C for heating.

[0028] Example 7 Pyrite Sulfur Inhibiting and Acid Reducing Agent The reagents in this embodiment include coal-based biochar and Thiobacillus ferrooxidans bacterial solution; The bacterial count of *Thiobacillus ferrooxidans* culture was 6.5 × 10⁻⁶. 7 ~7×10 7 The mass-to-volume ratio of coal-based biochar and *Thiobacillus ferrooxidans* bacterial solution was 1:5~6 g / ml; Preparation of *Thiobacillus ferrooxidans* bacterial culture: 1. Preparation of culture medium: (1) Weigh 1.5 g (NH4)2SO4, 0.25 g MgSO4•7H2O, 0.075 g Na2SO4•10H2O, 0.05 g KCl, 0.025 g KH2PO4, and 0.007 g Ca(NO3)2•4H2O and add them to a beaker. Add water to dissolve them (if they do not dissolve, add 3M sulfuric acid to adjust the pH).

[0029] (2) Adjust the pH of the above solution to 2.2~2.5 using 3M sulfuric acid; (3) After adjusting the pH, add water to make up to 500 mL, seal the bottle with sealing film, and put it into a high-temperature sterilizer for 20 minutes to obtain the culture medium.

[0030] 2. Place the culture medium and 24.6g FeSO4•7H2O into a sterile room and turn on the ultraviolet disinfection.

[0031] 3. After the culture medium has cooled in a sterile room, add 50 ml of *Thiobacillus ferrooxidans* ATCC 23270 and 24.6 g of FeSO4•7H2O to the culture medium. Seal the bottle with sealing film and incubate at 30℃ and 180 rpm for 96 h on a shaker to obtain a concentration of 6.5 × 10⁻⁶. 7 ~7×10 7 A bacterial culture of *Thiobacillus ferrooxidans* per ml.

[0032] The coal-based biochar is CAC9001, CAC7001, CAC9002, CAC7002, CAC9003 or CAC7003, and the corresponding pyrite sulfur-suppressing and acid-reducing reagents are CAC9001, CAC7001, CAC9002, CAC7002, CAC9003 or CAC7003.

[0033] Comparative Example 1 Preparation of coal-based biochar CC9002 1. Wash the anthracite with water until the pH is neutral (pH is 7), dry it at 105℃ for 12 hours, and then sieve it to obtain the material under a sieve of <40 mesh for sample preparation; 2. Place 5g of sieved anthracite in 25ml of activation solution and let it stand at 25℃ for 8 hours; in this example, the activation solution is a potassium hydroxide solution, and 25ml of activation solution contains 2.5g of potassium hydroxide. 3. Place the anthracite from step 2 in an electric drying oven at 120℃ and dry for 12 hours; 4. Spread a thin layer (1~2 mm) of dried anthracite on the bottom of the crucible, place it in a tube-type electric heating furnace, and heat it under N2 atmosphere protection at a heating rate of 10℃ / min until it reaches 900℃ and heat it for 2 hours. 6. Wash the heated sample with 5% HCl solution and distilled water to adjust the pH to 6.5-7.5. Then dry it in an electric heating drying oven at 100℃ for 6 hours. Finally, record the carbon product as coal-based activated carbon, crush it, and sieve it to obtain the sample that passes through a sieve with a mesh size <100 to obtain coal-based biochar CC9002.

[0034] Comparative Example 2 Pyrite Sulfur Inhibitor and Acid Reduction Reagent CC9002 The pyrite sulfur-suppressing and acid-reducing reagent CC9002 in this comparative example is the same as that in Example 7, except that the coal-based biochar in this comparative example is the coal-based biochar CC9002 of Comparative Example 1.

[0035] Example 8 Sulfurization and acid reduction of pyrite using the reagents of Example 7 1. Crush the pyrite and screen it to obtain the material under a sieve with a mesh size <100; 2. Add 5g of pyrite obtained in step 2 to 100ml of culture medium, seal the bottle with sealing film, and sterilize in a high-temperature sterilizer for 20 minutes. 3. Add 10 ml of the pyrite sulfur-suppressing and acid-reducing reagent from Example 7 and 2.46 g of FeSO4•7H2O to the pyrite solution from step 2. Seal the bottle with sealing film and place it in a shaker at 30°C and 180 rpm for dissolution and incubation. Meanwhile, a control group was prepared by performing the same steps without adding the pyrite sulfur-suppressing and acid-reducing reagent.

[0036] 4. After dissolving and culturing in step 3, measure the pH and redox potential of the mixture at 0h, 48h, 96h, 192h, 288h, 384h, and 480h respectively. Extract the mixture and centrifuge it at 10,000 rpm for 15 min to separate the solid and liquid. Collect the supernatant and solid.

[0037] 5. After freeze-drying the solid obtained in step 4, SEM was performed. The results are as follows: Figure 1 As shown, the surface of pyrite is completely coated with potassium ferric sulfate / potassium ferric sulfate ammonium.

[0038] 6. Divide the supernatant obtained in step 4 into two parts. Dilute one part of the supernatant 7280 times and measure the concentration of ferric ions using an atomic absorption spectrometer.

[0039] 7. Prepare a 1.18 g / ml hydrochloric acid solution, a buffer solution (40 g ammonium acetate diluted with 50 ml glacial acetic acid and water to 100 ml), and a 0.5% (m / V) o-phenanthroline aqueous solution; 8. Dilute another portion of the supernatant from step 6 by 4500 times, then take 50 ml and add 1 ml of hydrochloric acid solution, 5 ml of buffer solution, and 2 ml of o-phenanthroline aqueous solution from step 7. Let it develop color for 5 min. 9. Measure the absorbance of the mixture obtained in step 8 at 510 nm using a spectrophotometer with water as a reference, perform blank correction, and measure the concentration of ferrous ions. The results are as follows Figure 2As shown, the total iron ion concentration (including the sum of ferrous and ferric ions) in the experimental groups with added pyrite sulfur-suppressing and acid-reducing reagents all exhibited a rapid decreasing trend, with the effects of pyrite sulfur-suppressing and acid-reducing reagents CAC9003 and CAC7003 being particularly significant. Under the presence of these two pyrite sulfur-suppressing and acid-reducing reagents, the total iron ion concentration decreased sharply in the initial stage of the experiment and reached equilibrium around day 4. In contrast, the iron ion concentration decreased significantly more slowly in the control group without added pyrite sulfur-suppressing and acid-reducing reagents, and the equilibrium time was significantly prolonged. The results indicate that the addition of coal-based biochar causes ferric ions and sulfate ions in the solution to form potassium ferric alum / potassium ferric alum ammonium, consuming the iron ions in the solution and preventing further oxidation of pyrite.

[0040] The results are as follows Figure 3 As shown, in the experimental system with added pyrite sulfur-suppressing and acid-reducing reagents, the concentration of ferrous ions exhibited a rapid decreasing trend. Compared with the control group, all pyrite sulfur-suppressing and acid-reducing reagent treatments significantly accelerated the removal of ferrous ions, with pyrite sulfur-suppressing and acid-reducing reagents CAC9003 and CAC7003 showing the most prominent effects. Under the presence of these two reagents, the concentration of ferrous ions decreased rapidly in the early stage of the experiment and basically reached the reaction endpoint on the 4th day, indicating that the oxidation process was nearing completion. Kinetic analysis showed that coal-based biochar CAC9003 and CAC7003 not only provided abundant reaction interfaces but also may have directly participated in the electron transfer process through surface functional groups, thereby greatly promoting the oxidation reaction rate of ferrous ions. This accelerating effect enabled ferrous ions in the solution to be oxidized in the shortest possible time, transforming into the more stable ferric ferric form. The results showed that the addition of coal-based biochar to the pyrite sulfur-suppressing and acid-reducing reagent rapidly oxidized ferrous ions in the solution to ferric ions, and formed potassium ferric alum / potassium ferric alum ammonium with ferric ions, which consumed the ferric ions in the solution and prevented the pyrite from continuing to oxidize.

[0041] The coal-based biochar CAC9003 in the pyrite sulfur-suppressing and acid-reducing reagent of the present invention is the optimal coal-based biochar: 25 ml of activation solution contains 2.5 g of KOH and 2.5 g of NaOH, and the second heating temperature is 900 °C.

[0042] The sulfur inhibition and acid reduction of this invention refers to the rapid oxidation of ferrous ions in the solution to ferric ions, and the formation of potassium ferric alum / potassium ferric alum ammonium by ferric ions and sulfate ions, which consumes iron ions in the solution and prevents pyrite from continuing to oxidize.

[0043] Example 9 Chemical antioxidant experiment To further confirm the effectiveness of the potassium ferruginous layer in inhibiting pyrite oxidation, a chemical test was conducted in a 3% hydrogen peroxide solution in this embodiment.

[0044] Prepare a 3% hydrogen peroxide solution. Passivated pyrite CAC9003 (the solid product of pyrite sulfur suppression and acid reduction using CAC9003, a pyrite sulfur suppression and acid reduction reagent containing coal-based biochar, in Example 8), pyrite CAC9002 (the solid product of pyrite sulfur suppression and acid reduction using CAC9002, a pyrite sulfur suppression and acid reduction reagent containing coal-based biochar, in Example 8), and pyrite without the treatment in Example 8 were placed into 250ml Erlenmeyer flasks, and 100ml of the 3% hydrogen peroxide solution was added. The mixture was stirred at 25-30℃, and samples were taken at 0h, 0.5h, 1h, 2h, and 3h.

[0045] The results are as follows Figure 4 As shown, after 0.5 h of oxidation, the oxidation of both pyrite CAC9003 and pyrite CAC9002 was significantly inhibited compared to pyrite treated in Example 8 (CK). After 3 hours, the total iron ion concentration in the solution decreased by more than 70% compared to CK.

[0046] Example 10 The effects of pyrite sulfur-suppressing and acid-reducing reagent CAC9002 and pyrite sulfur-suppressing and acid-reducing reagent CC9002 in Comparative Example 2 were compared. The steps were the same as in Example 8. Meanwhile, the same steps were performed without the addition of pyrite sulfur-suppressing and acid-reducing reagent as a control group.

[0047] The results are as follows Figure 5 As shown, after preheating at 400℃ for 1 hour (the first heating in Example 3), coal-based biochar CAC9002 significantly promoted the generation of ferrous ions (Fe2+) during the passivation of pyrite. 2+ ) and ferric ions (Fe 3+ The decrease in Fe content was significantly accelerated, both in terms of the rate and magnitude of the decrease. This indicates that pre-pyrolysis treatment can effectively accelerate the reduction of Fe content. 2+ To Fe 3+ The oxidation process provides a more abundant iron source for the formation of the passivation layer on the pyrite surface. Simultaneously, the 400℃ pre-pyrolysis treatment significantly promotes the rapid formation and stable development of the passivation layer. These phenomena can be attributed to the fact that the pre-pyrolysis treatment significantly improves the pyrolysis completion rate of coal-based biochar, thereby enhancing the formation of key active sites on its surface and increasing the effective contact area with the reactants.

[0048] All other parts not described in detail are existing technologies. Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing coal-based biochar, characterized in that: Includes the following steps: (1) Wash the anthracite until the pH is neutral, and then dry and sieve it in sequence; (2) Place the sieved anthracite in the activation solution and let it stand; (3) After standing, the anthracite is dried; (4) Place the anthracite from step (3) in a heating furnace for the first heating; (5) After the first heating is completed, a second heating is performed; (6) The anthracite after the second heating is washed until the pH is 6.5~7.5, and then dried, crushed and sieved in sequence to obtain coal-based biochar.

2. The preparation method according to claim 1, characterized in that: In step (1), the mesh size of the sieve is <40 mesh; In step (2), the settling temperature is 25~30℃, and the settling time is 8~8.5h. The activation solution is any one of water, potassium hydroxide solution, and hydroxide solution. The mass ratio of potassium hydroxide in the anthracite and potassium hydroxide solution is 1:0.495~0.

505. The hydroxide solution includes potassium hydroxide and sodium hydroxide, and the mass ratio of anthracite to potassium hydroxide and sodium hydroxide in the hydroxide solution is 1:0.495~0.505:0.495~0.

505.

3. The preparation method according to claim 2, characterized in that: The activation solution is a hydroxide solution, and the mass ratio of potassium hydroxide to sodium hydroxide in the anthracite and hydroxide solution is 1:0.5:0.

5.

4. The preparation method according to claim 1, characterized in that: In step (3), the drying temperature is 120~125℃ and the drying time is 12~12.5 h; In step (4), the heating rate of the first heating is 9~11℃ / min, the temperature is raised to 400~450℃, the temperature of the first heating is 400~450℃, and the time of the first heating is 1~1.5 h; In step (5), the heating rate of the second heating is 10~12℃ / min, the temperature is raised to 700~900℃, the temperature of the second heating is 700~900℃, and the time of the second heating is 2~2.5 h; In step (6), the mesh size of the sieve is <100 mesh.

5. The preparation method according to claim 4, characterized in that: The second heating is to 900°C, the second heating temperature is 900°C, and the second heating time is 2 hours.

6. The application of coal-based biochar prepared by the method of claim 1 in the preparation of pyrite sulfur-suppressing and acid-reducing reagent.

7. A pyrite-based sulfur-suppressing and acid-reducing reagent, characterized in that: The reagents include coal-based biochar and Thiobacillus ferrooxidans bacterial solution prepared by the preparation method of claim 1; The bacterial count of the *Thiobacillus ferrooxidans* culture was 6.5 × 10⁻⁶. 7 ~7×10 7 pcs / ml; The mass-to-volume ratio of the coal-based biochar and the Thiobacillus ferrooxidans bacterial solution is 1:5~6 g / ml.

8. The reagent according to claim 7, characterized in that: The bacterial count of the *Thiobacillus ferrooxidans* culture was 6.74 × 10⁻⁶. 7 pcs / ml; The mass-to-volume ratio of the coal-based biochar and the Thiobacillus ferrooxidans bacterial solution is 1:5 g / ml.

9. A method for inhibiting sulfurization and reducing acidity in pyrite using the reagent described in claim 7, characterized in that: Includes the following steps: 1) The pyrite is crushed and screened sequentially; 2) Add the crushed pyrite to the culture medium, and add the reagent and ferrous sulfate as described in claim 7, and carry out dissolution culture.

10. The method according to claim 9, characterized in that: In step 1), the mesh size of the sieve is <100 mesh; In step 2), the culture medium consists of 3 g / L (NH4)2SO4, 0.5 g / L MgSO4•7H2O, 0.15 g / L Na2SO4•10H2O, 0.1 g / L KCl, 0.05 g / L KH2PO4, and 0.014 g / L Ca(NO3)2•4H2O. The mass-to-volume ratio of pyrite, ferrous sulfate, culture medium, and the reagent is 1:0.45~0.55:20~30:2~3g / ml.

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