Biochar, preparation method and application thereof, and treatment method of heavy metals in water body

Abstract

The invention belongs to the technical field of sewage treatment, and provides biochar, a preparation method and application thereof, and a treatment method of heavy metals in a water body. The carbide slag and the pig manure are used as raw materials to prepare the biochar, the alkaline characteristic of the carbide slag enhances the buffering capacity of a water body, and alkaline mineral components (carbonate and calcium oxide) and oxygen-containing functional groups (such as hydroxyl groups, phenolic hydroxyl groups, carboxyl groups, ketone groups, ether bonds and alcohol functional groups) can be introduced into the biochar through compounding of the carbide slag and the pig manure; the alkaline mineral component and the oxygen-containing functional group promote the complexing adsorption and precipitation reaction of the biochar on heavy metals in the water body, so that the adsorption performance of the biochar on the heavy metals is improved. According to the invention, the raw material cost and resource competition are reduced, and the resource utilization of the waste carbide slag and pig manure can be realized; besides, the prepared biochar has excellent adsorption performance, a sustainable solution is provided for treatment of heavy metals in water, and environmental protection and improvement of economic benefits are promoted.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and in particular to a biochar, its preparation method and application, and a method for treating heavy metals in water. Background Technology

[0002] With rapid industrialization and urbanization, heavy metal pollution has become one of the major challenges facing the global water environment. Heavy metals, such as cadmium (Cd) and nickel (Ni), are characterized by high toxicity, poor degradation, and easy accumulation in organisms, posing a serious threat to ecosystems and human health. Therefore, developing efficient, economical, and environmentally friendly water heavy metal treatment technologies has become a critical issue that urgently needs to be addressed.

[0003] Biochar, with its abundant specific surface area, porous structure, and oxygen-containing functional groups, shows great potential for application in the adsorption of heavy metals. However, the raw materials for biochar production are currently concentrated in traditional biomass resources such as wood and crop straw, which presents problems such as high cost or resource competition. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide biochar, its preparation method and application, and a method for treating heavy metals in water. The preparation method provided by this invention uses carbide slag and pig manure as raw materials to prepare biochar, which not only reduces raw material costs and resource competition issues, but also enables the resource utilization of waste carbide slag and pig manure. Furthermore, the biochar prepared by this invention has excellent adsorption properties, providing a sustainable solution for the treatment of heavy metals in water.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing biochar, comprising the following steps: The carbide slag and pig manure were mixed and pyrolyzed to obtain the biochar.

[0006] Preferably, the mass of the carbide slag is 10-75% of the total mass of carbide slag and pig manure.

[0007] Preferably, the pyrolysis temperature is 300~700℃ and the time is 0.5~1.5h.

[0008] Preferably, the heating rate to the pyrolysis temperature is 5~15℃ / min.

[0009] Preferably, the pyrolysis is carried out under a protective atmosphere, which includes one or more of nitrogen and / or argon.

[0010] The present invention also provides biochar prepared by the preparation method described in the above technical solution.

[0011] This invention also provides the application of the biochar described in the above technical solution in the treatment of heavy metals in water bodies.

[0012] Preferably, the heavy metal includes Cd(II) or Ni(II).

[0013] This invention also provides a method for treating heavy metals in water, comprising the following steps: The biochar described in the above technical solution is added to water bodies containing heavy metals for treatment.

[0014] Preferably, the dosage of biochar is 1~5 mg / mL; The concentration of heavy metals in the water body is 100~150 mg / L.

[0015] This invention provides a method for preparing biochar.

[0016] The preparation method provided by this invention uses carbide slag and pig manure as raw materials to prepare biochar. The alkaline properties of carbide slag enhance the buffering capacity of water bodies, and the combination of carbide slag and pig manure can introduce alkaline mineral components (such as carbonates and calcium oxide) and oxygen-containing functional groups (such as hydroxyl, phenolic hydroxyl, carboxyl, ketone, ether, and alcohol functional groups) into the biochar. The alkaline mineral components and oxygen-containing functional groups jointly promote the complexation adsorption and precipitation reaction of heavy metals by the biochar, thereby improving the adsorption performance of the biochar for heavy metals. The preparation method of this invention not only reduces raw material costs and resource competition issues, but also realizes the resource utilization of waste carbide slag and pig manure. In addition, the biochar prepared by this invention has excellent adsorption performance, providing a sustainable solution for the treatment of heavy metals in water bodies, promoting environmental protection and economic benefits. Attached Figure Description

[0017] Figure 1 Scanning electron microscope images of different biochars in Test Example 2; Figure 2 Fourier transform infrared spectra of different biochars in Test Example 4. Detailed Implementation

[0018] This invention provides a method for preparing biochar, comprising the following steps: The carbide slag and pig manure were mixed and pyrolyzed to obtain the biochar.

[0019] Unless otherwise specified, the raw materials used in this invention are preferably commercially available products.

[0020] In this invention, the carbide slag preferably comprises the following components by weight percentage: CaO 254-72%, and other oxides 23-31%; the other oxides preferably include SiO 2, Al 2O 3, Fe 2O 3, and MgO. In this invention, the carbide slag is preferably naturally air-dried. In this invention, before mixing the carbide slag with pig manure, it is preferable to further include: grinding and sieving the carbide slag sequentially, wherein the sieve mesh size is preferably 100 mesh. In this invention, since the main components of the carbide slag are all alkaline substances, the carbide slag has alkaline properties, which enhance the buffering capacity of water bodies; and the combination of carbide slag and pig manure introduces alkaline mineral components (such as CaCO 3, CaO, etc.) into the biochar, increasing the surface activity and the number of adsorption sites of the biochar, which helps in the effective capture of heavy metals.

[0021] In this invention, the pig manure is preferably dehydrated pig manure. In this invention, before mixing the pig manure with carbide slag, the process preferably further includes: grinding and sieving the pig manure sequentially, wherein the sieve mesh size is preferably 100 mesh. In this invention, using pig manure as a biomass raw material, the organic matter in the pig manure, upon pyrolysis, forms oxygen-containing functional groups, thereby providing more binding sites for biochar, which is beneficial for the capture of heavy metals.

[0022] In this invention, the mass of the carbide slag is preferably 10-75% of the total mass of carbide slag and pig manure, more preferably 25-75%, and specifically preferably 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70% or 75%.

[0023] In this invention, the pyrolysis temperature is preferably 300~700℃, specifically preferably 300℃, 400℃, 500℃, 600℃, or 700℃; the time is preferably 0.5~1.5h, more preferably 1h. In this invention, the heating rate to the pyrolysis temperature is preferably 5~15℃ / min, more preferably 10℃ / min. In this invention, the pyrolysis is preferably carried out under a protective atmosphere, which preferably includes one or more of nitrogen and / or argon, more preferably nitrogen. In this invention, the pyrolysis is preferably carried out in an electrically heated vacuum tube furnace.

[0024] In this invention, the preferred pyrolysis process is as follows: a mixture of carbide slag and pig manure is placed in a quartz boat, and the quartz boat containing the mixture is placed in the central quartz tube reactor of an electrically heated vacuum tube furnace; then, a protective atmosphere is purged, and after purging, the temperature is raised to the pyrolysis temperature and held. In this invention, during the protective atmosphere purging process, the gas flow rate of the protective atmosphere is preferably ≥100 mL / min, more preferably 100 mL / min; the time is preferably 10~20 min, more preferably 15 min.

[0025] After pyrolysis, the present invention preferably includes: natural cooling to room temperature.

[0026] The preparation method provided by this invention can not only realize the resource utilization of waste carbide slag and pig manure, but also effectively reduce the cost of sewage treatment, providing technical support for the high-value utilization of waste and the treatment of environmental pollution, and has the technical advantages of being green and environmentally friendly.

[0027] The present invention also provides biochar prepared by the preparation method described in the above technical solution.

[0028] The biochar prepared by the method provided by this invention has excellent heavy metal adsorption performance and can efficiently remove heavy metals from water.

[0029] This invention also provides the application of the biochar described in the above technical solution in the treatment of heavy metals in water bodies.

[0030] In this invention, the heavy metal preferably includes Cd(II) or Ni(II).

[0031] This invention also provides a method for treating heavy metals in water, comprising the following steps: The biochar described in the above technical solution is added to water bodies containing heavy metals for treatment.

[0032] In this invention, the dosage of biochar is preferably 1 to 5 mg / mL, and more preferably 1 mg / mL, 2 mg / mL, 2.5 mg / mL, 3 mg / mL, 4 mg / mL or 5 mg / mL.

[0033] In this invention, the concentration of heavy metals in the water body is preferably 100-150 mg / L. In this invention, the pH value of the water body is preferably 5.5-6.5.

[0034] In this invention, the processing temperature is preferably room temperature, i.e., neither additional heating nor additional cooling is required. In this invention, the processing is preferably carried out under oscillation conditions, and the oscillation speed is preferably 100~300 r·min. -1 Further preferred is 200 r·min -1.

[0035] The following examples illustrate in detail the biochar, its preparation method, its application, and the treatment method for heavy metals in water provided by this invention. However, these examples should not be construed as limiting the scope of protection of this invention.

[0036] Example 1 Naturally air-dried carbide slag and dehydrated pig manure from a livestock farm were ground and sieved to obtain carbide slag and pig manure powder, which was then ground through a 100-mesh sieve. Biochar was prepared using an oxygen-limited temperature-controlled carbonization method, with carbide slag accounting for 10%, 25%, 50%, and 75% of the total mass of carbide slag and pig manure, respectively. Simultaneously, pig manure and carbide slag were pyrolyzed separately as control groups.

[0037] The specific pyrolysis process is as follows: Calcium carbide slag and pig manure are uniformly mixed in different proportions. A certain amount of the mixture is placed in a quartz boat and then introduced into the central quartz tube reactor of an electrically heated vacuum tube furnace. Before pyrolysis, the reactor is purged with high-purity N2 gas at a rate of 100 mL / min for 15 minutes to ensure an oxygen-free environment. The temperature is then increased to the target temperature (300℃, 500℃, 700℃) at a rate of 10℃ / min, and held at the highest temperature for 1 hour. Afterward, it is naturally cooled to room temperature to obtain calcium carbide slag-modified pig manure biochar. This biochar is then removed and stored in a desiccator for later use.

[0038] Biochar obtained from pig manure alone at different temperatures was designated as MB300, MB500, and MB700, respectively.

[0039] Biochar obtained by mixing carbide slag and pig manure at different temperatures was designated as CSB300-10%, CSB500-10%, CSB700-10%, CSB300-25%, CSB500-25%, CSB700-25%, CSB300-50%, CSB500-50%, CSB700-50%, CSB300-75%, CSB500-75%, and CSB700-75%, respectively.

[0040] Biochar obtained from calcium carbide slag at different temperatures is designated as CS300, CS500, and CS700, respectively.

[0041] All biochar was ground and passed through a 100-mesh sieve before being used for physicochemical characterization and analysis, as well as for experiments on adsorbing heavy metal ions in water.

[0042] Test Example 1 Table 1. Basic properties of different biochars

[0043] As shown in Table 1, the biochar obtained by mixing carbide slag and pig manure is strongly alkaline, and the pH value of the biochar increases with the increase of pyrolysis temperature and the proportion of carbide slag. The yield of biochar decreases with the increase of pyrolysis temperature and the proportion of carbide slag added.

[0044] Test Example 2 Biochar samples were passed through a 100-mesh sieve to collect uniformly sized powder samples. A suitable amount of sample was taken and adhered to the surface of a conductive copper stage using double-sided conductive adhesive, ensuring uniform sample distribution. The sample surface was then sputter-coated with gold for 60 seconds to improve conductivity and reduce the influence of electron beam focusing. A field emission scanning electron microscope (FET) was used; the accelerating voltage was set to 5 kV; and the magnification was selected to 30 nm to observe the macroscopic structure and fine pore structure of the biochar samples. The scanning electron microscope results for different biochar types are shown below. Figure 1 As shown.

[0045] Figure 1 Scanning electron microscope (SEM) images of different biochars are shown, where (a) is an SEM image of MB700, (b) is an SEM image of CS700, (c) is an SEM image of CSB700-10%, (d) is an SEM image of CSB700-25%, (e) is an SEM image of CSB700-50%, and (f) is an SEM image of CSB700-75%. Figure 1 It can be observed that the biochar obtained from the pyrolysis of pig manure alone (MB700) has a smooth surface, while the biochar obtained from the pyrolysis of carbide slag alone (CS700) has a rough and irregular surface. Compared with MB and CS, the biochar from CSB-10% to CSB-75% exhibits greater porosity and roughness, indicating that the co-pyrolysis process generates a large number of pores in the raw materials. As the proportion of carbide slag increases, the specific surface area of ​​the co-pyrolyzed biochar gradually increases, leading to a transformation from a less porous structure (CSB700-10%) to a more porous structure (CSB700-25%, CSB700-50%), and finally to a more porous structure (CSB700-75%).

[0046] Test Example 3 A suitable amount of biochar sample was placed in a vacuum drying oven at 60℃ and dried for 12 hours to ensure no moisture residue remained. The dried sample was then passed through a 200-mesh sieve, and the powdered biochar was collected for characterization. The nitrogen adsorption-desorption method was used, and the sample was characterized using a fully automated specific surface area and porosity analyzer (TriStarII 3020). Vacuum degassing was performed at 200℃, and liquid nitrogen (77K) was used as the adsorbent during the test. The relative pressure range (P / P0) was measured from 0.05 to 0.35, and the results are shown in Table 2.

[0047] Table 2 Pore properties of different biochars

[0048] Table 2 shows that the specific surface area, pore volume, and pore size of biochar range from 5.01 to 75.95 m². 2 ·g -1 1.13~7.11m 3 ·g -1 The specific surface area and pore volume of biochar with different ratios of carbide slag and pig manure also showed similar trends when the temperature increased from 300℃ to 700℃. At high temperatures, inorganic compounds in the ash are released, and the pores on the surface of the biochar are blocked, resulting in a decrease in the specific surface area and pore volume of the biochar.

[0049] Test Example 4 The biochar sample was dried and ground into powder; a 1:100 mass ratio of the sample was weighed and mixed with KBr, then ground evenly; the mixture was pressed into transparent thin sheets using a tablet press for analysis. Fourier transform infrared spectroscopy was used; the test wavelength range was 4000 cm⁻¹. -1 Up to 400cm -1 The resolution is 4cm. -1 Each sample was scanned repeatedly to ensure the signal-to-noise ratio met the characterization requirements. The results are shown in [the table below]. Figure 2 . Figure 2 Fourier transform infrared spectra of different biochars, from Figure 2 It can be seen that: 3406cm -1 The (-OH stretching vibration) showed a broad peak in this region for all samples, indicating a rich surface hydroxyl content. The peak intensity gradually decreased with increasing pyrolysis temperature (300℃ to 700℃), suggesting that the hydroxyl groups underwent dehydration or decomposition under high-temperature conditions. The peak intensity of biochar doped with carbide slag was slightly higher than that of unmodified biochar, possibly related to the formation of new hydroxyl groups from residual moisture or mineral reactions in the carbide slag. (1654 cm⁻¹) -1 (C=O stretching vibration) This characteristic peak indicates the presence of carboxyl or ketone groups on the material surface; the peak intensity is more pronounced in biochar with a high proportion of calcium carbide slag (CSB 700-75%), indicating that the addition of calcium carbide slag promotes the formation of oxygen-containing functional groups on the surface. 1459cm -1 (-COO) - (Symmetric stretching vibration) All biochar samples showed obvious peak intensities, which increased with the increase of the proportion of carbide slag, indicating that the carbide slag introduced a large amount of carbonate or similar chemical groups. 1048 cm⁻¹ -1 The absorption peaks in this region (COC or C-OH stretching vibrations) indicate the presence of ether bonds and alcohol functional groups in the sample. The peak intensities are even higher in biochar incorporating carbide slag, especially the CSB700 series, suggesting that changes in pore structure enhance the adsorption capacity of these functional groups. (870-600 cm⁻¹)-1 The strong peaks (Ca-O or Si-O vibrations) are related to the inorganic mineral components (such as calcium compounds and silicon oxides) in carbide slag, while unmodified biochar hardly exhibits such characteristic peaks.

[0050] Test Example 5 The BCR extraction method (a three-step extraction method proposed by the European Committee for Standardization) was used to extract and analyze the speciation of heavy metals in biochar, specifically in the following steps: Step 1 (Exchangeable State - F1): Extraction was performed using 0.11M acetic acid (pH 3.0), and the exchangeable state of the metal and the weak acid-bound state were determined. Step 2 (Reducible F2): Extraction was performed using 0.1M ammonium hydroxide and 0.5M hydrochloric acid (pH 2.0), and the portion of the metal bound to iron and manganese oxides was detected; Step 3 (Oxidizable form - F3): Extraction was performed using 8.8M hydrogen peroxide and 1M hydrochloric acid, and the portion of the metal bound to organic matter or sulfides was detected; Step 4 (Residual State - F4): The remaining part is considered to exist in a mineral-bonded form.

[0051] After each extraction step, the samples were separated using a centrifuge (4000 rpm, 15 min), and the supernatant was used to determine the heavy metal content. The analytical tool was inductively coupled plasma mass spectrometry (ICP-MS), and the detection results are shown in Table 3.

[0052] Table 3. BCR speciation analysis of cadmium and nickel in biochar prepared from different carbide slag blends (%)

[0053] As shown in Table 3, the proportion of cadmium in the residual state increases significantly with the increase of the proportion of carbide slag, especially for CSB700-75%, reaching 87.51%. This indicates that the incorporation of carbide slag into biochar can effectively fix cadmium in the residual state, reducing its bioavailability and thus lowering its migration and release risks. In unmodified biochar (such as MB500), the proportion of exchangeable cadmium is relatively high (31.44%), while with the increase of the proportion of carbide slag, especially in CSB700-75%, the content of exchangeable cadmium is almost zero, further demonstrating that the introduction of carbide slag effectively reduces the exchangeability of cadmium and improves its stability. With the increase of the proportion of carbide slag, the distribution of cadmium in the reducible and oxidizable states is relatively balanced, but the reducible state is still dominant. The higher proportion of carbide slag allows cadmium to combine more with mineral groups (such as calcium and silicon) to form more stable compounds.

[0054] Similar to cadmium, nickel exhibits a higher proportion of residual nickel in biochar incorporating carbide slag, especially in CSB700-75% (92.51%). This indicates that the addition of carbide slag significantly improves the stability of nickel, ensuring it exists primarily in a residual form, thereby reducing its potential environmental pollution risks. Unmodified biochar MB500 shows a high proportion of exchangeable nickel (7.29%), while in biochar incorporating carbide slag, particularly in CSB700-75%, exchangeable nickel is almost zero. This suggests that the incorporation of carbide slag effectively reduces the exchangeability of nickel and enhances its fixation ability in biochar. The distribution of nickel in reducible and oxidizable forms is relatively balanced, and with increasing carbide slag proportion, nickel is mainly concentrated in the reducible and residual forms, indicating that nickel is primarily bound to inorganic minerals and has high stability.

[0055] The incorporation of calcium carbide slag with biochar (especially CSB 700-75%) significantly improves the stability of heavy metals such as cadmium and nickel, reducing their bioavailability and migration in water bodies. The residual state is the main stable form of cadmium and nickel, while the proportions of exchangeable and oxidizable states decrease significantly, indicating that the incorporation of calcium carbide slag effectively inhibits the release of heavy metals. The addition of calcium carbide slag enhances the adsorption capacity of biochar for heavy metals, providing an effective material choice for the remediation of heavy metal pollution in water bodies.

[0056] Test Example 6 This study investigated the adsorption performance of Cd(II) by incorporating different proportions of calcium carbide slag prepared by pyrolysis at 700℃ into biochar (CSB700). The specific experimental procedures are as follows: Weigh 0.05 g of biochar sample into a 50 mL centrifuge tube, and add 20 mL of the initial concentration of 150 mg·L⁻¹. -1 The experimental system used a Cd(II) solution, with 0.01 M NaNO3 as the electrolyte and an initial pH of 4. The centrifuge tubes were then placed at a constant temperature of 25°C and centrifuged at 200 rpm. -1 The sample was oscillated at a constant speed for 12 hours. After the reaction was complete, the sample was filtered through a 0.45 μm filter membrane, and the Cd(II) content in the filtrate and blank control was determined by inductively coupled plasma mass spectrometry (ICP-MS). Calculations and analyses were performed based on the removal rate and heavy metal concentration results; some representative data are shown in Table 4.

[0057] Table 4. Removal rate and adsorption capacity of different biochars for Cd(II) in water.

[0058] Table 4 shows that the adsorption performance of the calcium carbide slag mixed with pig manure charcoal is significantly better than that of the unmodified sample (MB700). With the increase of the proportion of calcium carbide slag, both the removal rate and adsorption capacity are improved. Specifically, the removal rates of CSB700-25%, CSB700-50%, and CSB700-75% all reach 99.99%, and the adsorption capacity is close to the maximum value (28.40 mg·g⁻¹). -1 ).

[0059] This indicates that the introduction of alkaline mineral components during pyrolysis significantly enhances the adsorption effect of biochar on Cd(II). The pH of the equilibrium solution after adsorption was 6.43 for unmodified biochar (MB700), while the pH of biochar incorporating carbide slag increased significantly, reaching a maximum of 11.96 (CSB700-50%). This suggests that the alkaline properties of carbide slag enhance the buffering capacity of the water body and promote the binding of Cd(II) with alkaline mineral components such as carbonates, thereby improving adsorption performance. The alkaline mineral components (such as carbonates and calcium oxide) introduced into biochar by combining carbide slag and pig manure may undergo precipitation reactions with Cd(II). Furthermore, the increased functional groups (such as carboxyl and hydroxyl groups) on the surface of biochar provide more binding sites, further enhancing the adsorption effect.

[0060] The incorporation of carbide slag with biochar exhibits superior performance in Cd(II) adsorption in water, especially CSB700-25%, CSB700-50%, and CSB700-75%, achieving a removal rate as high as 99.99% and an adsorption capacity close to the theoretical saturation value. The results indicate that the addition of carbide slag and high-temperature pyrolysis significantly enhance the adsorption capacity of biochar, providing an efficient and feasible solution for the treatment of heavy metal-polluted water bodies.

[0061] Test Example 7 The adsorption performance of Ni(II) by incorporating different proportions of calcium carbide slag prepared by pyrolysis at 700℃ into biochar (CSB700) was investigated. The specific experimental procedures are as follows: Weigh 0.05 g of biochar sample into a 50 mL centrifuge tube, and add 20 mL of the initial concentration of 100 mg·L⁻¹. -1 The experimental system used a Ni(II) solution and a 0.01 M NaNO3 electrolyte solution, with an initial pH of 4. The centrifuge tubes were then placed at a constant temperature of 25°C and centrifuged at 200 r·min. -1 The sample was oscillated at a constant speed for 12 hours. After the reaction was complete, the sample was filtered through a 0.45 μm filter membrane, and the Ni(II) content in the filtrate and blank control was determined by inductively coupled plasma mass spectrometry (ICP-MS). Calculations and analyses were performed based on the removal rate and heavy metal concentration results; some representative data are shown in Table 5.

[0062] Table 5. Removal rate and adsorption capacity of different biochars for Ni(II) in water.

[0063] Table 5 shows that biochar significantly enhances the removal efficiency of Ni(II) under different proportions of carbide slag. Especially when the proportion of carbide slag reaches 25% or more, the removal rate is almost complete (99.99%), and the adsorption capacity is approximately 21 mg·g⁻¹. -1 In comparison, the unmodified sample MB700 showed a removal rate of only 63.85% and an adsorption capacity of 11.99 mg·g⁻¹. -1 The results show that the incorporation of carbide slag significantly improves the adsorption performance. The alkaline mineral components (such as CaCO3 and CaO) introduced by the compounding of carbide slag and pig manure may have increased the surface activity and number of adsorption sites of biochar, which is conducive to the effective capture of Ni(II). The oxygen-containing functional groups (such as carboxyl groups and phenolic hydroxyl groups) on the surface of biochar and the alkaline mineral components jointly promote the complexation adsorption and precipitation reaction of Ni(II). The CSB700-25% sample showed the best overall adsorption performance, with the removal rate and adsorption capacity reaching their maximum values, indicating that a moderate proportion of carbide slag can achieve a significant performance improvement. When the proportion of carbide slag is further increased (such as 50% and 75%), the adsorption capacity decreases slightly, but the high removal rate remains unchanged, possibly due to the adsorption sites tending to saturate.

[0064] Compared to Cd(II), Ni(II) adsorption exhibits a more pronounced dependence on the proportion of carbide slag, especially at low-proportion modification (CSB700-10%), where the removal rate and adsorption capacity are significantly improved, indicating that Ni(II) adsorption is more sensitive to surface modification.

[0065] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing biochar, characterized in that, Includes the following steps: The carbide slag and pig manure were mixed and pyrolyzed to obtain the biochar.

2. The preparation method according to claim 1, characterized in that, The mass of the carbide slag is 10-75% of the total mass of carbide slag and pig manure.

3. The preparation method according to claim 1, characterized in that, The pyrolysis temperature is 300~700℃ and the time is 0.5~1.5h.

4. The preparation method according to claim 1 or 3, characterized in that, The heating rate to the pyrolysis temperature is 5~15℃ / min.

5. The preparation method according to claim 1 or 3, characterized in that, The pyrolysis is carried out under a protective atmosphere, which includes nitrogen and / or argon.

6. Biochar prepared by the method according to any one of claims 1 to 5.

7. The application of the biochar according to claim 6 in the treatment of heavy metals in water bodies.

8. The application according to claim 7, characterized in that, The heavy metals include Cd(II) or Ni(II).

9. A method for treating heavy metals in water, characterized in that, Includes the following steps: The biochar described in claim 6 is added to water containing heavy metals for treatment.

10. The processing method according to claim 9, characterized in that, The dosage of the biochar is 1~5 mg / mL; The concentration of heavy metals in the water body is 100~150 mg / L.

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