Preparation method and application of biochar and method for removing phosphorus-containing substances in water

Abstract

The invention relates to the technical field of water body treatment and biochar, in particular to a preparation method and application of biochar and a method for removing phosphorus-containing substances in water, and the preparation method comprises the steps that biogas residues and eggshells are mixed for a carbonization reaction. The biochar has a porous structure and has stable adsorption performance on phosphorus-containing substances in sewage, meanwhile, the preparation method has the obvious advantages of being simple in technological process, low in cost, environmentally friendly and the like, the biochar is prepared from biogas residues, eggshells and other environment-friendly materials, resource utilization of waste is achieved, negative effects on the environment are reduced, and the biochar is suitable for industrial production. And the method has better economic benefits.

Description

Technical Field

[0001] The present invention relates to the technical field of biochar, and specifically, to a method for preparing biochar and its application. In addition, the present invention also relates to a method for removing phosphorus-containing substances in water. Background Art

[0002] Phosphorus (P) is an important element for the growth and development of animals and plants. However, the presence of excessive phosphorus (P) in water bodies can lead to eutrophication, thereby having a negative impact on the aquatic ecological environment. In order to prevent excessive phosphorus emissions, sewage treatment plants around the world are required to formulate strict phosphorus discharge standards. In recent years, various treatment methods such as chemical precipitation, physical adsorption, and biological absorption have been developed and applied to the control of water body eutrophication. Among various methods, chemical precipitation has high costs and generates a large amount of solid waste; biological absorption may be limited by the sensitivity of microorganisms to the environment; the adsorption method has high selectivity and practicability and is an efficient and feasible method for removing phosphorus. Biochar is a carbon-rich material extracted from the pyrolysis process of biomass and has excellent adsorption properties for cations and organic pollutants. However, its adsorption capacity for anionic pollutants such as phosphates is very low. It must be modified to improve its adsorption capacity for phosphates.

[0003] Currently, many studies have reported methods for modifying biochar with metal cation reagents (such as La 3+ , Fe 3+ , Al 3+ and Mg 2+ ). The modification has greatly improved the adsorption performance for phosphates. However, a large amount of La 3+ , Fe 3+ and Al 3+ may leach out in the solution, especially under acidic conditions, which can cause harm to the aquatic ecosystem. Calcium (Ca) has relatively little harm to the aquatic environment, is easy to obtain, and is suitable for modifying biochar to improve the adsorption efficiency. However, synthetic materials modified with chemical reagents (Ca 2+ ) have the characteristics of complex operation and high costs, which limit the wide application of modified materials in practice, and the adsorption effect on phosphorus still needs to be improved. Summary of the Invention

[0004] The object of the present invention is to solve the problems existing in the prior art for treating water bodies polluted by phosphorus-containing substances, such as complex processes, high costs, and the need to improve the phosphorus adsorption effect. Therefore, a preparation method of biochar and its application are provided, and a method for removing phosphorus-containing substances in water is also involved. This biochar has excellent porous structures and has a continuously efficient and stable adsorption performance for phosphorus-containing substances, and can efficiently adsorb and remove phosphorus pollutants in water bodies. At the same time, its preparation method has obvious advantages of simple process flow, low cost, and environmental friendliness. Using environmental protection materials such as biogas residues and eggshells to prepare biochar realizes the resource utilization of waste, reduces the negative impact on the environment, and has better economic benefits.

[0005] In order to achieve the above object, on the one hand, the present invention provides a preparation method of biochar, characterized in that the preparation method includes: carbonizing the mixture of biogas residues and eggshells.

[0006] Preferably, the eggshells are selected from at least one of chicken eggshells, duck eggshells, goose eggshells, and quail eggshells.

[0007] More preferably, the eggshells are chicken eggshells.

[0008] Preferably, the mass ratio of the biogas residues to the eggshells in terms of dry weight is 1:1 - 3.

[0009] Preferably, the conditions of the carbonization reaction include: temperature of 800 - 900 °C, time of 90 - 180 min, and heating rate of 5 - 15 °C / min.

[0010] On the second aspect, the present invention provides a biochar prepared by the method as described above.

[0011] On the third aspect, the present invention provides an application of the biochar as described above in removing phosphorus-containing substances in a liquid.

[0012] Preferably, the phosphorus-containing substance is phosphate.

[0013] Preferably, the phosphorus-containing substance is dihydrogen phosphate.

[0014] On the fourth aspect, the present invention provides a method for removing phosphorus-containing substances in water, characterized in that the method includes: mixing the phosphorus-containing sewage with the biochar as described above.

[0015] Preferably, the conditions of the mixing include: temperature of 20 - 30 °C, time of 2 - 4 h.

[0016] Preferably, the mixing is carried out in a shaker.

[0017] Preferably, the phosphorus-containing substance is selected from orthophosphate and / or metaphosphate, preferably monohydrogen phosphate and dihydrogen phosphate, and more preferably dihydrogen phosphate.

[0018] Preferably, the dosage of the biochar is 0.2 - 0.4 g relative to 1 g of the phosphorus-containing substance.

[0019] Preferably, in the phosphorus-containing sewage, the content of the phosphorus-containing substance is 45 - 55 mg / L.

[0020] Preferably, the method further includes: filtering the mixed sewage.

[0021] Preferably, the aperture of the filter membrane used for filtration is 0.45 - 1.2 μm.

[0022] Through the above technical solution, the method provided by the present invention prepares porous biochar by treating biogas residue and eggshells using the high-temperature carbonization method, which has a good adsorption effect on the phosphorus-containing substances in water, can be used to remove phosphorus from sewage, and at the same time realizes the resource utilization of biogas residue carbon. It can adapt to different water quality conditions and treatment requirements, can be used multiple times, and further reduces the treatment cost. The biochar prepared by the preparation method of the present invention can continuously provide efficient and stable adsorption of the phosphorus-containing substances in water, meeting the long-term water pollution treatment requirements. The research and application of the biochar preparation method of the present invention promote scientific research and technological innovation in the field of water pollution treatment, and provide new ideas and methods for the treatment of other similar pollutants. Description of the Drawings

[0023] Figure 1 The standard curve graph of the phosphorus solution provided for the test example. Detailed Embodiments

[0024] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0025] As described above, the first aspect of the present invention provides a method for preparing biochar, which includes: mixing biogas residue and eggshells and performing a carbonization reaction.

[0026] There is no particular limitation on the mixing, and it can be selected from any one of stirring mixing and shaking mixing, as long as the biogas residue and eggshells can be completely mixed evenly.

[0027] During the research process, the inventors found that mixing biogas residue and eggshells to prepare biochar with a porous structure has the advantages of high efficiency and stability in the process of removing phosphorus-containing substances.

[0028] According to the present invention, preferably, the eggshell is selected from at least one of chicken eggshells, duck eggshells, goose eggshells, and quail eggshells. Therefore, further preferably, the eggshell is a chicken eggshell. The present invention does not particularly limit the crushing particle size of the chicken eggshell. It can be crushed with a porcelain mortar and mixed evenly with the biogas residue.

[0029] According to the present invention, preferably, the mass ratio of the biogas residue to the eggshell in terms of dry weight is 1:1 - 3, specifically it can be 1:1, 1:1.5, 1:2, 1:2.5, 1:3, or any value between these values. It has been found that controlling the mass ratio of the biogas residue to the eggshell within the above range can effectively improve the adsorption performance of the biochar.

[0030] According to the present invention, preferably, the conditions for the carbonization reaction include: the temperature is 800 - 900 °C, specifically it can be 800 °C, 820 °C, 830 °C, 850 °C, 880 °C, 900 °C, or any value between these values; the time is 90 - 180 min, specifically it can be 90 min, 120 min, 150 min, 180 min, or any value between these values; the heating rate is 5 - 15 °C / min, specifically it can be 5 °C / min, 8 °C / min, 10 °C / min, 12 °C / min, 13 °C / min, 15 °C / min, or any value between these values. The inventors have found that preparing the biochar in the above preferred manner can further improve the adsorption effect of the biochar.

[0031] The second aspect of the present invention provides a biochar, which is prepared by the method as described above.

[0032] As a phosphorus removal adsorbent, this biochar can meet the long-term water pollution treatment requirements, and its adsorption performance is more stable and efficient. The research and application of this biochar have promoted scientific research and technological innovation in the field of water pollution treatment, providing new ideas and methods for the treatment of other similar pollutants.

[0033] The third aspect of the present invention provides an application of the biochar prepared by the method as described above in removing phosphorus-containing substances in a liquid. The inventors have found that the biochar prepared by the present invention has a more obvious effect on adsorbing phosphorus-containing substances in water.

[0034] According to the present invention, preferably, the phosphorus-containing substance is dihydrogen phosphate. The inventors have found that when the phosphorus-containing substance is dihydrogen phosphate, the adsorption effect of the biochar on it is more obvious.

[0035] The fourth aspect of the present invention provides a method for removing phosphorus-containing substances in water, which includes: mixing the biochar as described above with phosphorus-containing sewage. The mixing is not particularly limited and can be selected from any one of stirring mixing and shaking mixing, as long as it can make the biochar and the phosphorus-containing sewage fully contact for adsorption.

[0036] According to the present invention, preferably, the conditions for mixing include: the temperature is 20 - 30°C, specifically it can be 20°C, 22°C, 24°C, 26°C, 28°C, 30°C, or any value between these values; the time is 2 - 4 h, specifically it can be 2 h, 2.5 h, 3 h, 3.5 h, 4 h, or any value between these values; and shaking on a shaker. The inventors have found through research that by adopting the above preferred implementation manner, the reaction between biochar and phosphorus-containing sewage can be more sufficient and efficient.

[0037] According to the present invention, preferably, the phosphorus-containing substance is selected from at least one of orthophosphate, metaphosphate, hydrogen phosphate, and dihydrogen phosphate. Preferably, relative to 1 g of the phosphorus-containing substance, the dosage of the biochar is 0.2 - 0.4 g; preferably, the content of the phosphorus-containing substance is 45 - 55 mg / L. The inventors have found through research that by adopting the above preferred implementation manner, the effect of biochar adsorbing phosphorus-containing substances in sewage can be further improved.

[0038] According to the present invention, preferably, the method for removing phosphorus-containing substances from water further includes: filtering the sewage after mixed adsorption. According to the present invention preferably, the pore size of the filter membrane used for filtration is 0.45 - 1.2 μm. In practical applications, the filtration equipment can be selected from syringe-type membrane filters, Pall capsule filters, Pall sterile filters, etc. Since the experiments of the present invention are carried out in the laboratory, a needle-hole filter (pore size specifications: 0.45 μm, 0.8 μm, and 1.2 μm) is selected for research operations. The inventors have found through research that by using the above preferred implementation manner in combination with biochar, the phosphorus removal effect can be higher.

[0039] The method provided above can significantly improve the phosphorus removal effect of sewage.

[0040] Preparation of ammonium molybdate and ascorbic acid solution (color reagent):

[0041] Ascorbic acid solution: Take 10 g of ascorbic acid solid powder in a beaker, and use a glass rod to drain it into a 100 ml volumetric flask and add water to the mark to obtain a 100 g / L ascorbic acid solution.

[0042] Ammonium molybdate solution: Dissolve 13 g of ammonium molybdate and 0.35 g of potassium antimonyl tartrate solid powder in 100 mL of water respectively. Then, while stirring continuously, slowly add the ammonium molybdate solution to 300 mL of sulfuric acid (1 + 1) solution. Finally, add the potassium antimonyl tartrate solution and mix evenly. (Sulfuric acid (1 + 1) refers to a solution prepared by mixing one volume of concentrated sulfuric acid and one volume of water in a ratio of 1:1.)

[0043] Preparation of phosphorus solution standard curve

[0044] Take potassium dihydrogen phosphate to prepare a phosphorus standard solution with a concentration of 50 mg / L. Take 5 10-mL colorimetric tubes and prepare phosphorus standard solutions with different concentration gradients (0.2 mg / L, 0.4 mg / L, 0.6 mg / L, 0.8 mg / L, 1.0 mg / L). Then add 0.4 mL of ammonium molybdate and 0.2 mL of ascorbic acid solution successively, and finally add deionized water to the mark. Then shake well and after color development for 15 minutes, measure the absorbance with a spectrophotometer.

[0045] Measure the absorbance values of the 5 colorimetric tubes at a wavelength of 700 nm.

[0046] Draw a curve of absorbance value against phosphorus content (mg / L) to obtain the phosphorus solution standard curve. As Figure 1 shown.

[0047] The regression equation of the calibration curve is y = 0.39671x - 0.00286, R 2 = 0.999

[0048] In the following examples, the eggshells are from food waste; the biogas residue is purchased from Anhui Haoyue Environmental Technology Co., Ltd. The rest of the reagents and raw materials are all conventional commercially available products.

[0049] Example 1-1

[0050] Mix the biogas residue and eggshell fragments in a porcelain mortar according to a mass ratio of 1:2 to obtain a mixture; transfer all the mixture to an ash dish, and then in a tubular furnace, increase the temperature from room temperature to 800 °C at a heating rate of 10 °C / min and stay for 120 min. The obtained biochar is denoted as BC 1.

[0051] Example 1-2

[0052] Mix the biogas residue and eggshell fragments in a porcelain mortar according to a mass ratio of 1:3 to obtain a mixture; transfer all the well-mixed mixture of biogas residue and eggshells to an ash dish, and then in a tubular furnace, increase the temperature from room temperature to 800 °C at a heating rate of 10 °C / min and stay for 120 min. The obtained biochar is denoted as BC 2.

[0053] Example 1-3

[0054] Mix the biogas residue and eggshells in a porcelain mortar according to a mass ratio of 1:1 to obtain a mixture; transfer all the well-mixed mixture of biogas residue and eggshells to an ash dish, and then in a tubular furnace, increase the temperature from room temperature to 800 °C at a heating rate of 10 °C / min and stay for 120 min. The obtained biochar is denoted as BC 3.

[0055] Example 1-4

[0056] Mix the biogas residue and eggshells in a porcelain mortar according to a mass ratio of 1:0.5 to obtain a mixture; transfer all the evenly mixed biogas residue and eggshell mixture to a crucible, and then raise the temperature from room temperature to 800 °C at a heating rate of 10 °C / min in a tube furnace and hold for 120 min. The resulting biochar is denoted as BC 4.

[0057] Examples 1-5

[0058] Mix the biogas residue and eggshells in a porcelain mortar according to a mass ratio of 3:1 to obtain a mixture; transfer all the evenly mixed biogas residue and eggshell mixture to a crucible, and then raise the temperature from room temperature to 800 °C at a heating rate of 10 °C / min in a tube furnace and hold for 120 min. The resulting biochar is denoted as BC 5.

[0059] Examples 1-6

[0060] Prepare biochar according to the method described in Example 1-1, except that the pyrolysis temperature is adjusted to 700 °C. The resulting biochar is denoted as BC6.

[0061] Comparative Example 1

[0062] Prepare biochar according to the method described in Example 1-1, except that no eggshells are added. The resulting biochar is denoted as BC A.

[0063] Example 2-1

[0064] Take the biochar BC 1 obtained by the preparation method of Example 1-1 above, mix it with a 50 mg / L potassium dihydrogen phosphate solution, the addition amount of biochar per 100 ml of potassium dihydrogen phosphate solution is 0.02 g, the mixing temperature is 25 °C, shake it on a shaker, and after 3 h the reaction ends. The resulting phosphorus-adsorbed solution is filtered through a syringe filter with a pore size of 0.45 μm to obtain a filtrate, and collect the filtrate.

[0065] Example 2-2

[0066] Take the biochar BC 2 obtained by the preparation method of Example 1-2 above, mix it with a 50 mg / L potassium dihydrogen phosphate solution, the addition amount of biochar per 100 ml of potassium dihydrogen phosphate solution is 0.02 g, the mixing temperature is 25 °C, shake it on a shaker, and after 3 h the reaction ends. The resulting phosphorus-adsorbed solution is filtered through a syringe filter with a pore size of 0.45 μm, and collect the filtrate.

[0067] Example 2-3

[0068] Take the biochar BC 3 obtained by the preparation method of the above Examples 1-3, mix it with a potassium dihydrogen phosphate solution at 50 mg / L, add 0.02 g of biochar to every 100 mL of the potassium dihydrogen phosphate solution, keep the mixing temperature at 25 °C, shake it on a shaker, end the reaction after 3 h, filter the adsorbed phosphorus solution through a syringe filter with a pore size of 0.45 μm, and collect the filtrate.

[0069] Examples 2-4

[0070] Take the biochar BC 4 obtained by the preparation method of the above Examples 1-4, mix it with a potassium dihydrogen phosphate solution at 50 mg / L, add 0.02 g of biochar to every 100 mL of the potassium dihydrogen phosphate solution, keep the mixing temperature at 25 °C, shake it on a shaker, end the reaction after 3 h, filter the adsorbed phosphorus solution through a syringe filter with a pore size of 0.45 μm, and collect the filtrate.

[0071] Examples 2-5

[0072] Carry out the adsorption reaction according to the method of Example 2-1, except that the biochar BC 1 obtained by the preparation method of Example 1-1 is replaced with the biochar BC 5 obtained by the preparation method of Example 1-5.

[0073] Examples 2-6

[0074] Carry out the adsorption reaction according to the method of Example 2-2, except that the biochar BC 1 obtained by the preparation method of Example 1-1 is replaced with the biochar BC 6 obtained by the preparation method of Example 1-6.

[0075] Comparative Example 2

[0076] Carry out the adsorption reaction according to the method of Example 2-2, except that the biochar BC 2 obtained by the preparation method of Example 1-2 is replaced with the biochar BC A obtained by the preparation method of Comparative Example 1-1.

[0077] Test Example 1

[0078] Use a pipette to take 1 mL of the filtrates obtained in the above Examples 2-1 to 2-6 and Comparative Example 2, put it into a 10 mL colorimetric tube, and successively add 0.4 mL of 26 g / L ammonium molybdate solution and 0.2 mL of 100 g / L ascorbic acid solution, and finally add deionized water to the mark. Then shake well and develop color for 15 minutes, and measure the absorbance with a spectrophotometer. According to Figure 1 the standard curve shown, obtain the content of potassium dihydrogen phosphate, and then calculate the removal rate and adsorption capacity of potassium dihydrogen phosphate. The analysis results are shown in Table 1;

[0079] Table 1

[0080] Number Adsorption rate (%) Adsorption capacity (mg / g) Example 2-1 96.51 241.27 Example 2-2 95.75 239.38 Example 2-3 87.68 219.21 Example 2-4 43.83 109.56 Example 2-5 -1.05 -2.62 Example 2-6 -175.98 -439.96 Comparative Example 2 -184.3 -460.76

[0081] As can be seen from Table 1, the adsorption rate and adsorption capacity of the biochar prepared in the examples for phosphorus-containing substances in the phosphorus solution are significantly higher than those of the biochar prepared in the comparative examples. Therefore, the phosphorus removal effect of the biochar acid prepared by the method provided by the present invention is better.

[0082] Test Example 2

[0083] The adsorption reaction was carried out according to the method of Example 2-1. After the reaction was completed, the biochar was recycled and regenerated with sodium hydroxide solution, and then a 50 mg / L potassium dihydrogen phosphate solution was added to continue the adsorption reaction. This cycle was repeated five times, and the adsorption rate and adsorption capacity of potassium dihydrogen phosphate in the filtrate obtained from each reaction were measured. The data obtained are shown in Table 2.

[0084] Table 2

[0085] Adsorption rate (%) Adsorption capacity (mg / g) First time 96.51 241.27 Second time 88.44 221.1 Third time 86.93 217.32 Fourth time 85.92 214.8 Fifth time 83.65 209.13

[0086] As can be seen from Table 2, for each adsorption reaction, the adsorption rate and adsorption capacity of potassium dihydrogen phosphate slightly decreased, and each decrease was within 10%. Therefore, the biochar prepared by the present invention has high cycle stability and great industrial development prospects.

[0087] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A method for preparing biochar, characterized in that: The preparation method comprises: mixing biogas residue and eggshells and then performing a carbonization reaction.

2. The preparation method according to claim 1, characterized in that: The eggshell is selected from at least one of chicken eggshell, duck eggshell, goose egg and quail egg; Preferably, the eggshell is an hen's egg shell.

3. The preparation method according to claim 1, characterized in that: The mass ratio of the biogas residue to the eggshell based on dry weight is 1:1-3.

4. The preparation method according to claim 1, characterized in that: The conditions of the carbonization reaction include: temperature of 800-900°C, time of 90-180min, and heating rate of 5-15°C / min.

5. A biochar, characterized in that: The biochar is prepared by the preparation method according to any one of claims 1 to 4.

6. Use of the biochar according to claim 5 in removing phosphorus-containing substances in liquid; Preferably, the phosphorus-containing substance is phosphate; Preferably, the phosphorus-containing substance is dihydrogen phosphate.

7. A method for removing phosphorus-containing substances in water, characterized in that: The method comprises: mixing phosphorus-containing wastewater with the biochar described in claim 5.

8. The method according to claim 7, characterized in that The mixing conditions include: temperature of 20-30°C and time of 2-4h; Preferably, the mixing is performed in a shaker.

9. The method according to claim 7, characterized in that: The phosphorus-containing substance is selected from orthophosphate and / or metaphosphate, preferably monohydrogen phosphate and dihydrogen phosphate, and more preferably dihydrogen phosphate; Preferably, the amount of the biochar is 0.2-0.4 g relative to 1 g of the phosphorus-containing substance; Preferably, in the phosphorus-containing wastewater, the content of the phosphorus-containing substance is 45-55 mg / L.

10. The method according to claim 7, characterized in that The method further comprises: filtering the mixed sewage; Preferably, the pore size of the filter membrane used for the filtration is 0.45-1.2 μm.

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