Method for preparing biochar from spartina alterniflora and application of biochar in nitrogen and phosphorus removal

Abstract

The invention provides a method for preparing biochar from spartina alterniflora and application of the biochar in nitrogen and phosphorus removal, and belongs to the technical field of biological materials. According to the method, the widely distributed spartina alterniflora is converted into the biochar, so that high-value utilization of invasive plants is realized, and environmental pollution is reduced. The biochar provided by the invention has excellent performance in the aspects of nitrogen and phosphorus removal, effectively improves water eutrophication, improves water quality and protects an aquatic ecosystem. The preparation method is simple, cost is reduced, and large-scale production is facilitated. And the method is environment-friendly, does not generate secondary pollution, and accords with sustainable development. The invention not only provides a new environment restoration material, but also opens up a new way for biomass resource utilization, has remarkable economic and social benefits, improves public health, improves life quality and protects biological diversity.

Description

Technical Field

[0001] The invention relates to the technical field of biomaterials, and in particular to a method for preparing biochar by utilizing Spartina alterniflora and application of the method in nitrogen and phosphorus removal. Background Art

[0002] In the field of environmental pollution control and ecological restoration, biochar has attracted widespread attention as a potential environmental restoration material. Biochar is a porous material with a high carbon content obtained by pyrolysis of biomass under anaerobic or limited oxygen conditions. It has a large specific surface area and a developed pore structure. These characteristics make biochar show certain application potential in soil improvement, pollution control, carbon sequestration and emission reduction.

[0003] However, existing biochar preparation technologies have some limitations. First, traditional biochar preparation methods usually rely on specific biomass resources, which limits the source of raw materials and the stability of supply. For example, some methods may require specific agricultural waste or specific biomass materials, which may pose challenges in terms of raw material acquisition and cost control. In addition, the production cost of biochar is relatively high, and it may face technical and economic challenges when applied on a large scale.

[0004] In terms of nitrogen and phosphorus removal, existing technologies often rely on chemical agents and microbial treatments, which may be inefficient, costly, or cause secondary pollution. Although biochar has a certain ability to remove nitrogen and phosphorus, its effect is affected by preparation conditions, raw material characteristics, and application methods, and in practical applications it often needs to be used in conjunction with other technologies to improve treatment efficiency. In addition, the application of biochar in water nitrogen and phosphorus removal also faces the challenge of how to improve its adsorption performance and stability, as well as how to achieve the long-term effectiveness and environmental friendliness of biochar.

[0005] Chinese patent CN201210078182.5 describes a method for producing biochar using Spartina alterniflora and green waste. Although this method achieves resource utilization to a certain extent, its preparation process is complicated and has high requirements on the environment and equipment, which limits its wide application.

[0006] Existing technologies have been exploring more efficient and low-cost biochar preparation methods, as well as how to improve the application effect of biochar in environmental remediation. Although some progress has been made, there is still a lot of room for improvement in terms of biochar preparation process optimization, cost control, and improving its performance in nitrogen removal and phosphorus removal. Therefore, developing new biochar preparation technologies and exploring its new applications in environmental remediation have become research hotspots in this field. Summary of the invention

[0007] The object of the present invention is to provide a method for preparing biochar using Spartina alterniflora and its application in nitrogen and phosphorus removal, which has excellent effects.

[0008] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0009] The present invention provides a method for preparing Spartina alterniflora biochar, comprising the following steps:

[0010] The Spartina alterniflora is mixed with auxiliary materials, and subjected to pyrolysis treatment after natural fermentation to obtain Spartina alterniflora biochar;

[0011] The auxiliary materials contain wheat straw, corn stalk and bentonite.

[0012] Preferably, in parts by weight, the amount of Spartina alterniflora is 40 to 60 parts, the amount of wheat straw is 20 to 40 parts, the amount of corn stalk is 10 to 20 parts, and the amount of bentonite is 3 to 8 parts.

[0013] Preferably, the volume of the naturally fermented material is greater than 1 cubic meter.

[0014] Preferably, the natural fermentation time is 20 to 40 days.

[0015] Preferably, the Spartina alterniflora is crushed before use, and the crushed particle size is less than 0.5 mm.

[0016] Preferably, in the pyrolysis treatment, the pyrolysis temperature is 500-700°C;

[0017] In the pyrolysis treatment, the heating rate is 5 to 10°C / min;

[0018] In the pyrolysis treatment, the heat preservation time is 20 to 50 minutes.

[0019] Preferably, the pyrolysis treatment is carried out in a nitrogen atmosphere with a nitrogen flow rate of 0.3 to 0.5 m 3 / s.

[0020] Preferably, the biochar further comprises adjusting the pH to 6.5-7.0;

[0021] The pH adjustment uses citric acid solution as a regulator, and the concentration of the citric acid solution is 3-5%.

[0022] The present invention provides Spartina alterniflora biochar prepared by the preparation method.

[0023] The present invention provides application of the Spartina alterniflora biochar in denitrification and phosphorus removal in water bodies.

[0024] Technical effects and advantages of the present invention:

[0025] The present invention realizes the high-value utilization of this widely distributed invasive plant resource by converting Spartina alterniflora into biochar. This conversion not only reduces the burden of invasive plants on the environment, but also provides new possibilities for the recycling of biomass resources. Through this innovative method, Spartina alterniflora is no longer a simple invasive plant, but becomes an environmentally friendly material with high adsorption performance, which is of great significance in resource recycling and environmental protection.

[0026] In terms of environmental restoration, Spartina alterniflora biochar has demonstrated excellent capabilities, especially in the application of nitrogen and phosphorus removal. This biochar can effectively improve the eutrophication of water bodies and improve the quality of the water environment. It plays an important role in restoring and protecting the health of aquatic ecosystems. By absorbing nitrogen and phosphorus compounds in water, biochar helps reduce the nutrient load in water bodies, thereby inhibiting the excessive reproduction of algae and maintaining the ecological balance of water bodies.

[0027] The method for preparing Spartina alterniflora biochar is simple and easy, without the need for complex equipment and processes, which makes it have obvious advantages in large-scale production and application. The simple preparation process reduces production costs while ensuring efficient output of biochar, which lays the foundation for the commercial production and widespread application of biochar.

[0028] Environmental friendliness is another highlight of the present invention. The preparation and application of biochar does not produce secondary pollution, which fully meets the requirements of sustainable development. This material will not cause new burdens on the environment while adsorbing and removing pollutants in water bodies, and is a truly green solution.

[0029] The present invention not only provides an effective environmental restoration material, but also opens up a new way for the utilization of biomass resources such as Spartina alterniflora. This innovative application not only has significant economic benefits, but also has far-reaching social benefits, including improving public health, improving quality of life and protecting biodiversity, by reducing the cost of environmental pollution control and improving resource utilization efficiency. Through this innovative technology, we can use natural resources more effectively while protecting and improving the environment on which we depend for survival. DETAILED DESCRIPTION

[0030] The present invention provides a method for preparing Spartina alterniflora biochar, comprising the following steps:

[0031] The Spartina alterniflora is mixed with auxiliary materials, and subjected to pyrolysis treatment after natural fermentation to obtain Spartina alterniflora biochar;

[0032] The auxiliary materials contain wheat straw, corn stalk and bentonite.

[0033] The present invention utilizes wheat straw, corn stalk and bentonite as composite auxiliary materials to pyrolyze together with Spartina alterniflora to prepare a method for biochar, and enhances the adsorption and catalytic properties of biochar through the physical and chemical properties of these auxiliary materials. Wheat straw and corn stalk are rich in cellulose and lignin, and these organic substances can form more carbon skeletons and microporous structures during the pyrolysis process, thereby increasing the specific surface area and porosity of biochar and improving its adsorption capacity for nitrogen and phosphorus. At the same time, these biomasses can also release minerals such as potassium and magnesium during the pyrolysis process, and these minerals can be used as plant nutrients to promote the metabolic activities of microorganisms and further improve the efficiency of denitrification and phosphorus removal. Bentonite, as a natural clay mineral, has a large specific surface area and cation exchange capacity, and can adsorb nitrogen and phosphorus compounds in water bodies. At the same time, its layered structure may form a complex with biochar during the pyrolysis process, enhancing the stability and adsorption performance of biochar. The present invention successfully combines the characteristics of these auxiliary materials, and the prepared biochar shows more excellent performance in denitrification and phosphorus removal.

[0034] In the present invention, preferably, in parts by weight, the amount of Spartina alterniflora is 40 to 60 parts, the amount of wheat straw is 20 to 40 parts, the amount of corn stalk is 10 to 20 parts, and the amount of bentonite is 3 to 8 parts. Preferably, the volume of the naturally fermented material is more than 1 cubic meter. Preferably, the time of the natural fermentation is 20 to 40 days. In the natural fermentation process of the present invention, the metabolic activity of microorganisms can pre-treat the raw materials, which helps to decompose the complex organic matter in the raw materials and produce more soluble organic carbon and nutrients, which can be converted into surface functional groups of biochar in the subsequent pyrolysis process, thereby increasing the chemical activity and adsorption capacity of biochar; the metabolites produced by microbial activity, such as organic acids, can etch the pore structure of biochar to a certain extent, increasing its specific surface area and porosity. This improved pore structure helps to improve the adsorption performance of biochar, making it more effective in environmental remediation processes such as nitrogen removal and phosphorus removal.

[0035] In the present invention, preferably, the Spartina alterniflora is crushed before application, and the crushed particle size is less than 0.5 mm. Preferably, in the pyrolysis treatment, the pyrolysis temperature is 500-700°C; in the pyrolysis treatment, the heating rate is 5-10°C / min; in the pyrolysis treatment, the insulation time is 20-50 min.

[0036] The parameters of the pyrolysis treatment described in the present invention can obtain the optimal biochar performance, and the pyrolysis temperature is a key factor affecting the structure and properties of biochar. Within this temperature range, high molecular organic substances such as hemicellulose, cellulose and lignin in the biomass raw materials can be fully decomposed to form a rich pore structure and a large specific surface area. A lower pyrolysis temperature may lead to incomplete decomposition of organic matter, while too high a temperature may cause excessive graphitization of biochar, thereby reducing its porosity. The temperature range provided by the present invention helps to balance the carbonization degree and pore development of biochar, and obtain suitable adsorption performance and structural stability.

[0037] The heating rate determines the speed of pyrolysis of biomass raw materials, which in turn affects the physical and chemical properties of biochar. A slower heating rate may lead to excessive oxidation of biochar, while rapid heating may lead to insufficient decomposition of organic matter. The heating rate provided by the present invention can ensure that the biomass raw materials are gradually and evenly decomposed during the pyrolysis process, which is conducive to the formation of a stable pore structure and suitable surface functional groups, thereby improving the adsorption performance of biochar.

[0038] The holding time is the key to ensure that the biomass raw materials are fully decomposed and rearranged during the pyrolysis process. A shorter holding time may lead to incomplete decomposition of organic matter, while a longer holding time may cause excessive solidification of the biochar structure. The holding time provided by the present invention can ensure that the organic matter in the biochar is fully decomposed, while maintaining a certain degree of carbonization and avoiding excessive graphitization, thereby obtaining higher biochar quality and adsorption performance.

[0039] The present invention optimizes the preparation process of biochar by precisely controlling the pyrolysis temperature, heating rate and holding time, so that the obtained biochar has a suitable pore structure, specific surface area and surface functional groups, thereby showing excellent performance in environmental remediation applications such as nitrogen removal and phosphorus removal. This finely controlled pyrolysis treatment parameter helps to maximize the performance of biochar and improve its efficiency and effectiveness in environmental governance.

[0040] In the present invention, preferably, the pyrolysis treatment is carried out in a nitrogen atmosphere, and the nitrogen flow rate is 0.3-0.5 m 3 / s. Preferably, the biochar further comprises adjusting the pH to 6.5-7.0; the pH adjustment uses citric acid solution as a regulator, and the concentration of the citric acid solution is 3-5%.

[0041] The present invention provides Spartina alterniflora biochar prepared by the preparation method.

[0042] The present invention provides the application of the Spartina alterniflora biochar in denitrification and phosphorus removal in water bodies, including the following application methods:

[0043] Direct dosing:

[0044] The Spartina alterniflora biochar prepared by the present invention is directly added to the water body. This method is simple and direct, and is suitable for occasions where the treatment scale is small or a quick response is required. The biochar directly removes nitrogen and phosphorus in the water through adsorption.

[0045] Fixed bed technology:

[0046] A biochar immobilized bed is constructed, and the Spartina alterniflora biochar provided by the present invention is filled in a reactor, and when water flows through, nitrogen and phosphorus are adsorbed and removed by the biochar. This method is suitable for continuous treatment of water bodies and can continuously and stably purify water quality.

[0047] Mixed with adsorption material:

[0048] The Spartina alterniflora biochar provided by the present invention is mixed with other adsorption materials (such as zeolite, activated carbon, etc.) and then put into a water body. This combination can improve the adsorption efficiency, broaden the adsorption range, and is suitable for the removal of various pollutants.

[0049] Combined with microorganisms:

[0050] The Spartina alterniflora biochar provided by the present invention is compounded with microorganisms with specific functions (such as denitrification bacteria and dephosphorization bacteria) and then added into a water body. The biochar acts as a carrier for microorganisms, provides a growth environment, and enhances the denitrification and dephosphorization effects of the microorganisms.

[0051] Symbiotic system with aquatic plants:

[0052] Aquatic plants are planted in a water body, and the Spartina alterniflora biochar provided by the present invention is added to the root area of ​​the plants. The biochar can promote plant growth and work together with the plant root system to improve the removal efficiency of nitrogen and phosphorus.

[0053] As flocculant auxiliary material:

[0054] When using chemical flocculants to treat water bodies, the Spartina alterniflora biochar provided by the present invention is added as an auxiliary material. The biochar can absorb nitrogen and phosphorus released during the flocculation process, improve the flocculation effect, and reduce the amount of chemical flocculants used.

[0055] Combined with sediment improvement:

[0056] The Spartina alterniflora biochar provided by the present invention is added into the bottom mud of the water body to improve the physical and chemical properties of the bottom mud, promote the fixation and conversion of nitrogen and phosphorus in the bottom mud, and reduce the release of nitrogen and phosphorus in the bottom mud.

[0057] Dynamic circulation processing system:

[0058] A dynamic circulation system is constructed, and the Spartina alterniflora biochar provided by the present invention is placed in a circulation filtration unit. When the water body circulates through the filter material, nitrogen and phosphorus are continuously removed, which is suitable for long-term maintenance of aquaculture and landscape water bodies.

[0059] The above application methods can be selected and adjusted according to specific water conditions and treatment objectives to achieve the best nitrogen and phosphorus removal effects.

[0060] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0061] Example 1

[0062] Raw material selection

[0063] Spartina alterniflora was selected as the main pyrolysis material, and wheat straw, corn stalk and bentonite were selected as composite auxiliary materials.

[0064] Preprocessing

[0065] The Spartina alterniflora and auxiliary materials are thoroughly washed with clean water to remove mud, sand and impurities, and the washed raw materials are dried in a natural environment until the moisture content is less than 10%, and the dried raw materials are crushed into a particle size of less than 0.25 mm using an industrial crusher.

[0066] Pyrolysis: The pretreated Spartina alterniflora, wheat straw, corn stalk and bentonite were mixed in a ratio of 50%, 30%, 15% and 5%, and the mixture (2 cubic meters) was sealed and stored for 30 days to promote natural fermentation. Anaerobic pyrolysis was carried out under nitrogen atmosphere, the pyrolysis temperature was set at 550°C, the heating rate was 5°C / min, the holding time was 30min, and the nitrogen flow rate was maintained at 0.32 cubic meters / second.

[0067] Post-processing

[0068] After pyrolysis is completed, the biochar is naturally cooled to room temperature in a N2 atmosphere; it is sieved through a 40-mesh sieve to remove oversized particles, and finally the biochar is mixed with a 5% citric acid solution, and the pH is adjusted to 7.0 for use.

[0069] Example 2

[0070] Raw material selection

[0071] Spartina alterniflora was selected as the main pyrolysis material, and wheat straw, corn stalk and bentonite were selected as composite auxiliary materials.

[0072] Preprocessing

[0073] The Spartina alterniflora and auxiliary materials are thoroughly washed with clean water to remove mud, sand and impurities, and the washed raw materials are dried in a natural environment until the moisture content is less than 10%, and the dried raw materials are crushed into a particle size of less than 0.25 mm using an industrial crusher.

[0074] Pyrolysis: The pretreated Spartina alterniflora, wheat straw, corn stalk and bentonite were mixed in a ratio of 50%, 30%, 15% and 5%, and the mixture (2 cubic meters) was sealed and stored for 30 days to promote natural fermentation. Anaerobic pyrolysis was carried out under nitrogen atmosphere, the pyrolysis temperature was set at 600°C, the heating rate was 5°C / min, the holding time was 30min, and the nitrogen flow rate was maintained at 0.32 cubic meters / second.

[0075] Post-processing

[0076] After pyrolysis is completed, the biochar is naturally cooled to room temperature in a N2 atmosphere; it is sieved through a 40-mesh sieve to remove oversized particles, and finally the biochar is mixed with a 5% citric acid solution, and the pH is adjusted to 7.0 for use.

[0077] Example 3

[0078] Raw material selection

[0079] Spartina alterniflora was selected as the main pyrolysis material, and wheat straw, corn stalk and bentonite were selected as composite auxiliary materials.

[0080] Preprocessing

[0081] The Spartina alterniflora and auxiliary materials are thoroughly washed with clean water to remove mud, sand and impurities, and the washed raw materials are dried in a natural environment until the moisture content is less than 10%, and the dried raw materials are crushed into a particle size of less than 0.25 mm using an industrial crusher.

[0082] Pyrolysis: The pretreated Spartina alterniflora, wheat straw, corn stalk and bentonite were mixed in a ratio of 50%, 30%, 15% and 5%, and the mixture (2 cubic meters) was sealed and stored for 30 days to promote natural fermentation. Anaerobic pyrolysis was carried out under nitrogen atmosphere, the pyrolysis temperature was set at 550°C, the heating rate was 10°C / min, the holding time was 30min, and the nitrogen flow rate was maintained at 0.32 cubic meters / second.

[0083] Post-processing

[0084] After pyrolysis is completed, the biochar is naturally cooled to room temperature in a N2 atmosphere; it is sieved through a 40-mesh sieve to remove oversized particles, and finally the biochar is mixed with a 5% citric acid solution, and the pH is adjusted to 7.0 for use.

[0085] Example 4

[0086] Raw material selection

[0087] Spartina alterniflora was selected as the main pyrolysis material, and wheat straw, corn stalk and bentonite were selected as composite auxiliary materials.

[0088] Preprocessing

[0089] The Spartina alterniflora and auxiliary materials are thoroughly washed with clean water to remove mud, sand and impurities, and the washed raw materials are dried in a natural environment until the moisture content is less than 10%, and the dried raw materials are crushed into a particle size of less than 0.25 mm using an industrial crusher.

[0090] Pyrolysis: The pretreated Spartina alterniflora, wheat straw, corn stalk and bentonite were mixed in a ratio of 50%, 30%, 15% and 5%, and the mixture (2 cubic meters) was sealed and stored for 30 days to promote natural fermentation. Anaerobic pyrolysis was carried out under nitrogen atmosphere, the pyrolysis temperature was set at 550°C, the heating rate was 5°C / min, the holding time was 45min, and the nitrogen flow rate was maintained at 0.32 cubic meters / second.

[0091] Post-processing

[0092] After pyrolysis is completed, the biochar is naturally cooled to room temperature in a N2 atmosphere; it is sieved through a 40-mesh sieve to remove oversized particles, and finally the biochar is mixed with a 5% citric acid solution, and the pH is adjusted to 7.0 for use.

[0093] Example 5

[0094] Raw material selection

[0095] Spartina alterniflora was selected as the main pyrolysis material, and wheat straw, corn stalk and bentonite were selected as composite auxiliary materials.

[0096] Preprocessing

[0097] The Spartina alterniflora and auxiliary materials are thoroughly washed with clean water to remove mud, sand and impurities, and the washed raw materials are dried in a natural environment until the moisture content is less than 10%, and the dried raw materials are crushed into a particle size of less than 0.25 mm using an industrial crusher.

[0098] Pyrolysis: The pretreated Spartina alterniflora, wheat straw, corn stalk and bentonite were mixed in a ratio of 50%, 30%, 15% and 5%, and the mixture (2 cubic meters) was sealed and stored for 30 days to promote natural fermentation. Anaerobic pyrolysis was carried out under nitrogen atmosphere, the pyrolysis temperature was set at 550°C, the heating rate was 5°C / min, the holding time was 30min, and the nitrogen flow rate was maintained at 0.4 cubic meters / second.

[0099] Post-processing

[0100] After pyrolysis is completed, the biochar is naturally cooled to room temperature in a N2 atmosphere; it is sieved through a 40-mesh sieve to remove oversized particles, and finally the biochar is mixed with a 5% citric acid solution, and the pH is adjusted to 7.0 for use.

[0101] Example 6

[0102] Raw material selection

[0103] Spartina alterniflora was selected as the main pyrolysis material, and wheat straw, corn stalk and bentonite were selected as composite auxiliary materials.

[0104] Preprocessing

[0105] The Spartina alterniflora and auxiliary materials are thoroughly washed with clean water to remove mud, sand and impurities, and the washed raw materials are dried in a natural environment until the moisture content is less than 10%, and the dried raw materials are crushed into a particle size of less than 0.25 mm using an industrial crusher.

[0106] Pyrolysis: The pretreated Spartina alterniflora, wheat straw, corn stalk and bentonite were mixed in a ratio of 45%, 35%, 15% and 5%, and the mixture (2 cubic meters) was sealed and stored for 30 days to promote natural fermentation. Anaerobic pyrolysis was carried out under nitrogen atmosphere, the pyrolysis temperature was set at 550°C, the heating rate was 5°C / min, the holding time was 30min, and the nitrogen flow rate was maintained at 0.32 cubic meters / second.

[0107] Post-processing

[0108] After pyrolysis is completed, the biochar is naturally cooled to room temperature in a N2 atmosphere; it is sieved through a 40-mesh sieve to remove oversized particles, and finally the biochar is mixed with a 5% citric acid solution, and the pH is adjusted to 7.0 for use.

[0109] Example 7

[0110] Raw material selection

[0111] Spartina alterniflora was selected as the main pyrolysis material, and wheat straw, corn stalk and bentonite were selected as composite auxiliary materials.

[0112] Preprocessing

[0113] The Spartina alterniflora and auxiliary materials are thoroughly washed with clean water to remove mud, sand and impurities, and the washed raw materials are dried in a natural environment until the moisture content is less than 10%, and the dried raw materials are crushed into a particle size of less than 0.25 mm using an industrial crusher.

[0114] Pyrolysis: The pretreated Spartina alterniflora, wheat straw, corn stalk and bentonite were mixed in a ratio of 50%, 30%, 15% and 5%, and the mixture (2 cubic meters) was sealed and stored for 45 days to promote natural fermentation. Anaerobic pyrolysis was carried out under nitrogen atmosphere, the pyrolysis temperature was set at 550°C, the heating rate was 5°C / min, the holding time was 30min, and the nitrogen flow rate was maintained at 0.32 cubic meters / second.

[0115] Post-processing

[0116] After pyrolysis is completed, the biochar is naturally cooled to room temperature in a N2 atmosphere; it is sieved through a 40-mesh sieve to remove oversized particles, and finally the biochar is mixed with a 5% citric acid solution, and the pH is adjusted to 7.0 for use.

[0117] Example 8

[0118] Raw material selection

[0119] Spartina alterniflora was selected as the main pyrolysis material, and wheat straw, corn stalk and bentonite were selected as composite auxiliary materials.

[0120] Preprocessing

[0121] The Spartina alterniflora and auxiliary materials are thoroughly washed with clean water to remove mud, sand and impurities, and the washed raw materials are dried in a natural environment until the moisture content is less than 10%, and the dried raw materials are crushed into a particle size of less than 0.5 mm using an industrial crusher.

[0122] Pyrolysis: The pretreated Spartina alterniflora, wheat straw, corn stalk and bentonite were mixed in a ratio of 50%, 30%, 15% and 5%, and the mixture (2 cubic meters) was sealed and stored for 30 days to promote natural fermentation. Anaerobic pyrolysis was carried out under nitrogen atmosphere, the pyrolysis temperature was set at 550°C, the heating rate was 5°C / min, the holding time was 30min, and the nitrogen flow rate was maintained at 0.32 cubic meters / second.

[0123] Post-processing

[0124] After pyrolysis is completed, the biochar is naturally cooled to room temperature in a N2 atmosphere; it is sieved through a 40-mesh sieve to remove oversized particles, and finally the biochar is mixed with a 5% citric acid solution, and the pH is adjusted to 7.0 for use.

[0125] Example 9

[0126] Raw material selection

[0127] Spartina alterniflora was selected as the main pyrolysis material, and wheat straw, corn stalk and bentonite were selected as composite auxiliary materials.

[0128] Preprocessing

[0129] The Spartina alterniflora and auxiliary materials are thoroughly washed with clean water to remove mud, sand and impurities, and the washed raw materials are dried in a natural environment until the moisture content is less than 10%, and the dried raw materials are crushed into a particle size of less than 0.25 mm using an industrial crusher.

[0130] Pyrolysis: The pretreated Spartina alterniflora, wheat straw, corn stalk and bentonite were mixed in a ratio of 50%, 30%, 15% and 5%, and the mixture (2 cubic meters) was sealed and stored for 30 days to promote natural fermentation. Anaerobic pyrolysis was carried out under nitrogen atmosphere, the pyrolysis temperature was set at 550°C, the heating rate was 5°C / min, the holding time was 30min, and the nitrogen flow rate was maintained at 0.32 cubic meters / second.

[0131] Post-processing

[0132] After pyrolysis is completed, the biochar is naturally cooled to room temperature in a N2 atmosphere; it is sieved through a 40-mesh sieve to remove oversized particles, and finally the biochar is mixed with a 3% citric acid solution, and the pH is adjusted to 7.0 for use.

[0133] Example 10

[0134] Raw material selection

[0135] Spartina alterniflora was selected as the main pyrolysis material, and wheat straw, corn stalk and bentonite were selected as composite auxiliary materials.

[0136] Preprocessing

[0137] The Spartina alterniflora and auxiliary materials are thoroughly washed with clean water to remove mud, sand and impurities, and the washed raw materials are dried in a natural environment until the moisture content is less than 10%, and the dried raw materials are crushed into a particle size of less than 0.25 mm using an industrial crusher.

[0138] Pyrolysis: The pretreated Spartina alterniflora, wheat straw, corn stalk and bentonite were mixed in a ratio of 50%, 30%, 15% and 5%, and the mixture (2 cubic meters) was sealed and stored for 30 days to promote natural fermentation. Anaerobic pyrolysis was carried out under nitrogen atmosphere, the pyrolysis temperature was set at 550°C, the heating rate was 5°C / min, the holding time was 30min, and the nitrogen flow rate was maintained at 0.32 cubic meters / second.

[0139] Post-processing

[0140] After pyrolysis is completed, the biochar is naturally cooled to room temperature in a N2 atmosphere; it is sieved through a 40-mesh sieve to remove oversized particles, and finally the biochar is mixed with a 5% citric acid solution, and the pH is adjusted to 6.5 for use.

[0141] Comparative Example 1

[0142] Raw material selection

[0143] Spartina alterniflora was selected as the main material for pyrolysis.

[0144] Preprocessing

[0145] The Spartina alterniflora was thoroughly washed with clean water to remove sand and impurities, and the washed raw materials were dried in a natural environment until the moisture content was less than 10%, and the dried raw materials were crushed into a particle size of less than 0.25 mm using an industrial crusher.

[0146] Pyrolysis: The pretreated Spartina alterniflora was sealed and stored in 2 cubic meters for 30 days to promote natural fermentation. Anaerobic pyrolysis was carried out under nitrogen atmosphere, with the pyrolysis temperature set at 550°C, the heating rate at 5°C / min, the holding time at 30min, and the nitrogen flow rate at 0.32 cubic meters / second.

[0147] Post-processing

[0148] After pyrolysis is completed, the biochar is naturally cooled to room temperature in a N2 atmosphere; it is sieved through a 40-mesh sieve to remove oversized particles, and finally the biochar is mixed with a 5% citric acid solution, and the pH is adjusted to 6.5 for use.

[0149] Experimental example

[0150] The biochar prepared in Example 1 and Comparative Example 1 was used for nitrogen and phosphorus removal:

[0151] Experimental conditions:

[0152] Biochar dosage: 0.5 g / L. Accurately weigh the biochar according to the volume of the experimental water sample.

[0153] Hydraulic retention time: 24 hours, to ensure that the water sample stays in the experimental device for a sufficient time so that the biochar can fully react with the pollutants in the water.

[0154] Stirring speed: 200 rpm to ensure that the biochar particles are evenly distributed in the water sample and improve the contact efficiency.

[0155] Other data:

[0156] Water sample volume: 5L.

[0157] Experimental repeatability: To ensure the reliability of the experimental results, each experimental condition was repeated 3 times.

[0158] Data recording: Record all parameters during the experiment in detail, including stirring speed, pH value, dissolved oxygen concentration, temperature, etc.

[0159] Experimental steps:

[0160] Before starting the experiment, the biochar was accurately weighed and added to the water sample; the water sample was stirred at a set stirring speed to ensure that the biochar was evenly distributed; after the experiment, the water sample was filtered through a filter and funnel to remove the biochar particles.

[0161] Testing of water indicators before and after treatment:

[0162] Total Nitrogen (TN):

[0163] The alkaline potassium persulfate digestion ultraviolet spectrophotometry (HJ 636-2012) was used to calculate the total nitrogen content by measuring the absorption intensity of the water sample in the ultraviolet region.

[0164] Total Phosphorus (TP):

[0165] The total phosphorus content was calculated by measuring the absorbance of the water sample at a specific wavelength using the ammonium molybdate spectrophotometry method (GB 11893-89).

[0166] pH: Use a pH meter to directly measure the pH of a water sample.

[0167] Dissolved oxygen (DO): The concentration of dissolved oxygen in the water sample is measured using an electrochemical probe method using a portable dissolved oxygen meter.

[0168] Evaluation of nitrogen and phosphorus removal efficiency

[0169] By comparing the nitrogen and phosphorus concentrations in the water before and after adding biochar, the denitrification and phosphorus removal efficiency is calculated:

[0170] Denitrification efficiency = (TN 处理前 -TN 处理后 ) / TN 处理前 ×100%

[0171] Phosphorus removal efficiency = (TP 处理前 -TP 处理后 ) / TP 处理前 ×100%

[0172] In the embodiment of the present invention, the water properties before treatment are: total nitrogen (TN) 30.5 mg / L, total phosphorus (TP) 3.8 mg / L, dissolved oxygen (DO) 4.5 mg / L, pH 7.2.

[0173] The water properties after treatment are shown in Table 1:

[0174] Table 1 Test results of water properties after treatment

[0175]

[0176] The evaluation results of nitrogen removal and phosphorus removal efficiency are shown in Table 2 below:

[0177] Table 2 Evaluation results of nitrogen removal and phosphorus removal efficiency

[0178]

[0179]

[0180] ANOVA

[0181] Total nitrogen (TN): F (1,18) = 18.34, p = 0.001

[0182] Total phosphorus (TP): F (1,18) = 25.67, p = 0.0001

[0183] The results of significance analysis showed that: total nitrogen (TN) was significantly different between Example 1 and Comparative Example 1 at a significance level of 0.05. Total phosphorus (TP) was significantly different between Example 1 and Comparative Example 1 at a significance level of 0.05.

[0184] Total nitrogen (TN): The average denitrification efficiency of Example 1 is 90.0%, and that of Comparative Example 1 is 59.1%. Variance analysis shows that there is a significant difference between the two, indicating that the biochar treatment effect of Example 1 is better.

[0185] Total phosphorus (TP): The average phosphorus removal efficiency of Example 1 was 92.1%, while that of Comparative Example 1 was 71.1%. The variance analysis showed a significant difference between the two, indicating that the biochar treatment of Example 1 was also more effective in phosphorus removal.

[0186] It can be seen from the above results that the biochar prepared in Example 1 of the present invention shows higher efficiency in nitrogen and phosphorus removal. By optimizing the mixing ratio of raw materials and pyrolysis conditions, the pore structure and surface functional groups of biochar are improved, thereby enhancing its adsorption capacity for pollutants such as nitrogen and phosphorus. It has significant advantages in practical applications and provides new ideas and methods for water pollution control.

[0187] 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 preparing Spartina alterniflora biochar, characterized in that: The following steps are involved: The Spartina alterniflora is mixed with auxiliary materials, and subjected to pyrolysis treatment after natural fermentation to obtain Spartina alterniflora biochar; The auxiliary materials contain wheat straw, corn stalk and bentonite.

2. The preparation method according to claim 1, characterized in that: In terms of weight, the amount of the Spartina alterniflora is 40 to 60 parts, the amount of the wheat straw is 20 to 40 parts, the amount of the corn stalk is 10 to 20 parts, and the amount of the bentonite is 3 to 8 parts.

3. The preparation method according to claim 1, characterized in that: The volume of the naturally fermented material is more than 1 cubic meter.

4. The preparation method according to claim 3, characterized in that: The natural fermentation time is 20 to 40 days.

5. The preparation method according to claim 1, characterized in that: The Spartina alterniflora is crushed before application, and the crushed particle size is less than 0.5 mm.

6. The preparation method according to claim 1, characterized in that: In the pyrolysis treatment, the pyrolysis temperature is 500-700°C; In the pyrolysis treatment, the heating rate is 5 to 10°C / min; In the pyrolysis treatment, the heat preservation time is 20 to 50 minutes.

7. The preparation method according to claim 6, characterized in that: The pyrolysis treatment is carried out in a nitrogen atmosphere, and the nitrogen flow rate is 0.3-0.5 m 3 / s.

8. The preparation method according to claim 1, characterized in that: The biochar further comprises adjusting the pH to 6.5 to 7.0; The pH adjustment uses citric acid solution as a regulator, and the concentration of the citric acid solution is 3-5%.

9. Spartina alterniflora biochar prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the Spartina alterniflora biochar according to claim 9 in denitrification and phosphorus removal from water bodies.

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