Preparation method of composite biochar material for removing intracellular and extracellular algal toxins in water body

Abstract

The invention belongs to the technical field of water bloom algae substance treatment and resource utilization, and discloses a preparation method of a composite biochar material for removing intracellular and extracellular algal toxins of a water body, and the preparation method comprises the following steps: S1, pretreatment of bottom mud; s2, pretreatment of water bloom algae mud; s3, preparing a bottom mud / algae mud composite biochar material; s4, preparation of a ZnO-AD composite biochar material; and S5, preparation of the M-ZnO-AD composite biochar material. According to the method, the river and lake bottom mud and the algal bloom mud are used as raw materials, the composite biochar material is prepared through a one-step pyrolysis method, and the one-step pyrolysis method is simple and controllable in process, low in pyrolysis temperature, low in energy consumption and capable of decomposing toxic substances and removing intracellular algal toxins; the prepared composite biochar material has abundant surface functional groups, can adsorb and degrade extracellular algal toxins in water, and realizes resource utilization of solid wastes of bottom mud and algae mud.

Description

Technical Field

[0001] The present invention relates to the technical field of treatment and resource utilization of bloom algal substances, and specifically to a preparation method of a composite biochar material for removing intracellular and extracellular microcystins in water bodies. Background Technique

[0002] With the rapid development of industry and agriculture in China, a large amount of industrial wastewater, domestic sewage and agricultural non-point source sewage containing nitrogen and phosphorus are discharged into rivers, lakes and seas, resulting in an increasingly serious eutrophication phenomenon in environmental water bodies. The eutrophication of water bodies often leads to the overgrowth of algae in the water bodies, especially the outbreak of planktonic algae (mainly cyanobacteria) to form water blooms. When the cyanobacterial bloom is severe, a thick layer of blue-green lake indigo forms on the water surface, emitting an unpleasant smell. It not only destroys the healthy and balanced aquatic ecosystem, but also a large number of cyanotoxins, odor substances and other toxic and harmful substances will be released after the accumulated algal cells die, triggering various derivative pollutions, posing a serious threat to the water ecosystem and public health safety.

[0003] The harmless treatment and resource utilization of bloom algal sludge face severe challenges. At present, the resource utilization technologies of bloom algal sludge mainly include the extraction of useful substances (such as natural pigments, algal proteins, extracellular polysaccharides, etc.). However, this technology is limited to single algal species. The types of algae in actual water bodies are complex and large in scale, and it is impossible to extract target substances with high purity, lacking practical operability. Another resource utilization method is to generate biogas by composting bloom algal sludge, etc. However, the water content of algal sludge is relatively high, and high-intensity dehydration is required before composting, with high energy consumption. In addition, the microcystins produced by cyanobacteria have a stable structure, are resistant to acids and alkalis and heat, and cannot be completely degraded even by heating at 300 °C. The above two resource utilization methods cannot effectively remove microcystins, increasing the difficulty of harmless treatment and resource utilization of bloom algal sludge.

[0004] Microcystins exist inside algal cells and are only released into the water body when the algal cells die or rupture. When the algal cells dissolve or die, they will enter the environmental water body. They are extremely stable in nature, are not easily chemically hydrolyzed or oxidized under environmental conditions, and can remain in the dark environment for several months to several years. Traditional water purification technologies have low removal efficiency for microcystins and are difficult to meet the standards of microcystin content in drinking water stipulated by the World Health Organization and China (MC-LR ≤ 1.0 μg / L); in addition, for eutrophic water bodies, the removal of microcystins mainly includes two parts, namely the removal of intracellular microcystins (algae removal) and extracellular (dissolved) microcystins. At present, most treatment measures are based on algae removal and ignore extracellular microcystins. Sometimes, some algae-killing measures only kill algal cells, but instead promote the release of microcystins in algal cells into the water body, resulting in the danger of safety in the treatment measures themselves. Therefore, finding an efficient method for removing intracellular and extracellular microcystins has become an urgent problem to be solved currently. Summary of the invention

[0005] The present invention aims to provide a method for preparing a composite biochar material for removing extracellular and extracellular algal toxins in water bodies. The composite biochar material is prepared by a one-step pyrolysis method using river and lake sediments and water bloom algal mud as raw materials. The one-step pyrolysis method has a simple and controllable process, a low pyrolysis temperature, and low energy consumption. It can decompose toxic substances and remove intracellular algal toxins. The prepared composite biochar material has rich surface functional groups and can adsorb and degrade extracellular algal toxins in water bodies, thereby realizing the resource utilization of solid waste of sediments and algal mud.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] A method for preparing a composite biochar material for removing intracellular and extracellular algae toxins in water comprises the following steps:

[0008] S1. Pretreatment of sediment: Take sediment from natural water bodies, soak and wash it with distilled water, separate and remove scum, dehydrate and dry it, grind it, and sieve it to obtain dry sediment;

[0009] S2. Pretreatment of algae bloom mud: taking the salvaged algae bloom mud, letting it stand, centrifuging the lower sediment, washing the lower algae mud with distilled water, and vacuum freeze-drying to obtain dry algae mud powder;

[0010] S3, preparation of sludge / algae mud composite biochar material: take the sludge obtained in S1 and the algae mud powder obtained in S2 in proportion, mix and grind them thoroughly, add deionized water, and disperse them by ultrasonic to obtain a stable suspension; stir the suspension, filter it with suction, dry it, and then calcine it and cool it to room temperature, and then wash it, filter it with suction, dry it, and grind it evenly to obtain the sludge / algae composite biochar material AD;

[0011] S4. Preparation of ZnO-AD: Add water and ethanol to zinc nitrate, add AD after ultrasonic stirring, and add ammonia ethanol dilution dropwise, heat and stir, wash with distilled water and ethanol to remove unreacted substances; recover the solid phase by centrifugation, calcine the solid phase in a tube furnace, and obtain ZnO-AD after cooling and grinding;

[0012] S5. Preparation of M-ZnO-AD: Dissolve FeCl3·6H2O in ethylene glycol and stir until uniform and transparent. Add NaAc under magnetic stirring, and add ZnO-AD while stirring. After reacting at a preset temperature, cool naturally to room temperature, collect the black precipitate, rinse with deionized water, dry and grind to obtain M-ZnO-AD.

[0013] Further, in S1, the mixture is washed by distilled water for 10 hours to 20 hours, and then dried at 45° C. to 55° C. after dehydration.

[0014] Further, in S2, centrifuge for 10 min - 20 min under the condition of 2000 r / min - 3000 r / min.

[0015] Further, in S3, the mass ratio of the sediment obtained in S1 to the algal sludge powder obtained in S2 is: 25% - 35%: 65% - 75%.

[0016] Further, in S3, the calcination process is as follows: After stirring, suction filtration, and drying the suspension, calcine in a tube furnace at 380°C - 420°C for 2 h - 3 h under an Ar atmosphere, with a heating rate of 5°C / min - 6°C / min.

[0017] Further, in S4, the mass ratio of zinc nitrate to AD is: 29 - 31: 19 - 21; water and ethanol are added to zinc nitrate, and the volume ratio of water to ethanol is: 2 - 3: 7 - 8; in the ethanol-diluted ammonia water, the volume ratio of ethanol to ammonia water is: 5:2.

[0018] Further, in S4, the calcination process is as follows: Place the solid phase in a tube furnace and calcine at 380°C - 420°C for 2 h - 3 h under an Ar atmosphere, with a heating rate of 5°C / min - 6°C / min.

[0019] Further, in S4, the mass ratio of FeCl3·6H2O, NaAc, and ZnO-AD is: 29 - 31: 36 - 44: 28 - 32.

[0020] Further, in S4, the preset temperature is 198°C - 202°C, and the reaction time is 8 h - 9 h; rinse with deionized water multiple times until the pH value is 6.8 - 7.2.

[0021] The beneficial effects of the technical solution are:

[0022] 1. The present invention uses bloom algal sludge and river-lake bottom sludge as raw materials to prepare a composite biochar material through a one-step pyrolysis method. The one-step pyrolysis method has a simple and controllable process, a low pyrolysis temperature (400 °C), low energy consumption, can decompose toxic substances, and remove intracellular algal toxins. Moreover, the composite biochar material has good adsorption performance, and on this basis, it is functionally modified by loading ZnO and negative magnetization to optimize the internal structure and optoelectronic properties, having high-efficiency photocatalytic degradation performance and being rich in magnetism, which is convenient for recycling and reuse. The multifunctional composite biochar material (M-ZnO-AD, where M represents magnetism and AD represents the bottom sludge / algal sludge composite biochar material) combines adsorption and photocatalytic degradation performance, realizes the resource utilization of solid waste from bottom sludge and algal sludge. The multifunctional composite material has both adsorption and photocatalytic functions, can be applied to the removal of algal toxins in eutrophic water bodies, and has great application potential in removing heavy metals in water bodies and reducing nitrogen and phosphorus. Especially, it can be applied to complex water environments to achieve the integrated removal of multiple pollutants. And the present invention uses algal sludge as a raw material to prepare a multifunctional composite material through pyrolysis, without the need to obtain other raw materials additionally, reducing the production and manufacturing cost, can effectively decompose the algal toxins not released into the water body, not only solves the problem of resource disposal of bloom algal sludge, avoids secondary pollution caused by algal toxins in algal sludge, but also can remove algal toxins in water bodies, achieving waste treatment with waste and reaching a win-win goal.

[0023] 2. The present invention uses river-lake bottom sludge and bloom algal sludge as raw materials to prepare a bottom sludge / algal sludge composite biochar material, optimizes its performance and surface properties through modification. Toxic substances can be decomposed during the preparation process. The obtained composite biochar material (M-ZnO-AD) has rich functional groups and combines adsorption and degradation performance, can be used for the removal of extracellular algal toxins in water bodies, and the used material decomposes toxic substances through high-temperature pyrolysis to achieve recycling and is environmentally friendly.

[0024] 3. Starting from resource utilization, the main raw material sources of the prepared composite biochar material of the present invention are rich, low-cost and easy to obtain.

[0025] 4. During the preparation process of the present invention, by fully grinding the mixture, not only can the mixture be fully and evenly mixed, but also the algal cell walls can be broken, saving the energy consumption required for pyrolysis.

[0026] 5. On the one hand, the present invention solves the problem of resource utilization of river-lake bottom sludge and water bloom algae. On the other hand, by adjusting the material ratio, the content of organic carbon in the raw materials under different natural environments can be regulated, and the application range is wide. Description of the Drawings

[0027] Figure 1 SEM image of the M-ZnO-AD composite biochar material prepared by the preparation method of the present invention;

[0028] Figure 2 TEM of the M-ZnO-AD composite biochar material prepared by the preparation method of the present invention Figure 1 ;

[0029] Figure 3 TEM of the M-ZnO-AD composite biochar material prepared by the preparation method of the present invention Figure 2 ;

[0030] Figure 4 XPS energy spectrum and high-resolution elemental energy spectrum of the M-ZnO-AD composite biochar material prepared by the preparation method of the present invention; in the figure, (a) is the XPS energy spectrum of the M-ZnO-AD composite biochar material, (b) is the fine energy spectrum of the C1s region, (c) is the fine energy spectrum of the N1s region, and (d) is the fine energy spectrum of the Fe 2p region;

[0031] Figure 5 Transient photocurrent response diagrams of different composite biochar materials;

[0032] Figure 6 EIS diagrams of different composite biochar materials;

[0033] Figure 7 Effect of pH on the removal of microcystins by the composite material;

[0034] Figure 8 Effect of different catalyst dosages on the removal rate and removal amount of microcystins. Detailed implementation manners

[0035] The present invention will be further described in detail below with reference to the drawings and embodiments:

[0036] In the related art, algal sludge biochar is a biochar material prepared by steps such as dehydration, crushing, drying, granulation, shaping, and carbonization of algal sludge. Algae are rich in organic matter and have a high carbon content. The biochar obtained after pyrolysis has less ash content, and algae have a relatively small molecular weight. The particle size of the prepared biochar is much smaller than that of biochar materials such as crop straws. Algal sludge biochar has porosity and a high specific surface area, and can be used as a biomass energy source, soil conditioner, sewage treatment agent, etc. for the removal of organic matter and heavy metals in the environment. At the same time, pyrolysis can destroy most microorganisms and toxic substances. Through functional modification, the original biochar can be improved or endowed with new properties. Among them, the composite modification technology has low cost and simple technology, and has great potential application value in the field of environmental pollution control and ecological restoration. At present, most of the research focuses on the preparation and modification of single-algae biochar, and there are very limited reports on water bloom algal sludge composite biochar materials.

[0037] The invention provides a preparation method of a composite biochar material for removing intracellular and extracellular algae toxins in water bodies. The composite biochar material is prepared by a one-step pyrolysis method using algae bloom mud and river and lake bottom mud as raw materials. The composite biochar material has good adsorption performance, and functional modification is performed on this basis. ZnO is loaded and negative magnetism is used to optimize the internal structure and photoelectric properties. The composite biochar material has efficient photocatalytic degradation performance, is rich in magnetism, and is easy to recycle and reuse. The multifunctional composite biochar material (M-ZnO-AD: wherein M represents magnetism, and AD represents bottom mud / algae mud composite biochar material) has both adsorption and photocatalytic degradation performance in terms of function, realizes the resource utilization of solid wastes of bottom mud and algae mud, and the multifunctional composite material has both adsorption and photocatalytic functions, can be applied to the removal of algae toxins in eutrophic water bodies, and has both adsorption and photocatalytic functions, and has great application potential in removing heavy metals in water bodies and reducing nitrogen and phosphorus, and can be applied to complex water environments to realize the integrated removal of multiple pollutants. The current algal toxin removal methods cannot effectively remove intracellular algal toxins. The present invention uses algal mud as raw material to prepare a multifunctional composite material through pyrolysis. It does not require additional raw materials, reduces production costs, and can effectively decompose algal toxins that are not released into the water body. It not only solves the problem of resource disposal of water bloom algal mud and avoids secondary pollution caused by algal toxins in algal mud, but also provides new ideas and technologies for removing algal toxins in water bodies, realizing waste treatment with waste and achieving a win-win goal.

[0038] The specific steps are as follows:

[0039] S1. Pretreatment of sediment: Take 10g of surface sediment from natural water bodies, soak and wash with distilled water for 15h, separate and remove scum, repeat 4 times, dehydrate and dry at 50℃, grind, pass through 80-mesh sieve, and set aside;

[0040] S2. Pretreatment of algae bloom mud: Take 5L of salvaged algae bloom mud, let it stand for 24 hours, take the lower sediment, centrifuge it at 3000r / min for 15 minutes, wash the lower algae mud with distilled water 4 times, and freeze-dry it in vacuum to obtain dry algae mud powder;

[0041] S3, preparation of sludge / algae mud composite biochar material: take 1.5g of sludge obtained in S1 and 3.5g of algae mud powder obtained in step 2, mix and grind them thoroughly for 20min, add 60mL of deionized water, and ultrasonically disperse them for 20min to obtain a stable suspension; stir rapidly for 2h at 20℃, filter with suction, and dry the obtained product in a 60℃ oven; place the above reactants in a 400℃ tubular furnace, calcine for 3h under Ar atmosphere, and the heating rate is 5℃ / min; after calcination, cool to room temperature, wash with anhydrous ethanol and deionized water 4 times respectively, filter with suction, and dry at 50℃, grind evenly to obtain the sludge / algae composite biochar material after 80 mesh sieve;

[0042] S4. Preparation of ZnO-AD composite biochar material: Add 10 mL of water and 30 mL of ethanol to 3 g of zinc nitrate. After ultrasonic stirring until evenly mixed, add 2 g of AD and continue magnetic stirring for 30 min. Dilute 4 mL of ammonia water with 10 mL of ethanol and then add it dropwise to the above suspension. After the addition is complete, continue stirring for 20 min, then raise the temperature to 80 °C and stir for 2 h. Wash with distilled water and ethanol to remove unreacted substances. Centrifuge to recover the solid phase, place the solid phase in a tubular furnace, calcine at 400 °C for 3 h under an Ar atmosphere, heating rate: 5 °C / min. After cooling and grinding, the ZnO-AD composite biochar material is obtained.

[0043] S5. Preparation of M-ZnO-AD composite biochar material: Prepared by hydrothermal co-precipitation method. Dissolve 1.5 g of FeCl3·6H2O in 20 mL of ethylene glycol, stir vigorously until evenly transparent. Slowly add 2 g of NaAc under magnetic stirring and continue stirring for 20 min. While stirring, add 1.5 g of ZnO-AD. Transfer the suspension to a stainless steel autoclave and react at 200 °C for 8 h, then naturally cool to room temperature. Use a magnet to collect the black sediment and rinse it with deionized water multiple times until the pH value is 6.8 - 7.2. Dry and grind at 60 °C, and the obtained product is the M-ZnO-AD composite biochar material.

[0044] The surface morphology of the M-ZnO-AD composite biochar material was observed using a scanning electron microscope (SEM) and a scanning transmission electron microscope (TEM). The results are as Figures 1 to 3 shown. The surface of the composite biochar material is rough, forming larger cavities, with a rich wrinkled structure, and fine particles are closely dispersed in the cavity structure.

[0045] The chemical state of the surface elements of the composite biochar material was analyzed by X-ray photoelectron spectroscopy (XPS). The XPS spectrum and high-resolution elemental spectrum of M-ZnO-AD are as Figure 4As shown in the figure. The composite material is composed of C, N, O, Si, Al, and Fe, without other impurity elements. It can be seen from the high-resolution spectrum of the C1s region that the C1s spectrum line of the composite material can be decomposed into four fitting peaks. Their binding energies are 284.2 eV, 286.2 eV, 288.6 eV, and 289.3 eV, which are attributed to C-C bond / C=C bond, C-NHx (x = 1-2) bond, C-O\N=C-N bond, and O-C=O / O=C-N bond respectively. From the high-resolution spectrum of the N 1s region, it can be seen that the spectrum line of the M-ZnO-Ni-RD composite material can be decomposed into three fitting peaks. The binding energies of 399.2 eV, 399.9 eV, and 400.5 eV are attributed to C=N-C bond, N–(C)3 bond, and C-N-H bond respectively. From the high-resolution spectrum of the Fe 2p region, it can be seen that the spectrum line of the M-ZnO-Ni-RD composite material can be decomposed into 3 fitting peaks. Among them, the two peak centers at 713.5 eV and 725.4 eV correspond to Fe 2p1 / 2 and Fe2p3 / 2 respectively, and the energy difference between the Fe 2p3 / 2 and Fe 2p1 / 2 spin-orbit doublets is 11.9 eV, indicating the presence of Fe2O3 in the composite material. There is a Fe0 peak at the binding energy of 7106.2 eV, further confirming the formation of Fe0 on the surface of the M-ZnO-Ni-RD composite material. Fe0 has a large specific surface area, high surface activity, and a large capacity for removing pollutants. It can remove pollutants through various actions such as adsorption, reduction, and precipitation, but it is easy to react with water, resulting in passivation. By combining with the carrier biochar material, Fe0 is dispersed in the pore structure of the biochar, solving the problem of inactivation due to agglomeration; the surface functional groups of the biochar interact with Fe0, providing a medium and carrier for electron transfer. This force is relatively strong, enhancing the adsorption and degradation performance of the composite material for pollutants. Due to its typical core-shell structure, the internal Fe0 is wrapped by external oxides, and most of the Fe0 exists in the internal pore structure of the biochar, reducing iron spillage.

[0046] The generation and change of photocurrent of the composite material were observed under light and dark conditions, as Figure 5 shown. It can be observed that the change of "on" and "off" currents in a complete cycle shows almost vertical and rapid changes, meaning that charges are rapidly transported in the sample. The photocurrent signal of the M-ZnO-AD composite material is the strongest, indicating a large amount of photoelectron production, which is a performance possessed by excellent photocatalysts. Attributed to the close interaction and synergistic effect at the interface, the photoinduced electron-hole pairs are effectively separated, thus suppressing the recombination of photogenerated charges.

[0047] The impedance properties of the composite material were tested by the electrochemical impedance spectroscopy (EIS) of the photocatalyst. As Figure 6As shown, an arc can be observed in the EIS diagram of the material, indicating that the photocatalytic charge transfer reaction only occurs on the surface. The semicircle radius of the M-ZnO-AD composite material electrode is smaller than that of other catalysts, indicating that its AC impedance is the smallest. A small impedance can make the electron-hole separation on its surface easier, and the photo-generated electrons can be more easily conducted out, so that a higher photocatalytic efficiency can be obtained.

[0048] Performance optimization experiments were carried out on the multifunctional composite biochar material (M-ZnO-AD) prepared by the present invention and the existing algal toxin removal materials. Through single-factor experiments, the optimal reaction conditions of the multifunctional composite biochar material (M-ZnO-AD) were determined. Under the optimal reaction conditions, the photocatalytic degradation rate of the M-ZnO-AD composite biochar material for algal toxins was as high as over 99%, and the maximum removal amount was 9.909 mg / g. The research by Xia Wang et al. (2023) showed that the reaction equilibrium time was 120 min, the removal rate was 97%, and the removal amount was 0.485 mg / g (50 mg ZnO / g-C3N4, V = 50 mL, c0(MC-LR) = 500 μg / L). The composite material of the present invention requires less catalyst dosage and shorter time, about 55 min, in the application of algal toxin removal experiments.

[0049] The Bi2WO6 / Fe3O4 / RGO developed by Mingming Zhan et al. had an algal toxin removal rate of 79.3% and a removal amount of 3.965 mg / g under certain conditions (6 mg Bi2WO6 / Fe3O4 / RGO, V = 10 mL, c0(MC-LR) = 3 mg / L). The composite biochar material (M-ZnO-AD) of the present invention has a higher removal rate.

[0050] Among them, the influence of pH on the removal of algal toxins by the composite material and the influence of different catalyst dosages on the removal rate and removal amount of algal toxins are as Figure 7 and Figure 8 shown. Figure 7 shows the influence of pH on the removal of algal toxins by the composite material (reaction conditions: catalyst dosage 20 mg, system V = 20 mL, initial algal toxin concentration 10 mg / L, temperature 25 °C in the dark reaction stage, 300-watt xenon lamp (filter λ > 420 nm) in the photocatalytic stage); Figure 8 shows the influence of different catalyst dosages on the removal rate and removal amount of algal toxins (reaction conditions: pH 5.0, system V = 20 mL, initial algal toxin concentration 10 mg / L, temperature 25 °C in the dark reaction stage, 300-watt xenon lamp (filter λ > 420 nm) in the photocatalytic stage).

[0051] In summary, the present invention focuses on the removal of intracellular and extracellular algal toxins. It makes use of local materials, uses algal sludge as raw material to pyrolyze and remove intracellular algal toxins, uses the prepared materials to adsorb and degrade extracellular algal toxins, and the used materials can decompose toxic substances through high-temperature heating, realizing recycling and reflecting green chemistry.

[0052] The above are only embodiments of the present invention. Specific technical solutions or common knowledge such as characteristics well known in the art are not described in detail herein. It should be noted that for those skilled in the art, without departing from the technical solution of the present invention, several deformations and improvements can be made, which should also be regarded as the protection scope of the present invention, and these will not affect the implementation effect of the present invention and the practicality of the patent. The protection scope required by this application should be based on the content of its claims, and the specific implementation manners and the like recorded in the specification can be used to interpret the content of the claims.

Claims

1. A preparation method of a composite biochar material for removing intracellular and extracellular algal toxins in water bodies, characterized in that, The following steps are involved: S1. Pretreatment of sediment: Take sediment from natural water bodies, soak and wash it with distilled water, separate and remove scum, dehydrate and dry it, grind it, and sieve it to obtain dry sediment; S2. Pretreatment of algae bloom mud: taking the salvaged algae bloom mud, letting it stand, centrifuging the lower sediment, washing the lower algae mud with distilled water, and vacuum freeze-drying to obtain dry algae mud powder; S3, preparation of sludge / algae mud composite biochar material: take the sludge obtained in S1 and the algae mud powder obtained in S2 in proportion, mix and grind them thoroughly, add deionized water, and disperse them by ultrasonic to obtain a stable suspension; stir the suspension, filter it with suction, dry it, and then calcine it and cool it to room temperature, and then wash it, filter it with suction, dry it, and grind it evenly to obtain the sludge / algae composite biochar material AD; S4. Preparation of ZnO-AD: Add water and ethanol to zinc nitrate, add AD after ultrasonic stirring, and add ammonia ethanol dilution dropwise, heat and stir, wash with distilled water and ethanol to remove unreacted substances; recover the solid phase by centrifugation, calcine the solid phase in a tube furnace, and obtain ZnO-AD after cooling and grinding; S5. Preparation of M-ZnO-AD: Dissolve FeCl3·6H2O in ethylene glycol and stir until uniform and transparent. Add NaAc under magnetic stirring, and add ZnO-AD while stirring. After reacting at a preset temperature, cool naturally to room temperature, collect the black precipitate, rinse with deionized water, dry and grind to obtain M-ZnO-AD.

2. The preparation method of the composite biochar material for removing intracellular and extracellular algal toxins from water bodies according to claim 1, characterized in that: In S1, the product is soaked and washed in distilled water for 10 h to 20 h; and then dried at 45° C. to 55° C. after dehydration.

3. The preparation method of the composite biochar material for removing intracellular and extracellular algal toxins in water bodies according to claim 1, wherein: In S2, centrifuge at 2000 r / min-3000 r / min for 10 min-20 min.

4. The preparation method of the composite biochar material for removing intracellular and extracellular algal toxins from water bodies according to claim 1, characterized in that: In S3, the mass ratio of the bottom mud obtained in S1 to the algae mud powder obtained in S2 is: 25%-35%: 65%-75%.

5. The preparation method of the composite biochar material for removing intracellular and extracellular algal toxins in water bodies according to claim 1, characterized in that: In S3, the calcination process is as follows: after the suspension is stirred, filtered and dried, it is calcined in a tubular furnace at 380°C-420°C under Ar atmosphere for 2h-3h with a heating rate of 5°C / min-6°C / min.

6. The preparation method of the composite biochar material for removing intracellular and extracellular algal toxins from water bodies according to claim 1, wherein: In S4, the mass ratio of zinc nitrate to AD is 29-31:19-21; water and ethanol are added to zinc nitrate, and the volume ratio of water to ethanol is 2-3:7-8; in the ethanol dilution of ammonia water, the volume ratio of ethanol to ammonia water is 5:

2.

7. The preparation method of the composite biochar material for removing intracellular and extracellular algal toxins in water bodies according to claim 1, characterized in that: In S4, the calcination process is: placing the solid phase in a tubular furnace, calcining at 380°C-420°C for 2h-3h under Ar atmosphere, with a heating rate of 5°C / min-6°C / min.

8. The preparation method of the composite biochar material for removing intracellular and extracellular algal toxins from water bodies according to claim 1, characterized in that: In S4, the mass ratio of FeCl3·6H2O, NaAc, and ZnO-AD is: 29~31: 36~44: 28~32.

9. The preparation method of the composite biochar material for removing intracellular and extracellular algal toxins in water bodies according to claim 1, characterized in that: In S4, the preset temperature is 198°C-202°C, the reaction time is 8h-9h; and the mixture is rinsed with deionized water for multiple times until the pH value is 6.8-7.2.

Images