High-adsorption-performance environment-friendly seaweed carbon material and preparation method thereof

Abstract

The invention belongs to the technical field of environment functional materials, and particularly relates to a high-adsorption-performance environment-friendly seaweed carbon material and a preparation method thereof. In order to pursue high specific surface area and adsorption performance, seaweed biochar depends on strong acid, strong alkali or heavy metal salt for chemical activation, and a large amount of acid-alkali wastewater and secondary pollution are generated. Through a molecular bridging soft and hard template cooperation strategy, firstly, seaweed meal is mixed with bridging molecules and a functional metal salt solution, so that metal ions are dispersed in a molecular level and are firmly combined; blending and molding with a soft template agent and a hard template; synchronous carbonization and activation are realized through one-step controllable pyrolysis, and finally, a hard template is removed through etching, so that high adsorption capacity and selectivity on heavy metal ions and organic pollutants are realized.

Description

Technical Field

[0001] This invention belongs to the field of environmental functional materials technology, specifically relating to a high-adsorption-performance environmentally friendly seaweed char material and its preparation method. Background Technology

[0002] With the rapid development of industrialization and urbanization, adsorption methods have become an important technical means for water pollution control due to their advantages such as simple operation, low cost, and high efficiency. Biochar, as a novel carbonaceous adsorbent material, has attracted widespread attention due to its wide availability, simple preparation, and environmental friendliness. Seaweed, as a renewable marine resource, is rich in polysaccharides, proteins, and inorganic salts, making it an excellent raw material for biochar preparation (CN112174109A). Seaweed biochar not only inherits the general characteristics of biochar but also possesses abundant surface functional groups due to its unique chemical composition, showing promising application prospects in the field of environmental remediation.

[0003] However, traditional methods for preparing seaweed biochar have the following prominent problems:

[0004] (1) Pore structure is underdeveloped: seaweed biochar prepared by direct pyrolysis usually has a simple pore structure, mainly micropores, lacking mesopores and macropores, resulting in limited specific surface area, large mass transfer resistance, slow adsorption kinetics, and difficulty in meeting the requirements of efficient adsorption.

[0005] (2) Insufficient surface active sites: The surface functional groups of unmodified seaweed biochar have low density and uneven distribution, resulting in limited adsorption capacity and selectivity for specific pollutants, making it difficult to achieve efficient removal of target pollutants.

[0006] (3) Environmental problems caused by chemical activation: In order to improve the specific surface area and adsorption performance of biochar, existing technologies usually use strong acids, strong bases or heavy metal salts for chemical activation treatment. Although these methods can effectively improve the pore structure, they generate a large amount of acid and alkaline wastewater, increase the environmental burden, and the residual activator may cause secondary pollution.

[0007] In conclusion, developing an environmentally friendly, highly controllable method for preparing seaweed biochar that can simultaneously achieve hierarchical porous structures and precise construction of high-density active sites is of great significance for promoting the practical application of biochar materials in the field of environmental governance. Summary of the Invention

[0008] This invention provides a high-adsorption-performance environmentally friendly seaweed char material and its preparation method. Through molecular bridging technology and a hard-soft dual-template synergistic strategy, the hierarchical porous structure and high-density active sites of seaweed biochar are precisely constructed. The prepared seaweed char material has excellent adsorption performance and environmentally friendly characteristics.

[0009] The specific technical solution is as follows: A highly adsorption-performance environmentally friendly seaweed charcoal material and its preparation method are as follows: S1: Raw material pretreatment and molecular bridging.

[0010] S11: Add dried seaweed powder to deionized water, stir, and ultrasonically disperse to obtain seaweed suspension.

[0011] S12: Add the bridging molecule solution to the seaweed suspension prepared in S11, stir, then add the functional metal salt, and continue stirring to obtain the chelated solution.

[0012] S13: Add the soft template agent to the chelation solution prepared in S12, stir, and obtain the seaweed composite slurry.

[0013] S2: Hard template composite and molding. Monodisperse mesoporous silica nanospheres are added to the seaweed composite slurry prepared in S13, stirred until there are no dry powder lumps, ball-milled, hydraulically molded, and dried to obtain a dry green body that can be used for pyrolysis.

[0014] S3: Pyrolysis and activation. The dried green body prepared in S2 is placed in a sealed furnace, the air is replaced, the temperature is gradually increased for pyrolysis, and then it is naturally cooled to room temperature to obtain the carbonized composite material.

[0015] S4: Post-processing: The carbonized composite material prepared in S3 is added to the etching solution for etching, stirred, naturally cooled to room temperature, vacuum filtered, washed, and dried to obtain environmentally friendly seaweed carbon material with high adsorption performance.

[0016] Furthermore, the seaweed powder described in S11 has a mass-to-volume ratio of 1:10 to deionized water.

[0017] The ultrasonic dispersion described in S11 has the following parameter settings: power 300W, frequency 40kHz, duration 30min.

[0018] The bridging molecule solution described in S12 has a bridging molecule that is one of polyethyleneimine, chitosan, or polyacrylamide, and the mass ratio of the bridging molecule to seaweed powder is 1:20 to 6:20.

[0019] The stirring described in S12 has the following parameters: temperature 40-50℃, duration 2-3h, and speed 200-400rpm.

[0020] The functional metal salt mentioned in S12 is one or more of magnesium chloride, lanthanum chloride, ferric chloride, and calcium nitrate, and its mass ratio with seaweed powder is 1:10 to 1:40.

[0021] The soft template agent mentioned in S13 is one of urea and ammonium citrate, and its mass ratio with seaweed powder is 1:3 to 1:10.

[0022] The stirring described in S13 has the following parameters: temperature 30℃, duration 1-2h, and speed 200-400rpm.

[0023] Furthermore, the monodisperse mesoporous silica nanospheres described in S2 have a mass ratio of 1:1 to 1.5:1 with the seaweed powder.

[0024] The ball mill described in S2 has the following parameter settings: using zirconia balls as the grinding medium, a ball-to-material ratio of 4:1, a rotation speed of 200-300 rpm, and a duration of 4-6 hours.

[0025] The hydraulic forming described in S2 has the following parameter settings: pressure 10-30 MPa, duration 1-3 min.

[0026] The drying process described in S2 has the following parameters: temperature 60–80°C, duration 12–24 hours.

[0027] Furthermore, in the gradient heating pyrolysis described in S3, nitrogen gas is continuously introduced, and the parameters are set as follows: heating rate of 1-5℃ / min, temperature of 250-350℃, duration of 30-120min in the low-temperature stage, heating rate of 2-6℃ / min, temperature of 500-700℃, duration of 60-180min in the high-temperature carbonization stage.

[0028] Furthermore, the etching solution described in S4 is a sodium hydroxide solution of 0.5–2 mol / L.

[0029] The etching described in S4 has the following parameters: temperature 200-300℃, pressure 2-4MPa, and duration 6-10h.

[0030] The drying process described in S4 has the following parameters: temperature 105–120°C, duration 12–24 hours.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] 1. This invention ensures uniform dispersion of functional metal components through a molecular bridging strategy, avoids agglomeration, and improves the utilization efficiency and adsorption performance of active sites.

[0033] 2. This invention uses soft and hard templates to create pores. The soft template decomposes and creates micropores and some macropores, while the hard template constructs an ordered mesoporous framework, ultimately forming a connected hierarchical porous system, which improves specific surface area and mass transfer efficiency. Attached Figure Description

[0034] Figure 1 This is a process flow diagram for the preparation of a highly adsorption-performance, environmentally friendly seaweed charcoal material.

[0035] Figure 2These are SEM and TEM images of the morphological structure of the seaweed carbon material finally prepared in Example 1.

[0036] Figure 3 This is a comparison chart of the specific surface area and iodine adsorption value of the seaweed char materials finally prepared in Examples 1-4 and Comparative Examples 1-2. Detailed Implementation

[0037] The following embodiments further explain and illustrate the technical solutions of the present invention. It should be specifically noted that each specific embodiment is a concretization and explanation of the technical solution and should not be considered as a limitation on the scope of protection of the present invention. Those skilled in the art still have the right to modify the technical solutions of these embodiments and make equivalent substitutions for some or all of the technical features, and these modifications or substitutions do not change the essence of the corresponding technical solutions, nor do they cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions described in the present invention.

[0038] This invention proposes a high-adsorption-performance, environmentally friendly seaweed biochar material and its preparation method. Through molecular bridging technology and a synergistic strategy of hard and soft dual templates, the precise construction of a hierarchical porous structure and high-density active sites in the seaweed biochar is achieved. (See attached diagram) Figure 1 The diagram shows a method for preparing a highly adsorption-performance, environmentally friendly seaweed charcoal material. The detailed technical solution is as follows:

[0039] 1. Raw material pretreatment and molecular bridging Dry seaweed powder was added to deionized water, stirred, and ultrasonically dispersed to obtain a seaweed suspension. A bridging molecule solution was added to the seaweed suspension, stirred, then a functional metal salt was added, and stirring continued. Finally, a soft template agent was added and stirred to obtain a seaweed composite slurry.

[0040] After being dispersed in water, the abundant hydrophilic groups such as hydroxyl and carboxyl groups on the surface of seaweed powder are activated, providing adsorption sites for subsequent molecules. Bridging molecules preferentially adsorb onto the seaweed surface and internal pores through electrostatic interactions, hydrogen bonds, or van der Waals forces. Simultaneously, these bridging molecules contain numerous amino and imine coordination groups, which strongly chelate subsequently added functional metal ions, forming a stable metal-organic coordination structure. This effectively prevents uneven precipitation or aggregation of metal ions in subsequent processes, ensuring their highly dispersed state. The finally added soft template agent is uniformly dispersed in the system under stirring, and some is adsorbed onto the surface or interstices of the formed seaweed-bridging molecule-metal complex. It decomposes and produces gas during the subsequent pyrolysis stage, acting as a "pore-forming agent" for micropores and some macropores.

[0041] 2. Rigid template composite and molding Monodisperse mesoporous silica nanospheres were added to seaweed composite slurry and stirred until no dry powder lumps were formed. The mixture was then ball-milled, hydraulically molded, and dried to obtain a dry green body suitable for pyrolysis.

[0042] Monodisperse mesoporous silica nanospheres serve as hard templates, possessing uniform particle size and internal mesoporous channels. When these nanospheres are uniformly dispersed and blended with the composite slurry, each silica sphere and the gaps created by its accumulation spatially "occupy" a region that will become a cavity in the future. Under mechanical force, the seaweed composite slurry fully fills all the gaps between the hard template particles and coats the surface of each hard template particle, forming a bicontinuous phase structure where the "seaweed composite-hard template" interpenetrates.

[0043] 3. Pyrolysis and Activation The dried green body is placed in a sealed furnace, the air is replaced, the temperature is gradually increased for pyrolysis, and then it is naturally cooled to room temperature to obtain a carbonized composite material.

[0044] In the low-temperature stage, the soft template agent first undergoes thermal decomposition, releasing a large amount of gas that expands and escapes within the not-yet-fully-carbonized, plastic seaweed-bridging molecule composite matrix. This pre-etches abundant micropores and an initial pore network into the material, achieving physical pore creation. Simultaneously, the bridging molecules undergo dehydration, cross-linking, and solidification reactions with polysaccharides and proteins in the seaweed biomass, forming a preliminary stable nitrogen-containing organic framework. This framework also "anchors" chelated metal ions, preventing their migration and aggregation at subsequent high temperatures. In the high-temperature carbonization stage, the seaweed biomass undergoes deep carbonization, further removing volatile components and forming a basic carbon framework dominated by graphite microcrystals. The bridging molecules themselves undergo pyrolysis, with their nitrogen-containing structural components being converted into nitrogen atoms that are doped into the carbon framework, significantly enhancing the surface polarity, electronic conductivity, and binding ability of the carbon material to pollutants. Simultaneously, the chelated functional metal ions are reduced in a reducing pyrolysis atmosphere, generating highly dispersed nanoscale metal oxides or metal oxide nanoclusters. These are firmly embedded or loaded onto the carbon framework, becoming highly active adsorption sites for specific pollutants. The entire process is completed in a continuous temperature-programmed manner, without the need for any external chemical activators. By precisely controlling the heating rate, the temperature at each stage, and the holding time, the synergistic rhythm of soft template decomposition and biomass carbonization, the intensity of gas release, and the nitrogen / metal conversion state can be regulated, thereby achieving precise control over the final material's pore structure, surface chemistry, and active site distribution.

[0045] 4. Post-processing The carbonized composite material was added to the etching solution for etching, stirred, naturally cooled to room temperature, vacuum filtered, washed, and dried to obtain a highly adsorption-performance environmentally friendly seaweed carbon material.

[0046] The silica hard template can dissolve under alkaline conditions, and the resulting sodium silicate is soluble in water. However, the nitrogen-doped carbon framework and embedded metal oxide / elemental nanoclusters formed by high-temperature pyrolysis are chemically stable in alkaline solutions and will not be destroyed. The template can be removed while retaining the functional host.

[0047] After the silica spheres are removed, the gaps between their own accumulation form macropores (>50nm); after the hard template particles are removed, they will form mesopores (2-50nm) with uniform size; the slurry matrix, which is uniformly dispersed in the hard template gaps, will decompose during pyrolysis, generating abundant micropores (<2nm) inside and on the surface of the mesoporous framework. The three combine to form a hierarchical porous network of "micropore-mesopore-macropore".

[0048] Example 1 A highly adsorption-performance environmentally friendly seaweed charcoal material and its preparation method are as follows: Table 1 Main Raw Materials

[0049] S1: Raw material pretreatment and molecular bridging.

[0050] S11: Add 100g of dried seaweed powder to 1000mL of deionized water, stir, and ultrasonically disperse to obtain a seaweed suspension. The ultrasonic dispersion parameters were set as follows: power 300W, frequency 40kHz, and duration 30min.

[0051] S12: Add the polyethyleneimine solution to the seaweed suspension prepared in S11, stir, then add magnesium chloride and lanthanum chloride, and continue stirring to obtain a chelated solution. The stirring parameters were set as follows: temperature 45℃, duration 2.5h, rotation speed 300rpm; the mass ratio of polyethyleneimine to seaweed powder was 3:20; the mass ratio of magnesium chloride and lanthanum chloride was 1:1, and the mass ratio of both to seaweed powder was 1:25.

[0052] S13: Add urea to the chelation solution prepared in S12 and stir to obtain seaweed composite slurry. The mass ratio of urea to seaweed powder is 1:7; stirring parameters are set as follows: temperature 30℃, duration 1.5h, and speed 300rpm.

[0053] S2: Hard template composite and molding. Monodisperse mesoporous silica nanospheres were added to the seaweed composite slurry prepared in S13, stirred until no dry powder lumps remained, ball-milled, hydraulically molded, and dried to obtain a dried green body suitable for pyrolysis. The mass ratio of monodisperse mesoporous silica nanospheres to seaweed powder was 1.25:1. The ball-milling parameters were: zirconia balls as the grinding medium, ball-to-material ratio 4:1, rotation speed 250 rpm, duration 5 h; the hydraulic molding parameters were: pressure 20 MPa, duration 2 min; and the drying parameters were: temperature 70℃, duration 18 h.

[0054] S3: Pyrolysis and activation. The dried green body prepared in S2 is placed in a sealed furnace, the air is replaced, and pyrolysis is performed by gradient heating. After natural cooling to room temperature, the carbonized composite material is obtained. In the gradient heating pyrolysis, nitrogen gas is continuously introduced. The parameters are set as follows: heating rate of 3℃ / min, temperature of 300℃, and duration of 75min in the low-temperature stage; heating rate of 4℃ / min, temperature of 600℃, and duration of 120min in the high-temperature carbonization stage.

[0055] S4: Post-treatment. The carbonized composite material prepared in S3 was added to a 1.3 mol / L sodium hydroxide solution for etching, stirring, natural cooling to room temperature, vacuum filtration, washing, and drying to obtain a highly adsorbent environmentally friendly seaweed carbon material. The etching parameters were set as follows: temperature 250℃, pressure 3 MPa, time 8 h; the drying parameters were set as follows: temperature 113℃, time 18 h.

[0056] Example 2 The composition and preparation process are the same as in Example 1, except that: In the S12 preparation process, the bridging molecular solution is chitosan (degree of deacetylation > 85%), the mass ratio of chitosan to seaweed powder is 4:20, the functional metal salt is ferric chloride, and its mass ratio to seaweed powder is 1:10, and other components are the same.

[0057] The stirring parameters in step S12 of the preparation process are set as follows: temperature 40℃, duration 2h, rotation speed 200rpm, and other steps are the same.

[0058] In the preparation process S13, the soft template agent is ammonium citrate, and its mass ratio with seaweed powder is 1:3, with other components being the same.

[0059] The stirring parameters in step S13 of the preparation process are set as follows: duration 1 hour, rotation speed 200 rpm, and other steps are the same.

[0060] In the preparation process S2, the mass ratio of monodisperse mesoporous silica nanospheres to seaweed powder is 1:1, and other components are the same.

[0061] In step S2 of the preparation process, the ball milling parameters are set as follows: zirconia balls are used as the grinding medium, the ball-to-material ratio is 4:1, the rotation speed is 200 rpm, and the time is 4 h; the hydraulic forming parameters are set as follows: pressure is 10 MPa, and the time is 3 min; the drying parameters are set as follows: temperature is 60℃, and the time is 12 h. Other steps are the same.

[0062] In step S3 of the preparation process, gradient heating pyrolysis is performed while nitrogen is continuously introduced. The parameters are set as follows: heating rate of 1℃ / min, temperature of 250℃, and duration of 30min in the low-temperature stage; heating rate of 2℃ / min, temperature of 500℃, and duration of 60min in the high-temperature carbonization stage; and the other steps are the same.

[0063] In step S4 of the preparation process, the etching solution is a 0.5 mol / L sodium hydroxide solution, and the other components are the same.

[0064] In the S4 process, the etching parameters are set as follows: temperature 200℃, pressure 2MPa, and time 10h; the drying parameters are set as follows: temperature 105℃ and time 12h. Other steps are the same.

[0065] Example 3 The composition and preparation process are the same as in Example 1, except that: In the preparation process S12, the bridging molecule solution is polyacrylamide, with a mass ratio of 1:20 to seaweed powder, and the functional metal salt is calcium nitrate, with a mass ratio of 1:40 to seaweed powder. Other components are the same.

[0066] The stirring parameters in step S12 of the preparation process are set as follows: temperature 50℃, duration 3h, rotation speed 400rpm, and other steps are the same.

[0067] In the preparation process S13, the soft template agent is urea, and its mass ratio with seaweed powder is 1:10, with other components being the same.

[0068] The stirring parameters in step S13 of the preparation process are set as follows: duration 2 hours, rotation speed 400 rpm, and other steps are the same.

[0069] In the preparation process S2, the mass ratio of monodisperse mesoporous silica nanospheres to seaweed powder is 1.5:1, and other components are the same.

[0070] In step S2 of the preparation process, the ball milling parameters are set as follows: zirconia balls are used as the grinding medium, the ball-to-material ratio is 4:1, the rotation speed is 300 rpm, and the time is 6 h; the hydraulic forming parameters are set as follows: pressure is 30 MPa, and the time is 1 min; the drying parameters are set as follows: temperature is 80 ℃, and the time is 24 h. Other steps are the same.

[0071] In step S3 of the preparation process, gradient heating pyrolysis is performed with continuous nitrogen gas flow. The parameters are set as follows: heating rate of 5℃ / min, temperature of 350℃, and duration of 120min in the low-temperature stage; heating rate of 6℃ / min, temperature of 700℃, and duration of 180min in the high-temperature carbonization stage; and the other steps are the same.

[0072] In step S4 of the preparation process, the etching solution is a 2 mol / L sodium hydroxide solution, and the other components are the same.

[0073] In the preparation process S4, the etching parameters were set as follows: temperature 300℃, pressure 4MPa, and time 6h; the drying parameters were set as follows: temperature 120℃ and time 24h. Other steps were the same.

[0074] Example 4 The composition and preparation process are the same as in Example 1, except that: In the preparation process, the bridging molecular solution in S12 is polyethyleneimine, with a mass ratio of 6:20 to seaweed powder, and the functional metal salt is magnesium chloride, with a mass ratio of 1:35 to seaweed powder. Other components are the same.

[0075] The stirring parameters in step S12 of the preparation process are set as follows: temperature 42℃, duration 2.8h, rotation speed 350rpm, and other steps are the same.

[0076] In the preparation process S13, the soft template agent is ammonium citrate, and its mass ratio with seaweed powder is 1:9, with other components being the same.

[0077] The stirring parameters in step S13 of the preparation process are set as follows: duration 1.8h, rotation speed 220rpm, and other steps are the same.

[0078] In the preparation process S2, the mass ratio of monodisperse mesoporous silica nanospheres to seaweed powder is 1.4:1, and other components are the same.

[0079] In the S2 step of the preparation process, the ball milling parameters are set as follows: zirconia balls are used as the grinding medium, the ball-to-material ratio is 4:1, the rotation speed is 270 rpm, and the time is 4.5 h; the hydraulic forming parameters are set as follows: pressure is 12 MPa, and the time is 1.2 min; the drying parameters are set as follows: temperature is 75 ℃, and the time is 20 h. Other steps are the same.

[0080] In step S3 of the preparation process, gradient heating pyrolysis is performed while nitrogen is continuously introduced. The parameters are set as follows: heating rate of 4℃ / min, temperature of 320℃, and duration of 100min in the low-temperature stage; heating rate of 5℃ / min, temperature of 680℃, and duration of 160min in the high-temperature carbonization stage; and the other steps are the same.

[0081] In step S4 of the preparation process, the etching solution is a 1.8 mol / L sodium hydroxide solution, and the other components are the same.

[0082] In the preparation process S4, the etching parameters were set as follows: temperature 220℃, pressure 2.5MPa, and time 9h; the drying parameters were set as follows: temperature 117℃ and time 14h. Other steps were the same.

[0083] Comparative Example 1 The composition and preparation process are the same as in Example 1, except that: No bridging molecules are added in step S1 of the preparation process; the other steps are the same.

[0084] Comparative Example 2 The composition and preparation process are the same as in Example 1, except that: In step S2 of the preparation process, no mesoporous silica nanospheres are added; pores are created solely using a soft template, urea. The other steps are the same.

[0085] Samples of the high-adsorption-performance environmentally friendly seaweed char material prepared in Example 1 were taken, sputter-coated with gold, and observed using a scanning electron microscope (accelerating voltage 5kV, working distance 8mm). Figure 2 As shown in Figure (a), the spherical mesoporous cavities left after the silica hard template and the interconnected macropores formed by particle accumulation are visible, indicating that the hard and soft dual templates were successfully achieved. A sample of the high-adsorption-performance environmentally friendly seaweed carbon material prepared in Example 1 was taken, anhydrous ethanol was added, and the mixture was sonicated for 30 min. The upper suspension was then pipetted onto an ultrathin carbon support film and allowed to dry naturally under an infrared lamp. The film was then observed using a transmission electron microscope (accelerating voltage 200 kV, bright field imaging). Figure 2 As shown in Figure (b), a large number of metal / metal oxide nanoclusters with a diameter of less than 5 nm are uniformly distributed in the carbon matrix, indicating that the bridging molecules effectively anchor the active metal sites on the porous framework.

[0086] Based on Examples 1-4 and Comparative Examples 1-2, samples of the finally prepared seaweed char material were taken for specific surface area testing: the seaweed char material was blown with high-purity nitrogen at 120°C for 5 hours, and then adsorbed with low-temperature nitrogen, referring to the standard GB / T19587-2017 "Determination of specific surface area of ​​solid materials by gas adsorption BET method".

[0087] Based on Examples 1-4 and Comparative Examples 1-2, samples of the finally prepared seaweed char material were taken for iodine adsorption value testing: The seaweed char material was ground, passed through a 200-mesh sieve, and dried at 105℃ to constant weight. 0.5g of the sample was added to 50mL of iodine standard solution (0.1mol / L), and the mixture was shaken at a constant temperature (25℃, 30min). After filtration, 10mL of the filtrate was titrated with sodium thiosulfate standard solution until a pale yellow color was obtained. Starch indicator was added, and titration continued until the blue color disappeared. Five groups were tested, and the average value was taken. The calculation formula is as follows: Where V0 is the blank consumption volume, V is the sample consumption volume, C is the sodium thiosulfate concentration, m is the sample mass, and 126.9 is the molar mass of iodine.

[0088] Based on Examples 1-4 and Comparative Examples 1-2, samples of the finally prepared seaweed char material were taken for methylene blue adsorption value testing: methylene blue standard solutions with concentrations of 5 mg / L, 7.5 mg / L, 10 mg / L, 12.5 mg / L, and 15 mg / L were prepared, and 0.1 g of seaweed char material sample was added to each solution. The mixture was shaken at room temperature for 2 hours. The absorbance of the supernatant was measured using a UV-Vis spectrophotometer at the characteristic absorption wavelength of methylene blue. The absorbance was converted to the residual concentration using a standard curve, and the mass of methylene blue adsorbed per unit mass of sample was calculated.

[0089] Combining Examples 1-4 and Comparative Examples 1-2, samples of the finally prepared seaweed charcoal material were taken and subjected to Pb analysis. 2+ Adsorption capacity test: Wastewater solutions of lead nitrate with concentrations of 100 mg / L, 150 mg / L, 200 mg / L, 250 mg / L, 300 mg / L, 350 mg / L, and 400 mg / L were prepared, and the pH was adjusted to 5. Then, 0.1 g of sample was added to each solution, and the solutions were incubated at 25°C for 5 hours with constant shaking. The remaining Pb in the filtrate was determined using atomic absorption spectrometry. 2+ concentration.

[0090] The specific test results are shown in Table 2. Figure 2 , Figure 3 As shown: Table 2 Comparison of core performance of Examples 1-4 and Comparative Examples 1-2

[0091] The comparison results above show that Example 1 has the best overall performance. The bridging molecules stabilized the precursor network, and the hard template accurately replicated abundant mesopores. The high adsorption capacity for methylene blue and heavy metals indicates that Example 1 successfully solved the problem of limited adsorption capacity and selectivity caused by the underdeveloped pore structure and insufficient surface active sites of seaweed biochar. The overall performance of Examples 2 to 4 is slightly lower than that of Example 1, but still maintains a high level. This shows that excellent adsorption effects were still achieved under a wide range of parameter variations. Comparative Example 1, due to the lack of bridging molecules, has a loose precursor structure and underdeveloped pores after pyrolysis, resulting in the lowest adsorption index. This proves that bridging molecules are the basis for building a well-developed structure. Comparative Example 2 did not use a hard template and relied solely on a urea soft template to create pores. Its specific surface area and adsorption value were much lower than any of the examples, indicating that a hard template is indispensable for forming a high specific surface area.

[0092] In summary, it can be clearly seen from the above embodiments and comparative examples that the highly adsorbent seaweed char material provided by the present invention solves the problems of underdeveloped pore structure and insufficient surface active sites in seaweed biochar, which lead to limited adsorption capacity and selectivity, while being environmentally friendly.

Claims

1. A high-adsorption-performance environmentally friendly seaweed charcoal material, possessing a porous structure and adsorption active sites, characterized in that: The porous structure consists of macropores formed by the self-accumulation of gaps, mesopores formed after the removal of hard template particles, and micropores generated inside and on the surface of the mesoporous framework; the mesopores are composed of spherical cavities; the adsorption active sites are metal active sites, which are dispersed and anchored on the framework of the porous structure through a nitrogen-containing carbon layer.

2. The environmentally friendly seaweed charcoal material with high adsorption performance according to claim 1, characterized in that: The seaweed charcoal material has a specific surface area ≥ 600 m². 2 / g, iodine adsorption value ≥1300mg / g, methylene blue adsorption value ≥300mg / g, Pb 2+ The adsorption capacity is ≥150mg / g.

3. The method for preparing the high-adsorption-performance environmentally friendly seaweed charcoal material according to any one of claims 1-2, characterized in that, Includes the following steps: S1: Raw material pretreatment and molecular bridging; S11: Add dried seaweed powder to deionized water, stir, and ultrasonically disperse to obtain seaweed suspension; S12: Add the bridging molecule solution to the seaweed suspension prepared in S11, stir, then add the functional metal salt, and continue stirring to obtain the chelated solution; S13: Add the soft template agent to the chelation solution prepared in S12, stir, and obtain the seaweed composite slurry; S2: Hard template composite and molding, monodisperse mesoporous silica nanospheres are added to the seaweed composite slurry prepared in S13, stirred until there are no dry powder lumps, ball milled, hydraulically molded, and dried to obtain a dry green body that can be used for pyrolysis. S3: Pyrolysis and activation. The dried green body prepared in S2 is placed in a sealed furnace, the air is replaced, the temperature is gradually increased for pyrolysis, and then it is naturally cooled to room temperature to obtain the carbonized composite material. S4: Post-processing: The carbonized composite material prepared in S3 is added to the etching solution for etching, stirred, naturally cooled to room temperature, vacuum filtered, washed, and dried to obtain environmentally friendly seaweed carbon material with high adsorption performance.

4. The method for preparing a high-adsorption-performance environmentally friendly seaweed charcoal material according to claim 3, characterized in that: The seaweed powder described in S11 has a mass-to-volume ratio of 1:10 to deionized water. The ultrasonic dispersion described in S11 has the following parameter settings: power 300W, frequency 40kHz, duration 30min.

5. The method for preparing a high-adsorption-performance environmentally friendly seaweed charcoal material according to claim 3, characterized in that: The bridging molecule solution described in S12 has a bridging molecule specifically selected from polyethyleneimine, chitosan, and polyacrylamide, and the mass ratio of the bridging molecule to seaweed powder is 1:20 to 6:

20. The stirring described in S12 has the following parameters: temperature 40-50℃, duration 2-3h, and speed 200-400rpm. The functional metal salt described in S12 is one or more of magnesium chloride, lanthanum chloride, ferric chloride, and calcium nitrate, and its mass ratio with seaweed powder is 1:10 to 1:

40.

6. The method for preparing a high-adsorption-performance environmentally friendly seaweed charcoal material according to claim 3, characterized in that: The soft template agent described in S13 is one of urea and ammonium citrate, and its mass ratio with seaweed powder is 1:3 to 1:

10. The stirring described in S13 has the following parameters: temperature 30℃, duration 1-2h, and speed 200-400rpm.

7. The method for preparing a high-adsorption-performance environmentally friendly seaweed charcoal material according to claim 3, characterized in that: The monodisperse mesoporous silica nanospheres described in S2 have a mass ratio of 1:1 to 1.5:1 with seaweed powder. The ball mill described in S2 has the following parameter settings: using zirconia balls as the grinding medium, a ball-to-material ratio of 4:1, a rotation speed of 200-300 rpm, and a duration of 4-6 hours.

8. The method for preparing a high-adsorption-performance environmentally friendly seaweed charcoal material according to claim 3, characterized in that: The hydraulic forming described in S2 has the following parameter settings: pressure 10-30MPa, duration 1-3min; The drying process described in S2 has the following parameters: temperature 60–80°C, duration 12–24 hours.

9. The method for preparing a high-adsorption-performance environmentally friendly seaweed charcoal material according to claim 3, characterized in that: The gradient heating pyrolysis described in S3 involves continuous nitrogen gas flow, with the following parameter settings: heating rate of 1–5℃ / min in the low-temperature stage, temperature of 250–350℃, and duration of 30–120min; heating rate of 2–6℃ / min in the high-temperature carbonization stage, temperature of 500–700℃, and duration of 60–180min.

10. The method for preparing a high-adsorption-performance environmentally friendly seaweed charcoal material according to claim 3, characterized in that: The etching solution described in S4 is a sodium hydroxide solution of 0.5–2 mol / L; The etching described in S4 has the following parameters: temperature 200-300℃, pressure 2-4MPa, and duration 6-10h. The drying process described in S4 has the following parameters: temperature 105–120°C, duration 12–24 hours.

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