Preparation method and application of sweet potato vine base high-performance adsorptive biochar

Abstract

The application discloses a preparation method of sweet potato vine base high-performance adsorptive biochar in the field of biochar and application thereof, the sweet potato vine is utilized in a high value way, a biochar base composite material is obtained through multi-element modification, conversion from sweet potato vine raw materials to final functional adsorption material is realized, N and S heteroatom precursors are introduced into the material, and Cu base nanoparticles are loaded, functionalization improvement of the biochar is realized, in the adsorption process, relying on the targeted active sites of the ternary structure, a differential synergistic adsorption mechanism for different types of pollutants is realized, and the biochar has the characteristics of high adsorption capacity, fast reaction rate, strong fixation / mineralization capacity and wide environmental adaptability.

Description

Technical Field

[0001] This invention belongs to the field of biochar technology, specifically referring to a method for preparing high-performance adsorbent biochar based on sweet potato vines and its application. Background Technology

[0002] Pollutants in water bodies, such as heavy metal ions, phosphates, dyes, and pesticides, are difficult to degrade and have strong bioaccumulation properties, easily leading to eutrophication of water bodies and excessive heavy metal levels in soil, seriously threatening ecosystem stability and human health. Volatile organic compounds and acidic gases in the atmosphere are important precursors to ozone and PM2.5, significantly impacting air quality. Adsorption methods, due to their simplicity, high efficiency, and wide applicability, have become one of the most widely used technologies for water and air pollution control. The core of this approach lies in developing high-performance, low-cost, and environmentally friendly adsorption materials.

[0003] Current adsorption materials, such as activated carbon, zeolite, and molecular sieves, while possessing good adsorption performance, have significant drawbacks: activated carbon preparation largely relies on fossil resources or high-quality wood-based raw materials, resulting in high costs and non-renewable resources; inorganic adsorption materials such as zeolite and molecular sieves have limited specific surface areas, poor selectivity for specific pollutants, and their adsorption capacity is insufficient for advanced treatment requirements. Biochar, a carbon-rich solid material formed by the pyrolysis and carbonization of biomass raw materials under anaerobic or oxygen-limited conditions, possesses characteristics such as porous structure, abundant surface functional groups, and strong chemical stability, and its raw materials are widely available and inexpensive. Surface modification of biochar through physical, chemical, or biological methods can further optimize its pore structure, increase surface active sites, and significantly improve the adsorption capacity and selectivity for target pollutants, representing a key approach to enhancing the adsorption performance of biochar.

[0004] Sweet potatoes are a widely cultivated food and cash crop globally. my country ranks among the world's top countries in both sweet potato planting area and yield. The sweet potato vines, a byproduct of cultivation, are produced in huge quantities but have not yet been utilized at a high value; most are discarded directly or simply used as animal feed. Sweet potato vines are rich in biomass core components such as cellulose, hemicellulose, and lignin. They have a high carbon content and low ash content, making them an excellent precursor for biochar production. Using sweet potato vines as raw material to prepare adsorbent biochar can transform agricultural waste into a valuable resource, possessing both resource utilization and environmental protection value.

[0005] However, existing technologies still have many problems that urgently need to be solved. First, sweet potato vine-based biochar has inherent defects. Biochar prepared by direct pyrolysis has an underdeveloped pore structure, small specific surface area, and few active functional groups such as oxygen and nitrogen on its surface, resulting in low adsorption capacity and selectivity for pollutants, making it difficult to meet the needs of deep treatment in actual pollution control. Second, existing modification methods for sweet potato vine-based biochar are relatively simple, mostly using simple acid-base impregnation or single metal ion loading. The modification methods lack systematic optimization and do not fully utilize the synergistic effect of physical structure regulation and chemical functional group modification, resulting in limited improvement in the adsorption performance of modified biochar. Third, existing sweet potato vine-based biochar has poor regeneration and recycling performance. After adsorption saturation, it is difficult to efficiently desorb and regenerate, increasing the cost of practical applications. Moreover, some modification methods easily introduce secondary pollutants, reducing the environmental friendliness of the material. Summary of the Invention

[0006] To address the above issues and overcome the shortcomings of existing technologies, this invention provides a method for preparing high-performance adsorbent biochar based on sweet potato vines and its application. This invention utilizes sweet potato vines for high-value purposes, obtaining biochar-based composite materials through multi-element modification, thus realizing the transformation from sweet potato vine raw materials to final functional adsorbent materials. N and S heteroatom precursors are introduced into the material, and Cu-based nanoparticles are loaded, thereby achieving functional improvement of the biochar. During adsorption, relying on the targeted active sites of the ternary structure, a differentiated synergistic adsorption mechanism is achieved for different types of pollutants, exhibiting characteristics of high adsorption capacity, fast reaction rate, strong immobilization / mineralization ability, and wide environmental adaptability.

[0007] To achieve the above objectives, the technical solution adopted by this invention is as follows: This invention proposes a method for preparing high-performance adsorbent biochar based on sweet potato vines, specifically including the following steps:

[0008] S1. Preparation of sweet potato vine nanocellulose powder: Fresh sweet potato vines were treated with alkali to produce sweet potato vine-based nanocellulose powder.

[0009] S2. Bromination treatment of sweet potato vine-based nanocellulose: The sweet potato vine-based nanocellulose powder prepared in step S1 is subjected to a nucleophilic substitution reaction with phosphorus tribromide using pyridine as an acid-binding agent to obtain brominated sweet potato vine-based nanocellulose.

[0010] S3. Preparation of the modifier: Using 2-cyanothiophene as a reactant, an intermolecular cyano ring trimerization reaction occurs under the catalysis of trifluoromethanesulfonic acid to form an intermediate with a triazine ring-thiophene structure, yielding 2,4,6-tris(thiophene-2-yl)-1,3,5-triazine; the thiophene group in 2,4,6-tris(thiophene-2-yl)-1,3,5-triazine is activated by n-butyllithium and tributyltin chloride to obtain a reactive modifier;

[0011] S4. Preparation of modified sweet potato vine-based nanocellulose: Under the catalysis of tetra(triphenylphosphine)palladium, the brominated sweet potato vine-based nanocellulose prepared in step S2 is subjected to Stille cross-coupling reaction with the modifier prepared in step S3 to achieve covalent grafting of the modifier and sweet potato vine-based nanocellulose, thereby obtaining modified sweet potato vine-based nanocellulose.

[0012] Preparation of S5, Cu-Cu2O / Modified Sweet Potato Vine-Based Nanocellulose: In the modified sweet potato vine-based nanocellulose described in step S4, the N in the triazine ring and the S in the thiophene ring affect the Cu... 2+ Its affinity for Cu makes it compatible with Cu 2+ Coordinate bonds are formed, and Cu is reduced by ethylene glycol. 2+ Reduced to Cu 0 Cu-Cu2O forms nanoparticles, which are then anchored on a CNF framework to obtain Cu-Cu2O / modified sweet potato vine-based nanocellulose.

[0013] S6. Pyrolysis treatment: Through high-temperature pyrolysis treatment, Cu-Cu2O / modified sweet potato vine-based nanocellulose forms a porous carbon framework with micropores / mesoporous structures. The supported Cu-Cu2O undergoes a high-temperature hybridization reaction with N and S in the carbon framework to generate CuN and CuS nanoparticles, thus obtaining high-performance adsorbent biochar based on sweet potato vines.

[0014] Furthermore, the preparation method of the sweet potato vine-based high-performance adsorbent biochar specifically includes the following steps:

[0015] S1. Preparation of sweet potato vine nanocellulose powder:

[0016] S11. Take fresh sweet potato vines, wash them, cut them into 3-5cm sections, dry them until completely dry, grind them in a grinder and then sieve them to obtain sweet potato vine powder.

[0017] S12. Accurately weigh the sweet potato vine powder prepared in step S11 and disperse it in NaOH aqueous solution. Raise the reaction temperature to carry out alkaline hydrolysis. After the reaction is completed, wait for the reaction system to cool naturally to room temperature, filter, collect the filter cake, wash and dry it to obtain sweet potato vine crude fiber.

[0018] Preferably, in step S12, the solid-liquid ratio between the sweet potato vine powder and the NaOH aqueous solution is 1g:15-20mL; the mass fraction of NaOH in the NaOH aqueous solution is 3%-5%.

[0019] Preferably, in step S12, the alkaline hydrolysis temperature is 90-100℃ and the alkaline hydrolysis time is 2-3 hours;

[0020] S13. Disperse the sweet potato vine crude fiber prepared in step S12 in deionized water, and perform high-speed shearing and homogenization treatment in sequence. Centrifuge, take the supernatant for dialysis, freeze dry, and obtain sweet potato vine-based nanocellulose powder.

[0021] Preferably, in step S13, the shearing speed of the high-speed shearing process is 10,000-12,000 rpm, and the high-speed shearing time is 3-5 min; the working pressure of the homogenization process is 70-80 MPa, and the number of homogenization cycles is 6-8.

[0022] S2. Bromination treatment of sweet potato vine-based nanocellulose: After drying the sweet potato vine-based nanocellulose powder prepared in step S1, it was dispersed in anhydrous dichloromethane, phosphorus tribromide and pyridine were added, and after mixing evenly, a bromination reaction was carried out. After the reaction was completed, it was cooled, slowly transferred to ice water for quenching, filtered, the solid was collected, washed, and dried to obtain brominated sweet potato vine-based nanocellulose.

[0023] Preferably, in step S2, the solid-liquid ratio between the sweet potato vine-based nanocellulose powder and phosphorus tribromide is 1g:0.9-1.3mL;

[0024] Preferably, in step S2, the solid-liquid ratio between the sweet potato vine cellulose powder and pyridine is 1g:0.8-1.2mL;

[0025] Preferably, in step S2, the reaction temperature of the bromination reaction is 30-40°C, and the reaction time of the bromination reaction is 4-6 hours.

[0026] S3. Preparation of the modifier:

[0027] S31. Dissolve 2-cyanothiophene in anhydrous chloroform and transfer it to an ice-water bath. Add trifluoromethanesulfonic acid dropwise while maintaining the ice-water bath conditions. After continuous stirring and mixing, carry out a cyclotrimerization reaction at room temperature. After the reaction is completed, wash three times with deionized water, collect the organic phase, dry it to remove water, and then distill under reduced pressure, purify and dry it to obtain 2,4,6-tris(thiophene-2-yl)-1,3,5-triazine.

[0028] Preferably, in step S31, the volume ratio between 2-cyanothiophene and trifluoromethanesulfonic acid is 1:3.8-4.3;

[0029] Preferably, in step S31, the reaction time for the cyclotrimerization reaction is 40-50 hours;

[0030] S32. Dissolve the 2,4,6-tris(thiophen-2-yl)-1,3,5-triazine obtained in step S31 in anhydrous THF, transfer it to a dry ice-acetone bath, add n-butyllithium to carry out the lithiation reaction. After the reaction is completed, maintain the dry ice-acetone bath conditions, add tributyltin chloride, heat to room temperature, and continuously stir to carry out the tinification reaction. After the reaction is completed, slowly pour it into a saturated ammonium chloride aqueous solution for quenching, add anhydrous diethyl ether for extraction, combine the organic phases, wash the organic layer with saturated NaCl aqueous solution and deionized water, dry to remove water, and after vacuum distillation, purification, and drying, obtain 2,4,6-tris(5-(tributyltinyl)thiophen-2-yl)-1,3,5-triazine, which is the modifier;

[0031] Preferably, in step S32, the molar ratio between 2,4,6-tris(thiophene-2-yl)-1,3,5-triazine and n-butyllithium and tributyltin chloride is 1:3.3-3.5:3.1-3.3;

[0032] Preferably, in step S32, the reaction time for lithiation is 1-2 hours, and the reaction time for tinning is 6-8 hours.

[0033] S4. Preparation of modified sweet potato vine-based nanocellulose: The brominated sweet potato vine-based nanocellulose prepared in step S2 was dispersed in a DMF / water mixed solvent, the modifier prepared in step S3 was added, and after continuous mixing, tetra(triphenylphosphine)palladium was added, and the reaction temperature was increased to carry out the coupling reaction. After the reaction was completed, the mixture was cooled, centrifuged, the precipitate was collected, washed, and dried to obtain modified sweet potato vine-based nanocellulose.

[0034] Preferably, in step S4, the mass ratio of the brominated sweet potato vine-based nanocellulose to the modifier is 1:0.2-0.4;

[0035] Preferably, in step S4, the reaction temperature of the coupling reaction is 70-80℃, and the reaction time of the coupling reaction is 12-16h.

[0036] S5. Preparation of Cu-Cu2O / modified sweet potato vine-based nanocellulose: Ethylene glycol and anhydrous ethanol were mixed, Cu(NO3)2·3H2O was added, and the modified sweet potato vine-based nanocellulose prepared in step S4 was added. After mixing evenly, the mixture was transferred to a high-pressure reactor, sealed, and the temperature was raised to carry out a hydrothermal reaction. After the reaction was completed, the mixture was cooled, centrifuged, and the precipitate was collected. After washing and drying, Cu-Cu2O / modified sweet potato vine-based nanocellulose was obtained.

[0037] Preferably, in step S5, the volume ratio between ethylene glycol and anhydrous ethanol is 4-5:3-4;

[0038] Preferably, in step S5, the mass ratio between the modified sweet potato vine-based nanocellulose and Cu(NO3)2·3H2O is 1:0.2-0.3;

[0039] Preferably, in step S5, the hydrothermal reaction temperature is 160-180℃, and the hydrothermal reaction time is 4-6h.

[0040] S6. Pyrolysis treatment: The Cu-Cu2O / modified sweet potato vine-based nanocellulose prepared in step S5 is placed in a tube furnace, sealed, and flowing nitrogen is introduced to raise the temperature inside the furnace for pyrolysis treatment. After completion, it is cooled, the pyrolysis products are collected, ground and sieved to obtain high-performance adsorbent biochar based on sweet potato vines.

[0041] Preferably, in step S6, the pyrolysis temperature of the pyrolysis treatment is 700-800℃, and the pyrolysis time is 2-3h.

[0042] This invention also provides an application of high-performance adsorbent biochar based on sweet potato vines, specifically including the adsorption of high-valence heavy metals, heavy metal ions, and organic pollutants;

[0043] Preferably, the high-priced heavy metal includes at least one of Cr and As;

[0044] Preferably, the heavy metal ions include Hg. 2+ Pb 2+ Cd 2+ At least one of them;

[0045] Preferably, the organic pollutant includes at least one of tetracycline (TC), rhodamine B (RhB), and methyl orange (MO).

[0046] The beneficial effects achieved by this invention are as follows:

[0047] This invention provides a method for preparing high-performance adsorbent biochar based on sweet potato vines and its application. This invention utilizes sweet potato vines for high-value production by obtaining a biochar-based composite material through multi-component modification, realizing the transformation from sweet potato vine raw material to a final functional adsorbent material. N and S heteroatom precursors are introduced into the material, and Cu-based nanoparticles are loaded, thereby achieving functional improvement of the biochar. During adsorption, relying on the targeted active sites of the ternary structure, a differentiated synergistic adsorption mechanism is achieved for different types of pollutants, exhibiting high adsorption capacity, fast reaction rate, strong immobilization / mineralization ability, and wide environmental adaptability. In this invention, brominated sweet potato vine-based nanocellulose is covalently coupled to achieve covalent grafting of thiophene-triazine groups to the CNF carbon skeleton, stably anchoring the N and S heteroatom precursors on the carbon substrate. The N, O, and S functional groups on the modified CNF surface interact with Cu through lone pair electrons. 2+Ethylene glycol forms coordinate bonds with Cu. 2+ Reduced to Cu + / Cu 0 Cu-Cu2O nanoparticles are generated and loaded onto the material surface, achieving initial dispersion and anchoring of copper-based particles. The modified CNF cellulose carbon skeleton and the conjugated aromatic rings of thiophene-triazine undergo condensation and carbonization reactions at high temperatures, forming an amorphous carbon skeleton. The fusion of aromatic ring structures enhances the graphitization degree of the carbon skeleton, improving the material's chemical stability and electronic conductivity, providing electron transfer channels for redox and catalytic reactions. The N and S atoms in the thiophene-triazine groups detach from the organic precursors at high temperatures and are in-situ doped into the lattice and defect sites of the carbon skeleton, forming active functional groups such as pyridine N, pyrrole N, graphitic N, thiophene S, and CSC. The loaded Cu-Cu2O undergoes a high-temperature hybridization reaction with the N and S heteroatoms in the carbon skeleton, preferentially forming CuN and CuS composite nanoparticles. The N and S heteroatoms provide anchoring sites for the metal particles through coordination bonds, inhibiting their aggregation and controlling the particle size to 3-10 nm with high monodispersity. No free CuO / Cu 0 The formation of Cu is due to the fact that the hybridization reaction of N / S with Cu has a much higher priority than the oxidation / elementalization of Cu. It exhibits corresponding adsorption mechanisms for different pollutants. For highly toxic, high-valence heavy metals, the large specific surface area and pore structure of the hierarchical porous carbon framework rapidly adsorb and enrich Cr(VI) from water onto the material surface and within the pores, increasing the local pollutant concentration and accelerating subsequent reactions. The Cu in CuN is in a low valence state (Cu... + / Cu 0 It exhibits strong reducing activity, reducing water-soluble Cr(VI) to low-toxicity, poorly soluble Cr(III) under acidic conditions. The highly graphitized carbon skeleton provides a rapid electron transfer channel for the reaction, enhancing reduction efficiency. The resulting Cr(III) forms stable five- or six-membered ring coordination complexes with pyridine N and thiophene S in the carbon skeleton, while Cu... 2+ It forms a hydroxide co-precipitate with Cr(III), permanently fixing Cr(III) within the material pores, while the oxidized Cu... 2+ It can be reduced to Cu by the reducing carbon sites of the carbon skeleton. +This approach enables the recycling of CuN reduction sites. For heavy metal cations, different adsorption mechanisms are employed to adsorb different types of heavy metal cations, such as using irreversible chemical precipitation reactions to generate extremely insoluble precipitates, and using electrostatic adsorption and complexation to achieve efficient removal of heavy metal ions. For organic pollutants, the conjugated aromatic rings of the carbon skeleton undergo π-π stacking with the aromatic ring structure of the organic pollutants, and the NH and SH atoms of the N / S heteroatoms form hydrogen bonds with the amino, hydroxyl, and carbonyl groups of the organic pollutants. At the same time, the physical adsorption of the hierarchical porous carbon skeleton rapidly enriches the organic pollutants onto the material surface. These three factors work synergistically to achieve stable adsorption of organic pollutants, providing a high-concentration reaction environment for catalytic degradation. After the organic pollutants are mineralized, the originally occupied adsorption and catalytic sites are released, allowing for the continued adsorption and degradation of new pollutant molecules, thus achieving site recycling and significantly improving the adsorption capacity and concentration tolerance of the material. Attached Figure Description

[0048] Figure 1 The graph shows the adsorption performance of the high-performance adsorbent biochar prepared in Examples 1-3 and Comparative Examples 1-2 of this invention on highly toxic high-valence heavy metals.

[0049] Figure 2 The graph shows the adsorption performance of the high-performance adsorbent biochar prepared in Examples 1-3 and Comparative Examples 1-2 of this invention in the adsorption of heavy metal cations.

[0050] Figure 3 The graph shows the adsorption performance of the high-performance adsorbent biochar prepared in Examples 1-3 and Comparative Examples 1-2 of this invention on organic pollutants.

[0051] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof. Detailed Implementation

[0052] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0053] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those familiar to those skilled in the art. Furthermore, any methods and materials similar to or equivalent to those described herein may be applied to this invention. The preferred embodiments and materials described herein are for illustrative purposes only and do not limit the scope of this application.

[0054] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; unless otherwise specified, the experimental materials and test strains used in the following examples were purchased from commercial channels.

[0055] Example 1

[0056] This embodiment provides a method for preparing high-performance adsorbent biochar based on sweet potato vines, specifically including the following steps:

[0057] S1. Preparation of sweet potato vine nanocellulose powder:

[0058] S11. Take fresh sweet potato vines, wash and remove mud, withered leaves and rotten parts, cut into 3cm sections, dry in a forced-air dryer at 60℃ for 24 hours until completely dry, grind in a pulverizer and pass through a 60-mesh sieve to obtain sweet potato vine powder.

[0059] S12. Accurately weigh 10g of the dried sweet potato vine powder prepared in step S11 and place it in a three-necked flask. Add 200mL of 3% NaOH aqueous solution to the flask, turn on the magnetic stirrer, and stir at 300rpm. After mixing evenly, raise the reaction temperature to 90℃ and carry out alkaline hydrolysis. After reacting for 3 hours, wait for the reaction system to cool naturally to room temperature, filter, collect the filter cake, and wash it repeatedly with deionized water until neutral to obtain the crude fiber of sweet potato vine.

[0060] S13. Place the sweet potato vine coarse fiber prepared in step S12 into a flask, add deionized water, and perform high-speed shearing at 10000 rpm. After 5 min, transfer it to a high-pressure homogenizer and homogenize it at a working pressure of 70 MPa. After continuous homogenization for 8 cycles, centrifuge at 8000 rpm for 10 min, take the supernatant and place it in a dialysis bag (molecular weight cutoff of 14 kDa). Dialyze it with deionized water for 7 days, and then freeze-dry it to obtain sweet potato vine-based nanocellulose powder.

[0061] S2. Bromination treatment of sweet potato vine-based nanocellulose: The sweet potato vine-based nanocellulose powder prepared in step S1 was placed in a vacuum drying oven and dried at 100℃ for 2 hours. 4.0 g of sweet potato vine-based nanocellulose powder was accurately weighed and placed in a three-necked flask. It was dried by purging with nitrogen for 15 minutes. Under a dry nitrogen atmosphere, 80 mL of anhydrous dichloromethane was added to the reaction system. After stirring and dispersing at 300 rpm for 30 minutes, 4.1 mL of phosphorus tribromide and 3.9 mL of pyridine were added to the reaction system in sequence. The bromination reaction was carried out at 30℃ for 6 hours. After the reaction was completed, the reaction system was allowed to cool naturally to room temperature. The reaction system was then slowly transferred to ice water to quench the unreacted phosphorus tribromide. The solid was filtered, washed three times with 0.1 mol / L dilute hydrochloric acid aqueous solution, and then washed three times alternately with anhydrous ethanol and deionized water. Finally, it was dried under vacuum at 60℃ for 12 hours to obtain brominated sweet potato vine-based nanocellulose.

[0062] S3. Preparation of the modifier:

[0063] S31. Accurately weigh 2.0 mL of 2-cyanothiophene and place it in a three-necked flask. Add anhydrous chloroform to the flask and stir magnetically at 300 rpm until the reactants are completely dissolved. Place the reaction system in an ice-water bath and continue stirring to cool the reaction system thoroughly. Then, add 8.6 mL of trifluoromethanesulfonic acid dropwise to the reaction system through a constant pressure dropping funnel. After the addition is complete, maintain the ice-water bath conditions and continue stirring for 2.5 h. Raise the temperature to room temperature and maintain the room temperature conditions to continue stirring until the cyclotrimerization reaction occurs. The reaction takes 48 h. After the reaction is complete, transfer the reaction solution to a separatory funnel, wash it three times with deionized water, collect the organic phase, dry it with anhydrous magnesium sulfate to remove water, filter it to remove magnesium sulfate, collect the filtrate, remove the solvent by vacuum distillation using a rotary evaporator, recrystallize and purify it, and dry it under vacuum at 60 °C for 6 h to obtain 2,4,6-tris(thiophene-2-yl)-1,3,5-triazine.

[0064] S32. Take 6.3 g of 2,4,6-tris(thiophene-2-yl)-1,3,5-triazine obtained in step S31 and place it in a dry flask. After purging with nitrogen for 15 min, add 100 mL of anhydrous THF to the flask under a nitrogen atmosphere and stir at 300 rpm. After the reactants are completely dissolved, transfer the reaction system to a dry ice-acetone bath and stir continuously for 1 h. Cool the reaction system thoroughly. Dissolve 6.3 mL of n-butyllithium in n-hexane and add it dropwise to the reaction system through a constant pressure dropping funnel. After the addition is complete, continue stirring to carry out the lithiation reaction for 1 h. After the reaction is completed, while maintaining the dry ice-acetone bath conditions, add 17.3 mL of tributyltin chloride dropwise to the reaction system. After the addition of the reagents was complete, the reaction system was naturally heated to room temperature and stirred continuously for 6 hours. After the reaction was completed, the reaction solution was slowly poured into a saturated ammonium chloride aqueous solution for quenching. The solution was then transferred to a separatory funnel and extracted with anhydrous diethyl ether. The organic phase was collected, and the aqueous phase was repeatedly extracted with anhydrous diethyl ether three times. The organic phases were then combined, and the organic layer was washed twice with saturated NaCl aqueous solution and twice with deionized water. Anhydrous magnesium sulfate was added and dried overnight. The magnesium sulfate was removed by filtration, and the solvent was removed by vacuum distillation of the filtrate. After purification by silica gel column chromatography, the solvent was removed by distillation and dried under vacuum at 60°C for 6 hours to obtain 2,4,6-tris(5-(tributyltinyl)thiophene-2-yl)-1,3,5-triazine, which is the modifier.

[0065] S4. Preparation of modified sweet potato vine-based nanocellulose:

[0066] Accurately weigh 4.0 g of the brominated sweet potato vine-based nanocellulose prepared in step S2 and place it in a dry three-necked flask. After purging with flowing nitrogen gas for 15 min, add 80 mL of nitrogen gas to the flask under a nitrogen atmosphere. A DMF / water mixed solvent (the volume ratio of DMF to deionized water is 7:3) was used. The magnetic stirrer was turned on and stirred at 500 rpm for 30 min. The mixture was then sonicated at 300 W for 30 min to disperse the brominated sweet potato vine-based nanocellulose evenly in the reaction system. 0.8 g of the modifier prepared in step S3 was added to the reaction system and mixed evenly. Then, 88 mg of tetrakis(triphenylphosphine)palladium was added, and the reaction temperature was raised to 70 °C for coupling reaction. The reaction was carried out for 16 h. After the reaction was completed, the reaction system was naturally cooled to room temperature, centrifuged at 8000 rpm for 10 min, and the precipitate was collected. It was washed twice with 0.1 mol / L dilute hydrochloric acid aqueous solution, and then washed three times alternately with anhydrous ethanol and deionized water. Finally, it was vacuum dried at 60 °C for 12 h to obtain the modified sweet potato vine-based nanocellulose.

[0067] Preparation of S5, Cu-Cu2O / modified sweet potato vine-based nanocellulose: 25 mL of ethylene glycol and 20 mL of anhydrous ethanol were placed in a flask and mixed evenly. 1.0 g of Cu(NO3)2·3H2O was added to the flask and stirred at 300 rpm until completely dissolved. The modified sweet potato vine-based nanocellulose prepared in step S4 was accurately weighed and added to the reaction system. The mixture was ultrasonically treated in an ultrasonic cell disruptor at 400 W for 30 min to fully disperse 4.0 g of the modified sweet potato vine-based nanocellulose. The reaction system was then transferred to a high-pressure reactor, sealed, and heated to 160 °C for hydrothermal reaction for 6 h. After the reaction was completed, the reaction system was allowed to cool naturally to room temperature. The system was then centrifuged at 8000 rpm for 10 min, and the precipitate was collected. It was washed three times with anhydrous ethanol and deionized water, and then vacuum dried at 60 °C for 12 h to obtain Cu-Cu2O / modified sweet potato vine-based nanocellulose.

[0068] S6. Pyrolysis treatment: Accurately weigh the Cu-Cu2O / modified sweet potato vine-based nanocellulose prepared in step S5 and place it in a quartz boat. After spreading it evenly, place the quartz boat in a tube furnace, seal the tube furnace, and purge with flowing nitrogen at a rate of 50 mL / min for 30 min. Then, increase the furnace temperature at a rate of 5 °C / min to 700 °C and hold it at this temperature for 3 h. After the pyrolysis treatment is completed, keep the reaction system under a nitrogen atmosphere and allow it to cool naturally to room temperature. Collect the pyrolysis products, grind them, and pass them through a 100-mesh sieve to obtain high-performance adsorbent biochar based on sweet potato vines.

[0069] Example 2

[0070] This embodiment provides a method for preparing high-performance adsorbent biochar based on sweet potato vines, specifically including the following steps:

[0071] S1. Preparation of sweet potato vine nanocellulose powder:

[0072] S11. Take fresh sweet potato vines, wash and remove mud, withered leaves and rotten parts, cut into 4cm sections, dry in a forced-air dryer at 60℃ for 24 hours until completely dry, grind in a pulverizer and pass through a 60-mesh sieve to obtain sweet potato vine powder.

[0073] S12. Accurately weigh 10g of the dried sweet potato vine powder prepared in step S11 and place it in a three-necked flask. Add 180mL of 4% NaOH aqueous solution to the flask, turn on the magnetic stirrer, and stir at 300rpm. After mixing evenly, raise the reaction temperature to 95℃ and carry out alkaline hydrolysis. After reacting for 2.5h, wait for the reaction system to cool naturally to room temperature, filter, collect the filter cake, and wash it repeatedly with deionized water until neutral to obtain sweet potato vine crude fiber.

[0074] S13. Place the sweet potato vine coarse fiber prepared in step S12 into a flask, add deionized water, and perform high-speed shearing at 11000 rpm. After 4 min, transfer it to a high-pressure homogenizer and homogenize it at a working pressure of 75 MPa. After continuous homogenization for 7 cycles, centrifuge at 8000 rpm for 10 min, take the supernatant and place it in a dialysis bag (molecular weight cutoff of 14 kDa). Dialyze it with deionized water for 7 days, and then freeze-dry it to obtain sweet potato vine-based nanocellulose powder.

[0075] S2. Bromination treatment of sweet potato vine-based nanocellulose: The sweet potato vine-based nanocellulose powder prepared in step S1 was placed in a vacuum drying oven and dried at 100℃ for 2 hours. 5.0 g of sweet potato vine-based nanocellulose powder was accurately weighed and placed in a three-necked flask. It was dried by purging with nitrogen for 15 minutes. Under a dry nitrogen atmosphere, 80 mL of anhydrous dichloromethane was added to the reaction system. After stirring and dispersing at 300 rpm for 30 minutes, 6.3 mL of phosphorus tribromide and 5.8 mL of pyridine were added to the reaction system in sequence. The bromination reaction was carried out at 35℃ for 5 hours. After the reaction was completed, the reaction system was allowed to cool naturally to room temperature. The reaction system was then slowly transferred to ice water to quench the unreacted phosphorus tribromide. The solid was filtered, washed three times with 0.1 mol / L dilute hydrochloric acid aqueous solution, and then washed three times alternately with anhydrous ethanol and deionized water. Finally, it was dried under vacuum at 60℃ for 12 hours to obtain brominated sweet potato vine-based nanocellulose.

[0076] S3. Preparation of the modifier:

[0077] S31. Accurately weigh 3.0 mL of 2-cyanothiophene and place it in a three-necked flask. Add anhydrous chloroform to the flask and stir magnetically at 300 rpm until the reactants are completely dissolved. Place the reaction system in an ice-water bath and continue stirring to cool the system thoroughly. Then, add 12.0 mL of trifluoromethanesulfonic acid dropwise to the reaction system through a constant pressure dropping funnel. After the addition is complete, maintain the ice-water bath conditions and continue stirring for 2 hours. Raise the temperature to room temperature and maintain the room temperature conditions to continue stirring until the cyclotrimerization reaction occurs. The reaction takes 50 hours. After the reaction is complete, transfer the reaction solution to a separatory funnel, wash it three times with deionized water, collect the organic phase, dry it with anhydrous magnesium sulfate to remove water, filter it to remove magnesium sulfate, collect the filtrate, remove the solvent by vacuum distillation using a rotary evaporator, recrystallize and purify it, and dry it under vacuum at 60℃ for 6 hours to obtain 2,4,6-tris(thiophene-2-yl)-1,3,5-triazine.

[0078] S32. Take 9.3 g of 2,4,6-tris(thiophene-2-yl)-1,3,5-triazine obtained in step S31 and place it in a dry flask. After purging with nitrogen for 15 min, add 100 mL of anhydrous THF to the flask under a nitrogen atmosphere and stir at 300 rpm. After the reactants are completely dissolved, transfer the reaction system to a dry ice-acetone bath and stir continuously for 1 h. Cool the reaction system thoroughly. Dissolve 9.1 mL of n-butyllithium in n-hexane and add it dropwise to the reaction system through a constant pressure dropping funnel. After the addition is complete, continue stirring to carry out the lithiation reaction for 2 h. After the reaction is completed, while maintaining the dry ice-acetone bath conditions, add 24.1 mL of tributyltin chloride dropwise to the reaction system. After the addition of the reagents was complete, the reaction system was naturally heated to room temperature and stirred continuously for 8 hours. After the reaction was completed, the reaction solution was slowly poured into a saturated ammonium chloride aqueous solution for quenching. The solution was then transferred to a separatory funnel and extracted with anhydrous diethyl ether. The organic phase was collected, and the aqueous phase was repeatedly extracted with anhydrous diethyl ether three times. The organic phases were then combined, and the organic layer was washed twice with saturated NaCl aqueous solution and twice with deionized water. Anhydrous magnesium sulfate was added and dried overnight. The magnesium sulfate was removed by filtration, and the solvent was removed by vacuum distillation of the filtrate. After purification by silica gel column chromatography, the solvent was removed by distillation and dried under vacuum at 60°C for 6 hours to obtain 2,4,6-tris(5-(tributyltinyl)thiophene-2-yl)-1,3,5-triazine, which is the modifier.

[0079] S4. Preparation of modified sweet potato vine-based nanocellulose:

[0080] Accurately weigh 5.0 g of the brominated sweet potato vine-based nanocellulose prepared in step S2 and place it in a dry three-necked flask. After purging with flowing nitrogen gas for 15 min, add 80 mL of nitrogen gas to the flask under a nitrogen atmosphere. A DMF / water mixed solvent (the volume ratio of DMF to deionized water is 7:3) was used. The magnetic stirrer was turned on and stirred at 500 rpm for 30 min. The mixture was then sonicated at 300 W for 30 min to disperse the brominated sweet potato vine-based nanocellulose evenly in the reaction system. 1.5 g of the modifier prepared in step S3 was added to the reaction system and mixed evenly. Then, 140 mg of tetrakis(triphenylphosphine)palladium was added, and the reaction temperature was raised to 75 °C for coupling reaction. The reaction was carried out for 14 h. After the reaction was completed, the reaction system was naturally cooled to room temperature, centrifuged at 8000 rpm for 10 min, and the precipitate was collected. It was washed twice with 0.1 mol / L dilute hydrochloric acid aqueous solution, and then washed three times alternately with anhydrous ethanol and deionized water. Finally, it was vacuum dried at 60 °C for 12 h to obtain the modified sweet potato vine-based nanocellulose.

[0081] Preparation of Cu-Cu2O / modified sweet potato vine-based nanocellulose: 20 mL of ethylene glycol and 20 mL of anhydrous ethanol were placed in a flask and mixed evenly. 1.5 g of Cu(NO3)2·3H2O was added to the flask and stirred at 300 rpm until completely dissolved. The modified sweet potato vine-based nanocellulose prepared in step S4 was accurately weighed and added to the reaction system. The mixture was ultrasonically treated in an ultrasonic cell disruptor at 400 W for 30 min to fully disperse 5.0 g of the modified sweet potato vine-based nanocellulose. The reaction system was then transferred to a high-pressure reactor, sealed, and heated to 170 °C for hydrothermal reaction for 5 h. After the reaction was completed, the reaction system was allowed to cool naturally to room temperature. The system was then centrifuged at 8000 rpm for 10 min, and the precipitate was collected. It was washed three times with anhydrous ethanol and deionized water, and then vacuum dried at 60 °C for 12 h to obtain Cu-Cu2O / modified sweet potato vine-based nanocellulose.

[0082] S6. Pyrolysis treatment: Accurately weigh the Cu-Cu2O / modified sweet potato vine-based nanocellulose prepared in step S5 and place it in a quartz boat. After spreading it evenly, place the quartz boat in a tube furnace, seal the tube furnace, and purge with flowing nitrogen gas at a rate of 50 mL / min for 30 min. Then, increase the furnace temperature at a rate of 5 °C / min to 750 °C and maintain the temperature for pyrolysis treatment for 2.5 h. After the pyrolysis treatment is completed, keep the reaction system under a nitrogen atmosphere and allow it to cool naturally to room temperature. Collect the pyrolysis products, grind them, and pass them through a 100-mesh sieve to obtain high-performance adsorbent biochar based on sweet potato vines.

[0083] Example 3

[0084] This embodiment provides a method for preparing high-performance adsorbent biochar based on sweet potato vines, specifically including the following steps:

[0085] S1. Preparation of sweet potato vine nanocellulose powder:

[0086] S11. Take fresh sweet potato vines, wash and remove mud, withered leaves and rotten parts, cut into 5cm sections, dry in a forced-air dryer at 60℃ for 24 hours until completely dry, grind in a pulverizer and pass through a 60-mesh sieve to obtain sweet potato vine powder.

[0087] S12. Accurately weigh 10g of the dried sweet potato vine powder prepared in step S11 and place it in a three-necked flask. Add 150mL of 5% NaOH aqueous solution to the flask, turn on the magnetic stirrer, and stir at 300rpm. After mixing evenly, raise the reaction temperature to 100℃ and carry out alkaline hydrolysis. After reacting for 2 hours, wait for the reaction system to cool naturally to room temperature, filter, collect the filter cake, and wash it repeatedly with deionized water until neutral to obtain sweet potato vine crude fiber.

[0088] S13. Place the sweet potato vine coarse fiber prepared in step S12 into a flask, add deionized water, and perform high-speed shearing at 12000 rpm. After 3 min, transfer it to a high-pressure homogenizer and homogenize it at a working pressure of 80 MPa. After continuous homogenization for 6 cycles, centrifuge at 8000 rpm for 10 min, take the supernatant and place it in a dialysis bag (molecular weight cutoff of 14 kDa). Dialyze it with deionized water for 7 days, and then freeze-dry it to obtain sweet potato vine-based nanocellulose powder.

[0089] S2. Bromination treatment of sweet potato vine-based nanocellulose: The sweet potato vine-based nanocellulose powder prepared in step S1 was placed in a vacuum drying oven and dried at 100℃ for 2 hours. 6.0 g of sweet potato vine-based nanocellulose powder was accurately weighed and placed in a three-necked flask. It was dried by purging with nitrogen for 15 minutes. Under a dry nitrogen atmosphere, 80 mL of anhydrous dichloromethane was added to the reaction system. After stirring and dispersing at 300 rpm for 30 minutes, 5.4 mL of phosphorus tribromide and 5.0 mL of pyridine were added to the reaction system in sequence. The bromination reaction was carried out at 40℃ for 4 hours. After the reaction was completed, the reaction system was allowed to cool naturally to room temperature. The reaction system was then slowly transferred to ice water to quench the unreacted phosphorus tribromide. The solid was filtered, washed three times with 0.1 mol / L dilute hydrochloric acid aqueous solution, and then washed three times alternately with anhydrous ethanol and deionized water. Finally, it was dried under vacuum at 60℃ for 12 hours to obtain brominated sweet potato vine-based nanocellulose.

[0090] S3. Preparation of the modifier:

[0091] S31. Accurately weigh 4.0 mL of 2-cyanothiophene and place it in a three-necked flask. Add anhydrous chloroform to the flask and stir magnetically at 300 rpm until the reactants are completely dissolved. Place the reaction system in an ice-water bath and continue stirring to cool the system thoroughly. Then, add 15.2 mL of trifluoromethanesulfonic acid dropwise to the reaction system through a constant pressure dropping funnel. After the addition is complete, maintain the ice-water bath conditions and continue stirring for 3 hours. Raise the temperature to room temperature and maintain the room temperature conditions to continue stirring until the cyclotrimerization reaction occurs. The reaction takes 40 hours. After the reaction is complete, transfer the reaction solution to a separatory funnel, wash it three times with deionized water, collect the organic phase, dry it with anhydrous magnesium sulfate to remove water, filter it to remove magnesium sulfate, collect the filtrate, remove the solvent by vacuum distillation using a rotary evaporator, recrystallize and purify it, and dry it under vacuum at 60°C for 6 hours to obtain 2,4,6-tris(thiophene-2-yl)-1,3,5-triazine.

[0092] S32. Take 12.3 g of 2,4,6-tris(thiophene-2-yl)-1,3,5-triazine obtained in step S31 and place it in a dry flask. After purging with nitrogen for 15 min, add 100 mL of anhydrous THF to the flask under a nitrogen atmosphere and stir at 300 rpm. After the reactants are completely dissolved, transfer the reaction system to a dry ice-acetone bath and stir continuously for 1 h. Cool the reaction system thoroughly. Dissolve 11.6 mL of n-butyllithium in n-hexane and add it dropwise to the reaction system through a constant pressure dropping funnel. After the addition is complete, continue stirring to carry out the lithiation reaction for 1.5 h. After the reaction is completed, while maintaining the dry ice-acetone bath conditions, add 30.0 mL of tributyltin chloride dropwise to the reaction system. After the addition of the reagents was complete, the reaction system was naturally heated to room temperature and stirred continuously for 7 hours. After the reaction was completed, the reaction solution was slowly poured into a saturated ammonium chloride aqueous solution for quenching. The solution was then transferred to a separatory funnel and extracted with anhydrous diethyl ether. The organic phase was collected, and the aqueous phase was repeatedly extracted with anhydrous diethyl ether three times. The organic phases were then combined, and the organic layer was washed twice with saturated NaCl aqueous solution and twice with deionized water. Anhydrous magnesium sulfate was added and dried overnight. The magnesium sulfate was removed by filtration, and the solvent was removed by vacuum distillation of the filtrate. After purification by silica gel column chromatography, the solvent was removed by distillation and dried under vacuum at 60°C for 6 hours to obtain 2,4,6-tris(5-(tributyltinyl)thiophene-2-yl)-1,3,5-triazine, which is the modifier.

[0093] S4. Preparation of modified sweet potato vine-based nanocellulose:

[0094] Accurately weigh 6.0 g of the brominated sweet potato vine-based nanocellulose prepared in step S2 and place it in a dry three-necked flask. After purging with flowing nitrogen gas for 15 min, add 80 mL of nitrogen gas to the flask under a nitrogen atmosphere. A DMF / water mixed solvent (the volume ratio of DMF to deionized water is 7:3) was used. A magnetic stirrer was turned on and the mixture was stirred at 500 rpm for 30 min. The mixture was then sonicated at 300 W for 30 min to disperse the brominated sweet potato vine-based nanocellulose evenly in the reaction system. 2.4 g of the modifier prepared in step S3 was added to the reaction system and mixed evenly. Then, 240 mg of tetrakis(triphenylphosphine)palladium was added, and the reaction temperature was raised to 80 °C for coupling reaction. The reaction was carried out for 12 h. After the reaction was completed, the reaction system was naturally cooled to room temperature, centrifuged at 8000 rpm for 10 min, and the precipitate was collected. It was washed twice with 0.1 mol / L dilute hydrochloric acid aqueous solution, and then washed three times alternately with anhydrous ethanol and deionized water. Finally, it was vacuum dried at 60 °C for 12 h to obtain the modified sweet potato vine-based nanocellulose.

[0095] Preparation of Cu-Cu2O / modified sweet potato vine-based nanocellulose: 20 mL of ethylene glycol and 15 mL of anhydrous ethanol were placed in a flask and mixed evenly. 1.2 g of Cu(NO3)2·3H2O was added to the flask and stirred at 300 rpm until completely dissolved. The modified sweet potato vine-based nanocellulose prepared in step S4 was accurately weighed and added to the reaction system. The mixture was ultrasonically treated in an ultrasonic cell disruptor at 400 W for 30 min to fully disperse 6.0 g of the modified sweet potato vine-based nanocellulose. The reaction system was then transferred to a high-pressure reactor, sealed, and heated to 180 °C for hydrothermal reaction for 4 h. After the reaction was completed, the reaction system was allowed to cool naturally to room temperature. The system was then centrifuged at 8000 rpm for 10 min, and the precipitate was collected. It was washed three times with anhydrous ethanol and deionized water, and then vacuum dried at 60 °C for 12 h to obtain Cu-Cu2O / modified sweet potato vine-based nanocellulose.

[0096] S6. Pyrolysis treatment: Accurately weigh the Cu-Cu2O / modified sweet potato vine-based nanocellulose prepared in step S5 and place it in a quartz boat. After spreading it evenly, place the quartz boat in a tube furnace, seal the tube furnace, and purge with flowing nitrogen gas at a rate of 50 mL / min for 30 min. Then, increase the furnace temperature at a rate of 5 °C / min to 800 °C and hold it at this temperature for 2 h. After the pyrolysis treatment is completed, keep the reaction system under a nitrogen atmosphere and allow it to cool naturally to room temperature. Collect the pyrolysis products, grind them, and pass them through a 100-mesh sieve to obtain high-performance adsorbent biochar based on sweet potato vines.

[0097] Comparative Example 1

[0098] This comparative example provides a method for preparing high-performance adsorbent biochar. The only difference between this method and Example 1 is that step S5 is not included in the preparation method. Instead, the modified sweet potato vine-based nanocellulose prepared in step S4 is directly subjected to pyrolysis treatment. The pyrolysis parameters are the same as those in step S6 of Example 1, and the remaining components and component contents are the same as those in Example 1.

[0099] Comparative Example 2

[0100] This comparative example provides a method for preparing high-performance adsorbent biochar. The only difference between this method and Example 1 is that the preparation method does not include steps S2, S3, and S4. The sweet potato vine nanocellulose obtained in step S1 is reacted with Cu(NO3)2·3H2O in the manner described in step S5 to obtain Cu-Cu2O / sweet potato vine-based nanocellulose. Then, it is subjected to pyrolysis treatment in accordance with the method described in step S6. The remaining components and component contents are the same as in Example 1.

[0101] Application Example 1

[0102] This application example uses the high-performance adsorbent biochar based on sweet potato vines prepared in Examples 1-3 and Comparative Examples 1-2 for the adsorption of highly toxic and high-valence heavy metals. The high-performance adsorbent biochar prepared in Examples 1-3 and Comparative Examples 1-2 was dried in a vacuum drying oven at 60℃ for 24 hours until constant weight. After thorough grinding in an agate mortar, it was passed through a 100-mesh standard sieve and stored in a desiccator in a sealed, light-protected container. Before the experiment, 25.0 mL of 50 mg / L Cr(VI) standard working solution was quickly weighed and transferred to a 100 mL stoppered conical flask. 25 mL of ultrapure water was added, and the solution was shaken well to obtain 50 mL of a 25 mg / L Cr(VI) adsorption solution. The solution was then prepared with 0.1 mol / L HNO3 aqueous solution or 0.1 mol / L HNO3 aqueous solution. Adjust the pH of the solution to 2.5 with NaOH aqueous solution. Accurately weigh 0.02 g of pretreated high-performance adsorbent biochar and quickly add it to the above sample. Immediately seal the ground glass stopper and gently shake to disperse the biochar evenly. For the blank sample, do not add biochar and directly seal the stopper. Place all conical flasks in a constant temperature air bath shaker at 25℃ and 180 r / min, start the shaking, and record the starting time (t=0) to formally begin the adsorption reaction. Sample according to the set time gradient, covering the rapid adsorption stage, slow adsorption stage, and equilibrium stage. The specific time points are: 5, 10, 20, 30, 60, 90, 120, 180, 240, 360, 720, and 1440 min. Take 1 mL of the filtered filtrate from the above sample into a 25 mL stoppered colorimetric tube for colorimetric reaction. Measure the absorbance of the sample at 540 nm using a UV-Vis spectrophotometer. Calculate the actual concentration C of Cr(VI) in the sample using a standard working curve. t (mg / L), calculate the adsorption capacity according to the following formula ( (mg / g):

[0103] ;

[0104] Where C0 is the initial concentration (mg / L) of the Cr(VI) solution; C t t represents the equilibrium concentration of Cr(VI) at time t (mg / L); V represents the volume of the adsorption solution (L); and m represents the amount of biochar added (g).

[0105] Figure 1The figure shows the adsorption performance of the high-performance adsorbent biochar prepared in Examples 1-3 and Comparative Examples 1-2 of this invention on highly toxic high-valence heavy metals. As shown in the figure, regarding the equilibrium adsorption capacity, Example 2 has the highest equilibrium adsorption capacity at 59.4 mg / g, followed by Example 3 and Example 1. The equilibrium adsorption capacity of Comparative Example 1 is 14.2 mg / g, and that of Comparative Example 2 is 3.8 mg / g. The examples exhibit uniform structure, with CuN / CuS nanoparticles highly dispersed on the carbon framework surface and at the pore openings. Cr(VI) rapidly diffuses to the outer surface of the material under acidic conditions, undergoing a rapid redox reaction with CuN. The reduced Cr(III) immediately forms complexes with pyridine N and thiophene S on the surface, resulting in rapid occupation of the active sites on the outer surface within 60 min, thus causing a sharp increase in capacity. During the 60-360 min period, after the outer surface sites become saturated, Cr(VI) needs to diffuse through the membrane and within the particles to enter the hierarchical pores of the material, combining with the CuN / CuS particles and N / S heteroatoms within the pores. The mass transfer rate becomes the rate-determining step, thus the capacity increases slowly. The CuN / CuS reduction sites and N / S complexation sites on the material surface and within the pores are all occupied by Cr(VI) / Cr(III), reaching adsorption equilibrium. Comparative Example 1 is an N / S dual-heteroatom-doped porous carbon with no metal sites. It can only achieve physical adsorption and N / S complexation adsorption of Cr(VI), and cannot undergo reduction reactions. Lacking the strong reducing activity of CuN, it cannot convert water-soluble Cr(VI) into easily complexed Cr(III), and can only achieve adsorption through… The lone pair electrons of N / S form a weak coordination complex with Cr(VI), resulting in weak adsorption force and low site utilization. In Comparative Example 2, there are no dedicated heavy metal complexation sites, so the reduced Cr(III) cannot be effectively fixed and is easily desorbed. Furthermore, there are no heteroatoms to anchor the metal particles, leading to severe aggregation of CuO / Cu2O and insufficient exposure of active sites. The reduction activity of CuO / Cu2O is much lower than that of CuN, and without the support of electron conduction from a highly graphitized carbon framework, the reduction rate is extremely slow, resulting in the worst adsorption performance of Comparative Example 2.

[0106] Application Example 2

[0107] This application example uses the high-performance adsorbent biochar based on sweet potato vines prepared in Examples 1-3 and Comparative Examples 1-2 for the adsorption of heavy metal cations. The high-performance adsorbent biochar prepared in Examples 1-3 and Comparative Examples 1-2 was dried in a vacuum drying oven at 60℃ for 24 hours until constant weight. After thorough grinding in an agate mortar, it was passed through a 100-mesh standard sieve and stored in a desiccator in a sealed, light-protected container. Before the experiment, it was quickly weighed, and several 100mL stoppered conical flasks were taken. 50mL of Hg was accurately added to each flask. 2+ / Pb 2+ / Cd 2+Standard working solutions (concentrations of 20 mg / L, 80 mg / L, and 200 mg / L); adjust the pH of the solution to 5.0 by slowly adding 0.1 mol / L HNO3 aqueous solution or 0.1 mol / L NaOH aqueous solution, calibrating a precision pH meter; accurately weigh 0.02 g of the pretreated high-performance adsorbent biochar described in Examples 1-3 and Comparative Examples 1-2, and quickly add it to the stoppered conical flasks of the above three parallel samples; immediately tighten the ground glass stopper and gently shake to completely disperse the biochar in the solution; Hg 2+ The adsorption reaction flasks need to be wrapped with aluminum foil to protect them from light; no biochar is added to the blank sample, and the stopper is sealed directly; place all conical flasks in a constant temperature air bath shaker at 25℃ and 180r / min, start shaking, and allow the adsorption reaction to proceed for 24 hours. After the adsorption reaction reaches equilibrium after 24 hours, quickly remove all conical flasks from the shaker and immediately place them in a high-speed centrifuge at 8000rpm for 10min; after centrifugation, use a pipette to take 5mL of the supernatant, filter it through a 0.22μm aqueous filter membrane, and collect the filtrate into a clean test tube; Hg 2+ The filtrate was collected in a brown test tube, stored away from light, and ready for testing. After determining the sample concentration, the equilibrium adsorption capacity was calculated using the following formula ( (mg / g):

[0108] ;

[0109] Where C0 is the initial concentration (mg / L) of the heavy metal cation solution; C e V represents the concentration of heavy metal cations at adsorption equilibrium (mg / L); V is the volume of the adsorption solution (L); and m is the amount of biochar added (g).

[0110] Figure 2 The figure shows the adsorption performance of the high-performance adsorbent biochar prepared in Examples 1-3 and Comparative Examples 1-2 of this invention on heavy metal cations. As shown in the figure, the adsorption capacity and removal rate of the same material for the three ions all show the same trend. 2+ >Pb 2+ >Cd 2+ The pattern, CuS and Hg in Examples 1-3 2+ The irreversible chemical precipitation reaction that produces HgS is far stronger than ordinary complexation / electrostatic adsorption, resulting in a much higher Hg²⁺ adsorption capacity than Pb. 2+ / Cd 2+The main reason is that the complexation of N / S heteroatoms and the physical adsorption of porous carbon further enhance the removal effect of Hg²⁺. The performance gradient under the same ion and concentration is entirely due to the structural advantages / defects of the material. Example 2 has the best adsorption performance, while Comparative Example 1 and Comparative Example 2 have poor adsorption performance. Comparative Example 1 has no CuN / CuS metal sites and relies solely on the complexation of N / S heteroatoms and the physical adsorption of porous carbon. Comparative Example 2 has no dedicated heavy metal complexation sites and relies solely on the weak electrostatic adsorption of a small number of oxygen-containing functional groups. The adsorption force is extremely weak, CuO / Cu₂O is severely aggregated, the active site exposure is low, and CuO / Cu₂O does not have the special precipitation ability of CuS, which is detrimental to Hg²⁺ removal. 2+ Non-targeted adsorption.

[0111] Application Example 3

[0112] This application example utilizes the high-performance adsorbent biochar based on sweet potato vines prepared in Examples 1-3 and Comparative Examples 1-2 for the adsorption of organic pollutants. The high-performance adsorbent biochar prepared in Examples 1-3 and Comparative Examples 1-2 was dried in a vacuum drying oven at 60℃ for 24 hours until constant weight. After thorough grinding in an agate mortar, it was passed through a 100-mesh standard sieve and stored in a desiccator in a sealed, light-protected container. Before the experiment, it was quickly weighed, and several 100mL stoppered conical flasks were taken. 50mL of tetracycline (TC), rhodamine B (RhB), and methyl orange (MO) standard working solutions (concentrations of 20mg / L, 80mg / L, and 200mg / L) were accurately added to each flask. The solution was then diluted with 0.1mol / L HNO3 aqueous solution or 0.1mol / L HNO3 aqueous solution. Slowly add NaOH aqueous solution to adjust the pH of the solution to 5.0. Using a precision pH meter, accurately weigh 0.02 g of the pretreated high-performance adsorbent biochar described in Examples 1-3 and Comparative Examples 1-2, and quickly add it to the stoppered conical flasks of the above three parallel samples. Immediately seal the flasks with ground glass stoppers and gently shake to ensure complete dispersion of the biochar in the solution. If the RhB / TC adsorption reaction flask is made of ordinary glass, it needs to be double-wrapped with aluminum foil to protect it from light. For the blank sample, no biochar is added; simply seal the flask. Place all conical flasks in a constant-temperature, light-protected air bath shaker at 25°C and 180 r / min. Start the shaking and allow the adsorption reaction to proceed for 24 hours. After the adsorption reaction reaches equilibrium, quickly remove all conical flasks from the light-protected shaker and immediately place them in a high-speed centrifuge at 8000 rpm for 10 minutes. After centrifugation, use a pipette to collect 5 mL of the supernatant for testing. After determining the sample concentration, calculate the equilibrium adsorption capacity according to the formula shown in Application Example 2. (mg / g)

[0113] Figure 3The figures show the adsorption performance of the high-performance adsorbent biochar prepared in Examples 1-3 and Comparative Examples 1-2 of this invention for organic pollutants. As shown in the figures, the adsorption capacity and removal rate of the same material for the three organic pollutants exhibit the order RhB > TC > MO. RhB contains multiple conjugated aromatic rings, which form strong π-π stacking interactions with the triazine ring, thiophene ring, and aromatic ring structure of graphitized carbon in the biochar framework. The amino and hydroxyl groups of RhB form hydrogen bonds with N / S heteroatoms, and CuN / CuS has a highly efficient catalytic degradation effect on it. The superposition of these three effects results in the highest adsorption capacity and removal rate of RhB. Furthermore, it maintains a high removal rate even at high concentrations. TC contains benzene rings and naphthalene rings (π-π stacking sites), as well as polar groups such as amino, hydroxyl, and carbonyl groups, which can form stable hydrogen bonds with N / S heteroatoms and oxygen-containing functional groups in biochar. π-π stacking + hydrogen bonding is the main adsorption effect. TC has a larger molecular volume, and its diffusion rate within the pores is slightly slower than that of RhB, resulting in lower adsorption performance. MO is an anionic dye, exhibiting negative charge in a solution at pH=5.0. It has a slight repulsive force with the weakly negatively charged surface of biochar, relying only on a few positive potential points to form weak electrostatic adsorption, resulting in the lowest adsorption capacity and removal rate. Example 2 showed the best adsorption performance, while Comparative Examples 1 and 2 showed poor adsorption performance.

[0114] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention.

[0115] The present invention and its embodiments have been described above. This description is not restrictive, and the accompanying drawings are only one embodiment of the present invention. The actual application is not limited to this. In conclusion, if those skilled in the art are inspired by this description and design similar methods and embodiments without departing from the spirit of the present invention, they should all fall within the protection scope of the present invention.

Claims

1. A method for preparing high-performance adsorbent biochar based on sweet potato vines, characterized in that: Specifically, the following steps are included: S1. Preparation of sweet potato vine nanocellulose powder: Fresh sweet potato vines were treated with alkali to produce sweet potato vine-based nanocellulose powder. S2. Bromination treatment of sweet potato vine-based nanocellulose: The sweet potato vine-based nanocellulose powder prepared in step S1 is subjected to a nucleophilic substitution reaction with phosphorus tribromide using pyridine as an acid-binding agent to obtain brominated sweet potato vine-based nanocellulose. S3. Preparation of the modifier: Using 2-cyanothiophene as a reactant, an intermolecular cyanotricyclization reaction occurs under the catalysis of trifluoromethanesulfonic acid to form an intermediate with a triazine ring-thiophene structure, yielding 2,4,6-tris(thiophene-2-yl)-1,3,5-triazine; the thiophene group in 2,4,6-tris(thiophene-2-yl)-1,3,5-triazine is activated by n-butyllithium and tributyltin chloride to obtain a reactive modifier; S4. Preparation of modified sweet potato vine-based nanocellulose: Under the catalysis of tetra(triphenylphosphine)palladium, the brominated sweet potato vine-based nanocellulose prepared in step S2 is subjected to Stille cross-coupling reaction with the modifier prepared in step S3 to achieve covalent grafting of the modifier and sweet potato vine-based nanocellulose, thereby obtaining modified sweet potato vine-based nanocellulose. Preparation of S5, Cu-Cu2O / Modified Sweet Potato Vine-Based Nanocellulose: In the modified sweet potato vine-based nanocellulose described in step S4, the N in the triazine ring and the S in the thiophene ring affect the Cu... 2+ Its affinity for Cu makes it compatible with Cu 2+ Coordinate bonds are formed, and Cu is reduced by ethylene glycol. 2+ Reduced to Cu 0 Cu-Cu2O forms nanoparticles, which are then anchored on a modified sweet potato vine-based nanocellulose framework to obtain Cu-Cu2O / modified sweet potato vine-based nanocellulose. S6. Pyrolysis treatment: Through high-temperature pyrolysis treatment, Cu-Cu2O / modified sweet potato vine-based nanocellulose forms a porous carbon framework with micropores / mesoporous structures. The supported Cu-Cu2O undergoes a high-temperature hybridization reaction with N and S in the carbon framework to generate CuN and CuS nanoparticles, thus obtaining high-performance adsorbent biochar based on sweet potato vines.

2. The method for preparing a high-performance adsorbent biochar based on sweet potato vines according to claim 1, characterized in that: The preparation method of the sweet potato vine-based high-performance adsorbent biochar specifically includes the following steps: S1. Preparation of sweet potato vine nanocellulose powder: S11. Take fresh sweet potato vines, wash them, cut them into 3-5cm sections, dry them until completely dry, grind them in a grinder and then sieve them to obtain sweet potato vine powder. S12. Accurately weigh the sweet potato vine powder prepared in step S11 and disperse it in NaOH aqueous solution. Raise the reaction temperature to carry out alkaline hydrolysis. After the reaction is completed, wait for the reaction system to cool naturally to room temperature, filter, collect the filter cake and wash it to obtain sweet potato vine crude fiber. S13. Disperse the sweet potato vine crude fiber prepared in step S12 in deionized water, and perform high-speed shearing and homogenization treatment in sequence. Centrifuge, take the supernatant for dialysis, freeze dry, and obtain sweet potato vine-based nanocellulose powder. S2. Bromination treatment of sweet potato vine-based nanocellulose: After drying the sweet potato vine-based nanocellulose powder prepared in step S13, it was dispersed in anhydrous dichloromethane, phosphorus tribromide and pyridine were added, and after mixing evenly, a bromination reaction was carried out. After the reaction was completed, it was cooled, slowly transferred to ice water for quenching, filtered, the solid was collected, washed, and dried to obtain brominated sweet potato vine-based nanocellulose. S3. Preparation of the modifier: S31. Dissolve 2-cyanothiophene in anhydrous chloroform and transfer it to an ice-water bath. Add trifluoromethanesulfonic acid dropwise while maintaining the ice-water bath conditions. After continuous stirring and mixing, carry out a trimerization reaction at room temperature. After the reaction is complete, wash three times with deionized water, collect the organic phase, dry it to remove water, and then distill under reduced pressure, purify, and dry it to obtain 2,4,6-tris(thiophene-2-yl)-1,3,5-triazine. S32. Dissolve the 2,4,6-tris(thiophen-2-yl)-1,3,5-triazine obtained in step S31 in anhydrous THF, transfer it to a dry ice-acetone bath, add n-butyllithium to carry out the lithiation reaction. After the reaction is completed, maintain the dry ice-acetone bath conditions, add tributyltin chloride, heat to room temperature, and continuously stir to carry out the tinification reaction. After the reaction is completed, slowly pour it into a saturated ammonium chloride aqueous solution for quenching, add anhydrous diethyl ether for extraction, combine the organic phases, wash the organic layer with saturated NaCl aqueous solution and deionized water, dry to remove water, and after vacuum distillation, purification, and drying, obtain 2,4,6-tris(5-(tributyltinyl)thiophen-2-yl)-1,3,5-triazine, which is the modifier; S4. Preparation of modified sweet potato vine-based nanocellulose: The brominated sweet potato vine-based nanocellulose prepared in step S2 was dispersed in a DMF / water mixed solvent, the modifier prepared in step S3 was added, and after continuous mixing, tetra(triphenylphosphine)palladium was added, and the reaction temperature was increased to carry out the coupling reaction. After the reaction was completed, the mixture was cooled, centrifuged, the precipitate was collected, washed, and dried to obtain modified sweet potato vine-based nanocellulose. S5. Preparation of Cu-Cu2O / modified sweet potato vine-based nanocellulose: Ethylene glycol and anhydrous ethanol were mixed, Cu(NO3)2·3H2O was added, and the modified sweet potato vine-based nanocellulose prepared in step S4 was added. After mixing evenly, the mixture was transferred to a high-pressure reactor, sealed, and the temperature was raised to carry out a hydrothermal reaction. After the reaction was completed, the mixture was cooled, centrifuged, and the precipitate was collected. After washing and drying, Cu-Cu2O / modified sweet potato vine-based nanocellulose was obtained. S6. Pyrolysis treatment: The Cu-Cu2O / modified sweet potato vine-based nanocellulose prepared in step S5 is placed in a tube furnace, sealed, and flowing nitrogen is introduced to raise the temperature inside the furnace for pyrolysis treatment. After completion, it is cooled, the pyrolysis products are collected, ground, and sieved to obtain high-performance adsorbent biochar based on sweet potato vines.

3. The method for preparing a high-performance adsorbent biochar based on sweet potato vines according to claim 2, characterized in that: In step S12, the solid-liquid ratio between the sweet potato vine powder and the NaOH aqueous solution is 1g:15-20mL; the mass fraction of NaOH in the NaOH aqueous solution is 3%-5%; in step S12, the alkaline hydrolysis temperature is 90-100℃, and the alkaline hydrolysis time is 2-3h. In step S13, the shearing speed of the high-speed shearing process is 10,000-12,000 rpm, and the high-speed shearing time is 3-5 min; the working pressure of the homogenization process is 70-80 MPa, and the number of homogenization cycles is 6-8.

4. The method for preparing a high-performance adsorbent biochar based on sweet potato vines according to claim 3, characterized in that: In step S2, the solid-liquid ratio between the sweet potato vine-based nanocellulose powder and phosphorus tribromide is 1g:0.9-1.3mL; the solid-liquid ratio between the sweet potato vine-based nanocellulose powder and pyridine is 1g:0.8-1.2mL; the reaction temperature of the bromination reaction is 30-40℃, and the reaction time of the bromination reaction is 4-6h.

5. The method for preparing a high-performance adsorbent biochar based on sweet potato vines according to claim 4, characterized in that: In step S31, the volume ratio between 2-cyanothiophene and trifluoromethanesulfonic acid is 1:3.8-4.3; the reaction time for the trimerization reaction is 40-50 h.

6. The method for preparing a high-performance adsorbent biochar based on sweet potato vines according to claim 5, characterized in that: In step S32, the molar ratio between 2,4,6-tris(thiophen-2-yl)-1,3,5-triazine and n-butyllithium and tributyltin chloride is 1:3.3-3.5:3.1-3.3; the reaction time for lithiation is 1-2 h, and the reaction time for tinning is 6-8 h.

7. The method for preparing a high-performance adsorbent biochar based on sweet potato vines according to claim 6, characterized in that: In step S4, the mass ratio of the brominated sweet potato vine-based nanocellulose to the modifier is 1:0.2-0.4; the reaction temperature of the coupling reaction is 70-80℃, and the reaction time of the coupling reaction is 12-16h.

8. The method for preparing a high-performance adsorbent biochar based on sweet potato vines according to claim 7, characterized in that: In step S5, the volume ratio between ethylene glycol and anhydrous ethanol is 4-5:3-4; in step S5, the mass ratio between the modified sweet potato vine-based nanocellulose and Cu(NO3)2·3H2O is 1:0.2-0.3; in step S5, the hydrothermal reaction temperature is 160-180℃, and the hydrothermal reaction time is 4-6h.

9. The method for preparing a high-performance adsorbent biochar based on sweet potato vines according to claim 8, characterized in that: In step S6, the pyrolysis temperature of the pyrolysis treatment is 700-800℃, and the pyrolysis time is 2-3h.

10. An application of a high-performance adsorbent biochar based on sweet potato vines prepared by the preparation method according to any one of claims 1-9, characterized in that: Specifically, this includes the adsorption of heavy metal ions and organic pollutants; the organic pollutants include at least one of tetracycline, rhodamine B, and methyl orange.

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