CN111748109B - Chitosan microspheres prepared from chitosan solution with pH value of 6-8 and preparation method thereof - Google Patents

Chitosan microspheres prepared from chitosan solution with pH value of 6-8 and preparation method thereof Download PDF

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CN111748109B
CN111748109B CN201910248697.7A CN201910248697A CN111748109B CN 111748109 B CN111748109 B CN 111748109B CN 201910248697 A CN201910248697 A CN 201910248697A CN 111748109 B CN111748109 B CN 111748109B
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chitosan
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CN111748109A (en
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蔡杰
钟奕
张俐娜
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Wuhan University WHU
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    • C08B37/00—Preparation of polysaccharides not provided for in groups C08B1/00 - C08B35/00; Derivatives thereof
    • C08B37/0006—Homoglycans, i.e. polysaccharides having a main chain consisting of one single sugar, e.g. colominic acid
    • C08B37/0024—Homoglycans, i.e. polysaccharides having a main chain consisting of one single sugar, e.g. colominic acid beta-D-Glucans; (beta-1,3)-D-Glucans, e.g. paramylon, coriolan, sclerotan, pachyman, callose, scleroglucan, schizophyllan, laminaran, lentinan or curdlan; (beta-1,6)-D-Glucans, e.g. pustulan; (beta-1,4)-D-Glucans; (beta-1,3)(beta-1,4)-D-Glucans, e.g. lichenan; Derivatives thereof
    • C08B37/0027—2-Acetamido-2-deoxy-beta-glucans; Derivatives thereof
    • C08B37/003—Chitin, i.e. 2-acetamido-2-deoxy-(beta-1,4)-D-glucan or N-acetyl-beta-1,4-D-glucosamine; Chitosan, i.e. deacetylated product of chitin or (beta-1,4)-D-glucosamine; Derivatives thereof
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    • C08J3/02—Making solutions, dispersions, lattices or gels by other methods than by solution, emulsion or suspension polymerisation techniques
    • C08J3/03—Making solutions, dispersions, lattices or gels by other methods than by solution, emulsion or suspension polymerisation techniques in aqueous media
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    • C08J2305/00—Characterised by the use of polysaccharides or of their derivatives not provided for in groups C08J2301/00 or C08J2303/00
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    • C08J2405/00—Characterised by the use of polysaccharides or of their derivatives not provided for in groups C08J2401/00 or C08J2403/00
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    • C08K7/00—Use of ingredients characterised by shape

Abstract

The invention discloses a microsphere material prepared by using a chitosan solution with a pH value of 6-8 and a preparation method thereof. The preparation method comprises the following steps: (1) preparing a dispersion liquid; (2) adding chitosan into the dispersion liquid, controlling the temperature to be between the freezing point and 35 ℃, introducing carbon dioxide into the solution, simultaneously stirring to dissolve the chitosan, stopping introducing the carbon dioxide after the chitosan is completely dissolved, and defoaming to obtain a transparent chitosan solution with the pH value of 6-8; (3) the chitosan aqueous solution and the oil phase form chitosan emulsion drops through a membrane emulsifier or a micro-fluidic device or a conventional stirring device, and the chitosan microspheres are formed after the emulsion drops are solidified through a coagulant or a chemical cross-linking agent. The invention has the beneficial effects that: the method for preparing the chitosan microspheres is carried out in the environment with the pH value of 6-8, so that the degradation of chitosan molecular chains can be effectively weakened; the process for preparing the chitosan microspheres is green and environment-friendly, and is beneficial to improving the production efficiency and reducing the production cost.

Description

Chitosan microspheres prepared from chitosan solution with pH value of 6-8 and preparation method thereof
Technical Field
The invention belongs to the field of natural polymers, and particularly relates to chitosan microspheres prepared from a chitosan solution with a pH value of 6-8 and a preparation method thereof.
Background
The chitosan is a deacetylated product of chitin, and when the deacetylation degree of the chitin is more than 55%, the chitin is converted into chitosan which can be dissolved in an acidic aqueous solution. The chitosan has good biocompatibility and biodegradability, can promote wound healing, and has hemostatic effect. The chitosan solution obtained by dissolving the chitosan can be used for preparing new materials such as chitosan fiber, chitosan film, chitosan hydrogel, chitosan aerogel, chitosan microspheres and the like, and has good application prospect in the fields of separation and adsorption, biomedical materials, flexible electronic devices, heat insulation materials and the like.
Chitosan has a large number of hydrogen bonds both intra-and intermolecular, and is therefore difficult to dissolve in water and common organic solvents. The traditional method is to use low-concentration acetic acid or hydrochloric acid aqueous solution to dissolve chitosan, but chitosan is easy to degrade molecular chains of chitosan in acidic aqueous solution. Recently, some alkaline aqueous solvents have been developed to dissolve chitosan. The current alkaline aqueous solvents used to dissolve chitosan include lithium hydroxide-sodium hydroxide-urea combination (patent 201110099176.3), lithium hydroxide-potassium hydroxide-urea combination (patent 201310405191.5), sodium hydroxide-urea combination (Zhang W, Xia W.Disolution and stability of lithium hydroxide/urea aqueous solution [ J ]. Journal of Applied Polymer Science,2014,131(3): 1082. alpha. 1090.) and lithium hydroxide-urea combination (Li C, Han Q, Guan Y, et al. Michael reaction of chitosan with acrylic acid in aqueous solution of alkali-urea solution [ J ]. Polymer Bulletin,2015,72(8): 2087. alpha. 5.). The specific dissolving method is that firstly the chitosan is added into the alkaline hydrosolvents for soaking, then the mixture is frozen and frozen, finally the mixture is unfrozen and stirred at room temperature, and the chitosan is completely dissolved after one or more times of freezing-unfreezing. The freezing-thawing process consumes a large amount of energy, which is very disadvantageous for industrial applications, and thus, the efficiency of preparing the chitosan alkaline aqueous solution is to be improved.
Besides acid and alkaline water solvents, reports about the water solvent with the pH value of 6-8 for dissolving chitosan are blank. Compared with a strong alkaline aqueous solvent and an acidic aqueous solvent, the chitosan is more stable in the aqueous solvent with the pH value of 6-8, and the degradation of chitosan molecular chains is not easy to occur.
The chitosan is dissolved under the acidic or alkaline condition, and the solution thereof can have the problem of further degradation of the chitosan in the process of treatment or processing. In addition, acid and alkali substances still remain in the microspheres during preparation and processing, which may cause degradation of the chitosan microspheres during use and affect the performance of the chitosan microspheres.
Disclosure of Invention
In order to solve the technical problem, the invention provides a method for preparing a chitosan microsphere material based on a chitosan solution prepared by dissolving chitosan at a pH value of 6-8.
The method enables the chitosan to be dissolved in the environment with the pH value of 6-8, can effectively reduce the degradation of chitosan molecules, and enables the formed chitosan solution to be more stable. Because the solution does not contain acid and alkali, acidic or alkaline substances can not be remained in the subsequent microsphere preparation process, the stability is better, the degradation and aging are slower in the using process, and the solution can still keep better performance after long-term use. On one hand, the prepared chitosan microsphere material is widely applied to the fields of drug controlled release materials, adsorption materials and the like as a substitute of the traditional microsphere material; on the other hand, the microsphere chitosan serving as a carrier has potential application in the fields of catalysis and the like. The carbon microsphere doped with nitrogen element obtained by carbonizing the chitosan microsphere with the shell has wide application in batteries and capacitors. Functional groups or materials can be introduced in the preparation process of the chitosan microspheres, so that the functionality of the chitosan microspheres is increased, and the application range is expanded.
The specific scheme provided by the invention is as follows:
the first aspect provides a chitosan microsphere material prepared from chitosan with a pH value of 6-8 and a preparation method thereof.
The preparation method comprises the following steps:
(1) preparing a dispersion liquid;
(2) adding chitosan into the dispersion liquid, controlling the temperature to be between the freezing point and 35 ℃, introducing carbon dioxide into the solution, simultaneously stirring to dissolve the chitosan, stopping introducing the carbon dioxide after the chitosan is completely dissolved, and defoaming to obtain a transparent chitosan solution with the pH value of 6-8;
(3) preparing a chitosan microsphere material: and (3) forming chitosan emulsion drops by passing the chitosan aqueous solution and the oil phase obtained in the step (2), and solidifying the emulsion drops by a coagulant or a chemical cross-linking agent to form the chitosan microspheres.
Specifically, the dispersion is one or a mixture of two of a urea aqueous solution and a thiourea aqueous solution. The concentration of the urea aqueous solution is 6-60 wt%; preferably, the concentration of the urea aqueous solution is 18 to 60 wt%. The concentration of the thiourea aqueous solution is 3-14 wt%, preferably, the concentration of the thiourea aqueous solution is 7-14 wt%.
Specifically, the mass ratio of the chitosan to the dispersion liquid in the step (2) is 1: 7-1: 1000. Preferably, the mass ratio of the chitosan to the dispersion liquid is 1:7 to 1: 100.
Specifically, the oil phase in the step (3) is composed of an oily substance which is liquid at normal temperature and an oil-soluble emulsifier; the chitosan emulsion droplet forming method comprises emulsification by using a stirring device, a microfluidic device or a membrane emulsifier.
Further, the above oily substance is selected from liquid paraffin, petroleum ether, olive oil, cotton seed oil, soybean oil or sunflower seed oil; the oily emulsifier must be one which is soluble in the oily substance used and is selected from sorbitan sesquioleate (Arlace183), polymers of glyceryl ethers (such as PO-500, PO-310), polyoxyethylene hydrogenated castor oil, sorbitan trioleate (span 85), sorbitan monooleate (span 80), sorbitan tristearate (span 65), tween 80 or lipophilic-hydrophilic block copolymers. The mass concentration of the emulsifier in the oil phase is 0.5-10 wt%.
Specifically, the volume ratio of the chitosan aqueous solution to the oil phase in the step (3) in the preparation method is 1: 1-1: 1000, and preferably 1: 2-1: 100.
And further. The method for forming emulsion droplets by using the membrane emulsifier is characterized in that a chitosan aqueous solution (water phase) is pressed into an oil phase through a microporous membrane by using pressure to obtain emulsion droplets with uniform size; the method for forming the emulsion drop by utilizing the microfluidic device is characterized in that a micro-pump is used for conveying an oil phase and a water phase to two crossed channels in a customized microfluidic chip, and the oil phase is used as a continuous phase to separate the water phase to form a monodisperse emulsion drop; the method of forming the emulsion droplets using a conventional stirring apparatus is to mix an oil phase and an aqueous phase, and then mechanically stir them to disperse the aqueous phase into the oil phase to form the emulsion droplets.
Specifically, the crosslinking agent in step (3) includes aldehyde crosslinking agent, glycidyl ether crosslinking agent, epoxy compound, iridoid, and polyphenol, preferably glutaraldehyde, epichlorohydrin, genipin, and procyanidin. The molar ratio of the cross-linking agent to the chitosan is 0.1-10. The adopted coagulator is microspheres formed by a physical crosslinking mode, and is one or more of mixed aqueous solution of amide, dimethyl sulfoxide, ethyl acetate, acetone, alcohols, salts and acid. Preferably, the salt is selected from ammonium salt, sodium salt, potassium salt, magnesium salt, calcium salt and aluminum salt, and the concentration is 5-40 wt%. Preferably, the alcohol is selected from methanol and ethanol. The concentration is 10-100 wt%.
In a second aspect, a multifunctional chitosan microsphere and a preparation method thereof are provided.
The preparation method comprises the following steps: functional organic or inorganic additives and low-dimensional nano materials are introduced in the process of preparing the chitosan microspheres, or natural macromolecules or synthetic macromolecules are introduced for blending.
Specifically, the functional organic or inorganic additive is selected from one or more of a plasticizer, a reinforcing agent, a refractory material additive, a dye, an optical stabilizer, an antibacterial bacteriostatic agent, a conductive material and a surfactant.
Further, the low-dimensional nano material comprises graphene and derivatives thereof, carbon nanotubes and derivatives thereof, metal or metal oxide nanoparticles, an organic framework compound or molybdenum disulfide. The natural polymer or synthetic polymer is selected from polymer nanofiber, animal protein, vegetable protein, alginate, collagen, cellulose and its derivatives, conductive polymer, polyvinyl alcohol or polyethylene glycol.
In a third aspect, a method for preparing nitrogen-doped carbon aerogel microspheres is provided: and (3) carrying out heat treatment on the chitosan microspheres or the functional chitosan microspheres at the temperature of more than 150 ℃ under the protection of inert gas atmosphere to obtain the carbon aerogel microspheres.
The invention has the beneficial effects that:
(1) the dissolving method provided by the invention is carried out in an environment with a pH value of 6-8, so that the degradation of chitosan molecules can be effectively reduced, and the stability of chitosan in the dissolving process is high;
(2) the chitosan dissolution process is efficient, energy-saving, green and environment-friendly, is beneficial to improving the production efficiency and reducing the production cost, and can be used for large-scale production;
(3) the prepared chitosan solution has a pH value of 6-8, is high in stability as a raw material of fiber, has no acid and alkaline substance residues in the process of preparing microspheres and the use of the microspheres as products, and fills the blank of the method for preparing the chitosan microsphere material by using the chitosan solution with the pH value of 6-8;
(4) on one hand, the prepared chitosan microsphere material is widely applied to the fields of drug controlled release materials, adsorption materials and the like as a substitute of the traditional microsphere material; on the other hand, the microsphere chitosan serving as a carrier has potential application in the field of catalysis. In addition, the nitrogen-doped carbon microspheres obtained after carbonization can be widely applied to the fields of batteries and capacitors. Functional groups or materials can be introduced in the preparation process of the chitosan microspheres, so that the functionality of the chitosan microspheres is increased, and the application range is expanded.
Detailed Description
The invention will be further illustrated with reference to specific examples, to which the present invention is not at all restricted.
The chitosan used in the following examples is extracted from natural shrimp shell, crab shell, squid parietal bone, diatom, insects and other organisms containing alpha-chitin and beta-chitin, and the specific extraction steps are soaking with alkaline solution to remove protein, soaking with acid solution to remove inorganic salt, decolorizing with oxidant, washing with water and drying to obtain purified chitin. The chitosan is prepared by deacetylation reaction of chitin in sodium hydroxide or potassium hydroxide aqueous solution.
Example 1
Soaking shrimp shell in alkali solution to remove protein, soaking in acid solution to remove inorganic salt, and decolorizing with hydrogen peroxide water solution to obtain purified chitin. Heating chitin in 50 wt% sodium hydroxide water solution for 1h to perform deacetylation reaction, and obtaining chitosan with deacetylation degree of about 70%.
An aqueous urea solution having a concentration of 6 wt% was used as the dispersion. Mixing chitosan and dispersion liquid according to the mass ratio of 1:7, introducing carbon dioxide into the mixture at 35 ℃, stirring, stopping introducing the carbon dioxide after the chitosan is completely dissolved, obtaining a transparent chitosan solution after centrifugal deaeration, and enabling part of chitosan insoluble substances to be arranged at the bottom of a centrifugal tube. And (3) preparing the chitosan microsphere material by using the chitosan solution after insoluble substances are removed.
Mixing chitosan stock solution and 2 times volume ratio of oil phase (containing 0.5 wt% span 80 liquid paraffin), mixing chitosan monomer and epoxy chloropropane with molar ratio of 1:10, stirring at 800rpm for 1h to form the microsphere. And pouring the obtained microspheres into an ethanol aqueous solution with the alcohol content of 10wt% for regeneration, centrifuging, taking the precipitate, washing the precipitate with petroleum ether, acetone, ethanol, acetone and water in sequence, and freeze-drying to obtain the chitosan microspheres. And observing the morphology of the chitosan microspheres by using a scanning electron microscope, and counting the diameters of the microspheres to obtain the average size of 22 microns. The BET specific surface area is 350m by nitrogen adsorption2/g。
Example 2
Soaking crab shell with alkali solution to remove protein, soaking with acid solution to remove inorganic salt, and decolorizing with hydrogen peroxide solution to obtain purified chitin. Heating chitin in 55 wt% potassium hydroxide water solution for 2h to perform deacetylation reaction, and obtaining chitosan with deacetylation degree of about 60%.
An aqueous urea solution having a concentration of 18 wt% was used as the dispersion. Mixing chitosan and dispersion liquid according to the mass ratio of 1:1000, introducing carbon dioxide into the mixture at 20 ℃, stirring, stopping introducing the carbon dioxide after the chitosan is completely dissolved, obtaining a transparent chitosan solution after centrifugal deaeration, and enabling a small part of chitosan insoluble substances to be arranged at the bottom of a centrifugal tube. And (3) preparing the chitosan microsphere material by using the chitosan solution after insoluble substances are removed.
The hydrophobic membrane with pore size of 4.7 microns was soaked in petroleum ether to wet the porous membrane sufficiently to ensure that the hydrophobic membrane on the membrane was completely spread. Adding span 85 into 1L mixed oil phase of liquid paraffin and petroleum ether, and stirring toCompletely dissolved as an oil phase (the volume ratio of the liquid paraffin to the petroleum ether is 1:1, and the oil phase contains 1 wt% of span 85). 100g of chitosan solution is pressed into the oil phase through a hydrophobic microporous membrane with uniform pore diameter under pressure to obtain chitosan emulsion. Adding chitosan monomer and glutaraldehyde with the molar ratio of 1:1 to the emulsion, mixing, and stirring at the rotating speed of 300rpm for 2h to form microspheres. Washing the obtained microspheres with petroleum ether, acetone, ethanol and acetone in sequence, washing with water, and freeze-drying to obtain the chitosan microspheres. And observing the morphology of the chitosan microspheres by using a scanning electron microscope, and counting the diameters of the microspheres, wherein the average size of the microspheres is 16 microns. The BET specific surface area is 325m by nitrogen adsorption2/g。
Example 3
Soaking squid bones in alkali liquor to remove proteins, and soaking in acid liquor to remove inorganic salts to obtain purified chitin. Heating chitin in 56 wt% potassium hydroxide water solution for 2h to perform deacetylation reaction, and obtaining chitosan with deacetylation degree of about 60%.
An aqueous urea solution having a concentration of 60wt% was used as the dispersion. Mixing chitosan and dispersion liquid according to the mass ratio of 1:100, introducing carbon dioxide into the mixture at 0 ℃, stirring, stopping introducing the carbon dioxide after the chitosan is completely dissolved, and obtaining a transparent chitosan solution after centrifugal deaeration, wherein no chitosan insoluble substances exist at the bottom of a centrifuge tube. The chitosan solution is used for preparing the chitosan microsphere material.
The hydrophobic membrane with the aperture of 13 microns is soaked in petroleum ether, so that the porous membrane is sufficiently wetted to ensure that the hydrophobic link on the membrane is completely spread. Adding an oil-soluble emulsifier into a mixed oil phase of 1L of liquid paraffin and petroleum ether, and stirring until the oil-soluble emulsifier is completely dissolved to be used as an oil phase (the volume ratio of the liquid paraffin to the petroleum ether is 1:1, and the oil phase contains 1 wt% of span 85). 100g of chitosan solution is pressed into the oil phase through a hydrophobic microporous membrane with uniform pore diameter under pressure to obtain chitosan emulsion. Adding chitosan monomer and genipin with the molar ratio of 1:10 into the emulsion, mixing, and stirring at 300rpm for 2h to form microspheres. Pouring the obtained microspheres into 80 wt% ethanol water solution for regeneration, centrifuging, collecting precipitate, and adding petroleum ether and acetoneAnd respectively washing ketone, ethanol, acetone and water, and freeze-drying to obtain the chitosan microspheres. And observing the morphology of the chitosan microspheres by using a scanning electron microscope, and counting the diameters of the microspheres, wherein the average size of the microspheres is 32 microns. The BET specific surface area is 410m by nitrogen adsorption2/g。
Example 4
Soaking shrimp shell in alkali solution to remove protein, soaking in acid solution to remove inorganic salt, and decolorizing with hydrogen peroxide water solution to obtain purified chitin. Heating chitin in 48 wt% sodium hydroxide water solution for 2h to perform deacetylation reaction, and obtaining chitosan with deacetylation degree of about 70%.
An aqueous solution of thiourea having a concentration of 3% by weight was used as a dispersion. Mixing chitosan and dispersion liquid according to the mass ratio of 1:7, introducing carbon dioxide into the mixture at 35 ℃, stirring, stopping introducing the carbon dioxide after the chitosan is completely dissolved, and obtaining a transparent chitosan solution after centrifugal deaeration, wherein no chitosan insoluble substances exist at the bottom of a centrifuge tube. The chitosan solution is used for preparing the chitosan microsphere material.
The hydrophobic membrane with a pore size of 19 microns was soaked in petroleum ether to wet the porous membrane sufficiently to ensure that the hydrophobic chains on the membrane were completely spread. Adding span 80 into 1L of mixed oil phase of liquid paraffin and petroleum ether, and stirring until the mixture is completely dissolved to obtain an oil phase (the volume ratio of the liquid paraffin to the petroleum ether is 1:1, and the oil phase contains 5 wt% of span 80). 100g of chitosan solution is pressed into the oil phase through a hydrophobic microporous membrane with uniform pore diameter under pressure to obtain chitosan emulsion. Adding chitosan monomer and genipin with the molar ratio of 1:0.1 into the emulsion, mixing, and stirring at 300rpm for 2h to form microspheres. And pouring the obtained microspheres into an ethanol aqueous solution with the alcohol content of 90 wt% for regeneration, centrifuging, taking the precipitate, washing the precipitate with petroleum ether, acetone, ethanol, acetone and water in sequence, and freeze-drying to obtain the chitosan microspheres. And observing the morphology of the chitosan microspheres by using a scanning electron microscope, and counting the diameters of the microspheres to obtain the average size of 55 microns. The BET specific surface area is 350m by nitrogen adsorption2/g。
Example 5
Soaking crab shell with alkali solution to remove protein, soaking with acid solution to remove inorganic salt, and decolorizing with hydrogen peroxide water solution to obtain purified chitin. Heating chitin in a sodium hydroxide aqueous solution with the mass molar concentration of 48 wt% for 2h to perform deacetylation reaction, and obtaining chitosan with the deacetylation degree of about 60%.
An aqueous solution of thiourea having a concentration of 7% by weight was used as a dispersion. Mixing chitosan and dispersion liquid according to the mass ratio of 1:1000, introducing carbon dioxide into the mixture at 20 ℃, stirring, stopping introducing the carbon dioxide after the chitosan is completely dissolved, obtaining a transparent chitosan solution after centrifugal deaeration, and enabling a small part of chitosan insoluble substances to be arranged at the bottom of a centrifugal tube. And (3) preparing the chitosan microsphere material by using the chitosan solution after insoluble substances are removed.
Adding span 80 into 1L of mixed oil phase of liquid paraffin and petroleum ether, and stirring until the mixture is completely dissolved to obtain an oil phase (the volume ratio of the liquid paraffin to the petroleum ether is 1:1, and the oil phase contains 10wt% of span 80). Conveying the chitosan solution and the oil phase to a customized micro-fluidic chip (the diameter of an oil-phase channel in the chip is 350 microns, and the diameter of a water-phase channel in the chip is 16 microns) through a micro-pump to form monodisperse liquid drops; placing the collected liquid drops into a magnesium chloride solution with the salt content of 40 wt% for gelation, and removing the organic solvent; and pouring the obtained microspheres into a methanol water solution with the water content of 70 wt% for regeneration, centrifuging, taking the precipitate, washing the precipitate with petroleum ether, acetone, ethanol, acetone and water in sequence, and freeze-drying to obtain the chitosan microspheres. And observing the morphology of the chitosan microspheres by using a scanning electron microscope, and counting the diameters of the microspheres, wherein the average size of the microspheres is 42 microns. The BET specific surface area of the nitrogen gas adsorption material is 395m2/g。
Example 6
Soaking the top bone of the squid in alkali liquor to remove protein, and soaking in acid liquor to remove inorganic salt to obtain purified chitin. Heating chitin in 45 wt% sodium hydroxide water solution for 2h to perform deacetylation reaction, and obtaining chitosan with deacetylation degree of about 70%.
An aqueous thiourea solution having a concentration of 14% by weight was used as a dispersion. Mixing chitosan and dispersion liquid according to the mass ratio of 1:100, introducing carbon dioxide into the mixture at 0 ℃, stirring, stopping introducing the carbon dioxide after the chitosan is completely dissolved, and obtaining a transparent chitosan solution after centrifugal deaeration, wherein no chitosan insoluble substances exist at the bottom of a centrifuge tube. The chitosan solution is used for preparing the chitosan microsphere material.
Adding span 80 into 1L of mixed oil phase of liquid paraffin and petroleum ether, and stirring until the mixture is completely dissolved to obtain an oil phase (the volume ratio of the liquid paraffin to the petroleum ether is 1:1, and the oil phase contains 1 wt% of span 80). Conveying the chitosan solution and the oil phase to a customized micro-fluidic chip (the diameter of an oil-phase channel in the chip is 350 microns, and the diameter of a water-phase channel in the chip is 30 microns) through a micro-pump to form monodisperse droplets; placing the collected liquid drops into a magnesium chloride solution with the salt content of 20 wt% for gelation, and removing the organic solvent; and pouring the obtained microspheres into an ethanol aqueous solution with the alcohol content of 100 wt% for regeneration, centrifuging, taking the precipitate, washing the precipitate with petroleum ether, acetone, ethanol, acetone and water in sequence, and freeze-drying to obtain the chitosan microspheres. And observing the morphology of the chitosan microspheres by using a scanning electron microscope, and counting the diameters of the microspheres to obtain the average size of 41 microns. The BET specific surface area is 382m by nitrogen adsorption2/g。
Example 7
An aqueous solution of 10wt% urea to 7 wt% thiourea was used as a dispersion. Mixing chitosan and dispersion liquid according to the mass ratio of 1:100, introducing carbon dioxide into the mixture at 35 ℃, stirring, stopping introducing the carbon dioxide after the chitosan is completely dissolved, and obtaining a transparent chitosan solution after centrifugal deaeration, wherein no chitosan insoluble substances exist at the bottom of a centrifuge tube. The chitosan solution is used for preparing the chitosan microsphere material.
Adding span 85 into 1L of mixed oil phase of liquid paraffin and petroleum ether, and stirring until the mixture is completely dissolved to obtain oil phase (the volume ratio of the liquid paraffin to the petroleum ether is 1:1, and the oil phase contains 1 wt% of span 85). Conveying the chitosan solution and the oil phase to a customized T-shaped micro-fluidic chip (the diameter of an oil-phase channel in the chip is 350 microns, and the diameter of a water-phase channel in the chip is 50 microns) through a micro-pump to form monodisperse liquid drops; placing the collected liquid drop in magnesium chloride solution with salt content of 20 wt% for gelation, and removing organic substancesA solvent; and pouring the obtained microspheres into an ethanol water solution with the water content of 50 wt% for regeneration, centrifuging, taking the precipitate, washing the precipitate with petroleum ether, acetone, ethanol, acetone and water in sequence, and freeze-drying to obtain the chitosan microspheres. And observing the morphology of the chitosan microspheres by using a scanning electron microscope, and counting the diameters of the microspheres to obtain the average size of 75 microns. The BET specific surface area is 430m by nitrogen adsorption2/g。
Example 8
An aqueous urea solution having a concentration of 20 wt% was used as the dispersion. Mixing chitosan and dispersion liquid according to the mass ratio of 1:10, introducing carbon dioxide into the mixture at 25 ℃, stirring, stopping introducing the carbon dioxide after the chitosan is completely dissolved, and obtaining a transparent chitosan solution after centrifugal deaeration, wherein no chitosan insoluble substances exist at the bottom of a centrifugal tube.
Mixing chitosan stock solution and 5 times volume ratio of oil phase (olive oil and Tween 80, wherein the concentration of Tween 80 is 0.5 wt%) which is equivalent to procyanidin with 1 time molar ratio of chitosan monomer, and stirring at 1000rpm for 2h to form microspheres. And pouring the obtained microspheres into a magnesium chloride aqueous solution with the salt concentration of 40 wt% for regeneration, centrifuging, taking precipitates, washing the precipitates with petroleum ether, acetone, ethanol, acetone and water in sequence, and freeze-drying to obtain the chitosan microspheres. And observing the morphology of the chitosan microspheres by using a scanning electron microscope, and counting the diameters of the microspheres, wherein the average size of the microspheres is 20 microns. The BET specific surface area is 360m by nitrogen adsorption2/g。。
Example 9
An aqueous urea solution having a concentration of 20 wt% was used as the dispersion. Mixing chitosan and dispersion liquid according to the mass ratio of 1:10, introducing carbon dioxide into the mixture at 20 ℃, stirring, stopping introducing the carbon dioxide after the chitosan is completely dissolved, and obtaining a transparent chitosan solution after centrifugal deaeration, wherein no chitosan insoluble substances exist at the bottom of a centrifugal tube.
The chitosan stock solution is mixed with an oil phase (olive oil and Tween 80, wherein the Tween 80 accounts for 6 wt%) with the volume ratio of 5 times, and glutaraldehyde with the molar ratio of 0.1 time that of the chitosan monomer is mixed, and then the mixture is stirred at the rotating speed of 1000rpm for 2 hours to form microspheres. The microspheres are poured into ethanol for regeneration, and the precipitate is taken out after centrifugationSequentially washing with petroleum ether, acetone, ethanol, acetone and water, and freeze-drying to obtain the chitosan microspheres. And observing the appearance of the chitosan microspheres by using a scanning electron microscope, and counting the diameters of the microspheres, wherein the average size of the microspheres is 30 microns. The BET specific surface area is 290m by nitrogen adsorption2/g。
Example 10
An aqueous solution of thiourea having a concentration of 13% by weight was used as a dispersion. Mixing chitosan and dispersion liquid according to the mass ratio of 1:10, introducing carbon dioxide into the mixture at 10 ℃, stirring, stopping introducing the carbon dioxide after the chitosan is completely dissolved, and obtaining a transparent chitosan solution after centrifugal deaeration, wherein no chitosan insoluble substances exist at the bottom of a centrifugal tube.
Mixing the chitosan stock solution and an oil phase (olive oil and span 80, the concentration of span 80 is 0.5 wt%) with the volume ratio of 5 times, and stirring at the rotating speed of 1000rpm for 2 hours to form microspheres. And pouring the obtained microspheres into a methanol water solution with the water content of 30 wt% for regeneration, centrifuging, taking the precipitate, washing the precipitate with petroleum ether, acetone, ethanol, acetone and water in sequence, and freeze-drying to obtain the chitosan microspheres. And observing the appearance of the chitosan microspheres by using a scanning electron microscope, and counting the diameters of the microspheres, wherein the average size of the microspheres is 2 microns. The BET specific surface area is 475m by nitrogen adsorption2/g。
Example 11
An aqueous thiourea solution having a concentration of 14% by weight was used as a dispersion. Mixing chitosan and dispersion liquid according to the mass ratio of 1:20, introducing carbon dioxide into the mixture at 10 ℃, stirring, stopping introducing the carbon dioxide after the chitosan is completely dissolved, and obtaining a transparent chitosan solution after centrifugal deaeration, wherein no chitosan insoluble substances exist at the bottom of a centrifugal tube.
Mixing the chitosan stock solution and 5 times volume ratio of oil phase (liquid paraffin and span 80, span 80 accounts for 1 wt%) which is equivalent to 10 times mole ratio of glutaraldehyde of chitosan monomer, mixing, and stirring at 1000rpm for 2h to form microspheres. And pouring the obtained microspheres into a methanol water solution with the alcohol concentration of 70 wt% for regeneration, centrifuging, taking precipitates, washing the precipitates with petroleum ether, acetone, ethanol, acetone and water in sequence, and freeze-drying to obtain the chitosan microspheres. Observing shell by scanning electron microscopeThe morphology of the polysaccharide microspheres, counted by the diameter of the microspheres, had an average size of 15 microns. The BET specific surface area is 422m by nitrogen adsorption2/g。
Example 12
An aqueous urea solution having a concentration of 20 wt% was used as the dispersion. Mixing chitosan and dispersion liquid according to the mass ratio of 1:20, introducing carbon dioxide into the mixture at 5 ℃, stirring, stopping introducing the carbon dioxide after the chitosan is completely dissolved, and obtaining a transparent chitosan solution after centrifugal deaeration, wherein no chitosan insoluble substances exist at the bottom of a centrifugal tube.
Mixing chitosan stock solution and 5 times volume ratio of oil phase (liquid paraffin and span 80, span 80 accounts for 0.5 wt%) which is equivalent to 2 times mole ratio of glutaraldehyde of chitosan monomer, and stirring at 1000rpm for 2h to form microspheres. And pouring the obtained microspheres into a potassium chloride aqueous solution with the salt concentration of 5 wt% for regeneration, centrifuging, taking the precipitate, washing the precipitate with petroleum ether, acetone, ethanol, acetone and water in sequence, and freeze-drying to obtain the chitosan microspheres. And observing the morphology of the chitosan microspheres by using a scanning electron microscope, and counting the diameters of the microspheres to obtain the average size of 11 microns. The BET specific surface area is 435m by nitrogen adsorption2/g。
Example 13
An aqueous urea solution having a concentration of 20 wt% was used as the dispersion. Mixing chitosan and dispersion liquid according to the mass ratio of 1:20, introducing carbon dioxide into the mixture at 2 ℃, stirring, stopping introducing the carbon dioxide after the chitosan is completely dissolved, and obtaining a transparent chitosan solution after centrifugal deaeration, wherein no chitosan insoluble substances exist at the bottom of a centrifugal tube.
Mixing the chitosan stock solution and an oil phase (olive oil and span 80, the concentration of span 80 is 0.5 wt%) with the volume ratio of 5 times, and stirring at the rotating speed of 1000rpm for 2 hours to form microspheres. And pouring the obtained microspheres into a methanol water solution with the water content of 10wt% for regeneration, centrifuging, taking the precipitate, washing the precipitate with petroleum ether, acetone, ethanol, acetone and water in sequence, and freeze-drying to obtain the chitosan microspheres. And observing the appearance of the chitosan microspheres by using a scanning electron microscope, and counting the diameters of the microspheres to obtain the average size of 5 microns. The BET specific surface area is 460m measured by nitrogen adsorption2/g。
Example 14
An aqueous urea solution having a concentration of 45 wt% was used as the dispersion. Mixing chitosan and dispersion liquid according to the mass ratio of 1:20, introducing carbon dioxide into the mixture at 35 ℃, stirring, stopping introducing the carbon dioxide after the chitosan is completely dissolved, and obtaining a transparent chitosan solution after centrifugal deaeration, wherein no chitosan insoluble substances exist at the bottom of a centrifugal tube.
Mixing the chitosan stock solution with 1000 times volume ratio of oil phase (olive oil and Tween 80, wherein Tween 80 accounts for 1 wt%) and stirring at 1000rpm for 2h to form microspheres. And (3) pouring the obtained microspheres into methanol for regeneration, centrifuging, taking the precipitate, washing the precipitate with petroleum ether, acetone, ethanol, acetone and water in sequence, and freeze-drying to obtain the chitosan microspheres. And observing the morphology of the chitosan microspheres by using a scanning electron microscope, and counting the diameters of the microspheres, wherein the average size of the microspheres is 42 microns. The BET specific surface area is 370m by nitrogen adsorption2/g。
Example 15
An aqueous urea solution having a concentration of 24 wt% was used as the dispersion. Mixing chitosan and dispersion liquid according to the mass ratio of 1:20, introducing carbon dioxide into the mixture at 20 ℃, stirring, stopping introducing the carbon dioxide after the chitosan is completely dissolved, and obtaining a transparent chitosan solution after centrifugal deaeration, wherein no chitosan insoluble substances exist at the bottom of a centrifugal tube.
Mixing the chitosan stock solution and an oil phase (olive oil and Tween 80, wherein the concentration of the Tween 80 is 0.5 wt%) with the volume ratio of 1 time, and stirring at the rotating speed of 1000rpm for 2h to form the microspheres. And pouring the obtained microspheres into an aluminum chloride aqueous solution with the mass fraction of 40 wt% for regeneration, centrifuging, taking precipitates, washing the precipitates with petroleum ether, acetone, ethanol, acetone and water in sequence, and freeze-drying to obtain the chitosan microspheres. And observing the morphology of the chitosan microspheres by using a scanning electron microscope, and counting the diameters of the microspheres to obtain the average size of 21 microns. The BET specific surface area of the nitrogen gas adsorption material is 345m2/g。
Example 16
An aqueous urea solution having a concentration of 24 wt% was used as the dispersion. Mixing chitosan and dispersion liquid according to the mass ratio of 1:20, introducing carbon dioxide into the mixture at 20 ℃, stirring, stopping introducing the carbon dioxide after the chitosan is completely dissolved, and obtaining a transparent chitosan solution after centrifugal deaeration, wherein no chitosan insoluble substances exist at the bottom of a centrifugal tube.
Mixing the chitosan stock solution with 100 times volume ratio of oil phase (olive oil and Tween 80, wherein Tween 80 accounts for 1 wt%) and stirring at 1000rpm for 2h to form microspheres. And pouring the obtained microspheres into a potassium chloride aqueous solution with the mass fraction of 20 wt% for regeneration, centrifuging, taking the precipitate, washing the precipitate with petroleum ether, acetone, ethanol, acetone and water in sequence, and freeze-drying to obtain the chitosan microspheres. And observing the appearance of the chitosan microspheres by using a scanning electron microscope, and counting the diameters of the microspheres, wherein the average size of the microspheres is 30 microns. The BET specific surface area is 290m by nitrogen adsorption2/g。
Example 17
An aqueous urea solution having a concentration of 30 wt% was used as the dispersion. Mixing chitosan and dispersion liquid according to the mass ratio of 1:20, introducing carbon dioxide into the mixture at 20 ℃, stirring, stopping introducing the carbon dioxide after the chitosan is completely dissolved, and obtaining a transparent chitosan solution after centrifugal deaeration, wherein no chitosan insoluble substances exist at the bottom of a centrifugal tube.
Mixing the chitosan stock solution and an oil phase (olive oil and span 80, the concentration of span 80 is 0.5 wt%) with the volume ratio of 5 times, and stirring at the rotating speed of 1000rpm for 2 hours to form microspheres. And pouring the obtained microspheres into a sodium sulfate aqueous solution with the mass fraction of 10wt% for regeneration, centrifuging, taking the precipitate, washing the precipitate with petroleum ether, acetone, ethanol, acetone and water in sequence, and freeze-drying to obtain the chitosan microspheres. And observing the appearance of the chitosan microspheres by using a scanning electron microscope, and counting the diameters of the microspheres, wherein the average size of the microspheres is 30 microns. The BET specific surface area is 320m by nitrogen adsorption2/g。
Example 18
An aqueous 12 wt% thiourea solution was used as a dispersion. Mixing chitosan and dispersion liquid according to the mass ratio of 1:20, introducing carbon dioxide into the mixture at 20 ℃, stirring, stopping introducing the carbon dioxide after the chitosan is completely dissolved, and obtaining a transparent chitosan solution after centrifugal deaeration, wherein no chitosan insoluble substances exist at the bottom of a centrifugal tube.
Mixing the chitosan stock solution and an oil phase (olive oil and Tween 80, wherein the concentration of the Tween 80 is 0.5 wt%) with the volume ratio of 2.5 times, and stirring at the rotating speed of 900rpm for 2 hours at room temperature to form microspheres. And pouring the obtained microspheres into a calcium chloride aqueous solution with the mass fraction of 5 wt% for regeneration, centrifuging, taking precipitates, washing the precipitates with petroleum ether, acetone, ethanol, acetone and water in sequence, and freeze-drying to obtain the chitosan microspheres. And observing the morphology of the chitosan microspheres by using a scanning electron microscope, and counting the diameters of the microspheres to obtain the average size of 41 microns. The BET specific surface area is 356m by nitrogen adsorption2/g。
Example 19
An aqueous solution of thiourea having a concentration of 13% by weight was used as a dispersion. Mixing chitosan and dispersion liquid according to the mass ratio of 1:20, introducing carbon dioxide into the mixture at 20 ℃, stirring, stopping introducing the carbon dioxide after the chitosan is completely dissolved, and obtaining a transparent chitosan solution after centrifugal deaeration, wherein no chitosan insoluble substances exist at the bottom of a centrifugal tube.
Mixing chitosan stock solution with 5 times volume ratio of oil phase (olive oil and span 80, span 80 accounts for 5 wt%), 1 time molar ratio of chitosan monomer of epichlorohydrin, stirring at room temperature at 900rpm for 2h to form microspheres. And pouring the obtained microspheres into an acetic acid aqueous solution with the mass fraction of 20 wt% for regeneration, centrifuging, taking the precipitate, washing the precipitate with petroleum ether, acetone, ethanol, acetone and water in sequence, and freeze-drying to obtain the chitosan microspheres. And observing the appearance of the chitosan microspheres by using a scanning electron microscope, and counting the diameters of the microspheres to obtain the average size of 60 microns. The BET specific surface area is 270m by nitrogen adsorption2/g。
Example 20
An aqueous thiourea solution having a concentration of 14% by weight was used as a dispersion. Mixing chitosan and dispersion liquid according to the mass ratio of 1:20, introducing carbon dioxide into the mixture at 20 ℃, stirring, stopping introducing the carbon dioxide after the chitosan is completely dissolved, and obtaining a transparent chitosan solution after centrifugal deaeration, wherein no chitosan insoluble substances exist at the bottom of a centrifugal tube.
Chitosan stock solution and 5 volume times of oil phase (olive oil and olive oil)Tween 80, the concentration of tween 80 is 0.5 wt%), and the mixture is stirred at the rotating speed of 900rpm for 2 hours at room temperature to form microspheres. And pouring the obtained microspheres into a potassium sulfate aqueous solution with the mass fraction of 10wt% for regeneration, centrifuging, taking the precipitate, washing the precipitate with petroleum ether, acetone, ethanol, acetone and water in sequence, and freeze-drying to obtain the chitosan microspheres. And observing the morphology of the chitosan microspheres by using a scanning electron microscope, and counting the diameters of the microspheres, wherein the average size of the microspheres is 68 microns. The BET specific surface area is 365m by nitrogen adsorption2/g。
Example 21
An aqueous thiourea solution having a concentration of 14% by weight was used as a dispersion. Mixing chitosan and dispersion liquid according to the mass ratio of 1:20, introducing carbon dioxide into the mixture at 20 ℃, stirring, stopping introducing the carbon dioxide after the chitosan is completely dissolved, and obtaining a transparent chitosan solution after centrifugal deaeration, wherein no chitosan insoluble substances exist at the bottom of a centrifugal tube.
Mixing the chitosan stock solution and 100 times volume ratio of oil phase (isooctane and span 80, span 80 accounts for 0.5 wt%) and stirring at 900rpm at room temperature for 2h to form microspheres. And pouring the obtained microspheres into a sodium phosphate aqueous solution with the mass fraction of 5 wt% for regeneration, centrifuging, taking the precipitate, washing the precipitate with petroleum ether, acetone, ethanol, acetone and water in sequence, and freeze-drying to obtain the chitosan microspheres. And observing the appearance of the chitosan microspheres by using a scanning electron microscope, and counting the diameters of the microspheres, wherein the average size of the microspheres is 30 microns. The BET specific surface area is 250m by nitrogen adsorption2/g。
Example 22
An aqueous solution of thiourea having a concentration of 13% by weight was used as a dispersion. Mixing chitosan and dispersion liquid according to the mass ratio of 1:20, introducing carbon dioxide into the mixture at 20 ℃, stirring, stopping introducing the carbon dioxide after the chitosan is completely dissolved, and obtaining a transparent chitosan solution after centrifugal deaeration, wherein no chitosan insoluble substances exist at the bottom of a centrifugal tube.
And adding 1 wt% of sodium alginate into the chitosan solution, stirring for dissolving, and performing centrifugal deaeration to obtain the chitosan/sodium alginate solution. Mixing chitosan/sodium alginate solution with 10 volume times of oil phase (olive oil and sodium alginate)Span 80, wherein the proportion of span 80 is 10 wt%), and the microspheres are formed after stirring at the rotating speed of 900rpm for 2 hours at room temperature. And pouring the obtained microspheres into an ethanol water solution with the water content of 10wt% for regeneration, centrifuging, taking the precipitate, washing the precipitate with petroleum ether, acetone, ethanol, acetone and water in sequence, and freeze-drying to obtain the chitosan/sodium alginate microspheres. And observing the morphology of the chitosan microspheres by using a scanning electron microscope, and counting the diameters of the microspheres to obtain the average size of 31 microns. The BET specific surface area is 254m by nitrogen adsorption2/g。
Example 23
Preparing 97g of urea aqueous solution with the concentration of 20 wt% in advance as dispersion liquid, adding 0.5g of graphene oxide, performing ultrasonic dispersion, adding 2.5g of chitosan, introducing carbon dioxide into the mixture at 20 ℃, stirring, stopping introducing the carbon dioxide when the chitosan is completely dissolved, and performing centrifugal deaeration to obtain a transparent chitosan/graphene oxide solution. Mixing the chitosan/graphene oxide stock solution with an oil phase (olive oil and tween 80, the concentration of the tween 80 is 0.5 wt%) in a volume ratio of 2.5 times, and stirring at the rotating speed of 900rpm for 2 hours at room temperature to form microspheres. And pouring the obtained microspheres into an ethanol water solution with the water content of 30 wt% for regeneration, centrifuging, taking the precipitate, washing the precipitate with petroleum ether, acetone, ethanol, acetone and water in sequence, and freeze-drying to obtain the chitosan/graphene oxide microspheres. And observing the morphology of the chitosan microspheres by using a scanning electron microscope, and counting the diameters of the microspheres, wherein the average size of the microspheres is 40 micrometers. The BET specific surface area is 350m by nitrogen adsorption2(ii) in terms of/g. Adsorption experiments show that the chitosan/graphene oxide microspheres have good effect on tetracycline, and each 1g of chitosan/graphene oxide microspheres can adsorb 420mg of tetracycline.
Example 24
An aqueous solution of thiourea having a concentration of 13% by weight was used as a dispersion. Mixing chitosan and dispersion liquid according to the mass ratio of 1:20, introducing carbon dioxide into the mixture at 20 ℃, stirring, stopping introducing the carbon dioxide after the chitosan is completely dissolved, and obtaining a transparent chitosan solution after centrifugal deaeration, wherein no chitosan insoluble substances exist at the bottom of a centrifugal tube.
Adding 1 wt% of a di-component in the chitosan solutionAnd stirring and dissolving the molybdenum sulfide nanosheets, and centrifuging and defoaming to obtain the chitosan/molybdenum disulfide nanosheet composite solution. Mixing the chitosan/molybdenum disulfide nanosheet composite solution with an oil phase (olive oil and span 80, the span 80 accounts for 10 wt%) in a volume ratio of 10 times, and stirring at a rotating speed of 900rpm for 2 hours at room temperature to form microspheres. And pouring the obtained microspheres into 10wt% magnesium chloride-50 wt% ethanol water solution for regeneration, centrifuging, taking the precipitate, washing with petroleum ether, acetone, ethanol, acetone and water in sequence, and freeze-drying to obtain the chitosan/molybdenum disulfide nanosheet composite microspheres. And observing the morphology of the chitosan microspheres by using a scanning electron microscope, and counting the diameters of the microspheres, wherein the average size of the microspheres is 33 microns. The BET specific surface area is 344m by nitrogen adsorption2/g。
Example 25
An aqueous solution of thiourea having a concentration of 13% by weight was used as a dispersion. Mixing chitosan and dispersion liquid according to the mass ratio of 1:20, introducing carbon dioxide into the mixture at 20 ℃, stirring, stopping introducing the carbon dioxide after the chitosan is completely dissolved, and obtaining a transparent chitosan solution after centrifugal deaeration, wherein no chitosan insoluble substances exist at the bottom of a centrifugal tube.
Adding 1 wt% of chitin nanosheets into the chitosan solution, stirring for dissolving, and performing centrifugal deaeration to obtain the chitosan/chitin nanosheet composite solution. Mixing the chitosan/chitin nano-sheet composite solution with an oil phase (olive oil and span 80, the span 80 accounts for 10 wt%) in a volume ratio of 10 times, and stirring at a rotating speed of 900rpm for 2 hours at room temperature to form microspheres. And pouring the obtained microspheres into an ethanol aqueous solution with the alcohol concentration of 10wt% for regeneration, centrifuging, taking precipitates, washing the precipitates with petroleum ether, acetone, ethanol, acetone and water in sequence, and freeze-drying to obtain the chitosan/chitin nanosheet composite microspheres. And observing the morphology of the chitosan microspheres by using a scanning electron microscope, and counting the diameters of the microspheres, wherein the average size of the microspheres is 53 microns. The BET specific surface area is 244m by nitrogen adsorption2/g。
Example 26
97g of thiourea aqueous solution having a concentration of 14% by weight was prepared in advance as a dispersion, 0.5g of graphene oxide was added, and after ultrasonic dispersion, 2.5g of a shell was addedAnd (3) introducing carbon dioxide into the mixture at the temperature of 20 ℃ and stirring, stopping introducing the carbon dioxide after the chitosan is completely dissolved, and performing centrifugal deaeration to obtain a transparent chitosan/graphene oxide solution. Mixing the chitosan/graphene oxide stock solution with an oil phase (olive oil and tween 80, the concentration of the tween 80 is 0.5 wt%) in a volume ratio of 2.5 times, and stirring at the rotating speed of 900rpm for 2 hours at room temperature to form microspheres. And pouring the obtained microspheres into an ethanol water solution with the water content of 50 wt% for regeneration, centrifuging, taking the precipitate, washing the precipitate with petroleum ether, acetone, ethanol, acetone and water in sequence, and freeze-drying to obtain the chitosan/graphene oxide microspheres. And heating the obtained chitosan/graphene oxide microspheres to 1000 ℃ from room temperature at a speed of 10 ℃/min, and taking nitrogen as protective gas to obtain the nitrogen-doped carbon aerogel microspheres. The specific surface area of the carbon aerogel obtained by the nitrogen adsorption-desorption experiment is 1059m2/g。
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any modification, equivalent replacement, and improvement made by those skilled in the art within the technical scope of the present invention should be included in the scope of the present invention.

Claims (10)

1. A method for preparing a microsphere material by using a chitosan solution with a pH value of 6-8 is characterized by comprising the following steps:
(1) preparing a dispersion liquid;
the dispersion is one or a mixture of two of a urea aqueous solution and a thiourea aqueous solution; the concentration of the urea aqueous solution is 6-60 wt%; the concentration of the thiourea aqueous solution is 3-14 wt%;
(2) adding chitosan into the dispersion liquid, controlling the temperature to be between the freezing point and 35 ℃, introducing carbon dioxide into the solution, simultaneously stirring to dissolve the chitosan, stopping introducing the carbon dioxide after the chitosan is completely dissolved, and defoaming to obtain a transparent chitosan solution with the pH value of 6-8; the mass ratio of the chitosan to the dispersion liquid is 1: 7-1: 1000;
(3) preparing a chitosan microsphere material: and (3) forming chitosan emulsion drops by the chitosan solution obtained in the step (2) and the oil phase, and solidifying the emulsion drops by a coagulant or a chemical cross-linking agent to form the chitosan microspheres.
2. The method of claim 1, wherein: the concentration of the urea aqueous solution is 18-60 wt%; the concentration of the thiourea aqueous solution is 7-14 wt%.
3. The method of claim 1, further comprising: the oil phase in the step (3) consists of an oily substance which is liquid at normal temperature and an oil-soluble emulsifier; the chitosan emulsion droplet forming method comprises emulsification by using a stirring device, a microfluidic device or a membrane emulsifier.
4. The method of claim 3, wherein: the oily substance is selected from liquid paraffin, petroleum ether, olive oil, cottonseed oil, soybean oil or sunflower seed oil; the oily emulsifier is selected from sorbitan sesquioleate, glyceryl ether polymer, polyoxyethylene hydrogenated castor oil, sorbitan trioleate, sorbitan monooleate, sorbitan tristearate and tween 80; the mass concentration of the emulsifier in the oil phase is 0.5-10 wt%.
5. The method of claim 1, wherein: the volume ratio of the chitosan solution to the oil phase in the step (3) is 1: 1-1: 1000.
6. The method of claim 5, wherein: the volume ratio of the chitosan solution to the oil phase is 1: 2-1: 100.
7. The method of claim 3, wherein: the method for forming the emulsion droplets by using the membrane emulsifier is characterized in that a chitosan solution is pressed into an oil phase through a microporous membrane by using pressure to obtain the emulsion droplets with uniform size; the method for forming the emulsion drop by utilizing the micro-fluidic device comprises the steps of conveying an oil phase and a water phase to two intersected channels in a micro-fluidic chip by using a micro-pump, wherein the oil phase is used as a continuous phase to separate the water phase to form a monodisperse emulsion drop; the method of forming the emulsion droplets using the stirring device is to mix the oil phase and the water phase, and then mechanically stir them to disperse the water phase into the oil phase to form the emulsion droplets.
8. The method of claim 1, wherein: the cross-linking agent in the step (3) comprises an aldehyde cross-linking agent, a glycidyl ether cross-linking agent, an epoxy compound, iridoids and polyphenols; the molar ratio of the cross-linking agent to the chitosan is 1:0.1 to 10; the adopted coagulator is a mixed aqueous solution of one or more of alcohols, salts, amides, dimethyl sulfoxide, ethyl acetate and acetone, and the microspheres are formed in a physical crosslinking mode.
9. A method for preparing functional chitosan microspheres, which is characterized by comprising the method for preparing chitosan microsphere material of claim 1, wherein functional organic or inorganic additives are added in the preparation process of the chitosan microsphere material of claim 1, or natural macromolecules or synthetic macromolecules are introduced for blending; the additive is added through a chitosan solution or a coagulant; the functional organic or inorganic additive is selected from one or more of a plasticizer, a reinforcing agent, a refractory material additive, a dye, an optical stabilizer, an antibacterial bacteriostatic agent, a conductive material and a surfactant; the natural polymer or the synthetic polymer is selected from polymer nano-fiber, cellulose and derivatives thereof, animal protein, vegetable protein, alginate, polyethylene glycol, polyvinyl alcohol or conductive polymer.
10. A method for preparing nitrogen-doped carbon aerogel microspheres, which comprises the method for preparing chitosan microspheres of claim 1 or the method for preparing functional chitosan microspheres of claim 9, and further comprises performing heat treatment on the chitosan microspheres prepared in claim 1 or the functional chitosan microspheres prepared in claim 9 at a temperature of 150 ℃ or higher under the protection of inert gas atmosphere to obtain the carbon aerogel microspheres.
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