CN114656677B - Lignin porous microsphere based on W/O/W type multiple emulsion solvent volatilization and preparation method and application thereof - Google Patents

Lignin porous microsphere based on W/O/W type multiple emulsion solvent volatilization and preparation method and application thereof Download PDF

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CN114656677B
CN114656677B CN202210127717.7A CN202210127717A CN114656677B CN 114656677 B CN114656677 B CN 114656677B CN 202210127717 A CN202210127717 A CN 202210127717A CN 114656677 B CN114656677 B CN 114656677B
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lignin
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multiple emulsion
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porous microspheres
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CN114656677A (en
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庞煜霞
李治平
邱学青
楼宏铭
易聪华
于杰瑶
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South China University of Technology SCUT
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
    • C08J9/28—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof by elimination of a liquid phase from a macromolecular composition or article, e.g. drying of coagulum
    • A—HUMAN NECESSITIES
    • A01—AGRICULTURE; FORESTRY; ANIMAL HUSBANDRY; HUNTING; TRAPPING; FISHING
    • A01N—PRESERVATION OF BODIES OF HUMANS OR ANIMALS OR PLANTS OR PARTS THEREOF; BIOCIDES, e.g. AS DISINFECTANTS, AS PESTICIDES OR AS HERBICIDES; PEST REPELLANTS OR ATTRACTANTS; PLANT GROWTH REGULATORS
    • A01N25/00—Biocides, pest repellants or attractants, or plant growth regulators, characterised by their forms, or by their non-active ingredients or by their methods of application, e.g. seed treatment or sequential application; Substances for reducing the noxious effect of the active ingredients to organisms other than pests
    • A01N25/08—Biocides, pest repellants or attractants, or plant growth regulators, characterised by their forms, or by their non-active ingredients or by their methods of application, e.g. seed treatment or sequential application; Substances for reducing the noxious effect of the active ingredients to organisms other than pests containing solids as carriers or diluents
    • A01N25/10—Macromolecular compounds
    • A—HUMAN NECESSITIES
    • A01—AGRICULTURE; FORESTRY; ANIMAL HUSBANDRY; HUNTING; TRAPPING; FISHING
    • A01N—PRESERVATION OF BODIES OF HUMANS OR ANIMALS OR PLANTS OR PARTS THEREOF; BIOCIDES, e.g. AS DISINFECTANTS, AS PESTICIDES OR AS HERBICIDES; PEST REPELLANTS OR ATTRACTANTS; PLANT GROWTH REGULATORS
    • A01N43/00—Biocides, pest repellants or attractants, or plant growth regulators containing heterocyclic compounds
    • A01N43/90—Biocides, pest repellants or attractants, or plant growth regulators containing heterocyclic compounds having two or more relevant hetero rings, condensed among themselves or with a common carbocyclic ring system
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/22—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising organic material
    • B01J20/24—Naturally occurring macromolecular compounds, e.g. humic acids or their derivatives
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/28—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties
    • B01J20/28054—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties characterised by their surface properties or porosity
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/28—Treatment of water, waste water, or sewage by sorption
    • C02F1/286—Treatment of water, waste water, or sewage by sorption using natural organic sorbents or derivatives thereof
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08H—DERIVATIVES OF NATURAL MACROMOLECULAR COMPOUNDS
    • C08H6/00—Macromolecular compounds derived from lignin, e.g. tannins, humic acids
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2101/00—Nature of the contaminant
    • C02F2101/10—Inorganic compounds
    • C02F2101/20—Heavy metals or heavy metal compounds
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2397/00—Characterised by the use of lignin-containing materials

Abstract

The invention discloses a lignin porous microsphere based on W/O/W type multiple emulsion solvent volatilization, a preparation method and application thereof. The method comprises the steps of firstly, carrying out radiation hydrophobic modification on lignin, dispersing the modified lignin in water, adding alkali to dissolve and filter the lignin, adding acid to adjust pH value to separate out the lignin, and taking the separated lignin particle dispersion liquid as a water phase; adding water into the oil phase containing the surfactant, and emulsifying to obtain W/O primary emulsion; adding the W/O primary emulsion into the external water phase, and emulsifying by high-speed stirring to obtain W/O/W type multiple emulsion; and drying the emulsion to form the pure lignin porous microspheres. The preparation method is simple, the organic oil phase can be recycled, and the method has the potential of large-scale industrialization. Meanwhile, the method has the advantages of good balling effect, controllable particle size, rich pore channels in the ball, easy storage of the dried microspheres and convenient transportation. The sphere is pure lignin, has good biocompatibility, is biodegradable, and has zero pollution to the environment and organisms.

Description

Lignin porous microsphere based on W/O/W type multiple emulsion solvent volatilization and preparation method and application thereof
Technical Field
The invention belongs to the technical field of microsphere preparation, and particularly relates to a lignin porous microsphere based on W/O/W type multiple emulsion solvent volatilization, and a preparation method and application thereof.
Background
The microsphere is a spherical or spheroidal entity which takes a high molecular material as a matrix skeleton, has the grain diameter of 1-250 mu m, and is mainly divided into a solid microsphere, a hollow microsphere and a porous microsphere according to the structure. The porous microspheres have abundant and interconnected pore structures inside and outside, and have larger specific surface area and space capacity, so the porous microspheres have unique advantages in the aspects of micro-adsorption materials, drug carriers, catalytic materials and the like. The commonly used polymer materials mainly include natural polymer materials such as gelatin, chitosan, sodium alginate and the like, and synthetic polymer materials such as polylactic acid, polyethylene glycol, polystyrene and the like. Compared with synthetic polymer materials, natural polymer materials have the advantages of low price, good biocompatibility, no toxicity, biodegradability and the like.
Lignin is a natural polymer material with a very wide source, and the content of available lignin in the biosphere is about 3000 million tons. Meanwhile, the lignin has unique ultraviolet absorption capacity, oxidation resistance, a large number of active groups such as hydroxyl and the like, so that the lignin can better meet the special application requirements of certain fields. For example: when the lignin is used as a sphere material, the lignin can be used for encapsulating visible light easily-decomposed medicines to realize more effective protection, and can also be used for sewage treatment to better adsorb heavy metals or cationic polymers. In addition, the lignin has both hydrophilic groups and lipophilic groups in molecules, has amphipathy, and can be used as an emulsifier to prepare emulsion, so that more application possibilities are given.
There are many methods for preparing porous microspheres, such as: solvent evaporation, emulsion polymerization, seed swelling, hydrothermal and the like, but the method for preparing the porous microspheres by using lignin as a spherical material is single. The lignin-based porous microspheres are prepared by an inverse emulsion polymerization method or an aqueous suspension polymerization method, the preparation process is complex, and chemical reaction is required. Meanwhile, an organic solvent with high toxicity is used in the reaction process, so that the green chemical concept is not met. In these methods, lignin is usually combined with other macromolecules, rather than just lignin as a single spherical material, resulting in a low lignin content in the spherical material and not achieving maximum utilization of lignin.
In view of the above, it is urgently needed to develop a preparation method of lignin porous microspheres with simple operation.
Disclosure of Invention
In order to solve the defects and shortcomings of the prior art, the invention mainly aims to provide a preparation method of lignin porous microspheres based on W/O/W type multiple emulsion solvent volatilization.
The method disclosed by the invention is simple to operate, other high polymer materials are not required to be added except lignin particles and a small amount of traditional surfactant, a chemical reaction is not required, the oil phase of the double emulsion is volatilized firstly to solidify emulsion droplets into microspheres, and then the microspheres are centrifugally dried to remove the inner water phase, so that the lignin porous microspheres can be obtained.
According to the method, the solubility of the low-boiling-point oil relative to the lignin is utilized, the lignin is gradually separated out along with the volatilization of the solvent to form a solid sphere in the early stage of the drying of the emulsion, and the internal water phase still exists at the moment. In the later stage of emulsion drying, the internal water phase gradually disappears and simultaneously generates cavities and pore canals. The method for preparing the lignin porous microspheres has mild conditions, is simple, and can successfully overcome the defects of the prior art, and the obtained microspheres have adjustable sizes.
Firstly, performing high-energy radiation hydrophobic modification on lignin, dispersing the modified lignin in water, adding a proper amount of alkali to dissolve the lignin, filtering out insoluble substances, and then adding acid to adjust to a proper pH value to separate out the lignin in a particle form; and then using the traditional surfactant as an emulsifier to prepare W/O primary emulsion, and adding the obtained W/O primary emulsion into an external water phase containing lignin particles for emulsification to obtain W/O/W type multiple emulsion. The lignin particles in the external water phase are adsorbed in the interface of the oil phase and the external water phase in a large amount and are partially dissolved into the oil phase. Drying the W/O/W double emulsion, firstly separating out and solidifying lignin dissolved in the oil phase along with the volatilization of the low-boiling-point oil phase, and then generating cavities and pore canals in the microspheres by the volatilization of the internal water phase, thereby finally obtaining the porous microspheres.
The invention also aims to provide the lignin porous microspheres prepared by the method based on volatilization of the W/O/W type multiple emulsion solvent.
The invention further aims to provide application of the lignin porous microspheres based on volatilization of the W/O/W type multiple emulsion solvent.
The purpose of the invention is realized by the following technical scheme:
a preparation method of lignin porous microspheres based on W/O/W type multiple emulsion solvent volatilization comprises the following steps:
(1) Performing high-energy radiation hydrophobic modification on lignin, dispersing the hydrophobic modified lignin in water, adding alkali to dissolve and filter the hydrophobic modified lignin, and then adding acid to adjust pH value to separate out the hydrophobic modified lignin in a particle form to obtain an external water phase of the hydrophobic modified lignin;
(2) Adding water into the oil phase containing the surfactant, emulsifying to obtain W/O primary emulsion, adding the W/O primary emulsion into the hydrophobic modified lignin external water phase, and emulsifying to obtain W/O/W type multiple emulsion;
(3) Drying the W/O/W type multiple emulsion, firstly separating out and solidifying lignin dissolved in the oil phase along with the volatilization of the low-boiling-point oil phase, and then generating cavities and pore canals in the microspheres by the volatilization of the internal water phase, thereby finally obtaining the porous microspheres.
Preferably, the lignin in the step (1) is at least one of alkali lignin and enzymatic hydrolysis lignin; the alkali lignin can be at least one of wood pulp black liquor, bamboo pulp black liquor, straw pulp black liquor, reed pulp black liquor and bagasse pulp black liquor, and is subjected to acid precipitation drying to obtain acid precipitation lignin powder; the enzymatic hydrolysis lignin is lignin separated and extracted from residues after alcohol is prepared by fermenting cellulose in plant raw materials.
Preferably, the step (1) of hydrophobically modifying the lignin by high-energy radiation comprises the following steps: dissolving lignin and hydrophobic monomer in solvent, dispersing uniformly, and then N at room temperature 2 Or continuously irradiating the cobalt source to the required absorbed dose in the inert gas atmosphere; wherein the absorption dose is 10-60 kGy, the radiation dose rate is 0.5-5 kGy/h, and the mass ratio of the lignin to the hydrophobic monomer is 1.
More preferably, the hydrophobic monomer is at least one of dodecyl vinyl ether, methyl acrylate, vinyl trimethoxy silane, styrene, vinyl pyridinium salt, and acrylamide; the solvent is acetone, and the mass ratio of the lignin to the acetone is 1.
Preferably, the mass ratio of the hydrophobically modified lignin to the water in the step (1) is 0.05-1: 10.
preferably, the alkali in the step (1) is at least one of sodium hydroxide, potassium hydroxide and ammonia water; adding alkali to adjust the pH value to 10-12.
Preferably, the acid in step (1) is at least one of hydrochloric acid, sulfuric acid and acetic acid; adding acid to adjust the pH value to 3-5.
Preferably, the surfactant in step (2) is at least one of Span-60 and polyglycerol ricinoleate (PGPR); the oil phase is ethyl acetate, or mixed solution formed by the ethyl acetate and cyclopentanone according to the mass ratio of 4:1: -9:1, or mixed solution formed by the ethyl acetate and n-butanol according to the mass ratio of 4:1-9:1; the mass ratio of water to oil phase in the W/O colostrum is 1:3-1:7; the mass percentage of the surfactant in the oil phase is 0.5-6%.
Preferably, the mass ratio of the W/O colostrum to the hydrophobic modified lignin external water phase in the step (2) is 1:4-1:9; the mass percentage of the hydrophobic modified lignin particles in the external water phase is 0.5-10%.
Preferably, the W/O colostrum in the step (2) is emulsified and cut for 5min to 10min at 16000rpm to 26000 rpm; the W/O/W type multiple emulsion is stirred at high speed of 1000-3000 rpm for 20-40 min.
Preferably, the drying treatment in step (3) is: standing at 25-35 ℃ under normal pressure to volatilize the oil phase for 12-24 h, and then centrifugally drying; or rotationally evaporating the oil phase for 30-60 min at 25-35 ℃, the vacuum degree of 0.07-0.09 MPa and the rotating speed of 30-60 rpm, and then centrifugally drying.
Preferably, the preparation method of the lignin porous microspheres based on the W/O/W type multiple emulsion specifically comprises the following steps:
(1) Preparation of hydrophobic lignin: dissolving lignin and hydrophobic monomer in solvent, dispersing uniformly, and then N at room temperature 2 Or under the atmosphere of inert gas,continuously carrying out cobalt source irradiation to the required absorption dose, wherein the absorption dose is 10-60 kGy, the radiation dose rate is 0.5-5 kGy/h, and the mass ratio of the lignin to the hydrophobic monomer is 1.05-1;
(2) Preparation of lignin particle dispersion: dispersing the lignin after radiation modification in water, adding alkali to adjust the pH value to 10-12, filtering and removing impurities to obtain a hydrophobic modified lignin solution, and adding acid to adjust the pH value of a system to 3-5, so that lignin is separated out to form a lignin particle dispersion liquid;
(3) Preparation of W/O/W type multiple emulsion: adding a proper amount of deionized water into an oil phase containing an oil-soluble surfactant, and emulsifying by using a homogenizer to obtain W/O (W/O) primary emulsion; taking the hydrophobic modified lignin particle dispersion as an external water phase, adding the W/O primary emulsion into the external water phase, and stirring and emulsifying at a high speed to obtain a W/O/W type multiple emulsion;
(4) Preparing lignin porous microspheres: standing the W/O/W type multiple emulsion at a proper temperature under normal pressure for a period of time to volatilize an oil phase, and then centrifugally drying; or under the reduced pressure condition, after the oil phase is rotated and evaporated, the oil phase is centrifugally dried.
The lignin porous microsphere prepared by the method is based on volatilization of a W/O/W type multiple emulsion solvent.
The application of the lignin porous microspheres volatilized based on the W/O/W type multiple emulsion solvent in controlled release of drugs and heavy metal adsorption in water treatment is disclosed.
Compared with the prior art, the invention has the following advantages and beneficial effects:
1. the principle of preparing the lignin porous microspheres is to emulsify the hydrophobic modified lignin particles to obtain W/O/W type multiple emulsion, on one hand, the hydrophobic modified lignin particles can be used as an emulsifier to be firmly adsorbed on an oil phase interface and an external water phase interface to prevent emulsion droplets from aggregating, so that the use of a surfactant is reduced, and a stabilizing effect which is stronger than that of the surfactant is exerted; on the other hand, the hydrophobic modified lignin adsorbed on the oil-water interface can be dissolved by the oil phase, in the early drying process, the dissolved hydrophobic modified lignin can be separated out along with the volatilization of the low-boiling-point oil phase to form a sphere, and then the internal water phase is evaporated to enable the interior of the sphere to generate a cavity and a channel.
2. The invention carries out radiation hydrophobic modification on lignin and uses the hydrophobically modified lignin particles to prepare W/O/W type multiple emulsion. The lignin is modified by hydrophobization, so that the dissolving capacity in an oil phase can be improved, and regular spheres can be obtained.
3. The method for preparing the lignin porous microspheres is simple to operate, and the used low-boiling-point oil phase can be recycled by rotary evaporation, so that the method has the potential of large-scale industrial production. The sphere is pure lignin, has good biocompatibility, is biodegradable, and has zero pollution to the environment and organisms.
Drawings
FIG. 1 is a graph showing the contact angle of water on the thin lignin film before and after hydrophobic modification by irradiation in example 1.
FIG. 2 is an infrared spectrum of lignin before and after hydrophobic modification by irradiation in example 1.
Fig. 3 is an SEM image of lignin porous microspheres prepared in example 1.
Fig. 4 is a cross-sectional SEM image of the lignin porous microspheres prepared in example 1.
Fig. 5 shows the photolysis resistance of the avermectin-loaded lignin porous microspheres prepared in example 7.
Detailed Description
The present invention will be described in further detail with reference to examples and drawings, but the embodiments of the present invention are not limited thereto.
Those who do not specify specific conditions in the examples of the present invention follow conventional conditions or conditions recommended by the manufacturer. The raw materials, reagents and the like used without reference to manufacturers are all conventional products which can be obtained by commercial purchase.
Example 1
(1) Preparation of hydrophobic lignin: dissolving 10g of acid-out lignin powder of dried wood pulp black liquor in 100g of acetone solution containing 2g of dodecyl vinyl ether, and adding N at room temperature 2 Under the atmosphere, the cobalt source irradiation is continuously carried out until the absorbed dose is 60kGy and the radiation dose rate is 5kGy/h. And finally, carrying out rotary steaming and drying on the obtained mixed solution to obtain the hydrophobic modified lignin powder.
(2) Preparation of lignin particle dispersion: dispersing 2g of the hydrophobically modified lignin obtained in the step (1) in 100g of water, adjusting the pH to 11 by using 1mol/L NaOH solution, filtering and removing impurities to obtain a hydrophobically modified lignin solution, and adjusting the pH of the system to 3 by using 1mol/L HCl solution to separate out lignin to form a lignin particle dispersion.
(3) Preparation of W/O/W type multiple emulsion: first, 2.5g of deionized water was added to 7.5g of ethyl acetate containing 2wt% of PGPR, and the mixture was emulsified at 16000rpm for 10min using a homogenizer to obtain W/O colostrum; then 40g of hydrophobically modified lignin particle dispersion with the concentration of 2wt% is used as an external water phase, the obtained W/O primary emulsion is added into the external water phase, and the mixture is emulsified for 30min at 2000rpm, thus obtaining W/O/W type multiple emulsion.
(4) Preparing lignin porous microspheres: and (3) exposing the obtained W/O/W type multiple emulsion to normal pressure at 35 ℃, standing for 12h to volatilize an oil phase, and centrifuging and drying to obtain the lignin porous microspheres.
Example 2
(1) Preparation of hydrophobic lignin: dissolving 10g of acid-out lignin powder of dried bamboo pulp black liquor in 100g of acetone solution containing 0.5g of methyl acrylate, and performing N reaction at room temperature 2 Under the atmosphere, the cobalt source irradiation is continuously carried out until the absorption dose is 40kGy, and the radiation dose rate is 2kGy/h. And finally, carrying out rotary steaming and drying on the obtained mixed solution to obtain the hydrophobic modified lignin powder.
(2) Preparation of lignin particle dispersion: dispersing 5g of the hydrophobically modified lignin obtained in the step (1) in 100g of water, adjusting the pH value to 12 by using 1mol/L NaOH solution, filtering to remove impurities to obtain a hydrophobically modified lignin solution, and adjusting the pH value of the system to 5 by using 1mol/L acetic acid solution to separate out lignin to form a lignin particle dispersion liquid.
(3) Preparation of W/O/W type multiple emulsion: firstly, adding 2.5g of deionized water into a mixed solution of 7.5g of ethyl acetate and cyclopentanone containing 0.5wt% of PGPR, wherein the mass ratio of the ethyl acetate to the cyclopentanone is 4:1, and emulsifying for 5min at 26000rpm by using a homogenizer to obtain W/O colostrum; then 40g 5wt% of hydrophobically modified lignin particle dispersion is used as an external water phase, the obtained W/O primary emulsion is added into the external water phase, and the W/O/W type multiple emulsion is obtained after emulsification for 20min at 3000 rpm.
(4) Preparing lignin porous microspheres: under the conditions that the temperature is 25 ℃, the vacuum degree is 0.09MPa and the rotating speed is 60rpm, performing rotary evaporation for 60min, and performing centrifugal drying to obtain the lignin porous microspheres.
Example 3
(1) Preparation of hydrophobic lignin: dissolving 10g of dried enzymatic lignin powder in 100g of acetone solution containing 1g of vinyltrimethoxysilane, and heating at room temperature to obtain N 2 Under the atmosphere, the cobalt source irradiation is continuously carried out until the absorbed dose is 30kGy and the radiation dose rate is 0.5kGy/h. And finally, carrying out rotary steaming and drying on the obtained mixed solution to obtain the hydrophobic modified lignin powder.
(2) Preparation of lignin particle dispersion: dispersing 10g of the hydrophobically modified lignin obtained in the step (1) in 100g of water, adjusting the pH to 10 by using 1mol/L ammonia water, filtering to remove impurities to obtain a hydrophobically modified lignin solution, and then using 1mol/L H 2 SO 4 And regulating the pH value of the solution to be 3 to separate out lignin to form lignin particle dispersion.
(3) Preparation of W/O/W type multiple emulsion: firstly, adding 2.5g of deionized water into 7.5g of a mixed solution of ethyl acetate and n-butanol containing 6wt% span-60, wherein the mass ratio of the ethyl acetate to the n-butanol is 6:1, and emulsifying for 5min at 26000rpm by using a homogenizer to obtain W/O colostrum; then, 70g of 10wt% hydrophobically modified lignin particle dispersion was used as an external aqueous phase, and the W/O primary emulsion obtained above was added to the external aqueous phase, and emulsified at 1000rpm for 40min to obtain a W/O/W type multiple emulsion.
(4) Preparing lignin porous microspheres: under the conditions that the temperature is 35 ℃, the vacuum degree is 0.07MPa and the rotating speed is 60rpm, performing rotary evaporation for 60min, and performing centrifugal drying to obtain the lignin porous microspheres.
Example 4
(1) Preparation of hydrophobic lignin: dissolving 10g of acid-out lignin powder of dried straw pulp black liquor in 100g of acetone solution containing 1.5g of vinylpyridine salt, and reacting at room temperature with N 2 Under the atmosphere, the cobalt source irradiation is continuously carried out until the absorbed dose is 30kGy and the radiation dose rate is 3kGy/h. And finally, carrying out rotary steaming and drying on the obtained mixed solution to obtain the hydrophobic modified lignin powder.
(2) Preparation of lignin particle dispersion: dispersing 0.5g of the hydrophobically modified lignin obtained in the step (1) in 100g of water, adjusting the pH value to 11 by using 1mol/L KOH solution, filtering and removing impurities to obtain a hydrophobically modified lignin solution, and adjusting the pH value of the system to 3 by using 1mol/L HCl solution to separate out the lignin to form a lignin particle dispersion.
(3) Preparation of W/O/W type multiple emulsion: first, 1.25g of deionized water was added to 8.75g of a mixed solution of ethyl acetate and cyclopentanone containing 0.5wt% of PGPR in a mass ratio of 9:1, and emulsified for 5min at 16000rpm using a homogenizer to obtain W/O colostrum; then 40g of 0.5wt% hydrophobically modified lignin particle dispersion is used as an external water phase, the obtained W/O primary emulsion is added into the external water phase, and the mixture is emulsified for 30min at 1000rpm to obtain W/O/W type multiple emulsion.
(4) Preparing lignin porous microspheres: under the conditions that the temperature is 25 ℃, the vacuum degree is 0.09MPa and the rotating speed is 60rpm, performing rotary evaporation for 60min, and performing centrifugal drying to obtain the lignin porous microspheres.
Example 5
(1) Preparation of hydrophobic lignin: dissolving 10g of acid-out lignin powder of dry reed pulp black liquor in 100g of acetone solution containing 0.5g of styrene, and carrying out N reaction at room temperature 2 Under the atmosphere, the cobalt source irradiation is continuously carried out until the absorbed dose is 10kGy and the radiation dose rate is 0.5kGy/h. And finally, carrying out rotary steaming and drying on the obtained mixed solution to obtain the hydrophobic modified lignin powder.
(2) Preparation of lignin particle dispersion: dispersing 5g of the hydrophobically modified lignin obtained in the step (1) in 100g of water, adjusting the pH to 10 by using 1mol/L ammonia water solution, filtering to remove impurities to obtain a hydrophobically modified lignin solution, and adjusting the pH of the system to 4 by using 1mol/L HCl solution to separate out lignin to form a lignin particle dispersion.
(3) Preparation of W/O/W type multiple emulsion: firstly, adding 2g of deionized water into 8g of mixed solution of ethyl acetate and n-butanol containing 3wt% span-60, wherein the mass ratio of the ethyl acetate to the n-butanol is 4:1, and emulsifying for 5min at 22000rpm by using a homogenizer to obtain W/O primary emulsion; then 90g of 5wt% of hydrophobic modified lignin particle dispersion liquid is used as an external water phase, the obtained W/O primary emulsion is added into the external water phase, and emulsification is carried out for 20min at 2000rpm, so as to obtain W/O/W type multiple emulsion.
(4) Preparing lignin porous microspheres: and (3) exposing the obtained W/O/W type multiple emulsion to normal pressure at the temperature of 25 ℃, standing for 24 hours to volatilize an oil phase, and centrifuging and drying to obtain the lignin porous microspheres.
Example 6
(1) Preparation of hydrophobic lignin: dissolving 10g of acid-out lignin powder of dry bagasse pulp black liquor in 100g of acetone solution containing 1g of acrylamide, uniformly mixing, and carrying out N treatment at room temperature 2 Under the atmosphere, the cobalt source irradiation is continuously carried out until the absorbed dose is 40kGy and the radiation dose rate is 5kGy/h. And finally, carrying out rotary steaming and drying on the obtained mixed solution to obtain the hydrophobic modified lignin powder.
(2) Preparation of lignin particle dispersion: dispersing 0.5g of the hydrophobically modified lignin obtained in the step (1) in 100g of water, adjusting the pH value to 12 by using 1mol/L NaOH solution, filtering and removing impurities to obtain a hydrophobically modified lignin solution, and adjusting the pH value of the system to 3 by using 1mol/L KOH solution to separate out the lignin to form a lignin particle dispersion.
(3) Preparation of W/O/W type multiple emulsion: first, 2g of deionized water was added to 8g of ethyl acetate containing 6wt% of PGPR, and the mixture was emulsified at 16000rpm for 10min using a homogenizer to obtain W/O colostrum; then 40g of 0.5wt% hydrophobically modified lignin particle dispersion was used as an external aqueous phase, and the obtained W/O colostrum was added to the external aqueous phase, and emulsified for 20min at 3000rpm using a homogenizer to obtain a W/O/W type multiple emulsion.
(4) Preparing lignin porous microspheres: performing rotary evaporation for 50min at 35 deg.C, vacuum degree of 0.07MPa and rotation speed of 50rpm, and centrifuging and drying.
Example 7
(1) Preparation of hydrophobic lignin: dissolving 10g of acid-out lignin powder of dried wood pulp black liquor in 100g of acetone solution containing 2g of dodecyl vinyl ether, and adding N at room temperature 2 Under the atmosphere, the cobalt source irradiation is continuously carried out until the absorbed dose is 60kGy and the radiation dose rate is 5kGy/h. And finally, carrying out rotary steaming and drying on the obtained mixed solution to obtain the hydrophobic modified lignin powder.
(2) Preparation of lignin particle dispersion: dispersing 2g of the hydrophobically modified lignin obtained in the step (1) in 100g of water, adjusting the pH to 11 by using 1mol/L NaOH solution, filtering to remove impurities to obtain a hydrophobically modified lignin solution, and adjusting the pH of the system to 3 by using 1mol/L HCl solution to separate out lignin to form a lignin particle dispersion.
(3) Preparation of W/O/W type multiple emulsion: firstly, adding 2.5g of deionized water into 7.5g of ethyl acetate containing 2wt% of PGPR and 6wt% of abamectin, and emulsifying for 10min at 16000rpm by using a homogenizer to obtain W/O colostrum; then 40g of hydrophobically modified lignin particle dispersion with the concentration of 2wt% is used as an external water phase, the obtained W/O primary emulsion is added into the external water phase, and the mixture is emulsified for 30min at 2000rpm, thus obtaining W/O/W type multiple emulsion.
(4) Preparing lignin porous microspheres: and (3) exposing the obtained W/O/W type multiple emulsion to normal pressure at 35 ℃, standing for 12h, volatilizing an oil phase, and centrifugally drying to obtain the avermectin-encapsulated lignin porous microspheres.
Description of the effects of the examples:
the effects will be described by taking example 1 and example 7 as examples.
FIG. 1 is the contact angle of water on the lignin film before and after hydrophobic modification by irradiation of example 1. The contact angle of water on the unmodified Alkali Lignin (AL) film is 75 +/-2 degrees, and the contact angle on the hydrophobically modified lignin (RM-AL) film is 90 +/-1 degrees, which indicates that the hydrophobicity of the modified alkali lignin is enhanced. FIG. 2 is an infrared spectrum of lignin before and after the hydrophobic modification by irradiation in example 1. Compared with the raw material alkali lignin, the alkali lignin after radiation modification is 2933cm -1 And 1033cm -1 The absorption peaks at these two positions are clearly enhanced. This is due to the increase of ether and methylene linkages in the molecular structure of the alkali lignin after reaction with the hydrophobic monomer dodecyl vinyl ether, indicating successful grafting of dodecyl vinyl ether onto the alkali lignin.
Fig. 3 is an SEM image of the lignin porous microspheres prepared in example 1, which have smooth surfaces and regular spherical shapes, and some of the microspheres have small pores on the surfaces. Fig. 4 is a SEM image of a cross section of the lignin porous microsphere prepared in example 1, which shows that the microsphere has a porous structure and contains a plurality of interconnected pores. As is clear from fig. 3 and 4, the lignin particles are dissolved in the oil phase and then volatilize and precipitate out as the oil phase evaporates, thereby forming a smooth outer surface. Meanwhile, evaporation of the internal aqueous phase at the later stage of the drying process generates a large number of holes inside the microspheres.
The lignin porous microspheres obtained in example 1 are applied to adsorbing heavy metal ions Pb 2+ . The specific application operation is as follows: 50mL of Pb with the concentration of 500mg/L is transferred 2+ The solution was adjusted to pH 5 (error. + -. 0.03) in a 100mL Erlenmeyer flask with 0.1mol/L dilute nitric acid, 50mg of a sample of lignin microspheres was added and shaken at 150rpm for 5h at 25 ℃. After completion of the adsorption, an appropriate amount of the clear solution was filtered through a 0.22 μm aqueous filter head, and the filtrate was diluted 30 times (1% HNO content) 3 Solution), and testing by AA-6800 type atomic absorption spectrometer to obtain the Pb of lignin porous microsphere 2+ The amount of adsorbed was 140mg/g.
In example 7, the encapsulation efficiency of the loaded lignin porous microspheres to abamectin is 89.95%, and the drug loading rate is 33.61wt%. Fig. 5 shows the photolysis resistance of the lignin porous drug-loaded microspheres prepared in example 7. After 12 hours of irradiation under the ultraviolet light of 310nm, the content of the original drug AVM is suddenly reduced, and the effective retention rate of the AVM is only 5.3 percent after 72 hours of irradiation. The retention rate of the AVM encapsulated in the lignin porous microspheres can still reach 51.5% after the ultraviolet light is continuously irradiated for 72 hours, which shows that the lignin as a spherical material has a good protection effect on the photosensitive pesticide abamectin, and the light stability of the AVM is effectively improved.
The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.

Claims (10)

1. A preparation method of lignin porous microspheres based on W/O/W type multiple emulsion solvent volatilization is characterized by comprising the following steps:
(1) Performing high-energy radiation hydrophobic modification on lignin, dispersing the hydrophobic modified lignin in water, adding alkali to dissolve and filter the hydrophobic modified lignin, and then adding acid to adjust the pH value to separate out the hydrophobic modified lignin in a particle form, so as to obtain a hydrophobic modified lignin external water phase;
(2) Adding water into the oil phase containing the surfactant, emulsifying to obtain W/O primary emulsion, adding the W/O primary emulsion into the hydrophobic modified lignin external water phase, and emulsifying to obtain W/O/W type multiple emulsion;
(3) Drying the W/O/W type multiple emulsion to obtain porous microspheres;
the surfactant in the step (2) is at least one of Span-60 and polyglycerol ricinoleate; the oil phase is ethyl acetate, or mixed solution of ethyl acetate and cyclopentanone in the mass ratio of 4:1: -9:1, or mixed solution of ethyl acetate and n-butanol in the mass ratio of 4:1-9:1.
2. The preparation method of the lignin porous microspheres based on W/O/W type multiple emulsion solvent volatilization in the claim 1, characterized in that, the mass ratio of water to oil phase in the W/O colostrum in the step (2) is 1:3-1:7; the mass percent of the surfactant in the oil phase is 0.5-6%;
the mass ratio of the W/O colostrum to the outer water phase of the hydrophobically modified lignin in the step (2) is 1:4-1:9; the mass percentage of the hydrophobic modified lignin particles in the external water phase is 0.5-10%.
3. The preparation method of the lignin porous microspheres based on W/O/W type multiple emulsion solvent volatilization according to claim 1, wherein the step (1) of hydrophobically modifying lignin by high-energy radiation comprises the following steps: dissolving lignin and a hydrophobic monomer in a solvent, uniformly dispersing, and continuously irradiating a cobalt source to a required absorption dose at room temperature in an N2 or inert gas atmosphere; wherein the absorption dose is 10-60 kGy, the radiation dose rate is 0.5-5 kGy/h, and the mass ratio of the lignin to the hydrophobic monomer is 1;
the hydrophobic monomer is at least one of dodecyl vinyl ether, methyl acrylate, vinyl trimethoxy silane, styrene, vinyl pyridinium and acrylamide.
4. The preparation method of the lignin porous microspheres based on W/O/W type multiple emulsion solvent volatilization according to claim 1, characterized in that the drying treatment in step (3) is: standing at 25-35 ℃ under normal pressure to volatilize the oil phase for 12-24 h, and then centrifugally drying; or rotationally evaporating the oil phase for 30-60 min at 25-35 ℃, the vacuum degree of 0.07-0.09 MPa and the rotating speed of 30-60 rpm, and then centrifugally drying.
5. The preparation method of lignin porous microspheres based on W/O/W type multiple emulsion solvent volatilization according to claim 1, characterized in that the alkali in step (1) is at least one of sodium hydroxide, potassium hydroxide and ammonia water; adding alkali to adjust the pH value to 10-12;
the acid in the step (1) is at least one of hydrochloric acid, sulfuric acid and acetic acid; adding acid to adjust the pH value to 3-5.
6. The preparation method of the lignin porous microspheres based on W/O/W type multiple emulsion solvent volatilization according to claim 1, characterized in that the W/O colostrum in the step (2) is emulsified and sheared at 16000-26000 rpm for 5-10 min; the W/O/W type multiple emulsion is stirred at high speed of 1000-3000 rpm for 20-40 min.
7. The preparation method of the lignin porous microspheres based on W/O/W type multiple emulsion solvent volatilization according to claim 1, wherein the mass ratio of the hydrophobically modified lignin in the step (1) to water is 0.05-1: 10;
the lignin in the step (1) is at least one of alkali lignin and enzymatic hydrolysis lignin; the alkali lignin is at least one of wood pulp black liquor, bamboo pulp black liquor, straw pulp black liquor, reed pulp black liquor and bagasse pulp black liquor, and is subjected to acid precipitation drying to obtain acid precipitation lignin powder; the enzymatic hydrolysis lignin is lignin separated and extracted from residues after alcohol is prepared by fermenting cellulose in plant raw materials.
8. The preparation method of the lignin porous microspheres based on W/O/W type multiple emulsion solvent volatilization according to claim 3, characterized in that the solvent in the lignin hydrophobic modification is acetone, and the mass ratio of lignin to acetone is 1.
9. A lignin porous microsphere based on W/O/W type multiple emulsion solvent volatilization is prepared by the method of any one of claims 1 to 8.
10. The application of the lignin porous microspheres based on W/O/W type multiple emulsion solvent volatilization in controlled drug release and heavy metal adsorption in water treatment of claim 9.
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CN101249077A (en) * 2008-04-14 2008-08-27 西南交通大学 Preparation of degradable pollutant polyalcohol stephanoporate microballoons and uses thereof
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CN113181846A (en) * 2021-04-08 2021-07-30 华南理工大学 Preparation method of pure lignin microcapsule based on Pickering emulsion solvent volatilization

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US5980947A (en) * 1990-06-13 1999-11-09 Eisai Co., Ltd. Process for producing drug-containing microspheres by oil-in-water evaporation process
CN101249077A (en) * 2008-04-14 2008-08-27 西南交通大学 Preparation of degradable pollutant polyalcohol stephanoporate microballoons and uses thereof
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