CN113388896B - Preparation method of hydrophobic oleophylic nanocellulose based on immobilized enzyme chemistry-oxidative degumming - Google Patents
Preparation method of hydrophobic oleophylic nanocellulose based on immobilized enzyme chemistry-oxidative degumming Download PDFInfo
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Abstract
The invention discloses green intrinsic hydrophobic oleophylic nano-cellulose and a preparation method thereof. The method takes hemp stems as raw materials, takes independently developed immobilized enzyme-chemical degumming agent and oxidation degumming agent as cooking media, and prepares the nano-cellulose with intrinsic hydrophobic and lipophilic properties in an efficient and green way by alternately cooking the hemp stems and the chemical degumming agent and the oxidation degumming agent. The diameter of the nano-cellulose prepared by the method is 4-12 nm, the length-diameter ratio is large, the nano-cellulose has intrinsic hydrophobicity and lipophilicity without modification, the problem that the nano-cellulose prepared by the prior art is hydrophilic and oleophobic and needs to be further modified to improve the lipophilicity so as to realize the dispersion of the nano-cellulose in a hydrophobic polymer is solved, and the problem of serious pollution caused by a large amount of acid or alkali consumption in the existing nano-cellulose preparation process is well solved by adopting the novel immobilized enzyme-chemical degumming agent with low salt content.
Description
Technical Field
The invention relates to nanocellulose and a preparation method thereof, in particular to green intrinsic clean high-efficiency hydrophobic oleophylic nanocellulose and a preparation method thereof.
Background
China is a big country for planting hemp plants, the yield is the first world, but the current application focuses on the parts of bast and seed, and the like, and a large amount of residual hemp stalks are usually discarded or burned as agricultural wastes, so that not only is the resource wasted, but also the environmental pollution is caused. The hemp stems are recycled, so that the environment-friendly benefit is achieved, the economic cost of the hemp fiber industry can be reduced to a certain extent, and the development of the hemp industry can be further expanded.
Immobilizing pectinase, which means that pectinase can be immobilized on a substrate, has an effect on increasing the reuse of pectinase and regulating catalytic properties. The method can improve the stability of pectinase, reduce cost and improve the separation and purification of pectinase. The calcium alginate is the most common natural polymer, but has the problems of low strength, poor water resistance and the like, the invention utilizes the sodium alginate with electronegativity and the protein with electropositivity (under alkaline conditions) to compound and construct a polyelectrolyte compound system, and then calcium chloride reacts with the sodium alginate to form a multiple cross-linked structure, thereby enhancing the strength of a matrix, realizing the effective controlled release of pectinase, improving the heat resistance of the pectinase and further improving the efficient removal of pectin and lignin.
Nanocellulose is a nano-scale product of the treatment of cellulose fibers. Compared with the traditional cellulose material, the nano-cellulose has the characteristics of large specific surface area, large crystallinity, large tensile strength, high modulus, biodegradability, light weight and the like, is considered as the most promising composite material reinforcement, and has wide market space in various fields such as environmental protection, papermaking, packaging, food, energy, composite materials, medicine and the like.
The nano-cellulose can be derived from plants, animals, microorganisms and the like, is abundant in reserves, and is one of the materials which are difficult to artificially synthesize by human beings recently. Nanocellulose can be classified into Cellulose Nanocrystals (CNC), Cellulose Nanofibrils (CNF), bacterially synthesized nanofibers (BNC) and electrospun fibers (ECC)4 according to the difference in material source, preparation method and fiber morphology. The preparation method comprises mechanical method, chemical method and enzyme treatment method. In any case, the preparation process basically comprises four steps, namely: (1) pre-treatment, namely removing surface impurities and crushing through the processes of grinding, cleaning and the like; (2) separating the inner layer of fibrous cellulose from the primary cell wall and the large fiber of the plant and the secondary cell wall by chemical, mechanical or enzyme treatment; (3) separating and pulverizing cellulose existing in microfibril into nanocellulose by hydrolysis or mechanical disruption; (4) nanocellulose is modified to have flow distortion for subsequent processing and dispersibility in a matrix.
Disclosure of Invention
In view of the problems in the prior art, the invention aims to provide a method for preparing green, intrinsic, clean, high-efficiency, hydrophobic and oleophylic nanocellulose. The invention takes hemp stems as raw materials, takes independently developed immobilized enzyme-chemical degumming agent and oxidation degumming agent as cooking media, and prepares nano-cellulose with hydrophobic and lipophilic properties in a high-efficiency and green way by an alternate cooking method. The diameter of the nano-cellulose prepared by the method is 4-12 nm, the length-diameter ratio is large, the nano-cellulose has intrinsic hydrophobicity and lipophilicity without modification, the problem that the lipophilicity of the nano-cellulose prepared by the prior art can be improved only by chemical modification or surface finishing, and the nano-cellulose is dispersed in a hydrophobic polymer is solved, and the preparation method adopts a novel immobilized enzyme-chemical degumming agent, so that the problems of serious pollution caused by large consumption of acid or alkali in the preparation process of the existing nano-cellulose and non-repeatability in the use of enzyme in the existing nano-cellulose biological method are well solved.
The purpose of the invention is realized by the following technical scheme.
The technical scheme of the invention is to provide an immobilized enzyme-chemical degumming agent, which comprises the following components in percentage by mass: 10.50-13.00% of immobilized enzyme, 0.20-0.40% of sodium hydroxide, 0.10-0.20% of sodium carbonate, 0.15-0.25% of sodium chloride, 0.15-0.25% of calcium chloride, 0.05-0.08% of sodium formate and the balance of water, wherein the immobilized enzyme is prepared by immobilizing pectinase in a cross-linking matrix formed by sodium alginate, protein and calcium chloride.
In the above technical scheme, the preparation method of the immobilized enzyme comprises: dripping the water solution dissolved with sodium alginate, protein and pectinase into calcium chloride solution to form colloidal particles, filtering to obtain immobilized pectinase microspheres, washing, dehydrating, and freeze drying to obtain immobilized enzyme. Preferably, the aqueous solution dissolved with the sodium alginate, the protein and the pectinase is stirred and dispersed at room temperature, is added into a syringe after centrifugal deaeration, is extruded by a peristaltic pump through a nozzle of the syringe, and is dripped into the calcium chloride solution to form the cross-linked matrix. Washing the microspheres of the immobilized pectinase obtained by filtering with a Tris-HCl buffer solution, dehydrating, freezing at 14-18 ℃ for 24h, and then freeze-drying at-55 ℃ for 72h to obtain the immobilized pectinase with a microporous structure.
In the technical scheme, the mass percentage of the sodium alginate, the protein and the pectinase in the aqueous solution is 1-3: 0-20: 10-15, and the mass percentage concentration of the calcium chloride solution is 5-10%.
In the above technical scheme, the protein is one or more of feather keratin, krill protein, and silk fibroin.
The invention also provides a preparation method of the hydrophobic oleophilic type nano fiber, which comprises the step of alternately cooking straws in the immobilized enzyme-chemical degumming agent and the oxidation degumming agent.
In the technical scheme, the oxidation degumming agent comprises the following components in percentage by mass: 1-4% of sodium chlorite, 0.6-1.0% of glacial acetic acid and the balance of water.
In the technical scheme, the number of times of alternate cooking is 4-6, and each time of alternate cooking comprises the following steps: adding an immobilized enzyme-chemical degumming agent into the straws, cooking for 45-60 min at 60-80 ℃, washing to remove the immobilized enzyme-chemical degumming agent, adding an oxidation degumming agent, cooking the straws for 45-60 min at 70-80 ℃, washing to remove the oxidation degumming agent, wherein stirring is carried out in the cooking process at the stirring speed of 100-500 r/min.
In the technical scheme, the cooking liquor obtained by alternately cooking is subjected to suction filtration to obtain the nano cellulose fibrils, a proper amount of water is added, the concentration of the nano cellulose fibrils is adjusted to be 1% -2%, and ball milling is carried out to obtain the solution containing the nano cellulose fibrils, wherein the viscosity of the solution is 80-143 Pa.s. The ball milling time is preferably 60-120 min, and the nanocellulose fibers with the diameters of 4-12 nm and the lengths of 200-1000 nm are obtained after ball milling.
In the technical scheme, the mass ratio of the straw to the immobilized enzyme-chemical degumming agent is 1: 8-1: 12, and the mass ratio of the straw to the oxidation degumming agent is 1: 8-1: 12.
In the technical scheme, the straw is pretreated, and the pretreatment steps are as follows: and (3) washing the hemp stalks with desalted water for 3-4 times, drying at 100-105 ℃, and then crushing with a ball mill, wherein the particle size is controlled to be 40-60 meshes. The desalted water is water from which calcium, magnesium and chloride ions are removed.
In the technical scheme, the straw is hemp stalk. The hemp stalk is derived from the stem of a hemp plant. The bast fiber crops include hemp, ramie, jute, ramie, flax, kendir, kenaf, etc.
According to another technical scheme, the invention provides application of the intrinsic hydrophobic oleophilic type nano-fiber prepared by the preparation method in preparation of reinforced modified materials, substance separation materials, heat insulation materials, biomedical materials and intelligent responsive materials of polymer matrix composite materials. The nano-cellulose prepared by the method has the diameter of 4-12 nm, the length-diameter ratio is large, and the nano-cellulose has intrinsic hydrophobicity and lipophilicity without modification, is particularly suitable for enhancing modification of polymer matrix composite materials, and is also suitable for material separation, heat insulation and preservation, biomedical materials, intelligent responsive materials and the like.
In the invention, pectin, lignin and the like in the straw are removed by alternately cooking and continuously enhancing shearing action of the immobilized enzyme-chemical degumming agent and the oxidation degumming agent, meanwhile, the action among microfibers is weakened, the fibers are realized to obtain the nanocellulose fibers with high length-diameter ratio, and the yield and the fiber fineness of the nanocellulose are determined by the number of alternately cooking. The number of times of alternate cooking of the immobilized enzyme-chemical degumming agent and the oxidation degumming agent is preferably 4-6 times. The length of the nano-cellulose in the cooking liquor obtained after the alternate cooking can be regulated and controlled through ball milling. The ball milling time is preferably 60-120 min, and the length of the nanocellulose filaments can be controlled within 200-1000 nm under the ball milling time.
In the present invention, the immobilized enzyme is prepared by immobilizing pectinase in a cross-linked matrix formed from sodium alginate, protein and calcium chloride. The complex of sodium alginate and protein has two kinds of polymers in negative and positive polarity separately in alkali condition, and can raise the colloid strength and alkali resistance through the positive and negative points and effect. In the preparation process, calcium chloride, sodium alginate and protein are reacted to form a multiple cross-linked structure, so that the colloid strength is improved; the freeze-drying is used for forming pores to provide channels for enzyme release, and the results are favorable for improving uncontrollable release and improving the reusability of the enzyme. The compound form of the sodium alginate, the protein and the pectinase in the immobilized enzyme prepared by the method is physical mixing, and the pectinase exists in a compound network formed by the sodium alginate (calcium) and the protein in a dispersed form, so that the controllable release is facilitated.
Compared with the prior art, the invention has the following beneficial effects:
(1) the invention takes hemp stems as raw materials, takes independently developed immobilized enzyme-chemical degumming agent and oxidation degumming agent as cooking media, and prepares the nano cellulose with intrinsic clean efficient hydrophobic lipophilic property in a high-efficiency green way by an alternate repeated cooking method. The fourth process of preparing the common nano-cellulose is omitted, the process is greatly shortened, the production cost is reduced, the developed nano-cellulose has good dispersibility in a polymer aggregate, and the application of the developed nano-cellulose in a polymer matrix composite is promoted.
(2) The reuse of pectinase and the regulation of catalytic performance are improved by using immobilized enzyme, and the immobilized enzyme, namely the chemical degumming agent and the oxidation degumming agent can be reused, so that the reuse rate of the cooking liquor is improved, and the cost is reduced.
(3) An immobilized enzyme-chemical degumming agent (primary cooking liquor) is formed by using an immobilized enzyme and a cleaning additive, and the pectin and lignin are efficiently removed by using the efficient decomposition function of the enzyme on the pectin, the protection function of the cleaning additive on the enzyme and the efficient swelling function of the cleaning additive on the straw material; the supplementary cooking is carried out by a composite oxidant formed by a mixture of sodium chlorite and acetic acid, so as to further reduce the content of lignin. The method uses the alternate cooking of the immobilized enzyme-chemical degumming agent and the oxidation degumming agent oxidant, and utilizes the synergistic effect of the two agents, so that the separation efficiency of pectin and lignin can be obviously improved, the repeated cooking times and time can be reduced, and the efficient preparation of the nano cellulose can be realized.
(4) According to the immobilized enzyme-chemical degumming agent, 0.20-0.40% of sodium hydroxide is used for replacing 5.0-8.0% of potassium hydroxide for preparing nano-cellulose by an alkaline method, the immobilized enzyme-chemical degumming agent is low in salt content, the total salt content is 0.65-1.18%, the total salt content is less than 0.8% under the optimal condition, pectinase is immobilized for reuse, the environmental pollution is effectively reduced, and meanwhile, the production cost is reduced.
(5) The nano-cellulose prepared by the method has the diameter of 4-12 nanometers, the length-diameter ratio is large, and the nano-cellulose has intrinsic clean high-efficiency hydrophobic lipophilicity without modification, so that the nano-cellulose is particularly suitable for enhancing modification of polymer matrix composite materials and is also suitable for material separation, heat insulation, heat preservation, biomedical use and the like.
Drawings
Fig. 1 shows a transmission electron micrograph of the nanocellulose filaments shown in example 5.
Fig. 2 shows a transmission electron micrograph of the nanocellulose filaments shown in example 6.
Fig. 3 shows a transmission electron micrograph of the nanocellulose filaments shown in example 7.
Fig. 4 shows a transmission electron micrograph of the nanocellulose filaments shown in example 8.
FIG. 5 shows the water contact angle of the nanocellulose membranes shown in example 8.
FIG. 6 shows the oil contact angle of the nanocellulose membranes shown in example 8.
FIG. 7 is a photograph showing the sodium alginate-coated enzyme prepared in example 1.
FIG. 8 shows photographs of the sodium alginate and krill protein-coated enzymes prepared in example 2.
FIG. 9 shows photographs of the sodium alginate and feather keratin-coated enzyme prepared as shown in example 4.
Detailed Description
The following non-limiting examples are presented to enable those of ordinary skill in the art to more fully understand the present invention and are not intended to limit the invention in any way. In the following examples, unless otherwise specified, the experimental methods used were all conventional methods, and materials, reagents and the like used were all available from biological or chemical companies.
The technical scheme of the invention is further specifically described by the following embodiments.
Materials and instruments used in the examples:
sodium alginate: purchased from Qingdao Mingyue algae group, Inc. and having a viscosity of 540 CPS.
Krill protein: the method is characterized by taking antarctic krill powder as a raw material, and obtaining the antarctic krill powder by subtraction extraction, wherein the molecular weight is 66-140 Kda.
Silk fibroin: the method is characterized in that recycled silk is used as a raw material and is obtained through subtraction extraction, and the molecular weight is 10-100 Kda.
Ball mill: changshado apparatus DECO Deke high energy planetary ball mill "DECO-PBM-V-0.4L.
Whiteness chromaticity tester: YT-48A, Hangzhou research science and technology Co.
Example 1
Adding 4g of sodium alginate into 200g of room-temperature water, heating to 80 ℃, and dissolving for 90min to obtain a sodium alginate solution; adding 10G of pectinase into the solution, stirring and dispersing for 120min at room temperature, centrifuging and defoaming, adding an injector, extruding by a peristaltic pump through a 20G needle, passing through an 8cm air curtain, feeding a calcium chloride solution with the stirring speed of 300rpm and the mass fraction of 6%, gelatinizing for 20min, and filtering to separate immobilized enzyme microspheres (shown in figure 7); washing with Tris-HCl (8%, 8g/1000mL) solution for 4-5 times, dewatering, pouring into a culture dish, freezing at 14-18 ℃ for 24h, and freeze-drying at-55 ℃ for 72h to obtain the immobilized pectinase with the microporous structure.
Example 2
Taking 100g of distilled water, adjusting the pH value to 8 by using sodium hydroxide, adding 0.4g of krill protein, stirring for dissolving, adding 1.6g of sodium alginate after the protein is dissolved, heating to 60 ℃, and continuously dissolving for 90min to obtain a sodium alginate/krill protein solution; adding 12G of pectinase into the solution, stirring and dispersing for 120min at room temperature, centrifuging and defoaming, adding an injector, extruding by a peristaltic pump through a 20G needle, passing through an 8cm air curtain, feeding a calcium chloride solution with the stirring speed of 300rpm and the mass fraction of 6%, gelatinizing for 20min, and filtering to separate immobilized enzyme microspheres (shown in figure 8); washing with Tris-HCl (8%, 8g/1000mL) solution for 4-5 times, dewatering, pouring into a culture dish, freezing at 14-18 ℃ for 24h, and freeze-drying at-55 ℃ for 72h to obtain the immobilized pectinase with the microporous structure.
Example 3
Taking 100g of distilled water, adjusting the pH value to 8 by using sodium hydroxide, adding 0.2g of krill protein, stirring for dissolving, adding 1.8g of sodium alginate after the protein is dissolved, heating to 60 ℃, and continuously dissolving for 90min to obtain a sodium alginate/krill protein solution; adding 13G of pectinase into the solution, stirring and dispersing for 120min at room temperature, centrifuging and defoaming, adding an injector, extruding by using a peristaltic pump through a 20G needle, passing through an 8cm air curtain, feeding a calcium chloride solution with the stirring speed of 300rpm and the mass fraction of 6%, gelatinizing for 20min, and filtering to separate immobilized enzyme microspheres; washing with Tris-HCl (8%, 8g/1000mL) solution for 4-5 times, dewatering, pouring into a culture dish, freezing at 14-18 ℃ for 24h, and freeze-drying at-55 ℃ for 72h to obtain the immobilized pectinase with the microporous structure.
Example 4
Taking 100g of distilled water, adjusting the pH value to 8 by using sodium hydroxide, adding 0.4g of feather keratin, stirring for dissolving, adding 1.6g of sodium alginate after the protein is dissolved, heating to 60 ℃, and continuously dissolving for 90min to obtain a sodium alginate/feather keratin solution; adding 15G of pectinase into the solution, stirring and dispersing for 120min at room temperature, centrifuging and defoaming, adding an injector, extruding by a peristaltic pump through a 20G needle, passing through an 8cm air curtain, feeding a calcium chloride solution with the stirring speed of 300rpm and the mass fraction of 6%, gelatinizing for 20min, and filtering to separate immobilized enzyme microspheres (shown in figure 9); washing with Tris-HCl (8%, 8g/1000mL) solution for 4-5 times, dewatering, pouring into a culture dish, freezing at 14-18 ℃ for 24h, and freeze-drying at-55 ℃ for 72h to obtain the immobilized pectinase with the microporous structure.
Example 5
Immobilized enzyme-chemical degumming agent: the composite material comprises the following components in percentage by mass: 10.5% of immobilized enzyme (prepared in example 1), 0.40% of sodium hydroxide, 0.10% of sodium carbonate, 0.18% of sodium chloride, 0.16% of calcium chloride, 0.05% of sodium formate and 88.61% of water.
Oxidizing the degumming agent: the composite material comprises the following components in percentage by mass: 2% of sodium chlorite, 0.6% of acetic acid and 97.4% of water.
Primarily pulverizing hemp stalk straws, washing the straws with desalted water for 3-4 times, separating out soluble impurities, drying the straws at 100-105 ℃, crushing the straws by using a ball mill, and sieving the straws with a 60-mesh sieve. Taking 10g of hemp stalk straw powder screened below 60 meshes, adding 100mL of immobilized enzyme-chemical degumming agent, heating, stirring and cooking at 80 ℃ for 60min, recovering the immobilized enzyme-chemical degumming agent, washing with hot distilled water, and performing suction filtration for 4-5 times; then adding 100mL of oxidation degumming agent, heating, stirring and cooking for 60min at 80 ℃, recovering the oxidation degumming agent, washing with hot distilled water, and performing suction filtration for 4-5 times. Repeat the above step 4 times. Wherein the immobilized enzyme-chemical degumming agent and the oxidation degumming agent recovered after the first cooking are respectively 90mL for the second cooking; the immobilized enzyme-chemical degumming agent and the oxidation degumming agent recovered after the second cooking are respectively 80mL for the third cooking, and the cooking time is respectively 60 min. The immobilized enzyme-chemical degumming agent and the oxidation degumming agent recovered after the third cooking are respectively 70mL for the fourth cooking, and the cooking time is respectively 60 min.
And after cooking, carrying out suction filtration and washing on the solution to obtain nano cellulose fibrils, adding a certain amount of distilled water to prepare a solution with the concentration of the nano cellulose fibrils being 2%, and after ball milling for 75min, uniformly dispersing the fibers in the solution in a gel state to obtain the nano cellulose fibrils with the diameter of 8-10 nm and the length of 800-1000 nm (figure 1).
Example 6
Immobilized enzyme-chemical degumming agent: the composite material comprises the following components in percentage by mass: 10.5% of immobilized enzyme (prepared in example 2), 0.40% of sodium hydroxide, 0.10% of sodium carbonate, 0.18% of sodium chloride, 0.16% of calcium chloride, 0.05% of sodium formate and 88.61% of water.
Oxidizing the degumming agent: the composite material comprises the following components in percentage by mass: consists of sodium chlorite 2 wt%, acetic acid 0.6 wt% and water 97.4 wt%.
Primarily pulverizing hemp stalk straws, washing the straws with desalted water for 3-4 times, separating out soluble impurities, drying the straws at 100-105 ℃, crushing the straws by using a ball mill, and sieving the straws with a 60-mesh sieve. Taking 10g of hemp stalk straw powder screened below 60 meshes, adding 120mL of immobilized enzyme-chemical degumming agent, heating, stirring and cooking for 90min at 60 ℃, washing and filtering with hot distilled water for 4-5 times; then adding 100mL of oxidation degumming agent, heating, stirring and cooking for 90min at 70 ℃, recovering the oxidation degumming agent, washing with hot distilled water, and performing suction filtration for 4-5 times. Repeat the above step 4 times. Wherein the immobilized enzyme-chemical degumming agent and the oxidation degumming agent recovered after the first cooking for the second cooking are respectively 90 mL; the immobilized enzyme-chemical degumming agent and the oxidation degumming agent recovered after the second cooking for the third cooking are respectively 80mL, the immobilized enzyme-chemical degumming agent and the oxidation degumming agent recovered after the third cooking for the fourth cooking are respectively 70mL, and the cooking time is respectively 90 min. The immobilized enzyme-chemical degumming agent and the oxidation degumming agent recovered after the fifth cooking is performed by four times of cooking are respectively 60mL, and the cooking time is respectively 90 min.
And after cooking, carrying out suction filtration and washing on the solution to obtain nano cellulose fibrils, adding a certain amount of distilled water to prepare a solution with the concentration of the nano cellulose fibrils being 2%, and after ball milling for 90min, uniformly dispersing the fibers in the solution in a gel state to obtain nano cellulose fibril powder with the diameter of 3-5 nm and the length of 400-600 nm (figure 2).
Example 7
Immobilized enzyme-chemical degumming agent: the composite material comprises the following components in percentage by mass: 12.0% of immobilized enzyme (prepared in example 3), 0.35% of sodium hydroxide, 0.11% of sodium carbonate, 0.22% of sodium chloride, 0.21% of calcium chloride, 0.06% of sodium formate and 88.42% of water.
Oxidizing the degumming agent: the composite material comprises the following components in percentage by mass: 4% of sodium chlorite, 0.8% of acetic acid and 95.2% of water.
Primarily pulverizing hemp stalk straws, washing the straws with desalted water for 3-4 times, separating out soluble impurities, drying the straws at 100-105 ℃, crushing the straws by using a ball mill, and sieving the straws with a 60-mesh sieve. Taking 10g of hemp stalk straw powder screened below 60 meshes, adding 100mL of immobilized enzyme-chemical degumming agent, heating, stirring and cooking for 45min at 80 ℃, recovering the immobilized enzyme-chemical degumming agent, washing with hot distilled water, and performing suction filtration for 4-5 times; then adding 100mL of oxidation degumming agent, heating, stirring and cooking for 45min at 80 ℃, recovering the oxidation degumming agent, washing with hot distilled water, and performing suction filtration for 4-5 times. Repeat the above steps 5 times. Wherein the immobilized enzyme-chemical degumming agent and the oxidation degumming agent which are newly configured for the second cooking are respectively 90 mL; the amount of the immobilized enzyme-chemical degumming agent and the amount of the oxidation degumming agent which are newly configured for the third cooking are respectively 80mL, the amount of the immobilized enzyme-chemical degumming agent and the amount of the oxidation degumming agent which are newly configured for the fourth cooking are respectively 70mL, and the cooking time is respectively 45 min. The amount of the immobilized enzyme-chemical degumming agent and the oxidation degumming agent newly configured for the fifth cooking is respectively 60mL, and the cooking time is respectively 45 min.
And after cooking, carrying out suction filtration and washing on the solution to obtain nano cellulose fibrils, adding a certain amount of distilled water to prepare a solution with the concentration of the nano cellulose fibrils being 1%, carrying out ball milling for 60min, and uniformly dispersing the fibers in the solution in a gel state to obtain the nano cellulose fibrils with the diameter of 5-10nm and the length of 600-800 nm (figure 3).
Example 8
Immobilized enzyme-chemical degumming agent: the composite material comprises the following components in percentage by mass: 13% immobilized enzyme (prepared in example 4), 0.30% sodium hydroxide, 0.12% sodium carbonate, 0.22% sodium chloride, 0.22% calcium chloride, 0.07% sodium formate, and 87.69% water.
Oxidizing the degumming agent: the composite material comprises the following components in percentage by mass: 4% of sodium chlorite, 0.8% of acetic acid and 95.2% of water.
Primarily pulverizing hemp stalk straws, washing with desalted water for 3-4 times, separating out soluble impurities, drying at 100-105 ℃, crushing with a ball mill, and sieving with a 60-mesh sieve. Taking 10g of hemp stalk straw powder screened below 60 meshes, adding 100mL of immobilized enzyme-chemical degumming agent, heating, stirring and cooking at 80 ℃ for 60min, recovering the immobilized enzyme-chemical degumming agent, washing with hot distilled water, and performing suction filtration for 4-5 times; then adding 100mL of oxidation degumming agent, heating, stirring and cooking for 60min at 80 ℃, recovering the oxidation degumming agent, washing with hot distilled water, and performing suction filtration for 4-5 times. Repeat the above steps 3 times. Wherein the immobilized enzyme-chemical degumming agent recovered after the first cooking and the newly configured oxidation degumming agent for the second cooking are respectively 90 mL; the immobilized enzyme-chemical degumming agent recovered after the last secondary cooking and the newly configured oxidation degumming agent are respectively 80mL for the third cooking, and the cooking time is respectively 60 min; the immobilized enzyme-chemical degumming agent recovered after the third cooking and the newly configured oxidation degumming agent are respectively 70mL for the fourth cooking, and the cooking time is respectively 60 min; the immobilized enzyme-chemical degumming agent recovered after the fifth cooking is performed by four times of cooking and the newly configured oxidation degumming agent are respectively 60mL, and the cooking time is respectively 60 min. The immobilized enzyme-chemical degumming agent recovered after the fifth cooking and the newly configured oxidation degumming agent are respectively 50mL in the sixth cooking, and the cooking time is respectively 60 min. And after cooking, carrying out suction filtration and washing on the solution to obtain nano cellulose fibers, adding a certain amount of distilled water to prepare a solution with the concentration of the nano cellulose fibers being 2%, and after ball milling for 120min, uniformly dispersing the fibers in the solution in a gel state to obtain the nano cellulose fibers with the diameter of 2-3 nm and the length of 200-400 nm (figure 4). The obtained nanocellulose solution was formed into a cellulose film, and it was found that the cellulose film has a contact angle of 108.4 ° with water (fig. 5) and a contact angle of 15.9 ° with edible oil (fig. 6) and exhibits an intrinsic cleaning, highly effective hydrophobic and oleophilic characteristic.
Example 9
Table 2 shows the results of measuring the whiteness of the nanocellulose prepared in examples 4 to 7.
TABLE 1 nanocellulose fiber whiteness
The embodiments described above are intended to illustrate the technical solutions of the present invention in detail, and it should be understood that the above-mentioned embodiments are only specific embodiments of the present invention, and are not intended to limit the present invention, and any modification, supplement or similar substitution made within the scope of the principles of the present invention should be included in the protection scope of the present invention.
Claims (8)
1. The immobilized enzyme-chemical degumming agent is characterized by comprising the following components in percentage by mass: 10.50-13.00% of immobilized enzyme, 0.20-0.40% of sodium hydroxide, 0.10-0.20% of sodium carbonate, 0.15-0.25% of sodium chloride, 0.15-0.25% of calcium chloride, 0.05-0.08% of sodium formate and the balance of water, wherein the immobilized enzyme is prepared by dripping aqueous solution dissolved with sodium alginate, protein and pectinase into calcium chloride solution to form colloidal particles, filtering to obtain microspheres of the immobilized enzyme, washing, dehydrating and freeze-drying;
the mass ratio of the sodium alginate to the protein to the pectinase in the aqueous solution is 1-3: 0.2-0.4: 10-15, and the mass percentage concentration of the calcium chloride solution is 5-10%.
2. The immobilized enzyme-chemical degumming agent according to claim 1, wherein the protein is one or more of feather keratin, krill protein, silk fibroin.
3. A method for preparing hydrophobic oleophilic nanofiber, which comprises the step of alternately cooking straw in the immobilized enzyme-chemical degumming agent and the oxidation degumming agent according to claim 1 or 2.
4. The preparation method of claim 3, wherein the oxidation degumming agent comprises the following components in percentage by mass: 1-4% of sodium chlorite, 0.6-1.0% of glacial acetic acid and the balance of water.
5. The preparation method according to claim 3, wherein the number of the alternate cooking is 4 to 6, and each alternate cooking step is: adding an immobilized enzyme-chemical degumming agent into the straws, cooking for 45-60 min at 60-80 ℃, washing to remove the immobilized enzyme-chemical degumming agent, adding an oxidation degumming agent, cooking for 45-60 min at 70-80 ℃, washing to remove the oxidation degumming agent, wherein stirring is carried out in the cooking process at the stirring speed of 100-500 r/min.
6. The preparation method of the immobilized enzyme-chemical degumming agent, according to claim 3, is characterized in that the mass ratio of the straw to the immobilized enzyme-chemical degumming agent is 1: 8-1: 12, and the mass ratio of the straw to the oxidation degumming agent is 1: 8-1: 12.
7. The preparation method according to claim 3, wherein the straw is pretreated, and the pretreatment comprises the following steps: and (3) washing the hemp stalks with desalted water for 3-4 times, drying at 100-105 ℃, and then crushing with a ball mill, wherein the particle size is controlled to be 40-60 meshes.
8. The method of claim 3, wherein the straw is hemp stalk.
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| WO2013053210A1 (en) * | 2011-10-10 | 2013-04-18 | 青岛农业大学 | Immobilized carrier for pectinase and methods for preparing and immobilizing pectinase |
| CN107326453A (en) * | 2017-07-03 | 2017-11-07 | 晟颐天祥天然纤维科技有限公司 | One kind cleans degumming method of bast fiber |
| CN108004229A (en) * | 2017-12-25 | 2018-05-08 | 北京化工大学 | A kind of preparation of immobilized cellulase and its method for enzyme hydrolysis cellulose |
| CN111472190A (en) * | 2020-03-09 | 2020-07-31 | 齐齐哈尔大学 | Method for extracting high-purity straw cellulose by utilizing immobilized enzyme technology for pretreatment |
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| WO2013053210A1 (en) * | 2011-10-10 | 2013-04-18 | 青岛农业大学 | Immobilized carrier for pectinase and methods for preparing and immobilizing pectinase |
| CN107326453A (en) * | 2017-07-03 | 2017-11-07 | 晟颐天祥天然纤维科技有限公司 | One kind cleans degumming method of bast fiber |
| CN108004229A (en) * | 2017-12-25 | 2018-05-08 | 北京化工大学 | A kind of preparation of immobilized cellulase and its method for enzyme hydrolysis cellulose |
| CN111472190A (en) * | 2020-03-09 | 2020-07-31 | 齐齐哈尔大学 | Method for extracting high-purity straw cellulose by utilizing immobilized enzyme technology for pretreatment |
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