Method for preparing composite membrane by extracting aldehyde cellulose from tetrapanax papyriferus residues

Abstract

The invention discloses a method for preparing a composite membrane by extracting aldehyde cellulose from tetrapanax papyriferus residues, and belongs to the technical field of tetrapanax papyriferus residue recycling. The method comprises the following steps: dispersing tetrapanax papyriferus residue powder in a 0.5%-3% alkaline solution, reacting at 60-100 DEG C for 0.5-3 hours, and separating to obtain pretreated residues; adding the pretreated slag into an ionic liquid, heating at 50-120 DEG C for 0.5-3 hours, and adding 10-60 parts of deionized water to obtain a suspension; filtering the suspension, collecting intercepted liquid, adding an oxidizing agent, carrying out a reaction in a dark place, separating and collecting to obtain dialdehyde cellulose; and adding gelatin into the dialdehyde cellulose for compounding, and preparing a membrane to obtain the composite membrane. By controlling the content of aldehyde groups in the dialdehyde cellulose, the composite film can be endowed with excellent mechanical properties, so that the composite film has a wide application prospect.

Description

Technical Field

[0001] The present application belongs to the technical field of recycling and utilizing tongcao residues, and in particular, relates to a method for extracting aldehyde cellulose from tongcao residues to prepare a composite membrane. Background Art

[0002] Cellulose is currently the most abundant natural macromolecular renewable material, and products produced based on cellulose are widely used in various fields. Aldehyde cellulose is a cellulose derivative rich in active aldehyde groups obtained by oxidation of cellulose as a raw material under the action of an oxidant. Due to the presence of highly active aldehyde groups in the molecular chain, it is widely used in the fields of biomedicine, textile industry, sewage treatment, and active functional materials. However, the existing preparation process is to prepare aldehyde cellulose by adding a specific solvent such as an ionic liquid to a cellulose-like substance to dissolve it into a homogeneous system, and then adding an oxidant to the system. After the reaction is completed, the preparation process needs to add an additional additive to the reaction system to separate the reaction product from the homogeneous reaction system, which is not conducive to the separation and purification of the reaction product. In addition, since the process directly adds an oxidant to the homogeneous system, the oxidant after the reaction and the excess oxidant will co-exist in the system, which makes it difficult to recover the cellulose solvent such as an ionic liquid used to dissolve the cellulose components in the system, increasing the production cost and being not conducive to large-scale production. Therefore, a preparation process with simple design process and environmental friendliness is required.

[0003] The prior art with application publication number CN 117924761 A discloses a method for preparing cellulose film by extracting cellulose from xylose residue, which comprises mixing xylose residue with an ionic liquid-cosolvent system, vacuum degassing the obtained cellulose solution through centrifugation, and preparing regenerated cellulose film by a casting method.

[0004] However, the above process for preparing regenerated cellulose membrane has the following problems: first, a large amount of organic solvent is used to dissolve cellulose, which leads to strong equipment corrosion, great environmental risks and high production costs, which is not conducive to large-scale production; second, only a single cellulose is used as raw material, and the mechanical properties of the prepared membrane are poor. Summary of the invention

[0005] The present application discloses a method for extracting aldehyde cellulose from tongcao residue to prepare a composite membrane, aiming to solve the technical problems of the existing preparation of fiber membranes, such as high production cost, great environmental risk, great safety risk and poor mechanical properties.

[0006] In order to achieve the above purpose, the technical solution of this application is:

[0007] The first aspect of the present application provides a method for extracting aldehyde cellulose from tongcao residue to prepare a composite film, the method comprising:

[0008] Dispersing the tongcao residue powder in a 0.5%-3% alkaline solution, reacting at 60-100°C for 0.5-3h, and obtaining pre-treated residue after separation;

[0009] After adding the pretreated slag to the ionic liquid, heating at 50-120° C. for 0.5-3 h, adding 10-60 parts of deionized water to obtain a suspension;

[0010] The suspension is filtered, the intercepted liquid is collected, an oxidant is added to react in the dark, and then separated and collected to obtain dialdehyde cellulose;

[0011] The dialdehyde cellulose is added to gelatin for compounding and then a film is prepared to obtain a composite film.

[0012] In combination with the first aspect, preferably, the alkaline solution is an aqueous solution of sodium hydroxide or potassium hydroxide.

[0013] In combination with the first aspect, preferably, the ionic liquid is one of 1-butyl-3-methylimidazolium chloride, 1-hydroxyethyl-3-methylimidazolium chloride, 1-allyl-3-methylimidazolium chloride, 1-allyl-3-methylimidazolium bromide, 1-ethyl-3-methylimidazolium acetate, and 1-ethyl-3-methylimidazolium chloride.

[0014] In combination with the first aspect, preferably, the added amount of the ionic liquid is 10-60 parts by mass.

[0015] In combination with the first aspect, preferably, the suspension is placed in a deionized water system for filtration, and the molecular weight cutoff of the filtration membrane is 300-5000Da.

[0016] In combination with the first aspect, preferably, when the suspension is subjected to dialysis filtration, the filtrate is concentrated under reduced pressure and then vacuum dried to recover the ionic liquid.

[0017] In combination with the first aspect, preferably, the oxidant is one of sodium periodate and potassium periodate.

[0018] In combination with the first aspect, preferably, the added amount of the oxidant is 0.5-2 parts by mass.

[0019] In combination with the first aspect, preferably, when the oxidant is added to carry out the light-protected reaction, the reaction temperature is 30-60° C. and the reaction time is 0.5-8 h.

[0020] In combination with the first aspect, preferably, the mass ratio of the dialdehyde cellulose to gelatin is 0.5-2:100.

[0021] Compared with the prior art, the advantages or beneficial effects of the embodiments of the present application include at least:

[0022] The method for extracting aldehyde cellulose from tongcao residue to prepare a composite membrane provided by the present application uses tongcao residue as raw material, and obtains dialdehyde cellulose through low-concentration alkali treatment + ionic liquid extraction + oxidant treatment, and after mixing and cross-linking with gelatin, a composite membrane is obtained. First, low-concentration alkali treatment is used to remove the secondary metabolites in the tongcao residue, and the lignin and hemicellulose components in the raw material can also be removed; secondly, ionic liquid is used for dissolution and extraction to obtain a highly dispersed cellulose suspension, the ionic liquid in the suspension is collected and recovered, and then an oxidant is added to the intercepted suspension for oxidation reaction to prepare dialdehyde cellulose with an aldehyde content of 32-73%; finally, the chemical bonds formed by the reaction of the aldehyde groups in the dialdehyde cellulose with the amino groups in the gelatin are cross-linked into a film, which greatly improves the mechanical properties of the composite membrane. At the same time, the tongcao residue used in the present application is used as a raw material for the preparation of the composite membrane, which realizes the reuse of Chinese medicine residue waste, and has low cost, thus having significant raw material advantages; and it can realize the recycling of ionic liquids, reduce industrial production costs, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments recorded in the present application, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0024] Figure 1 A process flow chart for preparing the A1-composite membrane according to the embodiment of the present application;

[0025] Figure 2 The infrared image of A3-dialdehyde cellulose prepared in the example of this application;

[0026] Figure 3 Mechanical properties diagrams of A1-composite membrane, A2-composite membrane, A3-composite membrane and B1-composite membrane prepared for the examples of the present application. DETAILED DESCRIPTION

[0027] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0028] In the following description of this embodiment, the term "and / or" is used to describe the association relationship of associated objects, indicating that there may be three relationships. For example, A and / or B can represent: A exists alone, B exists alone, and A and B exist at the same time. A and B can be singular or plural. The character " / " generally indicates that the associated objects before and after are in an "or" relationship.

[0029] In the following description of this embodiment, the term "at least one" refers to one or more, and "plurality" refers to two or more. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single items or plural items. For example, "at least one of a, b or c", or "at least one of a, b and c", can all represent: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, c can be single or multiple, respectively.

[0030] Those skilled in the art should understand that in the following description of the embodiments of the present application, the order of serial numbers does not mean the order of execution, some or all of the steps can be executed in parallel or sequentially, and the execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0031] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms "a", "an" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0032] It should be noted that all raw materials and reagents in the examples of the present application were purchased on the market or prepared according to conventional methods well known to those skilled in the art.

[0033] In a first aspect, the present invention provides a method for extracting aldehyde cellulose from tongcao residue to prepare a composite film, the method comprising:

[0034] Dispersing the tongcao residue powder in a 0.5%-3% alkaline solution, reacting at 60-100°C for 0.5-3h, and obtaining pre-treated residue after separation;

[0035] After adding the pretreated slag to the ionic liquid, heating at 50-120° C. for 0.5-3 h, adding 10-60 parts of deionized water to obtain a suspension;

[0036] The suspension is filtered, the intercepted liquid is collected, an oxidant is added to react in the dark, and then separated and collected to obtain dialdehyde cellulose;

[0037] The dialdehyde cellulose is added to gelatin for compounding and then a film is prepared to obtain a composite film.

[0038] Among them, firstly, low-concentration alkali treatment can remove the secondary metabolites in the stalks of the Chinese angelica root, and can also remove the lignin and hemicellulose components in the raw materials; secondly, ionic liquid is used for dissolution and extraction to obtain a highly dispersed cellulose suspension, the ionic liquid in the suspension is collected and recovered, and then an oxidant is added to the intercepted suspension for oxidation reaction to prepare a dialdehyde cellulose with an aldehyde content of 32-73%; finally, the chemical bonds formed by the reaction of the aldehyde groups in the dialdehyde cellulose with the amino groups in the gelatin are cross-linked to form a film, which greatly improves the mechanical properties of the composite film. At the same time, the stalks of the Chinese angelica root used in this application is used as a raw material for the preparation of the composite film, which realizes the reuse of Chinese medicine residue waste, is low in cost, and thus has a significant raw material advantage; and it can realize the recycling of ionic liquids, reduces industrial production costs, and has broad application prospects.

[0039] It should be noted that the present application uses the residue of the tongcao as raw material to extract dialdehyde cellulose, thereby realizing the recycling of waste Chinese medicine residues. In addition, since a large amount of secondary metabolites in the tongcao have been extracted from the original medicine during the water decoction process, the current problem of effective conversion and utilization of solid residues in the production process of tongcao has been solved, providing a new way for the value-added utilization of waste biomass residues and creating greater market value.

[0040] It should be noted that the present application first uses a low concentration of alkaline solution for hydrolysis, so as to fully remove the secondary metabolites in the slag of the Chinese angelica root, and can remove the lignin and hemicellulose components in the raw material, which is beneficial to improve the purity of the product. Further, an ionic liquid is used as an extraction solvent, and the cellulose components it is rich in are dissolved and extracted. After diluting the extract, a highly dispersed cellulose suspension is obtained, and the ionic liquid in the suspension is recovered by membrane separation technology, so as to realize the recycling of the ionic liquid, and then an oxidant is added to cellulose for oxidation reaction to obtain dialdehyde cellulose. By preparing the reaction stock solution into a highly dispersed heterogeneous system, it is easier to separate the product while beneficially accelerating the reaction process, which is convenient for industrial promotion and application. Finally, after the prepared dialdehyde cellulose is reacted with gelatin, both have a high reactivity, giving excellent mechanical properties to the composite film.

[0041] In the embodiment of the present application, the alkaline solution is preferably an aqueous solution of sodium hydroxide or potassium hydroxide. Among them, a low-concentration alkaline solution is first used for hydrolysis, so as to fully remove the secondary metabolites in the tongcao herb residue, and at the same time, the lignin and hemicellulose components in the raw material can be removed, and no organic solvent is added, which is convenient for subsequent separation steps, reduces environmental pollution, improves the safety of the reaction in the production process, improves the quality of the extracted fiber, reduces production costs, and facilitates the separation and purification of the product.

[0042] In the embodiment of the present application, the ionic liquid is preferably one of 1-butyl-3-methylimidazolium chloride, 1-hydroxyethyl-3-methylimidazolium chloride, 1-allyl-3-methylimidazolium chloride, 1-allyl-3-methylimidazolium bromide, 1-ethyl-3-methylimidazolium acetate, and 1-ethyl-3-methylimidazolium chloride, and the addition amount is preferably 10-60 parts by weight. Among them, by controlling the addition amount of these ionic liquids, the cellulose dissolving ability is strong, it is easy to recycle, and it will not volatilize, so that cellulose can be effectively extracted from the herb residue of Tongcao, and it will not cause excessive waste of resources.

[0043] In the embodiment of the present application, the suspension is placed in a deionized water system for filtration, and the molecular weight cutoff of the filtration membrane is 300-5000Da. Among them, the present application uses a dialysis bag to filter the suspension, and by controlling the molecular weight cutoff during dialysis, the ionic liquid and cellulose in the suspension can be effectively separated to ensure the filtration effect and efficiency.

[0044] In the embodiment of the present application, the oxidant is preferably one of sodium periodate and potassium periodate, and the added amount is preferably 0.5-2 parts by mass. Among them, by controlling the amount of the added oxidant, the aldehyde content in the generated cellulose can be effectively controlled. Only when the aldehyde content is controlled within a certain range, the cross-linking effect of the composite film made with gelatin is enhanced with the increase of the aldehyde content in the dialdehyde cellulose. However, when the cross-linking effect between molecules tends to be saturated, no matter how many aldehyde groups are added, the cross-linking effect cannot be further improved. Instead, beneficial cross-linking may no longer be produced, thereby affecting the mechanical properties of the composite film.

[0045] In the embodiment of the present application, the mass ratio of dialdehyde cellulose to gelatin is preferably 0.5-2: 100. Among them, by controlling the mass ratio of dialdehyde cellulose to gelatin, the active aldehyde groups in dialdehyde cellulose can be combined with the amino groups of gelatin molecules after being added to the gelatin material to form a more stable chemical bond, thereby significantly improving the mechanical properties of the gelatin composite film material added with dialdehyde cellulose, and this cross-linking reaction can significantly improve the stability of the composite film.

[0046] The technical solution of the present application will be further described below in conjunction with specific embodiments.

[0047] Example 1

[0048] This embodiment provides a method for preparing an A1-composite membrane, according to Figure 1 The preparation process shown specifically includes:

[0049] S101: Take 1 part of the raw powder of the tongcao residue, add 10 parts of a sodium hydroxide solution with a mass concentration of 1%, reflux extract at 70° C. for 1 hour, filter and wash with water to obtain a pre-treated residue;

[0050] S102: the pretreated slag is transferred to a reaction kettle, 30 parts of 1-butyl-3-methylimidazolium chloride is added, and after heating at 80° C. for 1 hour, 30 parts of deionized water is added and stirred for dilution, so that flocculent insoluble matter is generated in the solution to obtain a suspension;

[0051] S103: using a dialysis membrane with a molecular weight of 1000Da, dialyzing the suspension, adding 0.5 parts of sodium periodate to the intercepted liquid, reacting at 40°C in the dark for 2 hours to obtain a reaction suspension, cooling the reaction suspension, centrifuging it, washing it with deionized water, and drying it to obtain A1-dialdehyde cellulose;

[0052] S104: Take 0.1 g of A1-dialdehyde cellulose and disperse it in 100 mL of deionized water. Stir and swell it at 60°C for 2 hours. Add 10 g of gelatin and continue stirring for 1 hour to obtain a mixed solution. Take 10 mL of the mixed solution and spread it evenly in a round culture dish with a diameter of 9 cm. Let it stand at room temperature for 48 hours and then peel it off to obtain an A1-composite film (A1-dialdehyde cellulose-gelatin composite film).

[0053] Example 2

[0054] This embodiment provides a method for preparing an A2-composite membrane, which specifically includes:

[0055] S201: Take 1 part of the raw powder of the tongcao residue, add 10 parts of a potassium hydroxide solution with a mass concentration of 1%, reflux extract at 70° C. for 1.5 hours, filter and wash with water to obtain a pre-treated residue;

[0056] S202: the pretreated slag is transferred to a reaction kettle, 40 parts of 1-hydroxyethyl-3-methylimidazolium chloride is added, and after heating at 90° C. for 2 hours, 40 parts of deionized water is added and stirred for dilution, so that flocculent insoluble matter is generated in the solution to obtain a suspension;

[0057] S203: dialyzing the suspension using a dialysis membrane with a molecular weight of 2000Da, adding 1 portion of potassium periodate to the intercepted liquid, reacting at 50°C in the dark for 3 hours to obtain a reaction suspension, cooling the reaction suspension, centrifuging it, washing it with deionized water, and drying it to obtain A2-dialdehyde cellulose;

[0058] S204: Take 0.2g of A2-dialdehyde cellulose and disperse it in 100mL of deionized water, stir and swell it at 60°C for 2h, add 10g of gelatin and continue stirring for 1h to obtain a mixed solution, take 10mL of the mixed solution, spread it evenly in a round culture dish with a diameter of 9cm, let it stand at room temperature for 48h, then peel it off to obtain an A2-composite film (A2-dialdehyde cellulose-gelatin composite film).

[0059] Example 3

[0060] This embodiment provides a method for preparing an A3-composite membrane, which specifically includes:

[0061] S301: taking 1 part of the raw powder of the tongcao residue, adding 30 parts of a sodium hydroxide solution with a mass concentration of 2%, reflux extraction at 90° C. for 2 hours, filtering and washing with water to obtain a pre-treated residue;

[0062] S302: the pretreated slag is transferred to a reactor, 50 parts of 1-allyl-3-methylimidazolium chloride is added, and after heating at 100° C. for 2.5 hours, 50 parts of deionized water is added and stirred for dilution, so that flocculent insoluble matter is generated in the solution to obtain a suspension;

[0063] S303: using a dialysis membrane with a molecular weight of 3000Da to dialyze the suspension, adding 2 parts of potassium periodate to the intercepted liquid, reacting at 50°C in the dark for 4 hours to obtain a reaction suspension, cooling the reaction suspension, centrifuging it, washing it with deionized water, and drying it to obtain A3-dialdehyde cellulose;

[0064] S304: Take 0.2g of A3-dialdehyde cellulose and disperse it in 100mL of deionized water, stir and swell it at 60°C for 2h, add 10g of gelatin and continue stirring for 1h to obtain a mixed solution, take 10mL of the mixed solution, spread it evenly in a round culture dish with a diameter of 9cm, let it stand at room temperature for 48h and then peel it off to obtain an A3-composite film (A3-dialdehyde cellulose-gelatin composite film).

[0065] At the same time, in order to verify the comprehensive performance of the composite membrane prepared in the above examples, the present application provides the following comparative examples for detailed description.

[0066] Comparative Example 1

[0067] The component ratio, preparation operation and process parameters of the B1-composite membrane prepared in the comparative example of the present application are basically the same as those in Example 3, except that the cellulose added in this example is not oxidized, that is, the extracted pure cellulose is compounded with gelatin to prepare the B1-composite membrane.

[0068] Comparative Example 2

[0069] The component ratio, preparation operation and process parameters of the B2-composite membrane prepared in the comparative example of the present application are basically the same as those in Example 3, except that in this example, 3 parts of potassium periodate are added to the intercepted liquid to prepare B2-dialdehyde cellulose, and a B2-composite membrane is prepared with gelatin.

[0070] Comparative Example 3

[0071] The component ratio, preparation operation and process parameters of the B3-composite membrane prepared in the comparative example of the present application are basically the same as those in Example 3, except that in this embodiment, 0.1 parts of potassium periodate are added to the intercepted liquid to prepare B3-dialdehyde cellulose, and a B3-composite membrane is prepared with gelatin.

[0072] The difference between Comparative Example 2 of the present application and Example 3 is that the amount of oxidant added is greater, and the aldehyde content of the obtained dialdehyde cellulose increases, but too much aldehyde content cannot enhance the mechanical properties of the composite film. The difference between Comparative Example 3 of the present application and Example 3 is that the amount of oxidant added is too small, and the aldehyde content of the obtained dialdehyde cellulose decreases, and it cannot form a stable fiber film with gelatin, resulting in a significant decrease in the mechanical properties of the composite film.

[0073] The yield and aldehyde content of dialdehyde cellulose extracted from the embodiment and the comparative example were tested, and the yield of dialdehyde cellulose was calculated as the percentage of grams of dialdehyde cellulose extracted from each gram of raw material. The aldehyde content of dialdehyde cellulose was determined by the alkali consumption method: 0.1 g of the product was taken, 10 mL of deionized water was added to swell, and then 10 mL of 0.1 mol / L sodium hydroxide solution was added, heated in a water bath at 60°C for 5 min, and after cooling, 10 mL of 0.1 mol / L hydrochloric acid solution was added, and then 3-5 drops of phenolphthalein indicator were added, and 0.1 mol / L sodium hydroxide solution was used to titrate to the end point. The aldehyde content was calculated by the following formula:

[0074]

[0075] Wherein: C0 and C1 are the concentrations of sodium hydroxide and hydrochloric acid solutions, mol / L; V0 and V1 are the volumes of sodium hydroxide and hydrochloric acid solutions consumed, mL; m is the mass of dialdehyde cellulose weighed, g; 162 is the average molecular mass of dialdehyde cellulose repeating units. The results are shown in Table 1.

[0076] Table 1 Yield and aldehyde content of dialdehyde cellulose

[0077]

[0078]

[0079] According to Table 1, the aldehyde content in the generated aldehyde cellulose can be effectively controlled by controlling the amount of the added oxidant. As the amount of the added oxidant gradually increases, the aldehyde content also gradually increases accordingly.

[0080] In order to verify the structure of the dialdehyde cellulose prepared in the examples of the present application, the A3-dialdehyde cellulose prepared in the examples was characterized, and the results were as follows: Figure 2 As shown; among them, Figure 2 This is the infrared image of A3-dialdehyde cellulose.

[0081] according to Figure 2 As is known, the A3-dialdehyde cellulose prepared in the embodiment was analyzed by Fourier transform infrared spectroscopy (FT-IR) at 4000-500 cm -1 The spectrum was scanned within the range for determination. -1 The strong absorption peak at 2923 cm is the stretching vibration peak of cellulose hydroxyl group. -1 The absorption peak at 1728 cm is caused by the carbon-hydrogen stretching vibration of the methylene group. -1 The absorption peak at 1639cm is the carbonyl absorption peak, which is the characteristic peak of aldehyde cellulose. -1 The strong absorption peak is caused by the intramolecular hydrogen bonds in the cellulose structure. -1 The absorption peak at 891 cm is caused by the vibration of the COC skeleton of the cellulose pyranose ring. -1 The absorption peak at represents the vibration of the β-glycosidic bond of cellulose and is the characteristic absorption peak of cellulose substances.

[0082] In order to verify the comprehensive performance of the composite membranes prepared in the examples of the present application, the mechanical properties of the A1-composite membrane, A2-composite membrane, A3-composite membrane and B1-composite membrane prepared in the examples were characterized, and the mechanical properties of the composite membrane materials were measured using a universal electronic tensile machine. The results are as follows: Figure 3 shown.

[0083] according to Figure 3 As shown in Table 2, the mechanical properties of the blank gelatin film material without dialdehyde cellulose are poor, with a maximum tensile displacement of 18.6 mm and a maximum tensile force of 20.7 N. The mechanical properties of the gelatin film material after adding dialdehyde cellulose are significantly improved, with the maximum tensile displacement of 23.8 mm and a maximum tensile force of 40.9 N for the A1-composite film; the maximum tensile displacement of 33.2 mm and a maximum tensile force of 89.2 N for the A2-composite film; and the maximum tensile displacement of 32.3 mm and a maximum tensile force of 82.1 N for the A3-composite film. The test results are shown in Table 2.

[0084] Table 2 Yield and aldehyde content of the composite membrane

[0085]

[0086] According to Table 2, by controlling the amount of oxidant added, the aldehyde content in dialdehyde cellulose can be effectively controlled, and then combined with the amino group of gelatin to form a more stable chemical bond, so that the mechanical properties of the composite film with dialdehyde cellulose added are significantly improved. When the added mass part of the oxidant is 1, the prepared dialdehyde cellulose and gelatin produce more effective cross-linking, and the mechanical properties of the composite film are optimal, so that it has a wider range of uses and higher performance in practical applications. In the process of preparing the composite film, the amount of dialdehyde cellulose added also has a certain effect on the performance of the film. Compared with Example 1, although the aldehyde content of dialdehyde cellulose prepared in Comparative Example 3 is significantly different, since Comparative Example 3 adds more parts of dialdehyde cellulose in the film making process, it achieves mechanical properties similar to those of the film material prepared in Example 1.

[0087] Therefore, the method for extracting aldehyde-based cellulose from tongcao residue to prepare a composite membrane provided by the present application uses tongcao residue as raw material, and obtains dialdehyde cellulose through low-concentration alkali treatment + ionic liquid extraction + oxidant treatment, and obtains a composite membrane after cross-linking with gelatin. The mechanical properties of the composite membrane can be greatly improved through the preparation process of the present application. At the same time, the tongcao residue used in the present application is used as a raw material for the preparation of the composite membrane, which realizes the reuse of Chinese medicine residue waste, and the development and application cost is low, thus having significant raw material advantages; and it can realize the recycling of ionic liquids, reducing industrial production costs, and has broad application prospects.

[0088] The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referenced to each other, and each embodiment focuses on the differences from other embodiments.

[0089] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit the present application. Although the present application has been described in detail with reference to the aforementioned embodiments, a person of ordinary skill in the art should understand that the technical solutions recorded in the aforementioned embodiments may still be modified, or some or all of the technical features therein may be replaced by equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the present application.

Claims

1. A method for extracting aldehyde cellulose from tongcao residue to prepare a composite film, characterized in that: The method comprises: Dispersing the tongcao residue powder in a 0.5%-3% alkaline solution, reacting at 60-100°C for 0.5-3h, and obtaining pre-treated residue after separation; After adding the pretreated slag to the ionic liquid, heating at 50-120° C. for 0.5-3 h, adding 10-60 parts of deionized water to obtain a suspension; The suspension is filtered, the intercepted liquid is collected, an oxidant is added to react in the dark, and then separated and collected to obtain dialdehyde cellulose; The dialdehyde cellulose is added to gelatin for compounding and then a film is prepared to obtain a composite film.

2. The method for extracting aldehyde cellulose from tongcao residue to prepare a composite film according to claim 1, characterized in that: The alkaline solution is an aqueous solution of sodium hydroxide or potassium hydroxide.

3. The method for extracting aldehyde cellulose from tongcao residue to prepare a composite film according to claim 1, characterized in that: The ionic liquid is one of 1-butyl-3-methylimidazolium chloride, 1-hydroxyethyl-3-methylimidazolium chloride, 1-allyl-3-methylimidazolium chloride, 1-allyl-3-methylimidazolium bromide, 1-ethyl-3-methylimidazolium acetate and 1-ethyl-3-methylimidazolium chloride.

4. The method for extracting aldehyde cellulose from tongcao residue to prepare a composite film according to claim 1, characterized in that: The added amount of the ionic liquid is 10-60 parts by mass.

5. The method for extracting aldehyde cellulose from tongcao residue to prepare a composite film according to claim 1, characterized in that: The suspension is placed in a deionized water system for filtration, and the molecular weight cutoff of the filtration membrane is 300-5000Da.

6. The method for extracting aldehyde cellulose from tongcao residue to prepare a composite film according to claim 1, characterized in that: When the suspension is filtered, the filtrate is concentrated under reduced pressure and then vacuum dried to recover the ionic liquid.

7. The method for extracting aldehyde cellulose from tongcao residue to prepare a composite film according to claim 1, characterized in that: The oxidant is one of sodium periodate and potassium periodate.

8. The method for extracting aldehyde cellulose from tongcao residue to prepare a composite film according to claim 1, characterized in that: The added amount of the oxidant is 0.5-2 parts by mass.

9. The method for extracting aldehyde cellulose from tongcao residue to prepare a composite film according to claim 1, characterized in that: When the oxidant is added to carry out the light-protected reaction, the reaction temperature is 30-60° C. and the reaction time is 0.5-8 h.

10. The method for preparing a composite film by extracting aldehyde cellulose from tongcao residue according to claim 1, characterized in that: The mass ratio of the dialdehyde cellulose to the gelatin is 0.5-2:100.

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