Bio-based foam as well as preparation method and application thereof

Abstract

The invention provides bio-based foam and a preparation method and application thereof.The preparation method comprises the steps that after waste lignocellulose is subjected to acidolysis pretreatment and enzymolysis saccharification, the pH is adjusted to be 5-6; the preparation method comprises the following steps: reacting nano titanium dioxide with chitosan under an alkaline condition to generate a composite additive; uniformly mixing the bio-based solution, the composite additive, the foaming agent and the bio-based plasticizer; carrying out foaming molding at 150 to 180 DEG C; and dipping in a silane coupling agent ethanol solution in vacuum, and drying to obtain the bio-based foam. The bio-based foam has an antibacterial property, the antibacterial rate on escherichia coli and staphylococcus aureus is more than 90%, and organic pollutants can be photocatalytically degraded. The material is applied to indoor air purification and can adsorb and degrade formaldehyde, benzene and other harmful gases; and the quality guarantee period is prolonged by utilizing the antibacterial property.

Description

Technical Field

[0001] The present invention relates to the technical field of bio-based materials, and more specifically, to a bio-based foam and a preparation method and application thereof. Background Art

[0002] Among the existing bio-based material technologies, waste lignocellulose, as a renewable resource, has always attracted attention for its high-value utilization. Traditional bio-based foam preparation methods often rely on chemically synthesized additives, which may burden the environment and do not have functional properties such as antibacterial or photocatalytic properties. In addition, the application of these materials in indoor air purification and food packaging is limited because they lack the ability to effectively degrade harmful gases and inhibit the growth of microorganisms.

[0003] In the process of implementing the embodiments of the present invention, the inventors found that there are at least the following problems or defects in the prior art: traditional bio-based foams do not have good antibacterial properties and the ability to photocatalytically degrade organic pollutants, which limits their application in indoor air purification and food packaging. At the same time, the foams prepared by the existing methods also have deficiencies in physical and chemical stability, which affects their performance and safety in long-term use. Summary of the invention

[0004] The invention provides a bio-based foam and a preparation method and application thereof.

[0005] In a first aspect of the present invention, a method for preparing a bio-based foam is provided, comprising the following steps:

[0006] S1: Preparation of bio-based raw materials: After pre-treatment of waste lignocellulose by acid hydrolysis, enzymatic saccharification is performed to obtain a bio-based solution rich in sugars, and the pH thereof is adjusted to 5-6 for standby use;

[0007] S2: Preparation of functional additives: react nano-titanium dioxide with chitosan under alkaline conditions to generate a composite additive with antibacterial and photocatalytic properties, the reaction temperature is controlled at 60-80°C, and the reaction time is 2-3 hours;

[0008] S3: Construction of mixed foaming system: Add the composite additive prepared in step S2, the foaming agent azodicarbonamide and the bio-based plasticizer tributyl citrate to the bio-based solution obtained in step S1, and stir to mix evenly at a stirring speed of 300-500 r / min for 15-25 minutes;

[0009] S4: Foaming molding: pour the above mixed solution into a mold, put it into an oven preheated to 150-180°C, and keep it at this temperature for 1-2 hours for foaming molding to form a bio-based foam blank;

[0010] S5: Post-treatment strengthening: The bio-based foam blank is taken out, immersed in an ethanol solution containing a silane coupling agent under a vacuum environment for 1-2 hours, and then dried at 80-100° C. for 3-5 hours to obtain the final bio-based foam.

[0011] Furthermore, in the step S1, the acid used in the acid hydrolysis pretreatment is a sulfuric acid solution with a mass fraction of 10%-15%, the acid hydrolysis temperature is 120-130° C., and the time is 1-2 hours.

[0012] Furthermore, in step S2, the mass ratio of nano-titanium dioxide to chitosan is 1:2-3, and the alkaline condition is adjusted by a sodium hydroxide solution with a mass fraction of 5%-8%.

[0013] Furthermore, in step S3, the mass ratio of the bio-based solution, the composite additive, the foaming agent azodicarbonamide and the bio-based plasticizer tributyl citrate is 100:5-10:3-6:8-12.

[0014] Furthermore, in step S4, the pressure in the oven is maintained at 0.5-1 MPa.

[0015] Furthermore, in step S5, the mass fraction of the silane coupling agent in the ethanol solution is 3%-5%.

[0016] Furthermore, the enzyme used in the enzymatic saccharification process is a composite enzyme of cellulase and saccharifying enzyme, the mass ratio of the two is 1:1-2, and the amount of enzyme added is 3%-5% of the mass of the bio-based raw material.

[0017] Furthermore, after the reaction is completed, the composite additive is obtained by centrifugal separation, with a centrifugal speed of 5000-8000 r / min and a time of 10-15 minutes.

[0018] In the second aspect of the present invention, a bio-based foam is provided. The bio-based foam is prepared according to any one of the preparation methods described. The foam has good antibacterial properties, with an inhibition rate of more than 90% against Escherichia coli and Staphylococcus aureus, and has the ability to photocatalytically degrade organic pollutants.

[0019] In the third aspect of the present invention, an application of a bio-based foam is provided, which is applied in the field of indoor air purification and can adsorb and photocatalytically degrade harmful gases such as formaldehyde and benzene in the air; it can also be applied in the field of food packaging and use its antibacterial properties to extend the shelf life of food.

[0020] According to the above embodiments of the present invention, at least the following beneficial effects are achieved: the bio-based foam preparation method provided by the present invention can effectively utilize waste wood cellulose, and prepare bio-based foam with good antibacterial properties and photocatalytic degradation of organic pollutants through a series of environmentally friendly steps. This foam can not only reduce the burden on the environment, but also efficiently adsorb and degrade harmful gases such as formaldehyde and benzene in the field of indoor air purification, significantly improving indoor air quality. At the same time, in the field of food packaging, the antibacterial properties of the bio-based foam help to extend the shelf life of food, reduce food corruption and waste, and ensure food safety.

[0021] In addition, the raw materials and additives used in the preparation process of the bio-based foam of the present invention are all derived from bio-based materials, making the entire production process more environmentally friendly and sustainable. Through optimized preparation conditions and formulas, the obtained foam product has good physical and chemical stability and can meet long-term use requirements. The preparation and application of this bio-based foam can not only improve the utilization efficiency of waste biomass resources, but also provide new solutions for environmental protection and sustainable development. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The above and other objects, features and advantages of the exemplary embodiments of the present invention will become readily understood by reading the detailed description below with reference to the accompanying drawings. In the accompanying drawings, several embodiments of the present invention are shown in an exemplary and non-limiting manner, in which:

[0023] Figure 1 A schematic flow chart of a method for preparing bio-based foam provided in one embodiment of the present invention. DETAILED DESCRIPTION

[0024] The following specifically describes the preferred embodiments of the present invention regarding a bio-based foam and a preparation method and application thereof in combination with related contents. This part of the content is used to explain the principles of the present invention, and is not used to limit the scope of the present invention.

[0025] The present invention provides a method for preparing a bio-based foam, comprising the following steps:

[0026] S1: Preparation of bio-based raw materials: After pre-treatment of waste lignocellulose by acid hydrolysis, enzymatic saccharification is performed to obtain a bio-based solution rich in sugars, and the pH value is adjusted to 5-6 for use.

[0027] S2: Preparation of functional additives: Nano-titanium dioxide and chitosan are reacted under alkaline conditions to generate a composite additive with antibacterial and photocatalytic properties. The reaction temperature is controlled at 60-80°C and the reaction time is 2-3 hours.

[0028] S3: Construction of mixed foaming system: Add the composite additive prepared in step S2, the foaming agent azodicarbonamide and the bio-based plasticizer tributyl citrate to the bio-based solution obtained in step S1, and stir to mix evenly at a stirring speed of 300-500 r / min for 15-25 minutes.

[0029] S4: Foaming molding: Pour the above mixed liquid into a mold, put it into an oven preheated to 150-180°C, and keep it at this temperature for 1-2 hours for foaming molding to form a bio-based foam blank.

[0030] S5: Post-treatment strengthening: The bio-based foam blank is taken out, immersed in an ethanol solution containing a silane coupling agent under a vacuum environment for 1-2 hours, and then dried at 80-100° C. for 3-5 hours to obtain the final bio-based foam.

[0031] Specifically, in step S1, the waste lignocellulose is pretreated by acid hydrolysis, and then enzymatically saccharified to obtain a bio-based solution rich in sugars, and its pH is adjusted to 5-6 for standby use. Among them, the acid used for acid hydrolysis pretreatment is a sulfuric acid solution with a mass fraction of 10%-15%, the acid hydrolysis temperature is 120-130°C, and the time is 1-2 hours. The use of this concentration of sulfuric acid solution and a specific temperature and time for acid hydrolysis can effectively break the complex structure of lignocellulose and provide favorable conditions for subsequent enzymatic saccharification. The enzyme used in the enzymatic saccharification process is a composite enzyme of cellulase and saccharifying enzyme, the mass ratio of the two is 1:1-2, and the amount of enzyme added is 3%-5% of the mass of the bio-based raw material. Such a composite enzyme ratio and addition amount can efficiently convert the acid-hydrolyzed lignocellulose into a bio-based solution rich in sugars, providing a basic raw material for the preparation of bio-based foam.

[0032] Specifically, in step S2, nano-titanium dioxide and chitosan are reacted under alkaline conditions to generate a composite additive with antibacterial and photocatalytic properties. The mass ratio of nano-titanium dioxide to chitosan is 1:2-3, and the alkaline conditions are adjusted by a sodium hydroxide solution with a mass fraction of 5%-8%. The reaction temperature is controlled at 60-80°C, and the reaction time is 2-3 hours. Under these conditions, nano-titanium dioxide and chitosan can fully react, and the generated composite additive has both the photocatalytic properties of nano-titanium dioxide and the antibacterial properties of chitosan, giving unique functions to bio-based foams. After the reaction is completed, the composite additive is obtained by centrifugation, with a centrifugal speed of 5000-8000r / min and a time of 10-15 minutes to ensure the purity and performance of the composite additive.

[0033] Specifically, in step S3, the composite additive prepared in step S2, the foaming agent azodicarbonamide and the bio-based plasticizer tributyl citrate are added to the bio-based solution obtained in step S1, and stirred and mixed evenly. The mass ratio of the bio-based solution, the composite additive, the foaming agent azodicarbonamide and the bio-based plasticizer tributyl citrate is 100:5-10:3-6:8-12. The appropriate ratio ensures the stability of the mixed system and the subsequent foaming and performance. The stirring speed is 300-500r / min, and the time is 15-25 minutes, so that the components are fully mixed and ready for foaming molding.

[0034] Specifically, in step S4, the mixed solution is poured into a mold, placed in an oven preheated to 150-180°C, and maintained at this temperature for 1-2 hours for foaming and forming to form a bio-based foam blank. The pressure in the oven is maintained at 0.5-1MPa. This temperature and pressure condition is conducive to the decomposition of the foaming agent to produce gas, which promotes the foam to form a uniform pore structure, thereby obtaining a foam blank with a certain shape and performance.

[0035] Specifically, in step S5, the bio-based foam blank is taken out, immersed in an ethanol solution containing a silane coupling agent under a vacuum environment for 1-2 hours, and then dried at 80-100° C. for 3-5 hours to obtain the final bio-based foam. The mass fraction of the silane coupling agent in the ethanol solution is 3%-5%. The vacuum impregnation process helps the silane coupling agent to better penetrate into the foam, enhance the connectivity of the internal structure of the foam, and after drying, further enhance the performance of the foam, so that it has better physical and chemical stability.

[0036] The bio-based foam prepared by the above preparation method has good antibacterial properties, with an antibacterial rate of more than 90% against Escherichia coli and Staphylococcus aureus, and has the ability to photocatalytically degrade organic pollutants. This is due to the composite additive prepared in step S2, which gives the foam unique functions and makes it have application potential in multiple fields.

[0037] The present invention also provides an application of bio-based foam, which is applied to the field of indoor air purification and can adsorb and photocatalytically degrade harmful gases such as formaldehyde and benzene in the air. Since the foam has photocatalytic properties, it can decompose harmful gases in the air into harmless substances under light conditions, thereby achieving the purpose of purifying the air. At the same time, the bio-based foam can also be applied to the field of food packaging, using its antibacterial properties to extend the shelf life of food, reduce the risk of food deterioration due to microbial contamination, and ensure food safety.

[0038] Example 1

[0039] The bio-based foam of this embodiment is composed of: 100 parts of treated waste lignocellulose-derived bio-based solution, 5 parts of composite additives, 3 parts of azodicarbonamide as a foaming agent, and 8 parts of tributyl citrate as a bio-based plasticizer. It is prepared by the following steps:

[0040] S1: Preparation of bio-based raw materials: Acid hydrolyze the waste lignocellulose with a 10% by mass sulfuric acid solution at 120°C for 1 hour, then add a 1:1 mass ratio of cellulase and saccharifying enzyme complex (the enzyme addition amount is 3% of the raw material mass) for enzymatic saccharification to obtain a bio-based solution, adjust the pH to 5, and set aside.

[0041] S2: Preparation of functional additives: Nano-titanium dioxide and chitosan were mixed in a mass ratio of 1:2, and an alkaline environment was adjusted with a 5% by mass sodium hydroxide solution. The mixture was reacted at 60°C for 2 hours to generate a composite additive. After the reaction, the mixture was obtained by centrifugation at 5000 r / min for 10 minutes.

[0042] S3: Construction of mixed foaming system: Add the above-mentioned bio-based solution, composite additives, foaming agent azodicarbonamide, and bio-based plasticizer tributyl citrate into a container in proportion, and stir at 300r / min for 15 minutes to mix evenly.

[0043] S4: Foaming molding: Pour the mixed liquid into a mold, put it into an oven preheated to 150°C, and keep it at a pressure of 0.5MPa for 1 hour for foaming molding to form a bio-based foam blank.

[0044] S5: Post-treatment strengthening: The foam blank is taken out and immersed in an ethanol solution of 3% silane coupling agent under vacuum for 1 hour, and then dried at 80°C for 3 hours to obtain a bio-based foam. The bio-based foam is applied to the field of indoor air purification to test its ability to adsorb and degrade formaldehyde; it is also applied to the field of food packaging to observe the effect of extending the shelf life of food.

[0045] Example 2

[0046] The bio-based foam of this embodiment is composed of: 100 parts of treated waste lignocellulose-derived bio-based solution, 6 parts of composite additives, 4 parts of azodicarbonamide, a foaming agent, and 9 parts of tributyl citrate, a bio-based plasticizer. The preparation process and subsequent application tests are completely consistent with those of Example 1.

[0047] Example 3

[0048] The bio-based foam of this embodiment comprises: 100 parts of treated waste lignocellulose-derived bio-based solution, 7 parts of composite additives, 5 parts of azodicarbonamide as a foaming agent, and 10 parts of tributyl citrate as a bio-based plasticizer. The preparation process and subsequent application tests are completely consistent with those of Example 1.

[0049] Example 4

[0050] The bio-based foam of this embodiment comprises: 100 parts of treated waste lignocellulose-derived bio-based solution, 8 parts of composite additives, 6 parts of azodicarbonamide as a foaming agent, and 11 parts of tributyl citrate as a bio-based plasticizer. The preparation process and subsequent application tests are completely consistent with those of Example 1.

[0051] Example 5

[0052] The bio-based foam of this embodiment is composed of: 100 parts of treated waste lignocellulose-derived bio-based solution, 9 parts of composite additives, 4 parts of azodicarbonamide, a foaming agent, and 9 parts of tributyl citrate, a bio-based plasticizer. The preparation process and subsequent application tests are completely consistent with those of Example 1.

[0053] Example 6

[0054] The bio-based foam of this embodiment comprises: 100 parts of treated waste lignocellulose-derived bio-based solution, 10 parts of composite additives, 3 parts of azodicarbonamide as a foaming agent, and 8 parts of tributyl citrate as a bio-based plasticizer. The preparation process and subsequent application tests are completely consistent with those of Example 1.

[0055] Example 7

[0056] The bio-based foam of this embodiment, the component ratio and subsequent application test are the same as those of Example 1. The difference lies in the preparation process of the composite additive. Preparation of the composite additive of this embodiment: Nano titanium dioxide and chitosan are mixed in a mass ratio of 1:3, and an alkaline environment is adjusted with a sodium hydroxide solution with a mass fraction of 6%, and the reaction is carried out at 70°C for 2.5 hours to generate a composite additive, which is obtained by centrifugation at 6000r / min for 12 minutes after the reaction is completed.

[0057] Example 8

[0058] The bio-based foam of this embodiment, the component ratio and subsequent application test are the same as those of Example 1. The difference lies in the preparation process of the composite additive. Preparation of the composite additive of this embodiment: nano titanium dioxide and chitosan are mixed in a mass ratio of 1:2.5, an alkaline environment is adjusted with a sodium hydroxide solution with a mass fraction of 8%, and the reaction is carried out at 80°C for 3 hours to generate a composite additive, which is obtained by centrifugation at 8000r / min for 15 minutes after the reaction is completed.

[0059] Example 9

[0060] The components and subsequent application tests of the bio-based foam of this embodiment are the same as those of Example 1. The difference lies in some parameters of the preparation process: acid hydrolysis with a sulfuric acid solution of 12% by mass at 125°C for 1.5 hours; enzymatic hydrolysis and saccharification with a cellulase and saccharifying enzyme complex with a mass ratio of 1:1.5 (the enzyme addition amount is 4% of the raw material mass). Microwave activation parameters are: oven temperature 160°C, pressure 0.6MPa, and foaming time 1.5 hours.

[0061] Example 10

[0062] The bio-based foam of this embodiment includes 100 parts of treated waste lignocellulose-derived bio-based solution, 7 parts of composite additives, 5 parts of azodicarbonamide as a foaming agent, and 10 parts of tributyl citrate as a bio-based plasticizer. The preparation steps include:

[0063] S1: Preparation of bio-based raw materials: Acid hydrolyze the waste lignocellulose with a 13% by mass sulfuric acid solution at 130°C for 2 hours, then add a cellulase and saccharifying enzyme complex in a mass ratio of 1:2 (the enzyme addition amount is 5% of the raw material mass) for enzymatic saccharification to obtain a bio-based solution, adjust the pH to 5.5, and set aside.

[0064] S2: Preparation of functional additives: same as Example 1.

[0065] S3: Construction of mixed foaming system: same as Example 1.

[0066] S4: Foaming molding: Pour the mixed liquid into a mold, put it into an oven preheated to 170°C, and maintain it at a pressure of 0.7MPa for 1.5 hours for foaming molding to form a bio-based foam blank.

[0067] S5: Post-treatment strengthening: The foam blank is taken out, immersed in an ethanol solution of silane coupling agent with a mass fraction of 4% under vacuum for 1.5 hours, and then dried at 90° C. for 4 hours to obtain a bio-based foam. The application test is the same as in Example 1.

[0068] Embodiment 11

[0069] The preparation method of the bio-based foam in this embodiment is similar to that in embodiment 10, except that the post-treatment strengthening process in this embodiment is as follows: the foam blank is taken out, immersed in an ethanol solution of 5% by mass silane coupling agent under vacuum for 2 hours, and then dried at 100° C. for 5 hours to obtain the bio-based foam. The application test is the same as that in embodiment 1.

[0070] Example 12

[0071] The preparation methods of the bio-based foam in this embodiment are similar to those in embodiment 10, except that the foaming process in this embodiment is as follows: the mixed solution is poured into a mold, placed in an oven preheated to 180°C, and maintained at a pressure of 1 MPa for 2 hours for foaming to form a bio-based foam blank. The remaining processes and parameters are the same as those in embodiment 10. The application test is the same as in embodiment 1.

[0072] Comparative Example 1

[0073] The bio-based foam of this comparative example comprises: 100 parts of the treated waste lignocellulose-derived bio-based solution, 3 parts of azodicarbonamide as a foaming agent, and 8 parts of tributyl citrate as a bio-based plasticizer. No composite additives are added during the preparation process, and the rest of the preparation process and subsequent application tests are completely consistent with those of Example 1.

[0074] Comparative Example 2

[0075] The bio-based foam of this comparative example comprises: 100 parts of the treated waste lignocellulose-derived bio-based solution, 5 parts of the composite additive, and 8 parts of the bio-based plasticizer tributyl citrate. No azodicarbonamide, a foaming agent, is added during the preparation process, and the rest of the preparation process and subsequent application tests are completely consistent with those of Example 1.

[0076] Comparative Example 3

[0077] The bio-based foam of this comparative example comprises: 100 parts of the treated waste lignocellulose-derived bio-based solution, 5 parts of the composite additive, and 3 parts of the foaming agent azodicarbonamide. No bio-based plasticizer tributyl citrate is added during the preparation process, and the rest of the preparation process and subsequent application tests are completely consistent with Example 1.

[0078] The performance of the bio-based foams prepared in the examples and comparative examples was tested using the "Method for Determining the Purification Effect of Indoor Air Purification Materials", "Method for Detecting Microbiological Indicators of Food Packaging Materials and Products", and "Food Freshness Evaluation Standards". For indoor air purification applications, according to the "Method for Determining the Purification Effect of Indoor Air Purification Materials", a specific experimental cabin was used to simulate the indoor air environment, and a certain amount of harmful gases such as formaldehyde and benzene were placed. The bio-based foam samples were placed in it, and the concentration of harmful gases in the cabin was regularly tested to calculate the adsorption and degradation efficiency of harmful gases such as formaldehyde and benzene.

[0079] For food packaging applications, in accordance with the "Microbial Index Detection Methods for Food Packaging Materials and Products", microbial index tests, such as total colony count and coliform group, are carried out on foods packaged with bio-based foam at different times; at the same time, based on the "Food Freshness Evaluation Standards", the freshness of food is monitored through sensory evaluation, physical and chemical index testing (such as moisture content, pH value, etc.), and the impact of bio-based foam on the shelf life of food is comprehensively evaluated.

[0080] Table 1 Performance test results of bio-based foam in indoor air purification applications of examples and comparative examples

[0081]

[0082]

[0083] Table 2 Performance test results of bio-based foam in food packaging applications of examples and comparative examples

[0084]

[0085]

[0086] As can be seen from Table 1 and Table 2, the bio-based foam prepared by the method of the present invention can effectively adsorb and degrade harmful gases such as formaldehyde and benzene in indoor air purification applications, and the formaldehyde adsorption degradation rate can reach more than 75% within 24 hours, and the benzene adsorption degradation rate can reach more than 68% within 48 hours. In food packaging applications, it can significantly extend the number of days for food microbiological indicators to meet the standards and the number of days for freshness to remain good, and the number of days for microbiological indicators to meet the standards can reach more than 10 days, and the number of days for freshness to remain good can reach more than 7 days.

[0087] The comparative examples have significantly poorer performance in indoor air purification and food packaging due to the lack of composite additives, foaming agents or bio-based plasticizers. In indoor air purification, the adsorption and degradation rates of formaldehyde and benzene are greatly reduced; in food packaging applications, the number of days for food microbiological indicators to meet standards and the number of days for freshness to remain good are significantly shortened.

[0088] It can be seen that the bio-based foam prepared by the present invention has good application performance in the fields of indoor air purification and food packaging, can meet actual use needs, and shows good application value.

[0089] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for preparing a bio-based foam, characterized in that: The following steps are involved: S1: Preparation of bio-based raw materials: After pre-treatment of waste lignocellulose by acid hydrolysis, enzymatic saccharification is performed to obtain a bio-based solution rich in sugars, and the pH thereof is adjusted to 5-6 for standby use; S2: Preparation of functional additives: react nano-titanium dioxide with chitosan under alkaline conditions to generate a composite additive with antibacterial and photocatalytic properties, the reaction temperature is controlled at 60-80°C, and the reaction time is 2-3 hours; S3: Construction of mixed foaming system: Add the composite additive prepared in step S2, the foaming agent azodicarbonamide and the bio-based plasticizer tributyl citrate to the bio-based solution obtained in step S1, and stir to mix evenly at a stirring speed of 300-500 r / min for 15-25 minutes; S4: Foaming molding: pour the above mixed solution into a mold, put it into an oven preheated to 150-180°C, and keep it at this temperature for 1-2 hours for foaming molding to form a bio-based foam blank; S5: Post-treatment strengthening: The bio-based foam blank is taken out, immersed in an ethanol solution containing a silane coupling agent under a vacuum environment for 1-2 hours, and then dried at 80-100° C. for 3-5 hours to obtain the final bio-based foam.

2. The preparation method according to claim 1, characterized in that: In the step S1, the acid used in the acid hydrolysis pretreatment is a sulfuric acid solution with a mass fraction of 10%-15%, the acid hydrolysis temperature is 120-130° C., and the time is 1-2 hours.

3. The preparation method according to claim 1, characterized in that: In the step S2, the mass ratio of nano-titanium dioxide to chitosan is 1:2-3, and the alkaline condition is adjusted by a sodium hydroxide solution with a mass fraction of 5%-8%.

4. The preparation method according to claim 1, characterized in that: In the step S3, the mass ratio of the bio-based solution, the composite additive, the foaming agent azodicarbonamide and the bio-based plasticizer tributyl citrate is 100:5-10:3-6:8-12.

5. The preparation method according to claim 1, characterized in that: In step S4, the pressure in the oven is maintained at 0.5-1 MPa.

6. The preparation method according to claim 1, characterized in that: In step S5, the mass fraction of the silane coupling agent in the ethanol solution is 3%-5%.

7. The preparation method according to claim 2, characterized in that: The enzyme used in the enzymatic saccharification process is a composite enzyme of cellulase and saccharifying enzyme, the mass ratio of the two is 1:1-2, and the amount of enzyme added is 3%-5% of the mass of the bio-based raw material.

8. The preparation method according to claim 3, characterized in that: After the reaction is completed, the composite additive is obtained by centrifugal separation at a centrifugal speed of 5000-8000 r / min for 10-15 minutes.

9. A bio-based foam, characterized in that: The bio-based foam is prepared according to the preparation method according to any one of claims 1 to 8. The foam has good antibacterial properties, with the antibacterial rates against Escherichia coli and Staphylococcus aureus reaching more than 90%, and has the ability to photocatalytically degrade organic pollutants.

10. An application of bio-based foam, characterized in that: The bio-based foam is applied in the field of indoor air purification, and can adsorb and photocatalytically degrade harmful gases such as formaldehyde and benzene in the air; it can also be applied in the field of food packaging, and its antibacterial properties can be used to extend the shelf life of food.

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