Lignocellulose bioplastic based on enteromorpha and preparation method thereof

Abstract

The invention relates to the field of harmless treatment and processing application of marine plankton, and provides an enteromorpha-based lignocellulose bioplastic and a preparation method thereof, and the preparation method comprises the following steps: 1) airing and crushing enteromorpha; (2) mixing a product obtained in the step (1) with a NaOH solution, carrying out wall breaking treatment in a high-pressure environment, and then magnetically stirring at 95 DEG C for 2-4 hours; (3) carrying out acid sedimentation on the mixed solution; the method comprises the following steps of 1, preparing lignocellulose, 2, carrying out solid-liquid separation, taking a precipitate, and re-dispersing the precipitate in water to obtain a mixed suspension liquid, 5, carrying out ultrasonic dispersion on the mixed suspension liquid, and uniformly stirring to obtain a lignocellulose film-forming slurry, and 6, degassing the slurry obtained in step 5, spreading the slurry on a substrate, drying the slurry, and uncovering the film to obtain the bioplastics.

Description

Technical Field

[0001] The invention relates to the field of harmless treatment and processing of marine plankton, and in particular to a lignocellulose bioplastic based on enteromorpha and a preparation method thereof. Background Art

[0002] Plastic pollution is a global environmental problem. Millions of tons of plastic waste enter the natural environment every year, causing serious damage to the ecosystem. Plastics rely on fossil fuels in the production process, release harmful substances, and contain potentially toxic chemicals. Plastic waste is difficult to degrade and recycle in the natural environment, causing environmental pollution, ecological damage and microplastic problems. Microplastic particles have spread all over the world, posing a huge threat to human health. Therefore, the use of renewable biological resources to develop a safe and degradable bioplastic to replace these petrochemical plastics has received widespread attention.

[0003] The massive reproduction and aggregation of Enteromorpha can lead to deterioration of water quality, damage to aquatic products, disruption of ecological balance, and impact on tourism. Enteromorpha disasters have a serious impact on the balance of marine ecosystems and require effective governance methods. They contain rich biomass (such as cellulose) resources and are particularly promising for the production of degradable bioplastics. Because algae contain a small amount of natural physical and chemical barriers, cellulose can be obtained without strict chemical treatment. Studies have shown that algae cellulose fibers are small and fine, with a higher length, larger aspect ratio and smaller particle size than terrestrial plant cellulose, which is particularly attractive for the preparation of bio-based materials. Therefore, from the perspectives of environment, economy and sustainability, it is of great significance to convert Enteromorpha into biodegradable bioplastics.

[0004] However, there are few studies on the direct production of bioplastics from algae, and even fewer reports on the conversion of Enteromorpha into bioplastics. Currently reported algae-produced bioplastics generally exhibit poor properties, such as low mechanical strength, flexibility, and water stability, which hinders the development and application of such materials. Therefore, it is challenging and meaningful to convert Enteromorpha into degradable bioplastics in a simple and sustainable way. Summary of the invention

[0005] In order to solve the problems of plastic environmental pollution existing in the prior art, as well as the problems that the current bioplastics have poor mechanical properties, are difficult to recycle and reuse, and require the addition of chemical reagents such as film-forming agents and plasticizers, the present invention proposes a wood cellulose bioplastic based on Enteromorpha and a preparation method thereof, with the aim of providing a method for green, simple and sustainable preparation of degradable multifunctional bioplastics based on Enteromorpha, wherein the bioplastics obtained by the method have good mechanical properties and are degradable and recyclable.

[0006] The present invention provides a method for preparing a lignocellulose bioplastic based on Enteromorpha, comprising the following steps: 1) Dry and crush the Enteromorpha; 2) mixing the product obtained in step 1) with a NaOH solution, breaking the cell wall under high pressure, and then magnetically stirring at 95° C. for 2-4 h to promote the separation of lignin and cellulose; 3) adjusting the pH of the mixture obtained in step 2) to acidic using a dilute hydrochloric acid solution to obtain a mixed solution, and then subjecting the mixed solution to acid precipitation; 4) performing solid-liquid separation on the mixed solution after acid precipitation obtained in step 3), taking the precipitate, and redispersing it in water to obtain a mixed suspension; 5) ultrasonically dispersing the mixed suspension obtained in step 4) and stirring until uniform to obtain a lignocellulose film-forming slurry; 6) Degas the slurry obtained in step 5), spread it onto a substrate, and peel off the film after drying to obtain bioplastic.

[0007] Preferably, in step 1), the Enteromorpha is crushed and then passed through a 200-mesh sieve; the present invention uses Enteromorpha as a raw material, and utilizes its lignin and cellulose for in-situ recombination to obtain lignocellulose bioplastics. In addition, other algae with similar compositions to Enteromorpha can also be applied to this method.

[0008] Preferably, in step 2), the concentration of the NaOH solution is 1-2.5 M, the mass volume ratio of the mixture of the product obtained in step 1) and the NaOH solution is 1 g:(25-50) mL, and the pressure of the high pressure environment is 2.0-3.0 MPa.

[0009] Preferably, in step 2), the cell wall breaking treatment is ultrasonic-microwave synergistic treatment, the microwave power is 300-700W, the ultrasonic power is 300-500W, and the treatment time is 10-20min; Under the environment of high pressure coordinated ultrasonic microwaves, the rapid heating of microwaves will quickly break the plant cell wall structure, exposing it to the alkaline solution more quickly, thereby accelerating the separation of cellulose and lignin in Enteromorpha.

[0010] Preferably, in step 3), the pH of the mixture is adjusted to 2-3 to obtain a mixed solution, the acid precipitation temperature is 25°C, and the standing time is 4-6 h; the acid precipitation step can make the lignin in the mixed solution settle in situ on the underlying cellulose substrate to promote their bonding.

[0011] Preferably, in step 4), the amount of water used when the precipitate is redispersed needs to be determined based on the amount of the precipitate. More specifically, every 10 g of Enteromorpha powder raw material corresponds to 100 mL of water when it is redispersed. If the precipitation ratio is too high, the cellulose content ratio is too high, which will lead to local acoustic cavitation in step 5) causing polymer agglomeration near the ultrasonic probe, affecting the transmission of sound waves and making it difficult for cellulose to be dispersed in water to form a uniform cellulose slurry. This solid-liquid separation slurry makes it impossible to use it for film laying. In addition, it will also damage the life of the ultrasonic probe. If the ratio is too low, the matrix concentration will be reduced, making it difficult to form a film.

[0012] Preferably, in step 4), the solid-liquid separation is filtration or centrifugation.

[0013] Preferably, in step 5), the ultrasonic power of the ultrasonic dispersion is 200-500 W, the ultrasonic time is 5-20 min, and then magnetic stirring is performed until it is completely uniform; the ultrasonic treatment allows the lignocellulose to be quickly and evenly dispersed in the water and form a uniform suspension for further production of bioplastic film.

[0014] Preferably, in step 6), the slurry is spread onto the substrate, the thickness of the slurry is 0.3-0.5 cm, and the drying condition is drying at 25-45°C or natural drying until the film can be peeled off smoothly, and the drying is drying or natural drying; too thin or too thick is not conducive to the stable formation of the film, and the temperature should not be too high, as too high a temperature can easily cause the film to break during the formation process.

[0015] The present invention breaks the cell wall of Enteromorpha by microwave and ultrasonic treatment under high pressure, then separates cellulose and lignin by alkali treatment, and then uses acid precipitation to precipitate lignin on cellulose in situ. Cellulose and lignin of single components are difficult to form films or have poor performance after forming films.

[0016] The lignocellulosic bioplastic is prepared by the above method. During the preparation process, other impurities (hemicellulose and some oligosaccharides and polysaccharides) are removed in the subsequent filtration step by high-pressure microwave ultrasonic treatment and alkali treatment.

[0017] The present invention utilizes the principle of in-situ regeneration of lignin to make it tightly entangled with cellulose fibers and form a multi-scale structure, which is beneficial to improving the mechanical properties of the film. The prepared bioplastic has high mechanical properties, water resistance, UV resistance, heat resistance, degradability and recyclability, and has great potential to replace petrochemical plastic products.

[0018] The enteromorpha-based lignocellulose bioplastic and the preparation method thereof provided by the present invention have the following advantages and beneficial effects: (1) The present invention makes the most of Enteromorpha, which not only avoids the environmental and ecological damage caused by Enteromorpha, but also improves the application value of Enteromorpha; (2) The obtained bioplastic has high mechanical strength (up to 12.80 MPa), high water stability (stable in water for more than 2 months), UV resistance (can absorb almost all UV rays), and is completely degradable (biodegradable within 3 months); (3) The obtained bioplastics are recyclable. After the use cycle ends, the bioplastics can be processed again to form new bioplastics after simple treatment; (4) The method used does not require other chemical reagents such as film-forming agents and plasticizers. It is safe, green, simple and easy to operate, low-cost, and easy to achieve sustainable mass production; (5) The prepared bioplastics can be used as substitutes for petrochemical plastics and have great application prospects in the field of packaging materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The mold and surface image of the bioplastic prepared in Example 1; Figure 2 A schematic diagram of folding and curling of the bioplastic prepared in Example 1; Figure 3 The water stability test of the bioplastic prepared in Example 1 was performed with a pure cellulose film as a control; Figure 4 UV resistance test of the bioplastic prepared in Example 1; Figure 5 Degradability test of the bioplastic prepared in Example 1 and commercially available plastic in soil and natural environment; Figure 6 Recyclability test of the bioplastic prepared in Example 1. DETAILED DESCRIPTION

[0020] The embodiments of the present invention will be further described in detail by examples. It is necessary to point out that the following examples are only used to further illustrate the present invention, and the embodiments of the present invention are not limited thereto. Some non-essential adjustments and improvements made by people familiar with the relevant fields according to the above invention scheme still belong to the protection scope of the present invention.

[0021] The Enteromorpha used in the following examples was collected in Qingdao; the other substances and reagents were all commercially available unless otherwise specified.

[0022] Example 1 A method for preparing a lignocellulosic bioplastic based on Enteromorpha comprises the following steps: Select Enteromorpha, wash and dry it, and crush it through a 200-mesh sieve to obtain Enteromorpha powder. Weigh 10 g Enteromorpha powder, mix it with 2 M NaOH solution at a ratio of 1 g:25 mL, place it in a high-pressure environment of 2.0 MPa, and treat it with ultrasonic microwave synergy for 10 min (microwave power: 400 W; ultrasonic power: 300 W), and stir it magnetically at 95 ° C for 2 h. After cooling, use dilute hydrochloric acid to adjust the pH of the mixture to 2.5. Then let it stand at room temperature for 5 h, filter the precipitate, and redisperse it in 100 mL of water. After mixing evenly, treat it with 300W ultrasound for 5 min to form a lignocellulose film-forming slurry, then stir it magnetically until it is completely uniform, degas it, pour it onto a glass plate of appropriate size (the slurry thickness is about 0.5 cm), dry it at room temperature and remove the film.

[0023] Figure 1 The image shows the film casting of lignocellulose slurry. 600mL of slurry was evenly poured onto a 150cm×15cm glass plate to a thickness of 0.5cm. After 36-48 hours of natural drying, the lignocellulose bioplastic was obtained by gently peeling it off.

[0024] like Figure 2 As shown, the prepared bioplastics have good flexibility and can still maintain their original shape after arbitrary folding and curling.

[0025] Example 2 A method for preparing a lignocellulosic bioplastic based on Enteromorpha comprises the following steps: Select Enteromorpha, wash and dry it, and crush it through a 200-mesh sieve to obtain Enteromorpha powder. Weigh 10 g Enteromorpha powder, mix it with 2 M NaOH solution at a ratio of 1 g:50 mL, place it in a high-pressure environment of 2.0 MPa, and treat it with ultrasonic microwave synergy for 10 min (microwave power: 400 W; ultrasonic power: 300 W), and stir it magnetically at 95 ° C for 2 h. After cooling, use dilute hydrochloric acid to adjust the pH of the mixture to 2.5. Then let it stand at room temperature for 5 h, filter the precipitate, and redisperse it in 100 mL of water. After mixing evenly, treat it with 300W ultrasound for 5 min to form a lignocellulose film-forming slurry, then stir it magnetically until it is completely uniform, degas it, pour it onto a glass plate of appropriate size (the slurry thickness is about 0.5 cm), dry it at room temperature and remove the film.

[0026] Example 3 A method for preparing a lignocellulosic bioplastic based on Enteromorpha comprises the following steps: Select Enteromorpha, wash and dry it, and crush it through a 200-mesh sieve to obtain Enteromorpha powder. Weigh 10 g Enteromorpha powder, mix it with 2.5M NaOH solution at a ratio of 1 g:25mL, place it in a high-pressure environment of 2.0 MPa, and treat it with ultrasonic microwave synergy for 10 min (microwave power: 400 W; ultrasonic power: 300 W), and stir it magnetically at 95°C for 2 h. After cooling, use dilute hydrochloric acid to adjust the pH of the mixture to 2.5. Then let it stand at room temperature for 5 h, filter the precipitate, and redisperse it in 100 mL of water. After mixing evenly, treat it with 300W ultrasound for 5 min to form a lignocellulose film-forming slurry, then stir it magnetically until it is completely uniform, degas it, pour it onto a glass plate of appropriate size (the slurry thickness is about 0.5 cm), dry it at room temperature and remove the film.

[0027] Example 4 A method for preparing a lignocellulosic bioplastic based on Enteromorpha comprises the following steps: Select Enteromorpha, wash and dry it, and crush it through a 200-mesh sieve to obtain Enteromorpha powder. Weigh 10 g Enteromorpha powder, mix it with 2 M NaOH solution at a ratio of 1 g:25 mL, place it in a high-pressure environment of 2.0 MPa, and treat it with ultrasonic microwave synergy for 10 min (microwave power: 300 W; ultrasonic power: 400 W), and stir it magnetically at 95 ° C for 4 h. After cooling, use dilute hydrochloric acid to adjust the pH of the mixture to 2.5. Then let it stand at room temperature for 5 h, filter the precipitate, and redisperse it in 100 mL of water. After mixing evenly, treat it with 300W ultrasound for 5 min to form a lignocellulose film-forming slurry, then stir it magnetically until it is completely uniform, degas it, pour it onto a glass plate of appropriate size (the slurry thickness is about 0.5 cm), dry it at room temperature and remove the film.

[0028] Example 5 A method for preparing a lignocellulosic bioplastic based on Enteromorpha comprises the following steps: Select Enteromorpha, wash and dry it, and crush it through a 200-mesh sieve to obtain Enteromorpha powder. Weigh 10 g Enteromorpha powder, mix it with 2 M NaOH solution at a ratio of 1 g:25 mL, place it in a high-pressure environment of 2.0 MPa, and treat it with ultrasonic microwave synergy for 10 min (microwave power: 300 W; ultrasonic power: 400 W), and stir it magnetically at 95 ° C for 4 h. After cooling, use dilute hydrochloric acid to adjust the pH of the mixture to 2.3. Then let it stand at room temperature for 5 h, filter the precipitate, and redisperse it in 100 mL of water. After mixing evenly, treat it with 300W ultrasound for 5 min to form a lignocellulose film-forming slurry, then stir it magnetically until it is completely uniform, degas it, pour it onto a glass plate of appropriate size (the slurry thickness is about 0.5 cm), dry it at room temperature and remove the film.

[0029] Example 6 A method for preparing a lignocellulosic bioplastic based on Enteromorpha comprises the following steps: Select Enteromorpha, wash and dry it, and crush it through a 200-mesh sieve to obtain Enteromorpha powder. Weigh 10 g Enteromorpha powder, mix it with 2 M NaOH solution at a ratio of 1 g:25 mL, place it in a high-pressure environment of 2.0 MPa, and treat it with ultrasonic microwave synergy for 10 min (microwave power: 300 W; ultrasonic power: 400 W), and stir it magnetically at 95 ° C for 4 h. After cooling, use dilute hydrochloric acid to adjust the pH of the mixture to 2.5. Then let it stand at room temperature for 5 h, filter the precipitate, and redisperse it in 100 mL of water. After mixing evenly, treat it with 400W ultrasound for 5 min to form a lignocellulose film-forming slurry, then stir it magnetically until it is completely uniform, degas it, pour it onto a glass plate of appropriate size (the slurry thickness is about 0.5 cm), dry it at room temperature and remove the film.

[0030] Comparative Example 1 A method for preparing a lignocellulosic bioplastic based on Enteromorpha comprises the following steps: Select Enteromorpha, wash and dry it, and crush it through a 200-mesh sieve to obtain Enteromorpha powder. Weigh 10 g Enteromorpha powder, mix it with 2 M NaOH solution at a ratio of 1 g:25 mL, place it in a high-pressure environment of 2.0 MPa, and treat it with ultrasonic microwave synergy for 10 min (microwave power: 400 W; ultrasonic power: 300 W), stir it magnetically at 95 ° C for 2 h, and after cooling, filter the precipitate and redisperse it in 100 mL of water. After mixing evenly, treat it with 300 W ultrasonic treatment for 5 min to form a lignocellulose film-forming slurry, degas it and pour it onto a glass plate of appropriate size (the slurry thickness is about 0.5 cm). Due to the lack of lignin functional effects, it is difficult to form a film.

[0031] Comparative Example 2 A method for preparing a lignocellulosic bioplastic based on Enteromorpha comprises the following steps: Select Enteromorpha, wash and dry it, and crush it through a 200-mesh sieve to obtain Enteromorpha powder. Weigh 10 g Enteromorpha powder, mix it with 2 M NaOH solution at a ratio of 1 g:25 mL, place it in a high-pressure environment of 2.0 MPa, and treat it with ultrasonic microwave synergy for 10 min (microwave power: 400 W; ultrasonic power: 300 W), and stir it magnetically at 95 ° C for 2 h. After cooling, use dilute hydrochloric acid to adjust the pH of the mixture to 2.5. Then let it stand at room temperature for 5 h, filter the precipitate, and redisperse it in 100 mL of water. After degassing, pour it onto a glass plate of appropriate size (thickness 0.5 cm). Since wood cellulose is not well dispersed in water, no film material can be obtained.

[0032] Comparative Example 3 A method for preparing a lignocellulosic bioplastic based on Enteromorpha comprises the following steps: Select Enteromorpha, wash and dry it, and crush it through a 200-mesh sieve to obtain Enteromorpha powder. Weigh 10 g Enteromorpha powder, mix it with 2 M NaOH solution at a ratio of 1 g:25 mL, and stir it magnetically at 95 ° C for 2 h. After cooling, use dilute hydrochloric acid to adjust the pH of the mixture to 2.5. Then let it stand at room temperature for 5 h, filter the precipitate, and redisperse it in 100 mL of water. After mixing evenly, 400W ultrasonic treatment for 5 min forms a lignocellulose film-forming slurry, which is then magnetically stirred until completely uniform, degassed and poured onto a glass plate of a suitable size (the slurry thickness is about 0.5 cm), and dried at room temperature to remove the film. A complete film cannot be obtained. The main reason is that Comparative Example 3 did not perform high-pressure microwave ultrasonic wall breaking treatment, and the efficient separation of biomass (i.e., lignin and cellulose) could not be achieved during the preparation process. The Enteromorpha without biomass separation still retains the original Enteromorpha structure to a large extent, making it difficult to reassemble into a film.

[0033] The preparation schemes of Comparative Examples 1-3 above are all difficult to form a complete film.

[0034] Experimental example The mechanical properties were measured by cutting the membrane into rectangles of 100 mm × 50 mm and determining its tensile strength using an automatic tensile testing machine with an initial clamping distance and speed of 50 mm and 1 mm / s, respectively.

[0035] Table 1 is a performance comparison of the bioplastic prepared in Example 1 and commercially available cling film (PVC) tensile strength UV resistance Degradable Recyclable Example 1 12.80 MPa Can absorb almost all UV rays Degradation in 3 months Can be recycled Commercially available plastic wrap 10.15 MPa none none none Lignocellulosic bioplastics exhibit excellent water resistance. Figure 3 As shown, the lignocellulosic bioplastic obtained in Example 1 was completely immersed in water and stored at room temperature. After 60 days, it still maintained its original shape without any deformation or cracking.

[0036] For better comparison, the inventors also used Enteromorpha cellulose to prepare bioplastics. The preparation method is as follows: 10g of Enteromorpha powder that has been washed, dried, crushed and passed through a 200-mesh sieve is added to a 5 wt% NaClO2 solution at a ratio of 1 g: 20mL, and the pH of the NaClO2 solution with Enteromorpha powder is adjusted to 4.6 with acetic acid, and stirred at 90°C for 4h, and the precipitate is filtered. Subsequently, the precipitate is added to a 2.5 M NaOH solution (at a ratio of 1g: 20mL), stirred at 90°C for 2h, and the cellulose is collected by filtration. After repeated rinsing with distilled water, the obtained cellulose is dispersed again in 100mL of deionized water and ultrasonically treated at 300W for 5min. A cellulose slurry is obtained, and the cellulose slurry is cast onto a glass plate after degassing, with a thickness of about 0.5cm, and the film is removed after drying at room temperature.

[0037] The cellulose bioplastic obtained as a control was immersed in water under the same conditions as above, and it quickly deformed, and eventually it became difficult to maintain its original shape, and its structure decomposed.

[0038] like Figure 4 As shown, the bioplastic film obtained in Example 1 was cut into a rectangle of 50 mm × 15 mm, and its transmission spectrum was measured in the wavelength range of 200-800 nm using a UV-visible spectrophotometer. Lignocellulosic bioplastics absorb almost all of the spectrum in the ultraviolet region (400-200 nm), indicating that they have excellent anti-ultraviolet properties.

[0039] The inventors have further studied their degradability and recyclability. Figure 5 As shown, the common commercially available PVC petrochemical plastic was used as a control, the film was cut into 5 cm × 5 cm rectangles, and the lignocellulosic bioplastic and PVC petrochemical plastic prepared in Example 1 were buried in the soil at a depth of about 5 cm ( Figure 5 Left) and in the soil of a garden placed outdoors in its natural environment ( Figure 5 Right), dug out and photographed at regular intervals to see if it has degraded. In the soil, the bioplastic was soaked and began to break after 20 days of swelling, because soil microorganisms directly attacked and digested the lignin and cellulose in the bioplastic. Ultimately, the bioplastic was almost completely degraded after 3 months, while PVC always maintained its initial form, reflecting the superiority of the prepared lignocellulosic bioplastic in terms of degradability. Similarly, after months of exposure to soil with different weather changes, the original structure of the bioplastic was almost completely degraded, while the PVC plastic still maintained its original form, indicating that the lignocellulosic bioplastic provided by the present invention has good degradability and environmental friendliness.

[0040] Figure 6 The recyclability of lignocellulose. The lignocellulose bioplastic prepared in Example 1 was stored for 1 month and then crushed. They were mixed in 80°C hot water at a ratio of 1g:20mL, vigorously stirred for 2 minutes, then magnetically stirred at 90°C for 2 hours, and ultrasonically treated at 300 W for 5 minutes. The obtained treatment liquid was spread on a glass plate (the slurry thickness was about 0.5cm), and after natural drying, it was torn off to obtain new bioplastics. The degradable and recyclable properties that petrochemical plastics do not have make the prepared lignocellulose bioplastics particularly promising as a substitute for petrochemical products, and can be used in packaging materials and other fields.

[0041] The present invention makes maximum use of Enteromorpha, which not only avoids its damage to the environment and ecology, but also enhances the application value of Enteromorpha; the obtained bioplastic has high mechanical strength, is completely degradable, and has water stability and UV resistance; the obtained bioplastic is recyclable, and the bioplastic after the use cycle ends can be formed into a film again after simple treatment.

[0042] The above embodiments are preferred implementations of the present invention, which mainly demonstrate and describe the main features and basic principles of the present invention. However, the implementation of the present invention is not limited to the above embodiments, and any modification, alteration, substitution, combination, simplification made by any person familiar with the relevant fields and technologies without departing from the spirit and scope of the present invention shall be deemed to be within the scope of the present invention.

Claims

1. A method for preparing a lignocellulosic bioplastic based on Enteromorpha, characterized in that: The following steps are involved: 1) Dry and crush the Enteromorpha; 2) mixing the product obtained in step 1) with a NaOH solution, performing a cell wall breaking treatment under a high pressure environment, and then magnetically stirring at 95° C. for 2-4 h; 3) adjusting the pH of the mixture obtained in step 2) to acidic using a dilute hydrochloric acid solution to obtain a mixed solution, and then subjecting the mixed solution to acid precipitation; 4) performing solid-liquid separation on the mixed solution after acid precipitation obtained in step 3), taking the precipitate, and redispersing it in water to obtain a mixed suspension; 5) ultrasonically dispersing the mixed suspension obtained in step 4) and stirring until uniform to obtain a lignocellulose film-forming slurry; 6) Degas the slurry obtained in step 5), spread it onto a substrate, and peel off the film after drying to obtain bioplastic.

2. The method for preparing enteromorpha-based lignocellulosic bioplastic according to claim 1, characterized in that: In step 1), the Enteromorpha is crushed and passed through a 200-mesh sieve.

3. The method for preparing enteromorpha-based lignocellulose bioplastic according to claim 1, characterized in that: In step 2), the concentration of the NaOH solution is 1-2.5 M, the mass volume ratio of the mixture of the product obtained in step 1) and the NaOH solution is 1 g:(25-50) mL, and the pressure of the high pressure environment is 2.0-3.0 MPa.

4. The method for preparing enteromorpha-based lignocellulose bioplastic according to claim 1, characterized in that: In step 2), the cell wall breaking treatment is ultrasonic-microwave coordinated treatment, the microwave power is 300-700W, the ultrasonic power is 300-500W, and the treatment time is 10-20min.

5. The method for preparing enteromorpha-based lignocellulose bioplastic according to claim 1, characterized in that: In step 3), the pH of the mixture is adjusted to 2-3 to obtain a mixed solution, the temperature of acid precipitation is 25°C, and the standing time is 4-6 hours.

6. The method for preparing enteromorpha-based lignocellulose bioplastic according to claim 1, characterized in that: Every 10 g of the Enteromorpha powder raw material in step 1) corresponds to 100 mL of water when it is redispersed in step 4).

7. The method for preparing enteromorpha-based lignocellulose bioplastic according to claim 1, characterized in that: In step 4), the solid-liquid separation is filtration or centrifugation.

8. The method for preparing enteromorpha-based lignocellulose bioplastic according to claim 1, characterized in that: In step 5), the ultrasonic power of the ultrasonic dispersion is 200-500 W, the ultrasonic time is 5-20 min, and then magnetic stirring is performed until it is completely uniform.

9. The method for preparing enteromorpha-based lignocellulose bioplastic according to claim 1, characterized in that: In step 6), the slurry is spread evenly on the substrate, the thickness of the slurry is 0.3-0.5 cm, and the drying condition is drying at 25-45°C or drying naturally until the film can be peeled off smoothly.

10. Lignocellulosic bioplastic prepared by the preparation method according to any one of claims 1 to 9.

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