A method for extracting coconut shell soft tissue cellulose

Abstract

The present invention discloses a method for extracting coconut shell soft tissue cellulose, which comprises the following steps: Step S1. Separation: separating the outer soft tissue fibers of the coconut shell and sieving; Step S2. Crushing: crushing the sieved outer soft tissue fibers of the coconut shell, the temperature of crushing is -50 to -150 °C, and the rotation speed of crushing is 1000 - 5000 rpm; Step S3. Extraction: mixing the crushed outer soft tissue fibers of the coconut shell, acid, sodium hypochlorite and water, and heating and stirring; Step S4. Purification: soaking the product of Step S3 with a KOH solution and adding an acetic acid solution to obtain coconut shell soft tissue cellulose. The extraction method of the present invention makes full use of coconut shell resources, turns waste coconut shells into treasures, improves economic benefits and reduces environmental pollution at the same time.

Description

Technical Field

[0001] The present invention relates to the technical field of recycling of agricultural waste, and particularly relates to a method for extracting cellulose from the soft tissue of coconut shells. Background Art

[0002] In China, more than 10 million tons of coconuts are used to produce coconut soft drinks every year. Among them, the weight of coconut shells accounts for 70-80%. After manually grooving to extract coconut juice, the coconut shells with hard cortex are often treated by landfilling. This treatment method not only causes waste of land resources, but also does not make reasonable use of agricultural waste. We found in the previous separation and treatment of coconut shells that the outer layer of coconut shells is a relatively soft long fiber tissue, which is easy to separate by mechanical operation and has a high cellulose content, with the potential for high-value application; the sub-outer layer is harder and is easily oxidized to brown. Compared with the outer layer, it requires additional treatment and processing.

[0003] Under the background of green, low-carbon and "carbon neutral" sustainable development, more and more agricultural wastes including straws and bagasse are made into degradable raw materials and applied in fields such as disposable packaging, daily necessities, and biomass fuels. As an important agricultural waste, coconut shells also have development potential in the field of degradable materials after appropriate treatment, but there are few reports on the extraction process of cellulose from the soft tissue of coconut shells in the existing technology. Summary of the Invention

[0004] The present invention aims to at least solve the above technical problems in the existing technology. For this reason, the purpose of the present invention is to provide a method for extracting cellulose from the soft tissue of coconut shells, which makes full use of coconut shell resources, turns waste coconut shells into treasures, improves economic benefits and reduces environmental pollution at the same time.

[0005] In order to achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0006] The present invention provides a method for extracting cellulose from the soft tissue of coconut shells, including the following steps:

[0007] Step S1. Separation: Separate the soft tissue fibers of the outer layer of coconut shells and screen them.

[0008] Step S2. Crushing: Crush the screened soft tissue fibers of the outer layer of coconut shells. The temperature of crushing is -50 to -150 °C, and the rotation speed of crushing is 1000-5000 rpm.

[0009] Step S3. Extraction: Mix the crushed soft tissue fibers of the outer layer of coconut shells, acid, sodium hypochlorite and water, and heat and stir.

[0010] Step S4. Purification: Soak the product of Step S3 with a KOH solution, add an acetic acid solution, and obtain cellulose from the soft tissue of coconut shells.

[0011] In some embodiments, in step S1, the sieve mesh for sieving is larger than 40 mesh.

[0012] In some embodiments, the pulverization in step S2 may also be: pulverizing the outer soft tissue fibers of the coconut shell after sieving, vibrating and sieving, the temperature of pulverization is -50 to -150 °C, the rotation speed of pulverization is 1000 - 5000 rpm, and the sieve mesh for sieving is 80 - 400 mesh.

[0013] In some embodiments, in step S3, the dosage ratio of the outer soft tissue fibers of the coconut shell, acid, and sodium hypochlorite is 5 - 20 g: 1 - 10 mL: 2 - 10 g.

[0014] In some embodiments, in step S3, the extraction may also be: mixing the pulverized outer soft tissue fibers of the coconut shell, acid, sodium hypochlorite, and water, heating and stirring at 50 - 95 °C, repeatedly adding acid, sodium hypochlorite, and water, adding them 6 times repeatedly, and then performing post-treatment.

[0015] In some embodiments, the post-treatment is specifically suction filtration, washing with water until neutral, suction filtration, and drying.

[0016] In some preferred embodiments, the acid is selected from at least one of citric acid, glacial acetic acid, carbonic acid, ferric chloride, zinc chloride, and aluminum chloride.

[0017] In some embodiments, in step S4, the purification may also be: soaking the product of step S3 with a KOH solution, adding an acetic acid solution, filtering, washing until neutral, suction filtration, and drying to obtain coconut shell soft tissue cellulose.

[0018] In some embodiments, in step S4, the drying is selected from one of freeze drying, microwave drying, far-infrared drying, and vacuum drying.

[0019] In some embodiments, in step S4, the mass fraction of the KOH solution is 5 - 15%.

[0020] In some embodiments, the molar ratio of KOH to acetic acid is 1:1.

[0021] In some embodiments, in step S4, the soaking time is 15 - 40 min.

[0022] The beneficial effects of the present invention are:

[0023] (1) At the temperature and rotation speed adopted in the present invention, coconut shell soft tissue cellulose with uniform size is obtained, and this temperature and rotation speed will not have a negative impact on the yield and crystallinity of cellulose.

[0024] (2) With the increase in the number of repeated additions of sodium hypochlorite and acid, the yield of coconut shell soft tissue cellulose decreases, and the relative crystallinity increases.

[0025] (3) Using KOH and acetic acid solution to purify the cellulose of the soft tissue of the coconut shell outer layer is beneficial to the crystallinity of cellulose.

[0026] (4) The extraction method adopted in the present invention has a relatively high extraction yield for the cellulose of the coconut shell outer layer, but the extraction yield and crystallinity of the cellulose extracted from coffee shells are relatively low. This may be related to the hardness, composition and tissue morphology of coconut shells and coffee shells. Thus, it shows that the extraction method of the present invention is more suitable for extracting coconut shells. Description of the Drawings

[0027] Figure 1 It is a micrograph of unextracted coconut shell powder.

[0028] Figure 2 It is a micrograph of the coconut shell soft tissue cellulose extracted in Example 1 of the present invention. Detailed Description of the Invention

[0029] The content of the present invention will be further described in detail through specific examples below. The raw materials, reagents or devices used in the examples and comparative examples can be obtained from conventional commercial channels or can be obtained by existing technical methods without special instructions. Unless otherwise specified, the test or measurement methods are conventional methods in the art.

[0030] Example 1

[0031] This example provides a method for extracting coconut shell soft tissue cellulose. The specific process is as follows:

[0032] Step S1. Separation: Use a self-made vertical cyclone separator to separate and collect the soft tissue fibers of the coconut shell outer layer onto a vibrating screen with a mesh size larger than 40 meshes;

[0033] Step S2. Crushing: Place the soft tissue fibers of the coconut shell outer layer in a cryogenic crusher filled with liquid nitrogen for crushing and vibrating screening. The temperature of the cryogenic crusher is -50 °C, the rotation speed is 3000 rpm, and the vibrating screen is 400 meshes to obtain coconut shell powder;

[0034] Step S3. Extraction: Place the selected coconut shell powder in a forced-air drying oven at 105 °C and dry it to absolute dryness. Weigh 5 g and transfer it to a conical flask. Add 100 mL of distilled water, 10 mL of citric acid, and 2 g of sodium hypochlorite to it respectively, stir evenly, cover the conical flask, and place it in a constant-temperature water bath at 80 °C for 1 h. During the heating process, continuously stir the reactants to make the coconut shell powder mix evenly with distilled water, citric acid, and sodium hypochlorite. Repeat adding 100 mL of distilled water, 10 mL of citric acid, and 2 g of sodium hypochlorite every 1 h, and repeat this six times in total. Take out the conical flask from the water bath and cool it in an ice-water bath. After 1 h, filter it with a dry glass filter, and repeatedly wash the filter cake with distilled water until it is no longer acidic (pH ≈ 7). Filter the filter cake again with a suction filter and dry it.

[0035] Step S4. Purification: Soak the product obtained in S4 thoroughly with a 15% KOH aqueous solution for 15 min. Add an acetic acid aqueous solution with an equimolar amount to KOH to the soaking solution and react for 10 min. Then filter and rinse until neutral, filter by suction, and freeze-dry for 72 h to obtain coconut shell soft tissue cellulose powder.

[0036] Example 2

[0037] This example provides a method for extracting coconut shell soft tissue cellulose, and the specific process is as follows:

[0038] Step S1. Separation: Use a self-made vertical cyclone separator to separate the soft tissue fibers on the outer layer of the coconut shell and collect them on a vibrating sieve with a mesh size larger than 40 meshes;

[0039] Step S2. Crushing: Place the soft tissue fibers of the coconut shell outer shell in a cryogenic grinder filled with liquid nitrogen for crushing and vibrating screening. The temperature of the cryogenic grinder is -150 °C, the rotation speed is 5000 rpm, and the vibrating sieve is 300 meshes;

[0040] Step S3. Extraction: Place the selected coconut shell powder in a forced-air drying oven at 105 °C and dry it to absolute dryness. Weigh 5 g and transfer it to a conical flask. Add 100 mL of distilled water, 8 mL of glacial acetic acid, and 10 g of sodium hypochlorite to it respectively, stir evenly, cover the conical flask, and place it in a constant-temperature water bath at 80 °C for 1 h. During the heating process, continuously stir the reactants to make the coconut shell powder mix evenly with distilled water, glacial acetic acid, and sodium hypochlorite. Repeat adding 100 mL of distilled water, 8 mL of glacial acetic acid, and 10 g of sodium hypochlorite every 1 h, and repeat this six times in total. Take out the conical flask from the water bath and cool it in an ice-water bath. After 1 h, filter it with a dry glass filter, and repeatedly wash the filter cake with distilled water until it is no longer acidic (pH ≈ 7). Filter the filter cake again with a suction filter and dry it.

[0041] Step S4. Purification: Soak the product obtained in S4 with a 5% KOH aqueous solution for 5 minutes. Add an acetic acid aqueous solution with an equimolar amount to KOH to the soaking solution and react for 10 minutes. Then filter and rinse until neutral, perform suction filtration, and vacuum dry for 48 hours to obtain coconut shell soft tissue cellulose powder.

[0042] Example 3

[0043] This example provides a method for extracting coconut shell soft tissue cellulose, and the specific process is as follows:

[0044] Step S1. Separation: Use a self-made vertical cyclone separator to separate and collect the outer soft tissue fibers of the coconut shell onto a vibrating screen with a mesh size larger than 40;

[0045] Step S2. Crushing: Place the outer soft tissue fibers of the coconut shell in a cryogenic crusher filled with liquid nitrogen for crushing and vibrating screening. The temperature of the cryogenic crusher is -100°C, the rotation speed is 1000 rpm, and the vibrating screen is 80 mesh;

[0046] Step S3. Extraction: Place the screened coconut shell powder in a forced-air drying oven at 105°C and dry it to absolute dryness. Weigh 20 g and transfer it to a conical flask. Add 800 mL of distilled water, 10 mL of glacial acetic acid, and 10 g of sodium hypochlorite to it respectively, stir evenly, cover the conical flask, and place it in a constant-temperature water bath at 95°C and heat for 1 hour. During the heating process, continuously stir the reactants to make the coconut shell powder, distilled water, glacial acetic acid, and sodium hypochlorite mix evenly. Repeat adding 800 mL of distilled water, 10 mL of glacial acetic acid, and 10 g of sodium hypochlorite every 1 hour, and repeat a total of six times. Take out the conical flask from the water bath and put it in an ice-water bath to cool. After 1 hour, perform suction filtration with a dry glass filter, and repeatedly wash the filter cake with distilled water until it is no longer acidic (pH≈7). Put the filter cake into the suction filter again for suction filtration and drying.

[0047] Step S4. Purification: Soak the product obtained in S4 with a 10% KOH aqueous solution for 40 minutes. Add an acetic acid aqueous solution with an equimolar amount to KOH to the soaking solution and react for 10 minutes. Then filter and rinse until neutral, perform suction filtration, and far-infrared dry for 48 hours to obtain coconut shell soft tissue cellulose powder.

[0048] Example 4

[0049] This example provides a method for extracting coconut shell soft tissue cellulose, and the specific process is as follows:

[0050] Step S1. Separation: Use a self-made vertical cyclone separator to separate and collect the outer soft tissue fibers of the coconut shell onto a vibrating screen with a mesh size larger than 40;

[0051] Step S2. Crushing: Place the soft tissue fibers of the coconut shell outer layer in a cryogenic crusher filled with liquid nitrogen for crushing and vibrating screening. The temperature of the cryogenic crusher is -120°C, the rotation speed is 3000 rpm, and the vibrating screen is 400 mesh;

[0052] Step S3. Extraction: Place the screened coconut shell powder in a forced-air drying oven at 105°C and dry it to absolute dryness. Weigh 5 g and transfer it to a conical flask. Add 100 mL of distilled water, 10 mL of citric acid, and 2 g of sodium hypochlorite to it respectively, stir evenly, cover the conical flask, and place it in a constant-temperature water bath at 80°C for heating for 1 h. During the heating process, continuously stir the reactants to make the coconut shell powder mix evenly with the distilled water, citric acid, and sodium hypochlorite. Repeat adding 100 mL of distilled water, 10 mL of citric acid, and 2 g of sodium hypochlorite every 1 h, and repeat this six times in total. Take out the conical flask from the water bath and put it in an ice-water bath to cool. After 1 h, filter it with a dry glass filter, and repeatedly wash the filter cake with distilled water until it is no longer acidic (pH≈7). Put the filter cake into the suction filter again for filtration and drying.

[0053] Step S4. Purification: Fully soak the product obtained in S4 with a 15% KOH aqueous solution, soak it for 15 min, add an acetic acid aqueous solution with an equimolar amount to KOH to the soaking solution and react for 10 min, then filter and rinse until neutral, filter by suction, and freeze-dry for 72 h to obtain coconut shell soft tissue cellulose powder.

[0054] Example 5

[0055] This example provides a method for extracting coconut shell soft tissue cellulose. The specific process is as follows:

[0056] Step S1. Separation: Use a self-made vertical cyclone separator to separate the soft tissue fibers of the coconut shell outer layer and collect them on a vibrating screen with a mesh size larger than 40;

[0057] Step S2. Crushing: Place the soft tissue fibers of the coconut shell outer layer in a cryogenic crusher filled with liquid nitrogen for crushing and vibrating screening. The temperature of the cryogenic crusher is -150°C, the rotation speed is 1000 rpm, and the vibrating screen is 300 mesh;

[0058] Step S3. Extraction: Place the selected coconut shell powder in a forced-air drying oven at 105 °C and dry it to absolute dryness. Weigh 5 g and transfer it to a conical flask. Add 100 mL of distilled water, 8 mL of glacial acetic acid, and 10 g of sodium hypochlorite to it respectively. Stir evenly, cover the conical flask, and place it in a constant temperature water bath at 80 °C and heat for 1 h. During the heating process, continuously stir the reactants to make the coconut shell powder mix evenly with the distilled water, glacial acetic acid, and sodium hypochlorite. Repeat adding 100 mL of distilled water, 8 mL of glacial acetic acid, and 10 g of sodium hypochlorite every 1 h, and repeat a total of six times. Take out the conical flask from the water bath and put it in an ice-water bath to cool. After 1 h, filter it with a dry glass filter, and repeatedly wash the filter cake with distilled water until it is no longer acidic (pH ≈ 7). Filter the filter cake again with a suction filter and dry it.

[0059] Step S4. Purification: Soak the product obtained in S4 with a 5% KOH aqueous solution by mass for 5 min. Add an acetic acid aqueous solution with an equimolar amount to KOH to the soaking solution and react for 10 min. Then filter and rinse until neutral, filter with suction, and vacuum dry for 48 h to obtain coconut shell soft tissue cellulose powder.

[0060] Comparative Example 1

[0061] This comparative example provides a method for extracting coconut shell soft tissue cellulose, which is different from Example 5 in the temperature and rotation speed of the cryogenic grinder in Step S2. The specific process is as follows:

[0062] Step S1. Separation: Use a self-made vertical cyclone separator to separate and collect the outer soft tissue fibers of the coconut shell onto a vibrating screen with a mesh size larger than 40;

[0063] Step S2. Crushing: Place the outer soft tissue fibers of the coconut shell in a cryogenic grinder filled with liquid nitrogen for crushing and vibrating screening. The temperature of the cryogenic grinder is room temperature, the rotation speed is 500 rpm, and the vibrating screen is 300 mesh;

[0064] Step S3. Extraction: Place the selected coconut shell powder in a forced-air drying oven at 105 °C and dry it to absolute dryness. Weigh 5 g and transfer it to a conical flask. Add 100 mL of distilled water, 8 mL of glacial acetic acid, and 10 g of sodium hypochlorite to it respectively. Stir evenly, cover the conical flask, and place it in a constant temperature water bath at 80 °C and heat for 1 h. During the heating process, continuously stir the reactants to make the coconut shell powder mix evenly with the distilled water, glacial acetic acid, and sodium hypochlorite. Repeat adding 100 mL of distilled water, 8 mL of glacial acetic acid, and 10 g of sodium hypochlorite every 1 h, and repeat a total of six times. Take out the conical flask from the water bath and put it in an ice-water bath to cool. After 1 h, filter it with a dry glass filter, and repeatedly wash the filter cake with distilled water until it is no longer acidic (pH ≈ 7). Filter the filter cake again with a suction filter and dry it.

[0065] Step S4. Purification: The product obtained in S4 was fully soaked in an aqueous solution of 5% KOH by mass for 5 min. An aqueous acetic acid solution equimolar to KOH was added to the soaking solution and reacted for 10 min. Then, it was filtered and rinsed until neutral, suction filtered, and vacuum dried for 48 h to obtain coconut shell soft tissue cellulose powder.

[0066] Comparative Example 2

[0067] This comparative example provides a method for extracting coffee shell cellulose. The difference from Example 5 is that the coconut shell is replaced with a coffee shell. The specific process is as follows:

[0068] Step S1. Separation: The coffee shell fibers were separated and collected on a vibrating screen with a mesh size larger than 40 using a self-made vertical cyclone separator.

[0069] Step S2. Crushing: The coffee shell fibers were placed in a freeze crusher filled with liquid nitrogen for crushing and vibrating screening. The temperature of the freeze crusher was -150 °C, the rotation speed was 1000 rpm, and the vibrating screen had a mesh size of 300.

[0070] Step S3. Extraction: The screened coffee shell powder was dried to absolute dryness in a forced-air drying oven at 105 °C. 5 g was weighed and transferred to a conical flask. 100 mL of distilled water, 8 mL of glacial acetic acid, and 10 g of sodium hypochlorite were added thereto, and the mixture was stirred evenly. The conical flask was capped and placed in a constant temperature water bath at 80 °C and heated for 1 h. During the heating process, the reactants were continuously stirred to make the coffee shell powder mix evenly with the distilled water, glacial acetic acid, and sodium hypochlorite. Every 1 h, 100 mL of distilled water, 8 mL of glacial acetic acid, and 10 g of sodium hypochlorite were added repeatedly, and the addition was repeated a total of six times. The conical flask was taken out of the water bath and placed in an ice-water bath to cool. After 1 h, it was suction filtered with a dry glass filter, and the filter cake was repeatedly washed with distilled water until it was no longer acidic (pH ≈ 7). The filter cake was again placed in a suction filter for suction filtration and drying.

[0071] Step S4. Purification: The product obtained in S4 was fully soaked in an aqueous solution of 5% KOH by mass for 5 min. An aqueous acetic acid solution equimolar to KOH was added to the soaking solution and reacted for 10 min. Then, it was filtered and rinsed until neutral, suction filtered, and vacuum dried for 48 h to obtain coffee shell soft tissue cellulose powder.

[0072] Comparative Example 3

[0073] This comparative example provides a method for extracting coconut shell soft tissue cellulose. The difference from Example 5 is that sodium hypochlorite and acid were not added repeatedly. The specific process is as follows:

[0074] Step S1. Separation: The outer soft tissue fibers of the coconut shell were separated and collected on a vibrating screen with a mesh size larger than 40 using a self-made vertical cyclone separator.

[0075] Step S2. Crushing: Place the soft tissue fibers of the coconut shell outer layer into a cryogenic crusher filled with liquid nitrogen for crushing and vibrating screening. The temperature of the cryogenic crusher is -150°C, the rotation speed is 1000 rpm, and the vibrating screen is 300 mesh;

[0076] Step S3. Extraction: Place the screened coconut shell powder in a blast drying oven at 105°C and dry it to absolute dryness. Weigh 5 g and transfer it to a conical flask. Add 100 mL of distilled water, 8 mL of glacial acetic acid, and 10 g of sodium hypochlorite to it respectively, stir evenly, cover the conical flask, and place it in a constant temperature water bath at 80°C for heating for 1 h. During the heating process, continuously stir the reactants to make the coconut shell powder mix evenly with distilled water, glacial acetic acid, and sodium hypochlorite. Repeat adding 100 mL of distilled water every 1 h, and repeat a total of six times. Take out the conical flask from the water bath and put it into an ice-water bath for cooling. After 1 h, filter it with a dry glass filter, and repeatedly wash the filter cake with distilled water until it is no longer acidic (pH≈7). Put the filter cake into the suction filter again for suction filtration and drying.

[0077] Step S4. Purification: Fully soak the product obtained in S4 with a 5% KOH aqueous solution. The soaking time is 5 min. Add an acetic acid aqueous solution with an equimolar amount of KOH to the soaking solution and react for 10 min. Then filter and rinse until neutral, perform suction filtration, and vacuum dry for 48 h to obtain coconut shell soft tissue cellulose powder.

[0078] Comparative Example 4

[0079] This comparative example provides a method for extracting coconut shell soft tissue cellulose. The difference from Example 5 is that KOH and acetic acid solution are not used to purify the coconut shell. The specific process is as follows:

[0080] Step S1. Separation: Use a self-made vertical cyclone separator to separate the soft tissue fibers of the coconut shell outer layer and collect them on a vibrating screen with a mesh size larger than 40;

[0081] Step S2. Crushing: Place the soft tissue fibers of the coconut shell outer layer into a cryogenic crusher filled with liquid nitrogen for crushing and vibrating screening. The temperature of the cryogenic crusher is -150°C, the rotation speed is 1000 rpm, and the vibrating screen is 300 mesh;

[0082] Step S3. Extraction: Place the selected coconut shell powder in a forced-air drying oven at 105 °C and dry it to absolute dryness. Weigh 5 g and transfer it to a conical flask. Add 100 mL of distilled water, 8 mL of glacial acetic acid, and 10 g of sodium hypochlorite to it respectively. Stir evenly, cover the conical flask, and place it in a constant temperature water bath at 80 °C and heat for 1 h. During the heating process, continuously stir the reactants to make the coconut shell powder mix evenly with the distilled water, glacial acetic acid, and sodium hypochlorite. Repeat adding 100 mL of distilled water, 8 mL of glacial acetic acid, and 10 g of sodium hypochlorite every 1 h, and repeat a total of six times. Take out the conical flask from the water bath and cool it in an ice-water bath. After 1 h, filter it with a dry glass filter, and repeatedly wash the filter cake with distilled water until it is no longer acidic (pH ≈ 7). Filter the filter cake again with a suction filter and dry it to obtain coconut shell soft tissue cellulose powder.

[0083] Performance test of coconut shell soft tissue cellulose:

[0084] Crystallinity: Scan the coconut shell soft tissue cellulose with an X-ray diffractometer at a scanning speed of 2° / min and a scanning range of 10 - 80°, and calculate the crystallinity through the integral area.

[0085] Cellulose diameter: Place a small amount of cellulose on a glass slide and observe the diameter and morphology of the cellulose under a stereomicroscope with a 10X eyepiece.

[0086] Table 1. Performance test results of coconut shell soft tissue cellulose.

[0087] Sample Crystallinity (%) Yield (%) Cellulose diameter (μm) Example 1 56 32 53±15 Example 2 61 37 58±10 Example 3 64 43 230±50 Example 4 55 31 62±3 Example 5 60 38 55±20 Comparative Example 1 35 22 196±50 Comparative Example 2 32 20 80±10 Comparative Example 3 24 55 75±23 Comparative Example 4 27 32 53±16

[0088] By comparing Example 5 with Comparative Example 1, it can be found that at the temperature and rotation speed adopted in the present invention, coconut shell soft tissue cellulose with uniform size is obtained, and this temperature and rotation speed will not have a negative impact on the yield and crystallinity of cellulose.

[0089] By comparing Example 5 and Comparative Example 2, it can be found that the extraction method adopted in the present invention has a relatively high extraction yield for the cellulose of the coconut shell outer shell, but the extraction yields and crystallinities of the cellulose extracted from coffee shells are both relatively low. This may be related to the hardness, composition, and tissue morphology of coconut shells and coffee shells. Thus, it shows that the extraction method of the present invention is more suitable for extracting coconut shells.

[0090] By comparing Example 5 and Comparative Example 3, it can be found that as the number of repeated additions of sodium hypochlorite and acid increases, the yield of coconut shell soft tissue cellulose decreases, and the relative crystallinity increases.

[0091] By comparing Example 5 and Comparative Example 4, it can be found that using KOH and acetic acid solution to purify the coconut shell outer shell soft tissue cellulose is beneficial to improving the crystallinity of cellulose.

[0092] By comparing the attachedFigure 1 and attached Figure 2 It can be found that the average diameter of the unextracted coconut shell powder is coarser than that of the extracted coconut shell cellulose, and the surface is rougher due to crushing; after extraction, the apparent structure of the obtained cellulose becomes denser and smoother.

[0093] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A method for extracting coconut shell soft tissue cellulose, characterized in that: It includes the following steps: Step S1. Separation: Separate the outer soft tissue fibers of the coconut shell and sieve them. Step S2. Crushing: Crush the sieved outer soft tissue fibers of the coconut shell, the crushing temperature is -50 to -150 °C, and the crushing rotation speed is 1000 - 5000 rpm. Step S3. Extraction: Mix the crushed outer soft tissue fibers of the coconut shell, acid, sodium hypochlorite and water, heat and stir at 50 - 95 °C, then repeatedly add acid, sodium hypochlorite and water, and perform post-treatment. Step S4. Purification: Soak the product of Step S3 with a KOH solution, add an acetic acid solution to obtain coconut shell soft tissue cellulose. In Step S3, the dosage ratio of the outer soft tissue fibers of the coconut shell to acid and sodium hypochlorite is 5 - 20 g: 1 - 10 mL: 2 - 10 g. The acid is selected from at least one of citric acid and glacial acetic acid. In Step S4, the mass fraction of the KOH solution is 5 - 15%.

2. The method for extracting coconut shell soft tissue cellulose according to Claim 1, characterized in that: In Step S1, the sieve mesh for sieving is larger than 40 mesh.

3. The method for extracting coconut shell soft tissue cellulose according to Claim 1, characterized in that: The crushing in Step S2 is: Crush the sieved outer soft tissue fibers of the coconut shell, vibrate and sieve, the crushing temperature is -50 to -150 °C, the crushing rotation speed is 1000 - 5000 rpm, and the sieve mesh for sieving is 80 - 400 mesh.

4. The method for extracting coconut shell soft tissue cellulose according to Claim 1, characterized in that: The post-treatment is specifically filtration by suction, washing with water until neutral, filtration by suction, and drying.

5. The method for extracting coconut shell soft tissue cellulose according to Claim 1, characterized in that: The molar ratio of KOH to acetic acid is 1:

1.

6. The method for extracting coconut shell soft tissue cellulose according to Claim 1, characterized in that: In Step S4, the soaking time is 15 - 40 min.

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