Preparation method and application of nanocellulose

Abstract

The invention relates to the technical field of nanocellulose, and discloses a preparation method and application of nanocellulose, cellulose is weighed and poured into a beaker, the beaker is placed in a constant-temperature water area of a constant-temperature magnetic stirrer, and an H2SO4 solution is slowly poured into the beaker; putting the fusiform rotor into a beaker, then starting a magnetic stirrer, stirring the suspension in the beaker, taking out the beaker after reaction, and adding deionized water for dilution to finish the reaction; centrifuging the diluted suspension at a rotating speed, pouring out supernate after centrifuging, and removing acid in the suspension; adding deionized water for repeated centrifugal washing until an upper solution obtained after centrifugation is turbid suspension, putting the suspension into a dialysis bag, and dialyzing in the deionized water until the pH value of dialysate is neutral; and taking out the liquid in the dialysis bag, centrifuging, taking the upper-layer suspension, and drying in a drying oven to obtain the nano cellulose. The nano cellulose solves the problems of high energy consumption and low efficiency of the existing cellulose preparation.

Description

Technical Field

[0001] The present invention relates to the technical field of nanocellulose, and in particular to a preparation method and application of nanocellulose. Background Art

[0002] With the acceleration of global industrialization, the annual output of the dye industry has exceeded 10 million tons, of which about 10%-15% of the dyes are discharged as wastewater during the production process, resulting in an additional 1 billion tons of dye wastewater worldwide each year. This type of wastewater has the following characteristics: (1) Chemical oxygen demand (COD) is as high as tens of thousands of mg / L, far exceeding the Class V standard for surface water (200 mg / L); (2) It contains a variety of aromatic compounds (such as azo dyes and anthraquinone dyes), of which 10%-30% have carcinogenic, teratogenic, and mutagenic effects; (3) The chromaticity generally exceeds 1000 times, seriously affecting the light transmittance of the water body; (4) It contains high concentrations of salt (such as NaCl up to 30 g / L), which aggravates the inhibitory effect of traditional biological treatment processes. my country's "Water Pollutant Discharge Standard for Textile Dyeing and Finishing Industry" (GB 4287-2012) stipulates that the chromaticity of directly discharged wastewater must be ≤40 times and the COD must be ≤80 mg / L, which poses a serious challenge to the treatment of dye wastewater.

[0003] Traditional dye wastewater treatment technologies have significant limitations: (1) Physical methods (such as coagulation and sedimentation, adsorption) have the risk of secondary pollution, and the energy consumption of activated carbon regeneration is as high as 2000-3000 kWh / ton; (2) Chemical methods (such as Fenton oxidation, ozone catalysis) require the addition of large amounts of hydrogen peroxide or ozone, increasing operating costs by 30%-50%; (3) Biological methods (such as activated sludge method) have a removal rate of less than 40% for difficult-to-degrade organic matter and are significantly inhibited by salinity. Nanomaterials have attracted attention due to their high specific surface area and functional groups, but existing nanocellulose preparation methods have three major bottlenecks: (a) Mechanical methods (such as high-speed shearing and high-pressure homogenization) have energy consumption of up to 150-200 kWh / ton, and the product diameter distribution is wide (20-200 nm); (b) Chemical methods (such as concentrated sulfuric acid hydrolysis) require reactions at -5°C, which increases equipment investment by 40% and produces a large amount of waste acid (H2SO4 residue >0.5%); (c) Biological methods (such as enzymatic hydrolysis) have a reaction cycle of up to 72 hours, which is difficult to meet the needs of industrial production.

[0004] Studies have shown that the microstructure of nanocellulose plays a decisive role in its performance: when the fiber diameter is <100 nm, the specific surface area can reach 150-200 m² / g, the hydroxyl functional group density increases to 1.2-1.5 mmol / g, and its adsorption capacity for cationic dyes is 3-5 times higher than that of micron-sized cellulose. However, existing industrial production still faces two major challenges: (1) the traditional acid hydrolysis method needs to be carried out at low temperature (-5°C) to inhibit the occurrence of side reactions, resulting in a 60%-80% increase in unit energy consumption; (2) the product purification process is complicated and requires multiple steps such as alcohol precipitation and dialysis, which keeps the total production cost at ￥2000-3000 / ton, restricting large-scale application. Therefore, the development of a low-temperature, efficient, low-cost, and environmentally friendly nanocellulose preparation process is of great significance to promoting the upgrading of dye wastewater treatment technology. Summary of the Invention

[0005] (1) Technical problems solved In view of the shortcomings of the existing technology, the present invention provides a preparation method and application of nanocellulose, which solves the problems of high energy consumption and low efficiency in the existing cellulose preparation.

[0006] (2) Technical solution To achieve the above object, the present invention provides the following technical solution: a method for preparing nanocellulose, comprising the following steps: (1) Weigh cellulose and pour it into a 200 mL beaker. Place the 200 mL beaker in the constant temperature water of a constant temperature magnetic stirrer and slowly pour 100 mL of 50 wt% H2SO4 solution into the beaker. (2) Place the shuttle rotor in the beaker, then start the magnetic stirrer to stir the suspension in the beaker. After the reaction, take out the beaker and add deionized water to dilute it 10 times to end the reaction; (3) Centrifuge the diluted suspension at 8000-8100 r / min. After centrifugation, discard the supernatant to remove the acid in the suspension. (4) Add deionized water and centrifuge repeatedly until the upper layer solution obtained after centrifugation is a turbid suspension. Place the suspension in a dialysis bag and dialyze it in deionized water. Replace the deionized water every 4-6 hours until the pH value of the dialysate is neutral. (5) The liquid in the dialysis bag was taken out and centrifuged at a speed of 8000 r / min. The upper suspension was taken and placed in an oven for drying to obtain nanocellulose.

[0007] Furthermore, the amount of cellulose in (1) is 1-1.2 g.

[0008] Furthermore, the temperature of the heating in (1) is 42-45°C.

[0009] Furthermore, the reaction time in (2) is 120-125 min.

[0010] Furthermore, the centrifugation time in (3) is 10-12 min.

[0011] Furthermore, the washing in (4) is performed 3-4 times.

[0012] Furthermore, the centrifugation time in (5) is 10-15 minutes.

[0013] Furthermore, the drying time in (5) is 1-2 hours.

[0014] Furthermore, the application of the method in dye wastewater treatment.

[0015] (3) Beneficial technical effects This method uses a sulfuric acid method to produce nanocellulose. The reaction proceeds under relatively mild conditions (42-45°C), avoiding the harsh conditions of high temperature and high pressure required in traditional preparation methods, significantly reducing energy consumption. The reaction time is controlled at 120-125 minutes, ensuring a full reaction while avoiding unnecessary energy waste.

[0016] The preparation process of the present invention ensures high purity and crystallinity of nanocellulose by precisely controlling reaction conditions and centrifugal washing steps. Specifically, the steps include multiple centrifugal washing and dialysis treatments, which effectively remove impurities and unreacted acid, resulting in a final product with high crystallinity and improved physical and chemical properties of the nanocellulose.

[0017] The prepared nanocellulose has a high specific surface area and abundant active groups, which gives it excellent adsorption properties in dye wastewater treatment. Experimental results show that the nanocellulose has a significant effect on dye wastewater treatment, effectively reducing the chromaticity and chemical oxygen demand of the wastewater. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is the infrared characterization image of nanocellulose. DETAILED DESCRIPTION

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention are clearly and completely described. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0020] In order to better understand the above technical solution, the above technical solution will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0021] Example 1 (1) Weigh 1 g of cellulose and pour it into a 200 mL beaker. Place the 200 mL beaker in a constant temperature water area of a constant temperature magnetic stirrer at 42°C. Slowly pour 100 mL of 50 wt% H2SO4 solution into the beaker. (2) Place the shuttle rotor in the beaker, then start the magnetic stirrer to stir the suspension in the beaker for 120 min. After the reaction, remove the beaker and add deionized water to dilute it 10 times to terminate the reaction. (3) Centrifuge the diluted suspension at 8000 rpm for 10 min. After centrifugation, discard the supernatant to remove the acid in the suspension. (4) Add deionized water and centrifuge repeatedly for 3 times until the upper layer solution obtained after centrifugation is a turbid suspension. Place the suspension in a dialysis bag and dialyze in deionized water. Replace the deionized water every 4 hours until the pH value of the dialysate is neutral. (5) The liquid in the dialysis bag was taken out and centrifuged at 8000 r / min for 10 min. The upper suspension was placed in an oven and dried for 1 h to obtain nanocellulose.

[0022] Example 2 (1) Weigh 1.2 g of cellulose and pour it into a 200 mL beaker. Place the 200 mL beaker in a constant temperature water area of a constant temperature magnetic stirrer heated to 45°C. Slowly pour 100 mL of 50 wt% H2SO4 solution into the beaker. (2) Place the shuttle rotor in the beaker, then start the magnetic stirrer to stir the suspension in the beaker for 125 min. After the reaction, remove the beaker and add deionized water to dilute it 10 times to terminate the reaction. (3) Centrifuge the diluted suspension at 8100 r / min for 12 min. After centrifugation, discard the supernatant to remove the acid in the suspension. (4) Add deionized water and centrifuge repeatedly for 4 times until the upper solution obtained after centrifugation is a turbid suspension. Place the suspension in a dialysis bag and dialyze in deionized water. Replace the deionized water every 6 hours until the pH value of the dialysate is neutral. (5) The liquid in the dialysis bag was taken out and centrifuged at 8000 r / min for 15 min. The upper suspension was placed in an oven and dried for 2 h to obtain nanocellulose.

[0023] Example 3 (1) Weigh 1.1 g of cellulose and pour it into a 200 mL beaker. Place the 200 mL beaker in a constant temperature water area of a constant temperature magnetic stirrer at 43°C. Slowly pour 100 mL of 50 wt% H2SO4 solution into the beaker. (2) Place the shuttle rotor in the beaker, then start the magnetic stirrer to stir the suspension in the beaker for 122 min. After the reaction, remove the beaker and add deionized water to dilute it 10 times to terminate the reaction. (3) Centrifuge the diluted suspension at 8050 r / min for 11 min. After centrifugation, discard the supernatant to remove the acid in the suspension. (4) Add deionized water and centrifuge repeatedly for 4 times until the upper layer solution obtained after centrifugation is a turbid suspension. Place the suspension in a dialysis bag and dialyze in deionized water. Replace the deionized water every 5 hours until the pH value of the dialysate is neutral. (5) The liquid in the dialysis bag was taken out and centrifuged at 8000 r / min for 12 min. The upper suspension was placed in an oven and dried for 2 h to obtain nanocellulose.

[0024] Example 4 (1) Weigh 1 g of cellulose and pour it into a 200 mL beaker. Place the 200 mL beaker in a constant temperature water area of a constant temperature magnetic stirrer at 42°C. Slowly pour 100 mL of 50 wt% H2SO4 solution into the beaker. (2) Place the shuttle rotor in the beaker, then start the magnetic stirrer to stir the suspension in the beaker for 120 min. After the reaction, remove the beaker and add deionized water to dilute it 10 times to terminate the reaction. (3) Centrifuge the diluted suspension at 8100 r / min for 12 min. After centrifugation, discard the supernatant to remove the acid in the suspension. (4) Add deionized water and centrifuge repeatedly for 4 times until the upper solution obtained after centrifugation is a turbid suspension. Place the suspension in a dialysis bag and dialyze in deionized water. Replace the deionized water every 6 hours until the pH value of the dialysate is neutral. (5) The liquid in the dialysis bag was taken out and centrifuged at 8000 r / min for 12 min. The upper suspension was placed in an oven and dried for 2 h to obtain nanocellulose.

[0025] Example 5 (1) Weigh 1.2 g of cellulose and pour it into a 200 mL beaker. Place the 200 mL beaker in a constant temperature water area of a constant temperature magnetic stirrer heated to 45°C. Slowly pour 100 mL of 50 wt% H2SO4 solution into the beaker. (2) Place the shuttle rotor in the beaker, then start the magnetic stirrer to stir the suspension in the beaker for 125 min. After the reaction, remove the beaker and add deionized water to dilute it 10 times to terminate the reaction. (3) Centrifuge the diluted suspension at 8050 r / min for 11 min. After centrifugation, discard the supernatant to remove the acid in the suspension. (4) Add deionized water and centrifuge repeatedly for 4 times until the upper layer solution obtained after centrifugation is a turbid suspension. Place the suspension in a dialysis bag and dialyze in deionized water. Replace the deionized water every 5 hours until the pH value of the dialysate is neutral. (5) The liquid in the dialysis bag was taken out and centrifuged at 8000 r / min for 10 min. The upper suspension was placed in an oven and dried for 1 h to obtain nanocellulose.

[0026] Example 6 (1) Weigh 1.1 g of cellulose and pour it into a 200 mL beaker. Place the 200 mL beaker in a constant temperature water area of a constant temperature magnetic stirrer at 43°C. Slowly pour 100 mL of 50 wt% H2SO4 solution into the beaker. (2) Place the shuttle rotor in the beaker, then start the magnetic stirrer to stir the suspension in the beaker for 122 min. After the reaction, remove the beaker and add deionized water to dilute it 10 times to terminate the reaction. (3) Centrifuge the diluted suspension at 8000 rpm for 10 min. After centrifugation, discard the supernatant to remove the acid in the suspension. (4) Add deionized water and centrifuge repeatedly for 4 times until the upper layer solution obtained after centrifugation is a turbid suspension. Place the suspension in a dialysis bag and dialyze in deionized water. Replace the deionized water every 5 hours until the pH value of the dialysate is neutral. (5) The liquid in the dialysis bag was taken out and centrifuged at 8000 r / min for 12 min. The upper suspension was placed in an oven and dried for 2 h to obtain nanocellulose.

[0027] Adsorption performance test Adsorbent dosage: 1 g / L, adsorption time 60 min, pH = 7; 25 °C.

[0028] Table 1: Adsorption performance test.

[0029] It can be seen from Table 1 that the nanocellulose of the present invention has a good removal effect on dye wastewater.

[0030] It should be noted that, in this document, the terms "comprise," "include," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or apparatus comprising a series of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus. In the absence of further limitations, an element defined by the phrase "comprises a ..." does not preclude the presence of other identical elements in the process, method, article, or apparatus comprising the element.

[0031] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

[0032] Those skilled in the art should understand that the above descriptions are only some specific embodiments of the present invention, rather than all embodiments.

Claims

1. A method for preparing nanocellulose, characterized in that: The following steps are involved: (1) Weigh cellulose and pour it into a 200 mL beaker. Place the 200 mL beaker in the constant temperature water of a constant temperature magnetic stirrer and slowly pour 100 mL of 50 wt% H2SO4 solution into the beaker. (2) Place the shuttle rotor in the beaker, then start the magnetic stirrer to stir the suspension in the beaker. After the reaction, take out the beaker and add deionized water to dilute it 10 times to end the reaction; (3) Centrifuge the diluted suspension at 8000-8100 r / min. After centrifugation, discard the supernatant to remove the acid in the suspension. (4) Add deionized water and centrifuge repeatedly until the upper layer solution obtained after centrifugation is a turbid suspension. Place the suspension in a dialysis bag and dialyze it in deionized water. Replace the deionized water every 4-6 hours until the pH value of the dialysate is neutral. (5) The liquid in the dialysis bag was taken out and centrifuged at a speed of 8000 r / min. The upper suspension was taken and placed in an oven for drying to obtain nanocellulose.

2. The method for preparing nanocellulose according to claim 1, wherein The amount of cellulose used in (1) is 1-1.2 g.

3. The method for preparing nanocellulose according to claim 1, wherein The temperature of the heating in (1) is 42-45°C.

4. The method for preparing nanocellulose according to claim 1, wherein The reaction time in (2) is 120-125 min.

5. The method for preparing nanocellulose according to claim 1, wherein The centrifugation time in (3) is 10-12 min.

6. The method for preparing nanocellulose according to claim 1, wherein Wash 3-4 times in the above (4).

7. The method for preparing nanocellulose according to claim 1, wherein The centrifugation time in (5) is 10-15 minutes.

8. The method for preparing nanocellulose according to claim 1, wherein The drying time in (5) is 1-2 hours.

9. A nanocellulose according to any one of claims 1 to 8, characterized in that The application in dye wastewater treatment.

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