Technology for preparing nano cellulose from waste cotton fabric

Abstract

The invention belongs to the field of renewable resource utilization, and particularly relates to development and utilization of a technology for preparing nano cellulose from waste cotton fabrics, which is hopeful to produce CNCs from high-cellulose-content and high-purity raw materials through a simple process.

Description

Technical Field

[0001] This invention belongs to the field of renewable resource utilization, and specifically relates to the development and utilization of a technology for preparing nanocellulose from waste cotton fabrics. Background Technology

[0002] Currently, a large amount of waste textiles is rapidly accumulating, and there is a lack of effective treatment and recycling methods. Therefore, the reuse of waste cotton textiles effectively alleviates the resource waste and environmental pollution caused by traditional landfill and incineration methods. Converting waste cotton textiles into... Cellulose nanoparticles (CNCs) It is not only environmentally friendly, but also helps to realize the recycling of cotton fiber, a high-value product.

[0003] Researchers have focused extensively on methods for extracting CNCs from various raw materials, such as microcrystalline cellulose, wood, cotton, agricultural waste, and other lignocellulosic biomass. Using concentrated sulfuric acid hydrolysis, the yield of CNCs from various cellulose materials is approximately 30-70%. This yield variation is mainly determined by the properties of the raw materials and the hydrolysis process parameters. Lower yields and more complex processing methods increase production costs and hinder practical applications. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the aforementioned background technology and to produce CNCs from raw materials with high cellulose content and high purity through a simple process. Cotton fiber, as the purest form of natural cellulose, can achieve a cellulose content of over 99% in cotton fabrics after fine washing and bleaching, thus meeting the production requirements of CNCs.

[0005] Cellulose nanomaterials are nanomaterials with unique physicochemical properties, including nanoscale size, lightweight, high strength, abundant surface groups, and excellent thermal stability. They are generally classified into two categories: cellulose nanocrystals (CNCs) and cellulose nanofibers (CNFs). CNCs are typically rod-shaped or whisker-like, with a width of 3-50 nm and a length between 50-500 nm; while CNFs are fibrous, with a width of 5-60 nm and a length extending from 50 nm to several micrometers. The choice of preparation method and the properties of the raw materials directly affect the structure and properties of cellulose nanomaterials.

[0006] Generally, CNCs are obtained through acid hydrolysis, a process that removes amorphous regions while retaining crystalline regions. In contrast, CNFs are primarily prepared by mechanical methods. Currently, various processes for preparing CNCs have been developed, including methods using organic acids, solid acids, and mixed acids, but concentrated sulfuric acid hydrolysis remains the most common, effective, and promising method for large-scale production.

[0007] The present invention will be further described in detail below with reference to embodiments, but these embodiments should not be construed as limiting the present invention. Example

[0008] In the process of preparing CNCs by acid hydrolysis of waste cotton fabrics, the waste cotton fabrics first undergo rigorous pretreatment; this includes thorough washing and drying to ensure that the cotton fabrics are free of any external impurities or moisture. After these steps, the cotton fabrics are cut into regular 2 cm × 2 cm pieces, which facilitates subsequent processing. Example

[0009] Next, these waste cotton fabric fragments were mixed with a 56% sulfuric acid solution at a solid-liquid ratio of 1:20 (w / v). During the mixing process, sufficient contact between the solution and the cotton fabric fragments was ensured to promote the hydrolysis reaction. The mixed sample was then transferred to a constant-temperature water bath and heated to accelerate the reaction rate and improve the reaction efficiency. When the reaction reached the predetermined endpoint, it was necessary to quickly terminate the reaction to prevent over-hydrolysis. For this purpose, 10 times the volume of deionized water was added, which not only diluted the reaction system but also neutralized the residual acidic substances. Example

[0010] Next, in order to separate the nanocrystals from the reaction mixture, multiple centrifugation processes were performed; after each centrifugation, cotton fiber residue and other large particulate impurities in the supernatant were removed, and a uniform milky white suspension was finally obtained. Example

[0011] To further purify and concentrate the CNCs, the suspension was transferred to a dialysis bag with a molecular weight of 10,000 and dialyzed for 48 hours under neutral pH conditions; this step helps to remove low molecular weight impurities and ions from the suspension. Example

[0012] After dialysis, the suspension was sonicated to ensure uniform dispersion of the CNCs; ultrasound can effectively break up agglomerated and aggregated nanocrystals, thereby making them more uniformly dispersed. Example

[0013] Finally, the water in the suspension was evaporated by vacuum freeze-drying technology to obtain dry powder of CNCs; this powder form of CNCs has good stability and storability.

[0014] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

[0015] The contents not described in detail in this invention are existing technologies known to those skilled in the art.

Claims

1. A technology for preparing nanocellulose from waste cotton fabrics, characterized in that... The waste cotton textiles mentioned above must first be thoroughly cleaned and dried to ensure that the cotton fabrics are free of any external impurities or moisture, and then crushed for later use.

2. The waste cotton fabric fragments described in claim 1 are mixed with a 56% sulfuric acid solution at a solid-liquid ratio of 1:20 (w / v). During the mixing process, it is necessary to ensure that the solution and the cotton fabric fragments are in full contact to promote the hydrolysis reaction. Heating treatment is also performed to accelerate the reaction rate and improve the reaction efficiency.

3. According to claims 1 and 2, when the reaction reaches the predetermined endpoint, the reaction needs to be terminated quickly to prevent excessive hydrolysis, and 10 times the volume of deionized water should be added.

4. According to claims 1, 2, and 3, the mixture needs to be centrifuged multiple times. After each centrifugation, cotton fiber residue and other large particulate impurities in the supernatant are removed, and a uniform milky white suspension is finally obtained.

5. According to claims 1, 2, 3, and 4, in order to further purify and concentrate the CNCs, the suspension was transferred to a dialysis bag with a molecular weight of 10,000 and dialyzed for 48 hours under neutral pH conditions; this helps to remove low molecular weight impurities and ions from the suspension.

6. According to claims 1, 2, 3, 4, and 5, after dialysis, in order to ensure the uniform dispersion of CNCs, the suspension was subjected to ultrasonic treatment to make its dispersion more uniform.

7. According to claims 1, 2, 3, 4, 5, and 6, the water in the suspension is evaporated by vacuum freeze-drying technology to obtain dried powder of CNCs.