A method for one-step extraction of bleached cellulose from cow dung

Abstract

The application discloses a method for one-step extraction of bleached cellulose from cow dung, and belongs to the technical field of cow dung-based paper pulp preparation. The one-step extraction method comprises the following steps: water washing is performed to remove excrement and impurities in the cow dung, thereby obtaining undigested plant fibers; the plant fibers are subjected to defatting and dewaxing; then, the plant fibers are added into a hydrogen peroxide solution containing activated carbon catalyst loaded with LaFeO3 perovskite for reaction, thereby obtaining cellulose. The application uses cow dung as raw material, attacks aromatic rings and ether bonds of lignin and glycosidic bonds of hemicellulose by using hydrogen peroxide, and additionally uses activated carbon catalyst loaded with perovskite to catalyze hydrogen peroxide, thereby enhancing the oxidation effect, and realizing the pulping and bleaching integrated technology by using cow dung as raw material. In the wastewater treatment stage, the wastewater generated by the one-step extraction and bleaching method only needs to be simply heated to be treated into normal water, and does not contain additional acid and alkali liquid, and the catalyst can be recycled and reused.

Description

Technical Field

[0001] This invention belongs to the field of cow dung-based pulp preparation technology, specifically relating to a one-step method for extracting bleached cellulose from cow dung. Background Technology

[0002] Currently, pulp is mainly sourced from natural plant resources, and different resource sources have a profound impact on paper strength, lifespan, and production processes. There are currently three main methods for pulp preparation: physical, chemical, and biological methods.

[0003] Physicochemical methods refer to the use of physical and mechanical behaviors such as high temperature, high pressure, and high shear to change the chemical composition and physical structure of substances. Currently, commonly used extraction processes include: ultrasonic-assisted extraction, steam explosion, and mechanical pulverization. (Zheng Xu) [1] When wheat straw was treated using steam explosion, the removal of hemicellulose was relatively good under the conditions of 1.8 MPa pressure and 6 min holding time, with 88.2% of hemicellulose removed. Steam explosion destroyed the original anti-degradation barrier of wheat straw, resulting in the degradation and removal of a large amount of hemicellulose in the material, the destruction of cell walls, the loosening of the resulting fiber bundle structure, and the increase of surface area. The crystallinity of the material increased from 57.4% to 63.4%, and the maximum decomposition rate temperature shifted towards higher temperatures, rising from 330.7℃ to 383.7℃.

[0004] Chemical methods, including acid treatment, alkali treatment, organic solvent treatment, and ionic liquid treatment, utilize various chemical reagents to treat cellulose-rich raw materials, separating or dissolving the cellulose for further extraction. (Wen Xu) [2] Six methods were used to extract cellulose from bagasse, and the cellulose content, yield, extraction time, and appearance were compared. The results showed that the nitric acid-ethanol-sulfuric acid method had the following advantages compared with the other five methods: (1) the extracted bagasse had the highest cellulose content, which was 84.68%; (2) the process was simple, with few steps and the shortest time, only 3.5 hours, which could greatly improve production efficiency; (3) the product had a good appearance, which was white and pollen-like; (4) the cost was low, and the experimental process required only conventional instruments and reagents, and the ethanol could be recycled.

[0005] Biological cellulose extraction refers to the process of extracting cellulose by decomposing lignin, hemicellulose, and pectin using various ligninases, hemicelluloseases, and pectinases. (Xu Shuying) [3]The effects of frequency and temperature in the ultrasonic pretreatment process on the degumming rate of banana stems were studied to determine the optimal ultrasonic pretreatment process. The results showed that the optimal ultrasonic frequency and temperature for pretreatment were 40 kHz and 70 ℃, respectively; and the optimal pH of the hemicellulase buffer and the optimal hemicellulase concentration for the enzymatic degumming process were 5.5 and 0.004 g·ml. -1 The reaction temperature was 50℃; the optimal pH of the pectinase buffer was 6.0, and the pectinase concentration was 0.003 g / ml. -1 The reaction temperature is 55℃.

[0006] References:

[0007] [1] Zheng Xu, Wang Huimei, Liu Zhong, et al. Steam explosion of wheat straw and characterization of its products [J]. Journal of Tianjin University of Science and Technology, 2020, 35(04):26-30.

[0008] [2] Wen Xu, Peng Siyao, Jiang Wenwei, et al. Comparative study on extraction methods of cellulose from bagasse [J]. New Chemical Materials, 2017, 45(09):250-252.

[0009] [3] Xu Shuying, Tan Wei, Zhang Yucang. Enzymatic degumming process of banana stems and its properties of degummed fibers [J]. Journal of Chemical Industry and Engineering (China), 2015, 66(09):3753-3761.

[0010] Currently, all pulping methods are researched specifically for biological raw materials, and the reagents used are mostly acids, alkalis, or organic solvents. While these methods are technically mature and effective, they generate wastewater and waste that pollute the environment, requiring additional wastewater and waste treatment. Mechanical methods, while not producing chemical pollution, are energy-intensive and have poor pulping results, making them unsuitable for large-scale implementation. Furthermore, none of the above methods can bleach the pulp, and the resulting pulp retains the original color of the raw materials. Summary of the Invention

[0011] The purpose of this invention is to provide a one-step method for extracting and bleaching cellulose from cow dung. Using cow dung as raw material, plant fibers are first extracted as raw material for cellulose production. The plant fibers are then degreased and dewaxed. Finally, a hydrogen peroxide solution containing a perovskite-supported activated carbon catalyst is used to extract and bleach the degreased and dewaxed raw material, yielding high-quality cellulose.

[0012] To achieve the above objectives, the present invention provides the following technical solution:

[0013] One of the technical solutions of this invention is to provide a method for one-step extraction of bleached cellulose from cow dung, comprising the following steps:

[0014] The cow dung is washed to remove feces and impurities, resulting in undigested plant fiber. The plant fiber is then degreased and dewaxed, and then added to a hydrogen peroxide solution containing an activated carbon catalyst supported on LaFeO3 perovskite to react and obtain cellulose.

[0015] The technical principle of this invention: LaFeO3 acts as a heterogeneous catalyst, promoting the decomposition of H2O2 into hydroxyl radicals (·OH) and other reactive oxygen species (such as superoxide radical ·O2) through the solid-liquid interface. - Using activated carbon as a support increases the accessibility of the catalyst's active sites. These reactive oxygen species attack the aromatic rings and ether bonds of lignin, causing them to oxidize and degrade into water-soluble small molecules, facilitating subsequent washing and removal. Simultaneously, they promote the cleavage of glycosidic bonds in hemicellulose, reducing the degree of polymerization and enhancing solubility, thus separating pure cellulose. During cellulose extraction, hydrogen peroxide can also eliminate the absorption of visible light by oxidizing the conjugated double bonds and phenolic structures in lignin residues, improving cellulose whiteness and achieving a bleaching effect.

[0016] Preferably, the degreasing and dewaxing specifically involves treating the plant fibers sequentially with petroleum ether and anhydrous ethanol.

[0017] Preferably, the preparation steps of the activated carbon catalyst supported on LaFeO3 perovskite include: adding activated carbon to the LaFeO3 perovskite dispersion to load the LaFeO3 perovskite onto the activated carbon.

[0018] More preferably, the activated carbon is acid-washed activated carbon.

[0019] Preferably, in the hydrogen peroxide solution containing the activated carbon catalyst supported on LaFeO3 perovskite, the mass fraction of hydrogen peroxide in the hydrogen peroxide solution is 10-20%, and the mass ratio of the activated carbon catalyst supported on LaFeO3 perovskite to hydrogen peroxide is 0.1:1-2.

[0020] Preferably, the mass ratio of the degreased and dewaxed plant fiber to the hydrogen peroxide solution containing the activated carbon catalyst supported on LaFeO3 perovskite is 1:15 to 20.

[0021] Preferably, the reaction temperature is 50–70°C and the reaction time is 0.5–1 h.

[0022] The second technical solution of the present invention provides a cellulose obtained by the above-described method of one-step extraction of bleached cellulose from cow dung.

[0023] The third technical solution of the present invention provides an application of the above-mentioned cellulose in papermaking.

[0024] The beneficial technical effects of the present invention are as follows:

[0025] This invention uses cow dung as raw material, utilizes hydrogen peroxide to attack the aromatic rings and ether bonds of lignin, as well as the glycosidic bonds of hemicellulose, and supplements it with a perovskite-supported activated carbon catalyst to catalyze hydrogen peroxide, thereby enhancing its oxidation effect and realizing an integrated pulping and bleaching technology using cow dung as raw material.

[0026] In the wastewater treatment stage, the wastewater generated by the one-step extraction bleaching method of the present invention only needs to be treated into normal water by simple heating, without any additional acid or alkali solutions. The catalyst can also be recycled and reused. The cellulose extraction bleaching method provided by the present invention is simple, safe, and environmentally friendly. Attached Figure Description

[0027] Figure 1 This is a process flow diagram for extracting bleached cellulose in Example 1 of the present invention.

[0028] Figure 2 The cellulose extracted in Example 1 and Comparative Example 1 of this invention.

[0029] Figure 3 This is a cross-sectional SEM image of the plant fiber used in Example 1 of the present invention.

[0030] Figure 4 This is a surface SEM image of the cellulose extracted in Example 1 of the present invention. Detailed Implementation

[0031] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention. It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the present invention.

[0032] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0033] Furthermore, regarding the numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, are also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0034] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar to or equivalent to those described herein may be used in the implementation or testing of this invention.

[0035] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0036] Unless otherwise specified, room temperature and normal temperature as used in this invention refer to temperatures ranging from 10 to 30°C.

[0037] The raw materials used in Example 1 and Comparative Example 1 of this invention are commercially available products, specifically processed cow dung plant fiber. The processing method is as follows: washing away feces and impurities from the cow dung to obtain undigested plant fiber, which is the raw material used in this invention.

[0038] Example 1

[0039] Extraction and bleaching methods for cellulose from cow dung plant fiber:

[0040] (1) First, dry the raw material in an oven at 105°C until it is completely dry (constant weight). Then, place it in a beaker and add petroleum ether at a mass ratio of raw material: petroleum ether = 1:10, ensuring that the petroleum ether fully wets the raw material. Place the beaker in an oil bath and heat it to 60°C. Stir continuously at this temperature for 1 hour to degrease. After degreasing, filter the material and add anhydrous ethanol to the filtered raw material until it is completely soaked. Let it stand for 24 hours, then place it in an oil bath and heat it to 60°C. Stir continuously at this temperature for 1 hour to dewax. After dewaxing, filter and wash away impurities, and dry it to completely dryness to obtain the pretreated raw material.

[0041] (2) Weigh an appropriate amount of activated carbon, ultrasonically clean it for 0.5 h, filter and dry it, then soak it in dilute nitric acid for 12 h, filter and clean it until neutral, and dry it at 100℃ for 12 h. Store the pretreated activated carbon in a dry place. Dissolve 2.60 g of La(NO3)3·6H2O and 2.43 g of Fe(NO3)3·9H2O in 40 mL of deionized water, solidify it at room temperature for 3 h, add 5 g of pretreated activated carbon, ultrasonically clean it for 2 h, let it stand for 12 h, filter and clean it, and dry it at 100℃ overnight to obtain the catalyst.

[0042] (3) According to the mass ratio of pretreated raw material to H2O2 solution containing catalyst = 1:15, the pretreated raw material obtained in step (1) was added to a 20 wt.% H2O2 solution containing catalyst prepared in step (2). The amount of catalyst added was 0.1 times the mass of hydrogen peroxide. The mixture was heated at 50°C for 0.5 h. The reaction was repeated twice under the above conditions. After the reaction was completed, the mixture was filtered by vacuum pump. The sample was washed with distilled water and anhydrous ethanol until neutral to obtain bleached cellulose.

[0043] The process flow diagram for extracting bleached cellulose in Example 1 of this invention is shown below. Figure 1 .

[0044] Comparative Example 1

[0045] Alkali treatment for extracting cellulose from cow manure plant fiber:

[0046] (1) The raw material pretreatment steps are the same as in Example 1.

[0047] (2) Prepare a 10 wt.% NaOH solution. Mix the two according to the mass ratio of pretreatment raw material: NaOH solution = 1:20. React at 60℃ for 1 h. After the reaction is completed, filter until neutral.

[0048] The cellulose extracted in Example 1 and Comparative Example 1 are shown below. Figure 2 The image shows cellulose extracted by alkaline treatment on the left and cellulose extracted by hydrogen peroxide catalytic extraction on the right.

[0049] like Figure 2 As shown, the pulp color of the alkali-treated pulp is almost identical to that of the cow dung raw material, indicating that under the same experimental conditions, the alkali-treated pulp has no bleaching ability at all. In contrast, the cellulose extracted by the one-step extraction bleaching method of this invention has high whiteness, excellent bleaching effect, and shorter fiber length, indicating that the one-step extraction oxidation method provided by this invention oxidizes the raw material.

[0050] The cross-sectional SEM image of the plant fiber used in Example 1 is shown below. Figure 3 The surface SEM image of the cellulose extracted in Example 1 is shown below. Figure 4 .

[0051] Figure 3 The results show that the undigested plant fibers in cow dung have a porous structure with a high specific surface area. The porous structure can effectively reduce the density, resulting in lightweight and high toughness. Figure 4 The results showed that after the lignin was destroyed, the cellulose was exposed and the overall surface was smooth, indicating that hydrogen peroxide successfully removed some of the lignin and hemicellulose. At the same time, residual plant features and some lignin that had not been removed could also be observed.

[0052] The cellulose content in the cellulose extracted in Example 1 and Comparative Example 1 was determined simultaneously using GB / T 2677.10.

[0053] The method is as follows: The sample is pulverized to 40-60 mesh, and 1-2 g of sample (accurate to 0.0001 g) is weighed and added to 100 mL of 2% HCl solution. The mixture is heated in a boiling water bath for 30 minutes with intermittent stirring. It is filtered through a glass frit crucible, washed with hot water until neutral, and then washed twice with ethanol. The residue after acid treatment is transferred to a beaker, and 100 mL of 2% NaOH solution is added. The mixture is heated in a boiling water bath for 30 minutes, filtered, and washed until neutral. The residue, along with the frit crucible, is dried in an oven at 105 °C to constant weight (the difference between two weighings ≤ 0.001 g). The residue is then placed in a muffle furnace and ignited at 550 °C for 4 hours, cooled, and weighed. The cellulose content is calculated using a formula.

[0054] The calculation results are as follows: the cellulose content of Example 1 is 57.15%, and the cellulose content of Comparative Example 1 is 45.12%.

[0055] The cellulose extracted in Example 1 and Comparative Example 1 were subjected to beating tests. The beating machine speed was set to 500 rpm. The cellulose obtained in Example 1 had a freeness of 43°SR after only 2 minutes of beating; under the same conditions, the fiber obtained in Comparative Example 1 had a freeness of 24°SR. This indicates that the cellulose extracted by the method provided by the present invention is more likely to form pulp with high freeness, and the conventional alkali treatment method is inferior to the method of the present invention.

[0056] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for one-step extraction of bleached cellulose from cow dung, characterized in that, The steps are as follows: The cow dung is washed to remove feces and impurities, resulting in undigested plant fiber. The plant fiber is then degreased and dewaxed, and then added to a hydrogen peroxide solution containing an activated carbon catalyst supported on LaFeO3 perovskite to react and obtain cellulose. The preparation steps of the activated carbon catalyst supported on LaFeO3 perovskite include: adding activated carbon to the LaFeO3 perovskite dispersion to load the LaFeO3 perovskite onto the activated carbon. The activated carbon is acid-washed activated carbon; In the hydrogen peroxide solution containing the activated carbon catalyst supported on LaFeO3 perovskite, the mass fraction of hydrogen peroxide in the hydrogen peroxide solution is 10-20%, and the mass ratio of the activated carbon catalyst supported on LaFeO3 perovskite to hydrogen peroxide is 0.1:1-2. The mass ratio of the degreased and dewaxed plant fiber to the hydrogen peroxide solution containing the activated carbon catalyst supported on LaFeO3 perovskite is 1:15~20.

2. The method for one-step extraction of bleached cellulose from cow dung according to claim 1, characterized in that, The degreasing and dewaxing process specifically involves treating the plant fibers sequentially with petroleum ether and anhydrous ethanol.

3. The method for one-step extraction of bleached cellulose from cow dung according to claim 1, characterized in that, The reaction is carried out at a temperature of 50-70°C for a time of 0.5-1 hour.

4. Cellulose extracted by a one-step extraction method of bleached cellulose from cow dung as raw material according to any one of claims 1 to 3.

5. The use of cellulose as described in claim 4 in papermaking.

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