TEMPO (2,2,6,6-Tetramethylpiperidine-1-oxyl) oxidation method used to prepare nanocellulose has many advantages, such as mild reaction conditions and high selective oxidation. However, it also has some disadvantages: 1. High cost: The cost of oxidants such as TEMPO and sodium hypochlorite (NaClO) is high, which limits large-scale industrial applications. 2. Environmental issues: Sodium hypochlorite and potassium hypochlorite used in the reaction are strong oxidants, which may cause pollution to the environment and require proper treatment of wastewater and by-products. 3. Complex control of reaction conditions: The reaction conditions of TEMPO oxidation method (such as pH, temperature, oxidant concentration, etc.) need to be strictly controlled, otherwise it may lead to excessive oxidation or insufficient oxidation of cellulose, thereby affecting the quality of the final product. 4. Long reaction time: In some cases, the TEMPO oxidation process may require

The preparation of carboxylated modified cellulose nanocrystals (CNCs) are usually improved by introducing carboxylic groups (-COOH). Common preparation methods include chemical oxidation and mechanical treatment methods. The following are several main methods: 1. TEMPO oxidation method • Principle: Use TEMPO (2,2,6,6-tetramethylpiperidine-1-oxygen free As a catalyst, the hydroxyl group on the cellulose surface is selectively oxidized to a carboxyl group in the presence of sodium hypochlorite (NaClO) and potassium hypochlorite (NaBr). • Steps: 1. Suspend the cellulose in water and add TEMPO, NaClO and NaBr. 2. Perform the oxidation reaction by controlling the pH value (usually between 10-11) and the temperature. 3. After the reaction is completed, the residual reagent is removed by dialysis or other means to obtain carboxylated cellulose nanocrystals. 2. Chloroacetic acid method • Principle: Use

Due to its unique physical and chemical properties, nanocellulose has broad application potential in the fields of adsorption and filtration materials. The following is an introduction to the application of nanocellulose in this field: 1. The nanoscale size and high specific surface area of ​​nanocellulose make it an ideal filter medium. Its applications include: Air filtration: Nanocellulose can be used to make high-efficiency air filter materials, which can capture fine particulate matter (PM2.5, PM10) and nanoparticles, and is widely used in air purifiers, masks and industrial dust removal equipment. Water filtration: In water filtration, nanocellulose can effectively remove suspended particles, microorganisms and some organic pollutants. Its high porosity and mechanical strength allow it to provide excellent filtration performance without significantly increasing flow resistance. 2. The adsorbent nanocellulose has rich surface hydroxyl groups, and various functional groups can be introduced through surface modification, so that they have excellent adsorption properties.

Nanocellulose agglomerates after freezing and is difficult to restore to gel state, mainly due to the following reasons: structural damage caused by moisture crystallization: During the freezing process, the moisture in the nanocellulose will form ice crystals. These ice crystals may squeeze or destroy the network of cellulose nanostructures, causing changes in the interaction between the fibers and destroy the original gel structure. Irreversible phase separation: When frozen, nanocellulose and solvents (water or other liquids) may be phase separation, and cellulose may form concentrated areas or flocculate. This phase separation is usually irreversible, and even after thawing, the nanocellulose is difficult to disperse evenly again, thus unable to restore the original gel state. Rearrangement of hydrogen bonds: The stability of nanocellulose gels is partially dependent on hydrogen bond interactions between cellulose chains. During the freeze-thawing process, the hydrogen bond network may be rearranged or enhanced, making the interaction between cellulose molecules stronger or closer.

Freezing nanocellulose (such as cellulose nanofibers or cellulose nanocrystals) usually agglomerate or form a condensed state, which may be caused by moisture crystallization and phase separation during the freezing process. To return to gel state, try the following: Gentle stirring: slowly thaw the frozen nanocellulose sample to room temperature, and then gently stir using a magnetic stirrer or other stirring device. Stirring helps to break the agglomerates and redisperse the cellulose nanostructures. Sonication: If the stirring is not enough to fully restore the gel state, ultrasonication can be used. Ultrasonic waves can effectively disperse nanocellulose and improve uniformity, but pay attention to controlling the processing time and power to avoid destroying the nanocellulose structure. High pressure homogenization: For more stubborn agglomeration, high pressure homogenization technology can be used. This method helps re-form the uniform gel by breaking the particles through a narrow nozzle at high pressure. Add a proper amount

The method of preparing nanocellulose dispersion into powder mainly involves removing solvents in the dispersion while retaining the structure and functionality of nanocellulose. Here are several common methods: 1. Lyophilization • Principle: Freeze-drying by quickly freezing the dispersion into solids, and then directly converting the moisture in the solids into water vapor through sublimation under low temperature and vacuum conditions, thereby Remove the solvent, leaving the dried powder behind. • Advantages: Freeze-drying can maintain the original form and structure of nanocellulose, prevent particles from agglomerating or structure collapse, and is suitable for thermally sensitive materials. • Steps: 1. Pour the nanocellulose dispersion into the tray of the freeze-dryer. 2. Quickly freeze the dispersion to low temperature (usually -40°C to -80°C). 3. Sublimate the moisture in a vacuum environment until a dry powder is obtained. 2. Spray drying

The price of nanocellulose varies greatly, and the main reasons can be attributed to the following aspects: 1. Source of raw materials: Source of natural cellulose: Nanocellulose can be extracted from a variety of natural resources, such as wood, agricultural waste, algae, etc. The prices and extraction difficulties of raw materials from different sources vary greatly, resulting in price differences in the final product. For example, wood cellulose is usually cheaper, while cellulose extracted from some rare plants may be more expensive. 2. Production process extraction and preparation method: The preparation process of nanocellulose (such as mechanical treatment, chemical treatment, biological enzymatic decomposition, etc.) has different complexity and different production costs. Chemical treatments may require expensive chemicals and strict environmental controls, while mechanical laws may consume more energy. Process efficiency and scale: The efficiency of the process, degree of automation, and production scale directly affect costs. Large-scale industrial production can often reduce costs through economies of scale

Sulfonated modified nanocellulose can form a chiral liquid crystal structure. Nanocellulose has natural chiral properties and is derived from the helical structure of cellulose molecular chains. Under certain conditions, especially at appropriate solution concentrations and pH values, nanocellulose can be self-assembled to form phases with chiral liquid crystal properties. Effect of sulfonation modification on the chiral liquid crystal structure Sulfonation modification refers to the introduction of sulfonic acid groups (-SO₃H) on the surface of nanocellulose. This modification will increase the negative charge on the surface of cellulose, thereby enhancing the nanocellulose in Dispersion and stability in solution. In addition, sulfonation modification may also affect the interaction forces of nanocellulose, including electrostatic repulsion and hydrogen bonding, which may affect the formation of the liquid crystal phase. Conditional concentration of chiral liquid crystal phase: When the concentration of nanocellulose in solution reaches a certain critical value, cellulose nanocrystals may spontaneously form chiral liquid due to their rigid and highly anisotropic morphology.

Nanocellulose has important application potential in the field of nanofluid research. Nanofluids refer to suspensions formed by uniformly dispersing nano-scale particles in base fluids (such as water, glycol, oil, etc.), and are often used in areas such as heat management, cooling, lubrication, and energy conversion. As a new type of nanomaterial, nanocellulose has its unique properties that make it show unique advantages in nanofluids. The following are the applications and characteristics of nanocellulose in nanofluid research: 1. Mechanism for enhanced thermal conductivity: Nanocellulose has high specific surface area and good thermal conductivity. When it is dispersed in the matrix fluid, the thermal conductivity of the fluid can be significantly improved, helping to enhance the thermal conductivity of the nanofluid. Application: In the fields of electronic equipment cooling, solar thermal conversion systems, automotive engine cooling, etc., nanocellulose-based nanofluids can effectively improve cooling efficiency. 2. Improve fluid flow mechanism: Nanocellulose has good

Dispersing nanocellulose in water usually takes several steps to ensure uniform dispersion and avoid agglomeration. The following are common dispersion methods: 1. Mechanical stirring steps: Add the nanocellulose powder directly to the water, and then stir using a high-speed stirrer. The stirring time and speed need to be adjusted according to the properties of the nanocellulose. Advantages: Simple and easy to use, suitable for small-scale preparation. Limitations: For nanocellulose with high concentrations or severe agglomeration, the effect may not be ideal. 2. Ultrasonic dispersion step: Use ultrasonic waves to crush the agglomerates of nanocellulose and disperse them in water. Usually, probe ultrasonic instruments are used, and the processing lasts for several minutes to more than ten minutes. Advantages: It can effectively disperse nanocellulose to obtain a uniform and stable dispersion. Limitations: Ultrasonic treatment may cause partial damage to the nanocellulose structure, so the ultrasonic time and power need to be controlled. 3. Steps to add dispersant: