Nanocellulose is a kind of cellulose material with nanoscale size, and its preparation methods are various. These methods include mechanical methods, chemical methods, biological methods and electrospinning methods. These preparation methods have their own characteristics and can obtain nano-scale cellulose materials, which provides a rich choice for the application of nanotechnology and materials.

Preparation Methods of Nanocellulose

1、机械法(Mechanical method)

(1)高压均质法(High-pressure homogenization)：

The cellulose suspension is passed through a high-pressure homogenization device to disperse into nanoscale particles through a narrow channel under high-speed shear and collision. This method can effectively break up and disperse cellulose bundles, resulting in uniformly dispersed nanocellulose particles.

(2) High-energy ball milling (High-energy ball milling):

The cellulose was milled using a high-speed rotating ball mill pot and spheres. During the ball milling process, the high-speed rotation and collision of the spheres will generate strong shearing and impact forces, which will gradually break the cellulose into nano-sized particles.

2. Chemical method (Chemical method)

(1) Acid hydrolysis:

The cellulosic feedstock is hydrolyzed under acidic conditions. Strong acids, such as concentrated sulfuric acid or hydrochloric acid, are commonly used to break down the polymeric chains of cellulose into nanosized cellulose. The nanocellulose prepared by acid hydrolysis has high purity and crystallinity.

(2)酶解法(Enzymatic hydrolysis)：

Cellulose is hydrolyzed by cellulase. Cellulases are capable of hydrolyzing the β-1, 4-glycosidic bonds of cellulose, breaking it down into nanosized cellulose. The nanocellulose prepared by enzymatic hydrolysis is relatively mild and environmentally friendly, and can retain the crystalline characteristics of cellulose.

(3) Chemical oxidation method (Chemical oxidation):

The cellulose is treated with a chemical oxidizing agent, such as chromic acid oxide or hydrogen peroxide. The oxidizing agent is capable of oxidizing the hydroxyl and methyl groups of the cellulose, causing it to decompose into nanosized cellulose. Chemical oxidation can regulate the functional groups and surface properties of cellulose.

3、生物法(Biological method)

(1) Microbial fermentation (Microbial fermentation):

Nanocellulose is produced by a biosynthetic process using specific microorganisms such as acetic acid bacteria. The process of microbial synthesis of nanocellulose includes microbial culture, the expression of cellulose biosynthetic enzymes and the synthesis of cellulose. This method can control the structure and properties of cellulose by regulating microbial culture conditions and genetic engineering techniques.

(2) Biological tissue culture method (Biological tissue culture):

Nanocellulose is prepared by culturing and growing plant cells using plant tissue culture techniques. This method can regulate the morphology and structure of cellulose by controlling the medium composition and growth conditions.

4、电纺法(Electrospinning)

The cellulose solution or molten cellulose material is sprayed onto the receiver by a high voltage, and a fine nano-sized cellulose is formed under the action of a strong electric field. Nanocellulose prepared by electrospinning has the characteristics of high specific surface area and nano-scale size, and is suitable for textile and filtration fields.

With the continuous development and optimization of nanocellulose preparation methods, its application prospects in various fields have become broader. The special structure and properties of nanocellulose give it excellent mechanical strength, high specific surface area and biodegradability, which make it have great potential in the fields of textile, medicine, food, environment and energy.