The difference between a physical desiccant and a chemical desiccant



The principle of physical desiccant is to physically adsorb water molecules in their internal pore structure; the principle of chemical desiccant is to chemically absorb water molecules and change their chemical structure to become another substance.
Example 1: Silica gel desiccant is a physical desiccant. Silica gel desiccant is usually prepared by reacting sodium silicate and sulfuric acid, and undergoing a series of post-treatment processes such as aging and acid foam. Silica gel desiccant is an amorphous material. Its shape is generally colorless, blue and orange transparent bead-shaped particles. There are many pores extending in all directions. The principle of moisture absorption is to use these pores to adsorb water molecules in the air to its structure. in.
There are two common silicone desiccants:
1, fine pore silica gel desiccant:
The product has a white, translucent glass body. It is mainly used for drying and moisture proof, and can be used as a catalyst carrier and dehydration purification of organic compounds. Because of its high bulk density and low humidity, the moisture absorption effect is obvious. It can be used as an air purifier to remove moisture from the air to control the humidity of the air. It is also widely used in shipping, and it can also be used as dehumidification between two parallel sealing glass plates to maintain the transparency of the glass.
2, coarse pore silica gel desiccant:
The appearance of the product is white, and there are three types of blocks, spheres and microspheres. The moisture absorption effect is more significant in the environment with higher relative humidity. It is commonly used as a dehydrating agent and a desiccant, a catalyst carrier, and can remove organic acids and water in the transformer insulating oil. In addition, due to its large pore size, it is also a raw material for deep processing of silica gel.
Example 2: The quicklime desiccant is a chemical desiccant. The main component of the quicklime desiccant is calcium oxide. It is usually made by natural rock with the main component of calcium carbonate. When calcined at high temperature, it can be decomposed to form carbon dioxide and calcium oxide. . Its water absorption capacity is achieved by a chemical reaction (CaO+H2O====Ca(OH)2), which becomes another chemical substance after water absorption, so it is a chemical desiccant. The quicklime desiccant absorbs water irreversibly. Regardless of the humidity of the external environment, it can maintain a moisture absorption capacity of more than 35% of its own weight, is more suitable for low temperature storage, has excellent drying and moisture absorption effect, and the price is also low, but in recent years, the accident of the lime desiccant explosion injured the child This has occurred, so this desiccant has gradually been eliminated.