Silica gel is a highly active adsorbent material, which is an amorphous substance with a chemical formula of mSiO2·nH2O. It is insoluble in water and any solvent, non-toxic and tasteless, chemically stable, and does not react with any substance except strong alkali and hydrofluoric acid. Various types of silica gels have different microporous structures due to their different manufacturing methods. The chemical composition and physical structure of silica gel determine that it has many other similar materials that are difficult to replace: high adsorption performance, good thermal stability, chemical stability, and high mechanical strength.
Silica gel is classified according to its pore size: macroporous silica gel, coarse pore silica gel, B-type silica gel, and fine pore silica gel. Due to the different pore structure, their adsorption properties are different. The coarse pore silica gel has a higher adsorption amount in the case of high relative humidity, and the fine pore silica gel absorbs more than the coarse pore silica gel in the case of relatively low relative humidity, while the B type silica gel has a pore structure in the coarse and fine pores. Between silica gel, the amount of adsorption is also between coarse and fine pores. Macroporous silica gel is generally used as a catalyst carrier, a matting agent, a toothpaste abrasive, and the like. Therefore, different varieties should be selected according to different uses.
After the silica gel adsorbs moisture, it can be regenerated by exposure, baking, air drying, and the like.
The chemical composition of silica gel desiccant:
Silica gel desiccant - the main component is silica, which is purified from natural minerals into pellets or beads. As a desiccant, its microporous structure (average 2A.) has a good affinity for water molecules. The most suitable moisture absorption environment for silica gel is room temperature (20~32) and high humidity (60~90%), which can reduce the relative humidity of the environment to about 40%.
A desiccant is a water-removing agent that absorbs moisture from the atmosphere. Its drying principle is to physically adsorb water molecules in its own structure or chemically absorb water molecules and change its chemical structure to become another kind. substance.
Color-changing silica gel: commonly used to keep the instrument and balance dry. It turns red after water absorption. The failed silica gel can be used after drying and regeneration. The amine, NH3, O2, N2, etc. can be dried.