Silica gel according to the size of its pore size is divided into: large pore silica gel, coarse pore silica gel, B-type silica gel, fine pore silica gel. Because of the different pore structure, so their adsorption performance has its own characteristics. Coarse pore silica gel has higher adsorption capacity under high relative humidity, fine pore silica gel has higher adsorption capacity than coarse pore silica gel under low relative humidity, while B-type silica gel has adsorption capacity between coarse and fine pore silica gel due to the pore structure. Macroporous silica gel is generally used as catalyst carrier, matting agent, toothpaste abrasive and so on. Therefore, different varieties should be selected according to different uses.
Silica gel adsorption of water, can be regenerated by exposure, baking, air drying and other methods.
Chemical composition of silica gel desiccant
Silica gel desiccant --- the main ingredient is silica, which is purified and processed from natural minerals into granular or bead-like. As a desiccant, its microporous structure (average 2A.) has a good affinity for water molecules. Silica gel is best suited for hygroscopic environments of room temperature (20~32) and high humidity (60~90%), and it can reduce the relative humidity of the environment to about 40%.
Desiccant is a kind of water remover that absorbs moisture from the atmosphere, and its drying principle is to adsorb water molecules in its own structure by physical means or to absorb water molecules by chemical means and change its chemical structure into another kind of substance.
Color-changing silica gel: commonly used to keep instruments and balances dry. It turns red when it absorbs water. Failed silica gel can be dried and regenerated for further use. Can dry amine, NH3, O2, N2, etc.