Physical adsorption desiccant has silica gel, alumina gel, molecular sieve, activated charcoal, bone charcoal, charcoal, mineral desiccant, or activated white earth, etc., and its drying principle is to adsorb water molecules in its own structure through physical way.
Chemical adsorption desiccant classification: the first category of acidic desiccant, there are concentrated sulfuric acid, phosphorus pentoxide, anhydrous copper sulfate, etc., the second category of alkaline desiccant, there are solid caustic soda, lime and soda-lime (a mixture of sodium hydroxide and calcium oxide), etc., and the third category of neutral desiccant, such as anhydrous calcium chloride, anhydrous magnesium sulfate, etc..