Although some desiccants are chemically inert, others are extremely reactive and require specialized handling techniques. The most common desiccant is silica, an otherwise inert, nontoxic, water-insoluble white solid. Tens of thousands of tons are produced annually for this purpose.[1] Other common desiccants include activated charcoal, calcium sulfate, calcium chloride, and molecular sieves (typically, zeolites). Desiccants may also be categorized by their type, either I,II,III,IV, or V. These types are a function of the shape of the desiccant's moisture sorption isotherm.
1. Silica gel desiccant: The main ingredient of silica gel desiccant is porous form of silicon dioxide. An aqueous solution of sodium silicate is acidified to produce a gelatinous precipitate that is washed, then dehydrated to produce colorless silica gel. The average pore diameter is 20Å, and has a strong affinity for water molecules. Silica gel desiccant is good for working at temperature (20-30℃) and humidity environment (60-90%). It can reduce the humidity to 40%.
2.Clay desiccant: It's made of natural mineral. The final product can be granuar, powder, and spherical etc.
3. Molecular sieve desiccant: it's a synthetic product with high water affinity. It can work at low temperature (0-20℃) and low humidity environment (10-60%).
4.Desiccant sheet: a desiccant sheet is made of some natural fiber and chemicals. The advantage of desiccant sheet is that it only take a space for a sheet.