Why Silica Gel Used as Desiccant?

Silica gel is an amorphous compound with large surface area, high surface activity and easy water absorption:

mSiO2 + nH2O = mSiO2.nH2O

It can be considered that H2SiO3 is locally generated, and H2SiO3 will be dehydrated only at high temperature:

H2SiO3 (high temperature) = H2O + SiO2

The reverse process is water absorption, that is, it is easy to absorb water at room temperature, so dehydration is difficult and requires high energy to dehydrate.