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What is a desiccant and what is its principle of hygroscopicity?


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.


What are the main types of desiccant?


There are many types of desiccants. Currently, there are three typical desiccant products in the desiccant industry: silica gel, clay (ie, montmorillonite) and molecular sieves.


1) 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%.


2) Mineral desiccant - the appearance of the shape is a gray ball, which is most suitable for moisture absorption in an environment below 50 °C. When the temperature is higher than 50 ° C, the degree of "water release" of the clay is greater than the degree of "water absorption". But the advantage of clay is that it is cheap.


3) Molecular sieve desiccant - it is a desiccant product that is synthetic and has strong adsorption to water molecules. The pore size of the molecular sieve can be controlled by different processing processes, and it can adsorb other gases in addition to adsorbing moisture. At high temperatures above 230 ° C, water molecules are well accommodated. Advantages: strong adaptability. Disadvantages: low moisture absorption rate, poor environmental protection (non-degradable).