Silica Gel
Silicon dioxide (SiO₂)
Silica gel is a classic desiccant for dehumidifying the ambient air within packaging, for example of medicines and dietary supplements. It adsorbs moisture (water vapor) and binds it due to its large specific surface area. It is odorless and colorless and resistant to most substances, except hydrofluoric acid and strong alkalis.
Silica gel, silica gel or silica gel?
Industry-specific terminology.
As a desiccant, the English spelling silica gel has become established. Alternatively, the German spelling Silikagel is also used, for example in the chemical industry. In the pharmaceutical industry and in the laboratory sector, silica gel is also known by the term Kieselgel.
Important to know: It is the same material.
Properties of silica gel
Adsorption
Silica gel is an adsorbent, not to be confused with absorbent. Adsorption refers to the process in which molecules adhere to the surface of a solid without penetrating its structure. That's why silica gel retains its hard and noticeably dry state even when it is saturated.
Hygroscopicity
Silica gel is hygroscopic, which means it attracts water vapor. The water molecules are adsorbed from a relative ambient humidity of approx. 10% by the silanol groups located on the silica gel surface.
Water Absorption Capacity
The water absorption capacity of silica gel is strongly influenced by the manufacturing process and is typically between 30 and 40%. When used as a desiccant, it depends on the relative humidity of the environment.
Regeneration
Silica gel can be completely regenerated by heating to 120°C and is then ready to absorb again.
Silica gel orange - silica gel with color change
Silica gel orange is identical in function to white silica gel. However, it was produced with a dye that serves as an indicator to visualize saturation.
In the dry state, the silica gel has the color orange; when saturated with water vapor, it then changes its color (color change). The color change can be to green, violet, or white. For our desiccant products, we use a silica gel that changes to white.
It is used with transparent containers, or in semi-transparent bags or bags with viewing windows. This enables the condition to be assessed through a simple visual inspection and, if necessary, the desiccant to be replaced.
Difference to molecular sieve
The water absorption capacity is higher for silica gel than for molecular sieve and it increases with increasing relative humidity. However, silica gel only begins water vapor adsorption from approx. 10% relative humidity. It can be regenerated at significantly lower temperatures. In terms of price, silica gel offers a clear advantage compared to molecular sieve.
Especially in contact with pharmaceutical products, the highest quality and safety in application are essential. At ThoMar, you always receive the right desiccant with all necessary certificates, no matter what you choose.
Humidity regulator / humidity control
Furthermore, there are special types of silica-gel-based products known as humidity regulators or humidity control packs. They are used to protect products that require a certain moisture content. The desiccant must not dry out the product and must be able to absorb excess moisture. The silica gel is conditioned to the desired value for this purpose.