The pharmaceutical, cosmetic, and food and beverage sectors all employ silica gel. The main purpose of silica gel is to protect the packaged contents from internal moisture by managing and/or decreasing the moisture level within the sealed packaging. Silica gel is a safe product since it is naturally non-corrosive and non-toxic. As a result, the US government has approved silica gel for use in food and medication packaging.
Because of
(1) its adsorption capabilities caused by Van der Waals interactions and
(2) capillary condensation at high humidity, Silica Gel is intended to manage moisture levels within packed items. Silica gel has an interconnected pore distribution and an amorphous microporous structure (3-60 angstrom). Through adsorption and capillary condensation, the linked hydrophilic pores generate a large surface area that draws and holds water. Silica gel works like a sponge, with millions of small holes that are all linked.
Silica gel is a kind of silicic acid that is made up of unevenly shaped and porous particles. Sodium silicate and sulphuric acid are the primary raw materials utilized in its manufacturing. These substances are designed to go through a chemical reaction that occurs under certain conditions. The end product is a hard, transparent substance comprised of amorphous silicate, which is pure silicon dioxide with a high SiO2 concentration.
To make the extremely porous substance, silica gel is broken down into granules, then washed, aged, and dried. The size and level of aggregation of the randomly connected spherical polymerized silicate particles (SiO2), as well as their surface chemistry, determine the characteristics of silica gels. To do this, silica gel makers modify the most significant physical properties such as pore size, porosity, and surface area by controlling the conditions of the washing, aging, and drying processes.
Except for strong alkaline chemicals and hydrofluoric acid, silica gel is inert and compatible with a wide range of compounds. Silica gel is odorless, non-toxic, and does not emit fumes or corrode metal. The internal surface of the silica gel particles is made up of a huge network of small holes that can attract and hold up to 36 percent of their own weight in moisture without losing their structure.
At temperatures below 25°C, silica gel is particularly efficient, but as temperatures increase, it loses some of its adsorption capability. A little quantity of water vapor will be absorbed in the interconnecting tiny pores even at very low humidity levels. The bigger pores will begin to fill as humidity rises. Because the adsorption force is smaller than that of molecular sieves (zeolite compounds), the adsorption capacity is decreased at low adsorbent concentrations (see chart below). Silica gel is highly effective at temperatures below 25°C, but as temperatures rise, it loses some of its adsorption capacity. Even at very low humidity levels, a little amount of water vapour will be absorbed in the interconnecting microscopic pores. As humidity rises, the larger pores will begin to fill. At low adsorbent concentrations, the adsorption capacity is reduced because the adsorption force is lower than that of molecular sieves (zeolite compounds) (see chart below).
The typical curves for water adsorption on silica gel and molecular sieves are shown in the graph below. It depicts the weight % absorbed in relation to the relative humidity in contact with the silica gel and the molecular sieve. The difference in the water vapour adsorption rates of silica gel and molecular sieves is demonstrated in the provided example (demo Graph).
The graph:
Desiccant bags and container inserts loaded with extremely active drying agents (even mixtures of silica gel and molecular sieves) provide an effective and ecologically acceptable option for moisture-sensitive product protection.
