What Is Silica Gel? Structure, Applications & Environmental Impact
Silica gel is a form of silicon dioxide that is porous as well as amorphous. It consists of a framework of tridimensional and also irregular geometry of alternating silicon (Si) and oxygen (O) atoms with a scale of nanometer voids and pores. The voids of the silica gel structure may contain either liquid or gas, vaccum.
Manufacturers often put little packets of the gel as it is a desiccant or drying agent that helps to keep moisture from damaging certain food products and also commercial products. Silica gel is usually prepared by the process of acidification of a solution of a silicate (water glass).
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Properties of Silica Gel
Some of the properties of silica gel are given below.
The Molecular Weight of silica gel is 60.09 g/mol.
Its appearance is translucent solid.
The melting point of silica gel is 1200 °C.
The specific surface area of silica gel is 500-950 m2/g.
Its electrical resistivity is 1015 Ω-cm.
The chemical name for the silica gel is silicon dioxide and the formula is SiO2. The molecule of silicon dioxide consists of two-atom of oxygen and one atom of silicon. Oxygen and silicon are the most abundant materials. The crust of the earth is 59 percent silica.
Uses of Silica Gel
Some of the major uses of silica gel are mentioned below.
Desiccant
A desiccant is a hygroscopic material used for maintaining dryness. For manufacturers, the purpose of silica gel is to be used as a desiccant. Silica gel also serves to keep the relative humidity inside a system of satellite transmission waveguide as low as possible. In compressed air systems of any industry, silica gel is also used to dry the air. Where a bed of silica gel beads is made for the air from the compressor discharge to flow through it. The silica gel beads are used for adsorbing the amount of moisture present in the air and preventing it from damaging at the point of use of the compressed air due to condensation. A similar kind of system is used for drying the compressed air on railway locomotives.
Water filtration
Silica gel has water absorption properties because of this property it is used in domestic water filters. Some minerals that are dissolved in water can be absorbed by the surface structure of silica gel. Because of the lack of regulations for products of the filtrations of domestic water, no studies give validation to the manufacturer claims regarding the effectiveness of the filtration system of sorbent silica gel.
Humidity indicator
The silica gel changes its colour slowly whenever it is doped with an indicator of moisture as it transitions from the anhydrous state which is a dry state to the hydrated state that is a wet state.
Chemistry
Silica gel in chemistry is applied in chromatography as a stationary phase. This gel is also applied to glass, plastic sheets and aluminium for thin-layer chromatography. Silica gel is also bound to chelating covalently. These materials possess the ability to remove the metal ions selectively from aqueous solutions. Chelating groups are able to make bonds (covalent bonds) to polyamines. This can also be combined with alkali metals and it forms an M-SG reducing agent. Silicon dioxide is not expected to biodegrade in soil and water.
Silica gel side effects
Some of the side effects of silica gel if eaten in excessive amounts are listed below. Now see what happens if you eat silica gel.
If someone has eaten silica gel in large quantities it can cause dehydration. This may create irritation in the throat and nose.
Silica gel is non-toxic material but sometimes it is a choking hazard for young children. Hence it should be put away from the reach of children.
It can cause stomach pains, vomiting, constipation, and nausea. Medical attention should be taken if vomiting is repeatedly occurring or can't keep food down, experiencing stomach pains, having an intestinal obstruction etc.
If silica gel gets into our eyes, it might cause irritation. As a result, we must first rinse our eyes with lukewarm water.
Dust of crystalline silica is a cause of disease silicosis which is a lung disease.
Do you know?
However this is unique about silica gel in that it is not a gel, nor will it dissolve in most liquids. It has a tendency to absorb water and other liquids instead of dissolving in them.
If you add silica gel in water it will absorb water around up to 40% of its weight in water.
Conclusion
We must have seen silica gel crystals in the new packaging of products as it is put there to absorb moisture. Silica gel desiccant property is widely used by manufacturers. We get all the important information related to silica gel such as what is the use of silica gel and its side effects as well.
FAQs on Silica Gel in Chemistry: Properties, Uses, Types & FAQs
1. What exactly is silica gel and what is it made of?
Silica gel is a solid, porous substance made from silicon dioxide, the same compound found in sand. Despite its name, it's not a soft gel but a hard, granular material. Its structure is filled with millions of microscopic pores that can attract and hold water molecules, a process known as adsorption.
2. What are the main properties that make silica gel so useful?
The key properties of silica gel are:
- High Porosity: It has a vast internal surface area, allowing it to adsorb a large amount of water relative to its weight.
- Chemically Inert: It does not react with most other substances, making it safe to package with food, medicine, and electronics.
- Non-toxic and Non-flammable: It is safe to handle and use in various consumer products.
- Hygroscopic: It readily attracts and holds water molecules from the surrounding air, making it an excellent desiccant (drying agent).
3. What are the most common uses for silica gel in everyday life?
Silica gel is mainly used as a desiccant to prevent moisture damage. You can find small packets of it in:
- New shoe boxes and leather bags to prevent mould.
- Bottles of vitamins and medications to keep them dry and effective.
- Packaging for electronics like cameras and phones to protect against humidity.
- Museum display cases to preserve delicate artefacts.
4. Why do silica gel packets have a “Do Not Eat” warning if it's non-toxic?
While silica gel itself is non-toxic and chemically inert (meaning it passes through the body undigested), the warning is crucial for two reasons. Firstly, the packet and the beads are a serious choking hazard, especially for children and pets. Secondly, some types of indicating silica gel contain additives like cobalt chloride, which can be harmful if ingested.
5. How does silica gel actually work to remove moisture?
Silica gel works through a physical process called adsorption. The tiny pores on its surface create a strong attraction for water molecules in the air. These water molecules stick to the surface of the silica gel, effectively pulling them out of the atmosphere and trapping them. It acts like a powerful, microscopic sponge for water vapour.
6. What is the difference between the clear (white) and blue silica gel beads?
The clear or white beads are non-indicating silica gel. The blue beads are known as indicating silica gel. They are coated with cobalt chloride, a chemical that changes colour from blue to pink as it becomes saturated with moisture. This provides a visual signal that the gel needs to be replaced or regenerated.
7. Can you reuse silica gel packets once they have absorbed moisture?
Yes, most silica gel can be reused. This process is called regeneration. By gently heating the beads in an oven at a low temperature (around 120°C or 250°F) for a couple of hours, the adsorbed water is driven off. This restores the gel's ability to adsorb moisture, making it effective again.
8. How is silica gel different from activated charcoal, as both are used for adsorption?
While both are excellent adsorbents, they specialise in different things. Silica gel is hydrophilic, meaning it primarily adsorbs water and other polar substances, making it ideal as a desiccant. In contrast, activated charcoal is hydrophobic and has a non-polar surface, making it extremely effective at adsorbing organic impurities, odours, and non-polar substances from gases or liquids, which is why it's used in water and air filters.
