Silica Gel vs Calcium Chloride
Moisture significantly impacts damaging products, such as electronics, food, and pharmaceuticals. High humidity levels can cause items to degrade or damage, leading to costly losses. Therefore, it’s essential to have effective packaging solutions to protect products against moisture. This article will explore the differences between silica gel and calcium chloride moisture absorbers for different requirements.
What is Silica Gel?
Silica gel is a porous, granular substance made from silicon dioxide, and the desiccant’s high surface area allows it to adsorb water molecules. The moisture absorber comes in various sizes and shapes, including small desiccant packs, beads, and powder form and is typically white, orange or blue, which changes colour upon saturation.
Applications of Silica Gel
- Moisture control for products, including electronics, leather goods, clothing, shoes, and food packaging.
- Preserving documents and artefacts in archives, museums, and libraries from moisture damage.
- Industrial uses such as the drying and purification of gases and liquids, as well as the production of plastics, resins, and coatings.
- Protect products during transportation and storage by absorbing excess moisture and preventing damage.
- Used in dehumidifiers to reduce the humidity level in indoor spaces.
- Cat litter and other pet products as a moisture-absorbing component.
- Silica gel can preserve flowers and other organic materials by absorbing moisture and preventing decay.
What is Calcium Chloride?
Calcium chloride is a white, crystalline substance highly soluble in water and an effective moisture absorber due to its hygroscopic properties. Like silica gel, calcium chloride comes in different forms, including pellets, flakes, and powder. The desiccant can absorb moisture faster than silica gel, making it an excellent choice for quick-drying requirements. Calcium chloride can be mixed with polymer gelling agents and used as container desiccants as a packaging solution to prevent container rain during shipping across different regions and through climate changes.
Applications of Calcium Chloride
- De-icing agents on roads, sidewalks, and airport runways to melt snow and ice at low temperatures.
- Concrete accelerator to produce concrete, helping it to set and harden faster.
- Firm up fruits and vegetables, enhance the texture of the cheese and act as a coagulant in the production of tofu.
- Increase the density of drilling fluids, control dust on oil and gas drilling sites, and maintain the stability of shale formations during hydraulic fracturing.
- Paper and pulp manufacturing, wastewater treatment, and leather tanning.
- Treating hypocalcemia (low calcium levels) as a component of intravenous solutions.
- Remove impurities and improve the quality of drinking water.
How do Silica Gel and Calcium Chloride Work?
Both silica gel and calcium chloride adsorb moisture from the air. Unlike absorption, which is a physical process that involves the soaking up of one substance into another, adsorption is a chemical process in which molecules of one substance adhere to the surface of another. When air containing moisture comes into contact with the surface of the substance, the water molecules are attracted to the surface and held there by forces of attraction.
Silica gel consists of tiny pores with a large surface area, allowing water molecules to be adsorbed. The water molecules are then trapped inside the pores of the silica gel, preventing them from causing damage to the surrounding environment. Once the silica gel has adsorbed a certain amount of moisture, it becomes saturated and can no longer adsorb additional water molecules. At this point, the desiccant must be regenerated or replaced to continue its moisture-absorbing function. Regeneration of the moisture absorber typically involves heating the desiccant to a high temperature, which removes the moisture and restores the desiccant to its original dry state.
Calcium chloride is a hygroscopic salt that attracts water molecules through hygroscopy. When exposed to moist air, the desiccant absorbs water molecules through a physical process that involves dissolving the salt in the water it has attracted. This process is exothermic, which means that it releases heat. Therefore, calcium chloride can also be used as a de-icing agent, as the heat generated can help to melt ice and snow. Once calcium chloride has absorbed significant moisture, the container desiccant can no longer absorb additional water molecules and must be regenerated or replaced.
Absorption Capacity
Regarding absorption capacity, calcium chloride has a higher absorption rate. Under 25°C and 70% relative humidity, calcium chloride absorbs seven times more moisture than silica gel. The desiccant’s high solubility in water allows it to absorb moisture faster than silica gel. Calcium chloride can also absorb more water per unit of weight, making it a better choice for large-scale moisture control applications.
However, silica gel works better in low-humidity conditions, making it a better option for long-term moisture control and smaller packaging. It retains the moisture inside, then releases it back into the air when heated to temperatures of around 120°C to be used again.
Safety Concerns
Both silica gel and calcium chloride are generally safe to use but pose some risks. Silica gel can be harmful if ingested or inhaled; therefore, bulk desiccants should be kept away from children and pets. Calcium chloride can irritate the skin and eyes and release toxic fumes if exposed to high temperatures. Follow proper safety precautions when handling these substances, such as wearing gloves and a mask and keeping them out of reach of children and pets.
Cost Comparison
Silica gel is generally more expensive than calcium chloride but more effective in certain applications. For example, silica gel is used in moisture-sensitive electronic equipment, where small amounts of moisture can cause significant damage. Calcium chloride is often used in large-scale moisture control applications, such as industrial settings or construction sites. In these applications, the lower cost of calcium chloride makes it a more cost-effective option, especially when large amounts of moisture must be removed quickly.
Both silica gel and calcium chloride desiccant can be reused multiple times, which can help reduce their overall cost. Silica gel can be regenerated by heating it to a specific temperature, which drives off the moisture and restores its adsorption capabilities. Calcium chloride can be reused by dissolving it in water and then boiling off the water to recover the salt.
Environmental Impact
Silica gel is considered to be more environmentally friendly than calcium chloride because it is non-toxic and can be recycled, while calcium chloride can have negative impacts on soil and water quality if not disposed of properly
Conclusion
When choosing between silica gel and calcium chloride, the decision depends on a specific application. Calcium chloride is a fast-acting moisture absorber with a high absorption capacity and a good choice for large-scale moisture control applications. At the same time, silica gel is the better option for long-term moisture control, especially in low-humidity conditions such as preventing mould on shoes. Both silica gel and calcium chloride are effective moisture absorbers to meet different packaging requirements. Choosing the right moisture absorber protects valuable products from humidity damage.