Silica Gel vs Calcium Chloride

Which One is the Better Moisture Absorber?

Moisture has a significant impact on damaging many 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. The two popular moisture absorbers are silica gel and calcium chloride. This article will explore the differences between these two 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. Silica gel is commonly used in food packaging, drying flowers, pharmaceuticals, logistics and electronics to protect goods against moisture damage.
The moisture absorber comes in various sizes and shapes, including small desiccant packs, beads, and powder. The desiccant is typically white, orange or light blue and changes colour upon saturation.

What is Calcium Chloride?

Calcium chloride is a white, crystalline substance highly soluble in water. The moisture absorber is commonly used in road de-icing, water treatment, and concrete settings. Calcium chloride is also an effective moisture absorber thanks 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.

How Do Silica Gel and Calcium Chloride Work?

Both silica gel and calcium chloride work by adsorbing 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 silica gel 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 adsorbed moisture and restores the material to its original dry state.

On the other hand, calcium chloride is a hygroscopic salt that attracts water molecules through hygroscopy. When exposed to moist air, the calcium chloride 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. As a result, 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

When it comes to 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, so the bulk desiccant 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 specific applications. For example, silica gel is often used in moisture-sensitive electronic equipment, where small amounts of moisture can cause significant damage. In this case, its moisture adsorption capabilities justify the higher cost of silica gel.

On the other hand, calcium chloride is often used in large-scale moisture control applications, such as industrial settings or construction sites. In these cases, the lower cost of calcium chloride makes it a more cost-effective option, especially when large amounts of moisture are required to 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 non-toxic and biodegradable, making it a better environmental choice. However, it is essential to dispose of it properly, as it can still pose a choking hazard if ingested.
On the other hand, calcium chloride is not biodegradable and can harm plants and animals if disposed of improperly and can also contribute to soil and water pollution if mishandled.

The Bottom Line

When choosing between silica gel and calcium chloride, the decision depends on specific requirements. Calcium chloride is a fast-acting moisture absorber with a high absorption capacity and a good choice for large-scale moisture control applications. Silica gel is the better option for long-term moisture control, especially in low-humidity conditions. Prevent mould on shoes using silica gel.
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.