Reusing Desiccants in Packaging: Sustainable Moisture Solutions

Desiccants are vital drying agents used for preservation and moisture control in many industries, including packaging and manufacturing. They’re substances or chemicals that adsorb or absorb and attract moisture from the air, resulting in desiccation (dryness) in the surrounding atmosphere. Some examples of desiccants are natural desiccants like silica beads, activated charcoal, and bentonite clay or chemical desiccants like calcium oxide and molecular sieve, which each working in their own unique ways.

Desiccants are used to prevent humidity damage and mould growth and extend product life by creating drier environments. For example, in the food industry, a box of new vitamins frequently contains a small mesh bag of silica beads labelled “Desiccant, Do Not Eat.” But did you know that most desiccants are reusable?

The shelf life of desiccants is determined by the packaging environment in which they are used. However, most desiccants have a shelf life of one to three years and can also be reused upon regenerating them. Reusing desiccants reduces waste and provides an economical alternative to frequent replacements.

But how do you do this? This guide will share the process of regenerating numerous popular desiccants, as well as signs that your desiccants need rejuvenation.

Types of Commonly Used Desiccants

Desiccants are crucial in numerous industries, providing essential moisture control for various applications. Certain desiccants have gained prominence among the various options available due to their efficacy and versatility, including:

• Silica gel: A porous form of silicon dioxide that’s most frequently shaped into beads and placed in small packets that can be tucked within the packaging of electronics and certain food products. Silica gel’s remarkable ability to adsorb up to 40% of its weight in water and its non-toxic and non-flammable properties make it ideal for prolonging the shelf life and maintaining the quality of products.
• Clay desiccants: Primarily derived from bentonite clay, they’re natural desiccants renowned for their broad applications. They’re often the go-to solution for bulk applications, particularly shipping containers. Notably, clay desiccants protect machinery, metals, and electronics from the corroding effects of moisture. With an adsorption capacity of approximately 30% of their dry weight and effectiveness up to 120°F (50°C) under certain conditions, they serve as reliable moisture combatants.
• Activated carbon: This desiccant’s primary strength lies in adsorbing organic compounds and neutralizing odours. Composed of processed carbon with small, low-volume pores, it has a large surface area that’s amplified to enhance its ability to purify environments, control moisture, and eradicate pollutants and unpleasant smells.
• Molecular sieves: These desiccants are crystalline aluminosilicates with consistent pore structures, ideal for drying gases and liquids. Their stellar performance is characterized by their ability to lower water content to levels below 1 ppm. Their efficacy, even at diminished humidity levels, further cements their use in high-end industrial applications, such as drying hydrocarbon streams and natural gas processing.
• Activated alumina: This desiccant consists of a highly porous form of aluminium oxide, which finds its niche in air-drying systems. It’s also instrumental in purifying drinking water by eliminating fluoride. Activated alumina’s high absorption abilities, complemented by its effectiveness over a diverse temperature spectrum, ensure its continued usage across various industries.

Signs That a Desiccant Needs Rejuvenation

As valuable as desiccants are for moisture control, their effectiveness diminishes over time – particularly with prolonged exposure to moisture. However, you can regenerate and reuse silica gel and other desiccants.

Recognising when a desiccant needs rejuvenation is the first step. Here are the primary signs:

• Changes in appearance or texture: Fresh silica gel beads are often clear or have a specific colour, depending on their type. Over time and with moisture adsorption, they can turn pink or green and appear cloudy. In comparison, clay desiccants might become lumpy or change from their usual dry, powdery texture to a wetter, muddier consistency.
• Reduced adsorption or absorption efficiency: Over time, a desiccant might not absorb moisture as effectively as it first did. The desiccant’s adsorption or absorption efficiency can be tested by placing it in a high-humidity environment and observing its performance over a set period. If items stored with the desiccant show signs of moisture damage, mould growth, or corrosion, it likely needs rejuvenation.
• Weight gain in desiccants: As desiccants absorb moisture, they gain weight. One can determine a desiccant’s moisture content by periodically weighing and comparing it to its initial weight. A significant increase in weight indicates higher saturation and a need for rejuvenation. For example, silica gel can typically absorb up to 40% of its weight before it requires regeneration.

How To Rejuvenate Different Desiccants

The value of desiccants in maintaining an optimal environment is undeniable. Over time, these desiccants do lose their efficacy. However, with proper rejuvenation techniques, many types of desiccants can be returned to their original state, ready for reuse.

1. Oven-Drying Silica Gel

Silica gel is a moisture-adsorbing desiccant commonly used in the healthcare and electronics industries. It’s made up of oxygen and silicon atoms with nanometer-sized voids that result in a high surface area with many microscopic pores. Adsorption – not absorption – is when water in the air is adsorbed and condenses between these microscopic pores. In the case of silica gel, the moisture turns into liquid through the process of capillary condensation. This is why, even when saturated, silica gel feels dry to the touch.

However, when this desiccant adsorbs moisture, it transitions from active to inactive. When this occurs, it must be reactivated before it can be used again. Silica gel’s distinctive trait of changing colour when saturated makes judging when it requires rejuvenation a straightforward process.

Restoring silica gel for reuse is also relatively easy and safe. To restore silica gel’s drying capability:

1. Spread the silica gel beads on a baking tray, ensuring they’re in a single layer.
2. Preheat your oven to 250°F (120°C) and place the tray inside.
3. Bake for 3–5 hours, periodically checking for a colour change (typically from pink to blue or transparent, depending on the type).
4. For silica gel packets, you want to ensure the packet material is oven-safe or bake the packets at a lower heat (120°F or 50°C) for longer. You should also check back frequently to ensure the packets aren’t melting or burning. You can also leave silica gel packets in the sun for a day to dry them.
5. Once dried, store silica beads or packets immediately in an airtight container to prevent moisture adsorption.

You can also purchase a specialised desiccant reactivation unit to restore large quantities of silica gel.

2. Refreshing Molecular Sieve

Molecular sieve is used for dehydrating, purifying, and separating specific gases and liquids. It’s widely used in filtration systems to reduce humidity levels, as it can absorb up to 22% of its weight and withstand temperatures as high as 300°C.

Molecular sieve typically comes in spheres composed of synthetic zeolites, such as sodium, potassium, or calcium aluminosilicates. Zeolites are composed of hydrated metal aluminosilicates with crystalline microporous tunnel-like structures of silica and alumina tetrahedra. The uniformity and small size of the pores allow molecular sieve to effectively filter molecules based on shape and size.

Due to its effective water adsorption – the process of adhesions of particles to the surface of a material as opposed to the particle’s absorption into the material – from carrier gas or samples, molecular sieve will not work as well as it did the first time, requiring regeneration after a single use. Molecular sieves can also be trickier to regenerate due to their high affinity for water.

Molecular sieve needs to be activated using heat prior to use. It’s also more complex to regenerate molecular sieve, as the process requires exposure to vacuum or gas at high heat. However, it is possible to heat it to remove excess moisture, especially if it has been used mainly as a desiccant for water, not to separate gas.

To activate or regenerate molecular sieves used for water adsorption, you can:

1. Place them in an oven set to 350–600°F (175–320°C).
2. Place the molecular sieves in a heat-resistant container. Ensure that the container is large enough to allow for proper air circulation.
3. Heat for 1–2 hours at higher temperatures or longer (several hours) at lower temperatures.
4. Allow it to cool in a sealed environment to prevent immediate moisture uptake.
5. Store in an airtight, dry, and moisture-free container.

Other methods for regenerating molecular sieves include:

• Pressure change (oxygen concentrators)
• Heating and purging with a carrier gas (ethanol dehydration)
• Heating under a high vacuum

However, you’re unlikely to be able to achieve these methods at home or work, as you need specialised equipment, such as a furnace with a controlled atmosphere and precise temperature control. You can consider employing a company that offers molecular sieve regeneration or recycling services to do it for you.

3. Rejuvenating Activated Alumina

Activated alumina is used in various heavy industrial applications, including catalyst adsorption and fluoride removal. The desiccant is made from aluminium oxide and has a surface area greater than 200m2g. So, it can adsorb many substances, including gases and liquids, without changing their shape or structure. It’s also commonly used to remove fluoride, arsenic, and selenium from water. Moreover, this adsorbent is ideal for high-pressure applications due to excellent compressive strength and good abrasion resistance.

An oven is required to regenerate activated alumina. The heat evaporates the small water vapours and droplets trapped inside its tiny pores at temperatures ranging from 149°C to 204°C.

To restore activated alumina using the thermal regeneration method:

1. Distribute the beads or pellets evenly on a baking tray.
2. Heat in an oven at 350°F (175°C) for 4-6 hours. You can also heat-activated alumina at lower temperatures of 200°F (93°C) for longer periods.
3. Cool in a desiccated environment till room temperature and promptly store in a moisture-proof container.
4. Once this desiccant is restored, it can be reused multiple times before requiring regeneration.

Like molecular sieve, activated alumina can also be regenerated using Pressure Swing Adsorption (PSA) and vacuum regeneration.

4. Regenerating Clay Desiccants

Activated clay is primarily used in industrial packaging because of its high efficiency, dehydrating properties, and low cost. This desiccant is a porous mineral that is dried to create a material with a high adsorption capacity at average temperature and relative humidity levels.

The clay retains its structure as it becomes saturated and can be easily reactivated for reuse by heating, even at low temperatures. The desiccant is also safe to handle and dispose of, as it is chemically inactive and non-toxic. Moreover, it is usually less expensive than other adsorbents.

This adsorbent material’s main disadvantage is its ability to adsorb moisture at temperatures as low as 50°C. This property helps reactivate the desiccant but may cause issues in high-temperature applications.

To regenerate activated clay:

1. Spread the clay evenly on a heat-resistant tray.
2. Set the oven to a lower temperature, around 220°F (105°C).
3. Bake for 6 hours.
4. Cool in a moisture-free environment and store in an airtight container.

Like molecular sieve and activated alumina, there are other more complex ways to regenerate activated clay, such as chemical regeneration or microwave regeneration.

5. Refreshing Activated Carbon

Activated carbon is a form of carbon that has a unique, highly porous structure. Its composition gives it a high surface area with small, low-volume pores that increase the surface area available for adsorption.  This results in strong physical adsorption forces, making it a cost-effective solution for removing a wide range of pollutants, such as treating large volumes of low-polluting gas or water, leading the desiccant to be commonly used in water, air, and gas treatment, as well as odour control.

However, before reusing activated carbon:

1. Allow the activated carbon to dry completely if it has become damp due to adsorbing atmospheric moisture.
2. Preheat the oven to 230°C and spread the carbon in a single layer on a baking sheet.
3. Bake the activated carbon for one hour at 230°C to remove odours and impurities.
4. Allow the activated carbon to cool completely to prevent thermal shock and structural damage. After it has cooled completely, store it in an airtight container. Activated carbon can be reused multiple times thereafter.

Conclusion

Desiccants protect products from damp, mould, and spoilage-causing moisture during shipping and storage. They’re essential in many industries, including manufacturing, food, and pharmaceuticals, and they can be reused to improve eco-friendliness and cost-effectiveness.

At Stream Peak, we’re committed to delivering only the best. Each desiccant we offer undergoes rigorous testing in our in-house QA laboratory, ensuring quality. Our desiccant bag production also adheres to both ISO 9001 and 14001 certifications, ensuring the best in international quality and environmental standards. Engage with our team of packaging engineers to learn more.