Reusing Desiccants in Packaging: Sustainable Moisture Solutions
Desiccants are vital tools for preservation and moisture control. They are substances or chemicals that absorb and attract moisture from the air, resulting in desiccation (dryness) in the surrounding atmosphere.
Desiccants are substances that absorb moisture from their surroundings. They are used across various industries 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 is frequently sealed with a small mesh bag labelled “Desiccant, Do Not Eat.”
The shelf life of desiccants is determined by the packaging environment in which they are used, but most desiccants have a shelf life of one to three years and can be reused upon regenerating them. Reusing desiccants reduces waste and provides an economical alternative to frequent replacements. By regenerating and reusing them, we can save costs and lessen the environmental impact of manufacturing and disposal.
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.
Silica Gel is a porous silicon dioxide form most frequently encountered in small packets tucked within the packaging of electronics and certain food products. Its remarkable ability to absorb up to 40% of its weight in water and its non-toxic and non-flammable properties are used by manufacturers aiming to prolong the shelf life and maintain the quality of products.
Clay Desiccants, primarily derived from bentonite clay, are natural desiccants renowned for their broad applications. They are often the go-to solution for bulk applications, notably in shipping containers. Notably, they protect machinery, metals, and electronics from the corroding effects of moisture. With an absorption capacity of approximately 25% of their weight in moisture and effectiveness up to temperatures of 120°F, they serve as reliable moisture combatants.
Activated Carbon’s primary strength lies in adsorbing organic compounds and neutralizing odours. Comprising carbon that’s been processed to possess small, low-volume pores, it amplifies its surface area, enhancing its ability to purify environments by controlling moisture and eradicating pollutants and unpleasant smells.
Molecular Sieves are crystalline aluminosilicates with consistent pore structures, ideal for drying gases and liquids. Their stellar performance, characterized by their ability to lower water content to levels below one ppm and their efficacy even at diminished humidity levels, cements their position in high-end industrial applications.
Activated Alumina porous incarnation of aluminium oxide, finds its niche in air drying systems and is instrumental in purifying drinking water by eliminating fluoride. Its high absorption prowess, complemented by its effectiveness over a diverse temperature spectrum, ensures its continued relevance across various industries.
Signs That a Desiccant Needs Rejuvenation
As valuable as desiccants are for moisture control, their effectiveness diminishes over time. Recognizing when a desiccant needs rejuvenation ensures optimal performance and product protection. 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 absorption, they can turn pink or green and appear cloudy. Clay Desiccants might become lumpy or change from their usual dry, powdery texture to a wetter, muddier consistency.
Reduced Absorption Efficiency: Over time, a desiccant might not absorb moisture as effectively as initially. This can be tested by placing the desiccant in a high-humidity environment and observing its performance over a set period. If items stored with the desiccant show signs of moisture damage or mould growth, it shows reduced efficiency.
Weight Gain in Desiccants As desiccants absorb moisture, they gain weight. One can determine its moisture content by periodically weighing a desiccant and comparing it to its initial weight. A significant increase in weight indicates saturation and a need for rejuvenation.
How to Rejuvenate Different Desiccants
The value of desiccants in maintaining an optimal environment is undeniable. Over time, these desiccants lose their efficacy, but with proper rejuvenation techniques, they can be returned to their original state, ready for reuse.
Oven-drying Silica Gel
Silica gel is a moisture-absorbing desiccant commonly used in the healthcare and electronics industries to adsorb moisture. Adsorption is when water in the air is absorbed between the microscopic pores as the air passes through them, which is made possible by the high surface area of the desiccant. The absorbers are made of oxygen and silicon atoms and have nanometer-sized voids.
When the desiccant absorbs moisture, it transitions from active to inactive. When this occurs, the desiccant must be reactivated before it can be used again. Their distinctive trait of changing colour when saturated makes the rejuvenation process straightforward. To restore its drying capability:
- Spread the silica gel beads on a baking tray, ensuring they’re in a single layer.
- Preheat your oven to 250°F (120°C) and place the tray inside.
- Bake for 3-5 hours, periodically checking for a colour change (typically from pink to blue or transparent, depending on the type).
- Once dried, store immediately in an airtight container to prevent moisture absorption.
Refreshing Molecular Sieve
Molecular Sieve is used for dehydrating, purifying, and separating specific gases and liquids. It is widely used in filtration systems to reduce humidity levels due to its ability to absorb up to 22% of its weight and withstand temperatures as high as 300°C.
Due to water adsorption from carrier gas or samples, the separating power of the desiccant can gradually decrease, which means that they will not work as well as they did the first time, and regeneration is required. Molecular sieves can be trickier to regenerate due to their high affinity for water.
Although some Molecular Sieves that remove alcohols and aromatic hydrocarbons use force to regenerate the sieve, most water-adsorption Molecular Sieves are usually regenerated by heating. Depending on the Molecular Sieve type, regeneration temperatures range from 175°C to 315°C. Most industrial applications require temperatures ranging from 121°C to 232°C.
- Place them in an oven set to 450°F (232°C).
- Heat for 1-2 hours.
- Allow to cool in a sealed environment to prevent immediate moisture uptake.
The methods for regenerating Molecular Sieves include:
- Pressure change (oxygen concentrators).
- Heating and purging with a carrier gas (ethanol dehydration).
- Heating under a high vacuum.
Regenerating Activated Alumina
Activated alumina is used in various heavy industrial applications, including catalyst adsorption and fluoride removal. The desiccant has a surface area greater than 200m2g and can adsorb many substances, including gases and liquids, without changing their shape or structure. It is also commonly used to remove fluoride, arsenic, and selenium from water. Moreover, the adsorbent is ideal for high-pressure applications due to its toughness.
An oven is required to regenerate the desiccant using hot air or gas. The heat evaporates the small water vapours and droplets trapped inside the tiny holes at temperatures ranging from 149°C to 204°C. Once the desiccant is restored, it can be reused multiple times.
- Distribute the beads or pellets evenly on a baking tray.
- Heat in an oven at 350°F (175°C) for 4 hours.
- Cool in a desiccated environment and promptly store in a moisture-proof container.
Regenerating Clay Desiccants
Activated clay is primarily used in industrial packaging because of its high efficiency, dehydrating properties, and low cost. The dessicant is a porous mineral dried to create an adsorbent 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.
The adsorbent material’s main disadvantage is its ability to absorb moisture at low temperatures. Temperatures as low as 50°C may start releasing moisture into the environment. This adsorbent material property helps reactivate the desiccant but may cause issues in high-temperature applications. The desiccant is safe to handle and dispose of as it is chemically inactive and non-toxic. Moreover, it is usually less expensive than other adsorbents.
- Spread the clay evenly on a tray.
- Set the oven to a lower temperature, around 220°F (105°C).
- Bake for 6 hours.
- Cool in a moisture-free environment and store in an airtight container.
Refreshing Activated Carbon
Activated carbon is a type of graphite with a random, flawed structure with a wide range of pore sizes, resulting in a high surface area and the highest physical adsorption forces. The desiccant is also a cost-effective method for treating large volumes of low-polluting gas or water, and it is commonly used in water, air, and gas treatment, as well as odour control.
Before reusing Activated Carbon:
- Allow it to dry completely if the Activated Carbon has become damp due to absorbing atmospheric moisture.
- Preheat the oven to 149°C and spread the Carbon in a single layer on a baking sheet.
- Bake the Activated Carbon for one hour at 149°C to remove odours and impurities.
- Allow the Activated Carbon to cool completely before placing it in an open shallow dish to remove odours. After it has been cooled completely, it can be reused multiple times.
Conclusion
Desiccants protect products from moisture during shipping and storage. They’re essential in the manufacturing, food, and pharmaceutical sectors and can be reused. 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 adheres to ISO 9001 and 14001 certifications, ensuring adherence to international quality and environmental standards. Contact us and book a no-obligation appointment with our packaging engineers to learn more.