Activated carbon, known more commonly as charcoal, is widely used throughout the pharmaceutical industry as an adsorbent for removing pollutants, odour and noxious gasses from packaged products. This is due to its amorphous, highly porous structure, which provides a large surface area for adsorption of gases and volatile organic molecules.
But, equally importantly, manufacturers and distributors choose activated charcoal for their packaging as it is especially effective in combination with other substances, such as desiccants for the control of both moisture and odour.
The manufacturing process of activated carbon
Activated carbon can be manufactured from many materials including coconut shells, peat, wood, coal and fruit stones. However, all of these materials result in varying degrees of pore size and distribution during activation. At Cilicant, we have found that coconut shell produces a very pure and efficient form of activated carbon that tends to be denser with a greater number of micro-pores. Furthermore, by using coconut shell in the production process, at Cilicant, we’ve been able to create pouches that are non-dusting. This attention to quality means we are able to offer a superior product that safeguards formulators and manufacturers from customer complaints arising from dusting issues. In addition to this, coconut shells are a very sustainable and renewable resource.
The first step of the manufacturing process involves thermal decomposition of the raw material, producing a carbonaceous mass full of tiny pores. In the second stage, this base material is ‘activated’ in steam-heated to up to 1,100 degrees Celsius.
Cilicant activated carbon has a lattice structure with a network of micro-pores, creating a large surface area for adsorption. Volatile gases and odours are attracted to this structure by physical adsorption and held to the surface until equilibrium is reached between adsorbed molecules and those still freely distributed carrying moisture or gas. Chemisorption also occurs when new chemical bonds are formed between the adsorbates and the surface of the activated carbon.
Properties that make activated carbon ideal for active packaging
Large surface area – The layered structure of activated carbon produces a surface area in the range of 200 to 2,000 m2/gm – just a spoonful would be equivalent to the entire surface area of a football field, meaning small amounts are effective in active packaging.
Thermal/PH properties – Activated carbon is stable over a wide range of PHs and temperatures. It performs equally well when used with acidic, or alkaline substances, making it highly resilient and reliable. Steam activated carbon remains stable well above its activation temperature.
Inert – Being inert in nature, activated carbon does not result in the decomposition of active ingredients. This greatly reduces the risk of undesirable reactions between the sorbent and the product, so drug efficacy remains high.
Hydrophobicity – Activated carbon is non-polar and hydrophobic, so is particularly effective in packaging where free moisture may limit the adsorption capacity of other sorbents. This means it can be safely combined with other desiccants for enhanced effectiveness and use in specific applications.
With a yield in the range of 95-98%, activated carbon, by nature, is an excellent adsorbent. In practice, the actual yield may depend on factors, such as the raw material, activation process and concentration of adsorbates.
Activated carbon in real-life applications
The excellent properties of activated carbon in tackling odour issues is highlighted in these examples of how it has been used to solve real-life pharmaceutical packaging challenges:
Metformin – This diabetic drug is well-known for an unpleasant odour, so unpleasant that some patients don’t adhere to the correct dosage routine. While extended versions of the drug have resulted in lower levels of odour, activated carbon in packaging can prevent excess build-up of odour before opening.
Formaldehyde/formic acid-induced degradation – Reactions in excipients containing formaldehyde and formic acid can lead to drug degradation. Studies have shown that activated carbon can attenuate this degradation and also address stability issues due to gelatine cross-linking.
Combining activated carbon with other active packaging materials
Since activated carbon is safe to combine with other desiccants and gas absorbers, the formulation of active packaging can be modified for greater effectiveness in certain applications. Here are just some of the combinations used:
Silica gel – As a micro-porous form of silicon dioxide, silica gel has been used effectively in moisture control for many years. While activated carbon is non-polar, silica gel possesses hydroxyl groups for the adsorption of free moisture. The non-toxic properties of both make this a good combination for nutraceuticals.
Bentonite clay – This calcium-rich and cost-effective montmorillonite desiccant possess a layered structure offering a large surface area for water adsorption on both its outer and inner surfaces. Naturally occurring and non-toxic, bentonite clay is ideal for use in pharmaceutical products. As activated carbon has poor desiccant properties, combining with bentonite clay delivers effectiveness in both moisture and odour control.
Oxygen absorber – As the name suggests, these substances reduce the amount of free oxygen in packaged products. While not classed as desiccants, oxygen absorbers can protect from oxidative degradation using iron which reacts with free oxygen to produce rust. In combination with activated carbon, this is particularly useful for eliminating odour, volatile gases and oxygen in packaging.
Molecular sieve – This synthetic zeolite sorbent is used to control odour and gas in pharmaceuticals/nutraceuticals. Like activated carbon, it has a high affinity for hydrocarbons and organics. Unlike non-polar activated carbon, molecular sieve has aggressive moisture control properties that make it a good choice for holistic moisture and odour control. On the downside, it isn’t suitable for applications requiring subtle control of moisture.
Clearly, on its own, activated carbon is an excellent choice for the control of odour and gases in active packaging. But, when combined with other active packaging materials, it becomes a truly effective and versatile solution for the active packaging industry, ensuring products reach the end-user with minimal loss of quality and efficacy.
For the best activated carbon solution for your active packaging needs, get in touch with our technical sales representative now!
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