All about activated carbon
Activated carbon is a porous material with multiple benefits that has been tested and approved over the centuries. Obtained by carbonising and then activating a vegetable organic material, activated carbon is an adsorbent. Adsorption (different from absorption) is a physical phenomenon where a porous surface attracts and then captures polluting molecules in its pores.
Once upon a time, activated carbon
Activated charcoal was already known and used in ancient Egypt, Greek Antiquity and by the Maya in Latin America for water filtration and medicine. It has been used throughout the ages, including during the First and Second World Wars, when it was incorporated into gas masks to protect soldiers from toxic gases.
Today, technological innovations have made it possible to optimise the adsorption capacities of activated vegetable carbon to make it a high-performance filtration method, particularly in water and air filtration.
How is activated carbon made?
Produced in powder, granule or fibre form, activated carbon follows a precise manufacturing method:
In an oxygen-free environment, selected organic plant material (wood bark, bamboo, coconut shells, olive pits, etc.) is calcined at high temperatures. During this process, particles of carbonised material evaporate and create pores in the charcoal. The material has become porous.
Activation removes the tar still trapped in the pores of the material. This process increases the porosity of the activated carbon and thus increases its capacity to adsorb contaminants. Thanks to this step, the adsorption surface can be between 500 and 2500m²/g! There are two methods for this: one physical and one chemical.
- Physics: Again, the coal is carbonised at a very high temperature, while inducing a thermal shock with the help of an air stream or steam.
- Chemical: Immersed in a chemical agent (e.g. phosphoric acid), the activated carbon is heated to a lower temperature and then rinsed to remove product residues.
The difference between these two methods? Physical activation forms narrow pores while chemical activation generates larger pores.
The uses of activated carbon in filtration
Depending on the filtration objective, the activated carbon used in HIFI FILTER® filters can take different forms:
- To neutralise odours, activated carbon particles are embedded directly in a cellulose or synthetic media. This is an impregnated media. Another possibility is the multi-layer media. A layer of activated carbon is inserted between two layers of filter media.
- In order to block vapours, hazardous substances and toxic gases, a larger quantity of activated carbon is required. A specific treatment time is also essential to ensure its effectiveness. It is mainly found in granular form or in a more compact form in filter cells.
Today, activated carbon is a real ally in our daily lives, mainly in water and air filtration. What are its different uses?
Filters for liquids
Liquid filters, especially water filters, are mainly composed of granular activated carbon. They can be installed in collective or individual systems. Whether it is for a water treatment plant or a kitchen, the porous surface of activated carbon is able to capture various pollutants present in the water. For example, activated carbon reduces chlorine levels and blocks chemical residues such as pesticides and heavy metals like lead. Its adsorption capacity also neutralises unpleasant odours, improving the taste of the water. In other words, activated carbon improves the potability of water and contributes to the protection of end consumers.
In an air filter, activated carbon, combined with other filters, adsorbs Volatile Organic Compounds (VOCs), which are known to be volatile and dangerous to living beings and the environment. Commonly referred to as butane, toluene, ethanol, acetone or benzene, these pollutants are found in solvents, degreasers, cleaning agents, preservatives, etc. Used daily in several industrial sectors such as metallurgy, plastics, printing, textiles, pharmaceuticals and chemicals, these products emit toxic gases. To protect their operators, these production plants regularly install activated carbon air filters.
Outside industry, conventional agriculture also uses activated carbon in its cabin filters. During spraying, plant protection products produce aerosols and gases that are toxic to farm operators. In combination with a HEPA absolute filter, activated carbon helps to capture these pollutants and protect the driver.
Note that in an air filter, activated carbon can also stop :
- Smells: tobacco, food, paint, etc.
- Allergenic pollutants: pollen, animal hair, etc.
- Bacteria: moulds, fungi, etc.
How can the effectiveness of activated carbon be guaranteed?
In order to guarantee optimal efficiency of the activated carbon, several criteria must be taken into account:
- Filter saturation: If its pores are saturated, the activated carbon will no longer capture pollutants and may release some of those previously retained. People in the vicinity would therefore be at risk. In order to guarantee their safety, it is therefore essential to change the filters regularly.
- Humidity: If the humidity is too high, the activated carbon will primarily adsorb water molecules. Other pollutants will not be blocked.
- The air/water flow rate: If the flow rate is too high, the activated carbon will not have time to adsorb all the pollutants.
- The number of associated filters: Filters installed upstream will limit saturation of the activated carbon.
- The type of original material: Each organic plant material used initially has different properties. Its choice therefore impacts the adsorption level of the activated carbon.
All the information presented above is generic and for information purposes only. For more information, please contact us.