Molecular filtration: The importance of gas phase filtration for effective gas adsorption

Harmful gases, such as volatile organic compounds (VOCs) and inorganic gases, are hazardous air pollutants. These airborne threats are completely invisible and can only be halted by using molecular filters. These gases often negatively impact both individual health and the environment, making effective gas phase filtration crucial in order to successfully combat these dangerous gases and improve quality of life.

We develop customised solutions for the molecular filtration of gases using our extensive range of activated carbons. At MANN+HUMMEL Air Filtration, our customers and partners can select products from our own filter media production range that effectively and reliably adsorb harmful gases such as ozone, nitrogen oxides, and many others.

Special pollutant gases require specialised solutions. We use filters based on the principles of chemisorption and physisorption. Both processes rely on adsorption, where substances fix themselves to the surface of a filter medium and accumulate there. The effectiveness of gas phase filtration depends on the surface area of the filter medium – the larger the surface area, the better the adsorption capacity and filtration performance. This can be measured using physico-chemical methods (e.g. BET measurements with nitrogen). With activated carbon filters from MANN+HUMMEL Air Filtration, the surface area of the activated carbon particles averages around 160,000 square metres.

In physisorption, adsorption occurs via physical Van der Waals forces, i.e., the attraction of forces between atoms or molecules. Due to this property, physical gas adsorption filters are highly effective against volatile organic compounds.

Generally, inorganic gases cannot be optimally adsorbed by activated carbon due to their distinct chemical-physical properties from VOCs. Here, chemical adsorption (chemisorption) can provide effective solutions.

For chemical filtration, activated carbon filter media are impregnated with special chemicals to make them highly effective against specific groups of inorganic gases. In gas phase filtration, the adsorptive (the substance to be adsorbed), the adsorbate (the adsorbed adsorptive), and the adsorbent (the material on which the molecules "adsorb") are firmly bound through chemical reactions (covalent bonding).

For acidic or alkaline gases such as hydrogen sulphide, nitrogen oxides, or ammonia, chemisorption through covalent bonds based on electrostatic attraction is deployed. We also use ion exchangers specifically for alkaline gases, which bind harmful molecules from the air and replace them with harmless ones. Ozone filters use a catalytic mechanism on the activated carbon, which allows almost 100 per cent of the ozone to react into oxygen.

MANN+HUMMEL Air Filtration ensures clean air by filtering out harmful gases. We’ll now explain which gases we target, how they are produced, and why they are dangerous.

We offer both physical and chemical gas adsorption solutions that effectively bind harmful gases. With over 80 years of experience in air filtration, we are one of the world's leading manufacturers of activated carbon filter media. Are you interested in customised molecular filtration? Then contact us today!