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gasadsorption-physisorption

   

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.

Chemisorption and physisorption: The science behind gas adsorption

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.

Physisorption for VOCs

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.

Chemisorption: Impregnated activated carbon for special gases

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.

Gas adsorption: Separating the useful from the harmful

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.

VOCs: Gas phase filtration against the invisible threat

VOCs are omnipresent, arising from many different sources. Outdoors, they mainly come from biological degradation, metabolic processes, and technical processes involving incomplete combustion (e.g., motor vehicles). Indoors, awareness of the effects of harmful VOC concentrations has been increasing. Potential sources include evaporating solvents (emanating from various building materials, cleaning agents, and cosmetics), tobacco smoke, and human metabolism. Thanks to physisorption, activated carbon filters can successfully bind VOCs from the air.

We provide molecular filtration solutions to help combat the following VOCs:

Toluene C7H8

Inhaled toluene (C7H8) can cause fatigue, eye and respiratory tract irritation or even unconsciousness. It’s used in paints, varnishes, cleaning agents, disinfectants, cosmetics, and many other products. Toluene is also released through incomplete combustion processes, such as from motor vehicles or smoking.

formaledhyde

The carcinogenic VOC, formaldehyde (CH₂O), can cause allergies and irritation to the skin, respiratory tract, and eyes. Major sources include wood-based materials, floor coverings, and certain insulating materials. Other everyday sources include tobacco smoke, candles, and textiles.

This compound can have anaesthetic effects, causing headaches, nausea, and irritation of the eyes, mouth or nose. It’s used in the manufacture of textiles, artificial leather, paraffin wax, adhesives, and coatings, among other things.

    

Inorganic gases: Filtration systems with impregnated activated carbon

With our impregnated activated carbon filter media, we can safely and reliably remove the following acidic and alkaline gases from the air:

H2S

Hydrogen Sulphide (H₂S): An invisible acid gas with a rotten egg smell, produced from natural sources such as volcanoes and biological decomposition processes. It’s highly toxic, flammable, and corrosive.

SO2

Sulphur Dioxide (SO₂): An acidic gas with a pungent odour, produced by the combustion of fossil fuels. Its concentration is often high indoors, especially in industrial areas or near traffic. Sulphur dioxide irritates mucous membranes and causes long-term damage to buildings and technical systems.

NOx

Nitrogen Oxides (NOₓ): This collective term refers to inorganic acid gases consisting of nitrogen and oxygen. Nitrogen oxides, nitrogen monoxide (NO), and nitrogen dioxide (NO₂) are primarily produced by fossil fuel combustion. NO₂, in particular, is a dangerous ​corrosive gas that can damage the respiratory tract.

NH3

Ammonia (NH₃): A pungent-smelling basic noxious gas mainly released by agricultural processes. It’s corrosive and harmful to health, causing irritation of the nose, throat, and respiratory tract. At high concentrations, it can even lead to blindness and death.

O3

Ozone (O3): Formed when nitrogen oxides (NOₓ) and VOCs combine in sunlight. Indoors, older printers and photocopiers or disinfectants can release ozone. This harmful gas irritates the respiratory tract and eyes and can impair lung function.

   

Gas phase filtration from MANN+HUMMEL: Leadership in filtration

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!