Gas Phase Filtration

Gas Phase FiltrationGas phase filtration is a way of removing gaseous contaminants from the breathing air in the laboratory space.

The choice of a correct and appropriate filtration is as important as the proper operation of the laboratory equipment like fume cabinets and biological safety cabinets. Inadequate filtration regimen by using the wrong filtration media for the application or lack of servicing on the media can lead to an uncomfortable and ultimately unwanted occupational health complications for laboratory workers.

Gas phase filtration is a way of removing gaseous contaminants from the breathing air in the laboratory space. The possible first step in achieving standard compliant clean laboratory air is to remove the source of gaseous contaminants but sources are created by processes that may be key processes carried out in the laboratories or occur naturally which can only be modulated and not eliminated completely1, leading to a need to install a gas filtration system that is properly designed for the air cleaning needs of the laboratory on a case-by-case basis.

An activated carbon media consisting of a variety of high carbon-content substances including coal, bituminous wood, coconut shells and bamboo raw materials is commonly utilized to filter the contaminant-infested air. Activated carbon is usually prepared as powder or small pellets. Activated carbon operates by means of adsorption, absorption and chemisorption assisting in attracting the gaseous contaminants to the activated carbon like a sponge and held into place by a variety of forces.

Adsorption

Adsorption is one of the surface reactions that have a rich empirical history of discovery and have numerous industrial chemical process applications like separation technology, industrial catalysis and more relevantly pollution control encompassing gas phase filtration2. Adsorption occurs when a solid surface is in contact with a gas or liquid, it is defined as the enrichment of material or increase in the density of the fluid near an interface (Rouquerol et al., 2014). The effect of adsorption in many cases is dependent on the size of the interfacial area. Consequently, all industrial adsorbents are highly porous or powders meaning larger specific surface areas, this phenomenon makes activated carbon one of the most effective adsorbents, hence an excellent choice for a gas filtration system media.

It is generally referred to as physical adsorption that is in comparison to chemical adsorption or chemisorption.

Chemisorption

A kind of adsorption in which the strength of the forces between adsorbents and surfaces are strong chemical forces and have high level of specificity as to which surfaces can bond with which gases [3], is it also commonly referred to as chemical adsorption. Chemisorption is an irreversible process and take place at higher temperatures compared to physical adsorption.3

SBT Laboratories can supply and install activated carbon pellets as part of gas filtration systems for the filtration of gaseous contaminants, including acidic gases and Volatile Organic Compounds (VOCs). An extensive list of contaminant gases can be filtered with different ranges of activated carbon products as specified for the application. Contaminant gases that can be filtered from the airstream utilizing the extensive range of activated carbon pellets include:

  • Hydrogen Sulphide
  • Sulphur Dioxide
  • Other oxides of sulphur
  • Nitrogen oxides
  • Chlorine
  • Ammonia
  • Formaldehyde
  • Hydrocarbons
  • Mercaptans
  • Low molecular weight organic acids (oxalic, formic, malic, acetic acids)
  • Volatile organic compounds (VOCs)

For gases not listed custom pellets solutions for specific contaminant gases can be indicated for on-site applications. Please consult an agent for a thorough assessment of your gas filtration needs and recommendation of the right activated carbon filter for the right application.

REFERENCES

  1. Gas Phase Filtration: A Guide to Understanding Gaseous Contaminant Air Filtration. (2018). [ebook] Available at: http://www.na.kccustomerportal.com/Documents/Upload/Application/2811/Learning%20Center/Article/Gaseous_Contaminant_Air_Filtration.pdf [Accessed 13 Jul. 2018].
  2. Rouquerol, F., Rouquerol, J., Llewellyn, P., Maurin, G. and Sing, K. (2014). Adsorption by powders and porous solids: Principles, Methodology and Applications. 2nd ed. Amsterdam [u.a.]: Elsevier, Academic Press, p. 1.
  3. Schmal, M. (2018). HETEROGENEOUS CATALYSIS AND ITS INDUSTRIAL APPLICATIONS. [S.l.]: SPRINGER, p.117.

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