Molecular filtration explained

摘要

Molecular filtration employs activated carbon, a microporous 'adsorbent' made from a carbonaceous material. Despite its solid appearance, microporous activated carbon is composed of a network of interlinked fissures and pores present throughout the material. The pores are tiny, ranging in size from <2 to >1,000 nanometres; they can only be seen with a powerful scanning electron microscope. Due to its complex internal pore structure, activated carbon is used in the purification and filtration of gases. Contaminant gas molecules in an airstream can enter the large pores at the surface of the carbon through a process called 'diffusion' and move towards the internal surface of the smallest pores. When a gas molecule collides with the carbon surface at a suitable site, an attraction is formed and it will be retained. Gas molecules are extremely small and are most strongly adsorbed in the smallest diameter pores.