TABLE OF CONTENTS The following are some adsorbent materials that may be may be used in nonwoven filters:
Activated carbon.
Activated alumina: Lower surface area but good base for certain impregnations.
Zeolite: Man-made, pore sizes can be designed for specialty separations.
Zeolite: Natural.
Ion exchange resins: Can be produced with controlled pore sizes and high chemical capacities.
Silica gel.
In addition to points (a)-(e) above, Flanders Filters is marketing a residence ventilation filter containing baking soda (sodium bicarbonate, NaHCO) for odor removal.
Middlebrooks [88] suggests that activated carbon is by far the preferred adsorbent for nonwoven filter medium applications. Generally it is the adsorbent with the largest total surface area depending on source. The most common sources are coal, wood, and coconut. Figure 4.35 is a microphotograph of the extended surface of an activated coconut carbon granule. Any organic material that can be charred and activated to a carbon can be used for producing some form of activated carbon. Synthetic polymer fibers such as PAN have been used for producing ACF. The choice depends on pore size and distribution. Generally, coconut sourced activated carbons are used for air filtration applications while coal-based carbons are preferred for water filtration. There are also carbons impregnated with some form of chemical to develop and enhance chemsorption properties.
Reproduced with permission of INDA Cary, North Carolina, USA [88].
One type of impregnated activated carbon, ASZM-TEDA carbon, has been used...
