Activated carbonis used to remove pollutants from air or water streams, both in the field
and in industrial processes such asspill cleanup, groundwater remediation, drinking water
filtration, air purification, and the capture of volatile organic compounds(VOCs).
Activated carbon filters and activate carbon filter media are also used in odor
control and reverse osmosis applications.
Most activated carbon is made of bituminous coal or lignite, a low-sulfur coal with high
moisture content. The material sourceand mode of activation determine the specific
properties of active carbon. Property standards are also important to considerwhen
selecting products from activated carbon suppliers.
Active carbonis available in various forms. Examples include activated carbon beds
and activated carbon blankets. There aretwo main types of activated carbon beds:
fixed and fluidized. Although fixed beds are suitable for some applications,
fluidizedbeds offer excellent gas distribution and lower resistance to gas flow.
Activated carbon blankets are used to absorb fumes andodors from products such
as new carpeting, cars, furniture, and homes. Activated carbon cloth and activated
carbon fabric ischaracterized by its large adsorption volume, fast adsorption speed,
heat resistance, and chemical resistance.
Activated carbon filters such as blocks, canisters, cartridges, and pellets are also
available. Activated carbon blocks are blendsof mesh-activated carbon, water, and a
plastic binder. They are hardened and extruded to form a solid matrix. Although the
plasticbinder occludes a percentage of the adsorption sites, activated carbon blocks
feature a finer mesh size that provides fasteradsorption kinetics and a greater
adsorption capacity. Activated carbon canisters, cartridges, and pellets are also
available. Mostactivated carbon canisters and activated carbon cartridges are used
for air and water filtration. Activated carbon pellets are usedin vapor applications.
Their particle size and pore structure adsorb impurities from a vapor steam with
limited flow resistance.
Specifications foractivated charcoalinclude particle size or mesh, surface area, pore
volume, moisture range, adsorptioncharacteristics, pH, water solubility, and tamped
bulk density. The percentage of ash, iron, and phosphates is also important toconsider.
For high-purity applications, activated carbon filters should contain very low amounts
of iron, typically 100 parts permillion (ppm). Activated carbon with extremely high
adsorptive capacities is suitable for decolorizing applications, and may carryproduct
specifications for methylene blue adsorption and have a molasses decolorizing number.