- Charcoal is obtained by burning wood, nutshells, coconut husks, animal bones, and/or other carbonaceous (carbon-containing) materials. Charcoal becomes activated by heating it with steam to approximately 1000 o C in the absence of oxygen (O2 ). This treatment removes residual non-carbon elements and produces a porous internal microstructure having an extremely high surface area. A single gram of such material can have 400 to 1,200 square meters of surface area, 98% of it internal!
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The chemical nature of amorphous carbon, combined with a high surface area and porosity, makes it an ideal medium for the adsorption and absorption of organic chemicals. Adsorption means that the chemical has an interaction with the surface of the material; absorption is incorporation into a host structure through pores (interstices). To avoid confusion, we can refer to the incorporated material as "sorbed".
Activated carbon can remove organic materials from gas streams or solutions. The amount of material removed depends on the capacity of the activated carbon as well as the affinity of the material for the carbon. Typical uses are to remove odors and volatile organic compounds (VOC's) .
Laboratory chemists often use activated carbon to remove colored impurities from crude organic reaction products. Typically, one dissolves the material in a solvent (if it is not already a liquid), adds activated carbon, and then filters the mixture to remove the carbon. This technique works well for colorless or lightly colored materials; in general, colored impurities tend to have molecular structures that make them bind preferentially to the charcoal.
Activated charcoals impregnated with other materials are also effective industrial and laboratory catalysts
for chemical reactions. For example, vegetable oils may be hydrogenated by exposing them to a hydrogen atmosphere in the presence of a carbon-supported palladium catalyst.
Supplied air respirator systems do not depend on charcoal canisters and provide superior respiratory protection.
- Activated charcoal can appear in several ways on an MSDS:
- It may be specified as a gas or vapor adsorbent in air-purifying respirators. These are commonly provided as screw-on cartridges. Keep in mind that charcoal canisters or filters have a finite capacity for organic materials and that one can generally not tell when this limit has been reached. Regularly replace filters according to the manufacturer's recommendations.
NEVER attempt to use regular charcoal briquettes (the kind you buy at a store for a barbecue grill) as a substitute for activated charcoal.