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Originally Posted by Kief Reefer On the subject, though, what's the difference between activated carbon and zeolite crystal? |
Okay, here's an exerpt of the differences:
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Molecular Traps Zeolites and Activated Carbon
Molecular trap is a general descriptive term for specific chemical entities such as zeolites or activated carbon. Both of these have been used to provide functions based on filtration, refining, and/or separation of chemical mixtures. The use of activated carbon, for example, to filter contaminants from gases and liquids is well established. Museums such as the Gene Autry Western Heritage Museum in Los Angeles
5, for example, use activated carbon in the mechanical air handling systems to remove atmospheric pollutants in make-up air and to remove pollutants in the recirculation air potion of the museum's general environment.
This ability of both activated carbon and zeolites to trap chemical species provides the basis for an application of molecular traps in preventative conservation. Activated carbon is an inert, porous graphite described as "graphite plates". The presence of imperfections on the plates' structure leads to the formation of a rigid skeletal structure which can comprise 75% or more of the total volume of the voids in the activated carbon. The voids are adsorption centers using primarily London dispersionforces (a Van de Waal's force) to hold the trapped entities in place (Hollinger, 1994). Zeolite molecular traps are microporous crystalline aluminosilicate structures and provide selective molecular trapping based on size and polar properties (Dyer, 198

. They generally act as adsorbents for molecules small enough to pass into their internal cavities. The trapped molecules are held in the cavities by physical (physisorption) and chemical (chemisorption) bonding (Hollinger, 1994). The most significant point is that the zeolites' interior cavity can be modified during fabrication to target molecules of a particular size and polarity.
The crystalline nature of zeolite traps provides the inert, non-reactive character required for use in close proximity to artifacts, while providing a functional role in trapping various molecular species, in particular, undesirable gaseous chemical species, present in the collection environment.
The advantages of zeolites over activated carbon include the fact that they can be engineered to target specific sized chemical species and that they can be used in situations where the activated carbon cannot because of its color or handling problems............"
The full article is located HERE:
Zeolite Molecular Traps And Their Use In Preventative Conservation
Scroll down to the heading "Molecular Traps" and beyond..
sherry