[kamiyu]

Recently I used activated charcoal to purfiy an important compound. It works!!

But one question, do you guys know what exactly activated charcoal selectively absorbs? I used it because I guess there are come colored imurities in my sample

[Arkcon]

Activated carbon has a high surface area made up of a vast network of graphite rings.  It tends to selectively absorb aromatic compounds by pi-bond stacking.  There is however a great deal of ambiguity in how activated carbon works: http://en.wikipedia.org/wiki/Activated_carbon#Properties

[Enthalpy]

Do small aromatic rings stack? I believed that because of graphite (and may have even read it), but benzene crystals organize differently if I get it well: the hydrogens target the center of neighbour benzene's carbon ring, making a sort of H shape but in 3D.
http://commons.wikimedia.org/wiki/File:Benzene-xtal-3D-vdW.png
http://catalog.flatworldknowledge.com/bookhub/4309?e=averill_1.0-ch12_s05
well, sources diverge.