Activated Carbon Now

With so many treating carbon as a pollutant these days, many might be surprised to know that without it, our drinking water supply would be seriously contaminated. Whether it be particulate contamination or organics, a readily-accessible form of carbon, activated carbon, functions as an excellent water filtrant for a variety of drinking water pollutants.

Of particular concern are the organics, which, when they react with disinfectants in the water, particularly chlorine, form disinfection by-products (DBP’s), which are often carcinogenic. Activated charcoal removes these DBP’s and other impurities by adsorption, which in scientific terms means that the impurities stick to the surface of the activated charcoal, thereby removing them from the water which passes through.

So, how does it work? In order to be an effective adsorbent (not to be confused with absorbent, which would be taking of materials into the interior of a solid), a comparatively large surface area must be available to do the absorbing. Activated charcoal has a structure very similar to honeycomb, which, because of the many large pores, has a much larger surface area than a sheer surface would have. As a result, more surface is available to adsorb more pollutants, and you have a relatively effective adsorption filter. Carbon readily bonds to itself, either chemically or physically through Van der Waals forces. With all this surface area exposed to the water, the organics dissolved in the water preferentially stick to the activated carbon, leaving the purified water to run on past. Of equally practical value is that since the organics stick to the surface of the activated charcoal and are not absorbed into the interior, often the filter can be taken out, treated to remove the organics stuck onto the surface, and returned to use as good as new.

So, what is the “activated” part and where is activated charcoal found? The source of activated charcoal can be any natural carbon source, such as wood, sawdust, peat, coconut shells, or petroleum residues. The particular source of carbon is chosen based upon desired pore size, space between pores, and other physical factors. The carbon is then dehydrated and carbonized by slow heating in anaerobic conditions in order to drive out water and other impurities. The activation step is then done with chemical treatment, usually in gaseous form, to end up with the specific desired properties of density, hardness, and other physical parameters of the application.