In a low-oxygen environment, the naturally carbon-rich shells are slowly heated to a very high temperature. It eliminates water and contaminants from the shells without causing them to burn. A number of chemical and/or physical procedures are used to activate the resultant substance, known as char. These activation mechanisms greatly increase the surface area and result in the formation of a porous network.
The activated carbon is then powdered, granulated, or extruded into the required shape. Particles tiny enough to pass through an 80 mesh filter make up powdered activated carbon. Granular particles are somewhat bigger and come in a variety of sizes. Granular activated carbon is combined with a binder and pushed through a pellet machine to create extruded activated carbon. Each kind is best suited to a certain purpose. If desired, the activated carbon is impregnated with one or more compounds.