The physical and chemical characteristics of an activated carbon can strongly influence its suitability for a given application, and there are a number of different tests that help predict a carbon's ability to perform in various situations.
The iodine number test can usually predict effectiveness when very small molecules are to be adsorbed. Tannin value and molasses number or molasses decolorizing efficiency are more appropriate in lab test parameters for medium and large-sized molecules or when small molecules are present with larger molecules.
In applications where there are a wide variety of impurities to be removed, the best type of activated carbon is not so easily determined. When impurities range from very small to very large in size, the large molecules often clog up small pores, making them inaccessible to other molecules. In this case, Cabot recommends performance testing first (isotherm and pilot column) to identify the best activated carbon for a specific application.