Adsorption on porous carbons was described as early as 1550 B.C. in an ancient Egyptian papyrus and later by Hippocrates and Pliny the Elder, mainly for medicinal purposes. In the 18th century, carbons made from blood, wood and animals were used for the purification of liquids. All of these materials, which can be considered as precursors of activated carbons, were only available as powders. The typical technology of application was the so-called batch contact treatment, where a measured quantity of carbon and the liquid to be treated were mixed and, after a certain contact time, separated by filtration or sedimentation.
At the beginning of the 19th century the decolourisation power of bone char was detected and used in the sugar industry in England. Bone char was available as a granular material which allowed the use of percolation technology, where the liquid to be treated was continuously passed through a column. Bone char, however, consists mainly of calcium phosphate and a small percentage of carbon; this material, therefore was only used for sugar purification.
At the beginning of the 20th century the first processes were developed to produce activated carbons with defined properties on an industrial scale. However, the steam activation (V. Ostreijko, 1900 and 1901) and chemical activation (Bayer, 1915) processes could only produce powder activated carbon.
During the First World War, steam activation of coconut char was developed in the United States for use in gas masks. This activated carbon type contains mainly fine adsorption pore structures suited for gas phase applications.
CALGON CARBON Corporation (USA), the parent company of CHEMVIRON CARBON, succeeded after World War II, in developing coal based granular activated carbons with a substantial content of transport pore structure and good mechanical hardness. This combination allowed the use of activated carbon in continuous decolourisation processes, resulting superior performance. In addition, CALGON CARBON and CHEMVIRON CARBON pioneered work on the optimisation of granular carbon reactivation.
Today, many users are switching from the traditional use of powdered activated carbon (PAC) as a disposable chemical to continuous adsorption processes using granular activated carbon (GAC) combined with reactivation. By this change they are following the modern tendency towards recycling and waste minimisation, thereby reducing the use of the world's resources.