What is the difference between granular activated carbon and anthracite?

Anthracite filter media is employed in the filtration process to remove particulate matter that has already been precipitated out of solution and sometimes chemically treated to improve its filterability. It does not function very well at the molecular level because its pores are very small, much smaller than most of the molecules that must normally be removed. GAC (Granular activated carbon) is made from agglomerations of PAC (Powdered activated carbon) particles. PAC is produced by driving out volatiles and burning away carbon in order to increase the size of the pores in the carbon particles, until they resemble a molecular sponge. Depending upon the pore size, activated carbon can even be processed to be selective, and remove only certain molecules, and leave others. This pore structure causes the removal of molecules by the process of adsorption onto the surface of the carbon particle followed by diffusion into and absorption in the pores. Precipitation is not necessary in this ...  more