TCE adsorption by GAC preloaded with humic substances

ranular activated carbon (GAC) adsorption has been identified by the Safe Drinking Water Act amendments of 1986 as the best available technology for removing synthetic organic contaminants (SOCs) from drinking water supplies.1 GAC is particularly suited for treating water because it effectively removes a wide range of organic compounds and can protect water supplies from such transient occurrences as occasional spills and seasonal loadings of toxic or potentially carcinogenic compounds. However, naturally occurring, macromolecular dissolved organic matter Adsorption of trichloroethylene (TCE) by activated carbon preloaded with humic and fulvic acids was studied under several conditions in completely mixed batch systems. The authors investigated how molecular weight and molecular-weight distribution of preloaded humic substances affected subsequent adsorption of TCE. The capacity of carbon to adsorb TCE was most greatly reduced in carbon that was preloaded with humic acid components having molecular weights less than about 1,400 g/mol as polystyrene sulfonate. The adsorption capacity was greatly reduced in carbon that was preloaded with whole humic mixtures in which lower molecular weights predominated. The energy distributions of adsorbent indicate that preloaded compounds preferentially occupy high-energy sites, making them inaccessible to subsequently encountered TCE. For executive summary, see page 166.