Effects of Activated Carbon Characteristics on Organic Contaminant Removal

Many water treatment plants need to remove objectionable trace organic compounds, and activated carbon adsorption is often the best available technology. Utilities face the challenge of having to choose from a large variety of activated carbons, and iodine number or BET surface area values are often utilized in the selection process. Although neither parameter correlates well with adsorption capacities, alternative activated carbon selection criteria based on fundamental adsorbent and adsorbate properties are lacking to date. The first objective of this research was to systematically evaluate the effects of activated carbon pore structure and surface chemistry on the adsorption of two common drinking water contaminants: the relatively polar fuel oxygenate methyl tertiary-butyl ether (MTBE) and the relatively nonpolar solvent trichloroethene (TCE). The second objective was to develop simple descriptors of activated carbon characteristics that facilitate the selection of suitable adsorbents for the removal of organic contaminants from drinking water. Overall, the results of this study showed that the adsorption capacity for a micropollutant is maximized for adsorbents with (1) a large volume of micropores with widths that are about 1.5 times larger than the kinetic diameter of the target adsorbate; (2) a micropore size distribution that extends to widths that are approximately twice the kinetic diameter of the target adsorbate to prevent pore blockage by competing natural organic matter (NOM); and (3) a hydrophobic pore surface chemistry which, when expressed as the sum of the oxygen and nitrogen contents, should not exceed 2 to 3 mmol/g Originally published by AwwaRF for its subscribers in 2003 This publication can also be purchased and downloaded via Pay Per View on Water Intelligence Online - click on the Pay Per View icon below