Effects of Activated Carbon Surface Chemistry and Pore Structure on the Adsorption of Methyl Tertiary-Butyl Ether and Trichloroethene from Natural Water

摘要

To systematically evaluate pore structure and surface chemistry effects, a matrix of activated carbon fibers (ACFs) with three activation levels and four surface chemistry levels was studied. To evaluate whether adsorption trends established for ACFs are also valid for granular activated carbon (GAC), ACF results were compared with those obtained for three commercially available GACs. Adsorption capacities were determined for methyl tertiary-butyl ether (MTBE) and trichloroethene (TCE) in organic-free water, for natural organic matter (NOM) and for MTBE and TCE in the presence of NOM. For adsorbents with similar pore structure, single-solute isotherms illustrated that both MTBE and TCE adsorption capacities were largest on the most hydrophobic adsorbents, and a similar trend was confirmed in the presence of NOM. Consistent with molecular size, TCE adsorption occurred primarily in 7-10 ? pores while MTBE adsorption occurred primarily in 8-11 ? pores. Effective adsorbents for drinking water treatment should therefore contain little oxygen and nitrogen whose presence increases the polarity of the adsorbent surface. Based on the elemental composition of the low-ash carbons evaluated in this study, activated carbons should exhibit an elemental (O+N)/C ratio of less than 0.05 to assure sufficient hydrophobicity. In addition, adsorbents should exhibit a large pore volume in the 7-11 A range when contaminants with molecular sizes similar to those of MTBE and TCE are targeted for removal from drinking water.