AWWA ACE59831

Methyl tertiary-butyl ether (MTBE) is frequently detected in surface and groundwater, and polar organic contaminants, such as MTBE, are difficult to remove from drinking water by activated carbon adsorption processes, in part because natural organic matter (NOM) competes with MTBE for adsorption sites. Unlike activated carbons, high-silica zeolites are adsorbents with well-defined pore sizes. From a drinking water treatment perspective, it may be possible to select high-silica zeolites that permit the adsorption of smaller organic contaminants while preventing the adsorption of competing NOM components of larger molecular size. MTBE isotherm experiments were conducted using a matrix of high-silica zeolites with different pore sizes, exchangeable cations, and hydrophobicities (Si/Al ratios). Single-solute isotherm tests were conducted in ultrapure water at pH 7.2. The adsorption capacities of the high-silica zeolites were compared to those of three GACs and a carbonaceous resin. Additional isotherm studies were conducted to determine the effects of co-adsorbing and preloaded NOM on MTBE adsorption from Tar River water (Greenville, NC). Single-solute isotherm data and isotherm data in the presence of competing NOM showed that high-silica zeolites (ZSM-5 and Mordenite) and the carbonaceous resin exhibited MTBE adsorption capacities that exceeded those of activated carbons. However, the beta zeolite was not effective for MTBE adsorption from aqueous solution, and MTBE adsorption was negligible on Y-zeolites. The Si/Al ratio and exchangeable cation of the tested ZSM-5 zeolites had no effect on MTBE adsorption capacity. For one ZSM-5 zeolite, co-adsorbing NOM had no effect on MTBE adsorption capacity, but for another zeolite with the same pore structure, a 55% reduction in MTBE adsorption capacity relative to the single-solute isotherm data was measured. Whether or not high-silica zeolites (cost: $7/lb and up) or carbonaceous resins (cost: ~$35/lb) are cost-effective adsorbents for MTBE removal will depend on the ease with which the adsorbents can be regenerated relative to activated carbon (cost: ~$1-2/lb). Includes 13 references, tables, figures.