AWWA ACE59831

AWWA ACE59831 Adsorption of MTBE on Alternative Adsorbents
Conference Proceeding by American Water Works Association, 06/17/2004

Rossner, Alfred; Knappe, Detlef R.U.

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Methyl tertiary-butyl ether (MTBE) is frequently detected in surface and groundwater, and polarorganic contaminants, such as MTBE, are difficult to remove from drinking water by activatedcarbon adsorption processes, in part because natural organic matter (NOM) competes withMTBE for adsorption sites. Unlike activated carbons, high-silica zeolites are adsorbents withwell-defined pore sizes. From a drinking water treatment perspective, it may be possible to selecthigh-silica zeolites that permit the adsorption of smaller organic contaminants while preventingthe adsorption of competing NOM components of larger molecular size.MTBE isotherm experiments were conducted using a matrix of high-silica zeolites with differentpore sizes, exchangeable cations, and hydrophobicities (Si/Al ratios). Single-solute isotherm testswere conducted in ultrapure water at pH 7.2. The adsorption capacities of the high-silica zeoliteswere compared to those of three GACs and a carbonaceous resin. Additional isotherm studieswere conducted to determine the effects of co-adsorbing and preloaded NOM on MTBEadsorption from Tar River water (Greenville, NC).Single-solute isotherm data and isotherm data in the presence of competing NOM showed thathigh-silica zeolites (ZSM-5 and Mordenite) and the carbonaceous resin exhibited MTBEadsorption capacities that exceeded those of activated carbons. However, the beta zeolite was noteffective for MTBE adsorption from aqueous solution, and MTBE adsorption was negligible onY-zeolites. The Si/Al ratio and exchangeable cation of the tested ZSM-5 zeolites had no effect onMTBE adsorption capacity. For one ZSM-5 zeolite, co-adsorbing NOM had no effect on MTBEadsorption capacity, but for another zeolite with the same pore structure, a 55% reduction inMTBE adsorption capacity relative to the single-solute isotherm data was measured. Whether ornot high-silica zeolites (cost: $7/lb and up) or carbonaceous resins (cost: ~$35/lb) are cost-effectiveadsorbents for MTBE removal will depend on the ease with which the adsorbents canbe regenerated relative to activated carbon (cost: ~$1-2/lb). Includes 13 references, tables, figures.