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.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 430 KB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 13 |
| Published : | 06/17/2004 |
