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REMOVAL OF MTBE FROM WATER WITH ZEOLITES
Citation:
Kaiser*, P. M., R G. Ford*, J T. Wilson*, AND S. Shevade. REMOVAL OF MTBE FROM WATER WITH ZEOLITES. Presented at Battelle Conference, Monterey, CA, May 24 - 27, 2004.
Impact/Purpose:
To inform the public.
Description:
MTBE has impacted public drinking water wells from releases of gasoline making the water non-potable. MTBE is highly soluble in water, has a low volatility, does not adsorb strongly to soil, and is not thought to be easily biodegradable. Traditional methods of removing organics from water such as air stripping does not work due to MTBE's low volatility. Biological systems are too slow and chemical oxidation systems using ozone or hydrogen peroxide are expensive. Removal of MTBE by adsorption on activated carbon seems to be ineffective, because MTBE has a low affinity for organics.
Zeolites, alumino-silicate minerals, are used for adsorption of organics and also as catalysts. MTBE has been shown to undergo hydrolysis under acidic conditions. Zeolites are solid acids and were tested to remove MTBE from water to below the EPA's advisory limit. Investigations were done utilizing five zeolites: NH4+/ZSM-5, NH4+/FER, NH4+/Y, H+/Beta, and H+/Y in batch mode over a two week period to remove MTBE from water. Each bottle contained 2 g of zeolite and 25 mL of 1 mg/L MTBE solution. The extents of removal were 99%, 81%, 66%, 88%, and 96% respectively. The time zero samples showed that the MTBE removal was almost instantaneous.
Continuous flow column experiments were conducted using 1 g of NH4+/ZSM-5 contained within an empty bed volume of 2 mL. A solution of approximately 800 mg/L MTBE was passed through three columns at flow rates 0.25 mL/min, 0.33 mL/min, and 0.65 mL/min. At these flow rates, the effluent water MTBE concentrations stayed below the EPA's advisory limit of 20 mg/L for > 6000, 8000, and 1800 empty bed volumes respectively. Tertiary-butyl alcohol (TBA) did not appear in the effluent until after 1000 empty bed volumes. The zeolite NH4+/ZSM-5 is capable of removing MTBE from water by both adsorptive and reactive mechanisms.