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May 2000
Method removes gas additive MTBE
from tainted water
WESTVILLE, Ind. – A Purdue University chemist has developed an experimental method that could be used to remove the gasoline additive MTBE from polluted ground water.
Reynaldo Barreto, an associate professor of chemistry at Purdue's North Central campus in Westville, will present a paper about the work on Wednesday, March 29, during a meeting of the American Chemical Society in San Francisco.
MTBE, or methyl tertiary butyl ether, is a chemical compound added as an "oxygenator" to make gasoline burn cleaner and reduce air pollutants. However, the chemical has become a potential water pollution problem because it is water soluble and is difficult to remove from the environment. It gets into ground water from leaky underground gasoline storage tanks.
"It has a very distinctive odor, and it is detectable at extremely low levels," Barreto says. "If I were to dilute an ounce of MTBE into a ton of water, you would be able to smell the MTBE."
Moreover, none of the conventional methods for removing pollutants from ground water will work effectively for MTBE. Consequently, although it is unclear whether the compound poses serious health dangers in the concentrations found in ground water, contamination has become a concern to communities across the nation and officials are searching for other oxygenators as replacements for MTBE in gasoline.
Barreto's technique for removing MTBE involves exposing tainted water to high-energy ultraviolet rays, which eventually turns the compound into carbon dioxide. To make the reaction possible, oxygen is bubbled into the water and the common catalyst titanium dioxide — an ingredient of white paint – is added to the water.
"After a couple of hours I can eliminate the bulk of the MTBE," says Barreto, who has been working on the method for about nine years. "But the technique that I've developed at this point has never been tried in a commercially viable way.
"I have shown it to a number of engineers and they've all said, 'This isn't cost effective because it takes too long,' to which my response is, as compared to what? It's faster than what we have now, which is nothing."
Details about the technique were published in the journal Water Research in 1995. The work to be discussed at the March meeting will focus on the technique's use in removing two possible MTBE replacement compounds from water. Those possible alternatives to MTBE are ethyl tertiary butyl ether, or ETBE, and tertiary amyl methyl ether, or TAME. However, their safety has yet to be determined, Barreto says.
"Rather than trying to develop techniques after compounds have contaminated ground water, why not try to figure it out now?" Barreto says. "MTBE was put into gasoline before anybody knew anything about it."
Data indicate that his technique is slightly less effective in removing the two possible alternatives from water than it is in removing MTBE from water. He currently is working to prove that the method also turns ETBE and TAME into carbon dioxide.
Source: Reynaldo Barreto, (219) 785-5475, rbarreto@purduenc.edu
Writer: Emil Venere, (765) 494-4709, evenere@purdue.edu
Purdue News Service: (765) 494-2096; purduenews@purdue.edu
Related Web site:
American Chemical Society
NOTE TO JOURNALISTS: Copies of the research paper referred to in this news release are available from Emil Venere at the Purdue News Service, (765) 494-4709.
ABSTRACT
Photocatalytic Destruction of Ethyl t-Butyl Ether (ETBE)
and t-Amyl Methyl Ether (TAME)
Reynaldo D. Barreto, Phillip V. Ban, Chris Chavis
The recent requirements for octane enhancers in several states have resulted in an increase in the production of water soluble organic fuel additives. Compounds such as methyl tert-butyl ether (MTBE) and tert-butyl alcohol (TBA) have become common additives in many grades of gasoline. Other compounds including ethyl tert-butyl ether (ETBE), and tert-amyl methyl ether (TAME) have also shown promise as octane enhancers. As these compounds find their way into more grades of gasoline, it becomes almost inevitable that they will become involved in ground water contamination through a fuel spill. While compounds such as MTBE and TBA have proven to be difficult to treat economically by conventional means, they are readily degraded photocatalytically. Previous work has shown that both MTBE and TBA can be photocatalytically degraded using TiO2 in a batch slurry process. Both of the processes were found to initially be pseudo first order in nature, yielding reaction rates of 1.2 X 10-3 s-1 for MTBE and 2.34 X 10-4 s-1 for TBA. Both MTBE and TBA were found to ultimately be converted to CO2 at the end of four hours, with greater than 90 percent efficiency. This work applies to photocatalytic batch slurry process used on MTBE and TBA to the degradation of ETBE and TAME. The results clearly show that both ETBE and TAME are also susceptible to this mode of degradation.
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