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BIFUNCTIONAL ALUMINUN: A PERMEABLE BARRIER MATERIAL FOR THE DEGRADATION OF MTBE
Citation:
Lien, H. AND R T. Wilkin*. BIFUNCTIONAL ALUMINUN: A PERMEABLE BARRIER MATERIAL FOR THE DEGRADATION OF MTBE. Presented at 27th Symp. of Waste Water Treatment Technology Annual Mtg, Taipei, TAIWAN, November 26 - 30, 2002.
Impact/Purpose:
To inform the public.
Description:
Bifunctional aluminum is an innovative remedial material for the treatment of gasoline oxygenates in permeable reactive barriers (PRBs). PRBs represent a promising environmental technology for remediation of groundwater contamination. Although zero-valent metals (ZVM) have been reported as effective remedial reagents for degradation of various contaminants such as chlorinated solvents, they are unable to degrade MTBE. The lack of suitable reagents limits the application of PRBs for the treatment of MTBE. Bifunctional aluminum, prepared by sulfating zero-valent aluminum with sulfuric acid, is an extension of ZVM technology. Bifunctional aluminum uses molecular oxygen, the most abundant, inexpensive, and environmentally compatible oxidant, to treat MTBE through a reductive activation process where oxygen is reductively activated to reactive oxygen radicals.
The use of bifunctional aluminum to degrade MTBE in the presence of dioxygen (O2) has been examined using batch systems. Primary degradation products were tert-butyl alcohol, tert-butyl formate, acetone, and methyl acetate. The initial rate of MTBE degradation exhibited pseudo first-order behavior and the half-life of reaction was less than 6 h. XPS analysis indicates the formation of sulfate at the surface of bifunctional aluminum. Concentration of surface sulfate varies linearly with increasing strength of sulfuric acid used during bifunctional aluminum preparation. Rate of MTBE degradation is a function of the concentration of surface sulfate. MTBE degradation rates increased by a factor of 2 as surface sulfate concentrations increased from 233 to 641 mole/m2. This relationship implies that sulfate at the surface of bifunctional aluminum particles acts as a reactive site.
The capability of bifunctional aluminum to degrade MTBE indicates that the reductive activation of dioxygen is a promising process for environmental remediation. This process occurs under reducing conditions. Therefore, it is possible to engineer a system where gasoline oxygenates can be oxidized through the reductive activation of dioxygen while chlorinated solvents can be reduced by taking advantage of reducing conditions. In other words, bifunctional aluminum has dual functionality of simultaneously decomposing oxidatively- and reductively-degradable contaminants. The ability to treat mixed contamination and the simple preparation procedures of bifunctional aluminum make it a promising remedial material for remediation of water contaminated with a wide array of contaminants.