| The fundamentals of the degradation of the fuel oxygenate Methyl tert-Butyl Ether (MTBE) in LRC aqueous solution using Fenton Reagent (FR) were investigated in this work. Initial MTBE concentrations ([MTBE]0) of 1.0 and 2.0 mg/L (11.4 and 22.7 muM, respectively) were treated with FR in batch reactors, in order to establish the extent of degradation and/or mineralization in a one-hour reaction period. The selected MTBE concentrations as well as other reaction conditions such as reduced concentrations of dissolved oxygen (DO < 0.01 mg/L) and absence of light, were used in order to simulate some of the actual conditions found in MTBE-contaminated aquifers.; When using a [FR]0:[MTBE]0 molar ratio of 10:1 and pH of approximately 3.0, the extent of MTBE degradation at the end of one hour was significantly higher (i.e., 90--99%) than its mineralization (i.e., 31.7% max.). Tert-butyl formate (TBF), tert -butyl alcohol (TBA), acetone and methyl acetate were identified and quantified as the major reaction intermediates. pH was a critical variable of this process. Experiments at acidic pH exhibited degradation efficiencies over 90% while those at neutral or close to neutral pH were below 10%. Additional experiments revealed that MTBE degradation efficiency peaked when FR was used as an equimolar mixture of its components (i.e., [H2O2] 0:[Fe2+]0 molar ratio = 1:1).; On the other hand, when the major MTBE intermediates described above were used as parent compounds and treated under the same conditions as those used for MTBE, their degradation efficiencies were proportional to their values of the second order rate constant of their reaction with OH· (k OH). From these studies it was also established that: (i) TBA is generated from both MTBE and TBF, (ii) acetone is formed independently from MTBE, TBF and TBA, and (iii) methyl acetate is formed exclusively from MTBE. These results were confirmed by monitoring different stages of reaction progress during further experiments using increasingly higher FR concentrations. A [FR]0:[MTBE]0 molar ratio of 20:1 was sufficient to achieve total transformation of an initial MTBE concentration of 2.0 mg/L, but complete MTBE mineralization was not achieved even at molar ratios as high as 200:1. |
