Application of GC-MS and GC-AED to the evaluation of by-products formed by solar photo-fenton degradation of Methyl tert-butyl ether in water

Abstract

This study describes the application of solar photocatalysis by photo-Fenton reaction to the degradation of methyl tert-butyl ether (MTBE) in aqueous solutions at a pilot scale in a compound parabolic collector (CPC) reactor. The results show a rapid and complete oxidation of MTBE after only 35 min of treatment. However, 54% remains to be mineralized after that time, almost compleste mineralization (97%) being reached only after 155 min of treatment. This indicated the formation of a large quantity of transformation products (TPs) more resistant to degradation than the parent compound. Identification and quantification of six TPs (tert-butyl formate, tert-butyl alcohol, acetone, methyl acetate, isobutene and formaldehyde) were possible with the combined use of two complementary techniques: GC-MS and GC-AED, both coupled to a purge-and-trap system. Ionic chromatography (IC) was used for the identification of organic ions usually present in the last stages of the mineralization process. Only formate ions were detected and these may be considered as the last step in the oxidation process previous to total mineralization. A degradation pathway, fixing the most critical compounds in terms of kinetic degradation, was proposed.

Keywords:

• Methyl tert-butyl ether
• Photo-Fenton
• By-products
• Gas chromatography-Mass spectrometry
• Atomic emission detector
• Photodegradation

Acknowledgement

This work was supported by the CICYT, Project No. PPQ2001–1805–CO3–03.