Fenton-like degradation of MTBE: Effects of iron counter anion and radical scavengers

Fenton-driven oxidation of methyl tert-butyl ether (MTBE) (0.11-0.16 mM) in batch reactors containing ferric iron (5 mM) and hydrogen peroxide (H2O2) (6 mM) (pH = 3) was performed to investigate MTBE transformation mechanisms, Independent variables included the forms of iron (Fe) (Fe-2(SO4)(3)center dot 9H(2)O and Fe(NO3)(3)center dot 9H(2)O), H2O2 (6, 60 mM), chloroform (CF) (0.2-2.4 mM), isopropyl alcohol (IPA) (25, 50 mM), and sulfate (7.5 mM). MTBE, tert-butyl alcohol and acetone transformation were significantly greater when oxidation was carried out with Fe(NO3)(3)center dot 9H(2)O than with Fe-2(SO4)(3)center dot 9H(2)O. Sulfate interfered in the formation of the ferro-peroxy intermediate species, inhibited H2O2 reaction, hydroxyl radical ((OH)-O-center dot) formation, and MTBE transformation. Transformation was faster and more complete at a higher [H2O2] (60 mM), but resulted in lower oxidation efficiency which was attributed to (OH)-O-center dot scavenging by H2O2. CF scavenging of the superoxide radical (O-center dot(2)-) in the ferric nitrate system resulted in lower rates of O-center dot(2)- reduction of Fe(III) to Fe(II), (OH)-O-center dot production, and consequently lower rates of MTBE transformation. IPA, an excellent scavenger of (OH)-O-center dot, completely inhibited MTBE transformation in the ferric nitrate system indicating oxidation was predominantly by (OH)-O-center dot, (OH)-O-center dot scavenging by HSO4-, formation of the sulfate radical ((SO4-)-S-center dot), and oxidation of MTBE by (SO4-)-S-center dot was estimated to be negligible. The form of Fe (i.e., counter anion) selected for use in Fenton treatment systems impacts oxidative mechanisms, treatment efficiency, and post-oxidation treatment of residuals which may require additional handling and cost. Published by Elsevier Ltd.