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

Chemosphere (2009-12-05)
Sangchul Hwang, Scott G Huling, Saebom Ko
ABSTRACT

Fenton-driven oxidation of methyl tert-butyl ether (MTBE) (0.11-0.16mM) in batch reactors containing ferric iron (5mM) and hydrogen peroxide (H(2)O(2)) (6mM) (pH=3) was performed to investigate MTBE transformation mechanisms. Independent variables included the forms of iron (Fe) (Fe(2)(SO(4))(3).9H(2)O and Fe(NO(3))(3).9H(2)O), H(2)O(2) (6, 60mM), chloroform (CF) (0.2-2.4mM), isopropyl alcohol (IPA) (25, 50mM), and sulfate (7.5mM). MTBE, tert-butyl alcohol and acetone transformation were significantly greater when oxidation was carried out with Fe(NO(3))(3).9H(2)O than with Fe(2)(SO(4))(3).9H(2)O. Sulfate interfered in the formation of the ferro-peroxy intermediate species, inhibited H(2)O(2) reaction, hydroxyl radical (()OH) formation, and MTBE transformation. Transformation was faster and more complete at a higher [H(2)O(2)] (60mM), but resulted in lower oxidation efficiency which was attributed to ()OH scavenging by H(2)O(2). CF scavenging of the superoxide radical (()O(2)(-)) in the ferric nitrate system resulted in lower rates of ()O(2)(-) reduction of Fe(III) to Fe(II), ()OH production, and consequently lower rates of MTBE transformation. IPA, an excellent scavenger of ()OH, completely inhibited MTBE transformation in the ferric nitrate system indicating oxidation was predominantly by ()OH. ()OH scavenging by HSO(4)(-), formation of the sulfate radical (()SO(4)(-)), and oxidation of MTBE by ()SO(4)(-) 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.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Iron(III) nitrate nonahydrate, ≥99.999% trace metals basis
Sigma-Aldrich
Iron(III) nitrate nonahydrate, ≥99.95% trace metals basis
Supelco
Iron standard for AAS, analytical standard, 10.00 g/L Fe in nitric acid, traceable to BAM
Sigma-Aldrich
Iron(III) nitrate nonahydrate, BioReagent, suitable for cell culture
Sigma-Aldrich
Iron(III) nitrate nonahydrate, ACS reagent, ≥98%