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Doctoral Dissertation Announcement
Candidate: Abraham Matthew Northup
Doctor of Philosophy
Title: Modified Fenton Oxidization of Hydrocarbon Contaminated Soils with CaO2: Microbial Survival and Surfactant Production
Dr. Daniel Cassidy, Chair
Dr. Duane Hampton
Dr. David Barnes
Dr. Anna Jelaso-Langerveld
Date: Friday, May 11, 2007 1:00 p.m. – 3:00 p.m.
1120 Rood Hall
The efficacy of CaO2 for use in Modified Fenton’s (MF) reactions was investigated in this study, with the goal of developing a CaO2–based MF oxidation technology for use in in situ chemical oxidation (ISCO). Traditionally, liquid H2O2 (HP) is used, and is injected into the subsurface in excess to ensure a sufficient radius of influence. CaO2 was investigated as an alternative source of H2O2 for MF reactions.
First, the rate of dissolution of powdered CaO2 and the yield of HP was investigated. Our results showed that the rate of dissolution of CaO2 and the corresponding yield of HP increases with decreasing pH. At a pH of 6 CaO2 is dissolved within 4 hours and the yield of HP is 82% of theoretical. The use of CaO2 as a source of H2O2 for the MF oxidation of tetrachloroethene (PCE), and 2-propanol, a hydroxyl radical scavenger, was used to demonstrate that the removal of PCE was due to oxidation by hydroxyl radicals. A comparison was made between HP and CaO2 based MF reactions with respect to PCE oxidation. The data indicate that CaO2 is able to sustain MF reactions longer and more efficiently than HP (i.e., less moles HP per mol PCE consumed). CaO2 buffered at pH 8 was also shown to degrade carbon tetrachloride, which indicates that reducing species (superoxide anion and perhydroxyl radical) were also formed.
A comparison was made between biological and Modified Fenton (MF) chemistry with respect to the effectiveness of treating hydrocarbon contaminated soil. The MF treatment was performed using both HP with Fe3+ and a CaO2 based oxidant to allow for comparisons between different MF oxidants. The MF treated systems had temporarily elevated surfactant concentrations with respect to the control and biologically treated soils, indicating surfactant production during chemical hydrocarbon oxidation. Enhanced total petroleum hydrocarbon (TPH) removal was observed as a result of MF treatment with hydrocarbon removal being greater with the CaO2 treatment relative to HP treatment. At the end of the treatment there was no considerable decrease in viable bacterial numbers between MF and biological treatments.