REACTIVE OXYGEN SPECIES GENERATED IN THE PEROXYGEN SYSTEMS

Miao Yu

Three different topics related to peroxymonosulfate activation by subsurface minerals, soluble irons and iron chelate, and the reactive species generated in modified Fenton's systems with different concentrations of hydrogen peroxide were studied. Chapter one presented an introduction of theory for this research. In chapter two, peroxymonosulfate activation by four subsurface minerals and three soil fractions was investigated. Rates of peroxymonosulfate decomposition and generation rates of reactive species were studied in the presence of minerals. Hematite activated peroxymonosulfate system most effectively degraded the hydroxyl radical probe nitrobenzene. Use of the probe compound anisole in conjunction with scavengers demonstrated that both sulfate radical and hydroxyl radical are generated in mineral-activated peroxymonosulfate systems. The natural soil did not effectively promote the generation of oxidants; however, the SOM was found to promote the generation of reductants. In chapter three, peroxymonosulfate activation by iron (II) sulfate, iron (III) sulfate and iron (III)-EDTA was compared using nitrobenzene as an oxidant probe and hexachloroethane as a reductant probe, and the model groundwater contaminants perchloroethylene(PCE) and trichloroethylene(TCE). FeSO4, Fe2(SO4)3, and Fe (III)-EDTA were each able to effectively activate peroxymonosulfate to generate oxidants, but not to generate reductants. PCE and TCE loss in FeSO4- and Fe2(SO4)3-activated peroxymonosulfate was due to hydroxyl radical activity, while both hydroxyl radical and sulfate radical were responsible for PCE and TCE degradation in Fe (III)-EDTA-activated peroxymonosulfate. The fourth chapter investigated the degradation of the reactive species responsible for PCE and TCE by catalyzed hydrogen peroxide propagation (CHP) using concentrations of H2O2 in increments between 0.01M and 1 M. The addition of scavenger confirmed that the degradation of PCE and TCE was mainly due to hydroxyl radical. The TCE degradation with scavenger became higher when H2O2 concentrations increased, suggesting that more superoxide was generated with greater H2O2 concentration. Results similar to PCE and TCE degradation were obtained with nitrobenzene destruction, indicating that there was less hydroxyl radical in CHP systems with high H2O2 concentrations. Tetranitromethane degradation further confirmed that higher reactivity of superoxide was generated due to increased H2O2 concentrations in CHP systems.

REACTIVE OXYGEN SPECIES GENERATED IN THE PEROXYGEN SYSTEMS

Files and links (1)

Abstract

Metrics

Details