PhD Research - Marie Mina Mitani

Degree Conferred

Dissertation Title
Applications of a Microporous Diffuser Reactor System for MTBE Oxidation Using Ozone and Ozone/Hydrogen Peroxide

In this work, MTBE oxidation using ozone and ozone/hydrogen peroxide for the purpose of remediation was explored. In order to have a better understanding of the oxidation process, the kinetics of reaction was studied for MTBE with ozone and ozone/hydrogen peroxide. The reaction pathway to mineralization was also explored.

When using ozone as the oxidant in a water treatment system, mass transfer is of concern. Without proper mass transfer, ozone is lost in the overlying headspace and oxidation of the aqueous pollutants is not efficiently carried out. In order to improve mass transfer and increase ozone utilization, a microporous diffuser was implemented into a reactor system, and its capability for mass transfer was studied. A mathematical model for the reactor system was needed to calculate the mass transfer coefficient and also predict the mass transfer capabilities at varying gas and liquid flow rates. Flow characteristics of the reactor system were also studied in this system in order to fine tune the model, and this was performed with residence time distribution experiments.

MTBE oxidation was carried out in the microporous diffuser reactor system using ozone and ozone/hydrogen peroxide. Combining ozone and hydrogen peroxide produces the reactive hydroxyl radical, which is a powerful oxidant for the purpose of chemical remediation. If an excess of hydrogen peroxide is present, it quenches the hydroxyl radical making the process much less effective. Therefore, the microporous diffuser reactor system was tested for MTBE oxidation with varying ratios of ozone and hydrogen peroxide to find the most effective ratio.

Several different chemical oxidation technologies were combined into one reactor system in order to generate a high concentration of hydroxyl radicals. The reactor system had the ability to incorporate TiO2 , UV, ozone, and ozone/hydrogen peroxide. Different combinations of the technologies were tested for the oxidation of MTBE, with conclusions drawn from the experimental results as to which combination was the most effective.

MTBE oxidation and degradation was also studied using a gas phase catalytic system. Proprietary low cost catalysts with lower loadings of precious metals were tested for the lowest temperature conversion of MTBE to CO2 and H2O.