DEGRADATION OF HYDROPHILIC AND HYDROPHOBIC CONTAMINANTS IN PERCARBONATE SYSTEMS
Almojil, Sattam Fahad
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Three topics related to the degradation of hydrophobic and hydrophilic compounds in percarbonate systems were studied. The first chapter provides a literature review and a brief description of the three treatment systems used in the present research: catalyzed hydrogen peroxide propagations (CHP), sodium percarbonate (PC), and base-activated persulfate (BAP) treatment systems. The second chapter presents a study of the degradation of contaminants by superoxide generated in PC systems, and further investigates the relationship between type of halogen and degree of halogenation in superoxide degradation rate for halogenated contaminants. Superoxide was responsible for the degradation of chlorinated compounds; and the rate of degradation by superoxide increased with greater degree of halogenation. Moreover, compounds with higher electronegativity were degraded more rapidly than those with lower electronegativity.Degradation of hydrophobic contaminants sorbed onto silica gel in PC, CHP, and BAP treatments are discussed in chapter three. The results demonstrate that chloroalkene and chloroalkane compounds were effectively degraded in CHP and PC systems, but not in BAP systems. Organochlorine insecticides and polychlorinated biphenyls were degraded in the CHP and BAP systems, but not in the PC systems. The hydrophobic herbicides diuron, bentazon, 2,4-D, and 2,4,5-T were degraded in CHP, BAP, and PC treatment systems with a degradation rate above the desorption rate of gas purge (GP) systems. However, atrazine was degraded only in CHP and BAP systems, indicating that superoxide does not react with atrazine. The fourth chapter covers changes in superoxide reactivity in aqueous systems with the addition of solids and minerals. The effects of 14 minerals and solids on the reactivity of superoxide in PC systems were investigated. The results showed increased superoxide reactivity in aqueous superoxide systems with the addition of solids or minerals due to increased surface area in the system. The results indicate that increased surface area—not the nature of the solid or mineral—is responsible for the increase in superoxide reactivity in aqueous PC systems. The linear relationship between the rate constants for HCA degradation and the actual solid or mineral surface areas demonstrates that providing surfaces in superoxide systems enhances its reactivity.