The compound 3,5,6-trichloro-2-pyridinol (TCPy), a metabolite of the broad-spectrum organophosphorous insecticide chlorpyrifos, is both more persistent and more water soluble than its parent compound. This difference, which allows TCPy to more readily leach into surface water and groundwater, has led to widespread contamination of TCPy in soils and aquatic environments. In this study, the degradation of TCPy by sulfate radicals was evaluated using zero valent ironactivated persulfate systems and heat activated persulfate system in aqueous media. Response surface methodology coupled with Box-Behnken design was applied in these studies to evaluate the effects of the independent variables on the mineralization of TCPy by both systems. In each system, the interactions, coefficients, and residuals of these variables were statically evaluated by Analysis of variance. Results indicate that both systems can effectively oxidized TCPy in water. While ZV/PS exhibited a high mineralization rate of TCPy up to 81.1%, TCPy was completely mineralized in heat activated PS system. The reaction kinetics of the degradation process were examined as functions of experimental parameters in each system and the result revealed that the oxidation of TCPy in both systems followed a pseudo-first-order model under all conditions tested. Radical scavenging tests indicated that sulfate radicals are the predominated species in zero valent iron activated persulfate system, whereas hydroxyl radicals are the predominated species in heat activated persulfate system. The presence of chloride, sulfate and phosphate anions showed negligible effects on TCPy oxidation by heat activated PS system. The degradation pathways of TCPy were proposed based on the products identified by GC-MS. Calculated ΔG values using density functional theory agreed with the proposed experimental pathway.
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Doctor of Philosophy (Ph.D.)
College of Sciences
Length of Campus-only Access
Doctoral Dissertation (Open Access)
Mogharbel, Roaa, "Thermo- and Zero-Valent Iron-Activated Persulfate Oxidation of 3,5,6-Trichloro-2-pyridinol in an Aquatic System" (2019). Electronic Theses and Dissertations. 6614.