Doctor of Philosophy (PhD)
The first part of the thesis investigates the use of theoretical quantum calculations for the study of EPFRs as the initial and fundamental step in the formation of polychlorinated dibenzo-p-dioxin and dibenzofuran. The computational model comprised of density functionals (B3LYP, PBE1PBE, and M06) and two types of basis set namely: LANL2DZ for all atoms and GEN (LANL2DZ for metals and aug-cc-pVDZ for non-metals). Full mechanisms of EPFRs formation over (CuO)1-8, and aluminum oxide clusters were studied. The most stable intermediates and products have been determined and compared to available experimental data. In case of (CuO)1-8 clusters, the small clusters are more exoergic and thus more reactive than larger clusters. However, Al4O6 cluster is more exoergic than Al2O3 cluster. Bader charge analysis was used to examine the degree of electron transfer from phenolic species to metal cluster. A low degree of electron transfer was observed for small clusters (CuO - Cu5O5). There was essentially no electron transfer for the large clusters studied (Cu6O6 - Cu8O8), and this suggests that the catalytic sites are likely to be small “islands" of metal oxide clusters. These studies serve to refine proposed mechanisms for EPFRs formation in Prof. Dellinger laboratory. In the second part of the thesis, the dependency of EPFRs yield and their persistency on different CuO content on silica is reported. The EPFRs were generated through exposure of particles to adsorbate vapors of phenol, 2-chlorophenol, and 1,2-dichlorobenzene at 230 0C using a custom-made vacuum chamber. Adsorption resulted in the formation of surface-bound phenoxyl- and semiquinoine–type radicals with characteristic EPR spectra displaying a g-value ranging from ~2.0037 - 2.006. The highest EPFRs yield was observed for CuO concentrations between 1-3% in relation for 2-chlorophenol and phenol adsorption. The two longest lifetimes, 25 h and 23 h, were observed for phenoxyl-type radicals on 0.5% CuO and chlorophenoxyl-type radicals on 0.75% CuO, respectively. The EPFR-containing particle generated twice as much DMPO-OH compared to non-EPFR containing radical. On average, the ratio of OH radical concentration to the number of EPFRs was estimated to be 10:1 signaling a cyclic process.
Document Availability at the Time of Submission
Secure the entire work for patent and/or proprietary purposes for a period of one year. Student has submitted appropriate documentation which states: During this period the copyright owner also agrees not to exercise her/his ownership rights, including public use in works, without prior authorization from LSU. At the end of the one year period, either we or LSU may request an automatic extension for one additional year. At the end of the one year secure period (or its extension, if such is requested), the work will be released for access worldwide.
Kiruri, Lucy W., "Experimental and Computational Studies of Environmentally Persistent Free Radicals (EPFRs) Formation" (2013). LSU Doctoral Dissertations. 3316.