The kinetics of the electron transfer reaction U(IV) + T1(III) → U(VI) + T1(I) were examined in aqueous perchloric acid solution. The rate law was found to be of the form [ Formula omitted ] The two rate constants were identified with reaction paths involving activated complexes of the compositions (U.OH.T1)⁶⁺ and (U.O.T1)⁵⁺ , respectively. The corresponding heats and entropies of activation, evaluated from rate measurements over the temperature range 16 to 25°, are ΔH₁± = 24.6 kcal/mole, ΔH₂± = 21.7 kcal/mole, ΔS₁±= 16 e.u. and ΔS₂±= 7 e.u. The effect of ionic strength and the specific effects of various anions and cations on the rate were examined. The results suggest, but do not prove, that the reaction occurs through a single two-equivalent step rather than through successive one electron changes. The homogeneous oxidation of carbon monoxide by metal ions in aqueous solutions was studied. At temperatures below 80° only Hg²⁺ and MnO₄¯ were found to oxidize carbon monoxide. The ions Cu²⁺ , Ag⁺ , Hg₂²⁺ , Fe³⁺ , T1³⁺ and Cr₂O₇²¯, were inactive. Kinetic measurements of the reaction 2Hg²⁺+ CO + H₂O → Hg₂²⁺+ + CO₂ + 2H⁺ in dilute perchloric acid over the temperature range 26 to 54° yielded the rate law [ Formula omitted ] The activation parameters are ΔH± = 14.6 kcal/mole and ΔS± =-13 e.u. It is believed that the reaction proceeds by a mechanism which involves the insertion of CO between Hg²⁺ and a coordinated water molecule [ Formula omitted ] The oxidation of carbon monoxide by MnO₄¯ was found to proceed readily over the temperature range 28 to 50°. The rate law was found to be [ Formula omitted ] with ΔH± = 13 kcal/mole and ΔS± = -17 e.u., both substantially constant over the pH range 1 to 13. The rate determining step is considered to be the formation of hypomanganate MnO₄¯+ CO + H₂O → MnO₄³¯ + CO₂ + 2H which then undergoes further fast reactions to yield MnO₄²¯ in basic solution and MnO₂ in acid and neutral solutions. A remarkable feature of the latter reaction is its very marked sensitivity to catalysis by Ag⁺ and Hg²⁺ (but not by Cu²⁺, Cd²⁺, Fe³⁺, or T1³⁺ ). The rate law of the catalyzed path is, in each case, [ Formula omitted ] where M = Ag⁺ or Hg²⁺. For Ag⁺, k at 0° is 1.10 x 10⁵ M¯² sec¯¹ with ΔH± = 1.3 kcal/mole and ΔS± = -30 e.u. For Hg²⁺, k at 0° is 1.09 x 10³ M¯² sec¯¹ with ΔH± = 6.5 kcal/mole and ΔS± = -21 e.u. It is suggested that the remarkably high reactivities exhibited by carbon monoxide in these catalytic reactions are related to favourable oxidation paths involving intermediates such as [ Formula omitted ] / Science, Faculty of / Chemistry, Department of / Graduate

This work takes a closer look at ceria catalyst synthesis through micelle self-assembly. We compare surfactants, precursors, solvent systems, and doping. The surfactants are the building blocks upon which the ceria can crystallize. The samples are calcinated to test their thermal stability. Characterization is performed using pXRD as well as physisorption. The samples that exhibited a higher thermal stability were characterized to have a high surface area as well as low fluctuations in crystallite size, pore volume, and pore size. Ceria synthesized with cerium (III) nitrate hexahydrate and CTAB in a water:ethanol mixture using sodium hydroxide showed to be the most effective at providing a thermally stable product. Doping the catalyst with titanium increased the thermal stability significantly. Select samples were run in a variety of fuel to oxygen ratios to determine the best conditions in which we could perform partial methane oxidation to recuperate hydrogen gas. Most of the experiments show oxygen depletion with minor changes in other gas levels indicating that there is no oxidation occurring. Curiously the oxygen levels do decrease. There is a possibility that there is a reaction occurring initially at room temperature and being exacerbated with further temperature increase.

Biomass is a natural resource that is both abundant and sustainable. Its efficient utilization has long been the focus of research and development efforts with the aim to substitute it for fossil-based feedstock. In addition to the production of biofuels (e.g., ethanol) from biomass, which has been to some degree successful, its conversion to high value-added chemicals is equally important. Among various biomass conversion pathways, catalytic conversion is usually preferred, as it provides a cost-effective and eco-benign route to the desired products with high selectivities. The research of this thesis is focused on the conversion of biomass to various chemicals of commercial interest by selective catalytic oxidation. Molecular oxygen is chosen as the oxidant considering its low cost and environment friendly features in comparison with commonly used hydrogen peroxide. However, the activation of molecular oxygen usually requires high reaction temperatures, leading to over oxidation and thus lower selectivities. Therefore, it is highly desirable to develop effective catalysts for such conversion systems. We use kegging-type heteropoly acids (HPAs) as a platform for catalysts design because of their high catalytic activities and ease of medication. Using HPA catalysts allows the conversion taking place at relatively low temperature, which is beneficial to saving production cost as well as to improving the reaction selectivity. The strong acidity of HPA promotes the hydrolysis of biomass of giant molecules (e.g. cellulose), which is the first as well as the most difficult step in the conversion process. Under certain circumstances, a HPA combines the merits of homogeneous and heterogeneous catalysts, acting as an efficient homogeneous catalyst during the reaction while being easily separated as a heterogeneous catalyst after the reaction. We have successfully applied HPAs in several biomass conversion systems. Specially, we prepared a HPA-based bi-functional catalyst (Au/Cs2HPW12O40) that enabled the selective conversion of cellobiose to gluconic acid with a very high yield of 96.4% (Chapter II); we realized a direct oxidative conversion of cellulose to glycolic acid (yield of 49.3 %) in a water medium for the first time, by using a phosphomolybdic acid catalyst (chapter III); we found that a vanadium-substituted phosphomolybdic acid catalyst (H4PVMo11O40) is capable of converting various biomass-derived substrates to formic acid and acetic acid with high selectivity, and under optimized reaction conditions, high yield of formic acid (67.8%) can be obtained from cellulose (chapter IV); we discovered that the vanadium-substituted phosphomolybdic acids can also selectively oxidize glycerol, a low-cost by-product of biodiesel, to formic acid, and interestingly this conversion can be performed in highly concentration aqueous solution (glycerol: water = 50: 50), giving rise to exceptionally high conversion efficiency (chapter V). These results reveal that HPAs are useful and suitable catalysts for selective oxidation of biomass, and that the reaction pathway is largely determined by the type of addenda atom in the HPA catalyst. The optimization of the reaction conditions and processes in these systems are also discussed in this thesis.

The objectives of this project have been to characterise the biooxidation of an auriferous pyrite/arsenopyrite flotation concentrate, and to interpret laboratory batch and continuous pilot plant data in the light of the logistic model. Furthermore, the possibility of predicting continuous biooxidation plant performance from batch data was considered. The batch testing was carried out on five narrowly sized fractions of Fairview concentrate, as well as on the bulk concentrate. Extents of removal of iron, arsenic and sulphide-sulphur were described by the logistic equation and values of the kinetic parameters obtained. Maximum rates of removal of these components, predicted by the logistic parameters, correlated well with experimentally determined rates of removal obtained from the linear portions of the fractional removal versus time curves. Bibliography: pages 93-98.

The purpose of this study was: (1) to find the effect of temperature on the wet oxidation of chalcopyrite, pyrite, and copper sulfide over the biological and nonbiological range; (2) to determine the influence of ferrous and ferric iron and free oxygen(air) on the oxidation. The sulfide minerals studied were oxidized over a range of temperatures between 25° to 75° C. The optimum biological oxidation occurred near 35° C. The nonbiological oxidation was very slow at low temperatures but increased with increasing temperature. The effect of solutions used in leaching the various sulfides over the temperature range differred. A synthetic nutrient solution, containing only a source of phosphate and nitrogen, was more effective on the biological oxidation of pyrite than on copper sulfide at the optimum temperature. Tailings water, obtained from Bingham Canyon, Utah, was more effective on chalcopyrite over a long period of time than the synthetic nutrient. Ten times more chalcopyrite was oxidized at 70° C. than at 55° C. in a dilute solution of sulfuric acid. A dilute solution of ferrous sulfate had very little effect on the oxidation of the sulfides. Oxygen and ferric iron in oxidized tailings water were shown to affect the oxidation of chalcopyrite at 65° C. The ferric iron was reduced. In an atmosphere of nitrogen, ferrous iron in fresh tailings water was inactive on the oxidation of chalcopyrite. Oxygen is the primary oxidizing agent in the biological and nonbiological oxidation of sulfide minerals in the leaching process.

Implications of water chemistry on milk synthesis are not well described yet water is an important nutrient for dairy cattle. High mineral concentrations (>0.3 mg/kg Fe and others) may be associated with natural levels in ground water, contaminating sources, drought conditions, or storage systems. This study evaluated effects of added iron in bovine drinking water on milk composition (Ca, Cu, Fe, P) measured by inductively coupled plasma mass spectrometry and oxidative stability measured by thiobarbituric acid reactive substances assay for malondialdehyde (MDA), volatile chemistry and sensory analysis (triangle test). Prepared ferrous lactate treatments, corresponding to 0, 2, 5, and 12.5 mg/kg drinking water levels were given abomasally (10 L/d) to 4 lactating dairy cows over 4 periods (1 wk infusion/period) in a Latin square design. Milk was collected (d6 of infusion), processed (homogenized, pasteurized), and analyzed within 72 h of processing and 7 d of refrigerated storage. No differences in MDA (1.46�0.04 mg/kg) or iron (0.22�0.01 mg/kg) were observed in processed milk. Cross effects analysis (treatment*cow) showed significant differences in calcium, copper and iron (P < 0.05). Sensory differences (P < 0.05), in treatment vs. control, suggested iron from water sources contributes to milk flavor changes. A case study with high and low (0.99; 0.014 mg/kg) iron treatments revealed no significant differences (P > 0.05) in mineral composition (0.23�0.06 mg/kg Fe) or MDA (0.77�0.03 mg/kg) of raw milk. Iron added to milk causes changes in oxidation; high levels of iron in bovine drinking water may not have observed effects. / Master of Science in Life Sciences

The purpose of our study was to compare the effects of dietary soy protein and animal protein (casein) on plasma lipoprotein concentrations, and exercise induced oxidation in human subjects. Sixteen normocholesterolemic young men participated in 30 min of cycling at 70% VO2pk to induce plasma oxidation. Each subject then followed a 4wk dietary treatment replacing 33g animal protein in a self-selected solid food diet with either soy protein or casein. The exercise was then repeated and plasma lipoproteins and oxidation were compared. Soy protein and casein dietary treatments did not affect plasma concentrations. Our study therefore, suggests that in healthy normocholesterolemic individuals, 33g of soy protein does not effectively reduce plasma lipoprotein concentrations or exercise induced oxidation. / Master of Science

Fresh tannic acid (5%) (FTA), heated to 121C for 15 min (PTA), and the combination of FTA and phosphates (FPH) were vacuum tumbled with catfish fillets and compared to water tumbled fillets (CTL). Fillets treated with FTA or PTA had higher whiteness whereas all treated fillets had higher chroma values than CTL, resulting in a deeper yellow color fillet. Microbial shelf life (CTL, log CFU/g, APC) of FTA and PTA treated fillets was extended by two days, to11.8 d at 4C, but FPH fillets did not reach over 5 log CFU/g for 15 d of storage. Fat from FTA and PTA treated fillets had induction points (IP) of 4.0 and 3.4 h, respectively, whereas FPH and CTL samples had IP of 1.4 and 2.4 h. Thus, FPH seems to be the best antimicrobial treatment and FTA/PTA, the best antioxidant treatment.

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