The oxidation reaction mechanisms of water soluble textile dyes amaranth (an azo dye), brilliant blue-R (a triaryl dye) and safranine-O (an azine dye) with oxidants- hypochlorite and chlorine dioxide, were investigated. The detailed kinetics of the reactions of the three dyes was studied under excess concentrations of the oxidant and other reagents. The depletion of concentration of the chosen dye, taken at low concentration was monitored using a Hi-Tech SF-61 DX2 double mixing micro volume stopped-flow apparatus. The hypochlorite initiated oxidations were investigated as function of varying concentration of oxidant and hydrogen ion, ionic strength and temperature. For the chosen dyes and reaction conditions, the depletion of dye followed pseudo first-order kinetics and the rate constants were estimated using KinetAsystTM software. All the three reactions had first-order dependence on the oxidant concentration, and the reaction rates increased by varied extent with increase in [H+]0. The role of acid in their reaction mechanisms was established. The kinetic data was analysed to evaluate the rate constants for the competitive pathways initiated by hypochlorite ion and hypochlorous acid. The overall second-order rate coefficients for the OCl- and HOCl initiated reactions were estimated for all the three reactions. Major oxidation products for the reactions were separated and characterized by 1H NMR and 13C NMR and GC-MS techniques and the stoichiometry was established. The energy parameters inclusive of Arrhenius factor, enthalpy, entropy and energy of activations for the oxidation of three dyes both by OCl- and HOCl species were estimated. Based on the experimental findings, the probable rate laws, mechanisms and reaction schemes were described. Simulations studies were conducted to validate the proposed mechanisms using SIMKINE2 computer programme. The rate of oxidation of safranine-O is greater than that of amaranth and brilliant blue-R with OCl- / HOCl reaction. Following similar protocol, the oxidations of the chosen dyes with chlorine dioxide were investigated by monitoring the depletion kinetics of dye as function of varying concentration of ClO2 and OH- ion, ionic strength and temperature. All the three dyes, exhibited pseudo first-order kinetics and the rate constants were estimated using KinetAsystTM software. All the three reactions had first-order dependence on the oxidant concentration at pH conditions 7.0, 8.0 and 9.0 suggesting that reaction mechanism remains unaltered with pH variation. The effect of hydroxide ion on the reaction rate revealed that it acts as catalyst. All the three reactions had first-order dependence on [OH-]0, when its concentration was low; but the order with respect to [OH-] decreased as [OH-] increased stoichiometry proportion to reactants. The catalytic constant for hydroxide catalysed reaction was estimated for all the three reactions. Kinetic salt effect experiments were conducted to identify the possible reaction species involved in the reactions. The major reaction products were characterized by 1H NMR, 13C NMR and GC-MS techniques. The stoichiometry ratios were established and energy parameters were estimated. The rate laws and probable reaction mechanisms were proposed and appropriate reaction schemes for all the reactions were described. The elucidated mechanisms were confirmed by simulation studies using SIMKINE2 software. At neutral pH the rate of oxidation of amaranth is greater than safranine-O and brilliant blue-R, and brilliant blue R being the slowest. / Thesis (Ph.D.)-University of KwaZulu-Natal, Westville, 2010.

No description available.

No description available.

No description available.

The central segment of the Taupo Volcanic Zone (TVZ) is one of the world’s most productive areas of silicic volcanism and geothermal activity. Rhyolites largely predominate the eruptive output in the central TVZ, with only minor basalts, andesites and dacites. The rhyolites show diversity in composition, and form a compositional continuum between two end-member types (R1 and R2), as suggested in previous studies. In this thesis I present results from a quartz- (and rare plagioclase-) hosted melt inclusions study, focussing on the volatile concentration (i.e. H2O, Cl, F, CO2) and their relative distribution between R1 and R2 rhyolites. The main objective is to add further constraints on the magmatic systems with regard to their contribution to the hydrothermal systems in the central TVZ. A comparative study between R1 and R2 melt inclusions show distinct volatile, fluid-mobile, and highly incompatible element compositions. Differences in the bulk volatile concentration of the parental magmas (i.e. basalts intruding the lower crust) are suggested to be at the origin of these volatile disparities. Further analysis on the volatile exsolution of R1 and R2 melts lead to the observation that the two rhyolite types exsolve a volatile phase at different stages in their magmatic history. From Cl and H2O concentrations, it is suggested that R1 magmas exsolve a vapour phase first, whereas R2 rhyolites more likely exsolve a hydrosaline fluid phase. These results have considerable implications for the magmatic contribution into the hydrothermal systems in the central TVZ, as differences in the composition of the resulting volatile phase may be expected. The hydrothermal systems in the central TVZ are subdivided into two groups based on their gas and fluid chemistry; and the current model suggests that there are two distinct contributions: a typical ‘arc’ system, with geochemical affinity with andesitic fluids, located along the eastern margin of the TVZ, and a typical ‘rift’ system, with geochemical affinity with rhyolitic/basaltic fluids, located along the central and/or western region of the TVZ. The addition of the new data on the rhyolitic melt inclusions, leads to a re-evaluation of the magmatic contribution into the hydrothermal systems, with a particular focus on B and Cl. The results indicate a more diverse variety of contributions to the meteoric water in the hydrothermal systems, and also show that the east-west distribution of ‘arc’ and ‘rift’ fluids is not a viable model for the central TVZ. This work emphasises that melt inclusion data and their volatile degassing history cannot be underestimated when characterising and quantifying the magmatic component in hydrothermal fluids. The melt inclusion data also provide further insight into the pre-eruptive magmatic plumbing systems and are particularly important from a hazard perspective. Included in the thesis is a detailed petrological analysis of rhyolite melt inclusions across the central TVZ and an interpretation that large silicic magma systems (in the TVZ) are typically comprised of multiple batches of magma emplaced at some of the shallowest depths on Earth. Tectonic activity is suggested to play an important role in triggering large caldera-forming eruptions as the evacuation of one magma batch could cause a regional-scale readjustment that is sufficient enough to trigger and allow simultaneous eruption of an adjacent melt batch.

The decommissioning of nuclear power stations will lead to the production of a number of contaminated components. The materials produced will consist of process and structural wasteforms. Before this waste can be disposed it will be necessary to obtain a full inventory of those radionuclides contained in those wastes. This will be necessary to ensure that the waste is handled in a suitable manner and that full information is available so that reliable risk assessment can be carried out on the proposed disposal site. A number of radionuclides have been highlighted as significant in terms if their halflife, terrestrial mobility and predicted levels in decommissioning wastes. A selection of these radionuclides have been investigated, and methods developed for their determination in concrete. It was a requirement of this work that the methods developed were robust and that the minimum detectable amount was below that of the de minimis of O.4Bq g-1.

Typescript. / Thesis (Ph. D.)--University of Hawaii at Manoa, 1979. / Bibliography: leaves 147-156. / Microfiche. / x, 156 leaves ill. (some col.) 29 cm

Thesis (Ph. D.)--University of Wyoming, 2007. / Title from PDF title page (viewed on Feb. 6, 2009). Includes bibliographical references.

Thesis (doctoral)--Lund University, 1997. / Added t.p. with thesis statement inserted.

Thesis (doctoral)--Lund University, 1997. / Added t.p. with thesis statement inserted.