No description available.

No description available.

Soluble manganese (Mn) presents a significant treatment challenge to many water utilities, causing aesthetic and operational concerns. Surface water treatment plants using ozonation followed by biofiltration are unable to apply free chlorine across the filter, a method used by many utilities for soluble Mn control. These facilities are vulnerable to periodic problems of elevated Mn in the finished water. Manganese-oxidizing bacteria (MOB) readily oxidize Mn in groundwater treatment applications, which normally involve pH values above 7.0.  However, the ability of MOB to facilitate Mn oxidation under lower pH conditions (6.2--6.3) often employed to optimize organics removal has not been demonstrated. Laboratory-scale biofilters were operated to evaluate the ability of MOB to accomplish soluble Mn control at a range of pH (6.3--7.3).  The biofilters were able to oxidize Mn at a pH as low as 6.3 at greater than 98% removal.  Ozonation by-product removal was also greater than 90% in all filter columns. Stress studies indicated that well-acclimated MOB can withstand variations in Mn concentration, hydraulic loading rate, and temperature typically found at surface water treatment plants, at least for relatively short (1-2 days) periods of time. Pilot studies demonstrated that there are unknown factors that affect MOB acclimation, and MOB may be present in full-scale biofilters already. MOB are difficult to identify with current biological analysis techniques and comprise small percentages of the total microbial population. MOB have demonstrated potential for use in surface water treatment plants, but further research is needed before this application is fully feasible. / Master of Science

The system in which atmospheric nitrogen succumbs to enter Nature's cycle has a yet proven evasive with respect to the actual chemical reactions. At present several types of systems are proposed but their chemical makeup is practically unknown.

Chromium(IV) has been of interest for some time because of its role as an intermediate in chromic oxidation reactions. Since there are not a great number of stable tetravalent chromium complexes known, and the use of such species as oxidizing agents has not been widely explored, the preparation, isolation and characterization of new stable tetravalent chromium species may allow chemists the opportunity to more fully understand the role which tetravalent chromium plays in oxidation reactions. The present study thus involves the synthesis of Cr(OC4H9)4 and other Cr(IV) derivatives and the use of Cr(OC4H9)4 in oxidative reactions with selected fluoridated alcohols. Interestingly, the reaction of fluoridated alcohols with Cr(OC4H9)4 or Cr(NEt2)3 was found to be a useful method for preparing products.

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

Thesis (Ph. D.)--University of Hong Kong, 2008. / Includes bibliographical references (leaf 185-187) Also available in print.

Thesis (MS)--Montana State University--Bozeman, 2009. / Typescript. Chairperson, Graduate Committee: Brian Bothner. Includes bibliographical references (leaves 63-71).

Orientador: Luiz Carlos da Silva Filho / Banca: Bruno José Gonçalves da Silva / Banca: Gilbert Bannach / Resumo: Os hidrocarbonetos se constituem na função mais simples da química orgânica. Mesmo sendo formados apenas por carbono e hidrogênio, esta classe é uma das mais diversas, onde se destacam os hidrocarbonetos alquil aromáticos (HAA) e os hidrocarbonetos aromáticos policíclicos (HAP). Por possuírem baixa reatividade e serem lipossolúveis, os HAA e HAP tendem a se acumular na natureza e nos tecidos vivos podendo levar a mutações genéticas e ao câncer. Funcionalizações oxigenadas nestes hidrocarbonetos ampliam suas aplicações industriais e auxiliam na sua remediação ambiental. A oxidação radicalar utilizando radicais hidroxila via TBHP (t-butil-hidroperóxido) é uma rota promissora devido à ausência de resíduos metálicos nocivos no processo. Paralelamente, o uso de metais do bloco-d, como o nióbio, como catalisadores heterogêneos, que são conhecidos por apresentarem boa estabilidade térmica, porosidade, maior superfície de contato e podendo ser recuperado e reutilizado, vem sendo descrito como bons catalisadores para a reação, permitindo rendimentos maiores e condições reacionais mais brandas. O nióbio tem despertado o interesse de muitos grupos de pesquisa devido às suas propriedades e aplicabilidades na metalurgia, supercondutores e supercapacitores, e na síntese orgânica. Este trabalho focou no estudo da aplicação do óxido de nióbio como catalisador heterogêneo em reações de oxidação de HAA e HAP usando o TBHP como oxidante. Diferentes variáveis reacionais como o solvente, a concen... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Hydrocarbons are the simplest function of organic chemistry. Although formed only by carbon and hydrogen, this class is one of the most diverse, in which the alkyl aromatic hydrocarbons (AAHs) and the polycyclic aromatic hydrocarbons (PAHs) stand out. These substances are mostly fossil raw materials widely used in industry in diverse applications. Because they have low reactivity and are liposoluble, AAHs and PAHs tend to accumulate in nature and in living tissues, leading to genetic mutations and cancer. Oxygenated functionalities in these hydrocarbons broaden their industrial applications and assist in their environmental remediation. Radical oxidation using hydroxyl radicals via TBHP (t-butylhydroperoxide) is a promising route due to the absence of noxious metal residues in the process. At the same time, the use of d-block metals, such as niobium, as heterogeneous catalysts, which are known to have good thermal stability, porosity, larger contact surface and be able to be recovered and reused, have been described as good catalysts for the reaction, allowing for higher yields and softer reaction conditions. Niobium has attracted the interest of many research groups because of its properties and applications in metallurgy, superconductors and supercapacitors, and in organic synthesis. This work focused on the study of the application of niobium oxide as a heterogeneous catalyst in oxidation reactions of AAHs and HAP using TBHP as oxidant. Many reactional variables like the s... (Complete abstract click electronic access below) / Mestre

Floodplain lakes are wetlands which receive flood waters from nearby rivers or other sources. Water samples were taken from floodplain lakes near the Illinois River, the Mississippi River, and the Cache River in Southern Illinois. Fluorescence in situ hybridization (FISH), spectrophotometry, and gene probes were used to investigate the effect of nutrient and chemical concentrations on the abundance of nitrifying bacteria; specifically ammonia-oxidizing Nitrosococcus and Nitrosomonadales and nitrite-oxidizing Nitrospira and Nitrobacter. Nitrosococcus was the dominant ammonia-oxidizing bacteria at each river system. Nitrospira and Nitrobacter had similar average abundances. Nitrosococcus abundances showed a significant positive correlation with nitrate (NO3-) (R2= 0.247, P=0.05, 95% confidence R2≥0.199) and a positive trend with nitrite (NO2-) (R2= 0.194, P=0.10, 90% confidence R2≥0.125). Nitrosomonadales abundance positively correlated with temperature (R2= 0.530, P=0.05, 95% confidence R2≥0.510). Nitrospira abundances positively correlated with ammonium (NH4+) (R2= 0.265, P=0.05, 95% confidence R2≥0.199), NO2- (R2= 0.372, P=0.05, 95% confidence R2≥0.199), and NO3- (R2= 0.482, P=0.05, 95% confidence R2≥0.199). None of the target bacterial abundances significantly correlated with pH or dissolved inorganic phosphate.