No description available.

The Zeeman splitting of nuclear quadrupole resonances is discussed and a formula given for the split resonance frequencies as a function of the angle between the perturbing magnetic field and the symmetry axis of the crystalline electric field. The direction of this axis in the crystal can be found If the electric field does not have cylindrical symmetry then for certain angles the spectrum becomes simplified and the directions of the three principal axes of the electric field gradient tensor can be found as well as the degree of asymmetry of the electric field. These resonances are observed with the aid of a super-regenerative oscillator. A brief description of its operation is given as well as some signal to noise ratio considerations for various methods of detection of the resonances. The spectrometer used is described. The Zeeman spectra of the nuclear quadrupole resonances of Br⁸¹ in single crystals of Zn(BrO₃)₂ .6H₂O and Co(BrO₃)₂.6H₂O are observed. The accuracy of the observations is discussed and the conclusion is reached that within the error of the experiment the crystalline electric fields have cylindrical symmetry with four different directions of the symmetry axes in the crystal. They are parallel to the{1,1,1} crystal axes. The crystals have cubic structure. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

S-Nitrosothiols have been found to undergo nucleophilic attack by the hydroperoxide anion to effect electrophilic nitrosation of the nucleophile. Peroxynitrite anion is formed in almost quantitative yields and the kinetics of the reaction examined, confirming attack through the deprotonated form of hydrogen peroxide. Conversely, under slightly acidic conditions peroxynitrous acid, the neutral form of peroxynitrite, has been shown to nitrosate an excess of thiol in an indirect pathway. Initially two moles of thiol are oxidised to the corresponding disulfide with the concomitant production of nitrite. Under mildly acidic conditions nitrous acid is formed which can then nitrosate excess thiol present. The reaction of a 2;1 excess of thiol over peroxynitrous acid has been shown to generate nitrous acid, which remains relatively stable, as there is no thiol remaining due to its oxidation to the disulfide. At higher acidities an additional source of nitrosation is uncovered which is explained in the terms of the formation of a protonated from of peroxynitrous acid with analogies toward the nitrous acidium ion. A comparison of the antioxidant potential of S-nitrosothiols versus thiols has also been examined using the powerful oxidant potassium bromate. Complex kinetic traces were generated but evidence was obtained which showed that S-nitrosothiols have enhanced antioxidant potential over thiols due to the nitroso moiety. The alkaline hydrolysis of S-nitrosothiols was also investigated with attack of the hydroxide ion postulated to proceed via nucleophilic attack on the sulfur atom of S-nitrosothiols. Also the reaction between S-nitrosothiols and phenolic compounds was found to proceed through different mechanisms depending on the ring substituents on the phenol.

Ozone is a powerful oxidant and disinfectant used in potable wastewater reuse to destroy specific harmful compounds, including pharmaceuticals, personal care products and endocrine disrupting compounds. Ozonation also increases the biodegradability of recalcitrant organic compounds and inactivates disease-causing microbes. However, bromate, a regulated possible human carcinogen can form when bromide is present due to natural or industrial sources. Pilot-scale testing on wastewater treatment plant effluent with high bromide concentrations showed that the addition of preformed monochloramine could reduce bromate formation by as much as 97%. Monochloramine addition was able to keep concentrations below the U.S. Environmental Protection Agency Maximum Contaminant Level of 10 µg/L while exceeding 3-log or 99.9% virus removal credit. Preforming monochloramine in separate carrier water prior to addition upstream of ozonation eliminated the potential for disinfection byproduct formation when monochloramine is formed in the main water flow. This also allowed for the mechanisms of bromate suppression by monochloramine to be examined without the influence of reactions between chlorine and dissolved organic matter present. This research can help increase the application of ozonation in water reuse. / MS / Ozone is a powerful oxidant and disinfectant used in potable wastewater reuse to destroy specific harmful compounds, including pharmaceuticals, personal care products and endocrine disrupting compounds. Ozonation also increases the biodegradability of recalcitrant organic compounds and inactivates disease-causing microbes. However, bromate, a regulated possible human carcinogen can form when bromide is present due to natural or industrial sources. Pilot-scale testing on wastewater treatment plant effluent with high bromide concentrations showed that the addition of preformed monochloramine could reduce bromate formation by as much as 97%. Monochloramine addition was able to keep concentrations below the U.S. Environmental Protection Agency Maximum Contaminant Level of 10 µg/L while exceeding 3-log or 99.9% virus removal credit. Preforming monochloramine in separate carrier water prior to addition upstream of ozonation eliminated the potential for disinfection byproduct formation when monochloramine is formed in the main water flow. This also allowed for the mechanisms of bromate suppression by monochloramine to be examined without the influence of reactions between chlorine and dissolved organic matter present. This research can help increase the application of ozonation in water reuse.

No description available.

No description available.

Pelo uso da técnica biamperométrica modificada, pode-se determinar 35 ppb de íons iodato e 70 ppb de íons iodeto em água do mar; iodeto é determinado após sua oxidação a iodato com água de bromo no intervalo de pH entre 2,5 e 3,5 (o excesso de bromo é eliminado pelo aquecimento). Um estudo sistemático de pH foi efetuado para a elaboração do estudo de oxidação de íons iodeto a iodato com água de bromo, assim, como a oxidação de íons iodeto com água de bromo em várias temperaturas. Pode ser determinado 35 ppb de iodato em água do mar com %S de 3,9 e 70 ppb de íons iodeto em água do mar com %S de 5,8. O método proposto pode ser utililizado na determinação de íons iodato em sal de cozinha obtendo-se %S de 1,5. Por esta técnica também pode-se determinar íons bromato em farinha com melhores resultados em relação a volumetria. A análise de íons bromato, via biameprometria, pode ser efetuada por duas maneiras: diretamente na suspensão de farinha e por extração com Zn++/OH-, sendo que no primeiro caso pode-se determinar 15,2 ppm de íons bromato com %S de 7,00 e no segundo caso há necessidade de se utilizar um fator de correção, podendo-se chegar a concentrações de ppb. / Using the modified biamperometria technique, one can determine 35 ppb IO3- and 70 ppb I- is determined after its oxidation to IO3- with bromine in a range of pH between 2,5 - 3,5 (the excess of bromine is eliminated at 50º C). A sistematic study of pH for the oxidation of I- to IO3- was done as well for the oxidation of I- with bromine in a range of temperature. 35 ppb IO3- in sea water can be determined with accuracy of 3,9%; 70 ppb I- in sea water can be determined with accuracy of 5,8%. This method can be used for the determination of IO3- in kitchen salt in with accuracy of 1,5%. BrO3- in flours can be determined by the some technique with better results in comparison with the volumetric classical methods. The analysis of BrO3- in flours by the modified biamperometry can be made through two ways: directly in the suspension of the flours in water and by extraction with Zn++/OH-. By the first one can determine 15,2 ppm BrO3- with 7,00% of accuracy; by the second way one need to use a factor for correction, for determination of ppb level.

Pelo uso da técnica biamperométrica modificada, pode-se determinar 35 ppb de íons iodato e 70 ppb de íons iodeto em água do mar; iodeto é determinado após sua oxidação a iodato com água de bromo no intervalo de pH entre 2,5 e 3,5 (o excesso de bromo é eliminado pelo aquecimento). Um estudo sistemático de pH foi efetuado para a elaboração do estudo de oxidação de íons iodeto a iodato com água de bromo, assim, como a oxidação de íons iodeto com água de bromo em várias temperaturas. Pode ser determinado 35 ppb de iodato em água do mar com %S de 3,9 e 70 ppb de íons iodeto em água do mar com %S de 5,8. O método proposto pode ser utililizado na determinação de íons iodato em sal de cozinha obtendo-se %S de 1,5. Por esta técnica também pode-se determinar íons bromato em farinha com melhores resultados em relação a volumetria. A análise de íons bromato, via biameprometria, pode ser efetuada por duas maneiras: diretamente na suspensão de farinha e por extração com Zn++/OH-, sendo que no primeiro caso pode-se determinar 15,2 ppm de íons bromato com %S de 7,00 e no segundo caso há necessidade de se utilizar um fator de correção, podendo-se chegar a concentrações de ppb. / Using the modified biamperometria technique, one can determine 35 ppb IO3- and 70 ppb I- is determined after its oxidation to IO3- with bromine in a range of pH between 2,5 - 3,5 (the excess of bromine is eliminated at 50º C). A sistematic study of pH for the oxidation of I- to IO3- was done as well for the oxidation of I- with bromine in a range of temperature. 35 ppb IO3- in sea water can be determined with accuracy of 3,9%; 70 ppb I- in sea water can be determined with accuracy of 5,8%. This method can be used for the determination of IO3- in kitchen salt in with accuracy of 1,5%. BrO3- in flours can be determined by the some technique with better results in comparison with the volumetric classical methods. The analysis of BrO3- in flours by the modified biamperometry can be made through two ways: directly in the suspension of the flours in water and by extraction with Zn++/OH-. By the first one can determine 15,2 ppm BrO3- with 7,00% of accuracy; by the second way one need to use a factor for correction, for determination of ppb level.

Ozonation is used as an alternative disinfection process to chlorination but unfortunately has a potential of oxidizing bromide, a natural component of water sources, to bromate. Bromate is a possible carcinogen with a maximum contaminant level of 10 ppb. To understand bromate formation in full-scale systems, a comprehensive study was conducted at the Moorhead Water Treatment Plant (WTP). Bromide concentrations in source waters were monitored. Water samples from locations in the ozonation chambers were collected and analyzed for bromate and other parameters. Results showed that bromate formation was increased through increases in pH, bromide, and ozone dose during high temperatures and was decreased by increases in organics. The impact of the bromate influential parameters was minimized at low temperatures. To assist Moorhead WTP on developing bromate control strategies, a modeling approach was adopted to predict bromate formation at various operational conditions using temperature, pH, ozone dose, bromide, and TOC. / MWH Global, AWWA Scholarship / American Water Works Association (AWWA), Minnesota and North Dakota sections / North Dakota Water Resources Research Institute / Department of Civil Engineering, North Dakota State University

A recent study at the Moorhead water treatment plant (MWTP) determined that bromate formed during ozone disinfection and, at times, exceeded the maximum contaminant level (MCL) of 10 parts per billion (ppb) in the summer months. Operational data showed that bromate formation was directly related to raw water bromide concentration and control of the ozone system. This study was conducted with the purpose of developing and implementing operational strategies to minimize bromate formation in the MWTP. Several operational changes, including selection of source water based on bromide concentration and controlling ozone addition in a manner that reduces the ozone dose used to achieve disinfection, were implemented and were effective at minimizing bromate formation in the ozone chambers. The bromate concentration in the finished drinking water was significantly reduced and only a few samples contained greater than 10 ppb bromate. / Moorhead Public Service / American Water Works Association