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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Optimization of a manufacturing process for atrazine with a focus on waste minimization

Mtyopo, Mteteleli Bethwell January 2004 (has links)
Chemical synthesis is not complete without waste treatment. There is no chemical process that does not produce waste. The untreated effluent discharged by chemical industries poses a major environmental concern. This dissertation describes the results of an investigation carried out on the formation of by-products (impurities) during the synthesis of atrazine by neutralization of the reaction mixture during the actual synthesis procedure, and prior to disposal using carbon dioxide or hydrochloric acid. The main objectives for the said investigation were: {u100083} To optimise the reaction parameters to obtain a higher yield and purity of atrazine. {u100083} To evaluate the use of carbon dioxide and hydrochloric acid to neutralise the reaction mixture. {u100083} To study the solids present in the effluent. Synthetic reactions were carried out in the presence of an organic solvent, methyl isobutyl ketone (MIBK). The synthesis of atrazine was optimised in terms of addition sequence and rates of amine reagents and base (proton acceptor) additions by means of bench scale reactions. It was found that addition of a neutralising step (hydrochloric acid or carbon dioxide) to neutralise the basic reaction mixture prior to and after addition of the secondary amine and the base minimizes the formation of by-products. Of particular importance in ensuring high yields and selectivity to the atrazine product was temperature control, pH control, reagent ratios, addition rates and mixing. The latter was important in view of the rapid reaction of amine/NaOH with cyanuric chloride, as well as the possible reaction of mono-i, the reaction intermediate, with IPA in cases of excesses of reagent. Under optimum conditions, an atrazine composition of >97% was achieved where the resultant product was well within stipulated product specifications.
2

Significance of environmentally realistic levels of selected contaminants to ecological performance of fish larvae: effects of atrazine, malathion, and methylmercury

Alvarez, Maria Del Carmen 28 August 2008 (has links)
Not available / text
3

Effects of atrazine on olfactory-mediated behaviors in Pacific lamprey (Entosphenus tridentatus)

Smith, April G. 07 February 2012 (has links)
Pacific lamprey (Entosphenus tridentatus) are experiencing population declines throughout their range. Xenobiotics could be an important risk factor for lamprey populations. Our goal was to establish if common herbicides, as used in forest management, could affect reproductive fitness. We determined that atrazine was a likely compound of greatest concern to lamprey populations. Using an odorant response behavioral assay we were able to demonstrate that environmentally relevant concentrations of atrazine caused a depressed response to adult lamprey holding tank effluent, likely pheromones. Atrazine also depressed their activity level; the number of times they crossed into the effluent arm after being treated with atrazine was significantly lower than controls. In addition, activity level post exposure to atrazine differed between adult life history stages, something which was not significantly different during control trials. Using an odorant detection assay, based on evaluating ventilation rate, we were able to show that environmentally relevant concentrations of atrazine caused a significant increase in ventilatory response to a repulsive odorant, a conspecific necromone. Through the detection study we also showed that lamprey,exposed to atrazine, had a slight increase in ventilatory response to odor from adult lamprey. If we are concerned about the decline in Pacific lamprey populations, then we should logically be concerned with their exposure to atrazine in the environment. / Graduation date: 2012

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