Thiosalt behaviour in aqueous media
Thesis (M.Eng.)--Memorial University of Newfoundland, 2008. Engineering and Applied Science Includes bibliographical references (leaves 100-103) Understanding the behaviour of thiosalts is important in acid mine drainage study as thiosalt oxidation results in pH depression. This research focuses on...
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ftmemorialunivdc:oai:collections.mun.ca:theses4/96036 2023-05-15T17:23:33+02:00 Thiosalt behaviour in aqueous media Vongporm, Yaovaluk. Memorial University of Newfoundland. Faculty of Engineering and Applied Science 2008 xviii, 148 leaves : ill. Image/jpeg; Application/pdf http://collections.mun.ca/cdm/ref/collection/theses4/id/96036 Eng eng Electronic Theses and Dissertations (15.94 MB) -- http://collections.mun.ca/PDFs/theses/Vongporm_Yaovaluk.pdf a2544295 http://collections.mun.ca/cdm/ref/collection/theses4/id/96036 The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. Paper copy kept in the Centre for Newfoundland Studies, Memorial University Libraries Thiosulfates--Biodegradation Thiosulfates Text Electronic thesis or dissertation 2008 ftmemorialunivdc 2015-08-06T19:22:11Z Thesis (M.Eng.)--Memorial University of Newfoundland, 2008. Engineering and Applied Science Includes bibliographical references (leaves 100-103) Understanding the behaviour of thiosalts is important in acid mine drainage study as thiosalt oxidation results in pH depression. This research focuses on a study of thiosalt kinetics under acidic, neutral and basic conditions in the temperature range typical of receiving ponds. The thiosalt studies performed in this research included a HSC equilibrium study, a study of freeze-thaw stability, and a thiosalt kinetic reactions study. -- The purpose of the HSC equilibrium study was to identify the major factors involved in thiosalt behaviour and to use this data to aid in later experimental design. The study of thiosalt equilibrium composition was performed using HSC Chemistry software and these results were statistically analysed by Design-Expert software. According to the analysis, the formation of thiosulphate depends upon its initial concentration, temperature, and pH. The formation of polythionate is also influenced by temperature, pH, and initial polythionate concentrations. Though these results were not unexpected, it was not anticipated that under equilibrium conditions the behaviour of thiosulphate and polythionate would be relatively independent of each other. -- As the freeze-thaw cycle has been shown to influence thiosalt speciation, a stability study was conducted to determine the stability of thiosalt species at different pHs. The thiosalts were found to be reasonably stable using a fast-freeze approach, where at pH 2, 4, and 7, most thiosalt concentrations changed within the range of ±6% after fast freezing in liquid nitrogen, storage in a freezer, and thawing in a water bath at 20°C just prior to analysis. -- Kinetic experiments were designed and conducted with the purpose of investigating thiosalt reaction kinetics under acidic, neutral, and basic conditions at variable temperatures. According to the results of this study, thiosulphate decomposed to trithionate, sulphate, and tetrathionate at pH 2. At pH 2 and 9, trithionate decomposed to sulphate, thiosulphate and tetrathionate only at 30°C; while at pH 4 and 7, trithionate decomposed to sulphate, thiosulphate and tetrathionate at temperatures of 15°C or greater. At pH 9, tetrathionate decomposed to thiosulphate, trithionate, and sulphate. In a mixture of thiosalt, thiosulphate and trithionate reacted as in the single species experiments, but tetrathionate was more reactive. Generally, the relative rates of decomposition of thiosulphate, trithionate, and tetrathionate were second or higher order. The decomposition rates increased with increasing initial thiosalt concentration and temperature (except for thiosulphate decomposition at pH 9 and 30°C). Thesis Newfoundland studies University of Newfoundland Memorial University of Newfoundland: Digital Archives Initiative (DAI) |
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Memorial University of Newfoundland: Digital Archives Initiative (DAI) |
op_collection_id |
ftmemorialunivdc |
language |
English |
topic |
Thiosulfates--Biodegradation Thiosulfates |
spellingShingle |
Thiosulfates--Biodegradation Thiosulfates Vongporm, Yaovaluk. Thiosalt behaviour in aqueous media |
topic_facet |
Thiosulfates--Biodegradation Thiosulfates |
description |
Thesis (M.Eng.)--Memorial University of Newfoundland, 2008. Engineering and Applied Science Includes bibliographical references (leaves 100-103) Understanding the behaviour of thiosalts is important in acid mine drainage study as thiosalt oxidation results in pH depression. This research focuses on a study of thiosalt kinetics under acidic, neutral and basic conditions in the temperature range typical of receiving ponds. The thiosalt studies performed in this research included a HSC equilibrium study, a study of freeze-thaw stability, and a thiosalt kinetic reactions study. -- The purpose of the HSC equilibrium study was to identify the major factors involved in thiosalt behaviour and to use this data to aid in later experimental design. The study of thiosalt equilibrium composition was performed using HSC Chemistry software and these results were statistically analysed by Design-Expert software. According to the analysis, the formation of thiosulphate depends upon its initial concentration, temperature, and pH. The formation of polythionate is also influenced by temperature, pH, and initial polythionate concentrations. Though these results were not unexpected, it was not anticipated that under equilibrium conditions the behaviour of thiosulphate and polythionate would be relatively independent of each other. -- As the freeze-thaw cycle has been shown to influence thiosalt speciation, a stability study was conducted to determine the stability of thiosalt species at different pHs. The thiosalts were found to be reasonably stable using a fast-freeze approach, where at pH 2, 4, and 7, most thiosalt concentrations changed within the range of ±6% after fast freezing in liquid nitrogen, storage in a freezer, and thawing in a water bath at 20°C just prior to analysis. -- Kinetic experiments were designed and conducted with the purpose of investigating thiosalt reaction kinetics under acidic, neutral, and basic conditions at variable temperatures. According to the results of this study, thiosulphate decomposed to trithionate, sulphate, and tetrathionate at pH 2. At pH 2 and 9, trithionate decomposed to sulphate, thiosulphate and tetrathionate only at 30°C; while at pH 4 and 7, trithionate decomposed to sulphate, thiosulphate and tetrathionate at temperatures of 15°C or greater. At pH 9, tetrathionate decomposed to thiosulphate, trithionate, and sulphate. In a mixture of thiosalt, thiosulphate and trithionate reacted as in the single species experiments, but tetrathionate was more reactive. Generally, the relative rates of decomposition of thiosulphate, trithionate, and tetrathionate were second or higher order. The decomposition rates increased with increasing initial thiosalt concentration and temperature (except for thiosulphate decomposition at pH 9 and 30°C). |
author2 |
Memorial University of Newfoundland. Faculty of Engineering and Applied Science |
format |
Thesis |
author |
Vongporm, Yaovaluk. |
author_facet |
Vongporm, Yaovaluk. |
author_sort |
Vongporm, Yaovaluk. |
title |
Thiosalt behaviour in aqueous media |
title_short |
Thiosalt behaviour in aqueous media |
title_full |
Thiosalt behaviour in aqueous media |
title_fullStr |
Thiosalt behaviour in aqueous media |
title_full_unstemmed |
Thiosalt behaviour in aqueous media |
title_sort |
thiosalt behaviour in aqueous media |
publishDate |
2008 |
url |
http://collections.mun.ca/cdm/ref/collection/theses4/id/96036 |
genre |
Newfoundland studies University of Newfoundland |
genre_facet |
Newfoundland studies University of Newfoundland |
op_source |
Paper copy kept in the Centre for Newfoundland Studies, Memorial University Libraries |
op_relation |
Electronic Theses and Dissertations (15.94 MB) -- http://collections.mun.ca/PDFs/theses/Vongporm_Yaovaluk.pdf a2544295 http://collections.mun.ca/cdm/ref/collection/theses4/id/96036 |
op_rights |
The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. |
_version_ |
1766113286481248256 |