Method development for the recovery of trace metals from unpreserved water samples

Tan, Wenshuai

Method development for the recovery of trace metals from unpreserved water samples

Tan, Wenshuai

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Publication Type:: Thesis
Issue Date:: 2019

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Field	Value	Language
dc.contributor.author	Tan, Wenshuai
dc.date.accessioned	2019-05-09T02:10:43Z
dc.date.available	2019-05-09T02:10:43Z
dc.date.issued	2019
dc.identifier.uri	http://hdl.handle.net/10453/133263
dc.description	University of Technology Sydney. Faculty of Engineering and Information Technology.	en_AU
dc.description.abstract	Water contamination by trace metals in natural and industrialised environments is a common phenomenon, the analysis of trace metals is therefore a very important process. Trace metal analysis is employed to assess the occurrence and concentration of contaminants thereby providing important data to protect our ecosystems and public health. During trace metal analysis, sample preservation is a critical requirement however it is also subject to numerous difficulties throughout the testing procedure. The major standard water testing methods to preserve trace metals (as adopted by the USEPA and APHA) use nitric acid (HNO3) which is added to water samples usually stored in polyethylene bottles. However, in some cases, samples are sent to laboratories unpreserved whereby significant amounts of trace metals may be lost due to being adsorbed in the inner walls of the plastic bottles, leading to a loss of metal concentration in the water samples. The analytical results of analysis could therefore be significantly lower than their true values. To provide a solution to this problem, this study is focused on the recovery of 19 trace metals – Al, Ag, As, Ba, B, Cd, Cr, Co, Cu, Hg, Mn, Mo, Ni, Pb, Sb, Se, Tl, V and Zn – from unpreserved water samples spiked with trace metals. First the thesis focuses on deionised (DI) water samples spiked with trace metals. Findings from this work with DI water samples have indicated that sample testing with 1% (v/v) nitric acid plus 0.01% (v/v) hydrochloric acid (HCl) for a 24-hour period enabled efficient re-extraction of 70-110% of trace metals from the tested water samples. However, mercury (Hg) did not yield high recovery results (around 56%) with this method although, with the addition of 10 mg/L Au solution, recovery of Hg was increased to about 70%. After DI water samples recovery testing, then the thesis focuses on the recovery of trace metals from unpreserved drinking water samples. Tap water samples were studied with this research method: 1% (v/v) nitric acid plus 1% (v/v) hydrochloric acid for a 24-hour period. This enabled efficient re-extraction of 70-110% of trace metals from the water sample. However, as with tap water sampling, mercury did not yield high recovery results with this method (around 66%) although, with the addition of 1 mg/L Au solution, the recovery of Hg was increased to about 78%. Therefore, it is highly recommended that acidified water samples – those containing 1% (v/v) nitric acid plus 0.01% (v/v) hydrochloric acid – are sent to the laboratory for testing whenever possible to guarantee greatest accuracy in trace metals analyses. If unpreserved tap water samples are received, 1% (v/v) nitric acid plus 1% (v/v) hydrochloric acid can be utilised to recover most trace metals, while 1 mg/L Au solution guarantees greatest accuracy when testing for mercury. Finally, the limitations of this study have been stated with recommendations for future studies and applications which might develop methods for the recovery of trace metals from unpreserved water samples.	en_AU
dc.format	Thesis (ME)
dc.language.iso	en_AU	en_AU
dc.relation	https://opus.lib.uts.edu.au/bitstream/10453/133263/2/02whole.pdf
dc.rights	info:eu-repo/semantics/openAccess
dc.rights	au.edu.uts.lib/ppc
dc.rights	The author owns the copyright in this thesis including all reproduction and reuse rights for the work. The work may not be altered without the permission of the copyright owner. Attribution is essential when quoting or paraphrasing from this thesis.
dc.subject	trace metal
dc.subject	public health
dc.subject	nitric acid
dc.subject	polyethylene
dc.subject	deionised water
dc.subject	hydrochloric acid
dc.title	Method development for the recovery of trace metals from unpreserved water samples	en_AU
dc.type	Thesis	en_AU
utslib.copyright.status	open_access

Abstract:

Water contamination by trace metals in natural and industrialised environments is a common phenomenon, the analysis of trace metals is therefore a very important process. Trace metal analysis is employed to assess the occurrence and concentration of contaminants thereby providing important data to protect our ecosystems and public health. During trace metal analysis, sample preservation is a critical requirement however it is also subject to numerous difficulties throughout the testing procedure. The major standard water testing methods to preserve trace metals (as adopted by the USEPA and APHA) use nitric acid (HNO3) which is added to water samples usually stored in polyethylene bottles. However, in some cases, samples are sent to laboratories unpreserved whereby significant amounts of trace metals may be lost due to being adsorbed in the inner walls of the plastic bottles, leading to a loss of metal concentration in the water samples. The analytical results of analysis could therefore be significantly lower than their true values. To provide a solution to this problem, this study is focused on the recovery of 19 trace metals – Al, Ag, As, Ba, B, Cd, Cr, Co, Cu, Hg, Mn, Mo, Ni, Pb, Sb, Se, Tl, V and Zn – from unpreserved water samples spiked with trace metals. First the thesis focuses on deionised (DI) water samples spiked with trace metals. Findings from this work with DI water samples have indicated that sample testing with 1% (v/v) nitric acid plus 0.01% (v/v) hydrochloric acid (HCl) for a 24-hour period enabled efficient re-extraction of 70-110% of trace metals from the tested water samples. However, mercury (Hg) did not yield high recovery results (around 56%) with this method although, with the addition of 10 mg/L Au solution, recovery of Hg was increased to about 70%. After DI water samples recovery testing, then the thesis focuses on the recovery of trace metals from unpreserved drinking water samples. Tap water samples were studied with this research method: 1% (v/v) nitric acid plus 1% (v/v) hydrochloric acid for a 24-hour period. This enabled efficient re-extraction of 70-110% of trace metals from the water sample. However, as with tap water sampling, mercury did not yield high recovery results with this method (around 66%) although, with the addition of 1 mg/L Au solution, the recovery of Hg was increased to about 78%. Therefore, it is highly recommended that acidified water samples – those containing 1% (v/v) nitric acid plus 0.01% (v/v) hydrochloric acid – are sent to the laboratory for testing whenever possible to guarantee greatest accuracy in trace metals analyses. If unpreserved tap water samples are received, 1% (v/v) nitric acid plus 1% (v/v) hydrochloric acid can be utilised to recover most trace metals, while 1 mg/L Au solution guarantees greatest accuracy when testing for mercury. Finally, the limitations of this study have been stated with recommendations for future studies and applications which might develop methods for the recovery of trace metals from unpreserved water samples.

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http://hdl.handle.net/10453/133263