Adsorption-desorption of arsenic species in river sediment, water and associated microplastics

Field	Value	Language
dc.contributor.author	Nguyen, Kien Thanh
dc.date.accessioned	2022-10-28T00:51:22Z
dc.date.available	2022-10-28T00:51:22Z
dc.date.issued	2022
dc.identifier.uri	http://hdl.handle.net/10453/162773
dc.description	University of Technology Sydney. Faculty of Engineering and Information Technology.	en_US.UTF-8
dc.description.abstract	Arsenic (As) is a ubiquitous toxic metalloid, and its pollution has been reported in soil, surface water, groundwater and sediment worldwide. Additionally, micro-plastics (MPs) are an emerging organic pollutant widely detected in different environments. So far, studies on the interfacial behaviour of As in the river sediment-water were limited. This PhD research, therefore, aims to explore the adsorption and desorption processes and interfacial behaviour of As in the contaminated water-sediment system. The kinetic and isotherm sorption models are used to estimate the sorption behaviours of As(III) and As(V), while various surface characterisation methods are applied to understand the interactions between As species with adsorbent surface and the transformation among As species. Firstly, the adsorption and desorption of As(III) on river sediment (RS) were investigated under various environmental conditions and sediment characteristics. Higher As(III) and As(V) adsorption on RS was found in acidic to neutral conditions and on smaller size fractions of sediment. The monolayer maximum surface adsorption (qm) of As(V) (210.0 mg/kg) was higher than that of As(III) (201.7 mg/kg). The FTIR results showed the changes in surface functional groups of river sediment before and after adsorption, indicating that Fe–O/Fe–OH, Si(Al)–O, –OH and –COOH functional groups were predominantly involved in As(III) and As(V) adsorption on sediment surface. Secondly, the adsorption of As(III) and As(V) on polystyrene (PS) and low-density polyethylene (LDPE) in deionized (DI) water and simulated river water (RW) conditions were investigated by using bead MPs. Physisorption was the main mechanism involved in the adsorption processes based on the isotherm modelling. Moreover, the interactions between As species and PS and LDPE mainly occurred on the carboxyl and hydroxyl groups of adsorbent surfaces, whilst electrostatic force and non-covalent interaction played an important role in the adsorption mechanism of As(III) and As(V) on PS and LDPE. Furthermore, the sorption behaviour of As(III) and As(V) was evaluated by using mixtures of sediment with PS or LDPE and DI water or RW. The amounts of As(III) and As(V) adsorbed in RW solution with the presence of PS and LDPE were lower than those in sediment only, suggesting that PS and LDPE may inhibit sediment adsorption of As(III) and As(V). The desorption process showed a positive impact of RW in the release of As(III) and As(V) into the water phase. This study provided valuable information on the sorption behaviour and mechanism of inorganic As species in the simulated river system.	en_US.UTF-8
dc.format	Thesis (PhD)
dc.language.iso	en_US	en_US.UTF-8
dc.relation	https://opus.lib.uts.edu.au/bitstream/10453/162773/2/02whole.pdf
dc.rights	info:eu-repo/semantics/openAccess
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.rights	au.edu.uts.lib/ppc
dc.title	Adsorption-desorption of arsenic species in river sediment, water and associated microplastics	en_US.UTF-8
dc.type	Thesis
utslib.copyright.status	open_access	*

Abstract:

Arsenic (As) is a ubiquitous toxic metalloid, and its pollution has been reported in soil, surface water, groundwater and sediment worldwide. Additionally, micro-plastics (MPs) are an emerging organic pollutant widely detected in different environments. So far, studies on the interfacial behaviour of As in the river sediment-water were limited. This PhD research, therefore, aims to explore the adsorption and desorption processes and interfacial behaviour of As in the contaminated water-sediment system. The kinetic and isotherm sorption models are used to estimate the sorption behaviours of As(III) and As(V), while various surface characterisation methods are applied to understand the interactions between As species with adsorbent surface and the transformation among As species. Firstly, the adsorption and desorption of As(III) on river sediment (RS) were investigated under various environmental conditions and sediment characteristics. Higher As(III) and As(V) adsorption on RS was found in acidic to neutral conditions and on smaller size fractions of sediment. The monolayer maximum surface adsorption (qm) of As(V) (210.0 mg/kg) was higher than that of As(III) (201.7 mg/kg). The FTIR results showed the changes in surface functional groups of river sediment before and after adsorption, indicating that Fe–O/Fe–OH, Si(Al)–O, –OH and –COOH functional groups were predominantly involved in As(III) and As(V) adsorption on sediment surface. Secondly, the adsorption of As(III) and As(V) on polystyrene (PS) and low-density polyethylene (LDPE) in deionized (DI) water and simulated river water (RW) conditions were investigated by using bead MPs. Physisorption was the main mechanism involved in the adsorption processes based on the isotherm modelling. Moreover, the interactions between As species and PS and LDPE mainly occurred on the carboxyl and hydroxyl groups of adsorbent surfaces, whilst electrostatic force and non-covalent interaction played an important role in the adsorption mechanism of As(III) and As(V) on PS and LDPE. Furthermore, the sorption behaviour of As(III) and As(V) was evaluated by using mixtures of sediment with PS or LDPE and DI water or RW. The amounts of As(III) and As(V) adsorbed in RW solution with the presence of PS and LDPE were lower than those in sediment only, suggesting that PS and LDPE may inhibit sediment adsorption of As(III) and As(V). The desorption process showed a positive impact of RW in the release of As(III) and As(V) into the water phase. This study provided valuable information on the sorption behaviour and mechanism of inorganic As species in the simulated river system.

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