- Title
- Interaction mechanisms between engineered nanoparticles (ENPs) and emerging contaminants (ECs) in water systems
- Creator
- Khan, Anwar Ul Haq
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2024
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- Engineered nanoparticles (ENPs) are chemically manufactured nanoparticles with approximate sizes ranging between 1 and 100 nm. ENPs are commonly used in textiles, electronics, renewable energy, agricultural chemicals, biomedical, healthcare, and environmental and industrial applications. The exponential growth of ENPs application has led to their widespread presence in the environment through natural or incidental processes. Among the many metal oxide-based ENPs, zinc oxide nanoparticles (ZnO-NPs) are among the five most commonly produced and employed ENPs in the fast-growing nanotechnology sector. ZnO-NPs are largely used in products such as nanomedicines, sunscreens and cosmetics, textiles, coatings, paints and nanopigments, ultraviolet (UV) filters, plastics and others. The approximate global annual production (550 − 33,400 tons/year) of ZnO-NPs leads to the wide application and release of ZnO-NPs from products, ending up in natural aquatic systems. Moreover, organic chemicals such as brominated flame retardants, BFRs and per- and polyfluoroalkyl substances (PFAS) in many commercial and consumer products result in their accumulation in environmental media such as water systems. The cooccurrence of ZnO-NPs and emerging contaminants (ECs, e.g. BFRs and PFAS) may promote the generation of complex compounds that are different from the parental compounds. It could occur through altering their physicochemical characteristics after interacting with each other. Environmental factors including pH, electrolytes, natural organic substances, and temperature may influence the interaction mechanisms. A detailed literature review was conducted to illustrate the occurrence and interactions of ENPs and BFRs such as polybrominated diphenyl ethers (PBDEs) in water systems and the generation of highly complex compounds in the environment (Chapter 2-published). Intermingled compounds (ENPs-BFRs) exhibit different behaviours than do parental ENPs or BFRs, but investigations of these compounds are currently lacking. A literature review also suggested that more research efforts are required for several ENPs and the factors influencing their fate and behaviour, such as the increasing introduction and release of ZnO-NPs into the environment as a consequence of their usage in commercial products. The impacts on the aquatic environment prior to and after interactions with coexisting organic pollutants are yet to be fully understood. To understand the fate and behaviour of ZnO-NPs in water systems, an additional review was conducted (Chapter 3). Sunscreens are a major source of ZnO-NPs released into environmental waters. In Chapter 4 (published), a simple and effective method for extracting ZnO-NPs from ZnO-based sunscreen products and wastewaters obtained from NSW, Australia, is used. The results are useful for understanding the presence of ZnO-NPs in sunscreens and wastewaters, which are critical for realistically investigating the fate and behaviour of these nanoparticles. The interactions between ZnO-NPs and ECs such as hexabromocyclododecane (HBCD) (Chapter 5-published), perfluorooctanoic acid (PFOA) (Chapter 6), and tetra-bromobisphenola-A (TBBPA) (Chapter 7) in the presence of various electrolytes (sodium chloride, NaCl, calcium chloride, CaCl2 and magnesium chloride, MgCl2), organic substances (humic acid, HA) and bovine serum albumin (BSA) were investigated at a controlled pH of 7 in simulated water. It was revealed that aging factors followed by electrostatic, hydrophobic, and van der Waals interactions, including cation bridging, ligand exchange, and hydrogen bonding, could be potential interaction mechanisms responsible for altering the shape, crystallinity, purity, size, and surface charge of ZnO-NPs in the presence of electrolytes, organic substances and proteins in water systems. The results strongly suggested the agglomeration of ZnO-NPs in organic matter, salts and contaminants. Thus the sedimentation and precipitation are promising under salty surface waters/sea waters. Overall, this study (thesis) revealed important outcomes explaining the sources, occurrence and reported concentrations of various ENPs and BFRs in environmental systems, their fate and behaviour and the formation of complex compounds after their interactions. This study also revealed the environmental effects of nanoparticles (found in packed product-sunscreens) in many water systems. This thesis explains the possible morphological, structural, and elemental analyses of ZnO-NPs extracted from sunscreens, wastewaters and commercially available ZnO-NPs. This thesis also thoroughly explained the interaction mechanisms responsible for the alterations, fate and behaviour of ZnO-NPs before and after their interactions with BFRs and PFAS impacted by salts and other organic and inorganic substances. This work provides insights on the fate and behaviour of altered nanoparticles which are relevant to the exposure and risk assessment for aquatic and marine life.
- Subject
- engineered nanoparticles; emerging contaminants; ZnO-NPs; adsorption; agglomeration; zeta potential; aqueous system
- Identifier
- http://hdl.handle.net/1959.13/1511436
- Identifier
- uon:56496
- Rights
- This thesis is currently under embargo and will be available from 20.08.2025. Copyright 2024 Anwar Ul Haq Khan
- Language
- eng
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