- Title
- Remediation of emerging contaminants
- Creator
- Khoshyan, Ashkan
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2025
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- Emerging contaminants are synthetic or natural chemicals and microorganisms that are not routinely monitored but can harm ecosystems and human health. These include pharmaceuticals, pesticides, industrial chemicals, surfactants, and personal care products found in water and food sources. Endocrine disruptors, antibiotics, and various pharmaceutical compounds also fall into this category. The toxicity of many remains unstudied, and they often go untested in municipal water systems. Additionally, they may generate unknown by-products during water treatment, and biological contaminants are another significant concern. Among these emerging contaminants, per- and poly fluoroalkyl substances (PFAS) are anthropogenic chemicals which have been manufactured and utilised since the 1940s. Due to their unique physico-chemical properties, they have been used in a wide range of sectors. Unfortunately, their discharge into the environment has been associated with human health and wildlife risk. PFAS demonstrate simultaneous hydrophilic and hydrophobic properties, which enable them to accumulate at interfacial regions. Accordingly, they are able to transport worldwide and contaminate vadose zone far from the emission point. Although policymakers and environmental authorities have established health advisory guidelines, particularly for drinking water, environmental contamination by PFAS as an emerging contaminant still requires attention through practical remediation technologies. However, each approach comes with its own set of advantages and disadvantages. Therefore, to make remediation technologies more practical, cost-effective, scalable, environmentally friendly, and time-efficient, further research and development are essential. The initial part of this study focuses on the adsorption process using materials typically employed to fabricate anodes for the electrochemical advanced oxidation (EAOPs) of PFAS in water. Magnéli phase titanium sub-oxide (Ti4O7), a new anode in PFAS electrooxidation, was used to elucidate the discrepancy in fluoride mass balance between the PFAS introduced before the electrooxidation process and the fluoride recovered after the reaction. The results showed that although (perfluorooctanoic acid) PFOA adsorption was inconsiderable compared to other reported adsorbents, factors such as solution pH, particle size, and ionic strength impacted the adsorption capacity. The adsorption isotherms and reaction kinetics were analysed using several commonly studied models, with the Langmuir and pseudo-second-order models being the best fit. The second part of this study, which is the main component of this research project, is to investigate and develop ultrasonic-based technologies to destroy different types of PFAS as well as AFFFs as representations of highly environmentally contaminated samples to evaluate the practicality of the ultrasonic technology. Firstly, the geometric features of ultrasonication, which are mostly overlooked, were considered in indirect ultrasonic methods by using two commonly used labware materials: glass and polypropylene (PP). The results showed that glass enhanced the propagation of ultrasonic waves in terms of sound velocity and intensity. After examining key factors such as frequency and power input, approximately 95% of PFOA, with an initial concentration of 1 mg/L (ppm), was defluorinated within 3 hours. In contrast, under the same operating conditions, using PP resulted in only around 46% defluorination. These results were same when other types of PFAS and AFFFs were studied. Secondly, in the context of advanced oxidation processes, which are principally based on the generation of reactive radicals to enhance the PFAS destruction, the piezo-catalytic activity of PTFE induced by ultrasonic waves was investigated. Based on data obtained from geometric studies, the defluorination of PFOA in the presence of PTFE using PP increased from approximately 46% to around 98%, indicating that radicals such as hydroxyl (OH•) contributed synergistically with the ultrasonic pyrolysis effect. Alongside investigating key parameters such as ultrasonic frequency and power input, the effect of PTFE particle size was examined. When applied to other types of PFAS and AFFFs, this method showed a significant improvement in defluorination efficiency compared to using ultrasound alone. Notably, no considerable interaction between PFOA and polytetrafluoroethylene (PTFE) was observed. Thirdly, the synergistic effect of geometric factors (reactor material) and ultrasound irradiation modes (continuous, sweep, and pulse) was utilised to enhance the generation of carbonate radicals. The sweep mode demonstrated that sound waves passing through the glass reactor led to a higher production of OH• radicals. This was confirmed when carbonate radicals were introduced into the system, acting as radical scavengers for OH• and producing carbonate radicals. Under optimised conditions (frequency = 80 kHz and 100% power setting), approximately 69% of PFOA, with an initial concentration of 15 mg/L, was defluorinated within 6 hours. Various contributing factors such as solution pH, volume, carbonate dosage, and inorganic additives were also examined. It is noteworthy that the generation of carbonate radicals was confirmed using radical probes like phenol and aniline. However, the studied method was impractical for perfluorooctane sulfonic acid (PFOS). However, all of these studies are served to understand, how advanced oxidation process (AOP), which is mainly based on oxidation/reduction reactions, will improve the generation of reactive radicals in the shed of ultrasonic irradiation.
- Subject
- remediation; emerging contaminants; PFAS; human health; ecosystems
- Identifier
- http://hdl.handle.net/1959.13/1518345
- Identifier
- uon:57275
- Rights
- Copyright 2025 Ashkan Khoshyan
- Language
- eng
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| View Details Download | ATTACHMENT01 | Thesis | 105 MB | Adobe Acrobat PDF | View Details Download | ||
| View Details Download | ATTACHMENT02 | Abstract | 337 KB | Adobe Acrobat PDF | View Details Download |