Engineering polymeric hydrogels for solar water purification

Mao, Shudi

Engineering polymeric hydrogels for solar water purification

Mao, Shudi

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Publication Type:: Thesis
Issue Date:: 2025

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Field	Value	Language
dc.contributor.author	Mao, Shudi
dc.date.accessioned	2025-11-11T00:48:58Z
dc.date.available	2025-11-11T00:48:58Z
dc.date.issued	2025
dc.identifier.uri	http://hdl.handle.net/10453/190652
dc.description	University of Technology Sydney. Faculty of Engineering and Information Technology.	en_US.UTF-8
dc.description.abstract	Water scarcity, as an increasingly pressing global issue, has posed a serious threat to human health and world peace. Without requiring any extra energy input, Interfacial Solar Steam Generation (ISSG) offers a promising complement to current energy-intensive freshwater production technologies. Both thermal and water managements play crucial roles in governing the performance of ISSG systems. However, thermal management alone such as enhancing light capture and solar-thermal conversion cannot surpass the theoretical evaporation rate limit of 1.59 kg m-2 h-1 under one-sun irradiation (1 kW m-2). By utilizing polymeric hydrogels, equivalent evaporation enthalpy of water (EEW) can be lowered through hydrogen bonding, activating surrounding water molecules and facilitating evaporation. Despite this potential, insufficient understanding of the structure-property relationships between hydrogels and water molecules limits the advancement of efficient hydrogel-based ISSG systems. This thesis investigates the interactions of polymeric hydrogels with water molecules across nano-, micron-, and macro-scales. At nanoscale, seven different hydrogels with diverse functional groups were synthesized, and their relationships with key properties (e.g., evaporation enthalpy, electrostatic potential) and the corresponding hydrogels’ ISSG performance were systematically investigated. Hydrophilic groups were ranked based on their influence on ISSG potential as follows: -N+(CH3)3Cl- < -SO3H < -COOH < -OH < -C-O-C- < -N(CH3)2 < -NH2. Among the tested hydrogels, polyacrylamide (PAM) ISSG containing -NH2 groups demonstrated superior performance, characterized by rapid water replenishment capability, a high intermediate water (IW) content of 78.2%, low EEW, and an exceptional seawater evaporation rate of 3.41 kg m-1 h-1. At microscale, interconnected pores were constructed by selecting polymer precursors with appropriate glass transition temperatures (Tg), and employing freeze-thaw processing. This approach facilitated water transport, enabling continuous evaporation and achieving an enhanced evaporation rate of 3.59 kg m-1 h-1. Finally, at macroscale, Digital Light Processing (DLP) 3D printing was employed to scale up hydrogel fabrication with optimized monomer consumption by adding poly(vinyl alcohol) (PVA) for improved printability and ensuring consistent layer-by-layer printing. This methodology enabled the successful fabrication of hydrogels with intricate macro/microstructures, allowing tailored control over water and heat transport properties while utilizing record-low polymer dosages. The resulting hydrogels exhibited high porosity, enhanced water uptake, low EEW, and a high evaporation rate of 3.56 kg m-2 h-1. My PhD research has achieved remarkable advancements in freshwater production from seawater and wastewater, representing several significant breakthroughs in ISSG for sustainable water treatment applications.	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/10453/190652/1/thesis.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	© 2025 Shudi Mao
dc.rights	au.edu.uts.lib/cph
dc.title	Engineering polymeric hydrogels for solar water purification	en_US.UTF-8
dc.type	Thesis
utslib.copyright.status	open_access	*

Abstract:

Water scarcity, as an increasingly pressing global issue, has posed a serious threat to human health and world peace. Without requiring any extra energy input, Interfacial Solar Steam Generation (ISSG) offers a promising complement to current energy-intensive freshwater production technologies. Both thermal and water managements play crucial roles in governing the performance of ISSG systems. However, thermal management alone such as enhancing light capture and solar-thermal conversion cannot surpass the theoretical evaporation rate limit of 1.59 kg m-2 h-1 under one-sun irradiation (1 kW m-2). By utilizing polymeric hydrogels, equivalent evaporation enthalpy of water (EEW) can be lowered through hydrogen bonding, activating surrounding water molecules and facilitating evaporation. Despite this potential, insufficient understanding of the structure-property relationships between hydrogels and water molecules limits the advancement of efficient hydrogel-based ISSG systems. This thesis investigates the interactions of polymeric hydrogels with water molecules across nano-, micron-, and macro-scales. At nanoscale, seven different hydrogels with diverse functional groups were synthesized, and their relationships with key properties (e.g., evaporation enthalpy, electrostatic potential) and the corresponding hydrogels’ ISSG performance were systematically investigated. Hydrophilic groups were ranked based on their influence on ISSG potential as follows: -N+(CH3)3Cl- < -SO3H < -COOH < -OH < -C-O-C- < -N(CH3)2 < -NH2. Among the tested hydrogels, polyacrylamide (PAM) ISSG containing -NH2 groups demonstrated superior performance, characterized by rapid water replenishment capability, a high intermediate water (IW) content of 78.2%, low EEW, and an exceptional seawater evaporation rate of 3.41 kg m-1 h-1. At microscale, interconnected pores were constructed by selecting polymer precursors with appropriate glass transition temperatures (Tg), and employing freeze-thaw processing. This approach facilitated water transport, enabling continuous evaporation and achieving an enhanced evaporation rate of 3.59 kg m-1 h-1. Finally, at macroscale, Digital Light Processing (DLP) 3D printing was employed to scale up hydrogel fabrication with optimized monomer consumption by adding poly(vinyl alcohol) (PVA) for improved printability and ensuring consistent layer-by-layer printing. This methodology enabled the successful fabrication of hydrogels with intricate macro/microstructures, allowing tailored control over water and heat transport properties while utilizing record-low polymer dosages. The resulting hydrogels exhibited high porosity, enhanced water uptake, low EEW, and a high evaporation rate of 3.56 kg m-2 h-1. My PhD research has achieved remarkable advancements in freshwater production from seawater and wastewater, representing several significant breakthroughs in ISSG for sustainable water treatment applications.

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