Synthesis of wastewater sludge-derived TiO₂ and its composites for NOₓ removal

Hossain, Sayed Mukit

Synthesis of wastewater sludge-derived TiO₂ and its composites for NOₓ removal

Hossain, Sayed Mukit

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Publication Type:: Thesis
Issue Date:: 2022

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Field	Value	Language
dc.contributor.author	Hossain, Sayed Mukit
dc.date.accessioned	2022-11-28T00:00:31Z
dc.date.available	2022-11-28T00:00:31Z
dc.date.issued	2022
dc.identifier.uri	http://hdl.handle.net/10453/163763
dc.description	University of Technology Sydney. Faculty of Engineering and Information Technology.	en_US.UTF-8
dc.description.abstract	This research focuses on wastewater flocculation, sludge recycling, and degrading air pollutants using recovered sludge by-products. Resource recovery from coagulation and flocculation is a holistic environmental and economic sustainability approach. Reusing treated wastewater, by-products, and residues created after treatment helps wastewater treatment protect the environment and essential resources. By calcining Ti⁴⁺ flocculated wastewater sludge, TiO₂ could be synthesized. However, Ti-salt-based coagulation produces acidic effluent, and the photoactivity of sludge-generated TiO₂ (S-TiO₂) is confined to UV spectra only. So, this study's broad goals are to (a) investigate the possibility of generating metal-doped and undoped photocatalyst grade titania while solving Ti-salt-based flocculation's low pH challenge, along with (b) visible light activation of S-TiO₂ for photodegradation of NOₓ. Initially, TiCl₄ and Ca(OH)₂ were employed to flocculate synthetic wastewater, and an optimum coagulant dose was determined by measuring the treated water's turbidity, DOC, and zeta potential. As a coagulant aid, Ca(OH)₂ attained a neutral pH, at 32.40 mg Ca/L and 14.54 mg Ti/L coagulant dose. Both Ca-doped and S-TiO₂ were produced from flocculated sludge for morphological and photocatalytic assessment. The doped Ca atoms prevented the production of anatase TiO₂, and no CaO was observed. At the optimum Ca(OH)₂ dose, Ca-doped TiO₂ was inferior to S-TiO₂ in acetaldehyde photodegradation. Subsequently, for the viability of A-TiO₂ production from algae blooming surface water, TiCl₄ was found to be better than commercially available polyaluminum chloride. In a microcosm jar test, 0.3 g Ti/L removed 99.8% of turbidity, 67% COD, and 96% TP. Under a 10 W/m² UV-A lamp, A-TiO₂ nanoparticles and coated mortar blocks successfully eliminated gaseous CH₃CHO and NOₓ. In addition, this study investigates the feasibility of producing TiO₂/g-CN heterojunction using Ti-incorporated dried dye wastewater sludge to enhance S-TiO₂’s photoactivity. Primarily, only the dried sludge and melamine mixture were calcined, and the one-step calcination technique did not produce heterojunction, only N-doped anatase TiO₂. However, a successful TiO₂/g-CN composite was formed by calcining S-TiO₂ and melamine, and the optimum mixing ratio was evaluated as 1:3. Lastly, titanium nanotubes (S-TNT) were produced from S-TiO₂ and coupled with g-CN. The composite tripled the effective surface area (153.61 m²/g) and reduced the energy bandgap to 3.0 eV. The as-prepared composite's extended light absorption facilitated 19.62% and 32.44% of NO removal under 1 h of visible and UV light, respectively. In conclusion, it is feasible to make water and air safer and cleaner when considering Ti coagulants' exceptional coagulation performance.	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/10453/163763/2/02whole.pdf
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.rights	info:eu-repo/semantics/openAccess
dc.title	Synthesis of wastewater sludge-derived TiO₂ and its composites for NOₓ removal	en_US.UTF-8
dc.type	Thesis
utslib.copyright.status	open_access	*

Abstract:

This research focuses on wastewater flocculation, sludge recycling, and degrading air pollutants using recovered sludge by-products. Resource recovery from coagulation and flocculation is a holistic environmental and economic sustainability approach. Reusing treated wastewater, by-products, and residues created after treatment helps wastewater treatment protect the environment and essential resources. By calcining Ti⁴⁺ flocculated wastewater sludge, TiO₂ could be synthesized. However, Ti-salt-based coagulation produces acidic effluent, and the photoactivity of sludge-generated TiO₂ (S-TiO₂) is confined to UV spectra only. So, this study's broad goals are to (a) investigate the possibility of generating metal-doped and undoped photocatalyst grade titania while solving Ti-salt-based flocculation's low pH challenge, along with (b) visible light activation of S-TiO₂ for photodegradation of NOₓ. Initially, TiCl₄ and Ca(OH)₂ were employed to flocculate synthetic wastewater, and an optimum coagulant dose was determined by measuring the treated water's turbidity, DOC, and zeta potential. As a coagulant aid, Ca(OH)₂ attained a neutral pH, at 32.40 mg Ca/L and 14.54 mg Ti/L coagulant dose. Both Ca-doped and S-TiO₂ were produced from flocculated sludge for morphological and photocatalytic assessment. The doped Ca atoms prevented the production of anatase TiO₂, and no CaO was observed. At the optimum Ca(OH)₂ dose, Ca-doped TiO₂ was inferior to S-TiO₂ in acetaldehyde photodegradation. Subsequently, for the viability of A-TiO₂ production from algae blooming surface water, TiCl₄ was found to be better than commercially available polyaluminum chloride. In a microcosm jar test, 0.3 g Ti/L removed 99.8% of turbidity, 67% COD, and 96% TP. Under a 10 W/m² UV-A lamp, A-TiO₂ nanoparticles and coated mortar blocks successfully eliminated gaseous CH₃CHO and NOₓ. In addition, this study investigates the feasibility of producing TiO₂/g-CN heterojunction using Ti-incorporated dried dye wastewater sludge to enhance S-TiO₂’s photoactivity. Primarily, only the dried sludge and melamine mixture were calcined, and the one-step calcination technique did not produce heterojunction, only N-doped anatase TiO₂. However, a successful TiO₂/g-CN composite was formed by calcining S-TiO₂ and melamine, and the optimum mixing ratio was evaluated as 1:3. Lastly, titanium nanotubes (S-TNT) were produced from S-TiO₂ and coupled with g-CN. The composite tripled the effective surface area (153.61 m²/g) and reduced the energy bandgap to 3.0 eV. The as-prepared composite's extended light absorption facilitated 19.62% and 32.44% of NO removal under 1 h of visible and UV light, respectively. In conclusion, it is feasible to make water and air safer and cleaner when considering Ti coagulants' exceptional coagulation performance.

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