Immobilization of nanoscale zero-valent iron (NZVI) onto electrospun nanofiber membrane for groundwater remediation

Ren, Jiawei

Immobilization of nanoscale zero-valent iron (NZVI) onto electrospun nanofiber membrane for groundwater remediation

Ren, Jiawei

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Publication Type:: Thesis
Issue Date:: 2019

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Field	Value	Language
dc.contributor.author	Ren, Jiawei
dc.date.accessioned	2020-05-25T05:44:54Z
dc.date.available	2020-05-25T05:44:54Z
dc.date.issued	2019
dc.identifier.uri	http://hdl.handle.net/10453/140924
dc.description	University of Technology Sydney. Faculty of Engineering and Information Technology.	en_AU
dc.description.abstract	Nanoscale zero-valent iron (nZVI), as a promising material, has been widely used in groundwater remediation. However, individual nZVI particles are prone to agglomeration and hence sediment in the water environment, which reduces the reactivity of nZVI as well as its performance in contaminant removal. Membrane-supported nZVI can both avoid nZVI agglomeration for better reactivity and recycle nZVI/contaminants to lower the risk of secondary pollution. In this study, a new approach that combines nZVI with electrospinning technology has been put forward to obtain the membrane-supported nZVI. First, we developed a polyacrylic acid - polyvinyl alcohol (PAA-PVA) electrospun nanofiber membrane. The results indicate that nZVI particles were successfully immobilized on the membrane and had excellent removals to methylene blue and Cu (II) ions at 94% and 83.6% respectively. Subsequently, a “robbing behaviour” was observed during the nZVI immobilization. The robbing behaviour can significantly reduce the number of nZVI particles immobilized onto the membrane and hence weaken the performance of mitigating contaminated water. To minimize the undesirable effect of robbing behaviour, we developed a dipping method that enables exposure of enough free Fe (II) as electron acceptors to the Fe (II)-complexed PAA-PVA membrane for the subsequent reduction. The results shows that the membrane with dipping can immobilize more than 1.7 times the weight percentage of nZVI particles for the membrane without dipping. However, we found that the developed PVA-PAA-nZVI composites had a low mechanical strength after undergoing multiple reduction by NaBH₄ and membrane mechanical strength is a critical property for a long-term operation and the regeneration of nZVI membranes. Therefore, a high molecular weight dual-crosslinking method was investigated to improve the mechanical strength of polymeric electrospun nanofiber membranes. Alternatively, we examined to fabricate a polyvinylidene fluoride - graphene oxide (PVDF-GO) nanofiber membrane composite for nZVI immobilization. The addition of GO into PVDF nanofibers can both increase the hydrophilicity to improve membrane flux and offer –COOH as a binder to immobilize nZVI particles. PVDF-GO-nZVI membranes with different GO loadings (0%, 0.5%, 1%, 3% of PVDF) were tested with two typical nZVI-targeted contaminants (Cd(II) and trichloroethylene (TCE)) via gravity-driven membrane filtration. The results show that membrane with 1% GO had the best nZVI distribution against the aggregation and a better performance in both Cd removal (100%) and TCE removal (82%). To sum up, the eletrospun nanofiber membrane is a very suitable material for nZVI immobilization and the developed nZVI-immobilized electrospun nanofiber membrane composites had a great potential in groundwater remediation.	en_AU
dc.format	Thesis (PhD)
dc.language.iso	en_US	en_US
dc.relation	https://opus.lib.uts.edu.au/bitstream/10453/140924/2/02Whole.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	info:eu-repo/semantics/openAccess
dc.rights	au.edu.uts.lib/ppc
dc.title	Immobilization of nanoscale zero-valent iron (NZVI) onto electrospun nanofiber membrane for groundwater remediation	en_AU
dc.type	Thesis
utslib.copyright.status	open_access	*

Abstract:

Nanoscale zero-valent iron (nZVI), as a promising material, has been widely used in groundwater remediation. However, individual nZVI particles are prone to agglomeration and hence sediment in the water environment, which reduces the reactivity of nZVI as well as its performance in contaminant removal. Membrane-supported nZVI can both avoid nZVI agglomeration for better reactivity and recycle nZVI/contaminants to lower the risk of secondary pollution. In this study, a new approach that combines nZVI with electrospinning technology has been put forward to obtain the membrane-supported nZVI. First, we developed a polyacrylic acid - polyvinyl alcohol (PAA-PVA) electrospun nanofiber membrane. The results indicate that nZVI particles were successfully immobilized on the membrane and had excellent removals to methylene blue and Cu (II) ions at 94% and 83.6% respectively. Subsequently, a “robbing behaviour” was observed during the nZVI immobilization. The robbing behaviour can significantly reduce the number of nZVI particles immobilized onto the membrane and hence weaken the performance of mitigating contaminated water. To minimize the undesirable effect of robbing behaviour, we developed a dipping method that enables exposure of enough free Fe (II) as electron acceptors to the Fe (II)-complexed PAA-PVA membrane for the subsequent reduction. The results shows that the membrane with dipping can immobilize more than 1.7 times the weight percentage of nZVI particles for the membrane without dipping. However, we found that the developed PVA-PAA-nZVI composites had a low mechanical strength after undergoing multiple reduction by NaBH₄ and membrane mechanical strength is a critical property for a long-term operation and the regeneration of nZVI membranes. Therefore, a high molecular weight dual-crosslinking method was investigated to improve the mechanical strength of polymeric electrospun nanofiber membranes. Alternatively, we examined to fabricate a polyvinylidene fluoride - graphene oxide (PVDF-GO) nanofiber membrane composite for nZVI immobilization. The addition of GO into PVDF nanofibers can both increase the hydrophilicity to improve membrane flux and offer –COOH as a binder to immobilize nZVI particles. PVDF-GO-nZVI membranes with different GO loadings (0%, 0.5%, 1%, 3% of PVDF) were tested with two typical nZVI-targeted contaminants (Cd(II) and trichloroethylene (TCE)) via gravity-driven membrane filtration. The results show that membrane with 1% GO had the best nZVI distribution against the aggregation and a better performance in both Cd removal (100%) and TCE removal (82%). To sum up, the eletrospun nanofiber membrane is a very suitable material for nZVI immobilization and the developed nZVI-immobilized electrospun nanofiber membrane composites had a great potential in groundwater remediation.

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http://hdl.handle.net/10453/140924