Enhanced PVDF membrane antifouling performance via surface modification by functional polymers

In the past several decades, membrane technology is widely used in separation process in various fields. In particular, membrane bioreactors (MBRs) as an application of membrane technology has attracted increasing attention from the researchers worldwide. However, there still exists many obstacles i...

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Main Author: Zhao, Guili
Other Authors: Chen Wei Ning, William
Format: Theses and Dissertations
Language:English
Published: 2017
Subjects:
Online Access:http://hdl.handle.net/10356/69492
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Institution: Nanyang Technological University
Language: English
id sg-ntu-dr.10356-69492
record_format dspace
institution Nanyang Technological University
building NTU Library
continent Asia
country Singapore
Singapore
content_provider NTU Library
collection DR-NTU
language English
topic DRNTU::Engineering::Chemical engineering::Polymers and polymer manufacture
DRNTU::Engineering::Environmental engineering::Water treatment
DRNTU::Engineering::Materials::Functional materials
DRNTU::Engineering::Materials::Material testing and characterization
spellingShingle DRNTU::Engineering::Chemical engineering::Polymers and polymer manufacture
DRNTU::Engineering::Environmental engineering::Water treatment
DRNTU::Engineering::Materials::Functional materials
DRNTU::Engineering::Materials::Material testing and characterization
Zhao, Guili
Enhanced PVDF membrane antifouling performance via surface modification by functional polymers
description In the past several decades, membrane technology is widely used in separation process in various fields. In particular, membrane bioreactors (MBRs) as an application of membrane technology has attracted increasing attention from the researchers worldwide. However, there still exists many obstacles in membrane widespread application and the major challenge is membrane fouling. Recently, antifouling membrane fabrication by functional polymers is regarded as a promising and effective strategy to inhibit membrane fouling. Thus, this research work mainly focuses on poly(vinylidene fluoride) (PVDF) membrane modification by thermosensitive polymer PNIPAAm [poly(N-isopropylacrylamide)] and its copolymer with other functional polymers. Meanwhile, the objective of this thesis is to investigate the application potential of antifouling membrane prepared and to provide a feasible and effective strategy to achieve better antifouling performance for wide application, thereby providing a meaningful reference for future study. Firstly, functional polymer PNIPAAm was successfully bonded onto PVDF membrane via surface-initiated atom transfer radical polymerization (ATRP). The hydrophilicity of PVDF membrane was dramatically enhanced due to the incorporation of PNIPAAm chains. The microfiltration experiments indicated that PNIPAAm modified membrane exhibited a flux recovery ratio (FRR) as high as 91.59%. In addition, bacteria adhesion test revealed that the attachment of Escherichia coli on the modified membrane was reduced by 75% compared to the original membrane. Hence, the fouling tests demonstrated that PNIPAAm modified membrane exhibited obvious thermosensitive property and good antifouling ability compared with pure PVDF membrane. In order to further improve not only fouling resistance but also fouling release property of membrane, three types of modified membrane were well designed by grafting PNIPAAm, PHEMA [poly(hydroxyethyl methacrylate)] and P(HEMA-co-NIPAAm) respectively. Minimum protein adsorption and bacterial adhesion were both obtained on PVDF-g-P(HEMA-co-NIPAAm) membrane, with reduction by 44% and 71% respectively compared to the pristine membrane. The filtration testing indicated that the copolymer modified membrane exhibited high resistance to protein fouling and the foulant on the surface was removed easily by washing, suggesting easy-cleaning capacity. The biofouling on the membrane surface was analyzed using Gram-negative E. coli and Gram-positive Staphylococcus epidermidis. According to biofilm study using E. coli and S. epidermidis, it is inferred that microorganism species played an essential role in the formation and structure of biofilm as the species influenced the bacterial adhesion each other owing to their characteristics. Besides, the modified membrane exhibited higher fouling resistance during filtration and higher flux recovery after hydraulic cleaning compared with the original membrane for long-term use. Furthermore, for thermosensitive PVDF-g-P(HEMA-co-NIPAAm) membrane prepared in this thesis, water cleaning with temperature control provide an auxiliary and feasible strategy to promote the fouling release and to enhance the efficiency of fouling removal except for classical cleaning methods for wastewater treatment. This thesis was one of the limited studies to achieve higher antifouling property focusing on not only fouling resistance but also fouling release for PVDF membrane via grafting functional polymers P(HEMA-co-NIPAAm). This research study provided a feasible and effective strategy of antifouling membrane preparation which can be also used for other types of the membrane in wide range of applications.
author2 Chen Wei Ning, William
author_facet Chen Wei Ning, William
Zhao, Guili
format Theses and Dissertations
author Zhao, Guili
author_sort Zhao, Guili
title Enhanced PVDF membrane antifouling performance via surface modification by functional polymers
title_short Enhanced PVDF membrane antifouling performance via surface modification by functional polymers
title_full Enhanced PVDF membrane antifouling performance via surface modification by functional polymers
title_fullStr Enhanced PVDF membrane antifouling performance via surface modification by functional polymers
title_full_unstemmed Enhanced PVDF membrane antifouling performance via surface modification by functional polymers
title_sort enhanced pvdf membrane antifouling performance via surface modification by functional polymers
publishDate 2017
url http://hdl.handle.net/10356/69492
_version_ 1683493045548351488
spelling sg-ntu-dr.10356-694922020-11-01T04:47:10Z Enhanced PVDF membrane antifouling performance via surface modification by functional polymers Zhao, Guili Chen Wei Ning, William Interdisciplinary Graduate School Nanyang Environment and Water Research Institute DRNTU::Engineering::Chemical engineering::Polymers and polymer manufacture DRNTU::Engineering::Environmental engineering::Water treatment DRNTU::Engineering::Materials::Functional materials DRNTU::Engineering::Materials::Material testing and characterization In the past several decades, membrane technology is widely used in separation process in various fields. In particular, membrane bioreactors (MBRs) as an application of membrane technology has attracted increasing attention from the researchers worldwide. However, there still exists many obstacles in membrane widespread application and the major challenge is membrane fouling. Recently, antifouling membrane fabrication by functional polymers is regarded as a promising and effective strategy to inhibit membrane fouling. Thus, this research work mainly focuses on poly(vinylidene fluoride) (PVDF) membrane modification by thermosensitive polymer PNIPAAm [poly(N-isopropylacrylamide)] and its copolymer with other functional polymers. Meanwhile, the objective of this thesis is to investigate the application potential of antifouling membrane prepared and to provide a feasible and effective strategy to achieve better antifouling performance for wide application, thereby providing a meaningful reference for future study. Firstly, functional polymer PNIPAAm was successfully bonded onto PVDF membrane via surface-initiated atom transfer radical polymerization (ATRP). The hydrophilicity of PVDF membrane was dramatically enhanced due to the incorporation of PNIPAAm chains. The microfiltration experiments indicated that PNIPAAm modified membrane exhibited a flux recovery ratio (FRR) as high as 91.59%. In addition, bacteria adhesion test revealed that the attachment of Escherichia coli on the modified membrane was reduced by 75% compared to the original membrane. Hence, the fouling tests demonstrated that PNIPAAm modified membrane exhibited obvious thermosensitive property and good antifouling ability compared with pure PVDF membrane. In order to further improve not only fouling resistance but also fouling release property of membrane, three types of modified membrane were well designed by grafting PNIPAAm, PHEMA [poly(hydroxyethyl methacrylate)] and P(HEMA-co-NIPAAm) respectively. Minimum protein adsorption and bacterial adhesion were both obtained on PVDF-g-P(HEMA-co-NIPAAm) membrane, with reduction by 44% and 71% respectively compared to the pristine membrane. The filtration testing indicated that the copolymer modified membrane exhibited high resistance to protein fouling and the foulant on the surface was removed easily by washing, suggesting easy-cleaning capacity. The biofouling on the membrane surface was analyzed using Gram-negative E. coli and Gram-positive Staphylococcus epidermidis. According to biofilm study using E. coli and S. epidermidis, it is inferred that microorganism species played an essential role in the formation and structure of biofilm as the species influenced the bacterial adhesion each other owing to their characteristics. Besides, the modified membrane exhibited higher fouling resistance during filtration and higher flux recovery after hydraulic cleaning compared with the original membrane for long-term use. Furthermore, for thermosensitive PVDF-g-P(HEMA-co-NIPAAm) membrane prepared in this thesis, water cleaning with temperature control provide an auxiliary and feasible strategy to promote the fouling release and to enhance the efficiency of fouling removal except for classical cleaning methods for wastewater treatment. This thesis was one of the limited studies to achieve higher antifouling property focusing on not only fouling resistance but also fouling release for PVDF membrane via grafting functional polymers P(HEMA-co-NIPAAm). This research study provided a feasible and effective strategy of antifouling membrane preparation which can be also used for other types of the membrane in wide range of applications. Doctor of Philosophy (IGS) 2017-01-31T07:40:50Z 2017-01-31T07:40:50Z 2017 Thesis Zhao, G. (2017). Enhanced PVDF membrane antifouling performance via surface modification by functional polymers. Doctoral thesis, Nanyang Technological University, Singapore. http://hdl.handle.net/10356/69492 10.32657/10356/69492 en 178 p. application/pdf