EFFECT OF SURFACE MODIFICATION WITH ELECTROSPUN

NANOFIBERS ON THE PERFORMANCE OF THE

ULTRAFILTRATION MEMBRANE

By:

Ladan Zoka

Master of Applied Science Thesis

Submitted to the School of Graduate Studies and Research under the supervision of

Dr. Takeshi Matsuura and Dr. Roberto M. Narbaitz

In partial fulfilment of the requirement for the degree of Master of Applied Science in

Environmental Engineering

The degree is offered under Ottawa- Carleton Institute for Environmental Engineering

Department of Civil Engineering at University of Ottawa

Ottawa, Ontario

Canada K1N 6N5

 Ladan Zoka, Ottawa, Canada, 2018

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ABSTRACT

Membrane surface modification is often utilized to combat membrane fouling, i.e., the

deterioration of membrane performance with time. Among many modification methods,

the effect of coating the surface of a commercial membrane with electrospun nanofibers

on the membrane performance has received little attention.

In this work, a commercial polyethersulfone (PES) ultrafiltration membrane was

modified by electrospinning PVDF hydrophobic nanofibers for different time periods, i.e.,

25min, 125min, and 250min, and its effect on the filtration performance was investigated.

It was found that coating with the electrospun nanofiber layer enhanced the pure water

permeation (PWP) flux. While the fouling of electrospun PES (EPES) membranes was

more severe when they filtered Ottawa River (OR) Water or protein solutions, their final

flux was still higher than that of the PES membrane. The membranes were further

characterized by scanning electron microscopy (SEM), contact angle measurement and

pore size and pore size distribution. The relationship between these characteristics and

the membrane performance was discussed.

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I dedicate this study to:

My father`s soul,

My mom,

Pedram and

Tanaz

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ACKNOWLEDGEMENTS

I would like to express my gratitude to my supervisors Dr. Takeshi Matsuura and Dr.

Roberto Narbaitz for their continuous support, guidance, patience, enthusiasm, and

immense knowledge during all the testing and writing my thesis. This work would not

have been possible without them.

I would also like to thank Dr. Dipak Rana from the Department of Chemical and

Biochemical Engineering for his support and advice. I would like to thank Louis

Tremblay, the chemical engineering technician, for his help and recommendations. Also,

I would like my friend and lab co- worker Johnson Efome for teaching me how to use the

electrospinning equipment.

I would like to thank my dear friends Bingjie Xu and Pablo Gonzalez Galvis for their

help, support, and encouragement. We were Dr. Narbaitz’s students and Bingjie was the

first friend that I met since the beginning of the master’s program. Also, I would like to

thank Patrick D’Aoust, environmental engineering lab technician, and Neda Arabgol as

my friends, classmates, office mates, and for their help and advice. My other friends in

the same office: Nour Al- ghuasian, Kellie Boyle, and Maha Dabas always supported me.

Thanks for all those precious times of laughing, chating, and crying we spent together.

And at the end I would like to thank my angels, my parents. I need to give an additional

thanks to my dear husband Pedram Fouladirad and my pretty and lovely daughter Tanaz

Fouladirad for their support, love, understanding, inspiration, and encouragement. Thanks

to my dear sister Rana for her support and advice in this journey. Thanks to my brother,

Mohammad, for his support from far away.

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TABLE OF CONTENTS

ABSTRACT ........................................................................................................................ ii

ACKNOWLEDGEMENTS ............................................................................................... iv

ABBREVIATIONS ......................................................................................................... xiii

GLOSSARY .................................................................................................................... xvi

CHAPTER 1 ....................................................................................................................... 1

INTRODUCTION .............................................................................................................. 1

CHAPTER 2 ....................................................................................................................... 3

LITERATURE REVIEW .................................................................................................. 3

2.1 Membranes ................................................................................................................ 3

2.1.1 Membrane types and formation method ............................................................ 7

2.1.2 Symmetric membranes ....................................................................................... 9

2.1.3 Asymmetric membranes .................................................................................. 11

2.1.4 Thin-film composite membranes ...................................................................... 14

2.2 Membrane processes .............................................................................................. 16

2.2.1 Ultrafiltration: ................................................................................................... 16

2.3 Membrane fouling .................................................................................................. 18

2.3.1 Types of fouling................................................................................................ 19

2.3.2 Foulants .......................................................................................................... 22

2.3.2.1 Natural organic matter ............................................................................. 23

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2.3.2.2 Scaling...................................................................................................... 24

2.3.2.3 Membrane biofouling............................................................................... 24

2.4 Factors affecting membrane fouling ...................................................................... 25

2.4.1 Impact of feed properties ................................................................................. 25

2.4.1.1 Concentration ............................................................................................ 25

2.4.1.2 pH and ionic strength ............................................................................... 25

2.4.1.3 Constitution interactions ........................................................................... 26

2.4.1.4 Prefiltration and aggregates removal ........................................................ 26

2.4.2 Effect of membrane physio-chemical characteristics on membrane performance

and fouling ................................................................................................................. 26

2.4.2.1 Pore size ................................................................................................... 26

2.4.2.2 Porosity and pore size distribution ........................................................... 27

2.4.2.3 Physico-chemical properties .................................................................... 27

2.4.3 The effect of the membrane operating factors ................................................. 28

2.4.3.1 Transmembrane pressure ......................................................................... 28

2.4.3.2 Temperature ............................................................................................. 28

2.4.3.3 Cross-flow velocity and turbulence ......................................................... 29

2.5 Membrane cleaning ................................................................................................. 30

2.5.1 Physical cleaning methods............................................................................... 30

2.5.2 Chemical cleaning methods ............................................................................. 30

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2.5.3 Physico-chemical cleaning methods ................................................................ 31

2.5.4 Biological cleaning methods ........................................................................... 31

2.6 Approaches for improving membrane performance ............................................... 31

2.6.1 Boundary layer or velocity control .................................................................. 31

2.6.2 Turbulence generator ...................................................................................... 32

2.6.3 Membrane material and modification .............................................................. 32

2.7 Electrospinning.........................................................................................