EFFECT OF SURFACE MODIFICATION WITH ELECTROSPUN NANOFIBERS · PDF file...

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  • 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

  • ii

    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.

  • iii

    I dedicate this study to:

    My father`s soul,

    My mom,

    Pedram and

    Tanaz

  • iv

    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.

  • v

    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

  • vi

    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

  • vii

    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.........................................................................................