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Conductive Ultrafiltration Membrane Fabrication via a Novel Vacuum- Assisted Layer-by-Layer Assembly of Functionalized Carbon Nanotubes

Title:

Conductive Ultrafiltration Membrane Fabrication via a Novel Vacuum- Assisted Layer-by-Layer Assembly of Functionalized Carbon Nanotubes

Omi, Farah Rahman (2015) Conductive Ultrafiltration Membrane Fabrication via a Novel Vacuum- Assisted Layer-by-Layer Assembly of Functionalized Carbon Nanotubes. Masters thesis, Concordia University.

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Abstract

Membrane processes are currently used in several ways to purify water and wastewater. Because
of their high performance and smaller footprint, membranes are likely to grow in importance as
compared to other conventional technologies. Therefore, there is a critical need for development
of improved membranes that have higher flux, greater selectivity, and are less prone to fouling.
Recently, multiwalled carbon nanotube (MWNT) electrochemical (EC) filter was reported to be
extremely effective as a point-of-use technology in achieving complete removal and inactivation
of pathogens. In order to scale-up the electrochemical filtration technology to utilize it in a plantscale
centralized water treatment plant, conductive nano-composite ultrafiltration membranes
were developed in this project, through incorporating amine and carboxylic functionalized
MWNTs (MWNT-NH2, MWNT-COOH) into polysulfone (PSf) substrates. A novel fabrication
method, vacuum-assisted layer-by-layer self-assembly was used for surface modification of
polysulfone ultrafiltration membrane.
First, the polysulfone membrane was functionalized with oxygen containing negatively charged
functional groups through oxygen plasma treatment. In order to optimize the degree of
functionalization of polysulfone membrane with increasing plasma duration, a comprehensive
physicochemical characterization of the plasma treated membrane was performed by using ATRFTIR,
XPS, contact angle, EKA and SEM analyses. Water permeability test was also conducted
to investigate the differential performance of the plasma-treated membrane with increase in
plasma treatment duration. The ATR-FTIR analyses revealed the peaks at specific wavelengths
for hydroxyl, carboxyl and carbonyl functional groups, while the XPS results showed an increase
in oxygen content of the pristine polysulfone from 18.6% to 30.7%, after being plasma treated.The contact angle of the plasma-treated membrane dropped down to 44.2° from 68.6° of the
pristine membrane and the EKA showed an increase in surface zeta potential from -22.5mV to -
42.8mV for varying plasma duration. Based on these analyses, 60s plasma treatment time was set
as optimum for further modification of PSf membrane with MWNT.
The MWNT modified PSf membrane was characterized with a SEM that showed the uniform
distribution of MWNTs throughout the membrane thickness as well as a linear growth in
membrane thickness with increasing number of MWNT bilayers. The water contact angle
analyses revealed that the modified membrane became more hydrophobic with increasing
number of bilayers. The modified membrane exhibited reasonable permeability, higher
conductivity and high antifouling properties due to application of very low DC potential (0V-
3V). Due to high conductivity of the MWNT modified membrane an application of 3V DC
voltage showed almost 100% inactivation of E. coli inactivation suggesting the effectiveness of
the MWNT modified polysulfone membrane in controlling the biofouling in electrofiltration
system. Moreover, this study showed over 99% degradation of methyl orange during
electrofiltration that could contribute to reducing the organic fouling of the modified membrane.
Overall, the new MWNT modified polysulfone membrane has huge potential to be used in large
scale electrofiltration systems.

Divisions:Concordia University > Gina Cody School of Engineering and Computer Science > Building, Civil and Environmental Engineering
Item Type:Thesis (Masters)
Authors:Omi, Farah Rahman
Institution:Concordia University
Degree Name:M.A. Sc.
Program:Civil Engineering
Date:5 February 2015
Thesis Supervisor(s):Rahaman, Saifur
ID Code:979724
Deposited By: FARAH RAHMAN
Deposited On:20 Jun 2017 19:20
Last Modified:18 Jan 2018 17:49
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