Novel high throughput mixed matrix membranes embracing poly ionic liquid-grafted biopolymer: Fabrication, characterization, permeation and antifouling performance

Article abstract of DOI:10.1016/j.molliq.2018.06.100

We report a simple and effective protocol for preparation of a poly-ionic liquid (PIL)-grafted chitosan Schiff base (PILCSB) and titanium oxide nanoparticles (TNPs) for application as an antibiofouling nanocomposite in the fabrication of new polysulfone (PSU) ultrafiltration mixed matrix membranes (MMMs). The effect new additive (PILCSB@TNPs) on the porosity texture, pure water flux (PWF) and antibiofouling profile for modified MMMs was investigated. Interestingly, the surface hydrophilicity of these MMMs was remarkably enhanced in comparison to the neat PSU membrane (M0) as revealed from wettability and water contact- angle results (wettability/water contact angle = 29.18%/93.48° and 83.46%/57.35° for M0 and MMM6, respectively).

Full text of DOI:10.1016/j.molliq.2018.06.100

Accepted Manuscript
Novel high throughput mixed matrix membranes embracing poly
ionic liquid-grafted biopolymer: Fabrication, characterization,
permeation and antifouling performance
Reda F.M. Elshaarawy, Janina Dechnik, Hassan M.A. Hassan,
Dennis Dietrich, Mohamed A. Betiha, Stephan Schmidt,
Christoph Janiak
PII:
DOI:
Reference:
S0167-7322(18)32781-8
doi:10.1016/j.molliq.2018.06.100
MOLLIQ 9298
To appear in:
Journal of Molecular Liquids
Received date:
Revised date:
Accepted date:
28 May 2018
22 June 2018
25 June 2018
Please cite this article as: Reda F.M. Elshaarawy, Janina Dechnik, Hassan M.A. Hassan,
Dennis Dietrich, Mohamed A. Betiha, Stephan Schmidt, Christoph Janiak , Novel high
throughput mixed matrix membranes embracing poly ionic liquid-grafted biopolymer:
Fabrication, characterization, permeation and antifouling performance. Molliq (2018),
doi:10.1016/j.molliq.2018.06.100
This is a PDF file of an unedited manuscript that has been accepted for publication. As
a service to our customers we are providing this early version of the manuscript. The
manuscript will undergo copyediting, typesetting, and review of the resulting proof before
it is published in its final form. Please note that during the production process errors may
be discovered which could affect the content, and all legal disclaimers that apply to the
journal pertain.

ACCEPTED MANUSCRIPT
Novel high throughput mixed matrix membranes embracing poly ionic liquid-grafted
biopolymer: fabrication, characterization, permeation and antifouling performance
Reda F.M. Elshaarawya.b,*, Janina Dechnika, Hassan M. A. Hassanb, Dennis Dietricha, Mohamed A.
Betihac, Stephan Schmidtd, Christoph Janiaka,*
a Anorganische Chemie und Strukturchemie Institut, Heinrich-Heine Universität Düsseldorf, 40204 Düsseldorf,
Germany.
b Faculty of Science, Suez University, Suez, Egypt.
c Egyptian Petroleum Research Institute, Nasr City, Cairo 11727, Egypt
d
Department of Colloidal Adhesion, Organic and Macromolecular Chemistry Institute, Heinrich-Heine
Universität Düsseldorf, 40225 Düsseldorf, Germany.
* Corresponding authors
Email: reda.elshaarawy@suezuniv.edu.eg; reel-001@hhu.de
Email: janiak@hhu.de
Abstract
We report a simple and effective protocol for preparation of a poly-ionic liquid (PIL)-grafted
chitosan Schiff base (PILCSB) and titanium oxide nanoparticles (TNPs) for application as an
antibiofouling nanocomposite in the fabrication of new polysulfone (PSU) ultrafiltration
mixed matrix membranes (MMMs). The effect new additive (PILCSB@TNPs) on the
porosity texture, pure water flux (PWF) and antibiofouling profile for modified MMMs was
investigated. Interestingly, the surface hydrophilicity of these MMMs was remarkably
enhanced in comparison to the neat PSU membrane (M0) as revealed from wettability and
water contact- angle results (wettability/ water contact angle = 29.18%/ 93.48° and 83.46%/
57.35° for M0 and MMM6, respectively).
Keywords: Mixed matrix membranes; PIL-grafted biopolymer; Nanocomposite;
Antibiofouling; Water flux.
1. Introduction
During last few decades, the worldwide population has quadrupled while global water
demands grown seven-fold [1]. Where by the end of 2030, 3.9 billion people will suffer
1

ACCEPTED MANUSCRIPT
strongly from water scarcity as predicted by the World Water Council [2]. Therefore, water
scarcity along with poor water quality is a dormant crisis about to explode worldwide. One of
the most promising efforts to stem the global water crisis is the domestic and industrial
wastewater reclamation. Membrane technologies are favored over many other technologies
for purification of water due to their unmatched features such as mild operating conditions,
no chemical additives or thermal inputs requirements, efficient, selective, reliable separations
and eco-friendliness [3].
Outstanding physicochemical features of polysulfone (PSU) including excellent thermal,
chemical, oxidative and hydrolytic stability with preserving its constancy toward pH-
fluctuation [4,5], superior mechanical properties such as toughness, strength, rigidity and
flexibility along with good film forming characteristic [4,6] put it in the forefront of attention
of many researchers for manufacturing of diverse membranes [4,7]. However, the wide-
ranging applications of PSU in water treatment are often limited by its inherent
hydrophobicity and non-wetting characteristics that facilitate the hydrophobic interaction,
deposition and adsorption between the surface of PSU membranes and microorganisms or
lipophilic foulants in the feed solution which in turn leads to serious membrane biofouling
[8,9] resulting in poor permeation and diminishing of permeate flux, increasing maintenance
costs, alteration of membrane selectivity and durability. Therefore, there is growing demand
for fabrication of antifouling UF membranes through an enhancement of the hydrophilicity of
PSU surface via physical or chemical refinements. So far, surface grafting, surface coating
and blending are the most common techniques employed for enhancing membrane surface
hydrophilicity and antifouling efficacy, accordingly [10,11]. Recently, surface modification
by blending of the host membrane matrix with hydrophilic or amphiphilic macromolecular
additives revealed it as a simple and an effective method for fabrication of hydrophilic
antibiofouling membranes [12]. For instance, Poly-(ethylene glycol)-based and
polyzwitterionic architectures of significant hydration capacity are effectively used as
hydrophilicity fine-tuning additives [13].
Among natural biopolymers, chitosan (CS), a copolymer of glucosamine (GlcNH2) and
N-acetylglucosamine (GlcNHAc) blocks, can offer a key starting material for fabrication of
ideal promising eco-friendly membrane antibiofouling modulators owing to its wide-
spectrum antialgal, antimicrobial efficacies [14], amazing antibiofouling properties [15], and
superior film-forming ability. Furthermore, CS offers a green protocol to combat biofouling
as it is produced by mining of marine wastes (e.g., shrimp- and crab-shells) [16]. However,
application of neat CS for the blended membrane technology is restricted due to its limited
2

ACCEPTED MANUSCRIPT
solubility and lower thermo-mechanical stability [17]. Thus, surface-functionalization of CS
was addressed to overcome these aforementioned challenges and construct surface-
functionalized CS which may act as a key contributor for improving the hydrophilicity and
antibiofouling behaviors of UF membranes [18,19].
Notable, polymeric ionic liquids (PILs) have been used to fabricate diverse “smart”
materials [20,21] for various applications in gas separation, membranes technologies,
electrochemical energy devices, antimicrobials, catalysis, stimuli-responsive materials,
carbon materials, sensors [22] and wettability‐switchable materials [23]. Recent works
revealed that surface functionalization of membrane with PIL brushes can offer undeniable
engineering and economic advantages over the native membrane including tunable charge,
wettability and antifouling properties. For instance, Ye et al [24] and others [25,26] reported
that PIL brushes could be reversibly switched the surface wettability from hydrophilicity to
hydrophobicity and synergistically enhanced the antimicrobial and antifouling properties of
the surface as compared with traditionally polymer terminals. Moreover, the antimicrobial
and antibiofouling efficacies of PIL brushes could be fine-tuned by exchanging their counter
anions. Interestingly, the hexafluorophosphate-based poly(ionic liquid) coated Titania
nanoparticles (TNPs) exhibited excellent antibacterial activity in comparison with pristine
TiO2 NPs. Moreover, TNPs-based membranes displayed superior antibacterial, photocatalytic
effects [27] and enhanced antifouling performance [28].
Inspired by previous outstanding facts and in our endeavor toward the designing and
fabrication of novel architectures for bioapplications [14a,15a,29] we aimed in this work to
design a simple efficient protocol for preparing an eco-friendly anti-biofoulant (based on a
poly-ionic liquids-grafted chitosan Schiff base, PILCSB) and TNPs as synergistic (anti-
microbial and anti-biofouling) modulator for a PSU membrane (Fig. 1) which may
significantly improve the anti-biofouling and filtration performance of new MMMs.
3

ACCEPTED MANUSCRIPT
Fig. 1: Diagrammatic representation for the functionalization of the PSU surface with
PILCSB, PEG and TNPs to fabricate the target MMMs, PSU@PILCSB@PEG@TNPs.
2. Materials and methods
Instrumentation, sources of materials, extraction of CS from shrimp shells and
preparation details of TNPs and 4-methoxypyridinium ethoxysalicylaldehyde ionic liquid
((EtO)Sal-MeOPy+X–, 3a,b) are available in the electronic supplementary information (ESI†).
2.1.Synthesis of 5-(4-methoxypyridinium hexafluorophosphate)-ethoxysalicylidene
chitosan (PILCSB)
CS (1 g) was dissolved in 100 mL of a mixture of ethanol and 1% aqueous acetic acid
–
(1:1 v/v) by stirring at 50 °C for 30 min. (EtO)Sal-MeOPy+PF6 , 3b (equivalent to the NH2-
content in CS) was dissolved in a hot ethanol (30 mL) and then the obtained solution was
added portionwise to a stirring homogeneous solution of CS over a time of 30 min at the
same temperature. Then, the reaction temperature was raised to 80 °C and the reaction
mixture was further stirred at this temperature for 24 h. The desired product was isolated
from the reaction media by adding an excessive amount of ethyl acetate (AcOEt) coupled
with ultrasonication at r.t. for 5 h. The obtained product (PILCSB) was filtered and then
washed with EtOH:AcOEt mixtures (30:70, 20:80, and 0:100 v/v) (3 x 10 mL). Finally,
PILCSB was dried under vacuum at 40 °C for 24 h to obtain the desired PILCSB: It is
obtained as a yellowish-orange powder, Yield (2.13 g, 97.9%). FTIR (KBr, cm-1): 3445 (vs,
br), 3211 (m, br), 1658 (s, sh), 1636 (vs, sh), 1532 (m, sh), 1379 (m, sh), 1284 (m, sh), 1158
1
(s, sh), 1065 (m, sh), 896 (m, sh), 836 (s, sh) 767, 656 (m, sh). H NMR (600 MHz, 1%
CD3COOD/D2O)60 ºC δ (ppm): 11.23 (s, 1H), 10.89 (s, 1H), 8.92 (d, J = 7.1 Hz, 2H), 8.51 (d,
4

ACCEPTED MANUSCRIPT
J = 7.3 Hz, 4H), 8.28 (d, J = 7.2 Hz, 1H), 7.99 (d, J = 8.3 Hz, 4H), 7.80-7.67 (m, 4H), 5.95 (s,
4H), 5.23 (d, J = 7.6 Hz, 1H), 4.39 (q, 4H), 4.14 (br, s, 2H), 4.01 (s, 6H), 3.91-3.79 (m,2H),
3.65 (t, J = 7.1 Hz, 2H), 3.53 (br, s, 2H), 3.32-3.19 (m, 4H), 2.78 (t, J = 8.1 Hz, 2H), 2.45
(dd, J = 13.8, 8.4 Hz, 3H) , 1.39 (t, J = 7.6 Hz, 6H). 13C NMR (151 MHz, 1%
CD3COOD/D2O)60 ºC δ (ppm): 178.35, 178.10, 176.61, 164.55, 163.28, 153.48, 152.26,
151.18, 150.03, 148.49, 148.14, 147.26, 146.31, 134.85, 134.09, 127.86, 126.91, 118.99,
118.19, 110.77, 109.88, 109.11, 89.71, 85.42, 83.36, 81.51, 80.49, 79.13, 78.22, 76.26,
75.63, 75.21, 74.37, 73.45, 72.28, 71.31, 71.10, 68.34, 65.43, 65.18, 62.06, 58.38, 56.41,
31
2
19.89 and 18.63. P NMR (202 MHz, DMSO-d6): -159.38 to -117.33 ppm (septet, JPF
=
19
1
711.18 Hz). F NMR (470 MHz, DMSO-d6): -67.81 to -64.78 ppm (doublet, JPF = 711.24
Hz).
2.2.Preparation of neat PSU membrane (M0)
All membranes have been fabricated via modified non-solvent induced phase inversion
(NSIPI) and slow evaporation methods. To prepare the casting solution, a certain amount (3.8
g) of PSU was dissolved in NMP (15.2 g, 15.66 mL) under vigorous stirring at 60 °C to
obtain a homogeneous PSU solution which was further stirred at 300 rpm for 8 h. Then, the
casting solution was debubbled using vacuum for 15 min. Afterwards, the bubble-free
solution was then casted on either a nonwoven polyester fabric (novatex2483) and
immediately exposed to warmed water vapor for 15 min and then immersed into a milli-Q
water as a non-solvent at r.t. for NSIPI, or onto 2.5 cm Petri dishes, for slow evaporation in
vacuum oven at 50 °C/ 2 days. Noteworthy, the membranes obtained by NSIPI should be
stored in a milli-Q water for 3 days for complete removal of a residual NMP.
2.3.Fabrication of UF MMMs (MMM1, MMM2, MMM4, MMM5)
General procedure to fabricate PSU@CS (MMM1) and PSU@PILCSB (MMM4)
membranes (see Table 1 for the membrane composition) is described as follows: A 2%
solution of CS is obtained by dissolving 1 g CS in 50 mL of 1% aqueous AcOH (solution of
PILCSB obtained by dissolving 0.10 g in 5 mL NMP). PSU (3.8 g) was dissolved in (9.20 g,
9.50 mL) of NMP by stirring at 60 °C for 4h to obtain a clear homogeneous solution. Then,
5.0 mL of the obtained CS or PILCSB solution was added dropwise to the PSU solution
under vigorous stirring at 1100 rpm, maintaining the temperature at 60 °C. Thereafter, further
0.93 mL (0.90 g) of NMP was added. While CS was being added, it is re-precipitated
resulting in a formation of turbid solution which was stirred vigorously, at 900 rpm, at 70 °C
5

ACCEPTED MANUSCRIPT
for 12 h to obtain clear viscous casting solution. Then, this casting solution was deaerated
under vacuum to obtain bubbles-free casting solution. Afterwards, the bubble-free solution
was then casted on either a nonwoven polyester fabric (novatex2483), for NSIPI, or onto 2.5
cm petri dishes, for slow evaporation, as described above. The fabricated MMMs were
washed several times with distilled water and then milli-Q water before being dried at 30 °C.
Similar procedures were employed for the preparation of the PSU@CS@PEG (MMM2) and
PSU@PILCSB@PEG (MMM5) membranes by replacing definite amount of NMP with
equivalent amount of PEG.
Table 1. Composition (W %) of the prepared MMMs.†
Membrane ID
M0
PSU
20.0
20.0
20.0
20.0
20.0
20.0
20.0
NMP
80.0
53.2
53.0
52.9
79.5
79.3
79.2
AcOH
–
PEG
–
CS
–
PILCSB
TNPs
–
–
–
–
MMM1
MMM2
MMM3
MMM4
MMM5
MMM6
26.3
26.3
26.3
–
–
0.5
0.5
0.5
–
0.2
0.2
–
–
–
–
0.1
–
0.5
0.5
0.5
–
0.2
0.2
–
–
–
–
0.1
†
PSU, polysulfone; MMM, mixed matrix membrane; NMP, N-methyl-2-pyrrolidone; AcOH, 1% acetic acid;
CS, chitosan; PEG, polyethylene glycol; TNPs, TiO2 nanoparticles.
2.4.Fabrication of nanocomposite mixed matrix membranes (MMM3) and (MMM6)
Generally, 2 wt% solutions of CS (2 g/100 mL) and PILCSB were prepared by
dissolving 0.1 g of CS and PILCSB, separately, in 5 mL of 1 wt% aqueous acetic acid and 5
mL of NMP, respectively. To these solutions, PEG was added with continuous stirring at 500
rpm to obtain CS@PEG and PILCSB@PEG. Then, two equal amounts (3.8 g) of PSU were
dissolved separately in two quantities (9.20 g, 9.50 mL) of NMP by stirring at 60 °C/ 500
rpm for 4 h to obtain two homogenous solutions. Afterwards, previously prepared CS@PEG
and PILCSB@PEG solutions were added separately to the PSU solutions under vigorous
stirring, 1100 rpm, at 60 °C. Then, additional 0.93 mL (0.90 g) of NMP was added. The
obtained turbid solution was vigorously stirred at 70 °C for 12 h to obtain clear highly
viscous solutions. Thereafter, TNPs were added to these solutions under continuous stirring at
60 °C for 1h followed by sonication for 1 h at the same temperature. Then, the casting
solutions were deaerated under vacuum and casted on either a nonwoven polyester fabric
(novatex2483), for NSIPI, or onto 2.5 cm petri dishes, for slow evaporation, as described
above.
6

ACCEPTED MANUSCRIPT
2.5.Membranes structural and surface characterization
2.5.1. ATR-IR analysis
Attenuated Total Reflection-Fourier Transform Infrared Spectroscopy (ATR-FTIR)
spectrometer (BRUKER Tensor-37) was used to examine the surface-functionalization of the
new membranes in the range of 4000–400 cm−1. A diamond prism was used as the waveguide
and membrane holder. The membrane samples were dried at 40 °C/ overnight before
analysis. The following abbreviations were used to specify the spectral bands: vs (very
strong), s (strong), m (medium), w (weak), very weak (vw), sh (shoulder) and br (broad).
2.5.2. Morphological survey of the membranes
The cross-sectional and surface morphologies of the neat membrane and modified
membranes were compared on the basis of scanning electron microscopy (SEM)
micrographs. These SEM samples were prepared by breaking the membranes under liquid N2
to produce a generally consistent and clean cut. Then, the membranes were spin-coated with
thin film of gold. Thereafter, the membrane samples were mounted on brass plates. Cross-
sectional micrographs for our membranes were picked-up by an ESEM Quanta 400 FEG
SEM equipped with a secondary electron detector (SED) and operated at 20 keV.
2.5.3. Hydrophilicity, water swelling (uptake) and contact angles of the membrane surface
Hydrophilicity of our new membranes was estimated by measuring the water contact
angle (CA) using a steady contact angle measuring equipment (HHU, Düsseldorf, Germany).
A schematic diagram of the measurement of CA of our membranes is depicted in Fig. S1.
Multiple CA values have been measured and the average value was calculated with standard
deviation.
The pH dependent swelling or water uptake features of the MMMs were examined
following the procedure reported earlier in the previous work [30]. Briefly, a pre-weighed
and ultra-dry membrane sample of weight Wd and 1 cm2 area was immersed in phosphate
buffer solutions with different pH values of 3, 5, 7, 9 and 11 for 24 h. Afterwards, the wet
membrane was removed from the solution and the excess water on the outer surface of
membrane was discarded using a blotting paper. Thereafter, the MMM sample was re-
weighed as (Ww) and the percentage of swelling or water uptake was calculated using
equation (1):
Ww − Wd
(
)
( )
ퟏ
% 퐒퐰퐞퐥퐥퐢퐧퐠 water uptake = (
) x 100
Wd
2.5.4. Membranes porosity
7

ACCEPTED MANUSCRIPT
A QUANTACHROME POREMASTER 60-GT was used for pore analysis by means of
mercury porosimetry. The basis of this method is the so-called Washburn equation, which
used for a non-wettable liquid (mercury) represents the dependence of the pressure (to be
filled) or empty (extrusion) pore diameter of the applied pressure. With the POREMASTER
60-GT, filling of the measuring cells before the actual measurement is done in a horizontal
position: This prevents a static pressure of the heavy mercury (density approx. 13.5 g/cm3) on
the sample and an undetected filling of large pores. Two strips of approximately 8 × 30 mm
were used for the measurement per sample. The samples were not previously dried but
measured in the initial state. The results of the measurements are shown as an intruded
volume versus pressure or versus pore diameter.
2.6.Membrane Performance Characterization
2.6.1. Pure water permeation ultrafiltration experiments
The PWF of the MMM with an effective area of 5 cm2 was carried out using a cross-flow
ultrafiltration laboratory apparatus (Fig. 2). The membrane was soaked in milli-Q water for
24 h before running the water permeation experiment.
Fig.2: Schematic diagram of the permeation experimental apparatus: (1) N2 gas; (2,4) pressure
gauges; (3,7) valves; (5) feed tank; (6) membrane; (8) permeate reservoir; (9) electronic balance; (10)
computer.
Afterwards, membrane was compacted at a trans-membrane-pressure (TMP) of 0.10 MPa
for 30 min. Then, the time dependent PWF was measured at 0.3 MPa. The permeate samples
were collected after 15 min of exposure of a membrane to the target TMP at 26 °C and the
amount of water permeate was weighted every 10 min. Then the PWF (Jw) was calculated
using equation (2):
8

ACCEPTED MANUSCRIPT
Q
퐽w = (
)
(ퟐ)
A∆t
Where Q = volume of pure water collected during time Δt (h) using a MMM of area A
(m2) and Jw is expressed in L/m2h.
2.6.2. Antifouling assessment
Bovine serum albumin (BSA) has been chosen as a model fouling-induced protein to
examine the antifouling efficacy of new modified MMMs [31].
BSA ultrafiltration experiments
The membrane fouling propensity was evaluated during the ultrafiltration of BSA
aqueous solution. Initially, all MMMs were compacted at 0.1 MPa for 30 min. Then, the
TMP was raised to 0.3 MPa. After 90 min of a water flow, the steady state water flux was
calculated and assigned as Jw1 (L/m2h). Afterwards, the pure water was replaced by a BSA
aqueous solution (0.8 g/L). BSA flux at the end of the next 90 min was calculated and
assigned as JBSA (L/m2h). BSA rejection (R%) was estimated by UV-Vis spectroscopy at a
wavelength of 280 nm and calculated using equation (3):
Permeate
BSA
퐂
푹% = (1 −
) x 100
(ퟑ)
Feed
BSA
퐂
Permeate
BSA
Feed
BSA
Here, 퐂
(mg/mL) and 퐂
(mg/mL) represent the concentration of BSA
solution in permeate and feed, respectively. After BSA UF experiment, the MMM was
flushed with milli-Q water for 15 min before measuring the steady state PWF again a 90 min
and assigned as Jw2 (L/m2h). Finally, the membrane antifouling efficacy was calculated as a
flux recovery ratio (FRR) using equation (4):
퐽푤2
푭푹푹% = ( ) x 100
(ퟒ)
퐽푤1
Eventually, the antifouling capacities of these MMMs can be predicted from several
ratios including FRR (%) and total fouling Rt (Rt = 1 − JBSA/ Jw1), reversible fouling Fr (Fr =
(Jw2 − JBSA)/ Jw1) and irreversible fouling Fir (Fir = (Jw1 − Jw2)/ Jw1) [32].
3. Results and Discussion
3.1.Chemistry
Multiple chemical strategies (chloromethylation, quaternization, anion metathesis and
Schiff-base condensation, as well) (Scheme 1) were utilized for the surface modification of a
natural biopolymer chitosan (CS). We have prepared a new hydrophilic antifouling agent,
9

ACCEPTED MANUSCRIPT
poly-methoxypyridinium ethoxysalicylidene grafted-CS (PILCSB), from methoxypyridinium
-ethoxysalicylaldehyde hexafluorophosphate (3b), which was in turn obtained from 3-
ethoxysalicylaldehyde (1) according to Scheme 1. Chloromethylation of 1 was carried out
with hydrochloric acid and polyoxymethylene (POM) as a formaldehyde precursor in a
catalytic zinc chloride environment under aqueous biphasic conditions. The obtained
chloromethylaldehyde (2) was then effectively aminated with 4-methoxypyridine (4-MeOPy)
to yield methoxpyridinium-based salicylaldehyde chloride (3a). Subsequent chloride-
hexafluorophosphate anion metathesis of 3a using hexafluorophosphoric acid yielded the
corresponding hexafluorophosphate salt (3b).
Scheme 1 Schematic diagram for different chemical strategies used in the synthesis of poly-
methoxypyridinium ethoxysalicylidene brushes-based CS (PILCSB).
Eventually, the desired poly-methoxypyridinium ethoxysalicylidene brushes-based CS
(PILCSB), was obtained by a simple efficient Schiff base condensation of ionic
10

ACCEPTED MANUSCRIPT
salicylaldehyde hexafluorophosphate (3b) with the natural biopolymer, CS. This new
antifoulant was isolated in excellent overall yield of 97.9%, structurally characterized based
upon elemental analysis, ATR-FTIR, NMR (1H, 13C, 19F, 31P) and morphologically examined
by SEM micrographs.
3.2.Structural characterizations of CS and PILCSB
3.2.1. Structural characterizations of CS
Based on the elemental and spectral data for CS, the degree of deacetylation (DDA) was
found to be ~75.4% (See ESI†). Thus the plausible building unit of CS is a copolymer from
GlcNHAc and GlcNH2 kept at ca. 1:3 molar ratio, i.e, (GlcNHAc)0.246(GlcNH2)0.754 or
.
(C8H13NO5)0.246 (C6H11NO4)0.754 H2O.
3.2.2. Structural characterizations of PILCSB
Microanalytical data and degree of substitution DS (Iminization) for PILCSB
During the synthesis protocol of PILCSB, the experimental conditions were optimized for
achieving almost complete conversion of CS into the corresponding PILCSB. Thus, the
experimental yield of PILCSB may be plausibly used for calculation of its degree of
substitution (DS) (iminization) according to the reaction depicted in Scheme 2;
Scheme 2 Schematic conversion of CS into the corresponding Schiff base (PILCSB),
antifoulant.
Here, Schiff base condensation of (1.00 g) CS with 3b yielded 2.13 g of PILCSB which
means a 113% massive increase in the weight of CS and the MW of the building block of
PILCSB, accordingly. Thus, the MW of the resulting PILCSB is higher than that of CS
(MWCS = 189.51 g/mol) by 113%, i.e. MW4b = 403.84 g/mol which represents the MW of the
monomeric
building
block
suggested
for
PILCSB
in
Scheme
2,
(C8H13NO5)0.246(C6H11NO4)0.754-x(C22H27F6N2O8P)x(H2O). Solving this formula gives the
value of DS as 49.7% which is in good agreement with the results obtained from CHN
analysis
for
PILCSB.
Anal.
Calcd
for
(C8H13NO5)0.246(C6H11NO4)0.257
(C22H27F6N2O8P)0.497(H2O) (MW = 403.85 g/mol): 42.96; H, 5.35; N, 5.19. Found for
PILCSB (DS = 49.7%) C, 42.85; H, 5.42; N, 5.03. So, on the basis of elemental analyses, the
suggested structure for the desired antifoulant, poly-methoxypyridinium ethoxy- salicylidene
brushes-based CS (PILCSB), is depicted in Scheme 3.
11

ACCEPTED MANUSCRIPT
Scheme 3 Suggested structural formula for PILCSB.
FTIR
Changes in the ATR-FTIR signatures of PILCSB in comparison to the parent CS (Fig.
S2, ESI) demonstrate the successful covalent grafting of the hydrophilic poly-
methoxypyridinium ethoxysalicylidene brushes on the surface of CS fibers. Where, the
absorption at ca. 3438 cm−1 along with two maxima at 1644 cm−1, characteristic for
superimposed C=O (amide I) and azomethine (H–C=N) stretching vibrations, and 1277 cm−1,
characteristic for aryl‒O vibration, can be attributed to the overlapping of phenolic O-H and
amide N-H stretching modes. Pertinacity of NH peak to participate in the spectrum of
2
PILCSB, however, with a very feeble extent compared to that of CS, confirms the
predominance poly-methoxypyridinium ethoxysalicylidene brushes on the CS surface, via
partial Schiff base condensation, with minor contribution of neat glucosamine (GlcNH2)
−
units. Three predominant peaks (C=N stretching: 1526 cm−1; PF6 stretching: 840 cm−1 and
bending: 740 cm−1) are assignable to the methoxypyridinium terminals.
NMR spectroscopy
Consistent with a successful surface modification of CS with poly-methoxypyridinium
1
ethoxysalicylidene brushes is the appearance of novel signals in the H NMR spectrum of
PILCSB compared to the one of CS such as the highly deshielded peaks at δ = 12.28 and
8.91 ppm arising from phenolic OH involved in an intramolecularly H-bonded environment
[33] and aldimine protons, respectively. A set of multiplets in the range of 8.36‒7.24 ppm is
due to the resonance of aromatic protons. The 13C NMR spectrum for PILCSB offers further
evidence for the successful chemical anchoring of poly-methoxypyridinium ethoxy-
salicylidene compartments to the chitosan skeleton as revealed from the observation of two
low-field resonance signals at 166 and 158 ppm attributed to phenolic and azomethinic
carbons, respectively. The hexafluorophosphate ion was authenticated by a septet signal
centered at ca. -138 ppm with 2JPF = 711.18 Hz coupled with a doublet signal centered at ca. -
12

ACCEPTED MANUSCRIPT
1
31
19
65.5 ppm with JPF = 711.24 Hz in their P/ F NMR spectra which are characteristic for
−
PF6 counter anions.
3.2.3. Morphological and topographical characterizations of PILCSB
The morphology of the texture for the PILCSB was investigated from SEM micrographs
(see Fig. S3, ESI), which revealed a significant difference between the surface morphology of
PILCSB and CS. Where CS exhibits a flat surface with a smooth and dense texture while
PILCSB has a rough sponge-like texture. This could be attributed to the expected
interactions between CS matrix and PILCSB through H-bonding and imine linkages leading
to the formation of many hydrophilic sites at the surface with cross-sectional pores and micro
voids network.
3.3.Morphological and textural properties of TNPs
The morphology of TNPs prepared starting from TiCl4 by a solution-based method was
probed using SEM analysis (Fig. 3, Fig S4). SEM image revealed that most of the TNPs were
spherical with a regular diameter ranging from 39 nm to 57 nm.
(a)
(b)
Fig. 3 SEM micrograph of TNPs; (a) General view, (b) an approximate grain-size range (in
m) of TNPs.
The phase purity of TNPs was estimated from the XRD diffractogram (Fig. 4a). All
observed major peaks are well recorded to the TNPs in an anatase phase as indicated by the
standard (JCPDS card No. 21-1272).
13

ACCEPTED MANUSCRIPT
Fig. 4 (a) X-ray diffraction patterns (Cu-Kα radiation) of TNPs. (b) N2 adsorption–desorption
isotherms along with the corresponding pore size distributions (inset) of the TNPs at 77 K.
The specific surface areas and pore size distributions of the as-synthesized TNPs was
established using nitrogen adsorption–desorption isotherm (Fig. 4b) which reflect a type IV
isotherm with H2 hysteresis loop according to Brunauer–Deming–Deming–Teller (BDDT)
classification [34]. This hysteresis loop implies that the TNPs have mesoporous structure,
with specific surface area of 94 m2g‒1 and the pore size distribution curve (inset in Fig. 4b)
shows a wide range of pore size from 3.3 to 25 nm with a maximum population of ~3.3 nm.
3.4.Membranes characterization
3.4.1. ATR-FTIR
ATR-FTIR spectroscopy can provide information about the surface and near-surface
composition of the membranes. Where the presence of CS or new antifoulant (PILCSB) onto
the outer surface of PSU was evident by ATR-FTIR spectroscopy. In comparison to the FTIR
spectra of pure PSU and PILCSB, PSU@PILCSB@(PEG)@(TNPs) (MMM4, MMM5,
MMM6) membranes exhibit collective infrared spectral signatures of their woven
components, confirming successful fabrication of MMMs. The ATR-FTIR spectra of the new
membranes (Fig. 5) revealed common features represented by the characteristic peaks around
3420 cm−1 corresponding to the amide N‒H and alcoholic/ phenolic OH stretches of
PILCSB. The amide N-H peaks is in line with the characteristic for amide C=O peak around
1670 cm−1. The OH peak is in line with the Ar‒O vibration mode around 1275 cm−1. The
vibration peaks characteristic for PSU are seen around 1294 and 1150 cm−1, assignable to
asymmetric and symmetric stretching vibrations, respectively, of the O=S=O group, along
with a peak observed around 1240 cm−1 attributable for the C‒O‒C vibration.
14

ACCEPTED MANUSCRIPT
Fig. 5 ATR-FTIR patterns for comparison of the FTIR signatures of MMMs with parents
PILCSB and PSU.
3.4.2. Morphology of the membranes
The overall thicknesses of the newly fabricated MMMs were in the range of 80–110 µm.
The surface and cross-section morphologies of these new MMMs were inspected by SEM.
The cross-sectional SEM micrographs (Fig. 6) revealed that all membranes exhibited
asymmetric porous structure of a dense skin layer and a highly porous sub-layer containing
sponge-like structure (for CS-based MMMs) or macrovoid-type structure (in case of PILCSB
-based MMMs). These changes in membrane morphologies could be ascribed to the
replacement of CS with a poly-methoxypyridinium ethoxysalicylidene brush-based CS, a
violent hydrophilic antifouling additive, which enhances the hydrophilicity and subsequently
the affinity of the PSU@PILCSB@PEG@(TNPs) (MMM6) casting composite which
already dissolved in NMP to the non-solvent (water) coagulation bath compared to
PSU@CS@PEG@(TNPs) (MMM3) which reduce the mutual diffusivity between casting
solvent (NMP) and non-solvent (water). This prolonged mutual diffusion allowed longer
phase inversion time along with lower segregation rate of PILCSB from the bulk casting
solution up to the NMP-water interface and self-induced pore growth, as well. Moreover, the
hydrophilic nature of the TNPs facilitated the mass transfer between the NMP and the water
during phase inversion resulting in the development of longer macrovoids and subsequently
15

ACCEPTED MANUSCRIPT
the enhancement of overall membrane porosity [35].
The successful formulation of TNPs into the membrane matrix was proved by EDX
results (mapping and spectra) as depicted in Fig. S6 (ESI†). All new MMMs are typical UF
membranes with micrometer-scale pores upon the surface layer and micron-sized macrovoids
embedded across the membrane network.
Fig. 6 Surface and cross-sectional SEM micrographs of: (a, b) M0, (c, d) MMM2, (e, f)
MMM3, (g, h) MMM4, (i, j) MMM6.
3.4.3. Porosity
The pore size distribution (PSD) plot for MMM2 and MMM5, as representative examples
of MMMs is depicted in Fig. 7. As shown in in this figure, MMM2 possess "channels and
pores" where the surface shows many channel windows 10-100 µm. Inside of the walls
between channels, there are spherical pores with a hierarchical size distribution ranging from
internal smaller pores with ~10 µm diameter to external larger pores of ~100 µm diameter.
The MMM5 texture exhibited asymmetric pore distribution with large pores of 50-100 µm in
the center and small pores of 10-20 µm to the outside of the membrane. Moreover, the
surfaces of MMM2 and MMM5 show some pore windows 5-10 µm, while, the untreated
membrane (M0) shows slightly rough cross-section but no pores as revealed from its SEM
micrograph (cf. Fig. 6)
16

ACCEPTED MANUSCRIPT
Fig. 7 Pore size distribution (PSD) curve which is calculated from the normalized volume
curve by differentiation for MMM2 and MMM5 (representative examples of MMMs).
3.5.Membranes performance
3.5.1. Water uptake (membrane swelling) and contact angle measurement
Water uptake, swelling ratio and contact angle values of new MMM surfaces were
assessed to evaluate their hydrophilicity/ hydrophobicity features. As revealed from Fig. 8a,
the water uptake and swelling ratio values of PILCSB-blended MMMs were higher than
those of the neat PSU membrane and CS-based PSU membranes because of the existence of
poly-methoxypyridinium ethoxysalicylidene brushes on the active layer of membrane, as
revealed from EDX (cf. Fig. S5, ESI†), which offer multiple active H-bonding sites for
interaction with water. Noteworthy, water uptake performance was changed in a pH-
dependence profile with maximum uptake under acidic conditions (pH=4) due to protonation
of the GlcNH2 fragments of CS. At pH = 4, a maximum water uptake of 83.46% was
achieved for PSU@PILCSB@PEG@TNPs (MMM6). Thus, water uptake in membranes
depends on the content of hydrophilic TNPs. Noteworthy, the addition of TNPs didn`t
significantly change the hydrophilicity of the PSU membrane as revealed from water contact
angle measurements depicted in Fig. 8b, however, PILCSB brushes coated TNPs was greatly
enhanced the MMM6 hydrophilicity.
17

ACCEPTED MANUSCRIPT
Fig. 8 (a) pH dependent water uptake of MMMs in comparison with neat PSU membrane
M0. (b) Contact angle of MMMs compared to neat PSU membrane.
As shown in Fig. 8b, all woven membranes had water contact angles lower than 90°,
indicating that the highly hydrophobic properties of the parent PSU (water contact angle =
93.48°) were decreased to be somewhat more hydrophilic as a result of its surface refinement
with hydrophilic architectures (i.e., CS or PILCSB, PEG, TNPs). The membranes MMM4-6
modified with PILCSB, exhibit somewhat lower water contact angles compared to those
modified with CS (MMM1-3) because the multiple hydrophilic fragments in the poly-
methoxypyridinium ethoxysalicylidene brushes of PILCSB impart higher hydrophilicity than
CS. Moreover, the entrapment of TNPs on the matrix of the membrane led to an enhancement
of membrane hydrophilicity as revealed from the observed water contact angle (57.35°) for
MMM6.
3.5.2. Permeation properties
The permeation performance of the pristine PSU membrane (M0) and the MMMs were
determined by pure water (PWF) and BSA filtration experiments. From the PWF and BSA
rejection data for the virgin PSU membrane and the MMMs presented in Table 2, it is
noticeable that the virgin membrane M0 manifested an extremely low water flux of 60 L/m2 h
coupled with the elevated level of BSA rejection, 89.95%, under an operation pressure of 0.3
MPa, which is in accordance with its higher hydrophobicity. The water permeability of the
PSU-based composite MMMs was distinctly enhanced by integration of the hydrophilic
biopolymer CS or the amphiphilic copolymer (PILCSB), pore stabilizing agents (PEG) and
TiO2-NPs into the matrix of the membrane. Particularly, the PWF of MMM6 is 158.10 L/m2
h (~2.7 times higher than that of the native PSU membrane), moreover, it has the maximum
BSA rejection, 36%.
18

ACCEPTED MANUSCRIPT
Table 2. PWF (Jw1) and BSA rejections of the membranes a
Membrane ID
M0
composition
pure PSU
PWF (L/m2h)
BSA rejection (%)
69
76
90
68
53
52
43
37
36
MMM1
MMM2
MMM3
MMM4
MMM5
MMM6
PSU@CS
PSU@CS@PEG
95
PSU@CS@PEG@TNPs
PSU@PILCSB
99
129
144
158
PSU@PILCSB@PEG
PSU@PILCSB@PEG@TNPs
a PWF = pure water flux; BSA = Bovine serum albumin.
It is recognized that the water permeability of the membrane is governed by its physical
(hydrophilicity/ hydrophobicity), geometrical (porous network, pore size and roughness)
and chemical (liquid-solid interactions) parameters [36]. In this context, enhancing the
hydrophilicity of the surface of PSU membrane by blending it with a hydrophilic additive
(CS or PILCSB) will reduce the membrane affinity for physisorption of organic
contaminants (such BSA). A hydrophilic additive will also promote the hydrophilic pore-
water interaction within the porous framework and, thus, improve the water mass
transport. The BSA rejection was dramatically decreased as the hydrophilic additives (CS,
PILCSB, PEG and TNPs) were incorporated into the PSU membrane as presented in Table 2.
Specifically, MMM6 which exhibits promising performance because of it combines PILCSB
with polar ionizable moieties that induce surface charges which promote wettability of the
membrane while diminishing BSA-membrane interaction.
3.5.3. Antifouling properties of membranes.
A consecutive water-BSA-water permeation experiment was used to assess the
antifouling performance of the composite membranes (MMMs) in comparison with the virgin
PSU membrane (M0). As shown in Fig. 9, the permeation flux for the M0 dropped
dramatically when the pure water permeation was followed with the fouling-inducing model
BSA solution. This drop may be attributed to the hydrophobic surface which promotes
membrane fouling via hydrophobic (M0-BSA) interaction. On the other hand, the MMMs
exhibited lower flux decline than the neat PSU membrane M0 suggesting that the composite
membranes have lower fouling propensity than the pure PSU membrane. This could be
assigned to an increase of the membrane surface hydrophilicity by blending with hydrophilic
fillers which reduce its fouling propensity and diminish the flux declining degree,
accordingly. Noteworthy, the composite membranes (MMMs) exhibited a higher relative
19

ACCEPTED MANUSCRIPT
fluxes recovery than M0 after simple hydraulic cleaning as revealed from the water
permeation following BSA filtration (section (III) in Fig. 9). These results suggest
reversibility of the fouling for the MMMs which is in good agreement with their enhanced
surface hydrophilicity.
Fig. 9. Flux decline and recovery results for the as-fabricated MMMs. This permeation
experiment contains three phases: (I) pure water permeation, Experimental conditions:
Initially, a 5 cm2 membrane was compacted at 0.10 MPa, a trans-membrane-pressures (TMP),
for 30 min. Then, the time dependent pure water flux (PWF) was measured at 0.3 MPa. The
permeate sample collection was started after 15 min of exposure to target TMP at 26 °C and
the permeate was weighted every 10 min, and operation period of 90 min. (II) BSA solution
(model foulant) filtration, and (III) pure water permeation after water flushing.
Reversible fouling (Fr): arises from reversible adsorption/ deposition of a foulant protein
(BSA) and can be easily removed by simple water flushing. Irreversible fouling (Fir) is due to
the irreversible adsorption of a protein (BSA) and can only be eliminated by chemical
treatment. Thereafter, quantitative assessment of the antifouling capacities of these
membranes have been addressed based upon several ratios including flux recovery ratio
(FRR), total fouling (Ft), reversible and irreversible fouling (Fr, Fir) as depicted in Fig. 10. It
is clear from Fig. 10 that the FRR(%) values for the MMMs (67-89%) are much higher than
those of nascent PSU (M0), confirming the lower fouling propensity of the MMMs [37]. This
indicated that the MMMs could keep a higher water flux even after a BSA UF process [38].
Collected Ft, Fr and Fir values for the MMMs provide further evidence for their promotion of
antifouling performance as revealed from Fig. 10, where these values are greatly reduced by
blending of PSU with the antifoulants (PILCSB and TNPs) assignable to the increased
20

ACCEPTED MANUSCRIPT
hydrophilicity of MMMs.
Fig. 10. A summary of total fouling (Ft), reversible fouling (Fr), irreversible fouling (Fir), and
flux recovery ratio (FRR) for neat PSU (M0) and composite MMMs with CS, PILCSB and
TNPs.
Consequently, the hydrophilic fillers (PILCSB and TNPs) are believed to form a
hydration barrier that diminished the fouling model (BSA) adsorption.
4. Conclusion
In our work, PSU UF-membrane was physically modified with chitosan (CS) and poly-
ionic liquid-grafted chitosan Schiff base (PILCSB) and TNPs in presence of pore-stabilizing
agent, PEG. The effect of these additives on the morphology, porosities features, water flux,
protein rejections and antifouling performances of the modified membranes (MMMs) was
investigated. The results revealed that incorporation of all additives into a mixed matrix
membrane MMM6 (PSU@PILCSB@PEG@TNPs) was significantly enhanced membrane
texture and permeation performance with and improved pure water flux by 2.5 fold in
comparison to the neat PSU membrane (M0). Moreover MMM6 exhibited the highest
resistance to biofouling for the UF applications.
ACKNOWLEDGMENT
The authors gratefully acknowledge the financial support of the Federal German Ministry of
Education and Research (BMBF) in the project Optimat under grant no. 03SF0492C
APPENDIX A. SUPPLEMENTARY DATA
Supplementary data (experimental and spectral data) associated with this article are available
with the article through the journal Web site, at doi:
21

ACCEPTED MANUSCRIPT
REFERENCES
[1] Human Development Report, Chapter 4, United Nations Development Programme (UNDP)
(2006).
[2] Urban Urgency, Water Caucus Summary, World Water Council (WWC), Marseille, France
(2007).
[3] M. Mulder, Basic Principles of Membrane Technology, Kluwer Academic Publishers, London
(1996).
[4] (a) Y. H. Cho, H. W. Kim, S. Y. Nam, H. B. Park, Fouling-tolerant polysulfone–poly(ethylene
oxide) random copolymer ultrafiltration membranes, J. Membr. Sci., 37 (2011) 296-306;
(b) N. Nady, M. C. R. Franssen, H. Zuilhof, M. S. M. Eldin, R. Boom, K. Schroën, Modification
methods for poly(arylsulfone) membranes: a mini-review focusing on surface modification,
Desalination, 275 (2011) 1-9.
[5] K. J. Lee, J. Y. Jae, Y. S. Kang, J.Won, Y. Dai, G. P. Robertson, M. D. Guiver, Gas transport and
dynamic mechanical behavior in modified polysulfones with trimethylsilyl groups: effect of
degree of substitution, J. Membr. Sci., 223 (2003) 1-10.
[6] Y. Liu, Shuling Zhang, G. Wang, The preparation of antifouling ultrafiltration membrane by
surface grafting zwitterionic polymer onto poly (arylene ether sulfone) containing hydroxyl
groups membrane, Desalination, 316 (2013) 127-136.
[7] (a) J. Sikder, C. Pereira, S. Palchoudhury, K. Vohra, D. Basumatary, P. Pal, Synthesis and
characterization of cellulose acetate-polysulfone blend microfiltration membrane for separation of
microbial cells from lactic acid fermentation broth, Desalination, 249 (2009) 802-808;
(b) N. K. Saha, M. Balakrishnan, M. Ulbricht, Fouling control in sugarcane juice ultrafiltration
with surface modified polysulfone and polyethersulfone membranes, Desalination, 249 (2009)
1124-1131;
(c) R. Kumar, A. M. Isloor, A. F. Ismail, S. A. Rashidc, T. Matsuura, Polysulfone–Chitosan blend
ultrafiltration membranes: preparation, characterization, permeation and antifouling properties.
RSC Adv., 3 (2013) 7855- 7861.
[8] (a) Q. Shi, Y. L. Su, W. Zhao, C. Li, Y. H. Hu, Z. Y. Jiang, S. P. Zhu, Zwitterionic
polyethersulfone ultrafiltration membrane with superior antifouling property, J. Membr. Sci., 319
(2008) 271-278;
(b) D. Rana, T. Matsuura, Surface modifications for antifouling membranes, Chem. Rev., 110
(2010) 2448–2471;
(c) J. A. Koehler, M. Ulbricht, G. Belfort, Intermolecular forces between a protein and a
hydrophilic modified polysulfone film with relevance to filtration, Langmuir, 16 (2000) 10419-
10427.
9 (a) Q. F. Zhang, S. B. Zhang, L. Dai, X. S. Chen, Novel zwitterionic poly(arylene ether sulfone) s
22

ACCEPTED MANUSCRIPT
as antifouling membrane material, J. Membr. Sci., 349 (2010) 217-224;
(b) Y. G. Dave, A. V. R. Reddy, Preparation, characterization, acid stability and organic fouling
of poly(acrylonitrile-co-methacrylic acid) ultrafiltration membranes, Desalination, 282 (2011) 9-
18;
(c) M. P. Sun, Y. L. Su, C. X. Mu, Z. Y. Jiang, Improved antifouling property of PES
ultrafiltration membranes using additive of silica-PVP nanocomposite, Ind. Eng. Chem. Res., 49
(2010) 790-796.
[10] (a) J. Jiang, L. Zhu, L. Zhu, H. Zhang, B. Zhu, Y. Xu, Antifouling and antimicrobial polymer
membranes based on bioinspired polydopamine and strong hydrogen-bonded poly(N-vinyl
pyrrolidone), ACS Appl. Mater. Interfaces, 5 (2013) 12895-12904;
(b) H. Susanto, M. Ulbricht, Characteristics, performance and stability of polyethersulfone
ultrafiltration membranes prepared by phase separation method using different macromolecular
additives, J. Membr. Sci., 327 (2009) 125-135;
(c) H. Yu, Y. Cao, G. Kang, J. Liu, M. Li, Q. Yuan, Enhancing antifouling property of
polysulfone ultrafiltration membrane by grafting zwitterionic copolymer via UV-initiated
polymerization, J. Membr. Sci., 342 (2009) 6-13.
[11] (a) H. Dong, Y. Xu, Z. Yi, J. Shi, Modification of polysulfone membranes via surface-initiated
atom transfer radical polymerization, Appl. Surf. Sci., 255 (2009) 8860-8866;
(b) D. S. Wavhal, E. R. Fisher, Hydrophilic modification of polyethersulfone membranes by low
temperature plasma-induced graft polymerization, J. Membr. Sci., 209 (2002) 255-269.
[12] (a) D. Liu, D. Li, D. Du, X. Zhao, A. Qin, X. Li, C. He, Antifouling PVDF membrane with
hydrophilic surface of terry pile-like structure, J. Membr. Sci., 493 (2015) 243-251;
(b) M. K. Sinha, M. K. Purkait, Preparation of fouling resistant PSF flat sheet UF membrane
using amphiphilic polyurethane macromolecules, Desalination, 355 (2015) 155-168;
(c) Q. Shi, J. Meng, R. Xu, X. Du, Y. Zhang, Synthesis of hydrophilic polysulfone membranes
having antifouling and boron adsorption properties via blending with an amphiphilic graft
glycopolymer, J. Membr. Sci., 444 (2013) 50-59.
[13] (a) F. Gao, G. Zhang, Q. Zhang, X. Zhan, F. Chen, Improved antifouling properties of Poly(Ether
sulfone) membrane by incorporating the amphiphilic comb copolymer with mixed Poly(Ethylene
glycol) and Poly(Dimethylsiloxane) brushes. Ind. Eng. Chem. Res., 54 (2015) 8789-8800;
(b) Q. Liu, A. A. Patel, L. Liu, Superhydrophilic and underwater superoleophobic poly-
(sulfobetaine methacrylate)-Grafted glass fiber filters for oil−water separation. ACS Appl. Mater.
Interfaces, 6 (2014) 8996-9003;
(c) A. Venault, M. R. B. Ballad, Y. Liu, P. Aimar, Y. Chang, Hemocompatibility of PVDF/PS-b-
PEGMA membranes prepared by LIPS process, J. Membr. Sci., 477 (2015) 101-114.
[14] (a) R. F. M. Elshaarawy, A. A. Refaee, E. A. El-Sawi, Pharmacological performance of novel
23

ACCEPTED MANUSCRIPT
poly-(ionic liquid)-grafted chitosan-N-salicylidene Schiff bases and their complexes,
Carbohydrate polymers, 146 (2016) 376-387;
(b) H. K. No, N. Y. Park, S. H. Lee, S. P. Meyers, Antibacterial activity of chitosans and chitosan
oligomers with different molecular weights, Int. J. Food Microbiol., 74 (2002) 65-72;
(c) J. Rhoades, S. Roller, Antimicrobial actions of degraded and native chitosan against spoilage
organisms in laboratory media and foods, Appl. Envir. Microbio., 66 (1) (2000) 80-86;
(d) B. K. Choi, K. Y. Kim, Y. J. Yoo, S. J. Oh, J. H. Choi, C. Y. Kim, In vitro antimicrobial
activity of a chitooligosaccharide mixture against Actinobacillusactinomycetemcomitans and
Streptococcus mutans, Int. J. Antimicrob. Agents, 18 (6) (2001) 553-557.
[15] (a) R. F. M. Elshaarawy, F. H. A. Mustafa, A. Herbst, A. E. M. Farag, C. Janiak, Surface
functionalization of chitosan isolated from shrimp shells, using salicylaldehyde ionic liquids in
exploration for novel economic and ecofriendly antibiofoulants, RSC Adv., 6 (2016) 20901-
20915;
(b) I. L. Roux, H. M. Krieg, C. A. Yeates, J. C. Breytenbach, J. Membr. Sci., 248 (2005) 127-136.
,
E. Bagheripour, A. R. Moghadassi, S. M. Hosseini, B. Van der Bruggen, F. Parvizian, Novel
composite graphene oxide/chitosan nanoplates incorporated into PES based nanofiltration
membrane: Chromium removal and antifouling enhancement, J. Ind. Eng. Chem., 62 (2018) 311-
320.
[16] A. M. Motawie, K.F. Mahmoud, A. A. El-Sawy, H. M. Kamal, H. Hefni, H. A. Ibrahiem,
Preparation of chitosan from the shrimp shells and its application for pre-concentration of
uranium after cross-linking with epichlorohydrin, Egyptian J. Petroleum, 23 (2014) 221–228.
[17] Y. Mansourpanah, H. Soltani, K. Alizadeh, M. Tabatabaei, Enhancing the performance and
antifouling properties of nanoporous PES membranes using microwave-assisted grafting of
chitosan, Desalination, 322 (2013) 60–68.
[18] (a) S. Zinadini , A. A. Zinatizadeh, M. Rahimi, V. Vatanpour, H. Zangeneh, M. Beygzadeh,
Novel high flux antifouling nanofiltration membranes for dye removal containing carboxymethyl
chitosan coated Fe3O4 nanoparticles, Desalination, 349 (2014) 145–154;
(b) J. Miao, G. Chen, C. Gao, C. Lin, D.Wang, M. Sun, Preparation and characterization of N,O-
carboxymethyl chitosan (NOCC)/polysulfone (PS) composite nanofiltration membranes, J.
Membr. Sci., 280 (2006) 478-484;
(c) J. Miao, G. Chen, C. Gao, S. Dong, Preparation and characterization of N,O-carboxymethyl
chitosan/polysulfone composite nanofiltration membrane crosslinked with epichlorohydrin,
Desalination, 233 (2008) 147-156.
[19] (a) R. Kumar, A. M. Isloor, A. F. Ismail, T. Matsuura, Synthesis and characterization of novel
water soluble derivative of Chitosanas an additive for polysulfone ultrafiltration membrane, J.
Membr. Sci., 440 (2013) 140-147;
24

ACCEPTED MANUSCRIPT
(b) Y. Chen, Y. Zhang, H. Zhang, J. Liu, C. Song, Biofouling control of halloysite nanotubes-
decorated polyethersulfone ultrafiltration membrane modified with chitosan-silver nanoparticles,
Chem. Eng. J., 228 (2013) 12–20;
(c) M. K. Sinha, M. K. Purkait, Use of CS–PAA nanoparticles as an alternative to metal oxide
nanoparticles and their effect on fouling mitigation of a PSF ultrafiltration membrane, RSC Adv.,
5 (2015) 66109-66121.
[20] B. Yu, F. Zhou, H. Y Hu, C. W. Wang, W. M. Liu, Synthesis and properties of polymer brushes
bearing ionic liquid moieties, Electrochim Acta., 53 (2007) 487-494.
[21] Y. Ye, S. Sharick, Y. A. Elabd, Anion exchanged polymerized ionic liquids: high free volume
single ion conductors, Polymer, 52 (2011) 1309-1317.
[22] W. Qian, J. Texter, F. Yan, Chem. Soc. Rev., 46 (2017) 1124-1159.
[23] B. S. Lee, Y. S. Chi, J. K. Lee, Imidazolium ion terminated self-assembled monolayers on Au:
effects of counter anions on surface wettability, J Am Chem Soc., 126 (2004) 480-481.
[24] Q. Ye, T. Gao, F. Wan, Grafting poly(ionic liquid) brushes for antibacterial and anti-biofouling
applications, J Mater Chem., 22 (2012) 13123-13131.
[25] C. Du, X. Ma, C. Wu, Polymerizable ionic liquid copolymer P(MMA@co@BVIm@Br) and its
effect on the surface wettability of PVDF blend membranes, Chin J Polym Sci., 33 (2015) 857-
868.
[26] Y.-Y. Cheng, C.-H. Du, C.-J. Wu, K.-X. Sun, N.-P. Chi, Improving the hydrophilic and
antifouling properties of poly(vinyl chloride) membranes by atom transfer radical polymerization
grafting of poly(ionic liquid) brushes, Polym Adv Technol., 29 (2018) 623–631
[27] (a) A. Mollahosseini, A. Rahimpour, Interfacially polymerized thin film nanofiltration
membranes on TiO2 coated polysulfone substrate, J. Ind. Eng. Chem., 20 (5) (2014) 1261-1268;
(b) S. H. Kim, S.-Y. Kwak, B.-H. Sohn, T. H. Park, Design of TiO2 nanoparticle self-assembled
aromatic polyamide thin-film-composite (TFC) membrane as an approach to solve biofouling
problem, J. Membr. Sci., 211 (1) (2003) 157-165.
[28] S. Pourjafar, A. Rahimpour, M. Jahanshahi, Synthesis and characterization of PVA/PES thin film
composite nanofiltration membrane modified with TiO2 nanoparticles for better performance and
surface properties, J. Ind. Eng. Chem., 18(4) (2012) 1398-1405.
29 a) R. F. M. Elshaarawy, T. B. Mostafa, A. A. Refaee, E. A. El-Sawi, Ionic Sal-SG Schiff bases as
new synergetic chemotherapeutic candidates: synthesis, metalation with Pd(II) and in vitro
pharmacological evaluation, RSC Adv., 5 (2015) 68260-68269;
(b) R. F. M. Elshaarawy, H. R. Z. Tadros, R. M. Abd El-Aal, F. H. A. Mustafa, Y. A. Soliman,
M.A. Hamed, J. Environ. Chem. Eng., 4 (2016) 2754-2764;
(c) L. Carson, P. K. W. Chau, M. J. Earle, M. A. Gilea, B. F. Gilmore, S. P. Gorman, M. T.
McCann, K. R. Seddon, Green Chem., 11 (2009) 492-497.
25

ACCEPTED MANUSCRIPT
(d) R. F. M. Elshaarawy, I. M. Eldeen, E. M. Hassan, Efficient synthesis and evaluation of bis-
pyridinium/bis-quinolinium metallosalophens as antibiotic and antitumor candidates, J. Mol.
Struct.,1128 (2016) 162-173
[30] M. Padaki, A. M. Isloor, J. Fernandes, K. N. Prabhu, New polypropylene supported chitosan NF-
membrane for desalination application, Desalination, 280 (2011) 419-423.
[31] O. Iguerb, C. Poleunis, F. Mazéas, C. Compère, P. Bertrand, Antifouling Properties of
Poly(methyl methacrylate) Films Grafted with Poly(ethylene glycol) Monoacrylate Immersed in
Seawater, Langmuir, 24 (21) (2008) 12272-12281.
[32] L. Liu, D. Y. W. Di, H. Park, M. Son, H.-G. Hur, H. Choi, Improved antifouling performance of
polyethersulfone (PES) membrane via surface modification by CNTs bound polyelectrolyte
multilayers, RSC Adv., 5 (2015) 7340-7348.
[31] Y. S. Zhou, L. J. Zhang, X. R. Zeng, J. J. Vital, X. Z. You, A new structurally characterized
organotin/Schiff-base complex with approximately rectangular molecular boxes formed through
hydrogen bonds, J. Mol. Struct., 553 (2000) 25-30.
[34] J. G. Yu, J. J. Fan, K. L. Lv, Anatase TiO2 nanosheets with exposed (001) facets: improved
photoelectric conversion efficiency in dye-sensitized solar cells, Nanoscale, 2 (2010) 2144-2149.
[35] I.M. Wienk, R. M. Boom, M. A. M. Beerlage, Recent advances in the formation of phase
inversion membranes made from amorphous or semicrystalline polymers, J. Membr. Sci., 113
(1996) 361.
[36] (a) R. Taylor, R. Krishna, Multicomponent Mass Transfer Vol. 597, Wiley New York (1993);
(b) F. Zhang, W. Zhang, Y. Yu, B. Deng, J. Li, J. Jin, Sol-gel preparation of PAA-g-PVDF/TiO2
nanocomposite hollow fiber membranes with extremely high water flux and improved antifouling
property, J. Membr. Sci., 432 (2013) 25-32.
[37] T. Wang, Y. Wang, Y. Su, Z. Jiang, Antifouling ultrafiltration membrane composed of
polyethersulfone and sulfobetaine copolymer, J. Membr. Sci., 280 (2006) 343-350.
[38] H. Yu, Y. Cao, G. Kang, J. Liu, M. Li, Tethering methoxy polyethylene glycols to improve the
antifouling property of PSF/PAA-blended membranes, J. Appl. Polym. Sci., 124 (2012) E123–
E133.
26

ACCEPTED MANUSCRIPT
Graphical abstract
27

ACCEPTED MANUSCRIPT
Highlights
 A practical synthetic route of poly ionic liquid-chitosan Schiff bases (PILCSB) is reported.
 PILCSB was employed for surface modification of polysulfone to give mixed matrix membranes
(MMMs).
 Surface hydrophilicity of the MMMs was remarkably enhanced compared to the neat PSU
membrane.
 Pure water flux recovery ratio (FRR) experiment showed higher water permeability for MMMs.
 BSA filtration experiment demonstrates promoted and promising antifouling performance for
MMMs.
28