ArticlePDF Available

Fabrication of PES/PVP Water Filtration Membranes Using Cyrene®, a Safer Bio-Based Polar Aprotic Solvent


Abstract and Figures

A more sustainable dialysis and water filtration membrane has been developed, by using the new, safer, bio-based solvent Cyrene® in place of N-methyl pyrrolidinone (NMP). The effects of solvent choice, solvent evaporation time, the temperature of casting gel, and coagulation bath together with the additive concentration on porosity and pore size distribution were studied. The results, combined with infrared spectra, SEM images, porosity results, water contact angle (WCA), and water permeation, confirm that Cyrene® is better media to produce polyethersulfone (PES) membranes. New methods, Mercury Intrusion Porosimetry (MIP) and NMR-based pore structure model, were applied to estimate the porosity and pore size distribution of the new membranes produced for the first time with Cyrene® and PVP as additive. Hansen Solubility Parameters in Practice (HSPiP) was used to predict polymer-solvent interactions. The use of Cyrene® resulted in reduced polyvinylpyrrolidone (PVP) loading than required when using NMP and gave materials with larger pores and overall porosity. Two different conditions of casting gel were applied in this study: a hot (70°C) and cold gel (17°C) were cast to obtain membranes with different morphologies and water filtration behaviours.
This content is subject to copyright. Terms and conditions apply.
Research Article
Fabrication of PES/PVP Water Filtration Membranes Using
CyreneD, a Safer Bio-Based Polar Aprotic Solvent
Roxana A. Milescu,1C. Robert McElroy ,1Thomas J. Farmer ,1Paul M. Williams,2
Matthew J. Walters,2and James H. Clark 1
1Green Chemistry Centre of Excellence, Department of Chemistry, University of York, Heslington, York YO10 5DD, UK
2Department Chemical Engineering, Swansea University, Sketty, Swansea SA2 8PP, UK
Correspondence should be addressed to James H. Clark;
Received 13 March 2019; Revised 29 May 2019; Accepted 11 June 2019; Published 7 July 2019
Guest Editor: Zongli Xie
Copyright ©  Roxana A. Milescu et al. is is an open access article distributed under the Creative Commons Attribution
License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly
A more sustainable dialysis and water ltration membrane has been developed, by using the new, safer, bio-based solvent Cyrene
in place of N-methyl pyrrolidinone (NMP). e eects of solvent choice, solvent evaporation time, the temperature of casting gel,
and coagulation bath together with the additive concentration on porosity and pore size distribution were studied. e results,
combined with infrared spectra, SEM images, porosity results, water contact angle (WCA), and water permeation, conrm that
Cyreneis better media to produce polyethersulfone (PES) membranes. New methods, Mercury Intrusion Porosimetry (MIP) and
NMR-based pore structure model, were applied to estimate the porosity and pore size distribution of the new membranes produced
for the rst time with Cyreneand PVP as additive. Hansen Solubility Parameters in Practice (HSPiP) was used to predict polymer-
solvent interactions. e use of Cyreneresulted in reduced polyvinylpyrrolidone (PVP) loading than required when using NMP
and gave materials with larger pores and overall porosity. Two dierent conditions of casting gel were applied in this study: a hot
(C) and cold gel (C) were cast to obtain membranes with dierent morphologies and water ltration behaviours.
1. Introduction
e growing use of ltration membranes is the result of
increasing attention paid to environmental problems linked
to the availability of and growing demand for clean water
[–]. Recent work has highlighted the need for new sol-
vents in the membrane manufacturing process, in order
to minimise the problems of toxic solvent release to the
environment, with Polarclean,DMSOEvol, and ionic liq-
uids being successfully applied in this process [–]. Porous
polymeric membranes for water and wastewater treatment
have traditionally been produced from cellulose acetate [],
polysulfone [], polyvinylidene uoride (PVDF) [, ],
polyacrylonitrile (PAN) [], and polyvinyl alcohol (PVA)
[]. Polyethersulfone (PES) is used in separation due to its
excellent performance and high thermal, chemical, hydraulic,
and mechanical stability. e polymer generates membranes
ranging from nanoltration (NF) and Reverse Osmosis (RO)
used for desalinisation processes, to ultraltration (UF) used
for food, metal, and textile industry and microltration (MF)
for purication of beverages, and separation of oil and water
emulsions. Fouling of the membrane is as a result of the
hydrophobicity of PES, making separation unpredictable and
shortening its lifetime due to a higher energy demand to
push the water through the pores [, ]. To reduce the
fouling eect, the PES membranes are modied via bulk
modication, surface modication, and blending (a type of
surface modication), with the latter being the most widely
used method [].
Filtration membranes have previously been fabricated
using a casting solution of polyethersulfone (PES) in the
repro-toxic solvents NMP [–], DMF [], DMAc [],
or mixture of solvents [, ] along with a hydrophilic
homopolymer, such as polyvinylpyrrolidone (PVP) [, ]
or poly(ethylene glycol) (PEG) [, ], resulting in mem-
branes less prone to fouling [, ]. DMSO has been utilised
Advances in Polymer Technology
Volume 2019, Article ID 9692859, 15 pages
Advances in Polymer Technology
17.5 15
F : Recommended solvents mapped in Hansen space with solubility sphere for PES. Hansen solubility parameters are given here
in units of MPa1/2.
as the casting solvent [, , ], which is not in itself toxic, but
it acts as a permeability enhancer and transfer compounds
through the skin barrier. It is used in medicine as a skin
adsorption enhancer for dierent drugs [, ]. Recently
NMP was added to REACH’s restricted substances list [],
due to the reproductive eects of this solvent. NMP and
dichloromethane (DCM) were linked to foetal and adult
deaths and their use has been banned or limited from paint
stripping products by the big retailers. [] DMF and DMAc
are also on the Substances of Very High Concern (SVHC) list
as toxic for reproduction (may damage the unborn child). e
list of available and safe polar aprotic solvents is thus getting
e pore forming and structure controlling agents PVP
and PEG are incorporated into PES matrix, similar to other
polymer additives reported in the literature [, , ], so
as to increase the hydrophilicity, diusion properties (due to
pore size distribution on the membrane surface) antifouling,
and hemocompatibility properties of PES membranes [–
]. ese asymmetric membranes can be modied by
adjusting any of the following factors: the composition of the
casting solution (additives; solvent), the solvent evaporation
temperature/time, and the method utilised. In this study we
aim to substitute the traditional solvent used (NMP) with a
greener, safer alternative. Cyrene(dihydrolevoglucosenone)
is a new commercially available, nontoxic solvent obtained
from renewable waste and nonfood cellulosic source feed-
stock (e.g., straw, bagasse, and sawdust) (see Scheme ). It is
quickly proving to be a viable alternative polar aprotic solvent
to both NMP and DMF [–].
Cyreneis a polar aprotic solvent similar to NMP, but
renewable, biodegradable, and nontoxic []. Cyrenehas
been only given a hazard warning for being an eye irritant
(E) receiving an ECHA level  certication and has
recently received permission to be sold in large quantities
[, ]. Herein Cyrenehas been assessed for its suitability
in substituting for NMP in the fabrication of PES membranes.
2. Materials and Methods
2.1. Materials. e akes of UltrasonE P Polyar ylether-
sulfone (Figure ()) of , Da and a powder of PVP
LuvitekK- Pulver (Figure ()) with ,, Da were
obtained from INGE.BASF, Germany. e solvent Cyrene
was supplied by Circa Sustainable Chemicals Ltd., UK. All
the other solvents used in this study were of reagent grade
and purchased from Merck Co., UK, and VWR Chemicals ,
UK. Deionised water (DI) was provided in-house by the lab
using an ELGA CENTRAsystem. All chemicals were used
without any further purication.
2.2. HSPiP’s Predictive Power. Hansen Solubility Parameters
(HSP) [] were chosen to predict solubility of PES in
dierent solvents by mapping the three values (dispersion
interactions D, dipolarity P, and hydrogen bonding ability
H) in a three-dimensional ‘’Hansen space”, using 5th edition
.. of HSPiP (Hansen Solubility Parameters in Practice).
When determining whether a solvent will dissolve a
sphere, it is useful to calculate the relative energy dierence,
 = 
 ()
where Ro is the radius of interaction of a Hansen solubility
parameter sphere determined experimentally (Figure ) and
Ra is the solubility parameter distance between polymer and
solvent and can be calculated from
𝑠𝑜𝑙V𝑒𝑛𝑡 −
𝑠𝑜𝑙V𝑒𝑛𝑡 −
𝑠𝑜𝑙V𝑒𝑛𝑡 −
A D representation (Figure ) shows the distance of
the solvents which dissolved the polymer and PES. A
nonsolvent will have a Ra larger than the sphere’s Ro,making
Advances in Polymer Technology
cellulose levoglucosenone
Heat/ Pd
S : Scheme of Cyreneproduction from cellulose via levoglucosenone (LGO,).
F : Chemical structure of PES and PVP.
RED >, while solvents likely to aect the material will have
aRED<. A solvent with a RED < and closer to the
polymer’s centre (with D=., P=., and H=.) is
predicted a better solvent. Cyrenehas the smallest distance
from polymer in the Hansen space, suggesting the greatest
anity to PES (Table ). A full list of the solvents used
can be found in the Supplementary Material accompanying
the manuscript (SM Table ).
As seen in Table , comparing HSP of Cyreneand the
other polar aprotic solvents, it was found that Cyrenehas a
dispersion close to DMSO (. vs. .), a polarity parameter
close to NMP (. vs. .), and a hydrogen bonding close to
NMP (. vs. .). e similarity of Cyreneto the other polar
aprotic solvents has been studied previously [].
2.3. Membrane Synthesis
2.3.1. Preparation of Casting Solutions. In this study, the
polyethersulfone membranes (PES/C and PES/N) with highly
asymmetrical pore structure were fabricated from hot (C)
or NMP), using a nonsolvent phase inversion technique
Table  shows the formulations of PES ultraltration
at sheet membranes using two dierent solvents and with/
without PVP.
In this study, some of the characteristics of Cyrene
and NMP are presented in Table , showing the dierence
between the two solvents.
2.3.2. Membranes Fabrication. e casting solution was pre-
pared by dissolving  wt% of PES pellets (as compared to
the mass of solvent) into Cyreneor NMP at a temperature
of C for h. Dierent concentrations of PVP were added
under continuous stirring (Table ). e casting solution was
Polyester (PET) nonwoven fabric CraneMat CU (Neenah
Technical Materials, USA) for PES/C. e casting gel was
cast using a RK Print K bench casting machine (RK Print,
UK) at a speed of  cm s−1 for the membranes produced in
NMP and  cm s−1 for membranes produced in Cyrene.e
inuence over membrane ltration and a slower speed was
considered for PES/C due to its higher viscosity. e thickness
of all membranes was controlled at  m. e casting lm
was submerged in a coagulation bath containing deionised
water at RT, causing the PES to precipitate. Membranes were
then washed three times in distilled water for  minutes
while under sonication in order to wash out residual solvent
the fabricated membranes were then stored in deionised
water until further use. e membranes were prepared at RT
of C and a humidity of -%. e temperature of water
bath was C and the time from casting the gel to placing it
in a water bath was limited to a maximum of  seconds.
Due to the higher density of Cyreneand the amount
of PVP used, both of which add to the total viscosity of the
system; the gel was cast when hot. e viscosity of PES/C
was tested using a Brookeld R/S plus Rheometer and shows
a dramatic drop during the heating to C(SMFigure),
where its behaviour tends towards a Newtonian uid.
2.4. Membrane Characterisation. To characterise the pre-
pared membranes, they were rst washed with deionised
eects of the more viscous Cyreneon the pore size, porosity,
surface morphology, and mechanical properties of PES/PVP
membranes were studied by scanning electron microscopy
(SEM), pure water permeability, ATR-FTIR, and thermal
analyses. FTIR and TGA reected the physical or chemical
Advances in Polymer Technology
T : Hansen Solubility Parameters [MPa0.5] of dierent solvents and RED calculated for PES polymer.
Solvent DPHScoreRED
Cyrene. . . .
N-Methyl--Pyrrolidone  . . .
N,N-Dimethyl Acetamide . . . .
DimethylSulfoxide ...  .
Dimethyl Formamide . . . .
,-Dichloroethane . . .
T : Composition of casting solutions (g).
Membrane type Solution A Solution B
PES/ .% % .% .% % .%
PES/. .% .% .% .% .% .%
PES/. .% .% .% .% .% .%
PES/ .% .% .% .% .% .%
PES/ % % % % % %
PES/ .% .% .% .% .% .%
T : C y reneand NMP safety data sheet.
Solvent Empirical formula Molecular weight (g mol−1) Relative density (g mL−1 at C) B.P. (C) F.P. (C) M.P./F.P. (C)
CyreneC6H8O3. .   -.
NMP C5H9NO . .   -
changes on the surface or in the bulk of PES membranes aer
ATR-FTIR spectra were recorded on a PerkinElmer Spec-
tr um  FT-IR/ FT-NIR Spec trometer with transmittance
peaks in - cm−1 region, with rapid scanning ( scans)
and resolution  cm−1 at room temperature.
ermal stability of PES membranes was studied by TGA,
giving weight loss of the produced membranes as a function
of temperature. e membranes were heated from RT to
−1 under a ow of nitrogen.
Scanning Electron Microscopy (SEM) images were taken
on a JEOL JSM-LV, at kV from Bioscience Technology
Facility, Biology Department, University of York, and were
used to determine the morphology and structure of the
membranes aer they were frozen and fractured in liquid
nitrogen followed by Au/Pd coating.
Porosity and pore size distribution test were deter-
mined using Mercury Intrusion Porosimetry (MIP) using
a Micromeritics Autopore IV instrument located in the
University of Leeds. is method is based on the behaviour
of “nonwetting” liquids in capil lary which cannot be absorbed
by the pores of a solid itself, but requires an external pressure
to be applied. By measuring the volume of mercury that
intrudes into the sample material with each pressure change,
the volume of pores in the corresponding size class can be
obtained. MIP only shows accessible interconnected pores (if
the closed pores are incompressible). e applied mercury
pressure is inversely proportional to the size of the pores.
A lower pressure is needed to penetrate large pores, while
a greater pressure is needed to access smaller pores. From
the pressure versus intrusion data, the instrument generates
volume and size distributions using the Washburn equation:
=−4 cos
where Dstands for pore diameter (m), Pis the applied
pressure (psi), represents Hg-air surface tension ( mN
m−1), and is Hg-air-porous material contact angle ().
NMR spectroscopy was used as supporting evidence
of the pore size distributions and was considered a more
sustainable and less toxic method compared to the MIP
method, which can distort the skeletal porous structure of
a sample []. However, this method was used previously
to characterise porosity, pore geometry, connectivity, and
permeability of sandstones and carbonates [, ]. In this
project, the NMR was used to conrm the volume of uid
lling the pore space and a T distribution (equivalent to a
pore size distribution, PSD) is obtained aer deconvolution
of magnetization relaxation (Figure ).
As a measure of membrane’s hydrophilicity, the water
contact angle (WCA) was measured via the sessile drop
method [] using a eta Lite optical tensiometer at a room
temperature of C. A range of .–. Ldropletsizesof
water were placed on the membrane surface and the images
were recorded using the automated OneAttension soware.
e static contact angles were measured at a minimum of
three random locations and the mean values reported to
minimise experimental error.
Advances in Polymer Technology
0.001 0.01 0.1 1 10 100
Pore size distribution
Normalized signal
radius (microns)
Mercur y
F : MIP and NMR methods of porosity using a PES/C.
F : A schematic diagram of the frontal ltration equipment.
() Nitrogen cylinder, () valve, () pressure sensor, () water bath,
() membrane cell, () magnetic stirrer, () electronic balance, and
() PC.
2.5. Pure Water Permeability Test. Membrane permeability
was determined by measuring the pure water uxes using a
stirred cell (Sterlitech HP). e ltration solutions were
stirred magnetically at  rpm and a constant temperature
of ±.C. Rates of ltration were determined by continu-
ously weighing theltrate on an electronic balance connected
to a data logger. A digital electronic balance from Ohaus
(Scout Pro Range), with an accuracy of . g was used to
continuously measure the weight of the permeate. Recording
the weight at certain time intervals also allows the calculation
 = (+)−()
where 𝑤is the water ux (L m−2 h−1 (LMH)), mis the mass
at a given time, is the density of water, 𝑚is the area of the
membrane (m2), and tis the time (s).
Figure  shows schematically the arrangement of the
membrane ltration and ux measurement equipment. e
ltration cell was pressurised using nitrogen gas (oxygen
free) with pressure controlled by means of a regulator on the
cylinder. e  mm diameter membranes were rst subject
to an initial pressure of  bar until a stable ux was evident,
then the pressure increased to  and  bar.
2.6. Gravimetric Method of Water Adsorption. is method
is repeatedly used in literature to evaluate the porosity of
the membranes[, ] via determining take up of water.
e membranes were vacuum dried at C, before being
weighed and their size and thickness measured. ey were
then immersed in distilled water at RT for h, before being
weighed again, and the increase in mass registered. e
%water retained in pores was calculated using the following
=Ww Wd
Axlxx100 ()
where Ww and Wd represent wet and dry masses (g) of the
membranes, respectively, Aisthemembranesurfacearea
(m2), lis thickness of membrane (m), and is density of water
at RT ( Kg m−3).
3. Results and Discussion
3.1. Porosity and Pore Size Distribution. e membranes are
coded based on the solvent used (PES/C is the membrane
produced with Cyrenewhile PES/N represents the one with
NMP) and the concentration of PVP used, e.g., “” means
a membrane produced with no PVP, while “.” through to
‘’” means a membrane produced with .% through to %
PVP, respectively (Table ). For example, a PES membrane
produced with Cyreneand .% PVP will be referred to
as “PES/C.” while the same membrane produced in NMP
would be denoted “PES/N.”.
As seen in Figure , the Cyrene-based membranes pre-
sented higher porosity in comparison to NMP in all cases,
with a maximum of %and .% for PES/C. and PES/C,
respectively. e membrane prepared with Cyrene developed
porosity even when not using pore forming PVP (PES/CO
with .% total porosity), which demonstrates superior
porosity than a NMP-based membrane using pore forming
additive (PES/N.) with .% porosity. e membrane
with % PVP has the lowest total porosity (.%), and
at this point the membrane exhibits a dierent morphology
(phenomenon seen in SEM images). On the other hand, the
Advances in Polymer Technology
0 0.1 0.5 1 5 10
Porosity (%)
PVP (%)
F : Overall porosity of the PES membranes prepared with Cyrene(blue) and NMP (orange).
0 0.1 0.5 1 5 10
Pore diameter (m)
PVP (%)
F : Overall pore diameters (m) of PES/C (blue) and PES/N (orange).
highest porosity (.%), for the membranes produced with
NMP is obtained with a PVP concentration of .%. e
lowest porosity for the membranes produced using NMP
occurs for PES/N (.%).
It is also signicant that .% PVP is enough to produce
good quality PES/C membranes, lowering the amount of sac-
ricial polymer represents an important starting point for the
sustainable membrane fabrication together with substitution
of a toxic petroleum-derived solvent with a safe, bio-based
Both Cyrene- and NMP-based membranes present a
slightly decreasing porosity when .% PVP is used (PES/
C. and PES/N.) and clearly decrease when using a
higher concentration of PVP (PES/C and PES/N). is
decrease in porosity is more visible in the case of NMP-based
membranes. However, this means that % of additive is clearly
sucient to give the maximum porosity in both types of
membranes, with Cyrene-based membranes more superior
than the NMP equivalents.
Figure  shows the pore diameter of membranes pro-
duced with Cyreneand NMP. PES/C membranes developed
bigger pores than PES/N, except for PES/C, which has a
dierent morphology. Interestingly, the pore size of a Cyrene-
based membrane with no additive (PES/C) has a similar
pore diameter to that obtained in NMP-based membrane
using at % PVP (PES/N). is means that no additive
is necessary to form pores when using Cyreneas solvent.
Similarly a membrane produced using Cyreneand % PVP
(PES/C) shows the same pore diameter as a NMP-based
membrane when using % (PES/N) of the same pore
forming agent. at means that less sacricial pore forming
agent is required when using Cyreneas solvent compared to
NMP-based systems.
Membranes prepared with Cyrenehave pore diameters
from . m(PES/C)tom(PES/CandPES/C),while
the membranes prepared with NMP range between . m
(PES/N, ., ., m) to m(PES/N).Figureclearly
shows similarity between PES/C and PES/C to PES/N in
pore size and pore distribution (SM Figure  and SM Figure
). e membranes made using Cyreneneed % PVP to
develop the biggest pores (PES/C), while the membranes
produced with NMP need twice as much PVP to develop the
same pore diameter.
A high degree of variation in the pore system is seen
when PVP concentration is increased. is is observed
by the greater decrease in total porosity and an increase
of pore diameters in the range between . and mfor
PES/C-, followed by a dramatic decrease of pore diameter
for PES/C. e Cyrene-based membranes pore diameters
follow a trend from a minimum with PES/C to a maximum
Advances in Polymer Technology
with PES/C. Above a % PVP loading, this type of mem-
branes drops drastically in pore diameter. is is as a result
of the morphology of the membrane changing signicantly,
with large cavities containing very small pores on the walls
(as clearly seen in Figure ).
is morphology is clearly seen in PES/C where a
‘diusion membrane’ has been formed, at which point it
is believed that the pores of . m are incorporated in
the walls of cavities, replacing the classical macrovoids. e
asymmetric membranes have variable pore diameters, from
. to  m while the symmetric one (PES/C) present
more uniform pores, with majority of pores of  mdiameter.
PES/C presents a small quantity of pores of . m; the
quantity of this type of pores increases with increasing of
PVP in casting solution and their presence is exclusively in
Membranes made using NMP increase their pore diam-
eters with increasing PVP concentration from PES/N-.
e NMP-based membranes present the same small pore
diameter until a concentration of % of pore forming additive
is added to the casting gel, leading to a bigger pore diameter
with a maximum for PES/N.
e results from NMR spectroscopy are consistent with
the previously reported MICP results. e largest pores
(around  m) can be seen in the membranes produced with
Cyrene, increasing in line with the concentration of PVP
used, with a maximum in PES/C. For PES/N the number
of larger pores increases with increasing PVP concentration,
while smaller pores are no longer seen (e.g., pores in the
range . to . microns are only observed for PES/N.).
Aer deconvolution of magnetization relaxation of Nuclear
Magnetic Resonance (see Figure ), the obtained T curves
conrm the volume of uid lling the pore space and
indirectly the pore size distribution, described above by
MICP method.
3.2. Membrane Characterisation
3.2.1. Membrane Functional Groups via FTIR Spectroscopy.
e membranes present functional groups specic to PES,
S=O symmetric stretch at  cm−1,C-SO
2-C asymmetric
stretch at  cm−1, C-O asymmetric stretch at  cm−1,
C6H6ring stretch at  and  cm−1,C-Hstretchat
- cm−1, in addition to the residual PVP as indicated
by a C=O stretch at - cm−1, pyrrolidinyl radical at
 and  cm−1,C-Nvibrationatcm
asymmetric stretch at  cm−1.
During the membrane precipitation step, some of the PES
the water-soluble polymer, but enough PVP remains (with its
presence at  cm−1 in Figure ), providing the polymer
surface with a more hydrophilic nature than the surface of
PES alone.
InthecaseofPES/Cyrene, coloration due to release of
PES into the gelation media was les s apparent than in the PES/
NMP systems. is indicates a stronger PES/PVP interaction
in Cyrene(SM Figure ).
3.2.2. Scanning Electron Microscopy (SEM) Analysis. All
membranes produced herein (except for PES/C) present a
typical structure with a thin top layer supported on a sponge-
like substructure (important for the mechanical resistance of
the membranes), and macrovoids, due to the instantaneous
demixing during the phase inversion [], where PVP behaves
as an antisolvent agent in the demixing step due to its high
solubility in water. e casting solution has a high anity for
water which can cause changes in morphology and perfor-
mance []. In this study the gel was cast and the glass plate
with the casting gel was quickly immersed in the coagulation
bath meaning the exposure to the atmosphere was less than
 seconds. Finger-like structures can be seen near the inner
(connecting the top layer to the sponge-like structure) and
outer surface, while sponge structure can be seen in the
centre of membranes. It has been generally accepted that
instantaneous demixing leads to macrovoid structure and
delayed demixing leads to a sponge-like structure [, ].
While the sponge-like structure looks the same in both
Cyreneand NMP producing membranes, Figure  shows
the dierence between them in a macrovoid layer at the same
When pure PES is used, the phase separation of polymer
solution occurs immediately, due to low viscosity of the
casting gel. e higher viscosity of Cyrene(. m Pa s
at C) compared to NMP (. m Pa s at C) adds
to the casting gel’s viscosity leading to a slower demixing
process and hence to a more visible sponge-like structure
(Figure ). e modication of polymer solution (by adding
PVP) changes the pore structure of the membrane []. Also,
dierent temperatures of the casting gel lead to dierences in
their morphology (Figure ):
e membranes cast from the cold gels present more
nger-like layers than the plain PES/C (which is more
viscous), especially in the middle of the membrane. e
membranes cast from Cyrenehot gels showed more sponge-
like structure, with macrovoids all the way through the
membrane. A greater dierence in morphology starts from a
concentration of % PVP, with the greatest at a concentration
of % PVP. PES/C from a hot gel (Figure (l)) developed
a completely dierent surface morphology, a symmetrical-
like structure, looking like a porous web or sponge. is
could be caused by the large amount of PVP which slowed
precipitation. When cast from a cold gel, the membrane
shows asymmetrical layers with bigger space (Figure (i)).
Increasing the PVP content in the casting solution led to
slower demixing, especially towards the bottom layer of
membrane (closest to the glass slide). When the exchange
from solvent to antisolvent occurs, it starts at the surface,
where nger voids are observed and slows as it approaches
the bottom layer, when more sponge-like structures are seen.
is structure presents pores which increase in diameter
from the top to the bottom surface of the membrane. e
rheology of the casting gel of PES/C was studied, with
a decrease in viscosity with increasing temperature clearly
visible (SM Figure ). is had a great impact on the
membrane morphology and dierences in the permeability
data are expected. A clear dierence between the membranes
cast from hot/cold gels is seen in NMP’s case too (red circle
Advances in Polymer Technology
Normalized signal
radius (microns)
Normalized signal
radius (microns)
F : Pore size distribution of PES produced with Cyrene(a) and NMP (b) using NMR.
Wave Number (c-1)
F : Fourier transform infrared spectrum of PES/C.
in SM Figure ) where the one cast from a hot gel presents a
shows the nger layer all the way through the membrane.
3.2.3. ermal Stability of Membranes. e results of ther-
mogravimetric analysis on the membranes prepared here are
shown in Figure  and Table . PVP has a decomposition
temperature around C, while PES decomposes at
-C, which means that PVP would lose more weight
before PES began to decompose.
e rst degradation took place below Cdueto
moisture loss, followed by Cyrenevolatilisation at around
C for NMP, followed by PVP decomposition
at ca. C and PES decomposition at ca. -C. e
dierential thermogravimetric data shows a greater amount
of residual PVP from PES/C membranes.
PES/C membranes consistently show a higher thermal
stability than PES/N equivalents. PES/C has a thermal
decomposition of .C, while PES/N decomposes at
.C, which means that a greater energy is required to
break the bonds of PES/C membrane. e peak of the 1st
derivative (inection point) indicates the point of greatest
rate of change on the weight loss curve, as seen in Figures
(b) and (d).
e addition of PVP to the membranes decreases the
thermal stability, due to a lower decomposition temperature
of PVP than of PES, but the miscibility of both polymers
was conrmed from the thermal analysis. e dierences
between the concentration of PVP and TGA residue may
be due to PVP remaining in the membranes aer washing
with water, depending on the membranes porosity and pore
membranes lost more PES and PVP than PES/C, which
means that Cyrenemakes a better media for this type of
3.3. Surface Wetting Property of the New Membranes Produced
with Cyrene.AsshowninFigure(a),thestaticwater
contact angle of the new PES lms produced with Cyrene
decreased from .% for PES/C to .% for PES/C, with
a hydrophilic character in all cases. is decreasing of the
contact angle indicates increasing in hydrophilicity of these
membranes with increasing residual PVP content.
e wetting changes were recorded over time by means
of the same methodology used for static contact angle, but
with values taken over a  second range. It can be seen
in Figure (b) how the droplets change in a reproducible
Advances in Polymer Technology
(a) (b)
F : SEM images of PES/C. (a) and PES/N. (b) in detail.
T : ermogravimetric (TGA) analysis measurements of PES/C and PES/N membranes.
C/Sample Residue% Tm (C) N/Sample Residue Tm (C)
PES  .
PVP K . .
PES/C . . PES/N . .
PES/C. . . PES/N. . .
PES/C. . . PES/N. . .
PES/C . . PES/N . .
PES/C . . PES/N . .
PES/C . . PES/N . .
manner and reduce their contact angle. A larger initial drop
occurs as water rapidly lls pores at the surface of the
membrane, until locally saturated. is phenomenon was
found to be due to a result of the advancing angle (higher
changing into a receding angle (low contact angle of the
hydrophilic component) upon a decrease in droplet volume
and is due to imbibition and evaporation. []
e contact angle of PES/C recorded the smallest change
during the test time, due to a less hydrophilic character
and the tendency of the droplet to be repulsed by the
membrane surface at least at the beginning. Over the time,
when the membrane is locally saturated, the droplet moves
into the porous membrane and the contact angle changes.
On the other side, PES/C membrane was found to have the
most dramatic change in its contact angle, due to the most
hydrophilic character and its porosity. e SEM images of
the PES/C demonstrated a very porous membrane which
would allow the droplet of water to be completely absorbed
in under  seconds during the WCA experiment.
3.4. Pure Water Permeability. Pure water permeability (PWP)
testing was evaluated based on water ux. Evidence in the
literature indicates that the sponge layer lters are slower than
the nger layer of a membrane [].
Based on these criteria, the permeate ux seen in Figure 
shows dierences between the membranes depending on the
solvent used, the concentration of PVP used, and temperature
of the casting gel. e membranes produced using Cyrene
and cast from a cold gel show an increasing permeability
when PVP is added with a maximum at % PVP, but with
no permeability when using ., , and % PVP. is is
explained by the morphology of the membrane, with more
nger layers on top of the membrane a dense sponge layer
at the bottom of the membrane. is is due to the thickness
of membrane chosen in this project ( m) which results
in dierent morphologies most likely depending on speed of
exchange between the solvent and water (SM Figure ). At
the top surface, this is rapid, with the polymer precipitating
out and voids forming as a result of water displacement. At
the bottom, crystallisation has dominated, with fewer voids.
is results in low permeability as the nger regions are
not interconnected. e concentration of PVP used had a
great impact of permeability when using over .% PVP,
when the produced membranes showed no ux, due to the
presence of dead ends of the nger layers presented in their
morphologies. e new membranes PES/C and PES/C.
cast from cold gels together with PES/C from a hot gel
are believed to be suitable for a ultraltration (UF), while
a permeability is lower than  LMH/bar for a nanoltra-
tion/reverse osmosis (NF/RO), while the PES/C membrane
showed greater uxes more in keeping of a microltration
membrane (MF). Instead, when the same membranes are
cast from a hot gel, the produced membranes showed a
permeability with a maximum at % PVP, but with a smaller
permeate ux than the corresponding cold gel membrane.
e membranes produced from a cold gel, using Cyreneand
a PVP concentration above .%, developed a morphology
 Advances in Polymer Technology
(a) (b) (c)
(d) (e) (f)
(g) (h) (i)
(j) (k) (l)
F : SEM cross-section of membranes produced from Cyrene and dierent concentrations of PVP: % (a, d), .% (b, e), .% (c, f),
% (g, j), % (h, k), and % (i, l) in cold (rst letter)and hot gels (second letter).
Advances in Polymer Technology 
0% PVP
0.1% PVP
0.5% PVP
1% PVP
5% PVP
10% PVP
Temp (C)
WtPercent (%)
0% PVP
0.1% PVP
0.5% PVP
1% PVP
5% PVP
10% PVP
PES 3020
Temp (C)
Derivative weight (%/C)
0% PVP
0.1% PVP
0.5% PVP
1% PVP
5% PVP
10% PVP
Temp (C)
WtPercent (%)
0% PVP
0.1% PVP
0.5% PVP
1% PVP
5% PVP
10% PVP
PES 3020
Temp (C)
Derivative weight (%/C)
F : TGA and DTG spectra of PES/C (a-b) and PES/N membranes (c-d). Note: TGA, thermogravimetric analysis; DTG, dierential
with nger layers in the middle of the membrane but are not
interconnected to the surface, thus registering no permeate
When adding PVP, the permeability also increased in
PES/N, with a maximum ux at % PVP and when the
membrane was cast from a cold gel. When cast from a hot
gel, the membrane produced from the same concentration of
PVP showed a higher ux of water due to a void in the middle
of the membrane which permitted a higher permeability.
Looking at Figures SM (b) and (e) relating to .N, the
hot cast seems to have a layer in which all the pores appear
blocked about 1/2 waythroughthemembrane(redcirclein
SM Figure (e)). However, in the cold cast, the pores appear
to traverse the membrane (red circle in SM Figure (b)). e
presence of the middle sponge layer in PES/N membranes
which were hot cast showed a lower permeability than the
ones coming from a cold gel, except for PES/N., where
the morphology shows a thicker sponge layer, which would
generally slow the ux down.
3.5. Gravimetric Analysis. Figure  shows the absorption
capacity of PES/C (in blue) and PES/N (in orange) to retain
pure water in their pores. Although less precise than other
methodologies applied in this research, this is the standard
test to evaluate membrane porosity [].
Figure  shows that PES/C consistently developed a
greater water retention capacity than the respective PES/N
membrane (consistent with MICP and SEM data). MICP
and gravimetric data present dierences between the samples
generated using the same solvent. For example, gravimetri-
cally PES/C presents the biggest capacity of water absorp-
tion, while for MICP data, PES/C. has the biggest total
 Advances in Polymer Technology
0 60 120 180 240 300
F : e static water contact angle (a) and the time-depended values (b) for a sessile drop spreading over a range of PES membranes
produced with Cyrene.
90.2 124.7 000
15 187.2 10.3 140.5
720.3 656.3
Average permeability (LMH/bar)
Membrane name
2.4 4.5 2.3 23.2
65.5 3.5
103.5 157.2 210.6
Average permeability (LMH/bar)
Membrane name
F : Pure water permeability of membranes cast from cold (in blue) and hot (in red) gel.
porosity. However, PES/C showed the smallest capacity to
retain water, which is entirely consistent with MICP and SEM
4. Conclusions
Polyethersulfone at sheet membranes for water ltration
applications were prepared by the NIPS technique employing
Cyreneas an alternative solvent and compared to PES
produced using the traditional NMP. Membrane morphol-
ogy and performance were tailored acting on the casting
solution composition and temperature. e new membranes
produced with Cyreneare more sustainable, with less
of both polymers’ loss and tunable pore size and contact
angles, from a less hydrophilic PES/C to a more hydrophilic
PES/C when the hydrophilic additive is added to the
Advances in Polymer Technology 
0 0.1 0.5 1 5 10
Water adsorption capacity (%)
PVP (%)
F : Gravimetric analysis of PES/C and PES/N.
casting solution. e produced membranes with the bio-
based solvent Cyreneshowed a greater total porosity, bigger
pore size, and higher thermal stability, compared to the
PES membranes produced with NMP. It was found that
no additive is necessary to form pores when Cyreneis
applied as solvent, PES/C having the same pore diameter as
NMP-based membranes produced with % PVP (PES/N),
meaning that no additive many not be necessary for the
role of pore forming when using Cyrene.PESmembranes
produced with Cyreneand .% PVP (PES/C.) and %
PVP (PES/C) developed the largest porosity (ca. %) for the
both Cyreneand NMP-based membranes. PES produced
with Cyreneand minimal concentration of PVP (.%
PVP) developed the same pore diameter as PES produced
with NMP at a higher concentration of PVP (%) and the
largest pores are registered in PES when using Cyrenewith
largest pore diameter appears using a higher concentration
of PVP (%). e permeability of the new membranes
produced with Cyrenewas easily tailored in the range
between NF/RO to MF, by changing the temperature of the
casting gel, whereas only slightly small changes were observed
when using NMP. While the PES/N showed a trend with a
maximum ltration for PES/N cast from a cold gel when
% PVP was used, the same membranes cast from a hot
gel showed no supporting trend, probably because NMP
evaporated quicker than Cyrene at elevated temperatures.
Completely new morphologies were found in PES produced
in Cyrene, when using % PVP, regardless if cast hot or
cold. When using Cyrene, the morphology was dierent for
the two casting gels, with a symmetrical one observed when
hot cast; this is less obvious when cast from a cold gel. Both
hot and a cold cast PES/C have showed the best ltrate ux,
with the potential, for application in microltration. Utilising
cold casting, minimal addition of PVP leads to better ltra-
tion properties than the corresponding membrane produced
without any additive; this suggests PES/C. has applications
as a hydrophilic, highly biocompatible/haemodialysis ultra-
ltration membrane. e relatively high viscosity of Cyrene
adds to the overall viscosity of the PES/PVP casting gel and
this can be exploited to tailor membranes to dierent ranges
of ltration with dierent physical properties. Decreasing
viscosity with temperature is a potential factor to consider
when casting membranes containing Cyrene.
Data Availability
Data supporting this publication is available in the supporting
information while additional raw data is available via https://./cfa-caa--ad-fefcf.
Conflicts of Interest
e authors declare that they have no conicts of interest.
We extend our thanks to INGE.BASF for providing PES and
PVP polymers used in this project, Meg Stark from Bio-
science Technology Facility, Biology Department, University
of York for SEM images, and Dr Carlos Grattoni from School
of Earth and Environment, Leeds University for mercury
porosimetry and low-eld NMR spectroscopy. e authors
would like to acknowledge Circa Sustainable Chemicals Ltd.
for its nancial support of this work.
Supplementary Materials
Supplementary information is available and contains a table
listing all the solvents studied via HSPiP (SM Table ); a
plot for the temperature dependent viscosity of the PES/C
sample over the range of room temperature to C(SM
Figure ); MICP pore diameter distributions for each sample
prepared in Cyrene(SM Figure ) or NMP (SM Figure
); a photograph showing the coagulation bath of PES/PVP
membranes in Cyreneand NMP (SM Figure ); SME cross-
section images of each membrane prepared in NMP (SM
Figure ); SEM cross-section images of PES/C at dierent
thickness (SM Figure ). (Supplementary Materials)
 Advances in Polymer Technology
[] S. Al Aani, C. J. Wright, and N. Hilal, “Investigation of UF
membranes fouling and potentials as pre-treatment step in
desalination and surface water applications,Desalination,vol.
, pp. –, .
[] Y. L. uyavan, N. Anantharaman, G. Arthanareeswaran, and
A. F. Ismail, “Impact of solvents and process conditions on
the formation of polyethersulfone membranes and its fouling
behavior in lake water ltration,JournalofChemicalTechnology
and Biotechnology,vol.,no.,pp.,.
[] M. Omidvar, M. Soltanieh, S. M. Mousavi, E. Saljoughi, A.
Moarean, and H. Saaran, “Preparation of hydrophilic nano-
ltration membranes for removal of pharmaceuticals from
water,Journal of Environmental Health Science and Engineering,
vol. , no. , .
[] T. Marino, E. Blasi, S. Tornaghi, E. Di Nicol`o, and A. Figoli,
“Polyethersulfone membranes prepared with RhodiasolvPo-
larclean as water soluble green solvent,Journal of Membrane
Science, vol. , pp. –, .
[] D.S.Lakshmi,T.Cundari,E.Furiaetal.,“PreparationofPoly-
meric Membranes and Microcapsules Using an Ionic Liquid as
Morphology Control Additive,Macromolecular Symposia,vol.
, no. , pp. –, .
[] D. Kim, O. R. Salazar, and S. P. Nunes, “Membrane manufacture
for peptide separation,” Green Chemistry,vol.,no.,pp.
, .
[]D.Kim,H.Vovusha,U.Schwingenschl¨ogl, and S. P. Nunes,
“Polyethersulfone at sheet and hollow ber membranes from
solutions in i onic liquids,” Journal of Membrane Science,vol.,
pp. –, .
[] T. Marino, F. Galiano, S. Simone, and A. Figoli, “DMSO EVOL
as novel non-toxic solvent for polyethersulfone membrane
preparation,” Environmental Science and Pollution Research,vol.
, no. , pp. –, .
[] M. Elimelech, . Xiaohua Zhu,A. E. Childress, and . Seungkwan
Hong, “Role of membrane surface morphology in colloidal
fouling of cellulose acetate and composite aromatic polyamide
reverse osmosis membranes,Journal of Membrane Science,vol.
, no. , pp. –, .
[] K. Kim, K. Lee, K. Cho, and C. Park, “Surface modication of
polysulfone ultraltration membrane by oxygen plasma treat-
ment,Journal of Membrane Science,vol.,no.-,pp.
, .
[] Z.Wang,H.Yu,J.Xiaetal.,“NovelGO-blendedPVDFultra-
ltration membranes,Desalination,vol.,pp.,.
[] S. Ayyaru and Y. Ahn, “Application of sulfonic acid group func-
tionalized graphene oxide to improve hydrophilicity, perme-
ability, and antifouling of PVDF nanocomposite ultraltration
membranes,Journal of Membrane Science,vol.,pp.,
[] I. Sentana, M. De La Rubia, M. Rodr´ıguez, E. Sentana, and
D. Prats, “Removal of natural organic matter by cationic and
anionic polyacrylonitrile membranes. e eect of pressure,
ionic strength and pH, Separation and Purication Technology,
polyvinyl alcohol membrane,Materials Letters,vol.,no.,
pp. –, .
[] M. KOH, M. CLARK, and K. HOWE, “Filtration of lake
natural organic matter: Adsorption capacity of a polypropylene
microlter,Journal of Membrane Science,.
[] X. Ma, Y. Su, Q. Sun, Y. Wang, and Z. Jiang, “Enhancing the
antifouling property of polyethersulfone ultraltration mem-
branes through surface adsorption-crosslinking of poly(vinyl
alcohol),Journal of Membrane Science,vol.,no.-,pp.
, .
[] C.Zhao,J.Xue,F.Ran,andS.Sun,“Modicationofpolyether-
sulfone membranes—a review of methods, Progress in Materi-
als Science,vol.,no.,pp.,.
[] N.Maximous,G.Nakhla,andW.Wan,“Preparation,charac-
terization and performance of Al2O3/PES membrane for waste-
water ltration,Journal of Membrane Science,vol.,no.,pp.
–, .
[] R.Boom,T.vandenBoomgaard,andC.Smolders,“Masstrans-
fer and thermodynamics during immersion precipitation for
a two-polymer system,” Journal of Membrane Science,vol.,
no. , pp. –, .
[] J.-H. Kim and K.-H. Lee, “Eect of PEG additive on membrane
formation by phase inversion,Journal of Membrane Science,
vol. , no. , pp. –, .
“Improving permeability and ant ifouling performance of polye-
thersulfone ultraltration membrane by incorporation of ZnO-
DMF dispersion containing nano-ZnO and polyvinylpyrroli-
done,Journal of Membrane Science,vol.,pp.,.
[] M. Khorsand-Ghayeni, J. Barzin, M. Zandi, and M. Kowsari,
“Fabrication of asymmetric and symmetric membranes based
on PES/PEG/DMAc,Polymer Bulletin,vol.,no.,pp.
, .
[] K. Yoon, B. S. Hsiao, and B. Chu, “Formation of functional
polyethersulfone electrospun membrane for water purication
by mixed s olvent and oxidati on processes,” Polymer Journal,vol.
, no. , pp. –, .
[] A. Rahimpour and S. Madaeni, “Polyethersulfone (PES)/cellu-
lose acetate phthalate (CAP) blend ultraltration membranes:
Preparation, morphology, performance and antifouling proper-
ties,Journal of Membrane Science,vol.,no.-,pp.,
[] A. Idris, N. Mat Zain, and M. Noordin, “Synthesis, characteri-
zation and performance of asymmetric polyethersulfone (PES)
ultraltration membranes with polyethylene glycol of dierent
molecular weights as additives, Desalination,vol.,no.-,
pp. –, .
[] B. Chakrabarty, A. K. Ghoshal, and M. K. Purkait, “Eect
of molecular weight of PEG on membrane morphology and
transport proper ties,Journal of Membrane Science,vol.,no.
-, pp. –, .
[] H. Qin, S. Nie, C. Cheng et al., “Insights into the surface prop-
erty and blood compatibility of polyethersulfone/polyvinyl-
pyrrolidone composite membranes: toward high-performance
hemodialyzer,” Polymers for Advanced Technologies,vol.,no.
, pp. –, .
[] I.Sadeghi,A.Aroujalian,A.Raisi,B.Dabir,andM.Fathizadeh,
“Surface modication of polyethersulfone ultraltration mem-
branes by corona air plasma for separation of oil/water emul-
sions,Journal of Membrane Science,vol.,pp.,.
[] G. Arthanareeswaran and V. M. Starov, “Eect of solvents
on performance of polyethersulfone ultraltration membranes:
Investigation of metal ion separations,Desalination,vol.,
no. , pp. –, .
[] P. Karande and S. Mitragotri, “Enhancement of transdermal
drug delivery via synergistic action of chemicals,Biochimica
Advances in Polymer Technology 
et Biophysica Acta (BBA) - Biomembranes,vol.,no.,pp.
–, .
[] H. Marwah, T. Garg, A. K. Goyal, and G. Rath, “Permeation
enhancer strategies in transdermal drug delivery,Drug Deliv-
[] “-methyl--pyrrolidone - Substances restricted under REACH
- ECHA, (n.d.),”
under-reach/-/dislist/details/beff, .
[] “ - Doc ket Folder Summary, (n.d.),” https://www-, .
[] R.Boom,I.Wienk,T.vandenBoomgaard, andC.Smolders,
“Microstructures in phase inversion membranes. Part . e
role of a polymeric additive,Journal of Membrane Science,vol.
hury, G. Pleizier, and J. Santerre, “Inuence of processing
conditions on the properties of ultraltration membranes,
Journalof MembraneScience,vol.,no.-,pp.,.
[] F. Ran, S. Nie, Z. Yin et al., “Synthesized negatively charged
macromolecules (NCMs) for the surface modication of anti-
coagulant membrane biomaterials,” International Journal of
Biological Macromolecules, vol. , pp. –, .
[] S. Zinadini, A. A. Zinatizadeh, M. Rahimi, V. Vatanpour, and
H. Zangeneh, “Preparation of a novel antifouling mixed matrix
PES membrane by embedding graphene oxide nanoplates,”
Journal of Membrane Science, vol. , pp. –, .
[] Z.Yi,L.Zhu,Y.Xu,Y.Zhao,X.Ma,andB.Zhu,“Polysulfone-
based amphiphilic polymer for hydrophilicity and fouling-
resistant modication of polyethersulfone membranes,” Journal
of Membrane Science,vol.,no.-,pp.,.
[] D. E. Richardson and W. D. Raverty, “Predicted environmental
eects from liquid emissions in the manufacture of levoglu-
cosenone and Cyrene TM,Appita Journal,vol.,no.,pp.
–, .
levoglucosenone (Cyrene) as a bio-based alternative for dipolar
aprotic solvents,” Chem. Commun.,vol.,no.,pp.
, .
[] H. J. Salavagione, J. Sherwood, M. De bruyn et al., “Identica-
tion of hig h performance solvents for the su stainable processing
of graphene,Green Chemistry,vol.,no.,pp.,
[] J. Zhang, G. B. White, M. D. Ryan, A. J. Hunt, and M. J. Katz,
“ Dihydrolevoglucosenone (Cyrene) As a Green Alternative to
N,N -Dimethylformamide (DMF) in MOF Synthesis , ACS
Sustainable Chemistry & Engineering,vol.,no.,pp.
, .
[] L.Mistry,K.Mapesa,T.W.Bouseld,andJ.E.Camp,“Synthesis
of ureas in t he bio-alternative s olvent Cyrene,Green Chemistry,
vol. , no. , pp. –, .
[] “(S,R)-,-dioxabicyclo[..]octan--one - Substance Infor-
mati on - ECHA,” -information/
[] “Press Release: Circa Receives Green Light to Sell Non-toxic,
Bio-bas ed and Biodegradable Solve nt in EU, ( n.d.),” https://www-press-release-circa-receives-
vent-in-eu, .
[] C. M. Hansen, “e Universality of the Solubility Parameter,”
Industrial & Eng ineering Chemistry Product Rese arch and Devel-
of NMR Cryoporometry, Mercury Intrusion Porosimetry, and
DSC ermoporosimetry in Characterizing Pore Size Distri-
butions of Compressed Finely Ground Calcium Carbonate
Structures,Industrial & Engineering Chemistry Research,vol.
, no. , pp. –, .
[ ] Y. Ya o, D. L i u , Y. C h e , D . Ta n g , S . Ta n g , a n d W. Hu a n g , “ P e t r o -
physical characterization of coals by low-eld nuclear magnetic
resonance (NMR),Fuel,vol.,no.,pp.,.
[] E. Suuberg, “Elastic behaviour of coals studied by mercury
[] M. Peydayesh, M. Bagheri, T. Mohammadi, and O. Bakhtiari,
“Fabricati on optimization of p olyethersulfone (P ES)/polyv inyl-
pyrrolidone (PVP) nanoltration membranes using Box–Behn-
ken response surface method,RSC Advances,vol.,no.,pp.
–, .
[] H. Strathmann, K. Kock, P. Amar, and R. Baker, “e formation
mechanism of asymmetric membranes,” Desalination,vol.,
no. , pp. –, .
[] E. Saljoughi, M. Amirilargani, and T. Mohammadi, “Eect of
poly(vinyl pyrrolidone) concentration and coagulation bath
temperature on the morphology, permeability, and thermal
stability of asymmetric cellulose acetate membranes,” Journal of
Applied Polymer Science, vol. , no. , pp. –, .
[] N. Arahman, T. Maimun, Mukramah, and Syawaliah, “e
study of membrane formation via phase inversion method by
cloud point and light scattering experiment,” in Proceedings of
the AIP Conf,.
[] T. H. Muster and C. A. Prestidge, “Application of time-de-
pendent sessile drop contact angles on compacts to characterise
the surface energetics of sulfathiazole crystals,” International
Journal of Pharmaceutics,vol.,no.-,pp.,.
... Other bands present in all FTIR spectra are associated with the sulfone asymmetric and symmetrical stretching (1320, 1290, and 1150 cm − 1 ), the asymmetric stretching of the aromatic ether group (1240 cm − 1 ), C-S stretching vibrations (720 cm − 1 ), and S--O scissor angular deformations (555 cm − 1 ) of the sulfone group [30,54]. According to Milescu et al. [68], some of the bands can be attributed to the methylene group stretching (2950 and 2921 cm − 1 ), carbonyl groups (1655 cm − 1 ), pyrrolidinyl radical (1463 and 1424 cm − 1 ) and, C -N vibrations (1072 cm − 1 ) of the residual PVP still present in the polymeric membrane structures. ...
... The mass losses observed below 120 • C and around 140 • C were derived from the evaporation of moisture and residual NPM molecules. The first significant mass loss (310-430 • C) for all membranes is caused by the PVP polymer chains decomposition, while the second intense loss (430-630 • C) can be associated with the PES polymeric chains decomposition due to bound ruptures between aromatic rings and sulfone groups [27,68]. The mass loss at >630 • C results from the residual organic material carbonization and the water molecules evaporation formed in the vicinal silanol groups condensation of the mesomaterials incorporated in MMMs [27,37]. ...
The presence of recalcitrant compounds in aquatic systems, such as carbamazepine (CBZ), has intensified due to the wastewater discharge increase. This study aimed to evaluate the PES/mesoparticles-based MMM transport properties and their CBZ adsorption capacities in aqueous solutions with different physicochemical characteristics using a statistical design method. MMMs were synthesized via the phase inversion method using polyethersulfone as a polymeric matrix and mesoparticles as filler materials (MCM-41, NH 2-MCM-41, or SH-MCM-41). The MMMs were characterized by ATR-FTIR, DSC, SEM-EDS, TGA, and XRD. CBZ quantification was performed by ultra-performance liquid chromatography. The preliminary adsorption study showed that PES/SH-MCM-41-based MMMs present the highest potential for CBZ adsorption. The multivariate design results indicate that three independent variables (contact time, initial CBZ concentration, and the amount of SH-MCM-41 incorporated in MMM) significantly influence the MMM adsorption capacity, while pH does not affect it. Water permeability tests in MMMs showed a correlation between the H 2 O permeability and the porosity of the synthesized membranes. PES/SH-MCM-41-based MMM showed high porosity and good ability to remove CBZ from water, regardless of the pH of the aqueous solutions.
... For this reason, as one of the common polymeric materials, polyvinylpyrrolidone (PVP) has been attempted to be provided as one of the supporting materials replacing PP in the preparation of proton pump membrane in order to increase the reusability of the proton pump membrane for further application of TA measurement. As the hydrophilic polymer, the addition of PVP to the cocktail component can increase the permeability of membrane, indirectly leading to membranes less prone to fouling [13] due to the formation of well-defined pores [14,15]. Moreover, PVP is easy to use, has no or low toxicity [16] and good environmental stability, make it suitable to be used as supporting material for producing polymeric membranes [17]. ...
Total alkalinity is one of the important parameter in the regulation of seawater carbonate chemistry system to determine the capacity of water to neutralize acid. In this paper, a new proton pump membrane was successfully modified using polyvinylpyrrolidone (PVP) as a supporting material due to its excellent chemical properties. The surface morphology of the membrane was thoroughly studied using Scanning Electron Microscope (SEM), which showed the presence of pore structure, ascribed to the presence of low molecular weight of PVP. The absorption of membrane was studied using Ultraviolet-Visible (UV-Vis) spectrophotometer, where the peak appeared at 539 nm-1. The functional group of the modified membrane was analyzed using Fourier Transform Infrared Spectroscopy (FTIR), and the spectra showed almost similar between modified membrane with PVP and without PVP. The electrochemical behaviour of the membrane was evaluated by cyclic voltammetry (CV) using gold (Au) electrode and the resulting voltammogram showed that the modified membrane with PVP has higher current reading compared to the membrane without PVP, indicating that there is redox reaction occured during the immobilization. The condition and perfomance of modified proton pump membrane with PVP was compared and analyzed.
... ATR-FTIR analyses (Fig. S3) revealed that the use of Cyrene or spray coating did not alter the chemical structure of PES. The FTIR spectra of the top surface of C-PES-S-1 showed the characteristic bands of PES centred at 1104 cm -1 (C-O-C), 1148 cm -1 (S=O), 1240 cm -1 (C-O), 1320 cm -1 (C-SO2-C) , 1485 cm -1 and 1577 cm -1 (benzene ring) [37][38][39] . After the deposition of the PA selective layer via interfacial polymerisation, three new peaks centred at 1538, 1609 and 1656 cm -1 were observed. ...
Full-text available
Toxic solvents like n,n-dimethylformamide (DMF), n,n-dimethylethanamide (DMAc), and 1-methyl-2-pyrrolidone (NMP) are commonly used to fabricate polymer support membranes. Replacing these toxic solvents with green solvents such as Cyrene™ can imbue sustainability into membrane fabrication, but at the expense of poor membrane separation performances. Here we overcome this limitation by spray coating Cyrene™-based polymer dope solutions to form highly porous asymmetric membranes. The pure water flux of spray coated polyethersulfone (PES) membranes reached 206.6 L m-1 h-1, 7-folds higher than knife cast membranes. This significant increase in flux was ascribed to a porous, thin skin layer and macrovoids interconnected with finger-like pores in spray coated PES films. However, this did not impact on the ability to yield thin film composites (TFCs) with high separation performances. Through interfacial polymerisation, we deposited a polyamide selective layer on to the surface of spray coated PES films to yield TFCs for desalination of a 2000 ppm NaCl solution. The salt rejection rate and flux of such TFCs reached 93 % and 5.3 L m-1 h-1, respectively. This desalination performance was similar to knife cast membranes produced from DMF-, NMP- and DMAc-based polymer dope solutions, but fabricated here in a more sustainable manner. This indicated that spray coating could overcome the trade-off between poor membrane separation performance and sustainability.
... This shows that PVP is trapped in the PVDF membrane matrix, and is integrated with the polymer structure. PVP provides more hydrophilicity to PVDF membrane layers, as in PES membranes (35). Furthermore, the literature findings report that interactions can occur between sulfone groups (PES) and pyrrolidone groups (PVP), or between PES aromatic ring and side cyclic groups (PVP) through the study of the viscoelastic behaviour of these polymer blends (36). ...
Full-text available
In this investigation, polyvinylidene fluoride membranes were resulted by a phase inversion technique with polyvinylpyrrolidone (PVP) as an agent to form pores, as well as n-methyl pyrrolidone as a solvent. In addition, the effect of PVP concentration (1-4%) was investigated to prepare membranes with better membrane antifouling performance and characteristics. Furthermore, functional groups, morphological structures, and membrane porosity were analysed by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and membrane porosity calculation. The surface SEM images revealed that the size of the modified membrane pores increased. The increase of the PVP concentration added, resulted in the number of modified membrane pores. FTIR spectra confirmed that PVP functional groups were dispersed in the PVDF membrane matrix. Optimum pure water permeability (PWP) of 60 L/(m2•h•bar) was achieved using 3% PVP, resulting in a humic acid rejection percentage of 80% and a water flux recovery ratio (FRR) of 85%. These findings indicate that the utilization of PVP as a pre-forming agent resulted in higher PWP, lower humic acid rejection, and good antifouling properties.
... Before characterization, the membrane samples were gilded for 20 min. The membrane structures including average pore size, porosity and pore tortuosity were determined by mercury intrusion porosimetry (MIP) [34,35]. The hydrophilicity of membranes was evaluated by measuring the water contact angle (WCA) using a contact angle meter (SZ-CAMC31, Shanghai, China) according to the procedures: membrane samples were first immobilized on the glass slide, then 5 μL of ultra-pure water was dropped on the membrane surface to calculate the WCA using the software built-in program. ...
The superior hydrophilicity of graphene oxide (GO) makes it a promising candidate for improving the permeability and antifouling performance of membranes used for feed water pretreatment in desalination systems. However, the uncontrollable assembly structures of GO laminates on membrane surface restrict the full exertion of its hydrophilicity. In this study, a layer-by-layer self-assembled GO-based nanocomposite membrane with adjustable interlayer spacing and assembly layers was facilely fabricated by alternately depositing GO and (3-Aminopropyl) triethoxyilane modified silicon dioxide (SiO2@APTES) on membrane surface via electrostatic interaction. The fully exerted hydrophilicity of GO and well-maintained membrane pore structures facilitated the adsorption and penetration of water molecules, meanwhile, the hydration layer and electronegativity of GO effectively inhibited the adhesion of foulant. Thus, monolayer GO/SiO2@APTES/GO endowed P-(G/S/G)1 membrane with more than 10-fold water flux (560.2 L m⁻² h⁻¹) than pure PVDF membrane (55.4 L m⁻² h⁻¹) without sacrificing selectivity; and the antifouling performance was improved by nearly 50%. Moreover, the nanocomposite membrane presented robust structural stability after physicochemical cleaning. Overall, the nanocomposite membrane affords a novel facile way to fully exert the hydrophilicity of GO to improve permeability and antifouling performance, and is expected to provide an important guarantee for efficient operation of desalination system.
The usage of conventional solvent during the membrane fabrication could cause undesirable negative impact to the environment. Associated with this, greener alternative to membrane synthesis has grab the attention of researchers globally. Therefore, this study explored on the green synthesis of polyvinylidene fluoride (PVDF) membrane by adopting the natural ingredient Xanthan Gum (XG) biopolymer together with green solvent dimethyl sulfoxide (DMSO) to form a new generation PVDF membrane. The membrane was prepared by phase inversion method with different XG concentration ranging from 0 wt% to 1.5 wt% while maintaining the constant PVDF and DMSO concentration. Several membrane performance tests were done which included water flux test, Congo red (CR) rejection, and flux recovery ratio (FRR). In this study, the incorporation of XG in membrane shown enhancement in membrane hydrophilicity with a noticeably reduction of wettability from 48.67o to 42.15o. The results shown that membrane embedded with 0.5 wt% XG appeared as the optimum XG concentration. As for the membrane performance, it achieved the pure water flux and FRR of 182.87 L/m2.h and 91.25%, respectively. According to the overall performance evaluation, the incorporation of XG promoted the performance of membrane.
In the present study, nanocomposite polymeric membranes were fabricated using polyvinyl alcohol (PVA), cellulose acetate (CA) as polymers, and dimethyl sulfoxide (DMSO) as the solvent. The membrane was fabricated using the most widely adopted technique, phase immersion precipitation. To enhance the performance of the membrane, nanoparticles like TiO2, CaO, CdO, and ZrO were added to the polymeric solution and the doped polymeric solution was cast on a glass plate. Nine combinations of membranes were fabricated with two different concentrations (0.1 and 0.2%) of nanoparticles. The basic properties of the membranes such as density, porosity, viscosity, permeability, pure water flux, and water content were studied for the samples. The membrane pore structure and surface properties were identified and it was found that doping nanoparticles on the surface of membranes improved many properties like mechanical strength, stability, pore size, etc., allowing the membranes to perform better in extreme industrial‐level effluent treatment applications. High‐resolution scanning electron microscopy (SEM) showed the homogeneous dispersion of zirconium oxide, titanium dioxide, calcium oxide, and cadmium oxide nanoparticles on the surface of the PVA‐CA membrane. The doping of nanoparticles on the PVA‐CA membrane resulted in improved mechanical strength and good chemical oxidation stability. In comparison, the PCD‐TiO2 sample showed high thermal stability and oxidation stability at high temperatures, i.e., until 200°C which has a high potential for treating industrial effluents. This article is protected by copyright. All rights reserved
Full-text available
Bacterial nanocellulose has been widely investigated in drug delivery, but the incorporation of lipophilic drugs and controlling release kinetics still remain a challenge. The inclusion of polymer particles to encapsulate drugs could address both problems but is reported sparely. In the present study, a formulation approach based on in situ precipitation of poly(lactic-co-glycolic acid) within bacterial nanocellulose was developed using and comparing the conventional solvent N-methyl-2-pyrrolidone and the alternative solvents poly(ethylene glycol), CyreneTM and ethyl lactate. Using the best-performing solvents N-methyl-2-pyrrolidone and ethyl lactate, their fast diffusion during phase inversion led to the formation of homogenously distributed polymer microparticles with average diameters between 2.0 and 6.6 µm within the cellulose matrix. Despite polymer inclusion, the water absorption value of the material still remained at ~50% of the original value and the material was able to release 32 g/100 cm2 of the bound water. Mechanical characteristics were not impaired compared to the native material. The process was suitable for encapsulating the highly lipophilic drugs cannabidiol and 3-O-acetyl-11-keto-β-boswellic acid and enabled their sustained release with zero order kinetics over up to 10 days. Conclusively, controlled drug release for highly lipophilic compounds within bacterial nanocellulose could be achieved using sustainable solvents for preparation.
Full-text available
The performance of the membranes can be improved by adding the appropriate amount of nanomaterials to the polymeric membranes that can be used for water/wastewater treatment. In this study, the effects of polyvinylpyrrolidone (PVP), the impact of different amounts (0.5% and 1% wt.) of cellulose nanofibril (CNF), and the combined effects of PVP-CNF on the properties/performance of the polyethersulfone-based (PES-based) membrane are investigated. All PES-based ultrafiltration (UF) membranes are manufactured employing the phase inversion method and characterised via Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and the relevant techniques to determine the properties, including porosity, mean pore size, contact angle, water content, and pure water flux tests. Furthermore, the thermal properties of the prepared membranes are investigated using thermal gravimetric analysis (TGA) and differential thermal analysis (DTA) techniques. Experimental and numerical methods are applied for the mechanical characterisation of prepared membranes. For the experimental process, tensile tests under dry and wet conditions are conducted. The finite element (FE) method and Mori-Tanaka mean-field homogenisation are used as numerical methods to provide more detailed knowledge of membrane mechanics.
Full-text available
The possibility of replacing traditional toxic solvents normally employed during the preparation of polymeric membranes with greener alternatives represents a great challenge for safeguarding the human health and protecting the environment. In this work, an improved and pleasant-smelling version of dimethylsulfoxide (DMSO), i.e., DMSO EVOL™, was used as “greener solvent” for the preparation of polyethersulfone (PES) microfiltration (MF) membranes using a combination of non-solvent and vapor-induced (NIPS and VIPS, respectively) phase separation technique for the first time. The effect of two different additives polyvinylpyrrolidone (PVP) and poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) (Pluronic®) together with polyethylene glycol (PEG) on membrane properties and performances has been also evaluated. The membranes were characterized in terms of morphology, mechanical resistance, pore size, and water permeability. The obtained results show that DMSO EVOL™ is able to replace 1-methyl-2-pyrrolidone (NMP), which is a more toxic solvent normally used for the preparation of PES membranes. Furthermore, it was possible to tune the produced membranes in the range of MF (0.1–0.6 μm).
Full-text available
Herein response surface methodology (RSM) is employed to optimize the fabrication of polyethersulfone (PES) nanofiltration (NF) membranes via phase inversion. The Box–Behnken design matrix is applied to develop predictive regression models, minimize the number of experiments, and investigate the effects of parameters on the response. Four important parameters, including PES polymer concentration (18–22% w/w), PVP concentration (0–2% w/w), evaporation time (0–3 min) and coagulation bath temperature (0–50 °C), were chosen as independent variables and the optimization objectives were water flux and rejection. Consequently, 27 experiments were conducted to construct a quadratic model. The fabricated NF membranes were characterized via scanning electron microscopy (SEM) and water contact angle measurements. The performance of the fabricated membranes was evaluated using a bench scale cross-flow filtration unit. According to analysis of variance (ANOVA), all four independent parameters are statistically significant and the final model is reasonably accurate. Response surfaces and contours are plotted to represent the regression equations and their interpretation. Furthermore, the optimal experimental conditions for both water permeation flux and rejection were separately evaluated. The maximum permeation flux of 159.84 kg m⁻² h⁻¹ and rejection of 78.41% were achieved under the optimal fabrication parameters. Deviations between the predicted and actual responses of permeation flux and rejection were within 10% and 3%, respectively, which confirm the accuracy and validation of the model.
Full-text available
Cyrene as a bio-alternative solvent: a highly efficient, waste minimizing protocol for the synthesis of ureas from isocyanates and secondary amines in the bio-available solvent Cyrene is reported. This method eliminated the use of toxic solvents, such as DMF, and established a simple work-up procedure for removal of the Cyrene, which led to a 28-fold increase in molar efficiency versus industrial standard protocols.
Full-text available
Circa’s proprietary Furaceli™ technology is an industry-leading innovation that enables the manufacture of levoglucosenone (LGE), a potential platform chemical having a highly functional C6 structure, from a range of renewable waste and non-food source cellulosic feedstocks (e.g. straw, bagasse, sawdust). One use of LGE is conversion into a “green” alternative bio-solvent dihydrolevoglucosenone (known as Cyrene™). Furaceli™ is currently the only technology that allows production of LGE and Cyrene™ on a scalable basis. The Furaceli™ process takes lignocellulosic material and uses a combination of catalysts and heat to form LGE, biochar and water. The vapours formed during the process are separated from the biochar, distilled and purified before subsequent catalytic hydrogenation to form (Cyrene™). Cyrene™ is a renewable non-toxic solvent that has the potential for widespread use in the pharmaceutical and other industries. Following successful international market trials of Cyrene™, Circa and Norske Skog are now ready to build a 50 tpa developmental facility (FC5) to demonstrate to investors and customers a large-scale prototype before committing to a larger-scale commercial plant. In order to gain environmental approvals to construct FC5, an environmental effects report is required in which the composition and concentration of any compounds present are identified and their potential environmental effect predicted. The major process water components from the Furaceli™ process have been identified by gas chromatography/ mass spectrometry (GC/MS) analysis of earlier pilot plant streams to consist of short chain (<C5) C-0 compounds, short chain (<C5) carboxylic acids, non-aromatic & aromatic cyclic compounds, plus minor amounts of product and catalyst that will not be retained within the proto-type plant. A proprietary mass-balance process model has been used to estimate the likely concentrations of the major process water components in effluent proceeding to biological treatment. The ability of these components to be degraded in a biological treatment process has been established from literature data, thus enabling the estimation of their final concentration in treated effluent. Published toxicity data for these components has been used to establish that the final treated effluent is not likely to have to any toxicity to aquatic species.
Conference Paper
Full-text available
The composition of polymer solution and the methods of membrane preparation determine the solidification process of membrane. The formation of membrane structure prepared via non-solvent induced phase separation (NIPS) method is mostly determined by phase separation process between polymer, solvent, and non-solvent. This paper discusses the phase separation process of polymer solution containing Polyethersulfone (PES), N-methylpirrolidone (NMP), and surfactant Tetronic 1307 (Tet). Cloud point experiment is conducted to determine the amount of non-solvent needed on induced phase separation. Amount of water required as a non-solvent decreases by the addition of surfactant Tet. Kinetics of phase separation for such system is studied by the light scattering measurement. With the addition of Tet., the delayed phase separation is observed and the structure growth rate decreases. Moreover, the morphology of fabricated membrane from those polymer systems is analyzed by scanning electron microscopy (SEM). The imag...
The surface fouling of UF membranes used upstream as pre-treatment stage is critical for the long-term stability of the subsequent treatment stage (NF/RO membranes). In this paper, an attempt was made to probe and compare the potential of versatile UF membranes structures in terms of flux decline and selectivity, for more convenient pretreatment membranes selection. The role of polyethersulfone (PES) host polymer concentration, on the morphology and surface characteristics of asymmetric flat sheet ultrafiltration (UF) membranes, has been comprehensively investigated. Distinctly, as the casting solution viscosity decrease, a higher pore size, pore size distribution and pure water flux was observed along with lower mechanical properties and wider cross-section morphologies. However, this impact was trivial on water contact angle, surface roughness parameters and charge negativity of the membrane. To further assess the potential performance of the handmade fabricated membranes , they were systematically evaluated against three organic model foulants with dissimilar origins; humic acid (HA)-as natural organic matters (NOM), sodium alginate (NaAlg)-as polysaccharide, and bovine serum albumin (BSA)-as protein, under different initial feed concentration and pH chemistry. A disparate fouling behavior was observed depending on the membrane characteristics and the organic model foulant used. Depending on the UF membrane cutoff used, lower MWCO membranes, PES22 (6 kDa) and PES20 (10 kDa) exhibited a negligible relative flux decline while extremely low relative flux patterns were observed in the filtration with the 100 kDa membrane (PES16), as a result of one or more pore blocking mechanisms observed.
Polyethersulfone (PESU) porous membranes with high pure water permeability were successfully produced by coupling non-solvent induced phase separation (NIPS) with vapor induced phase separation (VIPS) techniques by employing Rhodiasolv®Polarclean (Polarclean®) for the first time, as eco-friendly sustainable solvent. Membrane morphology and performance were tailored by varying the casting solution composition and the exposure time to controlled humidity and temperature. Polyvinylpyrrolidone (PVP) and poly(ethylene glycol) (PEG) were used as hydrophilic pore former agent and small-molecule liquid, respectively. The resulting membranes were characterized in terms of morphology, thickness, porosity, contact angle, mechanical features, pore size and pure water permeability. The obtained data indicated that the exposure time to humid air as well as the polymer and the PEG concentration in the casting solution represent the most relevant parameters to obtain hydrophilic membranes with different structure and properties. Both ultrafiltration (UF) and microfiltration (MF) membranes, with a pore size ranging from ~0.04 to ~0.4 µm, were efficiently prepared by using the investigated novel solvent, offering the possibility to replace commonly used toxic diluents in polysulfones’ membrane fabrication.
We fabricated flat-sheet and hollow fiber membranes from polyethersulfone (PES) solutions in two ionic liquids: 1-ethyl-3-methylimidazolium diethyl phosphate ([EMIM]DEP) and 1,3-dimethylimidazolium dimethyl phosphate ([MMIM]DMP). The solvents are non-volatile and less toxic than organic solvents, such as dimethylformamide (DMF). The membranes morphologies were compared with those of membranes prepared from solutions in DMF, using electron microscopy. Water permeance, solute rejection and mechanical strengths were evaluated. Membranes were applied to DNA separation. While membranes based on PES were successfully prepared, polysulfone (PSf) does not dissolve in the same ionic liquids. The discrepancy between PES and PSf could not be explained using classical Flory-Huggins theory, which does not consider the coulombic contributions in ionic liquids. The differences in solubility could be understood, by applying density functional theory to estimate the interaction energy between the different polymers and solvents. The theoretical results were supported by experimental measurements of intrinsic viscosity and dynamic light scattering (DLS).
Nanomaterials have many advanced applications, from bio-medicine to flexible electronics to energy storage, and the broad interest in graphene-based materials and devices means that high annual tonnages will be required to meet this demand. However, manufacturing at the required scale remains unfeasible until economic and environmental obstacles are resolved. Liquid exfoliation of graphite is the preferred scalable method to prepare large quantities of good quality graphene, but only low concentrations are achieved and the solvents habitually employed are toxic. Furthermore, good dispersions of nanomaterials in organic solvents are crucial for the synthesis of many types of nanocomposites. To address the performance and safety issues of solvent use, a bespoke approach to solvent selection was developed and the renewable solvent Cyrene was identified as having excellent properties. Graphene dispersions in Cyrene were found to be an order of magnitude more concentrated than those achieved in N-methylpyrrolidinone (NMP). Key attributes to this success are optimum solvent polarity, and importantly a high viscosity. We report the role of viscosity as crucial for the creation of larger and less defective graphene flakes. These findings can equally be applied to the dispersion of other layered bi-dimensional materials, where alternative solvent options could be used as drop-in replacements for established processes without disruption or the need to use specialized equipment. Thus, the discovery of a benign yet high performance graphene processing solvent enhances the efficiency, sustainability and commercial potential of this ever-growing field, particularly in the area of bulk material processing for large volume applications.
A novel, highly hydrophilic nanocomposite additive, sulfonated graphene oxide (SGO), was synthesized from graphene oxides (GO), and characterized using a range of techniques. To examine the effects of the sulfonic acid groups of the filler particles on the polyvinylidene fluoride (PVDF) membrane performance, the PVDF-GO/SGO modified membranes were obtained through phase inversion by dispersing GO and different concentrations of SGO (0.4 - 1.2 wt. %). The surface of the prepared membranes was analyzed by scanning electron microscopy and atomic force microscopy. The addition of GO and SGO caused by an increase in surface roughness, porosity, and pore size of the membranes compared to the PVDF membrane. The P-SGO and P-GO blend membranes showed a 146.6% and 53.3% enhancement of the water permeation flux, respectively. The presence of additional sulfonic groups (-SO3H) on SGO supports hold a thicker water hydrogen layer and improve the water flux. The anchored -SO3H group in SGO is a stronger hydrogen-bonding group compared to the -COOH/-OH groups present in GO. From the antifouling test, P-SGO with the 0.8 wt. % blend membranes exhibited a high water flux recovery ratio (FRR) of 88.7% and low irreversible fouling ( ) Of 11.2% compared to the GO nanocomposite membrane (75% and 24%, respectively). This was recognized to the high hydrogen bonding forces and electrostatic repulsion of SGO against the fouling proteins. Overall, the induced SGO nanoparticle opens a novel path to enhance the hydrophilicity, water flux, antifouling, and mechanical performance of PVDF ultrafiltration membranes.