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Desalination of simulated seawater by purge-air

pervaporation using an innovative fabricated membrane

Mona Naim Mahmoud Elewa Ahmed El-Shafei and Abeer Moneer

ABSTRACT

An innovative polymeric membrane has been invented which presents a breakthrough in the 1047297eld of

desalination membranes It can desalinate simulated seawater of exceptionally high concentration to

produce a high 1047298ux of potable water with over 997 salt rejection (SR) in a once-through purge-air

pervaporation (PV) process A set-up was constructed for conducting the desalination experiments

and the effect of initial salt solution concentration (Ci) and pervaporation temperature (T pv) on the

water 1047298ux ( J ) SR separation factor and pervaporation separation index were determined The

membrane was prepared by the phase-inversion technique of a specially formulated casting solution

consisting of 1047297

ve ingredients after which the membrane was subjected to a post-treatment by whichcertain properties were conferred The results con1047297rmed that the salinity of the pervaporate was

independent of Ci (all SR above 997) The best result was at T pvfrac14 70 W

C where J varied from 597 to

345 lm2 h for C ifrac14 40ndash140 g NaCll respectively The membrane morphology was con1047297rmed to be

asymmetric The contact angle was immeasurable indicating the membrane to be super-hydrophilic

Activation energies computed using Arrhenius law were under all conditions investigated less than

20 kJmol K

Mona Naim

Chemical Engineering Department Faculty of

Engineering

Alexandria University

Alexandria

Egypt

Mahmoud Elewa

Research Development Department

Arab Academy for Science Technology and

Maritime Transport

Alexandria

Egypt

Ahmed El-Shafei (corresponding author)

Agricultural and Biosystems Engineering Faculty

of Agriculture


Alexandria

Egypt

E-mail ahmedelsha1047297 alexuedueg

Abeer Moneer

National Institute of Oceanography and Fisheries

Alexandria

EgyptKey words | activation energy cellulose acetate desalination membranes pervaporation

INTRODUCTION

Water is a vital resource of life As access to fresh water

becomes increasingly limited in many areas of the world

the ability to desalinate seawater is expected to take on

greater signi1047297cance Recently pervaporation (PV) has

been exploited as a promising membrane separation tech-

nology which separates mixtures by preferential removal

of one component from others present in the mixture due

to its higher af 1047297nity with andor faster diffusion rate

through a non-porous membrane In the PV process

mass transfer takes place by vapour pressure difference

and the liquid mixture is maintained at atmospheric

pressure on the upstream while the permeate is removedon the other side as a vapour due to the low pressure

achieved by using either a vacuum pump or a carrier

purge gas on the downstream (Kulkarni et al ) PV

has been extensively used for separation or concentration

of mixtures of aqueousndashorganic liquids eg dehydration

of alcohols (Hu et al Kuila amp Ray Pandey amp

Shahi ) It has also been widely used in the separation

of azeotropic mixtures (Luyben ) separation of water

from organic solvent (Lu amp Chen ) removal of trace

organics from water (Knight et al ) and separation

of organic mixtures (Smitha et al ) However there

are only limited studies on the application of this technol-

ogy in water desalination (Kuznetsov et al Ben

Hamouda et al Cho et al Swenson et al )

PV of an aqueous salt solution can be regarded as separ-

ation of a pseudo-liquid mixture containing free water

molecules and bulkier hydrated ions formed by dis-

sociation of the salt in water (Kuznetsov et al )

Membranes used in previous studies on PV desalination

include sulphonated polyethylene (Korin et al ) qua-ternized polyethylene (Korngold et al )

polyetherimide and polyether ester (Quintildeones-Bolantildeos

et al ) in which 1047298uxes were very low although the

PV temperature was in the region of 40ndash82 W

C The feed

temperature was a crucial parameter due to the increase

in diffusivity and reduction in viscosity that occurs on heat-

ing However the inherent permeability of the membrane

polymer is also extremely important (Xie et al )

785 copy IWA Publishing 2015 Water Science amp Technology | 725 | 2015

doi 102166wst2015277



Gong et al () successfully prepared super hydrophi-

lic nano-hybrid membrane by in situ ultraviolet irradiation

of titanium dioxide (TiO2) nano-particles embedded in poly-

electrolyte complexes in which the TiO2 precursor solution

was dynamically 1047297ltered through a layer-by-layer-assembled

poly(ethylene-imine)poly(acrylic acid) multi-layer under aspeci1047297c pressure The permeate 1047298ux was however only

865 gm2 h The preparation of hybrid polymer super hydro-

philic 1047297lms has not proven to be feasible as the uniform

dispersion of TiO2 nano-particles in the polymer is very dif-

1047297cult (Gong et al ) Also novel inorganicndashpolymer

hybrid membranes were prepared by Zhu et al () by

incorporation of nano-TiO2 into regenerated cellulose by

phase inversion and were tested in the separation of capro-

lactamndashwater mixtures by PV

The aim of the present work is to fabricate by purge-air

pervaporation a novel hydrophilic cellulose-based membrane

that is suitable for desalinating saline water of exceptionally

high initial concentration and provides the highest possible

1047298ux andsalt rejection (SR) Theeffect of solution concentration

(C i) andpervaporation temperature (T pv) on the values of water

1047298ux ( J ) and SR are to be evaluated In addition separation

factor (α ) and pervaporation separation index (PSI) are also

to be computed The morphology of the membrane is to be

determined via examination by scanning electron microscopy

(SEM) and Fourier transform infrared (FT-IR) spectra and

the contact angle of fabricated membrane will then be deter-

mined Finally the activation energy (Ea) for permeation

through themembrane is to be determined through applicationof the Arrhenius law

MATERIALS AND METHODS

Cellulose acetate powder (CA) (product of Panreac Egypt)

acetone (A) dimethyl phthalate (DMP) and dimethyl for-

mamide (DMF) (products of Adwic Egypt) glycerol (G)

and sodium chloride (products of El-Nasr Chemicals

Egypt) and sodium hydroxide (product of Chemajet

Egypt) were all used as received

Membrane preparation

CA powder was added to a wide-mouthed glass-stoppered

bottle then dissolved in a mixture of solventsadditives The

mixture was initially mixed manually using a glass rod The

bottle was then stoppered tightly and shaken gently until com-

plete dissolution had taken place after which the mixture was

left for 2 days for removal of air bubbles The membrane was

composed of CA A DMF DMP and G in de1047297nite pro-

portions The solution was cast into a membrane on a

smooth uniform glass plate of a casting assembly using a

doctorrsquos blade The as-cast membrane was allowed to evapor-

ate for exactly 05 minute after which the glass sheet was

immersed in ice-cold distilled water in a tray for 1 hour forcoagulation to take place The membrane was subjected to

complete deacetylation by steeping for 24 hours in an aqueous

alkaline bath consisting of 1 sodium hydroxide and 20

sodium chloride The membrane was then washed by repeti-

tive rinsing in distilled water and then storedin distilledwater

Membrane characterization

The cross-section morphology of the membrane was examined

using SEM (JOELJSM 6360 LA Japan) FT-IR spectra of the

membrane was obtained by a VERTEX 70 spectrometer

(Bruker Co Germany) Water contact angle was measured to

evaluate the hydrophilicity of the membrane surface The

static contact angles of water on the membrane surface were

measured by a contact angle goniometer (JC-2000C Contact

Angle Meter Powereach Co Shanghai China) The average

value of static contact angle on the membrane was calculated

for at least 1047297ve different locations on the membrane

Pervaporation testing

A simple PV test cell was used in all the PV experiments

The cell consisted of two identical plexi-glass rectangularparts 25 cm thick 15 cm long and 10 cm wide Each part

contained a compartment consisting of hexagonal grooves

5 mm deep with numerous lateral corrugations to induce

partial turbulence of the 1047298owing liquid on the feed side of

the membrane Before operation the two cell halves were

1047297rmly held together such that the membrane completely sep-

arated the two halves Rubber gaskets functioned as liquid

seals A schematic of the assembled unit is shown in

Figure 1 It consisted of the PV test cell a round-bottomed

1047298ask an air blower two small centrifugal pumps an electric

heater a glass Liebig condenser a thermometer and a recei-

ver 1047298ask The membrane was placed in the test cell and theunit was connected Two litres of heated NaCl solution were

made to recycle through the top compartment of the cell

The pumps and the blower were operated and the permeate

was collected in the receiver through the condenser through

which ice-cold water was made to recycle Recycling of the

hot saline solution ensured constancy of its temperature

adjacent to the membrane The permeate was collected at

different time intervals and then the concentration of

786 M Naim et al | Desalination of simulated seawater using an innovative fabricated membrane Water Science amp Technology | 725 | 2015



sodium chloride in the permeate was traced through con-

ductivity measurements

PV membrane performance

Performance of the PV membrane is determined by the

values of J SR α and PSI and Ea as follows in which

J frac14Q

A t (1)

SR frac14C i C f

C itimes 100 (2)

α frac14Y w=Y s

X w= X stimes 100 (3)

PSI frac14 J times α (4)

where Q is the mass of the permeate collected in time t A is

the effective membrane area C i and C f are the initial and

1047297nal solution concentration Y and X are the weight of water in the pervaporate and feed respectively the suf 1047297 x

w refers to water and s refers to solute

The dependence of 1047298ux on T pv could be expressed by

Arrhenius law as follows and from which Ea could be com-

puted

J frac14 Ap exp Ea

RT

(5)

where Ap R and T are the pre-exponential factor universal

gas constant and feed temperature in absolute units respect-

ively Ea is determined from the plot of ln( J ) versus 1T A

linear relationship is produced from which Ea is computed

from the slope of the straight line

RESULTS AND DISCUSSION

In this work the innovative membrane prepared by our group

was initiallyexamined for the morphology of its cross-section

by SEM FT-IR and contact angle and then J SR α and

PSI weredetermined The variablesC i and T pv were evaluated

as to their effect on the membrane performance Ea was

computed during PV at different C i values

Characterization of fabricated membranes

Figure 2 presents the cross-section micrograph of a perfect

asymmetric membrane showing the skin layer (thickness

20ndash25 μm) with mini-pores which are responsible for reject-

ing the salt The mini-pores gradually enlarge from the top

surface to the underside of the membrane in which very

large voids are apparent This unique morphology allowed

perfect rejection of salt by the skin layer while offering

high 1047298uxes due to the porous structure of the remaining

matrix

The FT-IR spectra of the fabricated membrane are illus-

trated in Figure 3 from which it is clear that the membranehas OH functional group (3000ndash3750 m1) Besides the typi-

cal hydroxyl group which makes the membrane super-

hydrophilic due to the presence of three OH groups per

anhydro-glucose unit the additional peak at 1640ndash1630 m1

Figure 1 | A schematic of the pervaporation set-up (1) pervaporation cell (2) feed cen-

trifugal pump (3) feed 1047298ask (4) electric heater (5) air blower (6) receiver 1047298ask

(7) Liebig condenser (8) cooling water centrifugal pump (9) cooling water

tank and (10) thermometer

Figure 2 | SEM micrograph of cross-section for fabricated membrane




clari1047297es the adsorption of water which not only assists in

the make and break of hydrogen bonding of water but also

causes easy permeation of water across the membrane In

addition the peak at 1125ndash1170 m1 is attributed to CndashOndashC

asymmetric stretching vibration (arabinose side chain)

while the peak at 1040ndash1050 m1 is assigned to CndashO

stretching in CndashOndashC glycosidic bonds both of which con-

1047297rmed the existence of the ether linkages between the

anhydro-glucose units and the asymmetricstretch of the arabi-

nose side chain It has also been veri1047297ed that none of the

solventsadditives were retained in the membrane matrix

and that they were leached out during coagulation and

post-washing

It is generally accepted that contact angles indicate

whether the surface is hydrophilic or otherwise so that if

the liquid molecules are strongly attracted to the solid mol-

ecules then the liquid drop will completely spread out on

the solid surface corresponding to a contact angle of 0W

In this case the surface is super-hydrophilic which was

the case of our membrane which gave 0

W

contact angleAccordingly the result emphasizes the super-hydrophilic

nature of our membrane

Effect of C i on PV membrane performance

Effect of C i is presented in Figures 4ndash7 Figure 4 clari1047297es the

effect of C i on J at various T pv from which it is clear that the

highest 1047298ux (597 lm2 h) was obtained at C ifrac14 40 gl at

T pvfrac14 70 W

C Moreover the 1047298ux declined by about 1 lm2 h

on increasing C i from the range of 34ndash60 gl to about

140 gl at all T pv tested which indicates that the membranedue to its super hydrophilicity is only slightly affected by the

salt concentration which is an advantage It is also observed

that the minimum 1047298ux is almost 2 lm2 h at 50 W

C which is

much higher than for other membranes cited in the litera-

ture for the dehydration of alcohols (Chapman et al

Hu et al Kuila amp Ray Pandey amp Shahi ) It

is also observed that the 1047298ux increases directly with T pv as

indicated in the 1047297gure

Figure 4 | Effect of initial concentration on pervaporate 1047298ux at different pervaporate

temperatures

Figure 3 | FT-IR spectra of fabricated membrane




However it is noteworthy that our membrane was fabri-

cated by a simple single step and cheap phase inversion

technique by which the super-hydrophilic cellulose-based

asymmetric membrane was generated In contrast other

membranes especially prepared for desalination by perva-

poration were based on very sophisticated andcomplicated multi-stage fabrication methods involving elec-

trospraying of PVA and electrospinning polyacrylonitrile

superimposed on a polyethylene terephthalate layer to com-

plete the composite membrane (Liang et al ) and

sulphochlorination and amination followed by quaterniza-

tion of already made polyethylene hollow 1047297 bres (Korngold

et al ) Liang et al () illustrated that the 1047298uxes of

their membrane were 853 724 and 557 lm2 h when the

initial NaCl solution concentrations were 5 35 and 50 gl

respectively

To this end water 1047298uxes of 25 and 039 kgm2 h were

reported for feed concentrations of 100 and 5500 mgl

Nathorn respectively by Swenson et al () when using several

deposits of dense natural clinoptilolite which exhibited both

high zeolite content and essentially no macroporosity or

inter-crystalline voids These values are much lower than

those obtained in our present work Moreover in a study

by Xie et al () a hybrid organicndashinorganic membrane

was synthesized via a solndashgel route in which the effects of

heat treatment on the separation of aqueous salt solutionin terms of J and SR were determined The authors used

an aqueous salt solution containing only 2 gl as the feed sol-

ution yet the 1047298uxes achieved were all less than 6 kgm2 h

despite very dilute feed solution concentration being used

However SR approached 995 In addition Ben

Hamouda et al () prepared polyether block amide

(PEBAX) membranes from commercial hydrophobic

PEBAX 2533 granules by dissolving the copolymer in

dimethyl-acetamide at 100 W

C The obtained 20 wt solution

was cast on a heated glass plate at 60 W

C followed by evapor-

ating the solvent at 60 W

C in an oven then drying under

vacuum at 80 W

C It was demonstrated in their work thatthe water 1047298ux varied inversely with NaCl concentration

reaching 18 kgm2 h at 03 moldm3 which decreased to

122 kgm2 h at 35 moldm3 The method is energy-inten-

sive while in comparison our membrane does not need

any heating in its preparation In addition the 1047298ux is much

lower than in our case Furthermore Cho et al ()

claimed a high water 1047298ux of 19 kgm2 h at 69 W

C by the

application of pervapourative seawater desalination using

Figure 5 | Effect of initial concentration on SR at different pervaporate temperatures

Figure 6 | Effect of initial concentration on separation factor at different pervaporate

temperatures

Figure 7 | Effect of initial concentration on PSI at different pervaporate temperatures




a NaA zeolite membrane which exhibited 999 SR They

attributed the high 1047298ux to the electrostatic interaction

between the surface charge and the polar water in which

the surface charge was positive in the seawater whereas in

the pure water it was negative making the water 1047298ux

in the seawater much higher than that in the pure water at T pv lower than 100

W

C The high rejections were attributed

to a joint size exclusioncharge exclusionsurface evapor-

ation mechanism The higher water 1047298ux and low Ea

(3739 kJmol) were explained by the reduced electrostatic

interaction between the positive surface charge and the

polar water However Cho et al () obtained a maximum

1047298ux of 6111 kgm2 h at a feed of only 0133 M NaCl at

pHfrac14 579 which is a much lower C i than in our case

In this regard in our present work J frac14 597 lm2 h was

reached when C i was much higher (40 gl) which indicates

the high performance of our membrane in desalinating

highly concentrated seawater

Figure 5 illustrates the effect of C i on SR It is observed

that in all cases SR is higher than 997 indicating that SR

is independent of C i and T pv which proves that the mem-

brane is of exceptionally high performance as regards 1047298ux

as well as SR However it is worth noting that it was

initially intended to investigate the membrane performance

in the range C ifrac14 34ndash60 gl which is typical for seawaters

but a few experiments were conducted at exceptionally

high C i to test the membrane performance under drastic con-

ditions The results proved to our surprise from Figures 4

and 5 that the highest SR (999) was obtained underthese high C i conditions at which J varied between 2 and

4 lm2 h which is a promising result that enables the mem-

brane to be applied in membrane crystallization for the

production of salt crystals plus extra fresh water thus sustain-

ing zero liquid discharge methodology from reverse osmosis

(RO) brines and assisting in protection of the environment ( Ji

et al )

Figure 6 clari1047297es the effect of C i on the α at various T pv

It is noteworthy that α is inversely proportional to T pv at

extremely high C i reaching 30667 at C ifrac14 140 gl at 50 W

C

This result may be attributed to the fact that at lower temp-

eratures lower salt contents are liable to diffuse with thepervaporate This result is dramatic and has never been

reached in all papers cited in the literature for membranes

used in the dehydration of alcohols except for Gong et al

() with α frac14 189981 However at much lower C i in the

range 30ndash60 gl α varies between 377 and about 5168 at

all T pv used This point is of great interest in that this particu-

lar membrane may be used in desalinating the brines

resulting from RO desalination units before dumping into

the sea to minimize pollution of the environment obtain

extra fresh water and concomitantly obtain much more con-

centrated brines which can yield salt crystals in

crystallization ponds more rapidly Moreover membrane

crystallization can be effected by using the membrane distil-

lation (MD) technique with hydrophobic membranes toobtain salt crystals with additional fresh water as a second

step (Edwie amp Chung ) In this way the combined desa-

lination using our innovative membrane by PV followed by

MD coupled with membrane crystallization resulted in zero

liquid discharge

The effect of C i on PSI is observed by inspecting Figure 7

It is noticed that PSI increases directly with C i at all T pv

reaching 55932 lm2 h at 80 W

C This is an extremely high

value However the value of PSI seems to be much more

affected by the value of α rather than J especially in our pre-

sent case since α is much larger than J

Effect of T pv on PV membrane performance

Effect of T pv on 1047298ux at different C i is illustrated in Figure 8

which indicates that J increases with increase in T pv as

expected The 1047297gure also indicates that J varies inversely with

C i Accordingly high T pv is preferred Figure 9 clari1047297es the

effect of T PV on SR which shows that extremely high SRs

(over 997) are obtained at all C i in the range 40ndash140 gl

Once again this result emphasizes the exceptional SR ability

of our fabricated membrane due to its distinct morphology

The effect of T pv on the value of α is depicted inFigure 10 It shows that α is very high at almost all values

of T pv ranging from 50 to 80 W

C Although varying widely

Figure 8 | Effect of pervaporation temperature on pervaporate 1047298ux at different initial

concentration




however α tends to be around 1700 at lower C i (40ndash50 gl)

Conversely as C i decreases from 50 to 48 gl the relation

between α and T pv is almost a straight line with a small nega-

tive slope Then as C i increases from 48 to 140 gl the

negative slope of the line connecting the points increases

markedly which refers to increasing the pervaporate con-centration from 0006 to 0144 gl due to increasing the

1047298ux to 597 lm2 h However as the temperature increases

from 70 to 80 W

C α increases markedly to an extremely

high value of about 20988 due to decreasing the pervapo-

rate concentration from 0144 to 0008 gl These results

point out that when high separation factors are required a

low T pv (such as 50 W

C) is preferred accompanied with

very high C i around 140 gl This is logical since diffusion

of the hydrated salt molecules tends to be slower at lower

T pv due to lower energy provided Moreover the present

membrane has proven to provide exceptionally high SR

especially at the highest C i studied in the present work as

shown in Figure 9

The effect of C i on PSI is illustrated in Figure 11 fromwhich it is veri1047297ed that the value of PSI is greatly dependent

on α rather than J The reader is asked to compare the gen-

eral shape of the curves in the present 1047297gure to those in

Figure 10 relating α with T pv It is noteworthy that the

highest value of PSI achieved in the present investigation

is identical to that obtained from Figure 11 namely

55932 lm2 h

Activation energy

Figure 12 illustrates an Arrhenius plot from which Ea was

calculated from the plot relating the 1047298ux as ln( J ) and the

reciprocal of absolute temperature (T pv) the pre-exponen-

tial factor ( A p) gas constant and Ea the latter computed

from the slopes of the lines The sharp variation of Ea

with C i is clari1047297ed in Figure 13 Ea values were 2171

1983 1594 and 2021 kJmol K at 40 48 50 and 140 g

NaCll respectively from which it is clear that the

values obtained are low to a great extent which is trans-

lated into the great ease of permeation of vapourwater

through our innovative membrane An average value of

Ea at T pv in the range C ifrac14 40ndash140 gl equals 1942 kJ

mol K For the sake of comparison Ea was found to be3739 kJmol K by Cho et al () for water transport

through NaA zeolite membranes whereas Xie et al ()

Figure 9 | Effect of pervaporation temperature on SR at different initial concentration

Figure 10 | Effect of pervaporation temperature on separation factor at different initial

concentration

Figure 11 | Effect of pervaporation temperature on PSI at different initial concentration




found Ea varied from 238 to 201 kJmol K when the salt

concentration in the feed was increased from 02 to

50 wt for hybrid organicndashinorganic membrane However

the lowest Ea was when C ifrac14 50 gl which may be due to

production of a reasonable quantity of vapour which

easily permeates the super-hydrophilic membrane at thesame time the salt amount is not very high such that it

will block the vapour at the boundary layer in the vicinity

of the membranersquos surface This explains why at higher C i

than the aforementioned situation Ea becomes larger since

the opposite of the previous reasoning takes place In other

words at lower T pv the vapour generated is less whereas at

higher C i the salt mass fraction is great causing some con-

centration polarization as well as reducing the mass

fraction of water 1047298owing adjacent to the membranersquos sur-

face resulting in greater resistance to diffusion and

permeation despite the membrane being super-hydrophilic

CONCLUSIONS

From the present work the following conclusions were

arrived at

1 An innovative super-hydrophilic membrane was fabri-

cated by a facile method using the phase inversion

technique

2 The membrane consisted of cellulose regenerated from a

casting solution comprising CA dissolved in de1047297nite pro-

portions of A DMF DMP and G

3 The membrane micrograph of SEM examination proved

the membrane to be of a unique asymmetric morphologywith a thin rejection layer of minute pores and a matrix

of intact pores that gradually increase in size to form very

large voids near the underside of the membrane

4 The contact angle was unreadable (could not be read)

demonstrating the membranersquos super-hydrophilicity

5 Exceptionally high 1047298ux reaching 597 lm2 h and remark-

able SRs above 997 were obtained

6 The membrane resulted in extremely high SR

approaching 100 at high C ifrac14 140 g NaCl per litre of sol-

ution which has not been reported in the literature

before

7 The 1047298ux increased directly with T pv while SR was not

affected by T pv and was at all times greater than 997

for C i up to 140 gl

8 Separation factors increased strongly with C i reaching

30667 at C ifrac14 140 gl also extremely high values of

PSI were obtained (55932 lm2 h a t 8 0 W

C and C ifrac14

140 gl) which to the best of our knowledge has never

been reported in the literature Thus the membrane is

extremely suitable for desalinating exceptionally high

salt-water concentrations by PV

9 Activation energies obtained from the Arrhenius

equation were under all conditions investigated less

than 2171 kJmol K which proves the great ease of

vapour permeation through the membrane

ACKNOWLEDGEMENT

The authors wish to acknowledge the kind support of the

Science and Technology Development Funds (STDF) of

Figure 13 | Effect of initial concentration on the values of activation energy (E a) com-

puted from Arrhenius equation

Figure 12 | Plot of ln( J ) versus the reciprocal of T pv at different initial concentration




Egypt for funding the research project (ID 4060) on desali-

nation of seawater through the application of purge-air

pervaporation technique

REFERENCES

BenHamoudaS BoubakriA Nguyen Q Tamp BenAmorM

PEBAX membranes for water desalination by pervaporation

process High Performance Polymers 23 (2) 170ndash173

Chapman P D Oliveira T Livingston A G amp Li K

Membranes for the dehydration of solvents by pervaporation

Journal of Membrane Science 318 (1ndash2) 5ndash37

Cho C H Oh K Y Kim S K Yeo J G amp Sharma P

Pervaporative seawater desalination using NaA zeolite

membrane mechanisms of high water 1047298ux and high salt

rejection Journal of Membrane Science 371 (1ndash2) 226ndash238

Edwie F amp Chung T-S Development of simultaneous

membrane distillation-crystallization (SMDC) technology for

treatment of saturated brine Chemical Engineering Science

98 160ndash172

Gong L Zhang L Wang N Li J Ji S Guo H Zhang G amp

Zhang Z In situ ultraviolet-light-induced TiO2 nanohybrid

superhydrophilic membrane for pervaporation dehydration

Separation and Puri 1047297cation Technology 122 32ndash40

Hu S Y Zhang Y Lawless D amp Feng X Composite

membranes comprising of polyvinylamine-poly(vinyl

alcohol) incorporated with carbon nanotubes for

dehydration of ethylene glycol by pervaporation Journal of

Membrane Science 417ndash418 34ndash44

Ji X Curcio E Al Obaidani S Di Pro1047297o G Fontananova E amp

Drioli E Membrane distillation-crystallization of

seawater reverse osmosis brines Separation and Puri 1047297cation

Technology 71 (1) 76ndash82

Knight R L Kadlec R H amp Ohlendorf H M The use of

treatment wetlands for petroleum industry ef 1047298uents

Environmental Science amp Technology 33 (7) 973ndash980

Korin E Ladizhensky I amp Korngold E Hydrophilic

hollow 1047297 ber membranes for water desalination by the

pervaporation method Chemical Engineering and

Processing Process Intensi 1047297cation 35 (6) 451ndash457

Korngold E Korin E amp Ladizhensky I Water desalination

by pervaporation with hollow 1047297 ber membranes Desalination

107 (2) 121ndash129

Kuila S B amp Ray S K Separation of isopropyl alcoholndash

water mixtures by pervaporation using copolymer

membrane analysis of sorption and permeation ChemicalEngineering Research and Design 91 (2) 377ndash388

Kulkarni S S Kittur A A Aralaguppi M I amp Kariduraganavar

M Y Synthesis and characterization of hybrid

membranes using poly(vinyl alcohol) and

tetraethylorthosilicate for the pervaporation separation of

waterndashisopropanol mixtures Journal of Applied Polymer

Science 94 (3) 1304ndash1315

Kuznetsov Y P Kruchinina E V Baklagina Y G Khripunov

A K amp Tulupova O A Deep desalination of water by

evaporation through polymeric membranes Russian Journal

of Applied Chemistry 80 (5) 790ndash798

Liang B Pan K Li L Giannelis E P amp Cao B

High performance hydrophilic pervaporation composite

membranes for water desalination Desalination 347

199ndash206

Lu Y amp Chen J Optimal design of multistage membrane

distillation systems for water puri1047297cation Industrial amp

Engineering Chemistry Research 50 (12) 7345ndash7354

Luyben W L Control of a columnpervaporation process

for separating the ethanolwater azeotrope Industrial amp


Pandey R P amp Shahi V K Functionalized silicandashchitosan

hybrid membrane for dehydration of ethanolwater

azeotrope effect of cross-linking on structure and

performance Journal of Membrane Science 444 116ndash126

Quintildeones-Bolantildeos E Zhou H Soundararajan R amp Otten L

Water and solute transport in pervaporation

hydrophilic membranes to reclaim contaminated water

for micro-irrigation Journal of Membrane Science 252 (1ndash2)

19ndash28

Smitha B Suhanya D Sridhar S amp Ramakrishna M

Separation of organicndashorganic mixtures by pervaporationmdasha

review Journal of Membrane Science 241 (1) 1ndash21

Swenson P Tanchuk B Gupta A An W amp Kuznicki S M

Pervaporative desalination of water using natural zeolite

membranes Desalination 285 68ndash72

Xie Z Ng D Hoang M Duong T amp Gray S Separation of

aqueous salt solution by pervaporation through hybrid

organicndashinorganic membrane effect of operating conditions

Desalination 273 (1) 220ndash225

Xie Z Hoang M Ng D Doherty C Hill A amp Gray S

Effect of heat treatment on pervaporation separation of

aqueous salt solution using hybrid PVAMATEOS

membrane Separation and Puri 1047297cation Technology 127

10ndash17

Zhu T Lin Y Luo Y Hu X Lin W Yu P amp Huang C

Preparation and characterization of TiO2-regenerated

cellulose inorganicndashpolymer hybrid membranes for

dehydration of caprolactam Carbohydrate Polymers 87 (1)901ndash909

First received 28 January 2015 accepted in revised form 19 May 2015 Available online 2 June 2015




Desalination of simulated seawater by purge-air

pervaporation using an innovative fabricated membrane

Mona Naim Mahmoud Elewa Ahmed El-Shafei and Abeer Moneer

ABSTRACT

An innovative polymeric membrane has been invented which presents a breakthrough in the 1047297eld of

desalination membranes It can desalinate simulated seawater of exceptionally high concentration to

produce a high 1047298ux of potable water with over 997 salt rejection (SR) in a once-through purge-air

pervaporation (PV) process A set-up was constructed for conducting the desalination experiments

and the effect of initial salt solution concentration (Ci) and pervaporation temperature (T pv) on the

water 1047298ux ( J ) SR separation factor and pervaporation separation index were determined The

membrane was prepared by the phase-inversion technique of a specially formulated casting solution

consisting of 1047297

ve ingredients after which the membrane was subjected to a post-treatment by whichcertain properties were conferred The results con1047297rmed that the salinity of the pervaporate was

independent of Ci (all SR above 997) The best result was at T pvfrac14 70 W

C where J varied from 597 to

345 lm2 h for C ifrac14 40ndash140 g NaCll respectively The membrane morphology was con1047297rmed to be

asymmetric The contact angle was immeasurable indicating the membrane to be super-hydrophilic

Activation energies computed using Arrhenius law were under all conditions investigated less than

20 kJmol K

Mona Naim

Chemical Engineering Department Faculty of

Engineering


Alexandria

Egypt

Mahmoud Elewa

Research Development Department

Arab Academy for Science Technology and

Maritime Transport

Alexandria

Egypt

Ahmed El-Shafei (corresponding author)

Agricultural and Biosystems Engineering Faculty

of Agriculture


Alexandria

Egypt

E-mail ahmedelsha1047297 alexuedueg

Abeer Moneer

National Institute of Oceanography and Fisheries

Alexandria

EgyptKey words | activation energy cellulose acetate desalination membranes pervaporation

INTRODUCTION

Water is a vital resource of life As access to fresh water

becomes increasingly limited in many areas of the world

the ability to desalinate seawater is expected to take on

greater signi1047297cance Recently pervaporation (PV) has

been exploited as a promising membrane separation tech-

nology which separates mixtures by preferential removal

of one component from others present in the mixture due

to its higher af 1047297nity with andor faster diffusion rate

through a non-porous membrane In the PV process

mass transfer takes place by vapour pressure difference

and the liquid mixture is maintained at atmospheric

pressure on the upstream while the permeate is removedon the other side as a vapour due to the low pressure

achieved by using either a vacuum pump or a carrier

purge gas on the downstream (Kulkarni et al ) PV

has been extensively used for separation or concentration

of mixtures of aqueousndashorganic liquids eg dehydration

of alcohols (Hu et al Kuila amp Ray Pandey amp

Shahi ) It has also been widely used in the separation

of azeotropic mixtures (Luyben ) separation of water

from organic solvent (Lu amp Chen ) removal of trace

organics from water (Knight et al ) and separation

of organic mixtures (Smitha et al ) However there

are only limited studies on the application of this technol-

ogy in water desalination (Kuznetsov et al Ben

Hamouda et al Cho et al Swenson et al )

PV of an aqueous salt solution can be regarded as separ-

ation of a pseudo-liquid mixture containing free water

molecules and bulkier hydrated ions formed by dis-

sociation of the salt in water (Kuznetsov et al )

Membranes used in previous studies on PV desalination

include sulphonated polyethylene (Korin et al ) qua-ternized polyethylene (Korngold et al )

polyetherimide and polyether ester (Quintildeones-Bolantildeos

et al ) in which 1047298uxes were very low although the

PV temperature was in the region of 40ndash82 W

C The feed

temperature was a crucial parameter due to the increase

in diffusivity and reduction in viscosity that occurs on heat-

ing However the inherent permeability of the membrane

polymer is also extremely important (Xie et al )

785 copy IWA Publishing 2015 Water Science amp Technology | 725 | 2015

doi 102166wst2015277































































































J frac14Q

A t (1)

SR frac14C i C f

C itimes 100 (2)

α frac14Y w=Y s









puted

J frac14 Ap exp Ea

RT

(5)






















matrix


























post-washing








W







T pvfrac14 70 W






C which is







temperatures



















respectively
























vacuum at 80 W








C by the




temperatures











W





























et al )




C



















liquid discharge





















concentration











from 70 to 80 W












shown in Figure 9







55932 lm2 h

Activation energy

















concentration





















CONCLUSIONS


arrived at



technique















before







C and C ifrac14









ACKNOWLEDGEMENT












REFERENCES














98 160ndash172























107 (2) 121ndash129

















199ndash206















19ndash28















10ndash17





































































































J frac14Q

A t (1)

SR frac14C i C f

C itimes 100 (2)

α frac14Y w=Y s









puted

J frac14 Ap exp Ea

RT

(5)






















matrix


























post-washing








W







T pvfrac14 70 W






C which is







temperatures



















respectively
























vacuum at 80 W








C by the




temperatures











W





























et al )




C



















liquid discharge





















concentration











from 70 to 80 W












shown in Figure 9







55932 lm2 h

Activation energy

















concentration





















CONCLUSIONS


arrived at



technique















before







C and C ifrac14









ACKNOWLEDGEMENT












REFERENCES














98 160ndash172























107 (2) 121ndash129

















199ndash206















19ndash28















10ndash17














J frac14Q

A t (1)

SR frac14C i C f

C itimes 100 (2)

α frac14Y w=Y s









puted

J frac14 Ap exp Ea

RT

(5)






















matrix


























post-washing








W







T pvfrac14 70 W






C which is







temperatures



















respectively
























vacuum at 80 W








C by the




temperatures











W





























et al )




C



















liquid discharge





















concentration











from 70 to 80 W












shown in Figure 9







55932 lm2 h

Activation energy

















concentration





















CONCLUSIONS


arrived at



technique















before







C and C ifrac14









ACKNOWLEDGEMENT












REFERENCES














98 160ndash172























107 (2) 121ndash129

















199ndash206















19ndash28















10ndash17





















post-washing








W







T pvfrac14 70 W






C which is







temperatures



















respectively
























vacuum at 80 W








C by the




temperatures











W





























et al )




C



















liquid discharge





















concentration











from 70 to 80 W












shown in Figure 9







55932 lm2 h

Activation energy

















concentration





















CONCLUSIONS


arrived at



technique















before







C and C ifrac14









ACKNOWLEDGEMENT












REFERENCES














98 160ndash172























107 (2) 121ndash129

















199ndash206















19ndash28















10ndash17























respectively
























vacuum at 80 W








C by the




temperatures











W





























et al )




C



















liquid discharge





















concentration











from 70 to 80 W












shown in Figure 9







55932 lm2 h

Activation energy

















concentration





















CONCLUSIONS


arrived at



technique















before







C and C ifrac14









ACKNOWLEDGEMENT












REFERENCES














98 160ndash172























107 (2) 121ndash129

















199ndash206















19ndash28















10ndash17















W





























et al )




C



















liquid discharge





















concentration











from 70 to 80 W












shown in Figure 9







55932 lm2 h

Activation energy

















concentration





















CONCLUSIONS


arrived at



technique















before







C and C ifrac14









ACKNOWLEDGEMENT












REFERENCES














98 160ndash172























107 (2) 121ndash129

















199ndash206















19ndash28















10ndash17
















from 70 to 80 W












shown in Figure 9







55932 lm2 h

Activation energy

















concentration





















CONCLUSIONS


arrived at



technique















before







C and C ifrac14









ACKNOWLEDGEMENT












REFERENCES














98 160ndash172























107 (2) 121ndash129

















199ndash206















19ndash28















10ndash17

























CONCLUSIONS


arrived at



technique















before







C and C ifrac14









ACKNOWLEDGEMENT












REFERENCES














98 160ndash172























107 (2) 121ndash129

















199ndash206















19ndash28















10ndash17












REFERENCES














98 160ndash172























107 (2) 121ndash129

















199ndash206















19ndash28















10ndash17







Documents

Desalination_of_Simulated_Seawater_by_Pu.pdf