Effect of Silica on the Properties of Cellulose Acetatepolyethylene

8/10/2019 Effect of Silica on the Properties of Cellulose Acetatepolyethylene

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D e s a lin a tio n 3 55 (2 0 1 5) 110

Contents listsavailable at S cien ceDirect

Desalination

journa l homepage: w wwels evi erco m! locate! "esa l

#$$ect o$ silica on the properties o$ cellulose acetate!pol%eth%lene

gl%col membranes $or reverse osmosis

&"nan &hma"a''Si"ra ahee"

a'Shaha"*a+soo" ,han

a'Saba" e-.ul

a'*uhamma" Sha/+

a' *uhamma" aroo+

b',hairu""inSanaullah

c' ahir 2amil

a

aDepartment o$ ol%mer #ngineering an" 1echnolog%'4niversit% o$ the unjab'uai"-e-&am Campus' 6ahore 57580'a9istan

bnstitute o$ Chemical#ngineering an" echnolog%' 4niversit% o$ the unjab' uai"-e-&am Campus'6ahore 57580'a9istan

cDepartment o$ Chemical#ngineering an" #nerg% Sustainabilit%'4niversit% *ala%sia Sarawa9'87300 ,otaSamarahan'Sarawa9'*ala%sia

; . ; 6 . ; S

2-stage phase inversion protocol< involving S an" controlle" evaporation

Silica is use" as an a""itive to augment permeation per$ormance

&""ition o$ silica enhance" the $ouling resistance remar9abl%

=ptimum loa"ing o$ silica particle is re+uire" $or ma>imumper$ormance

a rt i c l e i n $o

&rticle histor%:

?eceive" 23 ul% 2017

?eceive" in revise" $orm 2 =ctober

2017

&ccepte" @ =ctober 2017

&vailable online >>>>

,e%wor"s: ?everse

osmosis

ol%eth%lene

gl%col Cellulose

acetate Silica

hase inversion

a b s t ra c t

n this wor9' a series o$ cellulose acetate!pol%eth%lene gl%col-@00 membranes' with var%ing ratios were

prepare" b% 2-stage phase inversion protocol he permeation properties were stu"ie" b% subjecting

membranes in in"ig- enousl% $abricate" reverse osmosis plant &$ter optimiation o$ "i$$erent C&!#. ratios'

the membrane with highest salt rejection capacit% was selecte" an" mo"i/e" with var%ing amount o$ silica

he *o"i/e" membranes were characterie" $or their permeation properties' h%"rophilicit%' compositionalanal%sis' thermal stabilit%' mechanical strength an" morphological stu"ies Silica signi/cantl% inAuence" the

permeation per$ormance o$ composite membranehe Au> enhance" $rom 035 to 27@ 6!h m2

along with an

1171B relative increase in salt rejection he h%"rophilicit% was signi/cantl% enhance" b% the a""ition o$

silica n 01:? spectra' the broa"ening o$ thepea9 aroun" 3500 cmC1

an" emergence o$pea9 at 850 cmC1

speci/e" the incorporation o$ silica particles he thermal anal%sis in"icate" the relative increase in

"egra"ation temperature (ma>) an" glass transition temperature (g) $or CS-5 membrane he

mechanical stabilit% o$ the mo"i/e" membranes' increase" initiall%' but "ecline" with $urther a""ition o$

silica he results in"icate" that the incorporation o$ Si=2 content in the casting solution improve" the $ouling

resistance o$ the membranes

2017 #lsevier EF &ll rights reserve"

1 ntro"uction

*embranes an" membrane processes subsist as ol" as li$e G17H?ecentl%' s%nthetic membrane processes have appeare" among the

most innovative technologies to attain a variet% o$ goals ranging

$rom molecular separation to concentration o$ pro"ucts G5H he

intrinsic characteristics o$ membranes li9e high e$/cienc%' simplicit%'

selectivit%' low energ% consumption an" goo" stabilit% ma9e

membranes as an integral part o$ various chemical in"ustries G@'IH

*embrane base" "esalination processes involve reverse osmosis

(?=)' electro "ial%sis' $orwar" osmosis' ultra/ltration an"

nano/ltration GJ'8H he ?= process was commercialie" in 18I0

an" to"a% it is a

Correspon"ing author el: K82 321@IJ8I82 (Cell)

#-mail a""ress: a" nan ah me "b aloc hL gm ailcom (& &hma")

lea"ing membrane technolog% representing J0B o$ total "esalination

plants G1012H

&n i"eal ?= membrane shoul" possess the resistance to chemical

attac9' e>cellent separation per$ormance' goo" mechanical an"

thermal stabilit% G13H he per$ormance o$ a membrane is notabl%

inAuence"b% its constituents' which a$$ect man% properties G17'15H

Farious pol%mers have been use" to s%nthesie membranes' but

cellulose acetate (C&) membranes are well accepte" "ue to their goo"

transport characteristics' low protein a"sorption' e>cellent water

a$/nit%' appropriate mechanical strength' e>cellent /lm-$orming

properties an" lower cost G1@'1IH ;owever' C& has poor thermal

stabilit%' lower chemical resistance' in$erior mechanical strength an"

vulnerable to $ouling resistance here$ore' at- tempts have been

ma"e to improve the per$ormance o$ C&b% "eveloping h%bri" organic

inorganic membranes ew researchers have investigat- e" the e$$ect

o$ alumina (&l2=3)' irconia (Mr=2)' titania (i=2)'silver

h ttp :!!" >" oio rg !1 010 1 @!j" e s al2 0 1 71 0 0 0 7

0011-81@7! 2017 #lsevier EF &ll rights reserve"
http://dx.doi.org/10.1016/j.desal.2014.10.004http://dx.doi.org/10.1016/j.desal.2014.10.004http://dx.doi.org/10.1016/j.desal.2014.10.004http://www.sciencedirect.com/science/journal/00119164http://www.sciencedirect.com/science/journal/00119164http://www.sciencedirect.com/science/journal/00119164http://www.sciencedirect.com/science/journal/00119164http://www.sciencedirect.com/science/journal/00119164http://www.sciencedirect.com/science/journal/00119164http://www.sciencedirect.com/science/journal/00119164http://www.sciencedirect.com/science/journal/00119164http://www.elsevier.com/locate/desalhttp://www.elsevier.com/locate/desalhttp://www.elsevier.com/locate/desalhttp://www.elsevier.com/locate/desalhttp://www.elsevier.com/locate/desalmailto:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]://dx.doi.org/10.1016/j.desal.2014.10.004http://dx.doi.org/10.1016/j.desal.2014.10.004http://dx.doi.org/10.1016/j.desal.2014.10.004http://dx.doi.org/10.1016/j.desal.2014.10.004http://dx.doi.org/10.1016/j.desal.2014.10.004http://dx.doi.org/10.1016/j.desal.2014.10.004http://dx.doi.org/10.1016/j.desal.2014.10.004http://dx.doi.org/10.1016/j.desal.2014.10.004http://dx.doi.org/10.1016/j.desal.2014.10.004http://dx.doi.org/10.1016/j.desal.2014.10.004http://dx.doi.org/10.1016/j.desal.2014.10.004http://dx.doi.org/10.1016/j.desal.2014.10.004http://dx.doi.org/10.1016/j.desal.2014.10.004http://dx.doi.org/10.1016/j.desal.2014.10.004http://dx.doi.org/10.1016/j.desal.2014.10.004http://dx.doi.org/10.1016/j.desal.2014.10.004http://dx.doi.org/10.1016/j.desal.2014.10.004http://www.sciencedirect.com/science/journal/00119164http://www.elsevier.com/locate/desalhttp://www.elsevier.com/locate/desalmailto:[email protected]://dx.doi.org/10.1016/j.desal.2014.10.004http://dx.doi.org/10.1016/j.desal.2014.10.004


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2 & &hma" et al ! Desalination 355 (2015) 1N

*embrane

t%pe

ater

content

(B)

lu>

(6!h m2)

Salt rejection

(B)

*embrane

permeabilit%

(O10C7

6!h m2

9a)

C&!#.-1 @150 0JI 5200 2I0

C&!#.-2 5JI0 0I0 @000 250

C&!#.-3 5385 07@ @820 200

C&!#.-7 5111 035 J150 1@J

(Control)

ig 1 & schematic o$ reverse osmosis rig

an" silica (Si=2) particles in various pol%meric materials G1J20Hhe

re- sultant h%bri" membranes have been reporte" to increase the

Au> an" mechanical strength' upon increasing the concentration o$

inorganic particles G21'22H Si=2 particles have attracte" particular

attention owing to their special properties li9e small sie' thermal

resistance' /ne suspen- sion $ormation in a+ueous solution' strong

sur$ace energ% an" relativel% inert material

ol%meric ?= membranes are s%nthesie" through phase

inversion protocol t is the most versatile techni+ue to obtain a

variet% o$ mor- phologies ranging $rom micro/ltration membranes

with ver% porous structures' to more "ense reverse osmosismembranes G23H he concept

able 1

#$$ect o$ concentration o$ C&!#. on water content' Au>' salt rejection an" membrane

permeabilit%

o$ phase inversion involves an arra% o$ "i$$erent metho"s such as

"i$$usion-in"uce" phase separation' vapor-phase precipitation'phase

inversion b% controlle" evaporation an" thermal-in"uce" phase

separation (1:S) G27H &ll the metho"s involve comple> multi-

component

ig 2 ?elationshipbetween pressure an" Au>


3/15

mass trans$er e>cept thermal-in"uce" phase separation which

primari- l% "epen"s on heat trans$er G25H

n this paper' a "etaile" stu"% towar"s the s%nthesis o$ thermo-

able 2

#$$ect o$ "i$$erent concentration o$ silica on water content 'Au>' salt rejection an"

membr ane perme abilit%

mechanicall% en"urable membranes is reporte"hese membranes

were prepare"b% using cellulose acetate'pol%eth%lene gl%col an"

silica

*embrane

t%pe

ater

content (B)

lu>

(6!h m2)

Salt rejection (B) *embrane permeabilit%

(O10C7

6!h m2

9a)

& 2-stage phase-inversion protocol was "evise" involving thermall%-

in"uce" phase inversion $ollowe"b% a controlle" evaporation proce-

"ure he chemical alteration' thermal stabilit%' mechanical strengthan" morphological structure o$ membranes were characterie" b%

attenuate" total reAectance-ourier trans$orm in$rare" spectroscop%

(&?-?)' thermogravimetric anal%sis (.&)' "i$$erential scanning

calorimetr% (DSC)' ultimate tensile strength an" scanning electron

microscop% (S#*) respectivel% he e$$ects o$ a""ition o$ Si=2

particles on the membrane properties were investigate" b%

e>amining thepermeation per$ormance' such as pure water Au> an"

solute rejection e reporte" here that the incorporation o$ silica

particles simultaneousl% improves the selectivit% an" permeabilit% o$

membranes

2 *aterials an"

metho"s

Cellulose acetate (C&' *w 30'000 an" acet%l content 38B)'

pol%eth%l- ene gl%col-@00 (#.) an" acetone were supplie" b% ED;

laboratories supplies' oole' #nglan" Silica (Si=2) was purchase"

$rom Sigma &l"rich (#nglan") &ll chemicals an" solvents o$

anal%tical gra"e were use" as receive"

21 reparation o$ "ope"solutions

10 g o$ C& was "issolve" in J0 m6o$ acetone with constant stirringat

J0 PC $or 2 h o this homogenous solution' 10 g o$ #. was a""e"

with regular stirring at J0 PC $or @ h he viscous an" clear solutionwas obtaine"' which was terme" as a blen"e" "ope" Solution'

C&!#.-1 G2@H he "i$$erent ratios o$ C&!#. (12!J' 17!@ an" 1@!7

g!g) were use" to prepare three a""itional "ope" solutions'labele"

as C&!#.-2' C&!#.-3 an" C&!#.-7 respectivel% he casting

solutions were allowe" to cool "own to room temperature (25 PC)

an" were 9ept $or

27 h in a seale" Aas9 to remove micro bubbles $orme" in thesolution

CS-1 5J11 12J J300 31J

CS-2 @@I1 178 J550 350

CS-3 I533 1I8 J850 705

CS-7 J033 208 8200 783

CS-5 J22I 27@ 8000 532

3 Characteriation

31 *embrane per$ormance

311 #>perimental set up o$ ?= rig

he permeation e>periments were carrie" out in the ?=

e>perimental rig using a plate an" $rame membrane mo"ule &

schematic o$process Aow "iagram $or aplate an" $rame membrane

mo"ule is shown in ig 1 t consiste" o$ the $ee" tan9 o$ 10 6

capacit% he temperature o$ the $ee" solution was in"icate" an"

controlle" b% a thermocouple an" controller setup he $ee" was

circulate" using a circulationpump with a ma> power rating o$ 1 9

at a ma> $ee" rate o$ 2500 6!min he e$$ective membrane area in

contact with the $ee" was 001J m2 hepermeate was collecte" $rom

the sample points provi"e" a$ter the membrane mo"ule & saline

solution (QaCl solution) having a con"uctance o$ 20 milli-siemens

(mS) an" a concentration o$ 10 g!6 was sub- jecte" to the $ee" tan9

#ach membrane was compacte" with "istille" water at I00 9a $or 5

h till it attains stea"% state ee" temperature was 9ept at 30 PC

"uring the operation

312 ater content

he abilit% o$ membranes to absorb water was "etermine" a$ter

soa9ing membranes in water $or 27 h an" weighing a$terwar"she

wet membranes were then place" in a vacuum "r%er at I5 PC $or 7Jh an" the weights o$ the "r% membranes were recor"e" G28H he

water content'absorbe" b% the membranes'was "etermine" b% the

$ollowing relation'

wCD22 Casting o$ membranes ater content RBS T U100 R1S

D

he "ope" solution was sprea" slowl% on glass plate b%

maintaining uni$orm thic9ness with the help o$ micrometer a"justable/lm applicator (?e$: 111I!300 Sheen instruments) he temperature

o$ caste" mem-branes was lowere" imme"iatel% to 0 PC $or 15 min

to in"uce (S) he S causes the $ormation o$ "ense an"

as%mmetric structure t was $ollowe" b% precipitation un"er

controlle" evaporation b% increasing temperature up to @0 PC G2IH

he s9inne" membranes' thus $orme" G2JH were care$ull% remove"

$rom the glass plates b% using a sharp 9ni$e he thic9ness o$ the

resulting membranes was measure" an" was $oun" in the range o$

50200 microns hese membranes were test- e" on the basis o$ their

permeation per$ormance an" the best per$orming C&!#.-7 (control)

membrane was selecte" $or $urther mo"i/cation with silicaparticles

23 *o"i/cation o$ "ope" solutions

Silica (15B' w!v) was "isperse" in al9aline solution (10 m6)

be$ore a""ing to the C&!#.-7blen"e" "ope solution with constant

stirring $or 2 h at J0 PC he membranes (CS-1CS-5) were caste"

an" "rie" $ollowing the same proce"ure as mentione" in Section

22 Control an" mo"i/e" membranes were transparent' Ae>ible an"clear with smooth sur$ace


4/15

where w is wet sample weight an" D is "r% sample weight

ig 3 lu> o$ control an" mo"i/e" membranes over time


5/15

p

ig 7 Droplet images on control an" mo"i/e"membranes

313 ermeate Au> ()

he permeate Au> () represents the amount o$ pure water

collecte" per unit time an" per unit area at variable pressures t wascalculate" b% G30H:

317 Salt rejection

n reverse osmosis' the solute or salt rejection is "e/ne" as the

ratio o$ the concentration "i$$erence across the membrane an"

e>presse" as G31H'

2 T Vt & R2S?RBST 1C VC

> 100 R3S

where 2 is the permeate Au> (6!h m2)' is the amount o$permeate

(6)'t is the time (h) an" & is the membrane area (m2)

where ? is the salt rejection (B)' Cppermeate an" $ee" respectivel%

an" C$ are the con"uctance o$

ig 5 Contact angle o$ control an" mo"i/e" membranes ig @ ? spectra o$ control an" mo"i/e" membranes


6/15

*embrane

%pe

1min

(PC)

1ma>

(PC)

eight loss

at 1ma> (B)

?esi"ue at

en" (B)

Control 2I0 700 JIJ5 1CS-1 300 7@0 J818 5@J

CS-2 330 7J0 J817 5I7

CS-3 370 500 J817 5J0

CS-7 350 510 J817 582

CS-5 3@0 520 J817 @I2

ig I .& curves o$ control an" mo"i/e" membranesig J Derivative weight loss o$ control an" mo"i/e" membranes

35 hermal anal%sis

32 *embrane

permeabilit%

*embrane permeabilit% in"icates the tolerance o$ membrane

towar"s h%"raulic pressure o "etermine m' the Au> was measure"

at "i$$erent trans membrane pressures (W) he pressure "uring the

operation was increase" $rom 750 to J00 9a he permeabilit% o$

the membrane was evaluate" $rom the slope obtaine" b% plotting

permeate Au> versus membrane pressure "i$$erence (W)'using #+

(7)

2m T

WR7S

where m is the membrane h%"raulic permeabilit% G6 hC

mC 2

!9aH

an"W is a pressure "i$$erence(9a)

33 Contact anglemeasurement

he contact angles were measure" b% a Drop Shape &nal%er

(DS&

30' ,?4SS .erman%) through sessile "rop metho" & "angling

"roplet o$ 5 X6 o$ "eionie" water was "roppe" care$ull% $rom -

shape" micro- s%ringe to membrane sur$ace he contact angles

were calculate" b% the so$tware #ach contact angle was measure" at

ten "i$$erent points o$ each membrane an" an average value was

calculate" G32H

37 ourier rans$orm in$rare" spectroscop%(1:?)

01:? o$ membranes was scanne" b% using a Shima"u:? restige-

21 e+uippe" with ;oriontal &ttenuate" otal ?eAectance (;&1?)

acces- sor% he e>periments were run with air as the bac9groun"

or each spectrum 100 scans were accumulate" with a resolution o$ 7

cmC1

able 3

1hermal Stabilit% o$ control an" mo"i/e"membranes

Di$$erential scanning calorimetr%!thermal "egra"ation

measurements o$ the membrane samples were per$orme" using 1&

instruments SD- @00 thermo gravimetric anal%er at a heating rate

o$ 10 PC!min an" temperature programs $or DSC were run $rom 30 PC

to J00 PC he ther- mograms $or 1.& were obtaine" using a c%cle o$

heating $rom an ambient temperature to J00 PCQitrogen Aow was

maintaine" at 15 m6!min in or"er to remove all corrosive gas

involve" in the "egra"ation

3@ *echanical stabilit%

ensile testing o$ membranes was per$orme" at room

temperature using an :nstron-t%pe tensile testing machine

(1estometric!*350-10C1 ?=C;D&6#' #nglan")with a crosshea" spee"

o$ 3 mm!min he sample wi"th was 25 mm an" the length between

the jaws was 75 mm he measurements were per$orme" at 25 PC an"25 Y 2Brelative humi"it%

3I Scanning electron microscop% (S#*)

Scanning electron microscop% was per$orme" on eol S*-@7J0

1he membranes were cut into small pieces an" place" on stub an"

9ept in a speci/c chamber in a vacuum he electron beams were

sputtere" on sample an" images o$ membranes on var%ing resolutions

were observe"

ig 8 DSC curves o$ the control an" mo"i/e" membranes


7/15

silica amount he relative increase in water content is 3IJJB he *embrane t%pe S (*pa) #b (B) Containcrease" water content ma% be "ue to the increase in membrane h%"ro-

Control 2@387 5J 5721hilicit since the hi h h "ro hilicit $acilitates the "i$$usion o$ water

molecule into the membrane Similarl%' the Au> o$ all mo"i/e" mem- CS-2 35555 JI3 7011

branes also increase" with the increase in silica content CS-5 membrane CS-3 717@7 113@ 3718

has hi hest Au> o$ 27@ 6!h m2Similar results have been obtaine"b Zin CS-7 73I2J 1223 2J@8

7 ?esults an" "iscussions

71 *embrane per$ormance

he Au> o$ all "ope" an" compacte" membranes was calculate" at

a pressure o$ @50 9a $or I h he water content' Au> an" salt

rejection were measure" b% using #+s (1)' (2) an" (3) respectivel%

he water content' water Au>' salt rejection an" membrane

permeabilit% are represente" in able 1 C&!#.-1 membraneshowe" a ma>imum Au> o$ 0JI 6!h m

2while it e>hibite" minimum

salt rejection capacit% o$

52BC&!#.-7 membrane ha" J15B salt rejection an" its Au> was

035 6!h m2

he C&!#.-1 membrane' with the highest water content an"

Au>' showe" re"uction in salt rejection capacit% while C&!#.-7

membrane with the lowest water content an" Au>' ha" an elevate"

salt rejection capacit% as in"icate" in able 1 t was observe" that

with the increase" content o$ cellulose acetate' the water content'

Au> an" membrane permeabi lit% was "ecrease" while the salt

rejection capacit% was increase" remar9abl%

he transport mechanism within membrane can best be

e>plaine" on the basis o$ the solution "i$$usion mo"el &ccor"ing to

thismo"el' transport'

process within

themembrane involves three

steps: sorption at the sur$ace o$ the membrane'"i$$usion into "ense

membrane un"er pressure an" then "esorption he h%"rophilic

nature o$ #. acte" as "riving $orce $or sorption o$ water into

membrane G333@H 1he "ecrease in water content was attribute" to

the "ecrease in h%"rophilic #. content

t was "e"uce" pragmaticall% that salt rejection was inversel%

relate" to salt passage Cellulose acetate being "esalting in nature was

responsi- ble $or the removal o$ salt G3IH his was a reason that

C&!#.-7 ha" ma>imum salt rejection abilit% hen salt rejection

e$/cienc% o$ mem-brane was at its best' at the same time Au> was

re"uce"' "epen"ing upon the var%ing amount o$ C& an" #.

#. is h%"rophilic in nature an" acts as pore $ormer G3JH C&!#.-

1 membrane' with ma>imum +uantit% o$ #.' showe" increase in

water Au>' but at the same time salt rejection was compromise" his

might be attribute" to the $ormation o$ macro voi"s G38H onmembrane which allowe" the passage o$ salt along with water

*oreover' the "i$$usion rate o$ water was accelerate" b% the

presence o$ #. "ue to its h%"rophilic nature #. increase" the

ten"enc% o$ pore $ormation an" as a conse+uence Au> was increase"

t was observe" that within the pressure range o$ 750 to @50 9a'

the Au> "ecrease" linearl% with increase in trans membrane

pressure as in"icate" in ig 2 hese results are in agreement with

the reporte" "ata G70H

he "ecline o$ Au> with the passage o$ time' even at high pressure

was attribute" to the compaction phenomena occurring on the

membrane sur$ace he compaction o$ membrane un"er pressure

involve" rearrangement o$pol%meric chains which le" to the change

in membrane structure with low value porosit% which conse+uentl%

"ecrease" the Au> Similar results were obtaine" b%&rthanareeswaranet al G3JH

=n the basis o$ salt rejection an" Au>' C&!#.-7 membrane was

selecte" $or mo"i/cation with silica &$ter mo"i/cation these

membranes were characterie" an" compare" with C&!#.-7

(control) he water content' Au>' salt rejection an" membrane

permeabilit% o$ mo"i/e" membranes are given in able 2

he water content o$ the membrane was relate" to the

h%"rophilicit% o$ the membrane able 2 in"icates that the water

content an" membrane permeabilit% o$ mo"i/e" membrane

increase" with increase in

ig 10 1ensilestress an" elongation-at-brea9 o$ control an" mo"i/e" membrane

that a""ition o$ silica nanoparticles increases the Au> G71H he

embe"- "ing o$ silica particles in C&!#. membrane can also "isrupt

the pol%mer chain pac9ing b% creating microporous "e$ects between

inorganic particle an" pol%mer inter$ace he salt rejection increase"

$rom J15B to 82B $or CS-7 membrane as a result o$ incorporation o$

silica particles G72H ;owever' a slight "ecrease was observe" at

highest silica loa"ing (5B w!v) his result can be attribute" to the

agglomeration o$ silica particles in certain locations which a$$ect the

solute rejection

711 &nal%sis o$ membrane $ouling "uringpermeation

norganic compoun"s can be a"sorbe" an"!or "eposite" on the

membrane sur$ace' causing membrane $ouling which in turn re"uce

the Au> "rasticall%ouling increases energ% consumption an" results

in high operating cost G72H ig 3 shows the permeation Au> o$

control an" mo"i/e" membranes t is attention-grabbing that Au> $or

the control "ecline" with the passage o$ time an" attain a stea"%state' whereas $or the mo"i/e" membranes' the Au> increase"

remar9abl% with the increase o$ Si=2 content he increase in

permeation Au> was "ue to the increase in sur$ace h%"rophilicit%

which was ren"ere" b% Si=2 particles Similar observations were

ma"e $or C&!Si=2blen" membranes $or ultra/ltration application G28H

72 *embrane h%"raulic permeabilit%

(m)

*embrane h%"raulic permeabilit% is an intrinsic resistance o$ the

membrane t was "etermine" b% subjecting the membranes to

various pressures (750' 500' 550' @00' @50' I00' I50 an" J00 9a) an"

the m value was calculate" $rom the slope o$ the linear relationship

betweenpressures versus Au>he permeabilit% o$ unmo"i/e" membranes is given in able 1

1he presence o$ #. ha" consi"erable e$$ect on the h%"raulic

permeabilit% hus' when the #. concentration was "ecrease"

$rom 10 to 7 gm in the "ope solution' there was a correspon"ing

"ecrease in h%"raulic permeabilit% $rom 2I0 to 1@J (O10C7

6!h m2

9a) t might be attribute" to the "isappearance o$pores which were

$orme"b% #. *oreparticularl%'

able 7

*echanical properties an" contact angle o$ control an" mo"i/e"membranes

ct angle [ ("eg)


8/15

et al $or silica incorporation inpol%ami"e membranes' whichreveale"

CS-5 3J27@ 1033 2710


9/15

C&!#.-1 membrane with the highest #. contents o$$ere" greatest

permeabilit% his result was in agreement with that o$ Au> obtaine"

through permeation e>periment

he m values $or the mo"i/e" membranes are given in able 2'

showing an increase with the increasing amount o$ silica $rom 1 to

5B w!v or the mo"i/e" membranes' the permeabilit% increase"

$rom

12J to 27@ (O 10C 7

6!h m2

9a) he increase in permeabilit%

resulte"in an increase in permeate Au> as in"icate" in able 2 t was mainl%

"ue to increase in membrane h%"rophilicit% with the incorporation

o$ silica particles which e>pe"ites "i$$usion an" solubiliation o$

membranes

73 Contact angle

he contact angle is an important parameter $or measuring

sur$ace h%"rophilicit% n general' a smaller contact angle

correspon"s to a more h%"rophilic material ig 7 represents "igital

image o$ a li+ui" "roplet on a "r% sur$ace o$ all membranes in which

the contact angle ([) is measure" accor"ing to the sessile "rop

metho" t is evi"ent $rom ig 5 that there is "ecrease in contact

angle b% increasing silica particle concentration hese results

"emonstrate" that silica particle can improve h%"rophilicit% o$

membrane he less h%"rophilic sur$ace shows larger contact angle

with the sur$ace an" vice versa

77 01:? anal%sis

Spectroscopic metho"s pla% a crucial role in pol%mer

characteriation he use o$ metho"s such as in$rare" spectroscop%

is essential in or"er to investigate molecular structure o$ membranes

01:? spectrums o$ the control an" mo"i/e" membranes are given in

ig @

n case o$ control'pea9 at 37@8 cmC1

represente" stretching o$

=\;' 2JII cmC 1 showe" stretching o$ C\; bon"' 1I38 cm

C 1

"epicte" the strongpea9 $or C]=o$ carbon%ls'1733 cmC1

in"icate"

ben"ing o$ C\; $ollowe" b% pea9s at 13@8 cmC 1

an" 1227 cmC 1

which "escribe" roc9ing an" wagging mo"e o$ C\; bon" he

strongest pea9 at

1035 cmC1

speci/e" C\=\Cwhilepea9 at 1112 cmC1

an" 807 cmC

1

illustrate" the presence o$ sacchari"e Similar results ha" been previ-

ousl% reporte" in the literature G73'77H he emergence o$ new pea9

aroun" 850 cmC1

in the spectra o$ all mo"i/e" membranes coul" be

attribute" to stretching vibration o$ Si\=\ he broa"ening o$pea9

aroun" 32003@50 cmC 1

was "ue to ;-bon"e" Si\=; G75H he

broa"- ening an" emergence o$ new pea9 in the spectra o$ mo"i/e"

membranes con$orm the impregnation o$ silica particles within the

membrane matri>

75 hermal anal%sis

he thermal "ecomposition is e>presse" in terms o$ weight loss as

a $unction o$ the temperature $or the control an" mo"i/e"

membranes as shown in ig I #ach 1.& curve shows three main

"egra"ation steps he /rst step too9 place between 30 PC an" 250

PC an" "ispla%e" about 35B o$ weight loss his "egra"ation was

associate" with the vol- atiliation o$ the volatile matter an"!or the

evaporation o$ resi"ual absorbe" water he secon" stage o$"egra"ation starte" $rom 2@0 PC an" continue" up to 700 PC here

was JIJ5B weight loss occurring in secon" stage "ue to

"egra"ation o$ cellulose acetate chain he temperature at which

ma>imum "egra"ation occurs (ma>) is 700 PC Similar results were

observe" b% &rthanareeswaran et al G7@H 1he thir" step' starte" at

700 PC s%mbolie" the carboniation o$ "egra"e" pro"ucts to ash

t was observe" that the temperature at which "egra"ation

initiate" (min) is relativel% higher $or all the mo"i/e" membranes as

in"icate" in able 3 Similarl%' 1ma> $or all the membranes shi$te"

towar"s higher temperature (700 PC to 520 PC)' with increasing

amount o$ silica he substantial increase in thermal stabilit% was "ue

to the incorporation o$ silica within the matri> o$ cellulose acetate or

all the mo"i/e" membranes' when the temperature e>cee"e"

higher than 550 PC' the mass remaine" almost constant' whichshowe" that the resi"ue was mostl% metal o>i"e G7IH whereas in case

o$ control sample 1Bresi"ue in"icates the presence o$ carbon ash

he /rst "erivative o$ the mass-change with respect to time

("m!"t' calle" "erivative thermogravimetr% (D.)) was calculate"

an" plotte" as a $unction o$ temperature (0ig J) 4sing D.

anal%sis' a series o$ pea9s were obtaine" instea" o$ stepwise .

curves he areas un"er the pea9s were proportional to the total

mass-change o$ the membrane sample he D1. is more precise in

showing the onset o$ a reaction that is accompanie" b% mass loss an"

also permits the reaction temperatures to be "e/ne" more precisel%

he D.pea9s are associate" with the onset o$ the secon" stage o$

"ecomposition hese pea9s shi$te" towar"s higher temperature'

which in"icates an increase in stabilit% o$ mo"i/e" membranes

7@ DSC stu"ies

n a DSC anal%sis' the glass transition temperature (g) is an

in"ica- tive o$ the structure an" pac9ing o$ the pol%mer chain in the

membrane & lower glass transition temperature (g) in"icate" that

the membrane possesse" more $ree volume an" there$ore a loose

structure G73H he DSC thermogram o$ control an" mo"i/e"

membranes are given in ig 8 t was observe" that the control

e>hibite" a 1g at @0 PC t was


10/15

ig 11 S#* images o$ control (a) top sur$ace an" cross-section (b)


11/15

interesting to note that 1g o$ mo"i/e" membranes'increase" $rom @5

to

J0 PC CS-7 membranes reveale" 1g o$ J0 PC he increase in 1g was

"ue to the inclusion o$ silica within C&!#. membrane Similar

results were suggeste"b%Qunes et al G7JH he increase in 1gresulte"

in higher pac9ing "ensit% an" rigi"it% hese results were in

agreement with the mechanical properties o$ membranes

7I *echanicalstabilit%

n or"er to investigate the e$$ect o$ silica on mechanical properties

o$ membranes' the tensile stress (S) an" elongation-at-brea9 (#b) o$

control an" mo"i/e" membranes were measure" an" shown in ig

10 :t was noteworth% that the elongation-at-brea9'tensile stress an"

Zoung s mo"ulus initiall% increase" with the a""ition o$ Si=2

particles an" reache" at pea9 when the Si=2particle concentration

was 7B (w!v) an" then "ecline" as the Si=2 particle

concentration was $urther increase" Zan et al ma"e similar

observations $or &l2=3!FD0blen" $or

4 membrane he initial increase ma% be "ue to increase in

interaction between the silica particles an" pol%mers ;owever' an

e>cessive concentration ma% cause the aggregation o$ particles an"

prevent it to "isperse uni$orml% in a pol%meric matri> he large

phase separation results in the "ecline o$ mechanical stabilit% o$ the

membrane G78H hese behav- iors in"icate that an appropriate

amount o$ Si=2 particles in C&!#.-7 solution can improve the

mechanical properties o$ the membrane

he salt rejection an" mechanical behavior o$ mo"i/e"

membranes showe" i"entical pattern ie with increasing silica

particles there was increase" in salt rejection in a""ition to

mechanical strength Eut at ma>imum loa"ing o$ silica particles'

there was "ecline in salt rejection as well as mechanical behavior as

shown in ables 2 an" 7

7J S#* anal%sis

o attain high per$ormance membranes $or speci/c applications'it

is essential to manipulate the morphological structures o$ the

membranes


12/15


13/15

here$ore' the morphological stu"ies o$ various sections o$ control

an" sur$ace mo"i/e" membranes were ma"e b% using scanning

electron microscope he scanning electron micrographs o$ C&!#.

blen" membrane are shown in ig 11 t reAects the "ense

as%mmetric composite structure' with top' s9inne"-la%er an" sub-

la%er

ig 12 (a$) represents the images o$ mo"i/e" membranes with

"i$$erent silica loa"ings &ccor"ing to S#* images' the sur$ace

morphol- ogies o$ the membranes were change" signi/cantl% with thea""ition o$ silica particles he top sur$ace morpholog% is shown on

ig 12(a) t was observe" that micro-sie silica particle (051 Xm)

were "istribute" in the membrane he interaction o$ silica

particles with pol %mer "isrupts the mobilit% o$ pol%meric chains

resulting in the $ormation o$ macroscopic "e$ects G28H Eut as

concentration increase" the "e$ects were /lle" with silica aggregates

as observe" in ig 12($)

5 Conclusions

n this stu"%' thermo-mechanicall% stable membranes were

s%nthesie" through a 2-stage phase inversion metho"& series o$

C&!#. blen"e" membranes showe" a change in Au> an"

permeabilit% with change in ratio o$ #. an" C& he membranewith optimum Au> an" salt rejection was selecte" $or mo"i/cation

with silica he mo"i/e" membranes resulte" into an improve"

tren" in the salt rejection an" permeation properties CS-7 ha" 82B

salt rejection which provi"e" almost 11B increase in salt rejection

capacit% compare" with the control membrane (J15B) he

mechanical stabilit% o$ the mo"i/e" mem-branes'increase" $rom 1

to 7B (w!v) o$ silica loa"ing urther increase in Si=2particles in the

casting solution resulte" in the "ecrease o$ tensile strength an"

elongation at brea9 Similarl%' 1ma> an" 1g o$ all mo"i/e" membranes

remar9abl% increase" as evi"ent $rom 1.& an" DSC anal%sis he S#*

images reveale" incorporation o$ silica particles within the

as%mmetric composite membrane he improve" h%"rophilicit% o$

the composite membrane also enhance" $ouling resistance his

stu"% showe" a critical nee" $or optimiing the silica particleloa"ing' as overloa"ing o$ silica ma% not be a"vantageous $or ?=

per$ormance an" has negative impact on the ?= membrane

properties

&c9nowle"gments

he authors e>press their cor"ial gratitu"e to the team o$

Department o$ ol%mer #ngineering an" echnolog%' 4niversit% o$ the

unjab' $or their co-operation "uring the e>ecution o$ this research

projecthe authors are also than9$ul to the 4niversit% o$ *ala%sia

Sarawa9 (4Q:*&S)' which supporte" this wor9 through grant D

G.rant re$ no 02 (D23)!

888!2013(0@)H

?e$erences

G1H 6an g ' 2 Shen ' Z Mhan g ' Z Z u ' Z . u o ' C 6i u ' r ep arat i o n an " charac teriations

o $ charge " p ol% ( vin%l but% r al ) h o l lo w / be r u ltra / l t ra t io n m e mb r ane s w i th

p e r A u oros ul $o n i c a c i " a s a" "iti ve ' 2 *emb rS c i 73 0 (20 1 3 ) 110

G2H ; Str athmann ' 6 . l o m o ' # D r ioli' & n nt r o " uctio n t o * e mbran e S c ien c e an"

e c hno l o g% ' Co nsi glioQ a i o n a l e D e l l e ?i ch e r c h e ' ta l% ' 2 00@

G3H . e nte n'* em b rS c i e c h n o l 27 (20 0 2 ) 1 00 81 0 2 7

G7H S S eja l' ? De s ai ' o l% m er mem b ra n e te c hn olog%' n t #n g Sc i nn o v e c hn o l

2 (2 01 3) 7 0 07 03

G5H ; Stra thmann ' *embran e sep a rat i o nprocesses : curren t r elevanc e an " $uture

opp ortu n i ti es ' &Ch # 2 7 I (2001 ) 10II10JI

G@H ; S tra th m a n n' * e mb ra ne s ep a ra tio n p ro ce s s es' * e mb r S c i 8 (18 J 1 ) 1 2 1

1 J8

GIH ; St rath m an n' *em b ran e s an" mem b ra n e sep ara tion pro c ess e s' 1' r incip les'in

4 llma n n s # n c % c lop e " ia o$ n " u st rial C he mistr%' ile % ' . e rm a n%' 2 012

GJH ; , 6on s " ale' he g ro wt h o$ m e m b ra ne te c h n o log %' 2 * e m b r S c i 1 0 (1 8 J 2) J 1

1 J 1 G8H EF Er u gg e n' D e sa lin a ti o n b% "is ti lla ti o n an" b% re v e rse o s mo s istr e n"s

towa r"s

th e $u tu re' * em br e c h n o l (20 0 3 ) @8

G10H E F Erugg en' C Fa n " ec as tee l e' F .e s te l' D o% e n b' ? 6 e% s e n b ' & r e v i ew o$

pre s sur e -"r iv en m e m b ra n e pr o ce s se s i n w a s te w a te r tr e a tme n t a n " " rin9 ing

w a te r p ro " u c tio n' # n v iro n ro g 22 (20 0 3 ) 7 @5 @

G11H C 0rit m a nn' 2 6o we nb erg' intg en s' * e lin' S ta te -o $-th e -a rt o $ re v e rs e

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m embran e m or pholog% an " t ran spor t properties'2 *e m br Sci 30 8 (200I)

2 082 21

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