effect of silica on the properties of cellulose acetatepolyethylene
TRANSCRIPT
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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 tempera- ture (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$$ect man% properties G17'15H
Farious pol%mers have been use" to s%nthesie membranes' but
cellulose acetate (C&) membranes are well accepte" "ue to their goo"
transport characteristics' low protein a"sorption' e>cellent water
a$/nit%' appropriate mechanical strength' e>cellent /lm-$orming
properties an" lower cost G1@'1IH ;ow- ever' C& has poor thermal
stabilit%' lower chemical resistance' in$erior mechanical strength an"
vulnerable to $ouling resistance here$ore' at- tempts have been
ma"e to improve the per$ormance o$ C&b% "eveloping h%bri" organic
inorganic membranes ew researchers have investigat- e" the e$$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 -
8/10/2019 Effect of Silica on the Properties of Cellulose Acetatepolyethylene
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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 par- ticles 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$$usion-in"uce" phase separation' vapor-phase precipitation'phase
inversion b% controlle" evaporation an" thermal-in"uce" phase
separa- tion (1:S) G27H &ll the metho"s involve comple> multi-
component
ig 2 ?elationshipbetween pressure an" Au>
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8/10/2019 Effect of Silica on the Properties of Cellulose Acetatepolyethylene
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mass trans$er e>cept thermal-in"uce" phase separation which
primari- l% "epen"s on heat trans$er G25H
n this paper' a "etaile" stu"% towar"s the s%nthesis o$ thermo-
able 2
#$$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>perimen- tal rig using a plate an" $rame membrane mo"ule &
schematic o$pro- cess 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"uc- tance 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% increas- ing 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
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8/10/2019 Effect of Silica on the Properties of Cellulose Acetatepolyethylene
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where w is wet sample weight an" D is "r% sample weight
ig 3 lu> o$ control an" mo"i/e" membranes over time
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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
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*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$$erential scanning calorimetr%!thermal "egra"ation
measurements o$ the membrane samples were per$orme" using 1&
instruments SD- @00 thermo gravimetric anal%er at a heating rate
o$ 10 PC!min an" temperature programs $or DSC were run $rom 30 PC
to J00 PC he ther- mograms $or 1.& were obtaine" using a c%cle o$
heating $rom an ambient temperature to J00 PCQitrogen Aow was
maintaine" at 15 m6!min in or"er to remove all corrosive gas
involve" in the "egra"ation
3@ *echanical stabilit%
ensile testing o$ membranes was per$orme" at room
temperature using an :nstron-t%pe tensile testing machine
(1estometric!*350-10C1 ?=C;D&6#' #nglan")with a crosshea" spee"
o$ 3 mm!min he sample wi"th was 25 mm an" the length between
the jaws was 75 mm he measurements were per$orme" at 25 PC an"25 Y 2Brelative humi"it%
3I Scanning electron microscop% (S#*)
Scanning electron microscop% was per$orme" on eol S*-@7J0
1he membranes were cut into small pieces an" place" on stub an"
9ept in a speci/c chamber in a vacuum he electron beams were
sputtere" on sample an" images o$ membranes on var%ing resolutions
were observe"
ig 8 DSC curves o$ the control an" mo"i/e" membranes
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silica amount he relative increase in water content is 3IJJB he *embrane t%pe S (*pa) #b (B) Containcrease" water content ma% be "ue to the increase in membrane h%"ro-
Control 2@387 5J 5721hilicit since the hi h h "ro hilicit $acilitates the "i$$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$$usion rate o$ water was accelerate" b% the
presence o$ #. "ue to its h%"rophilic nature #. increase" the
ten"enc% o$ pore $ormation an" as a conse+uence Au> was increase"
t was observe" that within the pressure range o$ 750 to @50 9a'
the Au> "ecrease" linearl% with increase in trans membrane
pressure as in"icate" in ig 2 hese results are in agreement with
the reporte" "ata G70H
he "ecline o$ Au> with the passage o$ time' even at high pressure
was attribute" to the compaction phenomena occurring on the
mem- brane sur$ace he compaction o$ membrane un"er pressure
involve" rearrangement o$pol%meric chains which le" to the change
in mem- brane structure with low value porosit% which conse+uentl%
"ecrease" the Au> Similar results were obtaine" b%&rthanareeswaranet al G3JH
=n the basis o$ salt rejection an" Au>' C&!#.-7 membrane was
selecte" $or mo"i/cation with silica &$ter mo"i/cation these
membranes were characterie" an" compare" with C&!#.-7
(control) he water content' Au>' salt rejection an" membrane
permeabilit% o$ mo"i/e" membranes are given in able 2
he water content o$ the membrane was relate" to the
h%"rophilic- it% o$ the membrane able 2 in"icates that the water
content an" mem- brane permeabilit% o$ mo"i/e" membrane
increase" with increase in
ig 10 1ensilestress an" elongation-at-brea9 o$ control an" mo"i/e" membrane
that a""ition o$ silica nanoparticles increases the Au> G71H he
embe"- "ing o$ silica particles in C&!#. membrane can also "isrupt
the pol%mer chain pac9ing b% creating microporous "e$ects between
inorganic particle an" pol%mer inter$ace he salt rejection increase"
$rom J15B to 82B $or CS-7 membrane as a result o$ incorporation o$
silica particles G72H ;ow- ever' a slight "ecrease was observe" at
highest silica loa"ing (5B w!v) his result can be attribute" to the
agglomeration o$ silica particles in certain locations which a$$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> $or
the con- trol "ecline" with the passage o$ 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$$ect on the h%"raulic
permeabilit% hus' when the #. concentration was "ecrease"
$rom 10 to 7 gm in the "ope solution' there was a correspon"ing
"ecrease in h%"raulic per- meabilit% $rom 2I0 to 1@J (O10C7
6!h m2
9a) t might be attribute" to the "isappearance o$pores which were
$orme"b% #. *oreparticularl%'
able 7
*echanical properties an" contact angle o$ control an" mo"i/e"membranes
ct angle [ ("eg)
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et al $or silica incorporation inpol%ami"e membranes' whichreveale"
CS-5 3J27@ 1033 2710
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C&!#.-1 membrane with the highest #. contents o$$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
characteria- tion 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" mem- branes' 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
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ig 11 S#* images o$ control (a) top sur$ace an" cross-section (b)
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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$
con- trol 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" $or
4 membrane he initial increase ma% be "ue to increase in
interaction between the silica particles an" pol%mers ;owever' an
e>cessive concen- tration ma% cause the aggregation o$ 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
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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" mem- brane 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($)
5 Conclusions
n this stu"%' thermo-mechanicall% stable membranes were
s%nthe- sie" through a 2-stage phase inversion metho"& series o$
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 au- thors 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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