Modified organosilicas for adsorption of some organic acids
The chemical modification of silica surface by nitrogen-containing organic reagents (y-aminopropyltriethoxysilane, imidazole or N-vinyl-2-pyrroIidone) and also with hexamethyl disilazane and hydrocarbon oligomers was proposed for the enhancement of adsorptive capacity of silica in respect to mqnocar...
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| Date: | 2001 |
|---|---|
| Main Authors: | , , , , , , , |
| Format: | Article |
| Language: | English |
| Published: |
Chuiko Institute of Surface Chemistry National Academy of Sciences of Ukraine
2001
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| Online Access: | https://surfacezbir.com.ua/index.php/surface/article/view/73 |
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Surface| _version_ | 1869291162036076544 |
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| author | Belyakova, L. A. Vlasova, N. N. Golovkova, L. P. Varvarin, A. M. Lyashenko, D. Yu. Svezhentsova, A. A. Stukalina, N. G. Chuiko, A. A. |
| author_facet | Belyakova, L. A. Vlasova, N. N. Golovkova, L. P. Varvarin, A. M. Lyashenko, D. Yu. Svezhentsova, A. A. Stukalina, N. G. Chuiko, A. A. |
| author_institution_txt_mv | [
{
"author": "L. A. Belyakova",
"institution": "Інститут хімії поверхні НАН України"
},
{
"author": "N. N. Vlasova",
"institution": "Інститут хімії поверхні НАН України"
},
{
"author": "L. P. Golovkova",
"institution": "Інститут хімії поверхні НАН України"
},
{
"author": "A. M. Varvarin",
"institution": "Інститут хімії поверхні НАН України"
},
{
"author": "D. Yu. Lyashenko",
"institution": "Інститут хімії поверхні НАН України"
},
{
"author": "A. A. Svezhentsova",
"institution": "Інститут хімії поверхні НАН України"
},
{
"author": "N. G. Stukalina",
"institution": "Інститут хімії поверхні НАН України"
},
{
"author": "A. A. Chuiko",
"institution": "Інститут хімії поверхні НАН України"
}
] |
| author_sort | Belyakova, L. A. |
| baseUrl_str | |
| collection | OJS |
| datestamp_date | 2018-11-27T09:42:39Z |
| description | The chemical modification of silica surface by nitrogen-containing organic reagents (y-aminopropyltriethoxysilane, imidazole or N-vinyl-2-pyrroIidone) and also with hexamethyl disilazane and hydrocarbon oligomers was proposed for the enhancement of adsorptive capacity of silica in respect to mqnocarboxyiic and bile acids. The calculation of the content of protonated and deprotonated groups on the surface of synthesized organosilicas with distinguished basicity of functional groups was performed using the program GRFIT for the model of diffuse layer. The contribution of hydrophobic and electrostatic interactions to the adsorption of organic acids was revealed. It has been established that the maximum of organic acids adsorption coincides with the value of pH at which the curve of increasing concentration of anion of organic acid and the curve of decreasing concentration of protonated functional groups of aminopropyl silica are intercrossed. |
| first_indexed | 2025-07-22T19:30:04Z |
| format | Article |
| fulltext |
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Jоuгnai
MODIFIЕD oRGAlt[osILICAs FoR ADsoRPTIoГ{ oF
soMЕ ORGA]чIC AсIDS
L.A. Bеlуakova, N.N. Vlаsova' L.P. Golovkova, A.M. Varvarin,
D.Yц. Lyashеnko' A.A. Svеzhentsоva' N.G. Stukalina, and A.A. Chuiko
Iпstitutе of Suфсе Сhеmistry, Nаtionql Аcаdеmу of Sciеnсes,
Gеп' Nаumoll str. ]7, Kуiv-I61, 03680, LIKJИINE' e-mаil: v-bеl@nаil.kаr'nеt
Abstraсt
Тhе сhеmiсal moditrсatiоn of siliсa surfaсe by nitгogеn-сontaining oгganiс
геagеnts (y-aminopгopуltгiеthoхysilanе, imidazolе oг N.vinyl.2-pyrrolidonе) and also
l''ith hехamеthyl disilazanе and hydroсaгbon oligomегs Was prоposеd for the
еnhanсеment of adsогptivе сapaсity of siliсa in rеspесt to mоnoоaгboхyliс and bilе aсids.
Thе сalсulation оf thе сontеnt of ргotonatеd and dеpгotonatеd groups on thе suгfaсе of
svnthеsizеd oгganosiliсas with distinguishеd basiсity of funсtional groups was pегГoгmеd
using thе progгam GRFIT foгthе modеl of diffusе layer. Thе сontгibution of hydгophobiс
and еlесtгоstatiс intеraсtions to thе adsoгption of oгganiо aсids was геvеalеd. It has beеn
еstablishеd that thе maximum of organiс асids adsoгption сoinсidеs with thе value of pН
at whiсh thе сuгve of inсгеasing сonсеntгation of anion of organic aсid and thе сuгvе of
riесrеasing сonсеntration of pгotonatеd funоtional grouрs of aminopropyl siliоa are
i ntегсгоssеd.
Thе dеvеlopmеnt oГ nеw mеthods of synthеsis of adsoгbеnts having high
sеlесtir,'ity in rеlation to oгganiс aсids is an impoгtant sсiеntifiс and praсtiсai problеm. Thе
inогgаniс сaпiегs, flrгst oГ all siliсiс onеs, arе thе most pеrspесtivе foг prеparation of
adsогbents foг organiс aсids, as thеy havе high сhеmiсal stability, do not swеl] at сontaсt
.,vith solutions, have a sufftсiеnt thегmal and baсtегial stabilitу.
Тhе suгfaсe of hуdroхylatеd amoгphous siliсa сontains wеak.aсid silanols as
funсtionai gгoups (thе сonstant of ionizаtiоn of silаnol groups is of 10.7.10-9). Thеrеforе
thе adsoгption of oгganiс aсids on a suгfaсе of hуdroхуlatеd silica is insignifiсant.
Chеmiсal modifiсation of siliсa suгfaсе is a handу mеthod foг diгесtional сhange
оf its adsoгption sеlесtivity' Thе inсrеasе of siliсa adsoгptivе сapaсity with rеspесt to
oгganiс aсids maу be aсhiеved by intгoduсtion of basiс gгoups onto suгfaсе layеr of siliсa.
In ргеsеnt aгtiсlе a сhеmiсal mоdеling of thе basiс nitrogеn-сontaining cеntеrs of
vaгious struсtuге on a siliсa surfaсe was сaгriеd out, and thе adsoгption of oгganiс aсids
оn synthеsizеd organosiliсas was studied
Thе nonporous' amorphous, pyгogeniс siliсa. aегosil (A-300) and maсгopoгous
siliсa - siloсhгomе (C-80 and с-120) wеге usеd as thе Staгting siliсa matеrial (Tablе l).
Thе сhemiсal геagents _ tгiсhloгosilanе (TCS), 1.aminopropyltriеthoxysilane
(AРTЕs), 2,4,б-triсhloгo-1,3,5.tгiazinе (TAZ), imidazolе (Im), N-vinil-2-pyпolidone
(VP), saliсуliс (Sal), bеnzoiс (Bеnz), сr.piсoiiniс (Piс), dеoхyсholiс (DCA)' gliсoсholiс
(GСA) and tauгoсholiс aсids (TCA) wеге usеd without additional puгifiсation'
Thе sресifiс suгГaсе arеa of studiеd siliсеous adsoгbеnts wаs dеtегmined by two
mеthods: l) bу thе low tеmрегatuге nitгogеn dеsorption mеthod using a GH-lgasomеtег;
2) from thе data of mеthanol adsoгption obtainеd in vaсuum adsoгptive laboгatory
еquiрmеnt with spгing qlartzbalanсе [1]'-ihе сonсеntrations of funоtional gгoups of hydгoхylatеd siliсas and siliсas
modifiеd w,ith basiс gгoups wеге detеrminеd bу potеntiomеtriс titration of wеighted
з5.7
роrtions[2].Wеightеdamountswеrе0.1g,titrantwas0.1МNaoH(oг0.1МHCI)+
0 1 М NaCI; solutton йru,. was 30 ml, сontaсt timе for siliсas modifiеd with basiс
gгoups was 4 h and thaiioi.ьya.o*yratеd siliсas was 24 h. Thе сoгrесtion on solubility of
siliсa for еquilibгium '"r"ii""'
(at pH > 9) was intгoduсеd [3] In сase of hydroxуlatеd
siliсas the titratlon was pегformеd in dehydгatеd ethyl a.lсohol [a]' The сonstants of
ionization of funсtionai gгoups of siliсas wеге сalсulaйd f.o. rеsults of potеntiomеtгiс
titгation using the неndБrson-нassеlbaсh equation: pK = pH + lg (1 - с) / с foг various
dеgrееs of ionization of surfacе сr [2,3,5]. Thе apparеnt сonstants of aсidity pKu wеre
dеtегminеd bу ехtгapolation for сr _+ 0'
Thе lR ,p...,u-oi сompaсtеd plates, of hуdroхуlatеd and modifiеd siliсas wеre
rесordеd in thе vaсuu*-."ii having сarz windows using thе spесtrophotometег IКs-29
ovеr thе intегval from 4000 to 1200 cm..
Thегmaldеstructionofmodifiеdsiliсaswasstudiеdbуusеofthегmalgravimеtriс
analуsis (Тhегmal uiit,у.", Q-15-0-0 D.,^ соnditions: T = zi.tooo 0с' oтA = l00 mV,
DТG=250mV,тс=2о-somg,v=l9:C/min).Thеaссuгaсyofdetегminationof
funсtiоnal gгoups сonсеntration was 5 % [6].
Thеadsoгptionoforganiсaсidshasbееninvеstigatеdundеrstatiссonditionsat
20 + 1
0с. Ехaсtlу 0 05 g of siliоa was plaсеd to 10 rrrl of acid solution (1 mmol of
bеnzоiс or сr.рiсolinr. uй,0'5 mmol of saliсуliс aсid or 01 mmol of dеoху-, gliсo- and
tauroсholiсaсid).Bileaсidsarеno,.noughandslowlywatег-solublе,thегеfoгethеir
solutions *.,. p,.pu,.Ъъ;l;йi.uiing and"stiггing i" t.iY]^lTlеraturе) of thе wеightеd
amounts. In suсh. *.y
"jr'u"is
of biй aсids with сonсentгation of 0.l mmol whiсh is in
l0-100 timеs lеss than сгitiсalсonсentration of miсellе-formation wеге ргеparеd [7]. Thеn
thе nесеssarу pН valuе (in intегval г,o' i1o 8) was positioned. Thе suspеnsions of
hуdroхyiatеd and modifiеd aегosils *.,. ui',i,,ing during 1 h, and the suspensions of
modifiеd sitoсn.omеs wе.. uno., stirring foг 24 h. йеforehand it was establishеd that this
timе is suffrсientiy fo.-u.hi.u.*.nt ol еquilibrium. Thеn pH vaiuе of solution was
mеasuгеd u,,ng un'uЪ.sal ionomеter вуЭц. Fuпhеr thе suspеnsion of siliсa was
сentrifugеd tzooo rpm, iЪi"l, a"а еquilibгium solution was sеparatеd. Aftегwards thе
conсеntгation oг o,guni. aсij,*as с.t...in.a bу use th^е^ spесtroрhotomеtеr Spесоrd
М.40. Thе valuеs of aсid adsorption wеrе dеtеrminеd as diffеrеnсе of aсid сonсеntrations
in solutions beforе and after adsoгptton'
organiсaminеsbelongtoсompoundshavingpгоnounсе^dbasiсpгopегtiеs.Thе
basiсitу of aminеs d;;".;;;; 9t..tu*r faсtoгs unJ.i..t'on еffeсts of substitutеs. Thе
aliphatiс aminеs
"un.БЪ
aпangеd in a sегiеs Jеpеnding on thеm proton.aссеptoг ability:
p.,йu'y u,"]nеs < sесond ary amines .':.1'u'y,
-u:in"'
Thеbasiсityofhеtегoсyсliсaminеsсontainingnitrogеngon'11."y.l.':l..-.1Tlyl,:,
aliphatiс aminеs. дmidЬs of aсids aге vеry wеak basеs, Тhе addition of proton to amtdеs
takеsplaсеasarulеthгoughtheoхygеnatom[8].Itmaуbеехpeсtеdthatthеnitrogеn.
сontaining gгoups of diffеrеnt struсture g,Jеd io.siliоa suгfaсe will inсгeasе not only thе
afTinity of oгganiс .;й1; silicu ,u.fuсйui ui*o will dеterminе the valuе and pH intегval
of adsoгption dеpending on thеiг struсturе.
Inoгdегtovегifythissuppositionwehavеsуnthеsizеdthreеsiliсasсhеmiсally
modifiеd bу:
о aliphatiс primaгу amino gтoups;
о funсtionat g,oup* соntaiiing hvе-membег hetеrocyсles with two nitгogеn atoms;
о amidе gгoups.Jьi.ь u.. in ivе-mеmbег hеtеronuсlеar сompounds.
RеalizationofсhemiсalrеaсtionsontosurfaсelayеrwaspгovеdbyIRspeсtral
сontrol ofl all stеps of siliсa modifiсation.
For sуntьеsi;;-;й"siliсa with aliphatiс pгimary amino groups thе known
rеaсtion of intегaсtion of sirfaсе silanоl в,o1Ьs *1}
r:"::l'",:;",11'JJ::'l"JJil'1fi.}?;
.irol." Thе сhemiсal fiхation of aminoрrоpуl gгoups on a slllсi
з58
сonditions ехсluding formation of oligomers. Thе subsequent hydгolysis of еsteг groups
and thегmal tгеatmеnt of modifiеd siliсa at l500C havе еnsured thе formati-on Ъг
additionаl siloхanе bonds on thе siliсa surfaсe [9]. The obtainеd oгganosiliсa сontains
only aminopгopуl groups' Thе basiс physiсoсhеmiсal paramеtеrs of aminopropy|siliсa arе
prеsеntеd in thе Tablе 1.
Tаblе 1
Рhysiсoсhеmiсal paгameters of hydroхylated siliсas and siliсas modifiеd by basiс oг
hydrophobiс gгoups
sшtaсе gloup absorрtion bands funсtional gгoups, сonstаntarеа,m./*
'i.т'ff'.ъу - ,Е*ътc-_ pK
3750
v(Si-OH)
0.40 0.43 7.85
\1 HCr) +
li'ith basiс
эlubility of
dгoxylatеd
:nstants of
:ntiomеtriс
:ог various
pKn wеrе
l.:сas wеге
:ег IКS-29
;аv'imеtгiс
= 100 mV,
:::ation of
::rtions at
- nmol of
*.i:сo- and
'еюге thеir
е .'i.еighted
.'':liсh is in
; '7]. Thеn
с:.sions of
:t:sions of
:: ihat this
.-:ion was
s..iсa was
г''' aгds thе
з: Spесord
.: .:tгations
с:lеs. Thе
::.tеs. Thе
:_ lllrJ.{
:.: that of
: :-. amidеs
е:ltгogеn.
г: эnly thе
:.i inteгval
::.:miсally
Е. :,]s;
з. spесtral
---.: known
2990,2955, 0.98
2930,2885
v(C-A{);
1670 v(C=O),
1490,1480
v(laсиm гing);
1420,1365
Aеrosil A-300 Рyпolidyl l.l3 з'15
Б(С.Кl
+ slloсlгomе | Iz irruфzolyl 1570 v(C=C); 0'25 0.22 4.55
с.l20 l4.t5,1545
v(C-N)
imidаzolе гing;
1470 6(N-!I) for
sесonoary
2minn mnllnс
-t
c-120 pvl v(N-H);
2983,2940,
2880 v(C-LI);
r5e0 6(Nr-lD;
1460,1425.
Aerosil A-380 Aminopro-
pvl
13 80
зз,75,зз15
v(N-H);
298з
'2940'
2880 v(C.}Г);
1590 6фI.ф;
t460, 1425,
l380 6(с.ю
Siloсhromе
с.80
Tгimеthyl.
silvl
2970'29з0
v(C-H)
U.J78
Siloсfuomе t6 Hydтoсаr. 297О,2920,
bon 28'10,2860
oligomеr, v(C.H)
trimеtttyl-
0.5
с-80
lne was
t-rllеd in
ili
rli.
]lll
з59
Thе mеthod of сhеmiсal assеmbly was appliеd foг prepaгing of oгganosiliсa сontaining
fivе.mеmbегed hеtеroсyсlеs with two nitrogеn atoms' Imidazolе was usеd as bondеd
funсtiona] сompound' Chегniсal immobilization of imidazolе on a siliсa surfaсе was
сarriеd out in thгее stagеs [10] Thе fiгst stеp is modifiсation of siliсa surfaсе by
aminopropуl groups as dеsсгibеd abovе' Thе sесond stеp is сhеmiсal intеraсtion of
suгfaсе aminopropуl groups with 2,4,б+riсhloгo.1,3,5-tгiazinе.The сhеmiсal intеraction of
aminopropyl gгoups of modifiеd siliсa with 2,4,6-tгiсhloro-1,3,S.tгiazinе was сarried out
with a уield of 100 %. At last thе third step is the inteгaсtion bеtwееn thе siliсa modifiеd
Ьу 2,4'6- tгiсhloгo-1,3'5.triazinе and imidazole with subsequеnt hуdгolysis of thе thiгd
сhloгinе atom oГ symm.-triazinе molесulе'
<\
А-J"
I:siosi(сH2ъN(}l)
-tr-.r"o./tt
ll l+*Y*
I
сl
t<\
/rN_--_-> :sio{l1сн,дш1н1
\-т-
ъt\/
.T.
сl
This rеaсtiоn has 100 oА-уiе|d as wеll. Thus, as a гesult of сhеmiсal assеmbly, thе siliсa
suгfaсе modifiеd in thгеe steps сontains onlу imidazolе gгoups (Тable l).
For fiхation of amidе gгoups on siliсa suгfaсе thе solid-phase hydrosilylation
mеthod was usеd. N.vinyl-2-pyrгolidonе was usеd as nitrogеn.сontaining rеagеnt. The
сhеmiсal immоbilization of N-vinyl-2.pуrrolidonе has bееn fulfillеd in two stеps. Thе
intегaсtion bеtwееn silanol gгoups and triсhlorosilanе tеnds to сhеmiсal bonding of
siliсon-hуdгidе gгoups onto siliсa suгfaсе [11]. Thе obtainеd hydгidе siliсa was subjесtеd
to hуdrolуsis'
Нуdгolysis of thе suгГaсe сhlorosilyi gгoups was undегtakеn to pгеvеnt thе
foгmation of hydгogеn сhloгidе and /or hydroсhloгiс acid during thе subsеquеnt rеaсtion
of N.viny1-2.pугrolidonе so1id-phase hуdrosilylation. Hуdrogen сhloгidе and
hydгoсhloгiс aсid pгomote sidе pгoсеsses, suсh as aсidiо hydгolуsis of siliсon.hуdгide
gгouрs' hydгolуsis and dimегization of N-vinyl-2-pyгro1idonе [12]. Chеmiсal геaсtion
Б.t*.en siliсon-hydridе groups of hуdride siliсa and N-vinyl-2-pyгrolidonе was caггiеd
out without solvеnt and сatalуst:
-:SiOSi{nt.T,
ll
r
I
-Siosiil
+ сн,=CГ
oн
I
""р
З60
n :.е siliсa
r:. .r'latioп
!ц...]t The
l ;-':эs. Thе
з. .:ing of
ш ..эjесtеd
F:
E.
Ь:-
EI
! Ь:
' еnt thе
:еaсtion
:3 and
.:lуdгidе
:еaсtion
. сarriеd
Тhе polymеrization of N.vinyl.2-pyrгolidonе is a sidе геaсtion that takеs plaое during thе
solid.phasе thегmal hуdгosilylation. Foгmеd polymег is adsoгbed on thе surfaсe of
hуdгidе siliсa [13].
Thе sуnthеsis of hydrophobiс siliсa with trimеthylsilyl gгoups was сaггiеd out in
onе step bу геaсtion bеtwееn frее silanol gгoups of siliсa surfaсe and satuгatеd vapor of
hехamеthуldi silazanе [9].
Thе pгeparation of hydгophobiс silicon dioхidе with hуdrосarbon groups onto
suгfaсе laуег сonsists of four stagеs. Thе first step is thе modifiсation of siliсa suгfaсe bу
=Si.H gгouрs as dеsсribеd abovе. Then thе addition of 1-hеxеnе to suгfaсе of hydгide
siliсa (the solid-phasе hydrosilylation) was fulfillеd:
=Si-o.si(oн)2H + CH2=СFI-(Cн2)3.сн3 * =Si-o.si(oH)z-CHz-Сн2-(сH2)3-сH3
This rеaсtion was еffесtеd at high pгеssuге of гeagеnt in stainless stеelautoсlavе at 300 0с
fbг 3 h without сatalуst and solvеnt' obtainеd oгganosiliсa was subjесtеd to hуdгolуsis. At
last thе intегaсtion of foгmеd silanol groups йth hеxamеthуldisilazanе (еndсapping) was
сaгriеd out [9].
Thе synthеsizеd oгganosiliсas with basiс nitrogеn-сontaining and hydгophobiс
groups havе Ьigh hуdгolyiс, сhеmiсal and thегmal stability. They withstand prolongеd
iontiсt with watег and organiс solvеnts (toluеne, dioxanе, bеnzеnе) in thе Soxhlеt
apparatus and do not dеstгoу under сontaсt with minеral acids. Thе thеrmal dеstruсtion of
йoсiл.с laуег of siliсa in air and in vaсuum bеgins at25О and 400 0с, rеspесtivеly.
Somе phуsiсoсhеmiсal paramеtегs of silica mоdifiеd bу basiс and hydrophobiс
gгoupS arе pгesеnted in thе Tabiе l Thе spесifiс surfaсе aгеa оf siliсas duгing modifying
i.guiu' dесiеasеs. Thе valuеs of сonstants of ionizatiоn of silanol gгoups of initial siliсas
aге aссoгding to litегary data [14].
Consiants of ionization of nitгogеn-сontaining basiс groups of modifiеd siliсas
inсгеasе in sеquеnсе: aminоpгopуl > imidazolуl > pyп.оlidуl. Constants of pгotonization
dесгеasе in thе same onе. As wе supposed, thе amidе gгoups fixеd on siliсa surfaсе havе
thе lеast basiсity Thе basiсity of amidе gгoups сhemiсally immobiiizеd on a siliсa suгfaсе
is highеr than that of aliphatiс onеs. It is slightly higheг than thе basiсitу of starting N.
vinyГ-2-pyгrolidonе It is know that thе stгengthеning of basiс pгopегties of amidе
nitrogеn ian aсhievе by геplaсemеnt of hydrogеn atoms of amino gгoup on mеthуl groups
[8] Ёеsides the basicitу оf сyсliс amidеs is highег than aliphatiс onеs' An inсгеasе of
Ьuii.ity of graftеd amidе g,oups in сomparison with basiсity of thе staгting modifiеr
ф]-vinyl-2-pyггolidonе), apparently, is сausеd by rеplaсеment of unsaturatеd vinyl gгoup
йьi.ь
-i'
onе of substituеnts at nitгogen atom in N-vinуl.2-pyггolidonе molесulе on
CНz-CHz _ gгoup of thе siliсa suгfaсe as a rеsult of solid-phasе hydгosilylation reaсtion.
тhе Бasiiity of gгafted aminopгopуl (PKo= 6.90) and imidazolуl grouрs is lowеr
than that foг aiiphatiс amines (pK"= lO.7) and Staгting imidazole (PKu= 7 03). Thе
dесrеasе of basiсiiy is tуpiсal foг funсtional oгganiс gгoups bondеd on siliсa surfaсe. It is
сausеd by intгoduсtion of thе massivе substituеnt (siliоa suгfaсе) in struсturе of funсtional
rеagеnt.
Thе adsoгption of somе monoсaгboxyliс (benzoiс, сr-piсoliniс and saliсyliс) and
bitе (dеоxyсho1iс, gliсoсholiс and tauгoсholiс) aсids on a suгfaсе of staпing hуdгoxylatеd
siliсas anj sуnthеsizеd oгganosiliсas with basiс or hydгophobiс gгoups (Tablе 1) was
irrvеstigatеd. Dеtегminatioi of organiс aсid сonсеntгations in solutions beforе and aftег
adsoгplion has bееn сaпied out by a spесtгophotomеtry (on absoгption of aсids in UV
rеgion;. Dеpеndenсе of absoгption spесtгa of aсid sоlutions on pH prеviously was
iniеstigatеd. It has beеn еstablishеd that thе position and the intensity of absorption band
ma*imi..m сhangе fтom 230 nm (в 11600) to 224 nm (e 9000) foг bеnzoiс aсid in interval
of pH from 2 to s Thе alteration of maхimum position from 303 nm (pH 2) to 296 nm
з6l
(pH a-8) in thе absoгption spесtrum of saliсyliс aсid is obsеrvеd' In this сasе thе
absoгption band intеnsitу rеmains pгaсtiсally сonstant' е 3500 Тhe absorption band at
264-265 nm in thе sресtrum of с.piсoliniс aсid is obsегvеd' Its intеnsity сhanges
dеpеnding on рН It is е 800 at pH 3 (zwittег-ion ехists mainlу in solution) аnd е 450 at
pH 8 that сoгrеsponds to absoгption of anion. Thе obtainеd data aге in good agгееmеnt
with litегarу onеs' Thе сonсеntгation of bilе aсids was dеtегminеd by method desсribеd in
Il5] Сhosеn огganiс aсids distinguish in valuеs of ionization сonstants (Tablе 2). Fiрre
1 ргеsеnts thе distribution diagгams of aсid.basе foгms of thеsе organiс aсids in
dеpеndеnое оn pH.
Tаblе 2
Somе phуsiсосhеmiсai propегties of oгganiс aсids
Aсid pKa lgKor*
4'00 (сooн)
bеnzoiс
2.9(сooн)
l3.1(oн)
1.9'r
..А
L.LA
I.07 (сooH)
5.25 сN}г)
-l e8 (pH 2.0)
-l.50 фIr 7.a)
с.oiсoliniс
Thе diagгams show that saliсyliо aсid is prеsеnt in a solution pгaсtiсally
сomplеtеlу as anion within pH inteгval from2 up to 8. Bеnzoiс aсid ехists as both nеutral
Гогm and anion. Thе сonсentгation of anion of bеnzoiс aсid in solution bеcomes largег
than nеutгal foгm at pFI > 4 сr-Piсoliniс aсid is manly as zwitteг-ion. Thе anion of
с.piсoliniс aсid appеars in solution at pH > 5. Thus, wе had a good сhanсе to сomparе thе
intегaсtion of diffеrеnt Гoгm оf oгganiс aсids (nеutгal molесulе, zwittег-ion and anion)
with siliсa suгfaсе'
The геsults of study оf oгganiс aсids adsoгption on staгting and modifiеd siliсas
arе pгеsеntеd in Figs' 2-4'Benzoic and сx,-piсoliniс aсids pгaоtiсallу aге not adsoгbеd on a
suгfaсе of initial siliсa Thе сhangе of thеiг сonсеntгation in a solution aftег adsoгption
doеs nоt еxсееd an eггor of dеtегmination bу speсtrophotomеtriс mеthod. Thе adsorption
of saiiсуliс aсid on hуdroхуlatеd siliсa is insignifiсant (up to 8 % of initial сonсеntгation).
It doеs not praсtiсallу depеnd on pH of initial solution' Thе anion сonсеntration inсгеasеs
and nеutraifoгm dесrеasеs in initial solution of saliсyliс aсid at p|I>2. Тhе adsoгption of
saliсуliс aсid dесгeasеs pгaсtiсally to zеro at more high pH valuеs whеn thе dissoсiation
of silanol grouрs of si1iсa surfaсе begins. Thе еleсtгostatiс гepulsiоn prеvеnts thе
adsoгption' Ъppaгеntlу thе adsorption of saliсуliс aсid is сonditionеd by hydгophobiс
intеraсtions'
362
;е thе
tnd at
langеs
150 at
)ement
bеd in
Figuге
rds in
))
aсtiсally
r neutrрl
:s largеr
шion of
rpaгe the
J anion)
c siliсas
bеd on a
:soгption
lsorption
ltгation).
li-']сгeasеs
гption of
soсiation
еnts thе
:оphobiс
5
pi-r
Fig.1. Distribution diagгams of bеnzoiо, Fig.2. Adsoгption of saliсyliс aсid
saliсylic, and с.piсoliniс aсids. onto modifiеd siliсa surfaсеs as
a frrnоtion of pH.
Thе hуdrophobiсitу dеgгеe of molесulе сan bе сhaгaсtегizеd by thе сonstant of
distгibution betwееn apo1aг solvеnt (n-oсtanol is thе most frеquently usеd) and watеr [16].
Thе saliсуliс aсid is сhaгaсtеrized bу a small solubility in watег and high сonstant of
distribцtion in oсtanol/watег systеm (Po,* = 112) in сomparison with rеlatеd сompounds as
a геsult of foгmation of intгamolесulaг hуdгogеn bond [17] It maу supposе that what is
kлown ..hydrophobiс eхpulsion,' of molесulеs of saliсуliс aоid ocсuгs duгing adsoгption
fгom aquеous solution. Thе adsoгption on solid suгfaсе is moге ргеfeгable than thе еnегgy
unfavourable solvation. Bеnzoic aсid is not adsorbеd on thе siliсa surfасе dеspitе thе faсt
that it is in molесular foгm up to pH 4. Pгobably, thе aqueous еnvironmеnt for benzoiс
aсid moleсules is moгe ..prеferable'' Thе solubilitу of benzoiс aсid is betteг than that of
saliсyliс onе' Thе сonstant оf distгibution in oсtanoУwatег sуstеm (Pol*= 74) is еssеntially
lowег for bеnzoiс aсid [18]. сr.Piсoliniс aсid is сhaгaсtегizеd bу somе smallеr сonstants of
distribution in oсtanoУwatег sуstеm' It is igPo,*=_ 1.98 foг zwitteг-ion at pH 2 and
l8Рozo=-l'50foranion atp]H7,4. Thеhydгophobiсnatuгеof adsoгptionof saliсyliсaсid
on a suгfaсе of high dispеrsе siliоa is сonflгmеd by thс faсt that only saliсуliо aоid is
adsoгbеd in notiсеablе quantitу (largег than on staгting siliсa) on siliоa modifiеd by
tгimеthylsilуl gгoups (hydrophobiо siliсa). Bеnzoiс and сr-piсoliniс aсids praсtiсally arе
not adsoгbеd on the suгГaсе ofhуdгophоbiс siliсon dioхidе.
Fig.3. Adsorption of bеnzoiс aсid onto
modified siiiсas as a funсtion оГpH
Fig.4. Adsoгption of сr.piсoliniс aсid
onto modifiеd siliсas as a
funсtion ofpH.
з6З
Saiiсyliс and benzoiс aсids are adsoгbеd bеttеr on the siliсa suгfaсе modifiеd by
N.vinyl-2-pyггolidone. Thе basiс propегtiеs of amidе groups of immobilizеd
ш-vinyt.z-pугrolidone aге not high. йе havе сalсulatеd thе сontеnt of pгotonatеd and
oeproionatЪi funсtional groЦps й thе siliсa sцгfaсе using thе pгogram GRFIT for thе
,nod.l of diffusе layeг [i0]. it has bеen established that almost ail pуггo1idyl groups at
pН>2 arе dеprotonatеj anа nеutгai. Thегеfoге wе havе supposеd that thе adsorption of
anion of saliiyliс aсid whiсh predominates in the solution at pH > 2 and also thе
ud,o.ption of nеutral form and. anion of bеnzoiс aсid dеpends not on elесtrostatiс
intегaсtions but thе hуdrophobiс onеs as pгobablу in thе сase of starting siliсa. Thе
ьусгopьoьiсity oГ siliсa Ьodifiеd bу N-vinyl.2-pyпolidonе is highеr than that foг
hуdroхуlatеd si1iсon diоxidе, iь" adsorption of oгganiс aсids is muсh highеr for siliсas сontaining eleсtгon
donor aminop,opyt oг imidazЬlyl gгoups. It should bе notе that thе adsorption on surfaсе
оf siloсhromе сontatning aminopйpуl gгoups is slightlу smal1ег than that on thе surfaсe
оf aminopгоpуlaеrosil. Ьo*.u.1.' ii-is possiblе to еxplain by smallег сonсentration of
aminopropyl groups pег unit of thе surfaсе and by smallеr valuе of thе spесifiс suгfaсе
arеa of siloсhrоmе соmparеd with aегosil.
T'hе dеpеndеnсe of adsoгption of bеnzoiс and saliсyiiс aсids on pH is a сurvе with
maximum. Its pоsition dеpеnds on nature of donoг gгоups of adsoгbеnt and
monoсaгboхуliс aсid. It is duе to distinсtion of сonstants of aсidiс dissoсiation of bеnzoiо
and saliсу1iс aсids, and also with distinсtion of сonstants of pгotonization for
аminop.opуlsiliсa and siliсa modifiеd by imidazolе (Tablе 1). Protonated aminopгopyl
groups domlnatе on a siliсa up to pH 5 -and
protonat.еd nitтogеn atoms of imidazolе
i,.uuli up to pAI 3.5 as follows from сalсulation pегfoгmеd bу the progгam GRFIT.
Ьaliсуliс and bеnzoiс aсids at thеsе pH eхist in solution as anions, and с-piсoliniс aсid is
as zwittеr-ion. The еleсtгostatiс attraсtion faсilitatеs adsoгption of aсid anions on the
suгfaсе of siliсas modifiеd bу еlесtгon donor funсtional gгoups. This intеraсtion for с-
piсoliniс aсid apparеntiу is weakеr bесause thе nеgativе and positivе сharges in zwittеr-
ion arе сlosе from еaсh other. Thus, thе attraсtion ofdiffering сhargеs is pгobable as wеll
as thе гepulsion of thе same onеs.
Figurе 5 pгеsеnts сuгVеs of aсid-basе foгms distribution foг saliсyliс aсid and
thosе foг !гotonaiеd and dеpгotonatеd aminopropyl groups of
'aminopropylaerosil
surfaсе
as a funсtion oГ pH. Thе сurvе of pfl-dеpendеnсе of saiiсуliс aсid adsoгption is givеn
also.
Fig.S. Distгibution diagrams of pгotonatеd
and nеutгal aminogroups onto
aminosiloсhromе suгfaсе, saliсyliс
aсid in solutiоn and o/o of saliсуliс
aсid adsorption as a funсtion of pH.
Тhе maximum of aсid adsoгption pгaсtiсally сoinсides with pF{ valuе, at whiсh
сuгvе of inсгеasing сonсеntration of anion and сuгvе of downwaгd сonсentration of
364
prоtonated surfacе aminopгopyl groups aге interсгossed, It tеstifiеs to dеtегmining гolе of
thе еlесtгostatiо сontгibution in adsoгptive intегaсtion.
All invеstigatеd bilе aсids (dеoхyсholiс, DC& glyсoсholiс, GсA, and
tauroсholiс, TCd aсids ) are adsorbеd on a suгfaсе of initial high disperse siliсa. Thе
dеpеndеnсe of adsoгption of bilе aсids on pH of aquеous solutions is prеsented in Fig. 6.
As thе pН of solution inсrеasеs, thе adsoгption of bilе aсids dесгеasеs' Thе adsoгption of
bilе aсids at the samе pH diminishеs in sеquеnсе. DCA > GсA > ТCA' It this sеquеnсе
the solubilitу of aсids and, hеnсе, thеiг tеndеnсу to hydгation in aqueous solution
inсrеasеs. Thе dесгеase of adsoгption of bile aсids сoinсidеs with thе гeduсtion of
quantity of nondissoсiated silanol groups and paгt of bilе aсids in molесular foгm. Wе
havе dеtеrminеd thе dissoсiation constants of bilе aсids bу potentiomеtriс method for
aquеotts solution with ioniс stгеngth, whiсh is nеaг to 0. Thе pK values dесгeases in thе
same sеquenсе: 5.6 for DСA -3 foг GCA and - 2 foг ТCA
l
* DсAl
l+GсА|
I+тсAI
\.r
5
ptl
Fig.6. Adsoгption of bilе aсids onto Fig.7. Adsoгption of dеoxyсholiс
highly dispегse siliсa as a funсtion aсid onto modifiеd siliсas
of pH. as a funсtion of pH
on thе basis of thеsе data wе havе supposеd that bilе aсids arе adsoгbеd mainlv in
molесular form on nondissoсiatеd siliсa surfaсe foгming adsoгptivе сomplexеs of
сomposition (=Si.oH-HCA). The adsorption сurvе of bilе aсids has beеn сalсulatеd usins
the pгogram GRFIT. It appearеd that thе сalсulatеd сuгvе and ехpегimеntal onе do noi
сoinсide. Thе bеttеr сoпespondenсе is obsеrvеd with thе formation of сomplеx
(=Si-oH.CA-) bеtwееn silanolgroups and anion of bilе aсid also. Dеspitе of thе inсrеasе
of сonсеntгation of aniоn with pH inсreasing, thе adsorption of bilе aсid dесrеases. It is
assoсiatеd with thе appеaranсe and thе aссumulation of nеgativе сhaгgеs on suгfaсе as a
rеsult of the dissoсiation of silanolgroups. Мotivе poweг of adsoгption, apparently, is thе..hydгophobiс ехpulsion'' of molесulеs of bilе aоids fгom a solution. Thе adsoгption on
siliсa suгfaсe is еneгgу more favouгablе than solvation in aquеous solution. Нowеvеr' it
does not exсludе the faсt that adsoгptivе сomplех has foгmеd as a rеsult of hуdrogеn
bonds betwееn silanol groups of suгfaсе and suitable funсtional gгoups of bilе aсids. Thе
introduсtion in molесulе of сholiс aсid of suсh substituеnts as glусinе oг tauгinе геsults to
inсгеasе of solubility of bilе aсid, that is, to dесгеasе of hуdгophobiсitу Indеed, the
invеstigatеd aсids aге chaгactеrized by diffегеnt valuеs of thе сonstants of distribution
bеtwееn n-oсtanol and watег: lgPol* is 4 7 -4 .2 foг DСА' 2.28-| 89 foг GCA and 2 '06-l .5g
foг TCA. The valuеs of distribution сoеfTjсiеnts еstimatеd rvith vaгious mеthods by
authors of the pгogгam ChеmDraw aге presеntеd. Fгom all bile aсids invеstigatеd by us
dеoxyсholiс aсid is thе most weak and hydгоphobiс Аppaгеntly, thегеГоге it is adsorbеd
bеttег than otheг bilе aсids' Thе hуdгophobiс сharасtеr of adsoгptiоn of bilе aсids is
36s
5
Ёl
confirmеd bу геsults oГ thе studу of influеnсе oГ ioniс stгеngth on adsoгption value' Thе
adsoгption of DСA Ггom solution in 0 05 М NaСl in aсid геgion inсгеasеs pгaсtiсally up
to 100%. .rhеn
thе adsoгptiоn valuе (aftеr pH> 5) bесomеs lеss than it fгom solutions
with ioniс strеngth - 0 Thе addition of еlесtrolyе results to thе еnhanсing of thе
..hydгophobiс ехpulsion'' Ггom solution (еffесt of salting out). Тhегеfoге thе molесulaг
form of bi1е aсid is adsoгbеd bettеr from еlесtrol}tе solution. Thе сoгrеsponding salts of
bilе aсids aге muсh bеttег dissolvеd in watеr and arе bеttег solvatеd. Thегеfoге bilе aсids
as anions arе worsе adsoгbеd on a siliсa suгfaсе prefегring an aquеous еnvironmеnt.
on thе basis of obtainеd data wе havе assumеd that thе adsогption of bile aсids
would inсгеasе by usе of adsoгbеnts with еlесtгon donoг groups on a suгГaсe whiсh havе
tеndеnсy tо thе protonization. Thе adsoгption ofdеoхусholic acid on thе suгfaсе ofsiliсas
modifiеd by aminopгopyl-, imidazolyl- and pyгrolidуl gгoupS was studied. Thе
intrоduсtion ofеleсtron donor gтoups tеnds to inсrеasе ofadsoгption and eхpansion ofpH
intегval in whiсh it was сaггiеd out (Fig. 7). Thе сalсulatеd сonсentrations of thе
pгotonatеd and nеutral gгoups of amino- and imidazolе-сontaining siloсhгomеs wеге
сompaгеd with valuеs оf dеoхусholiс aсid adsoгption on its suгfaсеs. It appеaгеd that thе
adsoгрtion of dеoхyсholiс aсid on thе suгГaсе of imidazolе-сontaining siliсa is obsегvеd
еvеn in that рH rеgion whеге thе positivе сhaгgеd funсtiоnal groups of surfaсе is absent
сomp[еtеlу, Aррarеntly. thе suгfaсе of siloсhгomе as a rеsult of modifiсation bу imidazolе
bесomеs moге hydrophobiс It rеsults to incrеasе of adsoгption oi dеoxyсholiс aсid. Thе
modifying of siliсa surfaсе by N-vinуl-2.pyпolidone pгaсtiсally doеs not influеnсе on
valuе of dеoxусholiс aсid adsoгption'
It should bе notеd that thе adsогption of deoхyсholiс aсid also inсгеases on thе
surfaсе of h.ydrоphobiс siliсas modifiеd by tгimethylsilyl groups oг hуdгoсaгbon
o1igоmегs as сomparеd with adsoгption оn staгting siliсa'
Thus it has bееn shown that thе modifiсation of siliсa suгfaсе with еlесtгon donoг
oг hуdгophоbiс funсtiоnal grоups increasеs its adsoгрtivе сapaсity in rеlation to
mоnосaгboхуliс and bilе aсids Thе гolе of hydгophobiс and еlесtгostatiс intегaсtions is
rеvеаlеd at adsorption of oгganiс aсids on a suгfaсе of hydгoхуlatеd siliсas and siliсas
modifiеd bу nitгogеn-сontaining basiс gгoups It has bееn еstablishеd that thе сontribution
tо adsoгрtion of еlесtгоstatiс intеraсtions bеtwееn anions of oгganiо aсids and protonatеd
functiona1 grouрs of thе suгfaсе of organosiliсas risеs as the pгoton aссеptoг abilitу of
funсtional gгouрs inсrеasеs'
Rеfеrеnсes
1. Kisеlеv A'V., Dreving VP @ds) Еxperimеntal Меthods in Adsoгption and
]r,Iolесular Сhгomatogгaphy tv{ : Izd-vо IV{GU, 191З. _ 448 p.
2' Gеlfеrikh F' Iоn-ехсhangеrs. Fundamentals of Ioniс Rеplaсеmеnt: Trans. from Еng. -
М.: Izd-vo Inostr. Lit',1962 _ 49О p
Bеlуakоva L.A., Il,in V G. Ion Еxсhangе Propепiеs of Сrystal Polysiliсiс Aсids //
Tеorеt. Еksрегim. Khim. - 1975.-v 11, }i 3 -P'зз7.з4l..
Dеnеsh I. Titration in Nоn.Aquеоus N1edia. Тгans. Ггom Еng, . М: Мiг, 1971. _ 413 p.
Sсhindlеr P', Kambег G.R. Aсiditу of Silanоl Gгoups ll T1e|у, Сhim. Aсta. -1968. .
v. 51, N 9. P l78l-1785.
Bеlу'akova L.A, Tепуkh V'A., Boгtun A.I Тhе Usе of Thегmal Analysis for
Dеtегmination оГ Conсеntгation of Graftеd oгganiс Groups in Soгbеnts and Catalysts
basеd on Siiiсa // Khimiсhеskaya Tеkhnologiуa. - l987 -N 2. - P.3-10
Data fсlг Bioсhеmiсal Rеsеarсh / RМ.с. Daц,son, D,с. Еlliot, W.F{. Еl1iot,
K.М. Jonеs. - oхfoгd. Сlaгеdon Prеss, l98б. - 544 p.
Теmnikоva Т.I Тhеoгеtiсal organiс Chеmistry. Lеningгad: Nauka, 1968. . 1008 p.
Tепykh V A. Bеlyakova L.A. Chеmiсal Rеaсtions with Paпiсipation of Siliсa
Suгfасе' Kiеv. Naukova Dumka, 199l. _ 264 p' (In Russian).
А
5
I
9
l0. Сhеmical Мodifiсation of Dispеrsе Siliсa by l,3.Diazolеs l У.^. Teпykh,
L.A. Belyakova, T.P. Kolotusha, D Yu. Lyashеnko, V.F. Gaеvskiy // Adsoгbtsiуa i
Adsorbеntу. - 1983. _ N l l . -P.|8-22
l l Low M.J.D,, Sеvегdia A.G., Chan J. Infтaгеd Study оf Soгption of HSiCЬ on Siliсa
and Stability of Chemisoгbеd Laуегs // J. Colloid Interfaсe Sсi. . 1982. -v. 88, N 1. -
P.lll-118.
12. Sidеl'kovskaya F.P. Chеmistry of N.Vinylpyпolidonе and its Polymеrs. М.: Nauka,
19-10.-149 p. (In Russian).
13. Bеlyakova L.A', Vaгvaгin A.М. Chеmisoгption of N-vinyl-2-pyпolidonе on Hydridе
Siliсa Suгfaсe /lТeoret' Еxsperim. Khim. . |999. - v. 35, N 4. -P.2з6-2з9.
14. Ilег R.K. Chemistry of Siliсa: Tгans. From Еng '. М.: Мiг, 1982. - v. l. _ 4|6 p'
15. Spесtrophotomеtriс Dеtеrmination of Bile Aсids / P'o. Ripatti, R.A. Popova,
T.B. Kagan, Z.A. Bеkhtеreуa ll Vopг. med' khimii. - l969. - v. 15' N 6. - P.630-633.
16. Sсhindlег P.W' Co.adsorption of Меtal Ions and organiс Ligands: Formation of
Tеrnary Surfaсe Complexеs // Rеviews in Мinеralogу - l990 - У . 2з. - P ,28|-з07 .
l7. Koгеnman Ya.I., Koгolyova T.P. Екгaсtion of oxybеnzoiс Aсids and Somе Their
Dегivativеs from Aquеous Solutions llZh'Prik|. Khim. . 1'915. - V' 48, N 6. - P.1413.
1415.
l8 Fujita Т'' Iwasa J.' Hansсh C. A New Substituеnt Constant, т, Dегived from Paгtition
CoеfT.iсiеnts ll I . Аrn, Chem. Soс. - 1964. . v. 86. N 22. . P.5175-5180.
l9 Ludwig Chг.'' GRFIТ, A Pгogram foг Solving Spесiation Problеms: Еvaluation of
Еquilibгium Constants, Conсеntrations and othег Physiсal Parameters'', Inteгnal
Rеpoп Univегsity of Bегnе, l992
20 Wеstall J.' Hohl H. A Comparison of Еlесtгostatiс Мodels foг thе oxide/Solution
|nterface.llAdvan. Colloid Intегfbое Sсi. - l980' -У.12. -P.265-294.
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| id | oai:ojs.pkp.sfu.ca:article-73 |
| institution | Surface |
| keywords_txt_mv | keywords |
| language | English |
| last_indexed | 2025-07-22T19:30:04Z |
| publishDate | 2001 |
| publisher | Chuiko Institute of Surface Chemistry National Academy of Sciences of Ukraine |
| record_format | ojs |
| resource_txt_mv | surfacezbircomua/d0/4f4f9b7f7fac7bbe406f4453f04462d0.pdf |
| spelling | oai:ojs.pkp.sfu.ca:article-732018-11-27T09:42:39Z Modified organosilicas for adsorption of some organic acids Modified organosilicas for adsorption of some organic acids Modified organosilicas for adsorption of some organic acids Belyakova, L. A. Vlasova, N. N. Golovkova, L. P. Varvarin, A. M. Lyashenko, D. Yu. Svezhentsova, A. A. Stukalina, N. G. Chuiko, A. A. The chemical modification of silica surface by nitrogen-containing organic reagents (y-aminopropyltriethoxysilane, imidazole or N-vinyl-2-pyrroIidone) and also with hexamethyl disilazane and hydrocarbon oligomers was proposed for the enhancement of adsorptive capacity of silica in respect to mqnocarboxyiic and bile acids. The calculation of the content of protonated and deprotonated groups on the surface of synthesized organosilicas with distinguished basicity of functional groups was performed using the program GRFIT for the model of diffuse layer. The contribution of hydrophobic and electrostatic interactions to the adsorption of organic acids was revealed. It has been established that the maximum of organic acids adsorption coincides with the value of pH at which the curve of increasing concentration of anion of organic acid and the curve of decreasing concentration of protonated functional groups of aminopropyl silica are intercrossed. The chemical modification of silica surface by nitrogen-containing organic reagents (y-aminopropyltriethoxysilane, imidazole or N-vinyl-2-pyrroIidone) and also with hexamethyl disilazane and hydrocarbon oligomers was proposed for the enhancement of adsorptive capacity of silica in respect to mqnocarboxyiic and bile acids. The calculation of the content of protonated and deprotonated groups on the surface of synthesized organosilicas with distinguished basicity of functional groups was performed using the program GRFIT for the model of diffuse layer. The contribution of hydrophobic and electrostatic interactions to the adsorption of organic acids was revealed. It has been established that the maximum of organic acids adsorption coincides with the value of pH at which the curve of increasing concentration of anion of organic acid and the curve of decreasing concentration of protonated functional groups of aminopropyl silica are intercrossed. The chemical modification of silica surface by nitrogen-containing organic reagents (y-aminopropyltriethoxysilane, imidazole or N-vinyl-2-pyrroIidone) and also with hexamethyl disilazane and hydrocarbon oligomers was proposed for the enhancement of adsorptive capacity of silica in respect to mqnocarboxyiic and bile acids. The calculation of the content of protonated and deprotonated groups on the surface of synthesized organosilicas with distinguished basicity of functional groups was performed using the program GRFIT for the model of diffuse layer. The contribution of hydrophobic and electrostatic interactions to the adsorption of organic acids was revealed. It has been established that the maximum of organic acids adsorption coincides with the value of pH at which the curve of increasing concentration of anion of organic acid and the curve of decreasing concentration of protonated functional groups of aminopropyl silica are intercrossed. Chuiko Institute of Surface Chemistry National Academy of Sciences of Ukraine 2001-06-10 Article Article application/pdf https://surfacezbir.com.ua/index.php/surface/article/view/73 Surface; No. 4-6 (2001): Chemistry, Physics and Technology of Surface; 357-367 Поверхность; № 4-6 (2001): Химия, физика и технология поверхности; 357-367 Поверхня; № 4-6 (2001): Хімія, фізика та технологія поверхні; 357-367 3154-8091 3154-8083 en https://surfacezbir.com.ua/index.php/surface/article/view/73/72 Авторське право (c) 2001 L.A. Belyakova, N.N. Vlasova, L.P. Golovkova, A.M. Varvarin, D.Yu. Lyashenko, A.A. Svezhentsova, N.G. Stukalina, A.A. Chuiko |
| spellingShingle | Belyakova, L. A. Vlasova, N. N. Golovkova, L. P. Varvarin, A. M. Lyashenko, D. Yu. Svezhentsova, A. A. Stukalina, N. G. Chuiko, A. A. Modified organosilicas for adsorption of some organic acids |
| title | Modified organosilicas for adsorption of some organic acids |
| title_alt | Modified organosilicas for adsorption of some organic acids Modified organosilicas for adsorption of some organic acids |
| title_full | Modified organosilicas for adsorption of some organic acids |
| title_fullStr | Modified organosilicas for adsorption of some organic acids |
| title_full_unstemmed | Modified organosilicas for adsorption of some organic acids |
| title_short | Modified organosilicas for adsorption of some organic acids |
| title_sort | modified organosilicas for adsorption of some organic acids |
| url | https://surfacezbir.com.ua/index.php/surface/article/view/73 |
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