A new method for determination of free surface energy and adhesion forces. Highly dispersed oxides, mesoporous and microporous materials
A new method of determination of the Gibbs free surface energy and the radial dependence of adhesion forces of adsorbents in respect to the interfacial water was developed on the basis of measurements of the dependence of NMR signal intensity of unfrozen water on temperature at T < 273K....
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| Datum: | 2001 |
|---|---|
| Hauptverfasser: | , , , |
| Format: | Artikel |
| Sprache: | Englisch |
| Veröffentlicht: |
Chuiko Institute of Surface Chemistry National Academy of Sciences of Ukraine
2001
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| Online Zugang: | https://surfacezbir.com.ua/index.php/surface/article/view/52 |
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| Назва журналу: | Surface |
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Institution
Surface| _version_ | 1869291134837063680 |
|---|---|
| author | Turov, V. V. Gun'ko, V. M. Leboda, R. Brei, V. V. |
| author_facet | Turov, V. V. Gun'ko, V. M. Leboda, R. Brei, V. V. |
| author_institution_txt_mv | [
{
"author": "V. V. Turov",
"institution": "Інститут хімії поверхні НАН України"
},
{
"author": "V. M. Gun'ko",
"institution": "Інститут хімії поверхні НАН України"
},
{
"author": "R. Leboda",
"institution": "Maria Curie-Sklodowska University"
},
{
"author": "V. V. Brei",
"institution": "Інститут хімії поверхні НАН України"
}
] |
| author_sort | Turov, V. V. |
| baseUrl_str | |
| collection | OJS |
| datestamp_date | 2018-11-27T09:42:39Z |
| description | A new method of determination of the Gibbs free surface energy and the radial dependence of adhesion forces of adsorbents in respect to the interfacial water was developed on the basis of measurements of the dependence of NMR signal intensity of unfrozen water on temperature at T < 273K. It was considered features of application of this method to highly disperse oxides, modified oxides, microporous and mesoporous adsorbents. The free surface energy values are computed for a variety of oxide and carbon-mineral materials. |
| first_indexed | 2025-09-24T17:44:38Z |
| format | Article |
| fulltext |
ANЕw}IЕTtIoDFoRDЕTЕRМINATIONoFFRЕЕ
sURFACв вгqЁксY Al\D ADIIЕsIoIt{ FoRсЕs. IIIGIILY
DISPЕ,RSвпохIuЕs,MЕsoPoRoljsANDМICRoPoRoUs
МATЕRIALs
V.V. Turov,, v.NI. Gun,kоl, R. Lеbоda,2 and V.V. Brеil
lIlistitlttеofSuфсеСhеmistr1','Nq|ionаlАсаdernуofSсtепсеs,
i; ь,;, Nаtlmoу, str., 03680 Kуiv' {JKRАINЕ
2Fалllt1'с,f Сt,,misiу,iio)io ё,,,iе-Sklodowskа йпit,ersit'',2003] Lubliп, PОIАND
Abstraсt
,\ ttсrv iriеthod of dеtегrrrinatioп оf rhе GibЬs {?ее suгfaсе еnеrgу and thе radial dеpеndепсе
i;t. achоstоn forсеs оf adsorbеnts in rеspесt to the intегfaсial watеr was dеvеlopеd on thе
i:asi: оt.mеasufеmеn.,;i;h;;;й*й of 'н N]rД. signal intensity of unfrоzen Watеr on
1i,iliрUtatuге at Т < 2.7Зii.' it *u,
"on,iае,еd
fеatu,еs оf фpliсation of this mеthod to highly
dispеrsе охidеs, modifiеd oxidеs, .i.,opo,ou, unс *"'oporous.adso.rbеnts Thе fгee surfaсе
еIlегg}, ,,'aluеs arе ""'";;;J
i;; a variеty оf охidе and сarbоn-minеral matеrials.
Introduсtiоn
NlvtRspесtrosсopуrnеthodis"*idеl),usеdtostudуthеstruсtuгеofoxidеlattiсеs.A
signifiсant pопion oГ thе rеsults has bееп
"ьi-йЪа
irtilizing thе solid-statе sресtгosсopу of
hish rеsоlution rь:iih magiс*anglе sрinning unо .'o'*.polarizЪtron (сP-lv1AS) or сombination
оf-thе гotation with thе multi-рulsе spесtrosс;py iё{дпrs). Thгeе.NМR signats of 29Si сan
Ье оbsегved fоr diiъг-е,-,iliiiJ"' tьЬе.j siiiJi,,iti.u g.i, еtс ). r*'hiсh aге linkеd to (a) St
atсms ГоurГold o-сoоrdinatеd in thе silоxanе bonds |=Si-o)lSi (6: -10s-1l0 ppm)' (b)
(=Si-o.Si)зSiotl (6 = _ss.tоо ppm) and.(с) (=si-o.si):Si(oH)2 gгоuрs (6 : *s9-9l ppm)
Il-3].
tн сRAчS. *"u,u,...nis sьо*'ьu' .,)iйui silanols сan form thе hуdrоgеn bonds
thеmsеlvеs or Wltn ;;;; watеr mоlес"l.' i;j. A similaг сonсlusion'was madе on thе
basis of thе broad linеlH NМR spескu ut а k,1+1. Analоgous rеsults wеrе obtainеd for
сoiluidal sоlutions oг.itun'inu using
,'A1 N'As iйR shоwing diffегеnt surrоundings of Al
аtоms [!6}
of thе first mеthods tо ехрloгеintегaсtion ьеtu,е;11!s,o^1ь;*"/:^:j::':l*i:i.
sl'lrfaсеs was basеd ";;;;;;*,.,n.nt,
oг'i,'.^й*p",aшrе {едеnjеnсiеs
oГlongitudinal and
сrоss-rеlaхation oГ nuсlеar spins of uo*o'ь.j-*Ьi"сulе, 1i. тье тrrobilitу of adsorbed
гrсlссulеs dесrеasеs *itь ,t,.ie'1.еning adsJr-p.tlonlnt.r.u"tio:il :l'.n геsцlts in a rеduсtion
oi thе ге1aхation timе' IntегmoJесular ias *"li as aсisorption) intеraсtions сan bе desсribеd
miJrе еntiгеlу u,'ng.й" ,"ii-аlгzu,i"" "o"m"йnt,
whiсh ian bе measurеd with pulsе-gradiеnt
оf thе iтegnеtiс frеld [s-1i]. Thеse mеasu,**.n'' dеnronstratе that thе intегaсtion bеtwееn
aсisоrbatё and аilsorbеnt is plopagatеа tь,oue;;i"rui'."rу thiсk laует of сompound adsorbеd
оn miсrоporо*, una й...Д й'utй,*, *ьi.ь Еan,.u"ь z-i nmrэг largег [9,l2]' In thе aquеous
suspеnsiоns oг o*io.,] ini",u"tlon of o,ut.,-'i]ith thе solid suгfaсеs сan bе dеtесtеd еvrn at
l00 nm distanсr duе tо long-гangе "o*рon"ni"nii'.'t"*ot..ular
intеraсtion [13]' foгmation
оfthе еlесtriсa, doublе tayеi 1t+.tь1, u'o.ь.i.o'tatiс and рolarization effесts Il7'18].
Onе of ,.hе rrrain paramеtеrs.r.,u,u"йLinfi*"'u.ilon,bеtwееn solids аnd liquids is
thе Gibbs f,..,u,й.";;.;у (1ф'.wrri1rr.ou.r,.to "ьunв:]i:l.
Gibbs frее еnеrgу with
inсгеasing surГасе ;;; й';;'
tшoti".
that thе сoггеsрonding еxact measurеmеnts arе vеry
rlt
ЕЕ
;}1LY
)ROUS
D
diffrсult. onе of well-known mеthods tо rjеtеrminе thе surfaсе еnergу of solids is a mеthod
of сontaсt anglеs ||9-2з]. It is assumеd in this mеthod that thе freе iurfaсе еnегgy еquals to
the sum of twotегms, and thе fiгst оf thепt is соnditionеd by LiГshits-van-dег.Wials forсеs,
and thе sесond is геlatеd to aсid.basе intегaсtions
ys =ys'* *ys"b
Тhе aсid-basе tегm сonsists ofеlесtron-aссерtoг (7) and еleсtгon-donoг (Y-) сomponеnts
ys'o = 2(ys*ys-)'"2 (2t
Тhеn thе сontaсt anglе value foг thе systеm with vapoг (V)' liquid (L) and solids (S) сaп bе
dеtегminеd as follows
сos9 = -t + 2[(ysL\yLLцr)l',2 /7l,w] + 2[(Y,* },,--)''' /Yll,] + 2[(уs- уL\||2 /тlu] (3)
Сomponеnts of thе frее surfасе еnегgy сan bе estlmatеd on the basis of thе mеasurеmеnts оf
the сontaсt anglе fог liquids with drffегеnt tyреs оf intеr-molесulаr intегaсtions' Anothеr
method to detегminе thеsе сomponеnts is Invеrsе Gas Chгomatography (LGс) |24-26l. In thе
Iast mеthod, a dispеrsion сomponent of thе strгfaсе еnergy сan bе еvaluatеd from an
adsoгption еnегgy poгtion pеr СH2 gгoup foг sегiеs оf aliphatiсs. Foг еstimation оf a polaг
сomponent, the adsoгption of molесulеs possessing given elеctгon-donoг pгopегties сan be
applied.
In liquid watег, the fгее suгfaсе energv Ys еquals to сhangеs in thе GiЬbs freе enегgу
oГ solidУwatеr duе to thе ехistеnсе oГ thе intегtЪсе Whilе thе bound watег lavеr haJa
signifiсant thiсknеss this parаmеtеr is intеgгal
",, =ioсo* (4)
I
whеrе r is thе tЫсknеss oГthе bound watег |aуer, АG is thе сhаngе in thе Gibbs freе еneгgy
II. Charaсtеristiсs of the bound wаter layеrs dеterminеd using 'H NМR
A mеthod of mеasuгеmеnts of thе lH Ntr{R signal intеnsitу oГadsorbеd watеr
depеndеnt on tеmреraturе at T < 2.73 K is usеful and infoгmativе to studу thе сhaгaсtеristiсs
of thе intегfaсial watеr. Thе intегГaсial watег nеar thе oхidе suгflaсеs сan bе fгozеn atТ < 2,7З
K duе to thе impaсt of solids rеsulting in a rеduсtion in thе free еnеrgy of this watег. Thе
thiсknеss of unfrozеn watег сan bе еstimatеd using thе ,H
]t]Tr,m' signal intеnsity mеasuгеd
during frеezing.de.frееzing proсessеs' Тhе intегfaсial wateг is in a quasi.liquid statе at Т <
273 K duе to aсtion of thе adsorbеnt suгГaсеs; thегеforе, a rеlativеlу narrow 'н NIrД' signal
сопesponds to this watег Thе signal of iсе is not obsеrved in thе ,Н NМR spесtra bесausе а
laгgе diffегenсе in thе timеs of сгoss-rеlaхation of ргоtons in liquid and fгozеn watегs.
Depеndenсе of thе unfгozеn watеr layег thiсknеss (i.e', the intеnsity / of thе 'H I.п,m'
signal) on temрerature of aquеous suspеnsions oг hydгatеd powdегs of diffеrеnt adsoгbеnts
was studiеd by many authoгs [21-З8]' It was shown that this thiсknеss dеpеnds on thе
hydrophiliс pгoрeгtiеs ofadsoгbent suгfaсеs; for instanсе, it dесгеasеs in suсh seriеs as siliсa
gеl > kaolinitе > Теflon [З4] Thеге is a I(T) hystеrеsis loop on frееzing-de-fгeezing I29'з7],
whiсh сan appеaг duе to ovеrсooling oГ R/atеr on fгееzing [29] Thегеfoге, thе 1(| funсtions
obtainеd on dе-frееzing of samplеs аfter frееzing up to T lowеr than a minimal tempегatuге
(r)
i.; :..Jеnсе
fr: - -ln th€
Е ]:ег on
!L: righlY
}т . ..rгfaсе
:еs. A
:эу of
:.atiоn
>i сan
a) Si
. (b)
?pm)
эоnds
.r thе
.J for
_i Al
. .оlid
.. and
' ' гbеd
- -:tion
::rbrd
. ]]lеnt
:.-.\'ееn
:гbеd
. . -еous
I :nat
-:tion
is is
',r,ith
.'еry
tlJ
i'.г watrr О\,етсooling aге mOге aрpгoргiatе to dеtегminе thе сharaсtегistiсs of thе intегfaсial
ц'atег A mеthod to mеasurе tь. ёlььi frее еnегgу оf adsоrbеnts using thе o"o:".9:i:^..:l'i?
signal of unfгo..n *u.., on,"*p.,o,u,е is basеi-on thе faсt that the frееzing tеmpегatuгe oI
thе intегfaсial watег ,,-,й..а Ъу tье valu.е.dеpеndеnt on thе suгГaсе еnегgу of adsoгbепt
and thе distanсе ь",*.*,ioi."uЬ,.nа solid surfaсеs [38.a1]. Сonditiоn of watег frеezing
at thе intеrfaсе is thе еqualitу оf thе.frее еne,gi.s oi *at"i^and iсе, and thе сiosег thе
adsоrbеd molесules to tiJ su.гa""s, thе lowеr thе iеmpегaturе of wateг freezing'
a
fi
t\
--)\r---
,/.ч
80604020 0
Chеmiсаl Shifl
50 1
Ф чUl
1/
О.x (р|)
.20 .40 €0
(ppm)
Fig.1.,нN]r,fRsignalofunfrozеnwateгinaquеotlssuspеnsionoffumеdsiliсa(spесifiс
suгfaсе arеa S = 300 m2lg), prеviouslу prеssеd ut i.t+*tоj Toгг and ball-millеd (a) and thе
gтaph of thе intеnsity oЕ,iЁ ьш.m. ilgnut ,,..*,-.h. u*oun' оf watеr (С") addеd to thе
рowdеr (b)'
Lеtusсоnsidеrtheappliсatiоnofthismethodtothеaquеoussuspеnsionoffumеd
siliсa (sресifiс suгfaсе u,*u s.* 30о m2lg), p*uiou,ry рrеssеd at l.14хl05 Toп and ball-
rniilеd. Fig, 1a ,ьo*, й.-'н NМR signal .of thе ,ni,o""n watег in suсh a suspеnsion at
diffеrеnt tеmpегatuгes ;l" ;;;"d si[nal islinkеd to mоbilе watеr molесulеs subjесtеd to
thе impaсt of thе siliсa surfaсеs, as oH group' "iiь.
oхidе surfaсеs and iсе do not сontributе
duе to a shoгt timе i. lЬ:; .joi.,o,,-,.-lu"ut;on ot p,otons in sоlids Тhis signal is individual
оnе lvith thе сhеmiсal shift * 4 ppпr (in геspесt tЬ тlts). Its intеnsitv deогеasеs but half-
width inстеasеs with lowеring tеmp^егatuге ,;;;;;.;J. чi
a
11g,"iion
оf thе molесular
mobilitуThесonсеntгation'ofunfrоzеn-atе.(С"")оanbееstimatеdusingthissignal
intеnsitv сomparing "'t.;.;;;
-,ignui
in'"nui'у "i.tЁ'Ьn
amount ot. watеr adsoгbеd on this
оxiсiе from thе gas phasе. Foг simpliсitу, on".un ulppry tеst.adsoтрtion oflwatеr fтom aiг at
.iеmрегatuге в.hеn this watеr is unfro,"n ,'i;;;;;;;Ь nуo,ш"с ш rеlativе mоisturе of 70
?zi and room tеmpеr.i",...iЪ а.,егminе tь. .Zn..nt,etion Ъг watег adsoгbеd on this sampiе
(С')' onе сarr utilizе *#;'aй;;t:т'yii,й lшк signal vегsus thе amоunt of watеr
iС,) addеd to ttrе powdеi uiing u mеtеring т;йe o.* ]9J.,}е
point of intегsесtion оf
itr.',.С)witlr thе Х.;;l,-;;;,"spond* tJ tье initiat сonсеntratiоn оi adsoгbеd watеr. Thе
h^^r
= tl rl
Ф|
:l
1
'o] ,/l/;r
'-q051
ti.i
:::.гfaсial
:е ofthе
:jluге of
j s cгbent
:. ееzing
, ]sег thе
.: есifiс
. :ld thе
r :о thе
thiсknеss (Ф of unfгozеn watег (as thе numbег of the statistiсal monolayегs) саn bе
ЖH:::
from thе сonсеntгation oi adsoгbЬd watег (С,,i ;];;,p..ifiс suгfaсе aгеa of
d: 3.I С"/S (5)
Fig' 2a shows thе gгaph of thе intensity of thе'unfгozеn waieг signal vегsus tеmрeгaturе,Changеs in thе Gibbs fгее еnегgу zс liiкeаiт."-:::,"* ,.'p.."i.,.* of watег frееzing сanbе еasily сomputеd' as. thе tйЁ.'oa|iu'iс funсtionJ of iсе are кnown oveг a widеtеmpеratuге range |42l' Thе геIationship between АG andT сan be *.iu"n as Гollows
АG=0.036(273_ц
(б)
The I(T) gгaph foг thе unfгozen watег сan bе easily tгansfoгmеd to thе dependеnсе oflG foг
;!:::ж:'кJЬ:iJi-. 1'i-..
oгtье boundu.y ь",*..n fio,;" ;;;nso,"n *".",i" ii"
Ё
.л
-/--*
210 220 2З0 24o 25a 26A 270
Тemperаturе (К1)
Е
-fх
O
,ьo
:: :-mеd
r: ball-
f,
"n
at
пе::еd to
г:::butе
к .:dual
h- ralf-
E .сulaг
Ь .:gnal
I , :. this
Fig. 2. Depеndеnсe of thе intеnsitу of unfгozen watеr signal vеrsus tempеratuге (a) аnd aсalсulated dеpеndеnсе o| vaгiation in г'.. .n..gу of watеi at tье slriсazwatег intегfaсe as afunсtion of distanсе toward suгfaсе (b) in Aегosi1-,ln uqu.ous;,p.;;;""
Somеtimеs an inсгeasе in the intеnsity of thе trMR signal with lowегing temреratuгеduе to еnhanсеmеnt of nuсiеaг lеvеl populaiйn (Сurie rulе [a3]) should bе сonsidегеd' Thегеis thе rеlationship bеtwееn thе nuсlЁar
'ugi.tйutlo" й);;Ь;.й.. with N spins withthе spin valuе s and thе gyromagnеtiс ratioig
]v{ : K]vg2h,rв + I)Bo/1kT (7)
wheгe Bo is the magnе.: fi:id. intеnsity, K is a. сonstant dеpеndеnt on NМR mеasurеmentсоnditions. Notiсе that for thiсk watег iaуers adsoгb.с on tri" ,u,йЪ., oг dispersеd oxides,the сhoiсe of mеasurеmеnt сonditions allows onе to obtain thе NМк slgnals of wateг (with
l"""T;.'",
сonstant ovег a widе rangе of thе tеmpе,u,u..,
.l."l
tь" Cuгiе rule сan bе
:]г at
= -.Г 70
.,nplе
: .,, ater
rn of
Тhe
0 2 4 6 ё l,olЪlц
d (Numbeг of stаtistiсаl monolayегs)
I l-5
Thе сapiilary еflесts in thе aqtrеous suspеnsions of fumеd oхidеs with nonpoгous
primaгу paгtiсlеs aге praсtiсallу absеnt and АG(С',) dеtегminеs сhangеs in thе GiЬbs fтее
:;;*,"ъli" й..гu.iui watеi as a radial funсtion of thе unfrozеn watег 1aуег thiсknеss
aгound sphеriсalpп.a| рaгtiсlеs as Сu' is.propoгtional to t|1.laуег,thiсknеss x. The valuе
of thе frее surfaсе
"n..gyЪгadsoгbеnts
in ttrе aquеous suspеnsions сan bе dеtеrminеd using
thе АGК|'*) funсtion and Еq. (4) сan bе rе-written as follows
Су
Ys:Ki
"iЬG1С".1dС", (8)
whеrе ,(l is a sсalе сoеffrсient, Сu,,* is the thiсknеss оf thе unfгozen watеr laуег
еxtrapolatеd vtttь lG(c,-) at АG -+ o (|f АG is in kJ/mol and Ys in mJ/m2 that Kl =55'615,
whеrе S is thе spесifiс su.faсе arеa of adsoгbеnt), Two poпions.of thе АG graph сan bе
,.p-*'"o Gig. zЬ) Thе first рoгtion сorгеsponds to a largе геduсtion in thе unfrozеn watеr
laYеr ovег a narrow lG rangе (nеar 213K) and the sесond onе is linkеd to small сhanges in
thе thiсknеss оvег a bгoad АG range' Thе fiгst type ofthе intегГасial watеr сan bе assignеd as
wеakly bound watеr 1tы.t.n",, a*j аuе to a long.angе сomponеnt оJthе suгГaсе foгсеs. The
sесond tуpе сorrеsрonds to a grеatег сhangе in thе frее еnergy (lG,) ovеr a shoгt distanсr
(d,) from thе surfaсе, i.e., thisis stгonglу bЬund watег. Thе thiсknеss of these layегs (d, and
d. for stгongly and wеaklу bound watегs) and ovеrali сhangеs in thе frеe еnегgy for thеm
(lG, and АG,) canbе еstimatеd using eхtraрolation of thе plots to the aхеs. In thе оasе of a
nеaгlу iinеaг shapе of thеse АG(с1) gгaph рortions, thе frее surfaое еnегgу at thе intеrfaое оf
oхidе/ц'atеr/iсе can bе dеtегminеd using a simplе еquation
rs __ KlИG,d, - АG*d-)/2 (9)
This valuе сan bе сomрutеd as a Sum of /G for all monolaуегs in thе intегfaсial watег
whеrе /G, is thе аvеrage valuе for thе i monolayег and 1
.<
i . !:
: d,+ dn, The /Gi valuе
сoггеsponds tо сhangеs"in thе frее еnегgy of the first monolaуeг. Thе ovеrall АG-* va|ue can
bе еstimatеd using thе АG(d) graph at d -+ 0
III. Rеlаtiоnshiр betwееn thе frее surfaсe energy }5 and оthеr
thermodуnamiс paramеters
Immеrsionhесtt,Thediffеrеntialimmеrsionheat}.isthеhеatеvolvеdduеto
addition of an infinitе amount оf liquid onto thе surfaсе at a givеn сovеIagе х [44]. Thе },
va.luе as wеll as /G сharaсtеrizеs thе suгГaсе forсе fiеld Thе value }' = 0 сorrеsponds to full
сompеnSationofthe*u.fu..еnеrgуbуthееnrrgуofadsoгbatе^intегaсtionwiththеsurfaсе.
Thе }" valuе as wеll a, iй" оirгейntlat сiьь' fй .n"'gy АG for diffеrеnt laуеrs dесrеasеs
fathеr and fatьеr awai i..-". iь" surfaсе. Тhе diffеrеntiut сiьь' fгее еneгgу еquals to thе
diffеrеntiаl woгk of adhеsion
Ys = Е^G,d'
АG _ _||"
( l0)
(11)
I l6
onpoгous
iibbs frее
thiсknеss
Гhе valuе
nеd using
5l
::ег layег
:г. сan bе
zеn water
:angеs in
ls.gnеd as
::;еs. The
: cistanсе
тs (d, and
:rг thеm
'.]sе of а
:::Гасе of
i
.:
i -l value
' .:Lue сan
r rilc tn
). Тhе },
шс. to full
l.-.гfaсе.
l : : ::.еasеs
Fi :o thе
Тhе Gibbs frее еnегgy inсrеasеs with inсrеasing distanсе from thе suгfaсе and this inсremеntеquals to a геduсtion of thе suгfaсe Gibbs fгее еneгgy of immersion. The сhangе in the Gibbsfiее еnеrgy of liquid is linkеd with the thегmodynaй. ;;i;;i;;i.
.
АG : _RT lп а'
.\ссoгding to the Gibbs-Hеlmholtz еquаtion...\.гlttеn аs Гollows
)" : dАHia : АG- T(dАG/aT)
'At thе samе timе, the dегivativе of АG,,T with геspесt to temperaturе is
_.4^G,
АI^/-]т\ -J}L,+1(_-)У\2У/])- AT'aT =--7u*
Fгom Еqs. (lЗ) and (14), onе сan obtain
)=_Т2+g =RT,(О |nа\0T T -- 'aТ...'lх,/х
Тhe thеrmodynamiс aсtivity of liquid at a givеn сovегagе of thе suгfaсе is
сI' : P"/P,
)-: Q, - Qo
АG:2-T4S
(12)
the diffeгеntial hеаt of immегsion can bе
(13)
(14)
( 1s)
( l6)
( 18)
(te)
.'''hегед is thе prеssuге of saturatеd vapor ovеr1h-е-intегГaсe liquid at сovera*e х, p, is thе]геssuгe of saturated vapor ovеr thе ргisiine liquid. Using вq riji one сan obtain
}" = Rr@h p,/eD' _Rt'oln p/dГ) (r7)
'",hеге thе fiгst tегm in thе.гig.ht paгt is thе liquеfaсtion heat Q,of the vapor on the suгfaсe of:hе liquid, the sесond one is thе liquеfaсtion Ьeat (Qd undеr standaгd сonditions. then
Сonsеquеntly, thе diffегential hеat of immегsion еquals to the diffегеnсе bеtwееn thеiiquеГaсtion hеats оfthе watег vapol ovег thе adsorbent suгfaсе and thе bulk water. Тhus,ihегe is a similaritу bеtwеen thе dеtегminatiоn of thе immегsion heat in Еq (18) and АGjеsсгibеd abovе. Both thе immегsion heat and diffегеntial ft;;;;; aге dеtегmined by thеjrffеrеnсе in thе thermodynamiс funсtions foг thе phase tгansfеi,to f... and inteгfaсialtquids Sinсе the frее еneгgy and еnthalpy aге linkеd ьу еquatiЬn_
-. .
lvhiсh сan bе ге-wгittеn for ovегall valuеs oГthе fгeе suгfaсe еnегgy and summary hеаt of:mmеrsion (}q) with сonsidеration of сhangеs in thе thегmoсynamiJЬnсtions ovеr thе total:hiсknеss of the bound watег layer
It7
^ f-,^. .У': А' - |/Д)(х).ft (20)
(2't)
and
Аt :
| /J7х
Тhе dеpendеnсе ofthe hеat effесt on tеmpегature сan сontгibutе Еq (20) Thе ovегall vаluе
oГthe immеrsion hеat is dеtегminеd at a fixеd tеmpеratuге; howе'',eг, the mеasuгеmеnt оf thе
fгее surfaсе еnегgy bу mеans of fгееzing-оut of thе bulk of watег is pегformеd оvег a bгoаd
tеmPегatuге гangе. Thегеforе Еqs. (l9) and (20) оan bе rе.wгittеn
(22)
(2З)
In thе litегatuге, thеrе aге not thе data геlatеd tо thе dерendеnсе of thе frее suгfaсе
еneгgy of siliсa on tempегatuге. Hоwеvег, similaг invеstigations pегfoгmed by mеans of
invегsе gas сhromatogapl]у (iGС) foг graphitе [24] show that a dispегsion сomponеnt of y.
dесгеasеs from 140 mJ/m, to |25 m!/mz with еlеvating tеmрегatur" f'o- 300 K to зь0 Ё.
onе сan assumе that similaг small сhangеs in Y, сan oссuг in thе сasе of dispегsеd oxidеs.
Thеn non-isothегmiсitу of fгееzing-out оf thе bulk watег undег thе 'н N]tfi' Ь.a,u,"."nts
doеs not givе largе епors in геsресt to 7., whiсh саn bе сompaгеd with thе frее suгfaсе
enеrgу dеtеrminеd using othеr mеthods,
Disjоining prеssurе and surfaсе forсеs
onе offтеquеntlу usеd сharaсtеristiсs ofthе surfaсе forсеs is thе disjoining prеssurе,
whiсh is thе diffеrеnсе bеtwееn the pгessltге P7 on thе liquid laуеr loсatеd bеtwееn iwo solid
suгfaсes and the pгеssuге Pр in thе bu|k oГliquid [13]
П(х):Pl _Po (24)
whеrе x is the thiсknеss ofthе liquid lаyeг. Bеsides, thе disjoining pгеssuге еquals to сhаnges
in the Gibbs frеe еnегgy ovег thе unit distanсе to thе suгfaсе
rrft) : ЧdGidх)TPр (2s)
Tурiсallу thе disjoining pгrssuгe is measurеd using diгeсt methods to dеtегminе thе
forсе needеd for сlosing two platеs in liquid mеdia and thеse methods aге desсгibеd in dеtail
еlsеwhеге [lз'l4]. Foгmally, the disjoining prеssurе valuе сan bе еstimаtеd from thе data
shown in Fig. 2b. Howеvеr, Еq (25) сorгеsponds tо thе dеtегmination of the .1 valuе аt a
сonstant tеmpеratuге. Therеforе foг isobaгiс fгееzing-out of thе bulk liquid, one сan usе an
effесtivе valuе ofsuгfaсе foгсеs, whiсh сan bе сalсulatеd using thе rеlationship
F : (дG n)tх (26) il
118
yJ::.'ftlж#:a:i"':,ТТ,rж:il#"'.,' х is thе distanсе to thе suгfaс e.If the АG
, - tGС,*х109
l8х (tч/c) (27)
wateг layеr (x) oг thе
. з]uе
': thе
::оаd
Тhе dегivativе valuе of /G with
сonсеntгatlon of unfгozеn watег
геspесt tо thе thiсknеss of the bound
0 : d(АG),dY, 0 = d(АG)/d(C',) (28)
r ) Ur
-. ^г^.!r ls
-r K.
'.ldеs.
: ^l OOIS
.:Гaсе
.съ
Е
2
э
ц
160T--
j
lаo. ol\ Iэ2ю:i l l
l\lool
I-1tl80Jiл
60] \12lrn4ol \ i]a\r2or t\
^1 .=чъ ]uJ \{
4гj
30
zэ
2О
0'0 0'5 l 'o l 's z|a_ii-Тo
х (nrn)
х (nm)
.]ngеs
il3;",;ff'"l
dеpеndenсiеs of adhеsion forсеs (a) аnd 0(х) value (b) for Aеrosil .\.aqueous
Мaхima of this dеpеndеnсе dеtегminе thе сhaгaсtегistiс distanlсonсеntration of bоund ivatег), f".;hi;;;ngеs in thе typе
",,u.;".: ;;'"*";":r;'::'Foг fumеd siliсa pгеssеd-at P: l50 baг, tье dеpendеn.сеs 0:I0) and F:f(x)aге shown inFig. 3, whеге Л is in HN pеr 8гam oi'uс'Ъ.ь."' and shows.tЬe intеraсtion foгсe bеtwееnliquid watеr and gгam oгsiliсaЪьi'
".r"."li"iс.o 'ьy
й. spЪ.ii".,u.ъ.. area сoггеspondsto thе adhеsion forсе pег unit oг tь" suйuс. arеa In thе сasе oi di,"", measuгеmеnts, thеflo;се bеtwееn two platеs in liquid
'".". l' .1'l'atеa J+s-+цъ;; ; ouг mеasuгеments, thеadhеsion Гoгсе valuе is сomputеd
"i
iь.'i"i.oсtion forсе Ъеtween thе solid suгfaсе andliquid mеdium. Thеsе forсеs aге th; 'ы. .ь.,..i.;;;";ii,,;;,.ou.u'.,"., studiеd forсompositеs and fillеd matters. onе сan sеpaгatе long.rangе and sйoп.гangе сomponents inthе adhеsion foгсеs for t,he aquеous ;;';;;;"" of -йmеisili"" .Fй 3). This suggеsts thеpossibility to introduсе thе dеiегminatioi oi.st,оncli' ;;; ;;;;,t^;;""d waters. Change inthе typе of thе suгfaсе fоrсеs oссuгs .' *.un.аluunсe to the suгfaсе of approхimatеIy l nm.
IV. Highly Dispeгse oхidеs
IV.l. Influеnсе.of thе а.|sor!е11 prеtrеatmеnt on аdhеzion forсеsТhе samplеs of fumеd siliсa A-ЗOrj (Pilot Рlant oгtь. rn,i;tulе.of Suгfaое Chеmistry,Kalush, Ukгainе; thе spесifiс surfaсе aгеa S ry з0О m2/g, uoou..nil"nsity Са x 4О mg/m|)
l_ :.е thе
-cеtail
.з data
.еata
jsе an
П9
wеrе studiеd. Thеy wеге as follows samplеs' non.tгeated (\,), pгehеatеd up to 520 K Гoг 3 h
(\), pгеviously wеttеd with watег (\) oг hехane (suppliеd by Aldгiоh) (\"-) followеd by
drying at 293 K (Cu - 90 mg/ml) as wеll аs thе samрle prеviously subjесtеd io pгoсeduге of
prеssing (l5 МPa, Сь= 25o mg/mi), (Ap) [50,5l]
Changes in thе lН NМR speсtгa as funсtions of thе tеmpeгaturе and thе siliсa
сonсentration foг thе fгozеn suspеnsion ofAn' aгe givеn in Fig 4a and 4b, rеspeсtivelу Тhе
spесtrum of wateг adsorbеd on An (Fig. la) hаs a singlе signal, whose rvidth inсгеasеs whilе
thеtеmpеraturе goеs dorvn duе to a dесlinе in the molесular mobility оf adsorbеd wateг and
thе intеnsity falls as thе thiсknеss of геgion aquеous сlosе to thе Ъiliсa suгfaсe dесгеasеs
thгough fгееzing. Тhе samе tуpе oftеmpегatuгe depеndеnt сhanges is oЬsегvеd in thе spесtra
rеgistегеd fo. \ and \"-' Thе signal of adsoгbed watег for \ and \ is obsеrved on thе
baсkgгound of a сonsidеrably widеr signa! having a shaре diffегеnt fтom the Gaussian onе
(bесausе of thеir similaгitу only thе sресtra foг watег on \ arе given) Thе intеnsitу of a
tlгoad сompоnеnt quiоklу falls as a funсtion of dесrеasе in tеmpегaturе, and it is not
оbsеrvеd in thе spесtгa at Т < z55 K (Fig 4) It has bееn shown еaгliег |52,5з] that thе bгoad
сomрonеnt of the signal fог watеr diminishеs with dесreasе in thе distanсe betwеen the siliсa
paгtiсlеs' It has bееn suggеstеd that it is duе to thе formation of amoгphous modifiсation of
iсе nеaг thе suгfaсе.
------r^\-)
/r 26BK_-\---./А-
/\
/ \ 27ot<
---r.-_/ \-----/ -:.-. -=--'' ::е Unfiо;
Т.hе с
.::'.nglу s9ц
-.'. Foг wеа
^. :rnlal tbг .
.i е nоt Llе
] ] mponеnts
-: sapреaгs aS
.: thе rvatеr l
lаtеriаl. Тhu
.' atеr layег vi
-at thе сhaг;
З00 200 100 0 -100 -200.з00
Chemiсa| Shift (ppm)
300 200 100 0 .100.200 -з00
Chemiсal Shift (ppm)
Fig.4. Dеpеndеnсiеs of 'HNМR spесtra of watеr in frozеn aquеous suspеnsions of Aеrosil
Antttomtеmpегaturе(a)andsolidсоnсеntratiоn(b): 1.А*.= 1Yow/w;2-2%w/w;3-60А
wlw.4 - 2ОoАwlw'
120
з
0
Э
o
6 I 10
мonolаyer (d) Stаtistjcаl Мonoleyeг (d)
е inteгfaсial watегМatеriаl
^G,
G* J,us Ow
Fig.5' ЕtТесt of thе pгеtгeatmеnt pгoсеduге of Aеrosil suгfaсe on a shapе of гadial funсtionоf variatiоn in frее еnеIgv of adsoгbеd ',,u,..
-
Figs 5 and 6 show t'he АG(d) and F(х) graphs foг siliсas diffегеntly prе-tгеatеd.Thеsе gгaphs геflесt thе type of the radial гl,n.iiЫ
';.1i";;;.;йеs in thе frее еnеrgy ofwatег in thе adsсlгption Iayег. Тrr,o segmеnts may bе геvealй on thе Eеpеndеnсiеs oЬtainеd:thе sеgmеnt of a quiсk dесгеasе in ihе thiсknеss оf thе unfгozеn watеr layе. in a naпоwгangе оf the ZG valuе сhanges (tempeгatuгe is about 273 K) аnd thе onе, wheге d dесгеasеsгеlativеlу wеakly in a bгoad.rangе oiсhanges in thе lG vatues. As was shown in sесtion III,thеrе arе wеaНy and stгоnglу bondеd watJгs гespeсtively. Thе totai valuе of thе fтее еnеrgyof thе adsorbеd watег using linеaг dеpendenсеs /G,(d) and АG.(d) maу bе definеd
;;:уi*
to Еq (8) Тhe АG valuеs сalсulаtеd using data shown in Fig. 6 aге summaгizеd in
kJ/mol kJlmol Ys
mI/m2Ant
Ah."
A
A1
.-\{
З'4
J.)
38
J.J
5.з
v.J)
0'з5
u.)
5
4.5
Аt
", 1
8 35
11
IJ
in,
lб0
iooNotе.Unfroz.n*u'
Тhе data givеn in Tablе l show that the сlose valuеs of /G5 and the thiсknеss of thestгonglу bound watег layеr havе bеen obtained foг all the adsoгbents with thе ехсеption of.*L, For wеakiу bound wateг, the thiсknеss of thе l.'.; ;i;;;;tiaпy oгdегеd liquid isтinimal fо.г Ao and maхimal 1' o*, For \, and \ samplеs, the d5, АGn and ygpaгameteгs
1avе nоt Llееn dеtегminеd taking into aссount supегposition of thе narтow and wide]cmponеnts of thе signals (Fig. 5). Thе widе сoйponent oг iье bondеd *.t.._,ignui::sappеars as a funсtion оf гisе in thebulk dеnsity of siiiсa. н";;';;:thе maхimalthiсkness.: the watеrlaуеr struсtuгally oгdегеd bythе suгйое is obsеrvеJЬ" ыlgьt сompaсtion of thе:latегial' Тhus, foг pгaсtiсallу еqual valuеs of Co for \ й \;,"ii..'ьi.tn",s of thе bound..''atег layеr variеs moге than twiсе The dеpеndenсies.obtainej.rnuy ь. explainеd by thе faсt.зt thе сhaгaсtеristiсs of thе watеr lai,еrs struсturally ;,J;;;y йe suгfaсе dеpеnd on
't21
intеrpaпiсlе intегaсtiоn.s Еrimеd stliuа рlaпrсlт:! l;l thе aq'r.!еoi-it, SrlSpсil51ofiS аrе p'еsеnt ln tl1е
form of aggгеgatеS t,uо-sЬJ nin) aild agg1o'n",ut., (.j i рn-,l [54.] ii"rеrе swa'{ns arе not
stablе and еvеn ехрosu;е to nеgiigiьt.."t.,nu"t,?а.io,' t.Ъ sьaьlig оfsuspеnsions) givеs
гisе to dispеrslon as *.it ,o a.naigiroation oг 1i'*i*, Тйе-а'nu;р'пous fогn,t of frоzеn wаtеr
is likе'у to bе foгmеd;;;; ;;;Ы,"p#;i;;;;...,.ь.'*.*n thе pertiс'еs and favorabiе
dimеnsions of thе ,"*ndury, partiсiеs "r
.ь.
^"J,"'ЬЪnt.
Thеrеforе' thе influеnсе of
.the
adsoгbеnt prеtreatmеntH il ',,ййii;l
сha.aсйristiсs should bе tаkеn into aссount wnttе
studуing adsогptiоn ",:йoЬ",.гs
Ъn dispеrsеd matеriats Bу mеans оf modifуing thе
i\
Х (nm)
Fig6.ЕffесtofрI$rеatrnеntоnthегadialfunсtionоfadhеsionfоrсеsforwatеrsuspеnslons
of Aеrosil,
Dгеtrеatmеntсonditionsforthеadsoгbеntonеmaуraгуitsadsorptionсapaсityinar,r.toе
.ans'e oГ vaiuеs тьi,'*iii.'ь"'..un .гг*i.,?n';; ;d."'ptiЬn value of biologiсal
ma;rоmolесulеs' Thе,n-p.."яradial dеpеnd""." "i'ь..dhеsionforсеs
shown in Fig. 6 for
fumеd siliсa in tь. uqu.o.Y, й;;й d'#.,, ,ig;iп.^"iiy iio* simrlаг dеpеndеnсes mеasured
diгесt'у аs forсеs o.,*.."i*" .,o,,.o .уli"d;;;^i;;lijl' ёь.пу fr.om tЬеsе results (Fig. 6)'
thе adhеsion гo,". uuti]".,j;;;;;;;i*rй ri'"."пу,*;;1h; distanсе (not far from thе
surfaсе). At thе samе t,i;.' ;;'йuЪ,ion ь,J.;;;;;;" i*o
"ч1i"q..'s
сhangеs in thе sign at
a short distanсе bеtwееn thеm duе'tо *".1]1;i j.',.u,. in thе liquid laver thiсknеss and сan
bе dеsсгibеd as fottows F : x-n, Whеn., i, ,*;;;;.й;the adsoгbed laуеr thе work is madе
against thе adsorрtronio,".,' and thе u..,u,l,oi'ьi' iuу.' is dеstгovеd' In thе еxpеrtmеnts
o-n г,.., i n g. o ut o f th e ;" й Ь;;; i'. :Ч Т :* t{:kк- ::ЬT't':.}Ё:'Ц
j
i3
l'ж;lп'il.,fl :*:ffi ;.:}1Т{}FitНЁ:::^T::?***:Тi"il3,ii;."*"ii;},J'
mЬlесulеs tуpiсallу in.iJu,", with dесrеаst;;;;;;;of molесulеs in thе interfaсial layеr'
сhаngе in thе sign
",;j;;;;obsеruеd.
on*'ЕunТ'u'l]е that suсh a mеthod (howеvег' as an
indirесt onе) to
".,,**.
,i. *"rk of forсеs ;;.й;;; i"а er'l,is mоrе adеquatе than that
basеd оn diгесt measr]r"*"nt, bеtwееn .*o.i,'iioй, u' u фi"а"r сan сhangе the stгuсturе
of thе intегfa.iur ruyi,-n.u. th. *u,fu." oг-i..ono оnе produсing additional еггors in thе
mеasurеmеnts.
'o".
- Е-_д"t l
l6cъ\ l- ..Aneхl
"" fi\ l-"-on llq0.Ьl i_-}-A* i
1\\
12c.1 A \ a"'11 \ 1
g'rool \\ \
i i\l I Iэ uo] +'\ illi \tL .ol
\\ \ool \.\ \,ol !t-= .q-.+ i
ItE01=---- Е-rA"t l i
t22
:.: iii tilе
э: е not
s givеs
3: ,'vatеr
a ' cгablе
3 cf thе
:: whilе
':
l5:: - .-(ions
: : widе
: . . Jgiсal
lI, 6fоr
J -::sur€d
Ь -g 6)'
!- тthе
!Г': :l$n at
IV.2. Modifiеd siliса аnd Шiхеd окitiеs
N4iхеd oхides aге pгоmisеd matегials to i.tilizе them as сatalysts, polymег fillегs, and
adsorbеnts possеssing surtЪсе Bгиnstеd and Lеwis aсid sitеs. Bеsides this, dispегse paгtiсlеs
oГdust pollutants of industгial and naturаl oпgins aге mostly the miхtuге of poгous and non.
)orous oхidеs Sioz, Alzoз, Tioz, еtс', сontairring сarbon deposits on 1hе suгfaсe, or
;hеmisoгbеd molесulеs of oгganiс сompounds' In atmosphеrе, thеsе paгtiсtеs servе as nuсlei
эf сondеnsation or сrystаllization Гoг watег vapor
'l
o oL'_-=----.=.10 1002фзф4ф50o60о7ф8ф
с.'. (mds)
з o]
l
--l
6 ',.'l
I 1.5r'.J
, ,0.]
\l
\
м6sil
i
\,
\^
!ъ
\ 'э\s
\
\l .-----
i
0 100 2э0 з00 1ф 500 6ф 7ф
с-. (mgs)
€.
е'
Ч
'o
slll
,l
tki
\\\fi\\ш\ l
tхY \
(\*
50 1ф 15о 20о 2ф
c",. (mds)
0 5оo 1оo015002о0@50оз00с6500
с"'o (mу9)
..]d сan
. гnadr
:- ]ПeПtS
'., !G/х
:. watеr
Гig. 7. Dеpеndеncе in changes of adsoгptiоn еnеrgy for pyrogеniс mixеd oхidеs from
. зfrozen watег сonсentгation
In Fig. 7, thеrе aгe shown thе dеpеndеnсiеs of сhangеs in the frее еnergy vеrsus thе
:-rnсеntгation of unfrozen watеr. Thе сhaгaсtегistiсs of thе layегs of watеr adsorbеd on the
.'*rfaсe of thе studiеd samplеs and thе frее surfaсе еnегgy valuеs сalculatеd using Еq. 8 arе
-зргеsеntеd in Тablе 2.
It follows fгom Tablе 2 that foг alumina-siliсa wе have avеrage value of thе suгfaсe
::ее еnегgy bеtwееn valuеs сoгrеsponding individual oхidеs. Foг non-poгous matеrials with a
lrv suгfaсе сonсеntration of altеrnatе сompounds (pyгoсarbon on Sioz; Sioz/A]zoз on
lIo2), wе have a maхimal vaiuе of thе suгfacе frее enегgy. Thе most probablе ехplanation
-fthis faсt is thе polarization ofthе adsогbеnt suгfaое сausеd by сharge ехсhange bеtweеn
::fеrеnt phasеs' As was shown by Dukhin Il8], upon thе appеaгanсе of diffеrently сharged
::еas on thе suгfaсе of dispегsе partiсlеs, therе is a long.гangе сomponеnt of thе suгfaсе
:эгсеs, whiсh сausеd by thе еlесtгostatiс fiеld diгесtеd along thе surfaсe of paпiсlеs. In this
::еld' thе dipоlеs oгwatеr molеоulеs аre undег oriеntation еffeсt. Remotеnеss of this tvpе of
- rvatеr
. iayеr,
: - 3S lltl
..з that
-'r сturе
.n thе
-ts1]lш
-Е!tфз
-FаtюJ+tфlAфз'"1
l
l
{-0.6 t тФ
+1.7 t no2
+5 tт.o2
+ !7 t тio2q-!] xтю2
I z.э
Tablе l Chaгaсtегistiсs of intегfaсial watег on di oхidеs and
Adsorbеnt
lсa
Ys Rеf.
Меthуl siliсa
Alzoз
Sio2+1З%Alzoз
Sio2 + 3o,,o Alzoз
Sio2 + 23oА,ЦzОз
sio2+ 0.5% с
Sio2 + 40% С
Tioz (rutilе)
Sio2 + О.60/0Tioz
SiO2 + 1'TaroTiOz
Sio: * 5"kTiОz
SiOz r l'lohTtOz
Sio2 t Ззo^Tioz
8
lJ )
l0
\2.5
52
25
5
8
95
21 0
1 1.0
4.2
75
20
220
513
2з4
455
248
920
284
Jд| l
449
149"7
428
222
Is8
г5oL"'
t<oL-.
20
12
115
40
1J
5
T7
20
Ise
Ise
[60
[60
161,621
[61]
[61]
[61]
[61]
[6i]
61,62
Notе. Unfrоzеn watеr laуеr thicknеss d is shown in
, .2.mJm
statistiсal monolaуегs; and Ys is in
intегaсtion is dеtегminеd bу thе valuеs of сhaгges and thе distanсе bеtwееn thеm,
Тhis сar.rsеs еn еnhanсеmеnt of thе polarization of adsorbent paпiсlеs and thе appеaranсе оf
the long-rangе сomponеnt оfthе suгfaсе foгсеs. In all thе сasеs, onlу thе surfaсе pоlaгizatiоn
is thе йain iaсtor, whiсh affесts thе thiсknеss of thе adsorbеd watег laуегs. Thе inсгеasе in
thе сaгbon contеnt to 40 ',i,t % геduсеs сhangеs in thе fгeе suгfaсе еnегgy of thе adsorbеnt,
howеvег, it геmains signifiсantlу highеr than that observеd for thе paгеnt siliсa. Additionallу,
thе smallеr thе patсhеs of thе seсond рhasе dеnsеlу graftеd on the suppoгt' thе largеr thе
disoгdeг in thе intегfaсial water, whiсh сausеs grеatеr rеduсtion in its fтее еnегgy.
It should be noted that in thе сasе whеn thе /s valuеs arе govеrnеd only by the
hydrоphiliс propегtiеs of thе surfaсе, onе сan еxpeсt that thе valuеs of thе frее surfaсе
"n.,gy
obtainеd foг thе сarbosils should bе lowеr than thosе obtainеd for thе siliсa. In this
сonйtion, in thе сasе of nonpoгоus adsоrbеnts, a dominant rolе in the formatiorr of thе
struсturizеd intеrfaсial watег layеrs геlatеs to thе tеndеnсy of thе аdsoгbеnt suгГaсе to
undегgo polaгizatiоn in an aqueous mеdium. For poгous adsoфеnts, thе distanсе bеtwеen
сhargБrs on thе suгfaсе is limitеd by thе size of рoгеs. So foг this tуpе of adsoгbеnts
polaiization еffесts arе insignifiсant and intеraсtion with the aquеous mеdium is govегnеd by
thе hуdrophiliс propегtiеs of thе samptеs' Thе сoпеlation bеtwееn thе nanopaгtiсlе struсtuге
and tЬе сйaгaсtегisiiсs of watеr laуегs on thе paгtiсlе suгfaсes may hеlp in еstimаtion of thе
distanсеs of dust pollution tгansfег and iп prеdiсting the еffeсt of dust pollution on the
pгесiрitatiоn lеvеl. Radial dеpendenсiеs of adhеsion forсеs foг sоmе modifiеd and miхеd
охides arе рrеsеntеd in thе Fig 8.
V. Mеsoporous adsоrbents
V.i. Imрасt of hуdrothеrmаl trеatmеnt оп thе surfасе е'lеrgу
аnd аdhеsion foгсеs
Siliсa gеl Si-60 (Мегсk) (spесifiс surfaсe aгеaSвдт =369 m2lg,total poге
-u.oluT..|r
= 0'.753 сm,1g]auеrage poгe radiuslRo = 4.1 nm), Si-40 (Мегсk) (Sвгт] 732
'm"lg,
V,-=^9 5a?
cm'lg, Ro= iiв nmtand si-100 (Мегсk) (Sвдт = 332 mz|g, Vp= 1 l53 сm,/g, Л,^= 6.95-nm)
*",йho,"n as initial matегials foг hydrothermal trеatment (}ITT) at Trrгг = 200 oC rеsulting
124
i1:li{?:t,;T!#',Е:urTТl1i;";t:?ff.i{?ft,-':,.lP, j,'Яj:Тl.*E":
Rr:7.1nm).
Еig. 8. Radial funсtion of adhеsiоn forсеs foг mixеd non-poгous оxidеs.
Struсtuгal fеatuгеs of hydгothеrmally tгеatеd siliсa gels si-40, si.60 and Si-100 wеrе
.'':сidated prеviously [63] Vегtiсal рoгtions of the АG(C'-lgгaphs (Fig. 9a) are obsеrved foг
:-е aquеous suspensions ofjnitial siliсa gеls Si-40 and Si.6O in сontrast to non-poгous
.:soгЬеnts, initial Si-l00 (Fig. 9a) and all hydrothегmally tгeatеd samplеs €i;. ;Б'
::'ssеssing largег poгеs. Appеaranсе of this poпion of АG(С',) is due to unfгozеn intегfaсial
,'atег in narтow poгes with lоwегing tеmpеrature until T сoггеsрonding to a maхimal /G
:iuе for this plot poпion, on thе othеr words, lowеring T Ьvеr some inteгval is not
.:;ompaniеd bу watег frееzing, as this watег is under strong aсtion of thе siliсa suгfaсes in
:Iтow poгеs, whеn elесtrostatiс fiеIds of thе oppositе poге walls stronglу overlap Г64].
Thе сonсentгation.of stгongly bound watеr c* deс'еasеs wiйinс.еasing pore sizе
:,:h foг initial and hydгothеrmallу trеаtеd siliсa gеls (Tablе 3). Thе сonсеntгation-of wеakly
::und water С.u* ts laгgeг for the НTТ samplеs duе tо thе еnhanсemеnt of thе poге sizе;-].'\'еvег, thе гelationships betwееn thе С',*valuеs for difГеrеnt siliсa gеls (initial and нTТj
т'.rе сomp]ех than thosе for С*u (Тablе 3). Notiсе that thе volumе of ttnfrozеn watег (С",+-
..) for FITT-200 samplеs is largеr than thеir рore volumе, maybе due to foгmatlon oitьiiк
,.зtеr layегs on thе outег suгfaсеs оf tгеatеd samplеs' Also, filling of laгge pores by nitгogen
- - зId bе inсomplеtе at pipo: 0'98 (usеd to еstimatе Vo) in contrast to fittiщ by wateг inihе
:: ]еous suspеnsions'
€ z
э
ц
Е :'lume И,
}:.. = О'542
!.=i95nm)
]. ' :еsulting
\м€si|
\
\.
\
'\---...-.
_._0,. t тio2
-A_l?tтio2
-7- l t тю2
+17l rюz
_+_!3 t тю2
125
:-l
l-}qо l
|+Фl i
d
Е
a
'o
10 1
Х (А)
Fig.9.ChangеsinthеGibbsfгеееtiеrgvofthеintегГaсialwatегinthеaquеoussuspеnsions
of initial (a) and irусrotьеrmattу tгеaiеd (b) Si-40' Si-60, and Si-1O0; and сorrеsponding
adhеsion forсes (с, d) anсl derivativеs d(АG),,dСц, as funсiiоn of thе distanсе Х (in A1 from
thе siliсa suгfaсе.
t26
ffx-,;.,'1Тff:и;"ъ"*"d Watег Layeг foг Aquеous Suspеnsions of Siliсa Gеls, Initial
Samplе AG'
kJ/mol ^G"kJ/mol
с*
m
Ys
mJ/m2
;.::lding
i Ггom
si-40
si-60
si- 100
s-40нTT
si.60нTТ
si-100нТT
32
?{
з '25
5.0
4.0
4.0
92
1',72
87
281
з44
l.)
0.8
0.7
0.8
v. t>
570
540
500
300
200
r80
210
250
з20
250
Э1n эz5
Тhe free suгfaсе еnеrgy 15 is maхimal foг Si-60, initial or HTT This rеsult сan bесausеd by sеveгal rеasons, as ihе fгеe suгfaсe еnегgy at thе silica,,watег inteггaсes depеnds onboth thе natuге (е.g', сonсentгаtion of silanols,
"ъ.J" ;ъ;;;; ulo .n. topogгaphy of thеsurfaсеs' HTT for all samplеs leads to inсгеаsе
'l',:
o:1 b' ;1гf;** magnitudes and ДYs(сhaпgеs in /s duе to нTT) is maхimal (2З6 mJ/mz) foг Si.tЬонTi 1тuьt" З). Additionallу,HTТ rеsults in a maгked еnhanсеmеnt oi zG', whiсh сhaгaсteгizes thе fгее enеrgy of the fiгstmonolayeг of adsoгbed watег. This valuе foг НТT
'u'pl;'-i;^,Ё#..ntly greatеr than thatГoг somе othеr matегials invеstigatеd p,"uiou,lу, whiсh .un ь" Еu..to a substantial inсгеasеln thе сonсеntration of silanols (=Si-b-si= + Hlo -+ =SioН + HoSi=) (сonсеntгation ofstlanols foг diffегеnt siliсas in аir сan altег by
-sеvе.гal
timеs t6sfl, сapablе to foгm stгongnydrogеn bonds with watег moleсulеs from thе гrгst h'.;;';.]l;i!Ь, nun,ь., of suсh Ьondspеr a molесulе; i.е , thе numhег of strongly bound watег moleсulеs Тn thе fiгst layeг inсrеasеsfoг HTT samplеs. Howеvег, fог initial
'iii.u t.r'' tьe oppo,li" i.',ii.i- obsегvеd' Notiсе thatt.he F(х) funсtion сorгеlаtеs with inсгеasin* o.o'"' sizе foг HТТ samplеs (Fig 9d), but suсh aсoггelatioп is absent fог initial siliсa g.els фj. яс;. A similaг
"гг..i
iЪ.,..n for thе deгivativеs4(АG),,dС,* vеrsus x (Figs. 9е and gD iь"".aaG)/dc,,u.ru" i, tiЪ analog of thе сhemiсalрotential for isobariс fгееzing of watег. Мaxima or tь. d;й;;;; of 4(АG)/dС'p oП Хсoпespond to the distanсеs fтom thе siliсa surfa.сеs .ьu'..ioиng morе stablе сomplеxеs(сlusters) of the intегfaсial watеr. Тhe position
"iй;.;;;t'"".,f,t, .o*u.d laгgег r with;nсгеasing poгe size for both initial and HТT siliсas (f", I{TT-';йles, thе x valuеs wегесolrrputеd in a model of a flat suгfaсe) тhesе.еttесtJ;;;Ъ;.;;iuln"с ьy thе signifiсantdiflеrеnсеs in thе unfrozen watеI luy..' d"pеnd*'
""
.i..p"*;;;;.;' should bе notеd thattЪr Si-40, the 4(АG)/dC'' maximum.оoгrЁsponds to u *ut..rnonoluy.,, but foг Si.60 andsi-4oнTT, this is З.4 monolayегs, and for si-оo-нтт and Si.I0O-HTT, it is fivе-siх watегтronolayеrs (Fig. 9)'
V.2. Influеп-се ofpyroсarboп on thе аdsorbed wаtеr lаyеr struсturеSi|iсa gеI Si-60 (Sсhu"h:тJ- Мriпсhеn) (SG) was ;;;.;;.paге сarbon-mineгaladsorbеnts by the pyrolysis of CHzCЬ in a siainiй;'..i *".rй [6, ..l at 82зKfoг 0.5,''' 2' З' 4' and 6 h сorrеsponding to difГегеnt CS-l сaгbosil; *iti vaгious amounts ofэyгocarbon Cс (Тablе 4) (synthеsis of thеsе samples was dеsсribed in dеtails еlsеwhereг6б]). sG550 is Si-б0 hеated at 55O.C foг 24 i'
127
Tаblе 4- Struсtural and аdsorption сharaсtегistiсs of adsi.lrbеnts
Оaгbon Carbonizatiоn l'r.,1r, р
'
\p'qеs
Adsorbеnt
[m2/gl Cоntеnt [%l tim9 lhl *_-t!"']€]
^ A nRгl
зlg
[nrn]
SG
scss0
cs-l
CS-2
сs-3
CS-'1
CS.5
Сs-б
з.72
-з44
з66
JJу
299
2s9
ZL.'
163
0
0
О,11
ч эl
14 89
20 з2
/.o i
35 0
0
0
0.5
I
2
з
4
о
080
075
О,|4
0б?
0.56
^^1
0з9
028
43
4.4
4.0
40
1.8
JO
J)
з4
Tablе 5. С.haraсtегistiсs оf 'lratег adsогptiolt laуеrs from thrlI.{NМR cata onthе surfaсе оf
mеscDoгous сaгbоsils
(kJimоl) (mg/g) (kJimol)
520
/JU
zJv
155
225
125
250
i00
SG
SG55O
сSl
с52
cs3
\-JA
CS5
cs6
L.6
35
з0
7.L
4.0
3.C
J)
11
ЭI
J JLI
2iО
3.LV
-r /)
t15
150
22О
J!,JU
I
1.2
.ra
11
l.+
I .,i.
1.8
i 15
150
il0
109
'72
lз9
240
Thе сharaсtеristiсs оfthе rvatеr layеrs асisоrbed on thе сarbosil and initial siliсa gel surfaсеs
dеtеrminеd on thе basis of J.p"nj"n"" s АG(С*) aге pгеsеntеd^in j1в 10. Thiсknеss of thе
Ьondеd watеr lауег (С".) Гor thе weaklу bonJed \vateг and Сu*, for thе stronglу bonded
wateг) as wеll as free suгfaсе еnеrgy (y5J сompared in Тablе 5.
It should bе strеssеd that for pcгous matеrials, the amount of adsoгbеd (unГrozеn)
Watеr сannot bе muсh й;' п;" thеiotal volurnе of thе adsorbеnt poгrs. Therеforе, during
a dесrеasе in thе total fore volume with inсrеasing pуrolуsis time".whiсh rеsults in formation
of pугoсarbon deposit, i,1ь. рo.., and on the ouier sujaсеs of silioa gеl paгtiсlеs, thеrе is a
tеndеncу to dесгеasе thе adsorЬеd watег сonсrntration while passing fiom SG samplеs to
сarbosils, If еffесtivеnеss of сarbonization is small, thеn Сu." and АG" can tlе dеtегmined
quitеadеquаtеlу,butinсasеofothегsamрlеs.thеуhavе,1foгmoГappгoхimation.
Appеaranсе of inflесtions onthe АG(С,.*) grapЪs сan bе сaused bу thе hеtеrogenеitу oГthe
uj*l:ь.nt surГaсеs anсl liпritation of thе pоrе volumе.
. Hydration p,op.*l", of thе adiorb.еnt suгГaсеs at thе adsorbеnt/wetеr intегfaсе саn
bе ехprеssed thе mоstТоmp1еtety thгough the surfaсе frее enеrgу. it follоws ttom the data in
Тablе 5, that /sinсгеases as u rеiutt оf siliсa gеl thеrniallу trеatmеnt frош ll5 mJ/m2 to 1-s0
mJ/mz. Thе initial u"g" of-';li.u su,fu.* сaгbonization .iu'"' a dесгеasе in thе Гrее suгfaсе
еnеrgv lvhегеbу 1s dеJrеаses to 72 mJ/m2 for СS-4 It is in agreеmеnt with thе statеmеnt that
t1iе surfaсе ьуo,ution iio;;;.'--;; Jеtегminеd by thе сonсеntration оf surfaсе silanоls,
r,r,hiсh сan fоrm thе *,Jng.ьуа,.ogеn bonds with waiег molесulеs Adsorрtion sites for watег
оn pугосaгbon dеposits i,е,o*iЛ,еа сaгbоn atоms, whosе сonсеntratiоn is muсh smаllег
128
p
l \p'dе5
-_- [n'ц]
Ч'J
44
4.0
40
38
JO
J]
з4
:han that of SioH gгouрs on tlrе si]iсa sur{aсе; thегеfoге caгbon dеposits should -wеakеn the
rydтophiliс propeгties ofthе hуbrid adsогbеnts' I{owеvег, it is statеd that thеге is an inсгеasе
ln thе adsorbеnt hydгоphiliс pгopепiеs fоr thе samplеs CS-5 and CS.6, whiсh is е'rident in
lhе inсгеasе of thе valuеs /sand (I,.o and for С5-6, 15 is еvеn highег than that foг thе initial
siliсa.
б
Е
I
Ys
(mJlm?)
-*-r 15
150
il0
|з2
109
12
139
240
:tЪсе оf
l= s'lгfaсеs
г...s of thе
в . 'эondеd
-. тozеn)
й-. duгing
E' :nation
ц ..'.ге rs a
';_:lеs to
l:; :::niпеd
Е ::etion.
;'..lf thе
I
0 ,100 2c0 э00 4oo 5o0 600
Unfrozen Wаter сonc (mg/g)
50 1 00 1 50 200 25o зoo
Uлfrozen Wаter оonо, (mg/g)
160
140
120
r
z^^
tЭ
ц 60
140
'120
100
80
40
70
0.
fl F:_?ъзl+\\ l-*сsll
l ?Y |_v_сs5|
il \ l-Fсs6|ы\\
li ?\
\\!\
\$\
J\Y \iЧ l\\ Iъ\.
*
20 2 4 6 810121416182022242628з0
x (A)
.е сan
:rta in
.' I50
.:faсе
: that
:.nоls'
.\ ater
-l зll ег
Fig. l0. Сhangеs in thе Gibbs fгее еnегgу of thе intегfaсial wateг in thе aquеous suspеnsions
эf initial siliсa gеl and mеsopoгоus сaгbosiles and гadial funсtiоn of аdhеsiоn foгсеi for this
зdsoгbеnts.
VI. Мiсroprous mаtеriаls
VI.l. Aсtivatеd саrbоns
Caгbon adsorbеnt PS-O pгoduсеd utilizing рlum stonеs (Wood Dry Distillation
\\.oгks, Hajn6wka, Poland) was usеd es thе initial matегial. PS-0 was subjeсtеd to
rуdrotheгmal modifiсation (нTM) in a stainless stеel autoсlave (0 з L). To prepaгe oxidizеd
adsorbеnts PS-oХl and PS.oХ2, 5 g of PS-0 was plaсеd in a quaгtz thimble to ihe autoсlavе
tt'ith 20 mL of з0 o^ H2o2 and tгеatеd in thе vapoг phasе at 523 К (Ps.oХi ) oг 623 K (Ps.
oХ2) foг 6 h. A rеduсеd adsoгbеnt (Ps-н) was prepared on heating of PS-O in a Hz st,.uй in
a quartz flow гeaсtoг at 1073 K for 8 h t67]
l
I
,,,
l
I
- 2'oi
9l
ts 1,sl
'l
t.0l
I
0.,l
I
\ or i_*сso l\ \ l-v_сssIo Ъ .o l-*сsьI
\ \\\
\\"\
\ \'''
'\
\,1\
T
\\ \--ls_
\"'-{ч
o 2 4 6 810,l214 16 1в202224
129
4.0 г
I
3 5r A l-;*;s; i
I -a* ps-r-i
I
I -v- Ps-ox1 |
[-o--.рs.oxz l
1n-l
j
^-ll'Э !'
-.itr Z,U',
* l.5r/п L
)
'1 Г.l:
n t.l
0,0
20a 400 600 800 1000
Unfгozen Wаteг Conо (mg/g)
Fig" 1l. Сhangеs in thе Gibbs frсе еnегgу of thе intегfасial watеr iп thе aquеous suspеnsions
оf рlumе stonеs
Fig 11 shows.zariatlons in thе fгeе Gibbs еnеrgу as a funсtion of thе сonсеntгatiоn of
unfrozеn *аtег iп thе aquеоus suspеnsions сГthе initiai (сuгvе i). гсduсеd (сuгvе 2),and
oхidizеc сarbоns iсuгv,еs 3 а:ld 4) Т1.,е /G(|'",) gгaрhs ехhibit thе рorticns of thе unfгozеn
rvatег, *'hiсh rепlaiгr nеar сОnstent оvег a rvidе ДG rangе. Тhis еffесt сan Ье сausеd bу watеr
adsorptiоll in miсгoрorеs, аs aссогсiing to thе thеory оf volum.е Гtlling of poгеs [64], thе fгее
"n..gу
of rvatеr irr йiсrороrеs doеs not praсtiсallу deреnd on its loсalization thеre- Adsorbеd
watе-г.сan bе frоzеn rf its fiее еnrгgу bесomеs еqual tо that of iсe at a givеn tеmpеraturе. If
suсh a tеmpеraturе has nоt bееn rеiсhеd, frеeztng ofwatег dоеs not oссuг, and thе unfгozen
watеr сonсеntгation гemains ргaсtiсally unсhangеd. Thе pоrtion оf thе gгaph of lG as a
funсtion of Сu,to thе lеft oГihе vепiсal linе (Fig 12) сoгrеsponds to fгееzing oГwatег in
miсroрoгеs; and that to thе right is assoсiatеd with Watеr in largеr рorеs or wеaklу bound
watег on the outеr suгfaсе оf thе adsorbеnt paгtiсlеs. Thе pоints at thе absсissa
сoп-еsponding to thе vеfliсal iinеs dеtеrminе thе сonсentration of watеr adsorbеd in
miсrоpоrеs (Тablе 6, С,.,,'nP)'
Аs is sееn frоm thе data in Tаblе 6, the frее suгfaсе еnегgy (rs) and сontеnt ot
unfrozеn tvatег (С,.,u,^) dесrеasе foг PS-H' It is in agrееmеnt with thе notion that suсh a
tгеatmеnт rеsults in a jесrеasе in thе surГaсе соnс,еntration of oxidizеd groups, whiсh сan
forпr hуdгogеn-bondеd сlustеIs of watеr mоlесulеs. Additionallу, foг PS.H, a sharp dесгеase
in thе сonсеntтat1on oгwatег adsоrbеd in nriсгороrеs is sеen' Тhis еffесt сan bе ехplainеd bу
]owегing of thе aссеssibility оf miсroporеs ГOг watег rnolесulеs duе to inсгеasе in thе
lзi]
Tablе б. Ctaгaсtегistiсs ofthе inteгfaсial watеr layers in thе fгozеn aquеous suspеnsions of
Adsoгbеnt ЬG,* г ,nqх
c,n
4.2 8to 3Bo 58 1174Ps.н
Ps-oХl
Ps-oХ2
Аa
Ат
А
500
700
I 200
r90
400
650
OJ
t12
I 184
rt62
l20 t
i-:-iIlSlOПS
:t-..зtion of
;. 2), and
:.. lnttozеn
в- :''' watеr
- 'i.о Гrрд
э iJsoгbеd
Е.lаturе. If
:: .rnfrozen
::lGasa
I .. .\'atrr in
в..'.., bound
:: absсissa
r.:. ..гbеd in
Е : ]ntеnt of
l ..:: suсh a
ц . nrсh сan
le.: ]есrеasе
:. : 'rinеd bу
Е:rsе in the
Sample
hуdгophobiс pгopeгtiеs of the adsoгbеnt surfaсеs
1е{uсed by H,. When thе сaгbon suгfaсеsaге tгеatеd with hydгogеn pеroхidе (Ps-oХl, Ps-oХ2), un_in"."u," in thе bound watегсonсеntгation is obsеrvеd in сompaгison with PS-O duЬ to гo,'uiion of additional polaгgгoups, whiсh сan foгm hydrogеn-bonded сompleхеs with water moleсulеs iп miсгopoгеsand on thе outег suгfaсe ofadsoibеnt partiсlеs
VI.2. Adsorbеd wаtеr iп zеolitеs
Zeo|ite samplеs,t6s,69j wегe
-synthеsizеd...aссoгding to the teсhniquе dеsсгibеdэlsеwhеге [70] on thе basis oi fumеd Ъlumina.siliс;'_ .;;i u p.Ь..аu." allowеd us toslmplify thе synthеsis of zеolitеs while alumina-siliсa seгvеd as a souгсe foг foгmation of thеэoth oхidеs in thе zеolitе сrystal lattiсе'
The zеolitеs *.': .Yltl.sizеd using alumina-siliсa with molaг гatios sio2/Al2oззqualto lз1, 100, 26 and l9'5 for pгеpaгatiБn-of samples l .4 (i;l.7), геspесtivеlу. Тhе:эmplate. wаs tetгapropylammonium bгЬmide. In ordег.to p,.pu.. u ,.uсtion mixtuгe, sodium..'rdгoхide and tеmplatе wеге dissolvеd in distillеd watег; ihеil
'JiйI. amount of a'umina-..]iсa was addеd to this solution miхеd' In tегms of oхides thе сomponеnt гatios in thе:raсtion miхtuге wеге as follows: Na2/sio2 = 0.05, t(с3i{'4Nj,o7sБ, = 0'04, H2o/Nд2Q =il0
А Х-гaу diffгaсtion study was made with a DRoN-UМI (LoМo) diffraсtomеtег.sing Ni-filtегed Cu Kс гadiation. Thе сompаrison of
'ь"
>п'о pun",n, of the pгеparеd.:mples with thе literatuгe data on zsМ.s izt1 'ьo*,
that thеsJsamplеs сoггеspond toZSМ-5, whosе dеgгеes.of сгystallinity werе 94 . 96 %. ть.-'p".iл. suгfaсe aгea S was:еasured bу the method of theгmal dеsoгption of argon; tье poгe.volutme V, was detегmined
-stng mеthanoladsoгption isothегms' Thе values obйinеd arЁ listеd in Тablе 7
Тablе 7. Struсtural сhaгaсtегistics of zeolites
1
I
2
J
n
3. 15
7.з8
8.9s
482
чlэ
450
О.26
026
Cдzoэ
wt%
r3l
AsfollowsfromthеdatalistеdinTablе8'thесonсеntrationofwatегadsoгbеdin
zеolitе porеs and ,h. ;.;.;-;i;i"- .n",gу oг '.а*й.*s
(with thе еxсеption of thе samplе
сontaining 3 l5 wt. % ;;;Ыl;;.;;.,ltьll. uь'inum сontеnt. Ai thе samе timе, thе
maximum dеcrеasе i" й;.й;;;ещу in a laуеr of bound watеr is praсtiсallv thе samе foг all
thе studiеd zеolitеs ;^;;;i i*l.Б,u* tu,g. ul;h.";;;;;nJinj"ut"" foi siliсalitе Undеr
thеsе сonditions, the total adsoгbеnt рorе.uoiurn. is filtЁd bу watеr onlv for a samplе at
Cдlzoз = l96 wt%. d;,;;;;j i"Ь*11tv,;J;*;;;;t.;;т.gll. pгеsеntеd in [72] foт
adsorption or *u,.,^ujpЪ;;^;;tй;ч"в-i; thе сonсеntration of Al in thеiг сrystal
lattiсе' Тhе сausе
", 'iЪ1Ьйеd
fеaturеs 'ff # й;;й-^}:tors, nаmеlу сhangе.in the
struсturе оf watег o;i;;;;].;; with inстеasing сonсentratioтr oi A1 and variation .of
сonditions for thе сompеting sorгtioi;|;a|#f й;;ln-ui' к.ыru' in thе situation of a
h,gh;;;;.;:lP::*i;i","j,**н,;JjHHi:j:,""'l'.'НLirЦ.Щ$*#
adsoгption sitеs but. atl
aсiditу is сhaгaсtегts;;;i;;i;?:'.ty:]I^-i'ir
p"ni""
"1-1Plfu'."
йydroхуl groups' yhi*
is еvidеnсеd гo, ьy tiЪ luiu or сalorim.еtriс
. .: lЬ".iiil- witь inоreasing-сonсentгation of
aluminum, tirе сontеnt-oil.i.ь-u.tiu" 9н g'*p,-с*.,Ьu'.', 1nd,.as
a сonsеquеnсе, onе maу
also obsегvе a оесгеasе-in;;;;;", oг"ruЪ,.,Joi*.i.' ".,"r.!]i1s.^.'o'oеd
on thе surtaсе'
Thus, dеspit. tь. in.,.u*е in thе .on..n,*iion"Ъг p,i'u,у 'ч,Р.
watег adsorрtion' thе
еnhanсеmеnt of thе .o*Ъ",iu,ion of aluminum .un Ь. aсоompaniеd with a rеduсtion of thе
;;;;;;ii'dгation of thе zеoiitе surfaсеs.
Tаblе8.CharaсtеristiсsofintеrtЪсialц'atегlaуеrsinaquеOllssuspеnsionsofzеolitеs
Cдrzoз
tviro/o
Сn'"*
-lmgg
AG.U*
kJ mol-l ^{'^-'
0+
1.96
1',I 5
1 1a\
7.38 'Lv
))
250
80
61
61
60
4.8
)'Э
5.0
30
6.0
4.0
эl
6
/.o
l9
858.95
Ifadsorptionofwaterisaffесеdinair,thегеT"y:!Y::'asесondfaсtorthat
affесts thе dependеn.. "iiь.
i.g1.ъ ;1,11111i"" "i
tr.r" suгfaсе.on thе aluminum сontеnt ln a
sample. owing ,o ,t,. p-,.,.n.. Бt ui,, the zеolitе ;;'f*;;" a{s.orb simultanеouslу not onlу
watеr but also molесutеs of nitrogетl .:T:J-fi'i#:J,hi:f .;,j:H'l1ili':::;'"Ц*:
ж*,::rт'il"'ff$*"i}flifii Ёii;{"il. ;;; adsorbеd ргеdominant'у on morе
hvdrophobiс portions 9;Ъ;il;. fri,г in.i."''iй 'и.' "t
ы},l.^': "f
watеr adsorbеd on
;;;;;f *.,;т.::::;j#',i;trj*;;ir#Жii;1;6
,'T'"*:l.;:.ЩJЦ;'':?
valuе of adsorptton or
formatiоn of water.,",;;;;;й ihat оf bеsorpil;.;i;;;;."lесulеs from thе surfaсe. In this
situation, thе Гormatron,oi.*u.., .l::,Y,^.";.lус'."рьiri" ^'],::',.:.'
thе surfaсе maу bе
"n.,g"ti"ыrу',.,:}::;tl:,'lfr ffi"I,:H:;эil}".',..жffi ътЁЩ:'":у
,u1-й. As thе сontеnt ot alumtnuпt-ll:.:;".;;;;
"iu'..,'
iormеd nеaгbу thеsе sltеs mак€
adsorption of watеr ;;,;;.;;;, ьut tь. ;';;;i;;;;,' ф,'.o nеarbv thesе sitеs maкt
contaсt prеdominant'у.*i,ь*iуj,.q|rоьi1ryl;;;
oТlй. ,u,ru.е стеatеd bу siloxanе bгidgеs
As a rеsult, on. .un oь]..u.,." .h;..,tь.l{il**гjж',ill,t"l;::.asе
in the frее suгtaсе
;;;g;;i';"litеs with inсrеasing сontеnt oI ?
bеd in
'4llrРlw
Гoг all
Undеr
rplе at
-21 for
сrystal
: in thе
:ion of
cn ofa
эгlmary
ilе high
i rvhiсh
зtion of
-.']е maу
s:гfaсе.
::..n, thе
::. of thе
:
-2
:гL
VII. Сonсlusions
Тhе fгее surfaсе еnergy of unmodifiеd and modifiеd oхidеs in the aquеous mеdium
may vaгу in thе rangе of l00-1 100 mJ/m2 dеpеnding on thе nature ofthе adsorbеnts, and thе
thiсknеss оfl thе intегfaсial watег distuгbеd by the surfaсеs гangеs fгom 3 to 45 statistiсal
mоnolaуегs. Тhis is сonnесtеd with thе faсt that in aquеous mеdium a high сontгibution of
polaгization and struсtural сomponеnts to measured valuеs of suгfaсе еnегgу is obsеrvеd,
Тhе magnitudе of thesе сomponеnts depеnds not only on thе moгphology and сhеmiсal
struсturе of adsoгbеnt suгfaсеs but also on thе struсturе of intег.paгtiсlе aggrеgatеs as wеll as
on сonсеntгatiоn of a solid phasе in thе aquеous suspеnsion. For this reason for thе samе
п.ratегial, thе thiсknеss of thе laуег of adsoгЬеd watеr may vary dеpеnding on сonditions of
pгеpaгation of thе adsoгbеnt in a widе гangе, The inсгеasе in the thiсknеss оf layеr of
suгfaсе-struсturizеd watеr lеads to a deсгеasе in thе adsorption abilitу of thе adsoгbеnt.
Мaximum values of thе fгeе suгfaсе еnеrgу aге obsегvеd fог samples сharасtеrizеd
bу thе hetегogеnеous suгГaсеs (сaгbosil ha..ing a small amount оf ругoсaгbon dеposits, thе
niхtuге of siliсa with mеthуlsiliсa, amorphous siliсa pгeviously wеttеd) Spесially separatеd
тagmеnts of thе suгfaсеs of thе abovе adsorbеnts aге оharaоtегizеd by diffеrent valuеs of
dissoсiation сonstants ofthe surfaсe hydгoхyl gгoups and bу diffегеnt affinitiеs t0 protons
.{t the samе timе a polaгization of thе adsorbent suгГaсе tаkе plaсе, It саn be assumed that
:hе thiсknеss of thе laуег of adsoгbed watеr is stгonglу affесted bу thе surfacе сhargе
:rstгibution nonuniformitу сonnесtеd with apреaranсе of oppositеlу сhaгgеd fragmеnts' and
:rе fiеld сrеatеd bу thesе fragmеnts influеnсеs thе oriеntation of dipolеs of watег molесulеs.
Тhе appeaгanсе ofsuгfaсе сhaгgеs is also possiblе in thе zonеs ofintегрaгtiсle сontaсts' Fоr
:ris rеason in thе сasе of low,disреrsion matеrials, thе values of thе fгеe suгfaсе enегgу and
.aуег thiсkness of adsoгbеd wаtег in thе aquеous suspensions aге not dеtегminеd bу
:r'drophiliс-hydгophobiс pгopепiеs of thеsе matеrials but by сaрability of thе suгfaсе to
: olaгization,
Thе maхimum laуеr thiсkness fоr watеr adsoгbеd in poгous adsoгbents сannot
.lbstantiallу еxсееd thеiг pоrе гadius' Theгеfоге, whеn thе aсtion гadius for suгГaсе foгсеs is
sзallег than thе poге raditts, the laуеr thiсknеss foг watег adsoгbеd on thе surfaсе is
-;cvеrnеd mainly by thе surfaсе сonсеntration oГhуdrophiliс sites. If the surfaсe pоtentials of
:hе oppositе wails of a porе ше ovегlappеd, all thе watеr filling thе poгe is bound to thе
.':гfaсes' Thе fгееzing tеmpеraturе for wаtег in suсh a porе is govегnеd by thе poге sizеs and
:эгсе of intеraсtion bеtwеen thе surfaсе and watег. Thе frее suгfaсе еnеrgy value mеasuгеd
:tг suсh adsoгbеnts dеtегminеs the intеnsitу of intеraсtions bеtwееn watеr molесulеs and
: эге suгfaсе' In thе сasе of сhemiсally modifiеd сarbonaсеous adsoгbеnts the сompaгison
]еtwrеn valuеs of thеir frее suгfaсе еnеrgiеs in an aquеous medium makеs it possiblе to
:эtain valuablе infoгmation on thе сonstitution oГthеiг suгfaсе.
Rеfеrеnсes
. Kinnеy, D.R, Chaunc I-S , Мaсiel G.F Watеr and thе Siliсa Surfaсе As Studiеd by
Vaгiablе Теmpеratuге High Rеsolution 'Н N.'\,IR // I. Am. Chеm' Soс. _ 1993. - v. l15,
N r5 - P.6'786-6794.
i Chung I.S , Мaсiеl G.Е' Pгоbing Hydгogеn Bouncing at thе Loсal Еnvironment of
Silanol Suгfaсеs via Nuсlеaг Spin Сross Polaгization Dynamiсs ll J, Аm. Chеm. Soс. -
1996.- V. 118,N2. -P. 401-406.
. Сhang I-S .Кinnеу D R., Мaсiel G Е Inteгior Hvdroxуl of thе Siliсa Gеl systеm as
Studiеd by ,,Si сP-МAs NМR Spесtгosсopy ll J Ьm Chеm. Soс - 199з. V 115, N 19
- P 8695-8705.
;
r.,:еnt in a
i. rot onlу
р:,.эondеd
::] morе
ш.*:i.bеd on
в lhеn thе
в ::.еrgy of
t;: In this
в maу bе
в...
..S of this
r sitеs foг
} : ::s makе
f.. эгidgеs.
t*.. suгfaсе
I J-l
4StudуofСonstitutivеSupeгГrсialWatе^r^оfPrесipitatеdAmогphousSiliсasusing.H
NN{R, Broad-Linе at цi ano МAS at 300 K / C. Doгеrniеux-Моrin, L. Hеегibout, C.
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V. 118, N 6. _ P. 1304-lз45
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J Сhеm soс., гaraauу Тrans, - isss _ v 9l' N l0. _ P.15|9..|522
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Kampсz.vk. J Ku,;t;"ё.,o ir
,нo^.к'
p, iii"ьЪs, B i{'оhl.Kuhn /i J. Соlloid Intегfaсе
sсi. - tgsз _v йs }i 2 _Р' -io6.з7i.
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1з.
P
;,".#;'.;'- \, . L]huтаеv }i \, . V N4lv{uilсr. SuгtЪсе Forсеs. Nеrv Yогk, Consultants
,- il:ix},|Y, 3]u,l ."u-ll:.PA Rесеnt Dеvеlopmеnts in titе Mеasuгеmеnt of
Irrtегpariсlе гo,"J* z7дo' с"iьiо rnt..й"е s.' -'.'?n]...l.'i;.1o' N 2 - P. 18з-240
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_вtI*.,,
of Suгfасе Hеtеrogеnitу'cf oхidеs in Simptе Ion
Adsoгptron "t
o;;.ь];.i.olitе rnt.,гu.Jji'дЪ1o,ptionl_ ,gв - v 2' N з. _P 245.
255
16N{еaghеrL,,РashiеуRМ.ТhеlntеraсtionFоrсеsbеtwееn-SiliсaandPlasma.Tгeatеd
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',
),,J3.';,)"3 ;- i'i.",.?jeсtгiсal.T:"hu:i:1n.:I '"l":jч"i,;".]}'iyffifl';: '"
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|
| id | oai:ojs.pkp.sfu.ca:article-52 |
| institution | Surface |
| keywords_txt_mv | keywords |
| language | English |
| last_indexed | 2025-09-24T17:44:38Z |
| publishDate | 2001 |
| publisher | Chuiko Institute of Surface Chemistry National Academy of Sciences of Ukraine |
| record_format | ojs |
| resource_txt_mv | surfacezbircomua/12/9907b2ce4728e3f79b4a00f55bdb0c12.pdf |
| spelling | oai:ojs.pkp.sfu.ca:article-522018-11-27T09:42:39Z A new method for determination of free surface energy and adhesion forces. Highly dispersed oxides, mesoporous and microporous materials A new method for determination of free surface energy and adhesion forces. Highly dispersed oxides, mesoporous and microporous materials A new method for determination of free surface energy and adhesion forces. Highly dispersed oxides, mesoporous and microporous materials Turov, V. V. Gun'ko, V. M. Leboda, R. Brei, V. V. A new method of determination of the Gibbs free surface energy and the radial dependence of adhesion forces of adsorbents in respect to the interfacial water was developed on the basis of measurements of the dependence of NMR signal intensity of unfrozen water on temperature at T &lt; 273K. It was considered features of application of this method to highly disperse oxides, modified oxides, microporous and mesoporous adsorbents. The free surface energy values are computed for a variety of oxide and carbon-mineral materials. A new method of determination of the Gibbs free surface energy and the radial dependence of adhesion forces of adsorbents in respect to the interfacial water was developed on the basis of measurements of the dependence of NMR signal intensity of unfrozen water on temperature at T &lt; 273K. It was considered features of application of this method to highly disperse oxides, modified oxides, microporous and mesoporous adsorbents. The free surface energy values are computed for a variety of oxide and carbon-mineral materials. A new method of determination of the Gibbs free surface energy and the radial dependence of adhesion forces of adsorbents in respect to the interfacial water was developed on the basis of measurements of the dependence of NMR signal intensity of unfrozen water on temperature at T &lt; 273K. It was considered features of application of this method to highly disperse oxides, modified oxides, microporous and mesoporous adsorbents. The free surface energy values are computed for a variety of oxide and carbon-mineral materials. 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/52 Surface; No. 4-6 (2001): Chemistry, Physics and Technology of Surface; 112-137 Поверхность; № 4-6 (2001): Химия, физика и технология поверхности; 112-137 Поверхня; № 4-6 (2001): Хімія, фізика та технологія поверхні; 112-137 3154-8091 3154-8083 en https://surfacezbir.com.ua/index.php/surface/article/view/52/51 Авторське право (c) 2001 V.V. Turov, V.M. Gun’ko, R. Leboda, and V.V. Brei |
| spellingShingle | Turov, V. V. Gun'ko, V. M. Leboda, R. Brei, V. V. A new method for determination of free surface energy and adhesion forces. Highly dispersed oxides, mesoporous and microporous materials |
| title | A new method for determination of free surface energy and adhesion forces. Highly dispersed oxides, mesoporous and microporous materials |
| title_alt | A new method for determination of free surface energy and adhesion forces. Highly dispersed oxides, mesoporous and microporous materials A new method for determination of free surface energy and adhesion forces. Highly dispersed oxides, mesoporous and microporous materials |
| title_full | A new method for determination of free surface energy and adhesion forces. Highly dispersed oxides, mesoporous and microporous materials |
| title_fullStr | A new method for determination of free surface energy and adhesion forces. Highly dispersed oxides, mesoporous and microporous materials |
| title_full_unstemmed | A new method for determination of free surface energy and adhesion forces. Highly dispersed oxides, mesoporous and microporous materials |
| title_short | A new method for determination of free surface energy and adhesion forces. Highly dispersed oxides, mesoporous and microporous materials |
| title_sort | new method for determination of free surface energy and adhesion forces. highly dispersed oxides, mesoporous and microporous materials |
| url | https://surfacezbir.com.ua/index.php/surface/article/view/52 |
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