1
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In e ac ion o Hyd a ed Ca ions wi h Mica-n (n=2,
3 and 4) Su ace.
Espe anza Pa ón1,*, Miguel A. Cas o2, Agus ín Co a3, F ancisco J. Osuna2, M. Ca olina
Pazos4, Ma ía D. Alba2
1 Uni é de Ca alyse e de Chimie du Solide, UCCS, CNRS, UMR8181, Uni e si é Lille No d
de F ance, 59655 Villeneu e d’Ascq, F ance
2Ins i u o Ciencia de Ma e iales de Se illa (CSIC-Uni e sidad de Se illa). A da. Amé ico
Vespucio, 49. 41092 Se illa, Spain.
3Labo a o io de Rayos-X. CITIUS. Uni e sidad de Se illa. A da. Reina Me cedes, 4b.
41012-Se illa, Spain.
4 Escuela de Ciencias Químicas, Uni e sidad Pedagógica y Tecnológica de Colombia UPTC.
A da. Cen al del No e, Vía Paipa, Tunja, Boyacá, Colombia.
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ABSTRACT.High cha ged swelling micas, wi h laye cha ge comp ised be ween 2 and 4,
has been ound o eadily swell wi h wa e and ha comple e ca ion exchange (CEC) can be
achie ed. Due o hei high CEC, applica ions like adioac i e ca ion ixa ion o emo al o
hea y me al ca ions om was e wa e we e p oposed. Thei applicabili y can be con olled by
he loca ion o he in e laye ca ion in a con ined space wi h a high elec ic ield. In syn he ic
b i le micas, he in e laye ca ion has a low wa e coo dina ion numbe ; he e o e hei
coo dina ion sphe e would be comple ed by he basal oxygen o he e ahed al laye as inne -
sphe e complexes (ISC). Howe e , no di ec e idence o hese complexes o ma ion in b i le
micas has been epo ed ye . In his con ibu ion, we mainly ocus on he unde s anding he
mechanisms ha p o oke he o ma ion o ISC in high cha ge swelling micas, Mica-n. A
whole se ies o ca ions (X) we e used o explo e he in luence o he cha ge and size o he
in e laye ca ion. Th ee b i le swelling micas, Mica-n (n=4, 3 and 2), we e selec ed in o de
o analyze he in luence o he laye cha ge in he o ma ion o ISC. The con ibu ion o he
ISC has been analyzed ho ough he e olu ion o he 060 e lec ion and he changes in he
sho - ange o de o he e ahed al ca ions will be ollowed 29Si and 27Al MAS-NMR.The
esul s showed ha ISC was a o ed in X-Mica-4 and ha p o oked a high dis o ion angle
be ween he Si-Al e ahed a. When he con en o aluminum dec eases, he elec os a ic
o ces be ween he laye s a e elaxed, and he hyd a ed ca ions did no in e ac so s ongly
wi h he e ahed al shee , ha ing he oppo uni y o comple e hei hyd a ion sphe e.
KEYWORDS. High-cha ged micas, inne sphe e complex, hexagonal ca i y, e ahed a
dis o ion, NMR, b-pa ame e .
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TOC GRAPHIC
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4
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INTRODUCTION
High cha ge swelling micas, wi h laye cha ge comp ised be ween 2 and 4, has been ound
o eadily swell wi h wa e and ha comple e ca ion exchange (CEC) can be achie ed.1,2,3,4,5,6,7
Due o hei high CEC ( heo e ically up o 468 meq/100g), applica ions like adioac i e ca ion
ixa ion o emo al o hea y me al ca ions om was e wa e we e p oposed.8,9,10,11,12,13
In hose high cha ged syn he ic micas, he laye s bea a high pe manen nega i e cha ge
compensa ed by coun e ions loca ed be ween hem (in e laye space). These coun e ions a e he
o igin o wo in e es ing ea u es: mica swelling and ca ionic exchange. The o me e e s o he
up ake o wa e in o he in e laye space, while he la e in ol es he eplacemen o o iginal
coun e ions Na+ by ca ions o aqueous solu ion.14,15,16,17 Bo h p ocesses will be con olled by he
loca ion o he in e laye ca ion in a con ined space wi h a high elec ic ield.
Recen ly, wo impo an i ems ela ed o hese swelling b i le micas ha e been epo ed 1)
he in e laye ca ions do no exchange comple ely.18 2) The wa e coo dina ion o he ca ions is
small o ull ill hei hyd a ion sphe e.19
The hyd a ion s a e o he in e laye ca ions has been shown o depend on bo h he laye
cha ge o he aluminosilica e and he na u e o he in e laye ca ion.19 In syn he ic b i le micas,
he in e laye ca ion has a low wa e coo dina ion numbe ; he e o e hei coo dina ion sphe e
would be comple ed by he basal oxygen o he e ahed al laye as inne -sphe e complexes (ISC).
This ac has been ound as well in he hec o i e su ace, whe e weakly sol a ed ions, such as K+,
a e able o o m ISC.20 Howe e , no di ec e idence o hese complexes o ma ion in b i le micas
has been epo ed ye .
In his con ibu ion, we mainly ocus on he unde s anding he mechanisms ha p o oke
he o ma ion o ISC in high cha ge swelling micas, Mica-n. In e ms o me hodology, we d aw
a en ion o he ela ion be ween he hexagonal hole in he e ahed al laye and he in e laye
ca ion, which allows de ailed unde s anding o bo h he con ined ca ion and he clay su ace
s uc u e. Then, a whole se ies o ca ions will be used o explo e he in luence o he cha ge and
5
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size o he in e laye ca ion. Th ee b i le swelling micas, wi h di e en Si/Al a io, we e selec ed
in o de o analyze he in luence o he laye cha ge in he o ma ion o ISC. The con ibu ion o
he ISC will be analyzed ho ough he e olu ion o he 060 e lec ion and he changes in he sho -
ange o de o he e ahed al ca ions will be ollowed 29Si and 27Al MAS-NMR
EXPERIMENTAL
Syn hesis Me hod
A p ocedu e simila o ha desc ibed by Alba e al.21 was employed. Nea -
s oichiome ic powde mix u es wi h he mola composi ions (8 - n) SiO
2, (n/2) Al2O3, 6
MgF2, and (2n) NaCl we e used o syn hesize Na-Mica-n (n = 2, 3, 4). The s a ing ma e ials
we e SiO2 om Sigma (CAS no. 112945-52-5, 99.8% pu i y), Al(OH)3 om Riedel-de Haën
(CAS no. 21645-51-2, 99% pu i y), MgF2 om Ald ich (CAS no. 20831-0, 98% pu i y), and
NaCl om Pan eac (CAS no. 131659, 99.5% pu i y). All eagen s we e mixed and igo ously
g ounded be o e hea ing up o 900 °C in a P c ucible o 15 h. A e cooling, he solids we e
washed wi h deionized wa e and d ied a oom empe a u e. The as-syn hesized samples a e
named Na-Mica-n (n anging be ween 2 and 4). XRF analyses we e ca ied ou in o de o
check he chemical composi ion o hese samples (see “Sample Cha ac e iza ion” session o
acquisi ion de ails). The esul s a e displayed in Table 1, as well as he Si/Al a io achie ed
compa ed wi h he heo e ical alue. A good accu a e is ob ained and allows us a i ming ha
chemical composi ions o hese samples a e close o he heo e ical one. The as-made solids
we e analyzed by X- ay Di ac ion (XRD) o e alua e hei pu i y (Figu e 1S, Suppo ing
In o ma ion).
Ca ion-Exchange P ocess
The as-syn hesized Na-Mica-n we e exchanged wi h solu ions o Li+, K+, Mg+2 and
Al+3 sal s a concen a ions ha ensu ed ha he mola amoun o ca ion was 10 imes he
ca ion-exchange capaci y (CEC) o he mica.19 The mos impo an cha ac e is ics o hese

6
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ions in solu ion a e displayed in Table 2. The eagen s used we e MgCl2 om Sigma-Ald ich
(CAS n° 7786-30-6, 99.99% pu i y), KCl om Fluka (CAS n° 7447-40-7, >99% pu i y),
AlCl3 om Fluka (CAS n° 7784-13-6, >99.0 % pu i y), and LiCl om Fluka (CAS n° 7447-
41-8, >99.0% pu i y). Ion-exchange p ocess was desc ibed elsewhe e.19 The esul ing solids
we e analyzed by X- ay Di ac ion (XRD) o e alua e he pu i y o he samples (Figu e 2S,
Suppo ing In o ma ion). This exchange me hod p e en s he modi ica ion o he silica e
amewo k and consequen ly, XRF analyses we e no needed. The ex en o he ca ion
exchange eac ion was moni o ed by 23Na MAS- NMR. These solids a e e e ed o as X-
Mica-n, whe e X=Na+, Li+, K+, Mg+2, o Al+3 and n=2, 3, o 4.
Sample Cha ac e iza ion.
X- ay di ac ion (XRD) pa e ns we e measu ed a he CITIUS X- ay labo a o y
(Uni e si y o Se ille, Spain) using a B uke D8 Ad ance ins umen equipped wi h a Cu Kα
adia ion sou ce, ope a ing a 40 kV and 40 mA, and wi h a Ni il e . The powde XRD
pa e ns we e egis e ed in he 2θ- ange 58–62° wi h a s ep size o 0.05° and a ime s ep o 20
s. The analysis o he peaks we e ca ied ou using TOPAS© om B uke © and Pseudo oigh
unc ions.
XRF o powde ed samples in bo a e lux was pe o med o ob ain in o ma ion abou
he chemical composi ion o he samples. XRF measu emen s we e made wi h an au oma ed
Philips PW1400 spec ome e a he CITIUS, Uni e sidad de Se illa.
29Si and 27Al (SP) MAS-NMR spec a we e eco ded a he Spec oscopy Se ice o
ICMS (CSIC-US, Se ille, Spain) using a B uke DRX400 spec ome e equipped wi h a
mul inuclea p obe. Powde ed samples we e packed in 4-mm zi conia o o s and spun a 10
kHz. 29Si MAS-NMR spec a we e acqui ed a 79.49 MHz, using a pulse-wid h o 2.7 μs
(π/2=7.1 μs) and a pulse space o 3 s. 27Al (SP) MAS-NMR spec a we e eco ded a 104.26
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MHz, using a pulse wid h o 0.92 μs (π/2=9.25 μs) and a pulse space o 0.1s. The chemical
shi alues a e epo ed in ppm wi h espec o e ame hylsilane o 29Si and AlCl3 0.1M o
27Al.
RESULTS AND DISCUSSION
Hexagonal ca i y dis o ion: b pa ame e
In all he samples, he 060 e lec ions (Figu e 1) a e in he 2θ ange be ween 59.5 o
60.2º which is ypical o ioc ahed al clays22 and he 2θ alue depend on he in e laye ca ion
(Table 2).
The dis ance associa ed o his e lec ion, d(060), (Table 2) depends on he composi ion
o he oc ahed al shee , he amoun o Al in e ahed al shee and he deg ee o e ahed al il
angle.22 Fo hese easons, ioc ahed al clays like saponi e and e miculi e exhibi a highe
alue (1.52 and 1.54 Å, espec i ely) han dioc ahed al clay such as mon mo illoni e (d(060)
=1.49-1.50 Å). The alues ob ained o ou samples anges be ween 1.50 o 1.56 Å. The
bigges alues, ound o he highes cha ge micas (n=4 and 3), a e close o he alues
epo ed o e miculi es, whe eas o n=2, d(060) is in he epo ed alue o ioc ahed al
micas, like Bio i e (1.538 Å).
Geome y conside a ions can be de i ed om he 060 e lec ion (Table 2). Fo mos o
he laye ed silica e, he ideal hexagonal ca i y (Figu e 2a) is dis o ed o a di igonal
symme y by he oppose o a ion o al e na e e ahed on (Figu e 2.b). The amoun o his
o a ion a ies om a ew deg ees o nea he heo e ical maximum o 30º. This e ahed al
o a ion has been a ibu ed o he di e ence in size be ween he e ahed al and oc ahed al
shee s ( he i s one is highe han he second).23,24 The a e age e ahed al o a ion om
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hexagonal symme y, α, may be p edic ed om he obse ed b axis and he known Al- o -Si
subs i u ion as:22
cos 
 (1)
whe e b heo is he alue ob ained om25 󰇛󰇜9.150.74,󰇗, (x is he heo e ical
g ade o subs i u ion o Si4+ o Al3+ in he e ahed al shee ) and bobs is he expe imen al alue
calcula ed o m d(060) dis ance, aking in o accoun ha in monoclinic cells, b=6· d(060), Å.
F om he expe imen al d(060) alues and he sample chemical composi ions, he
dis o ion angle, α and b pa ame e we e calcula ed (Table 2) and ha e been co ela ed o he
in e laye ca ion size (Figu e 3).
The maximum dis o ion is ound o he samples wi h he highes isomo phical
subs i u ion Si/Al and hence, highes laye cha ge (uppe blank iangle, Figu e 3). This
beha io is a consequence o he inhibi ion o he inco po a ion o he wa e molecules o he
in e laye space when laye cha ge inc ease.19 In such case, he in e laye ca ions a e less
hyd a ed and inc ease he con ibu ion o inne sphe e complex. As obse ed in he Figu e,
he dis o ion c ea ed inc eases wi h he inc ease in he ionic adii o he in e laye ca ion,
meaning ha in his case, whe e ISC a e a o ed o occu , he adii o he in e laye ca ion is
he pa ame e ha in luence in he g ade o dis o ion p oduce in he laye . The sample
homoinized by K+ is he only excep ion in his beha io . This case will be analyzed u he in
he ollowing sec ion (see 29Si NMR).
On he opposi e si e, when laye cha ge dec eases, he elec os a ic in e ac ion be ween
he laye s is elaxed and allows he hyd a ion o he in e laye ca ions.19 This ac hinde s he
con ibu ion o inne sphe e complexes and consequen ly, smalle dis o ion in he e ahed al
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shee a e expec ed as occu ed o samples n=3 and n=2. In his case, he in luence o he
ionic adii in he dis o ion is smalle .
In X-Mica-n, he in e laye ca ions a e housed in he hexagonal ca i ies o med by he
O2- anions o he opposi e e ahed al shee s (Figu e 2c). The e o e, dis ega ding dis o ions,
hese ca ions ha e 12- old coo dina ion, and he bond leng h be ween oxygens and in e laye
ca ions, d, can be calcula ed h ough he equa ion:

 (2)
whe e h is he in e laye space, h=d001-9.4, Å and is de dis ance om he cen e o he
hexagonal ca i y o he oxygens o he plane in a e ahed al shee . In case o he e ahed al
shee s de o ma ion by o a ion o angle α, a ies as ollows:26
 


√3 an (3)
Bond dis ance be ween he basal oxygens and he in e laye ca ions calcula ed using
eq. 2 a e also displayed in Table 2. To de e mine hese pa ame e s he in e laye space is
equi ed (calcula ed using he d001 dis ance, Table 2).19
The dis ance be ween he basal oxygens and he cen e o he hexagonal ca i y, ,
sligh ly di e s om he expec ed ange (2.6 Å)27. Sho es dis ances a e ob ained when n=4,
and he p esence o ISC is encou aged. Howe e , when laye cha ge dec eases, his dis ance
inc eases e lec ing he smalle dis o ion p o oked by he in e laye ca ions, al hough i ne e
a i es o he ideal alue.
The dis ance be ween he in e laye ca ion and he basal oxygens (d) when a
monolaye o wa e is conside ed24 (d001≈12Å) ange be ween 2.6 and 3.4 Å. In he case n=4,
he dis ance is smalle (be ween 2.6 and 3.08 Å) indica ing ha hexagonal ca i ies a e
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(29) Mackenzie, K.J.D.; Smi h, M.E. Mul inuclea Solid S a e NMR o Ino ganic Ma e ials.
Else ie Science L d, Ox o d, 2002.
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phyllosilica es. J. Ame . Chem. Soc. 1984, 106, 4790-4793.
(31) Weiss, C.A.; Al ane , S.P.; Ki kpa ick, R.J. High- esolu ion 29Si NMR spec oscopy o
2:1 laye silica es: co ela ions among chemical shi s, s uc u al dis o ions and chemical
a ia ions. Am. Mine . 1987, 72, 935-942.
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phases and Al-Si dis ibu ion du ing Na-4-mica syn hesis. J. Phys. Chem. C 2011, 115,
20084-20090.
(33) Shannon, R.D.; P ewi , C.T. E ec i e ionic adii in oxides and lou ides. Ac a C ys al.
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(34) Thompson, J.G. 29Si and 27Al nuclea magne ic esonance spec oscopy o 2:1 clay
mine als. Clay Mine . 1984, 19, 229-236.
(35) Pea son, R.G. Ha d and so acids and bases. J. Am. Chem. Soc. 1963, 85, 3533-3539.
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Chem. Educ.1968, 581-586.
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Chem. Educ.1968, 643-648.
(38) Shainbe , I.; Kempe , W.D. Ion exchange equilib ia on mon mo illoni e. Soil Sci. 1967,
103, 4-9.
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and MgO: cha ac e iza ion and S +2 up ake kine ics. J. Ma e . Chem. 1988, 8, 205-208.
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(41) T illo, J.M.; Alba, M.D.; Al e o, R.; Cas o, M.A. Rexpansion o collapsed Li-
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Table 1. Elemen al quan i ica ion ob ained by XRF analysis o he h ee ini ial
samples.
%
Na
(±0.09)
Al
(±0.4)
Mg
(±0.06)
Si
(±0.09)
F
(±0.3) Si/Al
Si/Al
heo
Na-Mica-4 7.95 6.1 17.10 18.95 13.5 1.04 1
Na-Mica-3 9.46 9.0 16.75 15.67 14.3 1.74 1.68
Na-Mica-2 9.46 12.4 17.30 12.91 11 3.1 3
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Table 2. Physicochemical p ope ies o ca ions. ep esen s he Pauling
ionic adius, q/ is he ela ion be ween he ionic cha ge and ionic
adius. ΔH0hyd is he hyd a ion en halpy and pKa is he acidi y
cons an .
K+ Na+ Li+ Mg+2 Al+3
(Å) 1.33 0.95 0.6 0.65 0.5
q/ 0.75 1.05 1.70 3.08 6.00
ΔH0hyd(KJ/mol) -305 -406 -519 -1922 -4660
pKa 14.5 14.2 13.6 11.4 5.0
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Table 3. 060 and 001 plana dis ance, b-pa ame e , dis o ion e aed a angle (α) and ca ion-basal
plane dis ance o X-Mica-n.
Ca ion (X) 060/2θ d060 (Å) d001(Å) bobs(Å) α (Å) d(Å)
X-Mica-4
Li+ 59.75±0.01 1.55±0.01 11.96±0.02 9.28±0.05 13.92±0.02 2.30±0.05 2.63±0.05
Na+ 59.99±0.01 1.54±0.01 12.17±0.01 9.25±0.04 14.71±0.02 2.26±0.03 2.65±0.03
K+ 59.33±0.02 1.56±0.03 12.83±0.02 9.30±0.20 12.33±0.08 2.40±0.20 2.90±0.10
Mg+2 59.84±0.02 1.54±0.03 12.06±0.02 9.30±0.20 14.23±0.09 2.30±0.20 2.60±0.20
Al+3 59.69±0.01 1.55±0.02 13.50±0.02 9.30±0.10 13.50±0.02 2.30±0.10 3.08±0.08
X-Mica-3
Li+ 59.80±0.01 1.55±0.02 12.13±0.02 9.27±0.09 10.60±0.04 2.29±0.09 2.80±0.30
Na+ 59.97±0.01 1.54±0.02 12.17±0.01 9.30±0.10 11.31±0.04 2.36±0.09 2.74±0.08
K+ 59.45±0.06 1.55±0.08 12.80±0.04 9.32±0.50 8.80±0.20 2.50±0.50 3.00±0.40
Mg+2 60.06±0.03 1.54±0.05 14.27±0.02 9.20±0.30 11.80±0.10 2.40±0.30 3.40±0.20
Al+3 60.06±0.05 1.54±0.07 14.05±0.04 9.20±0.40 11.70±0.20 2.40±0.40 3.30±0.30
X-Mica-2
Li+ 60.34±0.02 1.53±0.03 12.11±0.03 9.20±0.20 8.80±0.10 2.40±0.30 3.40±0.20
Na+ 60.36±0.01 1.53±0.02 12.17±0.01 9.20±0.20 8.90±0.07 2.40±0.10 2.80±0.10
K+ 60.02±0.07 1.50±0.10 12.86±0.02 9.20±0.60 6.70±0.60 2.00±0.10 3.10±0.10
Mg+2 60.13±0.02 1.54±0.03 14.34±0.03 9.20±0.30 7.20±0.20 2.50±0.30 3.50±0.20
Al+3 60.21±0.06 1.50±0.10 13.94±0.02 9.20±0.30 8.00±0.40 2.40±0.70 3.30±0.50
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FIGURE CAPTIONS
Figu e 1. X- ay di ac ion diag ams in he ange o he 060 e lec ion. As e isks ep esen
he peak used in he ollowing calcula ions (Table 2).
Figu e 2. a) P ojec ion o he ab plane o he e ahed al shee . Con inuous line ep esen s he
B a ais uni cell and he discon inuous line ep esen s he p imi i e cell. b) Te ahed al shee
dis o ion due o he α- o a ion o adjacen e ahed a. c) Dis ance be ween he apical oxygens
and he in e laye ca ions.
Figu e 3. Dis o ion angles calcula ed om he b pa ame e ob ained om he 060 e lec ion
e sus he in e laye ca ion adius. Squa es= X-Mica-4, ci cles = X-Mica-3 and iangles= X-
Mica-2.
Figu e 4. 29Si MAS-NMR spec a o X-Mica-n as a unc ion o he laye cha ge (n) o he
alkaline in e laye ca ions: a) Li+, b) Na+, and, c) K+. Q3(mAl) en i onmen s a e ma ked wi h
*
Figu e 5. 29Si MAS-NMR spec a o X-Mica-n as a unc ion o he laye cha ge (n) o he
hi d pe iod in e laye ca ions: a) Na+, b) Mg2+, and, c) Al3+. Q3(mAl) en i onmen s a e
ma ked wi h *
Figu e 6. 29Si chemical shi alues ob ained om he i o he spec a o he Figu es 4 and 5
in unc ion o he in e laye ca ion adius. Q3(mAl) m=3, 2, 1 and 0 a e ep esen ed by
squa es, ci cles, uppe iangle and downe iangle espec i ely, and a e sepa a ed by do
lines. Solid symbols=X-Mica-4, c ossed=X-Mica-3 and open=X-Mica-2.
Figu e 7. 27Al MAS-NMR spec a o X-Mica-n.
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Figu e 1
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EXPERIMENTAL
Sample Cha ac e iza ion.
X- ay di ac ion (XRD) pa e ns we e measu ed a he CITIUS X- ay labo a o y (Uni e si y
o Se ille, Spain) using a B uke D8 Ad ance ins umen equipped wi h a Cu Kα adia ion
sou ce, ope a ing a 40 kV and 40 mA, and wi h a Ni il e . The powde XRD pa e ns we e
egis e ed in he 2θ- ange 3–70° wi h a s ep size o 0.05° and a ime s ep o 0.03 s. 
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Figu e 1S: X- ay di ac og ams ob ained o he s a ing samples- Na-mica-n
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Figu e 2S: X- ay di ac og ams ob ained o he s a ing samples homoionized wi h Li+, K+,
Mg+ 2and Al+3 ca ions.
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