1
THERMAL CHARACTERIZATION OF MONTMORILLONITE CLAYS
SATURATED WITH VARIOUS CATIONS
V. Balek 1,2*, M. Beneš1, J. Šub 2, J. L. Pé ez-Rod íguez3,
P.E. Sánchez-Jiménez3, L. A. Pé ez-Maqueda3 , J. Pascual-Cosp4
1Nuclea Resea ch Ins i u e Řež , plc., CZ-250 68 Řež, Czech Republic
2Ins i u e o Ino ganic Chemis y ASCR, CZ-250 68 Řež, Czech Republic
3Ins i u e o Ma e ials Sciences, CSIC - Uni . o Se illa, 41092 Se illa, Spain
4Depa men o Ci il Enginee ing, Technology and Ma e ials, Uni o Málaga,
29013 Málaga, Spain
Abs ac
Emana ion he mal analysis (ETA), he mog a ime y and high empe a u e XRD
we e used o cha ac e ize he he mal beha io du ing dehyd a ion o na u al Na
mon mo illoni e (Up on Wyoming, USA) and homoionic mon mo illoni e (MMT) samples
sa u a ed wi h di e en ca ions, i.e. Cs+, NH4+, Li+, Al 3+and Mg2. ETA esul s cha ac e ized
mic os uc u e changes ha accompanied he mass loss o he samples due o dehyd a ion on
hea ing in ai .A collapse o in e laye space be ween he silica e shee s a e wa e elease
om he MMT samples was cha ac e ized by a dec ease o he adon elease a e, ∆E.
Dec eases in c-axis basal spacing (d001) alues de e mined om XRD pa e ns o he
di e en mon mo illoni e samples ollow he sequence:
Mg-MMT> Al -MMT > Li -MMT > Na-MMT> NH4-MMT>Cs-MMT.
The dec ease o he adon elease a e (∆E) de e mined by ETA ha cha ac e ized
mic os uc u e changes due o collapse o in e laye space co esponded well o di e ences in
he c-axis basal spacing (∆d001) alues de e mined om he XRD pa e ns be o e and a e
samples dehyd a ion .
*co esponding au ho : bal@uj .cz
2
Key wo ds: Na-mon mo illoni e sa u a ed wi h a ious ca ions ,emana ion he mal
analysis, XRD, he mog a ime y , mic os uc u e changes , dehyd a ion
1.In oduc ion
In o de o unde s and he en i onmen al beha iou o monmo illoni e clay mine als
hei dehyd a ion and dehyd oxyla ion on hea ing has been s udied by se e al au ho s [1-7]. I
was ound ha di e ences in he mon mo illoni e dehyd a ion a e due o a mo e o less s ong
pola ising powe o he exchangeable ca ion. The hyd a ion numbe o he exchangeable
ca ions can be exp essed by a basic spacing o he clay s uc u e cha ac e ized by c-axis basal
spacing d001 [1]. The dec ease o he c-axis basal spacing akes place as he esul o he
mon mo illoni e dehyd a ion, obse ed usually on hea ing up o 200 °C. Mackenzie [5]
sugges ed ha he amoun o in e laye wa e depends on hyd a ion ene gy o he adso bed
ca ions and on hyd a ion o he su ace, and ha he mog a ime y esul s can be in e p e ed
o gi e ela i e alues o hese amoun s o wa e . He s a ed ha o mos o di alen ca ions
(e.g. Mg2+ and Ca2+) he ion is mo e impo an ha he in e laye su ace, bu o la ge
di alen ca ions as well as o mono alen ca ions he in luence o he laye ed su ace on he
hyd a ion is dominan . Glasse e al. [7] showed ha poly alen ions end o de ach
hemsel es om he silica e su ace and inco po a e in he wa e laye s. They s a ed ha he
comple e loss o he in e laye wa e is accompanied by a educ ion in he c-axis dimensions
( o 9.4–10 Å) wi h exac alue depending on he size o in e lamella ions.
In his s udy he mog a ime y , emana ion he mal analysis and high empe a u e
X- ay di ac ion me hods we e used o cha ac e ize he he mal beha io du ing
dehyd a ion o na u al Na mon mo illoni e and homoionic mon mo illoni e samples p epa ed
3
by a sa u a ion o Na mon mo illoni e wi h ca ions o Cs+, NH4+ , Li+, Al 3+ and Mg2+,
espec i ely . High empe a u e X- ay di ac ion was used o de e mine he c-axis basal
spacing pa ame e s o he mon mo illoni e samples. Emana ion The mal Analysis (ETA)
[8,9], based on he measu emen o adon elease om samples p e iously labeled, was used
o cha ac e ize mic os uc u e changes du ing „in si u“ hea ing o he samples. The ETA has
been p e iously used in he cha ac e iza ion o he he mal beha io o a ious mine als, such
as kaolini e [10], saponi e, beideli e [3], e miculi e [11-13], boehmi e [14], py ophylli e, alc
[15], b anne i e [16], haema i e [17].
2. Expe imen al
2.1 Samples
Na u al Na-mon mo illoni e (Up on, Wyoming, USA) was used as a s a ing ma e ial.
Homoionic mon mo illoni e samples sa u a ed wi h Cs+, NH4+, Li+, Al3+ and
Mg2+, espec i ely , we e p epa ed om Na-mon mo illoni e sample as ollows: he amoun o
10 g o he Na-mon mo illoni e was mixed wi h 800 ml o wa e and s i ed du ing wo days.
A e decan a ion 0.2 M chlo ide solu ion (200 ml) o he espec i e ca ion was added. The
suspension was s i ed o wo days, se e al imes washed by dis illed wa e un il he nega i e
eac ion o chlo ides (using Ag+ ions). The samples p epa ed by his way we e d ied a he
empe a u e o 40 °C in ai .
2.2 Me hods
Emana ion he mal analysis (ETA) measu emen s we e ca ied ou by using a
modi ied NETZSCH Equipmen Type DTA 404. The samples we e hea ed a he a e o 6
K/min in a cons an ai low o 75 ml/min. Samples o ETA measu emen s we e labeled by a
su ace adso p ion o ace amoun o 228Th as ni a e in ace one solu ion. The speci ic
ac i i y o he sample was 104 Bq/g am. A oms o adon 220Rn we e o med by a spon aneous
4
α-decay o 228Th and 224Ra. The 220Rn a oms we e implan ed in o he subsu ace o he
samples by ecoil ene gy o 85 keV/a om o a maximum dep h o 80 nm, as calcula ed by
he Mon e Ca lo me hod using TRIM code [18]. Mo e de ails abou emana ion he mal
analysis as a less common me hod a e gi en elsewhe e [8 ,9]. TG /DTG measu emen s we e
ca ied ou by using NETZSCH Equipmen Type STA 429 on hea ing a 6 K/min in ai .
XRD equipmen (PHILIPS PW 1050/25) using Cu Kα Ni- il e ed adia ion and
equipped wi h a high empe a u e chambe was applied o ob ain XRD pa e ns and o
de e mine c-axis basal spacings (d001).
3. Resul s and discussion
The mog a ime y esul s (TG /DTG cu es) o Na-mon mo illoni e and homoionic
mon mo illoni e samples sa u a ed wi h Mg2+, Cs+, NH4+ ,Li+ and Al 3+ ions, espec i ely,
a e p esen ed in Figs. 1 A-F. The mass loss obse ed om abou 50 °C up o abou 200 ºC
co esponds o a elease o mainly in e laye wa e molecules si ua ed be ween he silica e
shee s o he mon o illoni e samples. Bo h he amoun o eleased wa e and he empe a u e
o he p ocess is a ec ed by he in e laye ca ion [5,6]. The dehyd a ion o he samples
p oduces a dec ease in he basal spacing, as shown by high empe a u e XRD measu emen s
( see Figu es 2 A-F ).
Figu es 3 A-F depic emana ion he mal analysis esul s o Na–mon mo illoni e and
homoionic mon mo illoni e samples p epa ed by sa u a ion o Na –mon mo illoni e wi h
Mg2+, Cs+,NH4+,Li+ and Al 3+ ions, espec i ely. These igu es show an enhanced adon
elease a e, E(T), a he beginning o he hea ing due o he su ace exposu e a e he wa e
elease om he samples, ollowed by a dec ease o adon elease a e ha cha ac e ized he
collapse o he in e laye space be ween he silica e shee s, ini ially illed by wa e molecules.
5
By his way he ETA esul s b ough abou in o ma ion abou he s uc u e changes unde in
si u hea ing o he mon mo illoni e samples du ing hei dehyd a ion .Acco ding o he ETA
esul s p esen ed in Figu es 3 A-F he in ensi y o changes in he adon mobili y di e ed o
he ion-exchanged mon mo illoni e samples in es iga ed. The esul s ob ained in his s udy
can be compa ed wi h he esul s o ou p e ious s udy [4] cha ac e izing he mal beha iou
on a gon hea ing o Na- monmo illoni e sa u a ed wi h ca ions o Li+, Mg2 o Al3,
espec i ely.
In his s udy a special a en ion has been paid o he compa ison o he ETA esul s
wi h XRD esul s cha ac e izing he collapse o he in e laye space du ing dehyd a ion o
he mon mo illoni e samples. A ma hema ical model p oposed [19] was used in o de o
quan i a i ely e alua e he mobili y o adon a oms ha se ed as a p obe o mic os uc u e
changes in he samples .
The empe a u e dependence o he adon elease a e measu ed, E(T) can be
exp essed as
E (T) = E 25 + ED(T)•Ψ(T)
whe e E25 is adon elease a e measu ed a oom empe a u e , ED (T) is adon
di usion along s uc u e i egula i ies ha se ed as adon di usion pa hs, Ψ(T) is
cha ac e izing he changes in he numbe o he adon di usion pa hs.
The empe a u e dependence o he adon elease a e ,ED (T), was used o he
e alua ion o he anspo p ope ies and o mic os uc u e de elopmen cha ac e iza ion o
he samples on hea ing.
The model cu es o he empe a u e dependences o he adon elease a e ED(T) a e
p esen ed in Figu es 3 A-F as ull lines, whe eas he ETA expe imen al da a a e p esen ed
as poin s. A good ag eemen o he modelling esul s and he expe imen al ETA da a was
achie ed.

6
Fig. 4 depic s empe a u e dependences o Ψ(T) unc ions ob ained by modelling and
i ing he expe imen al ETA da a wi h he ma hema ical model [19] o cha ac e ize he
in ensi y o he mic os uc u e changes o he ini ial mon mo illoni e in e laye s uc u e due
o dehyd a ion. Table 1 summa izes alues o adon elease a e dec ease (∆E). F om Fig.4
and Table 1 i ollows ha he ∆E alues ha cha ac e ized s icking o he mon mo illoni e
in e laye space due o dehyd a ion dec ease in he sequence:
Mg-MMT> Al -MMT > Li -MMT > Na-MMT> NH4-MMT>Cs-MMT.
Values o di e ence in c-axis basal spacing (∆d001) ha cha ac e ize he s icking o he
in e laye space o he samples due o hei dehyd a ion a e also included in Table 1.
Fig. 5 depic s he linea ela ionship be ween alues o he di e ences ∆d001 in alues o c-
axis basal spacing and he co esponding alues o ∆E cha ac e izing mic os uc u e changes
due o dehyd a ion o he mon mo illoni e samples. The mos in ense dec ease o he adon
mobili y, ∆E, was obse ed wi h he Mg-mon mo illoni e ( see Fig. 1 B and Fig. 4. cu e 2).
The di e ences in he c-axis basal spacing (∆d001) de e mined om he XRD pa e ns ( see
Fig.2 B) suppo ed hese esul s. Thus, i is ob ious ha he ETA cha ac e iza ion o he
mic os uc u e changes due o dehyd a ion o he samples, co esponded well o di e ences
in he c-axis basal spacing (∆d001) alues de e mined om he XRD pa e ns.
4. Conclusions
ETA b ough abou addi ional in o ma ion abou p ocesses ha ook place on hea ing
o homoionic mon mo illoni e samples sa u a ed wi h a ious ca ions .
The dec ease o adon elease a e ∆E, de e mined by ETA cha ac e ized a dec ease o adon
mobili y du ing he collapse o he samples in e laye space. A good ag eemen was ound
be ween he dec ease o adon elease a e, ∆E de e mined om ETA measu emen s and
di e ences ∆d001 in alues o he c-axis basal spacing (d001) de e mined om XRD pa e ns.
7
Acknowledgmen s
The pape was p epa ed in he ame o he bila e al coope a ion be ween C.S.I.C and
Academy o Sciences o he Czech Republic. P esen a ion o his wo k was suppo ed by he
Minis y o Educa ion o Czech Republic (P ojec LA–292).and by he Minis y o Educa ion
o Spain (MAT2004-02640)
Re e ences
1. R.A. Rowland, E.J. Weiss, W.D. B adley, Na . Acad. Sci. Publ., 456 (1956) pp. 85–96.
2. C.M. Wa shaw, P.E. Rosenbe g, R. Roy, Clay Mine als Bull., 4 (1960) 113.
3. Z. Málek, V. Balek, D. Ga inkel-Shweky and S. Ya i , J. The mal Anal., 48 (1997) 83.
4. V. Balek, M. Beneš, G. Ma uschek, A.A.Ke up, Z.Málek, J. The m. Anal. Cal., 88
(2007) 93
5. R.C. Mackenzie, Be . Deu . Ke am. Ges., 41 (1964) 696.
6. C.M. Ea nes , in: W. Smyka z-Kloss and Slade S.J. Wa ne (Eds), The mal Analysis in
Geosciences, Sp inge Ve lag 1991, pp. 288–312
7. R.I. Glasse , I. Man in, J. Me ing, In e n. Geol. Cong . 21s Session, No den, F ance
(1960) pp. 28–34.
8. V. Balek and J. Tölgyessy, Emana ion he mal analysis and o he adiome ic
emana ion me hods, in: Wilson and Wilson (Eds), Comp ehensi e Analy ical Chemis y, Pa
XIIC, Else ie , Ams e dam 1984, 304 pp.
9. V. Balek, J. Šub , T. Mi suhashi, I. N. Beckman and K. Gyö yo á, J. The m. Anal. Cal.,
67 (2002) 15
10. V.Balek, M Mu a , The mochim, Ac a, 282 /283 (1996) 385
8
11. L. A. Pé ez-Maqueda, V.Balek, J. Poya o, J. L Pé ez-Rod íquez, J.Šub , I.M. Boun se a,
I. N. Beckman and Z. Málek, J. The m. Anal. Cal., 71 (2003) 715.
12. J. Poya o, L. A. Pe ez-Maqueda, A. Jus o, V. Balek, Clays Clay Mine . 50 (2002) 791.
13. V. Balek, J. L. Pe ez-Rod iguez, L. A. Pe ez-Maqueda, J. Sub , J. Poya o, J. The m.
Anal. Cal. 88 (2007) 819.
14.V.Balek,J.Šub ,J.Rouque ol,P.Llewellyn,V.Zelenák,I.M.Boun se a,I.N.Beckman,
K.Gyö yo á , J.The m. Anal.Cal., 71(2003) 773
15. V. Balek, L.A. Pé ez-Maqueda, J. Poya o, Z. Če ný, V. Ramí ez-Valle , I.M.Boun se a,
J. L. Pé ez-Rod íguez , J. The m. Anal. Cal., 88 (2007) 87
16.V. Balek, E.R. Vance, V. Zeleňák, Z. Málek, J. Šub , J. The m. Anal. Cal., 88 (2007) 93
17. L. A. Pé ez-Maqueda, J. M. C iado, C. Real, V. Balek, J. Sub , J. Eu op. Ce am. Soc. 22
(2002) 2277.
18. J.F. Ziegle and J.P.Bie sack, The s opping and ange o ions in solids, Pe gamon P ess,
New Yo k ,1985.
19. I.N.Beckman , V. Balek, J. The m. Anal. Cal., 67 (2002) 49
9
Table 1
Values o adon elease a e dec ease ∆E and di e ences c-axis basal spacing ∆d001
cha ac e izing dehyd a ion o mon mo illoni e samples sa u a ed wi h a ious ca ions
Mon mo illoni e Dec ease o adon elease a e Di e ence in c-axis spacing
Ca ion ∆E [ el.uni s] ∆d001 [Ǻ]
Ini ial sample-
Na+
0.149 1.59
Mg2+ 0.349 4.48
Cs+ 0.064 0.94
NH4+ 0.100 1.37
Al3+ 0.276 3.80
Li+ 0.257 2.57
16
5 1015202530
C3.36
4.28
4.48
7.65
11.27
150ºC
60ºC
2θ
30ºC
12.21
11.78
5 1015202530
D
3.36
4.28
4.49
10.42
200ºC
100ºC
2θ
30ºC
12.27
10.72
Fig. 2C-D

17
5 1015202530
E
3.36
4.28
4.51
10.77
200ºC
75ºC
2θ
30ºC
14.93
13.01
5 1015202530
F3.36
4.28
4.49
12.38
200ºC
75ºC
2θ
30ºC
10.05
11.84
Balek e al ,
Figs.2 E-F
18
0 200 400
0.00
0.05
0.10
0.15
0.20
0.25
E /Rel. uni s
Tempe a u e /°C
A
0 200 400
0.0
0.1
0.2
0.3
0.4
0.5
0.6
E / el.uni s
Tempe a u e /oC
B
Fig.3A-B
19
0 200 400
0.0
0.1
0.2
0.3
0.4
E / el.uni s
Tempe a u e / oC
C
0 200 400
0.00
0.05
0.10
0.15
0.20
0.25
E / el.uni s
Tempe a u e / oC
D
Fig.3C-D
20
Balek e al
Figs.3 E-F
21
0 100 200 300 400
0.7
0.8
0.9
1.0
6
5
4
3
2
1
Ψ(T)
Tempe a u e /oC
Balek e al
Fig.4

22
0.05 0.10 0.15 0.20 0.25 0.30 0.35
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
Al3+
Li+
Mg2+
Na+
NH4
+
Cs+
∆d001 / A
∆E / el.uni s
Balek e al
Fig.5