Clays and Clay Minerals, 1972, Vol.
20, pp. 2 5 9 - 2 7 0 .
P e r g a m o n Press.
P r i n t e d in G r e a t B r i t a i n
A D S O R P T I O N OF E T H Y L E N E D I A M I N E (EDA)
O N M O N T M O R I L L O N I T E S A T U R A T E D WITH
DIFFERENT CATIONS-II. HYDROGEN- AND
ET HYLENEDIAMMONIUM-MONTMORILLONITE:
PROTONATION
AND HYDROGEN
BONDING
P. CLOOS and R. D. LAURA
Laboratoire de Physico-Chimie Minrrale, Institut des Sciences de la Terre,
de Croylaan 42, 3030 Heverlee, Belgium
(Received 28 February 1972)
Abstract--The form under which ethylenediamine (EDA) is adsorbed from aqueous solution by
hydrogen- and ethylenediammonium-montmorillonite was studied as a function of the amount of
amine present in the system.
EDA added to the acid clay in quantities lower than or equal to the cation exchange capacity
9
"
(C.E.C.) was exclusively adsorbed as ethylenedlammonmm
( E D A H 22+) ion. On further addition of
diamine the pH of the suspension rose to alkaline values and the monoprotonated species (EDAH §
was the main charge balancing cation.
Evaporating at room temperature "EDA-H-montmorillonite-H20" or "EDA-EDAH2-montmorillonite-H20" systems containing 300 me EDA/100 g clay did not cause loss of nitrogen, but
degassing under high vacuum (10 -~ rnm Hg) did. Nevertheless, excess EDA molecules with respect
to the C.E.C. were retained on the clay surface, at the expense of water molecules, through strong
asymmetrical hydrogen bonds between their NH2 groups and the NH3 + groups of EDAH + ions. On
heating up to 160~ under vacuum the nitrogen content decreased further, but still remained at a level
significantly higher than the C.E.C. value, all NH3 + groups remaining involved in strong hydrogen
bonding. It is suggested that a "condensation" process takes place, implying evolution of EDA
molecules and giving rise to "polymeric" associations between protonated and unprotonated diamine.
Washing the clay suspensions with distilled water did not completely remove excess EDA either,
as a consequence of the equilibrium existing between the ionic species in solution (EDAH2~+ and
EDAH § and on the clay surface. It seems that these species were preferentially adsorbed as "trimeric"
associations in which two out of four NH3 § groups are hydrogen bonded to NH2 groups.
After heating at 200~ nitrogen retained on the clay surface was mainly in the form of NH4+
ions. Ammonium formation was enhanced by the presence of excess EDA and was considerably
faster than in montmorillonite systems containing EDA coordinated to Cu ~+ions.
INTRODUCTION
et al. (1962) for propyl- and butyl-amine, ethyleneand propylene-diamine, and by Mortland and
Barak6 (1964) for ethylamine. The same authors
report that ethylamine, ethylene- and propylenediamine are adsorbed in amounts largely exceeding
the cation exchange capacity of the clay. Similarly,
ethylamine is adsorbed by ethylammonium montmoriUonite (Farmer and Mortland, 1965). This is
interpreted in terms of competition between water
and amine molecules to associate with the alkylammonium cations through hydrogen bonding. It
must, however, be pointed out that the above mentioned studies were performed on non-aqueous
systems. Servais e t a ! . (1962) treated freeze-dried
259
THE NATURE of the exchangeable cation is one of
the most important factors determining the adsorption mechanism of alkylamines by clay surfaces
and hence the kind and stability of the amino-clay
complexes formed. As shown in part I of this study
(Laura and Cloos, 1970), with Cu 2+ ion, a definite
and stable coordination complex is obtained,
whether ethylene-diamine is added as pure liquid
to an air-dry montmorillonite film, or as aqueous
solution to a montmorillonite suspension.
On acid clay, protonation of the adsorbed amine
is the expected mechanism. This has actually
been observed by Fripiat et al. (1962), Servais
260
P. CLOTS and R. D. LAURA
montmorillonite with a benzene solution of amine,
whereas Mortland et al. (1964, 1965) exposed a
vacuum evacuated clay film to ethylamine vapor.
A priori, it may be assumed that in aqueous
medium the amine is not necessarily as successful
a competitor as in dehydrated systems. The fact
that ethylamine is displaced from the ethylamineethylammonium complex by water vapor at room
humidity ( F a r m e r and Mortland, 1965) sufficiently
justifies this assumption. On the other hand, from
the work of Servais et al. (1962) and Fripiat et al.
(1962) it appears that monoamines and diamines
do not behave in the same manner. In contrast
with what is observed for ethylene- and propylenediamine, propyl- and butyl-amine-montmorillonite systems show no excess retention with respect to the C.E.C. after washing with an essentially
non polar solvent such as benzene.
Therefore, it seemed of interest to the authors, to
carry out this adsorption study on aqueous
suspension, and to compare the thermal stability
of the compounds obtained in these conditions with
that of the copper-ethylenediamine complex
investigated previously (Laura and C l o t s , 1970).
~"
11- /)-----~
/
/"
RESULTS
Potentiometric titration curves
The potentiometric titration curves of different
clay suspensions with E D A solution are compared
in Fig. 1. With H-montmorillonite, like C u -
//'I
/
/t
,
J
~
J
/
// J
I
I
/
/
0
MATERIALS AND METHODS
The clay used was montmorillonite from CampBerteau (Morocco). Its cation exchange capacity
(C.E.C.), measured with NH4 § ion at p H 7,
amounts to 103 • 3 me/100 g. H-montmorillonite
was prepared by passing a 1 per cent suspension
of Na-montmorillonite (< 2~ fraction) through a
column of hydrogen saturated Amberlite IR-120
resin. This suspension was used immediately after
preparation in order to keep the level of conversion
of H - to A l - c l a y as low as possible (Eeckman and
Laudelout, 1961). EDAH2-montmorillonite was
obtained by treating the < 2/~ N a - c l a y fraction
three times with an excess of 1.0N solution of
ethylenediamine dihydrochloride, and then washing
it with distilled water on the centrifuge until free
of chloride.
The experimental methods used were the same
as described in part I (Laura and C l o t s , 1970).
Different amounts of E D A were added to 50 ml
portions of 1% clay suspensions (Fig. 1), and after
equilibration overnight, the samples were investigated before and after washing three times with
distilled water. X-ray and i.r. spectra were recorded
on thin oriented clay films (3-4 mg/cm2). Nitrogen
was determined by micro-Kjeldahl technique.
~. . . . . . . . . . . . . . . . . . . . . . . .
[
/
I
I
4
I
8
I
12
I
16
m l of 0.1N E D A
20
Fig. l. Potentiometric titration curves of 1% suspensions
(50 ml) of montmorillonite saturated by Cu 2§ (
),
H § ( - - - - - ) , EDAH~ 2+ ( . . . . . . ) and Na + (- . . . . . ) with
0.1 N aqueous solution of ethylenediamine. Arrows
indicate the amounts of EDA added for the preparation
of samples.
montmorillonite, the p H remained initially constant,
then increased suddenly; on further addition of
amine its increase was very slow. The quantity of
base added to reach the inflection point was about
half of that needed in the C u - c l a y system. As
expected, no inflection was observed in case of
E D A H 2 - and Na-montmorillonite. With the first
portions of amine added the p H rose directly to
alkaline values.
C h e m i c a l analysis
Table 1 shows the distribution of E D A between
the solid and liquid phases after equilibration overnight. Samples 1, 2 arid 3 of H-montmorillonite
correspond on the titration curve (Fig. 1) to points
respectively below, at and above the inflection
point. T h e balance between the quantities of amine
added and found in the various systems studied
can be considered as satisfactory, especially when
taking into account that the nitrogen determinations in the different phases required much handling,
thus multiplying the sources of error, and that tfiey
were carried out on small-sized samples (< 100 mg
clay). U p to the inflection point the total amount
ADSORPTION OF EDA ON MONTMORILLONITE
261
Table 1. Distribution of EDA between solid and liquid phases
Amounts of N (me/100 g of clay)
Saturating
cation
Sample
No.
H+
1
2
3
EDAHz 2+ Reference
4
Total
added
On clay
after
washing
In equilibrium
sol.
51
98
284
0
197
48
96
134
105
161
0
1
105
0
n.d.
In
washings
1
3
34
0
n.d.
n.d. - not determined.
of amine added was adsorbed on the clay and
resisted removal by washing. On further addition a
supplementary quantity was retained against
washing.
Similarly,
EDAH2-montmorillonite
adsorbs E D A which cannot be removed completely
by washing, the adsorption level considerably
exceeding the C.E.C. value.
X-ray data
The basal spacings d(001) of the different
systems studied are compared in Table 2. They
show the effect of four factors: (1) amount of
amine adsorbed, (2) outgassing at room temperature, (3) heating under vacuum, and (4) nature of
the saturating cation. They increased slightly as
the degree of adsorption went beyond the C.E.C.
value. Outgassing at ambient temperature caused
a small decrease in spacing; the experimental
values obtained compare fairly well with those
reported by L6onard et al. (1962). Heating under
vacuum reduced the basal spacing and provoked
interstratification. This phenomenon started at
80~ for sample 1, partially saturated with E D A ,
and at 120~ for the other samples. Complete
structure collapse at 200~ was observed only
for the reference and washed EDAH2-montmorillonite samples. After rehydration reexpansion to
the original value did not take place in any case.
The spacings of H-montmorillonite were generally
0.3-0.4 A higher than those of EDAH~-montmorillonite for equivalent E D A contents.
I.R. data
Provided samples with comparable N contents
are considered, the i.r. spectra are broadly similar,
whether the starting material was H - or E D A H z montmorillonite. This is illustrated in Fig. 2 showing spectra of the different systems after outgassing
at ambient temperature. In the case of acid clay,
bands are generally less distinct, probably as a
consequence of a lower degree of homogeneity
due to partial aluminization of the starting material.
Spectra recorded on samples containing different
levels of E D A showed significant differences
Table 2. Basal spacings d(001) in A for washed and unwashed samples after different treatments
Treatment
Saturating
cation
H+
EDAH~2+
Sample
No.
Reference
1 unw
1w
2 unw
2w
3 unw
3w
reference
4 unw
4w
Ambient tempera?.
hydrated outgassed
11-9"
12.5"
12-4"
12.6"
12.7"
12.9"
12.6"
12.2'
12.7'
12-3"
10.0"
12-0"
12.0"
12.3"
12.3"
12.6"
12.4"
11.9"
12.3"
12.0"
80~
outg.
120~
outg.
160~
outg.
200~
outg.
9-7*
10.87
11-2?
12-2"
12.3"
12.8"
12.6"
12.0"
12.5"
12.2"
9-6"
10.2t
10.37
10-97
10.77
11.87
11-5?
10-27
11.3?
10-97
-10-0?
10.2t
10.87
10.57
11.3?
10-77
10-0?
10.47
10-27
9.5*
9.9t
9"9t
10.47
10.2?
10-57
10-4t
9-6*
10.2-~
9.7*
u n w - unwashed; w-- washed.
*Rational or nearly rational (average value of the first, second and fourth order).
?Irrational, value of 001 reflexion.
Rehydrated
overnight
-9.8t
9-9t
10-27
10.27
11.67
10.37
9.5*
---
262
P. CLOOS and R. D. LAURA
#
T
U
Z
<~
rn
b
.,<
I
tN
o
..... ! . . . . . . . . . . . .
-f
2.5
J
: . . . . . T. . . . . . . . . .
-. . . . . . . . . ~
I
I
I
3.0
3.5
4.0
I
4.5
"
-
~e
" - "?....
I
I
I-
I
I
I
5.0
5.5
6.0
6.5
ZO
7.5
p
Fig. 2. I.R. spectra of H- and EDAH2-montmorillonitehaving adsorbed different levels
of EDA, after degassing under vacuum (10-5 mm Hg) at ambient temperature. - - :
EDAH2-montmorillonite; reference, 16 hr (a); sample 4w, 6 hr (c); sample 4unw, 3 hr
(e). - . . . . : H-montmorillonite; sample 2unw, 2 hr (b); sample 3w, 16 hr (d); sample
3unw, 2 hr (f). Times indicated in hours refer to the degassing treatment.
mainly in the position and shape of the N - H
bands. Table 3 gives the band assignments as
suggested by data in the literature (Powell, 1960;
Sabatini and Califano, 1960; J. Bellanato, 1960;
Fripiat et al., 1962) and will be discussed later.
The stretching region of each spectrum is
dominated by a broad absorption extending from
3350 to 2200 cm -~ with a main band near 3200
c m - ' . As the N content increased beyond the
C.E.C. value, this band sharpens, becomes more
symmetric and its maximum shifts to higher
frequencies. Simultaneously a new band of low
intensity develops near 3360cm -~ which is
assigned to vNH2 asym. of excess unprotonated
or monoprotonated EDA. In the 2800-1700
c m - ' range, absorption is slightly enhanced, two
diffuse, weak and broad bands emerging near
2500-2400 cm -~ and 2000 cm -~ respectively.
The 1843 cm -~ band is probably due to the clay
structure as it is already~present in pure montmorillonite. C - H vibrations in t h e 2 8 0 0 - 3 0 0 0 cm '
region appear more or less distinct. In the deformation region the two prominent bands near 1500
and 1600cm -1 correspond to the 6NH3 + sym.
and 6NH3 + asym. vibration modes respectively,
while the weaker absorptions in the 1450-1470
cm -1 range are due to CH2 scissoring. Excess
adsorption of E D A affected the position of the
high frequency band little, but resulted in broadening, especially for samples containing more than
2 0 0 m e N / 1 0 0 g (curves e and f). Moreover, in
this latter case two maxima may be distinguished
near 1637 and 1600 c m - ' and seem to be related
to contributions from 6NH3 + asym. and 6NH~ sci.
vibrations. Band broadening and development of
two diffuse maxima, near 1538 and 1 5 1 0 c m - '
respectively, are also shown by the 6NH3 + sym.
absorption when E D A is retained against washing
in excess of the C.E.C. (curves c and d). This
might be interpreted as an indication of the
existence of two different environments for the
NH3 + groups on the clay surface. When E D A
adsorption exceeds 200 per cent of the C.E.C.
(curves e and f) one single 6NH3 + sym. band of
medium intensity remains near 1540 cm -1. These
results differ from those of Fripiat et al. (1962)
who observed no 6NHz + sym. band in the 1500
cm -1 region on samples containing more than 50
mmoles of EDA, but only one absorption at 1597
c m - ' which they assigned to 6NH~ sci. vibration.
ADSORPTION OF EDA ON MONTMORILLONITE
Table 3. Vibration bands and their assignment for EDA
adsorbed on H- and EDAH2-montmorillonite
Band assignment
vOH (hyd. water)
vNH2 asym.
vNH4+
uNH2 sym. (+ vNH3+)
vNH3+
vCH2 asym.
vCH2 sym.
v/~-H... N
~OH (hyd. water)
+
8 N - H . . . N asym.
8NH3+ asym.
8NH2 sci.
81~-H... N sym.
+
~ N - H . . . OH2 sym.
~NH3+ sym.
8CH2 sci.
8NH4+
Observed frequencies in cm -1
Normal
Deuterated
3400
3362
3280
3226
3175 (b)
2963
2899
2439 (b)
1980 (b)
1634
1637
1617
1600
1538
1530
1510
1465
1449
1429
2597
2516
-2424
2387 (b)
2963
2890
1835 (b)
?
-------1460
1447
--
v-Streching; 8-Deformation; asym.-asymmetric;
sym. - symmetric; sci. - scissoring; (b)- broad.
This discrepancy might arise from the fact that
these authors prepared oriented films by pressing
powdered clay between stainless steel disks,
which probably did not assure the same degree
of orientation as slow evaporation of dilute clay
suspensions.
The data obtained in this work are more nearly
comparable to the findings of Farmer and Mortland
(1965) on the ethylamine-ethylammoniumsystem.
After adsorption of ethylamine on ethylammonium
montmorillonite they observed the replacement of
the ~NH3 + sym. ( 1 5 1 0 c m - 0 and ~NH3 + asym.
(1617 cm -1) absorptions respectively, by a diffuse
shoulder extending from 1580 to 1510cm -~ and
by two bands at 1642 and 1593 cm -1. In their
opinion the 1593 cm -~ vibration is due to NHz
scissoring, whereas the high frequency band can
be ascribed to the proton involved in symmetric
hydrogen bonding between the components of a
dimer of structure
Et
H
H
Et
The effect of degassing and heating under
vacuum is illustrated in Fig. 3. The changes
C C M Vol. 20, N o , 5 - B
263
brought about in the i.r. spectra by this treatment
are the same for E D A H 2 - and E D A - H - m o n t morillonite. Air-dried samples (curves a, f and k)
show strong absorptions by hydration water near
3400 and 1634cm -~, which obscure the N - H
bands of the respective regions. O n dehydration
the ~NH3 + sym. band shifts progressively from 1530
to 1508 cm -1 in the case of samples containing
no excess E D A (Figs. 3A, b and 2, a and b).
When a large excess of E D A was present (Fig.
3C, 1), the shift occurs in the opposite direction
(1538cm -1) accompanied by a decrease of the
absorption intensity. A similar weakening of the
6NH3 + sym. absorption was recorded for samples
containing a moderate excess of E D A (Fig. 3B, g).
Heating to 120~ did not cause major modifications of the spectra, except a further decrease of
the 8NH3 + sym. bands of samples having retained
excess E D A against washing (Fig. 3B, h). At
200~ a drastic change occurs in the spectra of
all the samples: the N - H bands of NH3 + and NH2
groups are replaced by strong, sharp NH4 + absorptions at 1429 and 3280cm -1. Simultaneously,
three rather weak bands appear at 1667, 1608
and 1303 cm -1 which might be associated with
decay products of E D A (Laura and Cloos, 1970).
I n samples containing excess E D A , ammonium
ion formation commenced at 160~ (Figs. 3B, i
and 3C, n). It should also be noted that at 200~
C - H vibrations in the 2 8 0 0 - 3 0 0 0 c m -1 region
and near 1465 cm -1 persist; their intensities seem
to be proportional to those of the three bands
attributed to decay products, which in turn
depend on the N contents of the respective samples.
DISCUSSION
The inflection point of the titration curve of H montmorillonite (Fig. 1) corresponds to an amount
of E D A equalling the C.E.C. value (Table 1,
sample 2). This indicates that E D A was adsorbed
as divalent E D A H z 2+ ion up to complete saturation of the C.E.C. Further support for this conclusion is provided by the similarity of the i.r.
spectra of pure EDAH2-montmorillonite and
of H-montmorillonite treated with E D A (Fig. 2,
a and b). The findings of Fripiat et al. (1962)
were similar, whereas Conley and Lloyd (1971)
suggested that on the surface of H-kaolinite E D A
functions as a monoamine, one single NH~ group
being protonated. The adsorption mechanism
involved is obviously proton transfer from the
clay surface to E D A , according to
2 m o n t . - H + E D A ~ (mont.-)~ EDAH2
As proposed by Servais et al. (1962), AP + ions
present in acid clay may participate in amine
264
P. CLOOS and R. D. L A U R A
A
I~ o
c
B
JI v
O
<
Ii
-,
~1
2.5
3,5
6
7
2.5
35
6
7
2.5
35
I
I
7
6
I
Fig. 3. I.R. spectra of H-montmorillonite ( - - - - - ) and EDAH~-montmorillonite (
)
having adsorbed different levels of E D A as affected by degassing and heating under
vacuum (10-~mm Hg). (A) EDA-H-mont. (sample 2unw) and EDAHz-mont. (reference): air-dried (a); degassed at ambient temp., 16 hrs. (b); heated under vacuum at
80~ 3 hr (c), at 160~ 4 hr (d), at 200~ 16 hr (e). (B) E D A - H - m o n t . (sample 3w)
and EDA-EDAHz-mont. (sample 4w) air-dried (f); degassed at ambient temp., 6 hr
(g); heated under vacuum at 120~ 16hr (h), at 160~ 3 hr (i), at 200~ 4 h r (j).
(C) E D A - H - m o n t . (sample 3unw) and EDA-EDAH~-mont. (sample 4unw): airdried (k); degassed at ambient temp., 2 hr (1); heated under vacuum at 120~ 3 hr (m),
at 160~ 4 hr (n), at 200~ 3 hr (o).
adsorption through the following dissociation:
(mont.-)3 AI(H~O)6 ~ 3 m o n t . - H + AI(OH)z
+ 3H20
T h e formation of AI(OH)3 in the interlamellar
s p a c e might account for the slight discrepancies in
the basal spacings (Table 2) o b s e r v e d b e t w e e n
E D A H ~ - and H - m o n t m o r i l l o n i t e with comparable
N contents.
U p o n addition of E D A in e x c e s s o f the C . E . C .
the p H o f the suspension rose as a c o n s e q u e n c e of
the following equilibria:
HzN-CHz-CH2-NH2 + H20
H2N-CH2-CHz-NHz ++ OH-
(1)
H2N-CH2-CH2-NH3 ++ H20
H3N+-CH2-CH2-NH3 ++ OH-
(2)
with
K m = [ E D A H + ] [ O H - ] = 5"15 • 10-4 at 0~
[EDA]
and
KB~ =
[EDAH22+][OH -]
= 3-66 • 10 -r at O~
[ E D A H +]
(Weast, 1969)
H e n c e , the clay particles w e r e in the p r e s e n c e of
three different species, i.e. E D A , E D A H § and
EDAH22§ the relative c o n c e n t r a t i o n s of which
v a r y with p H (Table 4) and influence the composition of the adsorbate. A t equilibrium the suspensions of samples 3 u n w and 4 u n w g a v e a p H of
approximately 10, at which E D A H + was the pred o m i n a n t species in solution. T h o u g h the selectivity
of charged clay surfaces is usually higher for
divalent than for m o n o v a l e n t cations, and their
acidity higher than that indicated by the p H of the
Table 4. Relative concentrations of EDA,
E D A H § and EDAH~ 2+ species in aqueous
solution at 0~C as a function o f p H
pH
[EDAH~ 2+] : [EDAH +] : [EDA]
3
4
5
6
7
8
9
10
3"66 • 104
10~
102
10
1
l0 -1
10-2
10-3
1
1
1
1
1
1
1
1
11
10 - 4
1
1"95 • 10-8
10-r
10-8
10-5
10-4
10-a
10-2
10-1
1
ADSORPTION OF EDA ON MONTMORILLONITE
suspension, it may be assumed that E D A H + was
the main charge balancing cation 9 Since on removal
of the equilibrium solution by centrifugation the
quantity of diamine retained (expressed in me
N/100 g) amounted to twice the C.E.C. (Fig. 4,b),
suggests this conclusion. Washing again modified
the composition of the adsorbate. The successive
equilibrations with portions of distilled water
caused release of E D A H § ions from the clay surface into the liquid phase 9 But for each such ion
lost, another E D A H + ion, remaining on the clay,
had to be converted into EDAH22+ ion in order to
satisfy charge compensation. The protons necessary for this conversion were produced by the dissociation of water, the hydroxyls insuring the
electrical neutrality of the liquid phase 9 This
process was very slow, as illustrated in Fig. 4,b,
and explains why after three washings the montmorillonite suspension still had a p H of 9 and a N
content exceeding the C.E.C. by roughly 50%.
In an aqueous system, therefore, retention of
excess E D A against washing must not be interpreted (as in dry systems) in terms of competition
between amine and water molecules for hydrogen
bonding with polar NH3 + groups.
Evaporation of the suspensions of the washed
samples 3 and 4 probably did not significantly
modify the status of the adsorbed species 9 The
0
300
~
40
8O
I
Temperature
120
160
I
f
~
200
0
o
220
Ld
E
c
g
u
'180
structural arrangement most compatible with the
data of chemical analysis and equilibrium considerations in relation to p H and charge balancing
requirements would be the following:
H
H
+1
I
H- N-CH2-CHe-N...
f
H
f
H
I
0
2
I
4
i
8
nb
of
washings
Fig. 4. Effect of washing and of degassing under vacuum
at increasing temperatures on the nitrogen content of
different systems9 EDAH2-montmorillonite equilibrated
with 0.017N solution of EDA.2HC1 (a), with 0-017N
solution of EDA (sample 4) (b); 0 washing = equilibrium
solution removed9 EDA-EDAH2-montmorillonite
(sample 4unw), air-dry A, degassed A(c).
(I)
H
This arrangement is also consistent with the appearance of two symmetric NH3 + deformation vibrations, at 1508 and 1538 cm -~ respectively (Figs 9
2c, d and 3B, g). The former might be related to the
terminal NH3 + groups of the trimer, having the
same environment as in pure EDAH2-montmorillonite. The latter might correspond to the NH3 +
groups of the E D A H 2 z+ ion, hydrogen bonded with
the NHz groups of the adjacent E D A H § ions. The
shift to higher frequencies (from 1530 to 1538
cm -x) with respect to hydrated samples suggests
that hydrogen bonds between NH3 + and NH2 were
stronger than between NH3 + and H~O. This seems
quite reasonable, as E D A H + is a stronger base
than water 9 As shown in Table 1, excess retention of E D A against washing is less important on
H-montmorillonite (sample 3) than on E D A H 2 montmorillonite (sample 4). This difference may be
accounted for by a higher proportion of EDAH2 ~§
ions reflecting a higher surface acidity due to the
presence of A P § ions in H-montmorillonite.
It is possible that the charge distribution in the
trimer may be modified in the following manner
H
H
H
H
I
I
I
I
J
N-CH~-CH2-N
I
H
9..
10
H
H
I
H
H
i
6
H
I
I
N-CH~-CH2-N+-H
I
I
9
a
100~
I
H
H
H
--c<..
t+
t
H
I
9
H
+1
H- N-CHe-CH2-N -H
H-+N-CH2-CH2-N+-H...
140
265
H
H
I
I
H-+N-CH~-CH2-N+-H
I
I
H
(II)
H
in order to insure a b e t t e r geometric "fit" with a
particular local charge distribution on the clay
surface 9 As measured on scale models, the nitrogen
atoms in trans E D A are separated by about 4 A,
and according to Pimentel and McClellan (1960)
the average length of a ~ - H . . . N hydrogen bond
266
P. CLOOS and R. D. LAURA
is 3.1 fit. Thus, the extreme positive centers in
the trimeric arrangement would be 18-2 A distant.
On the other hand, assuming a homogeneous
charge distribution on the montmorillonite surface,
it can be calculated that the mean distance between
two negative sites is approximately 12 fit. By an
appropriate translation of the adjacent sheets, one
with respect to the other (which in an aqueous
suspension is easily achievable), a different homogeneous distribution of negative sites in the interlameller space, i.e. one every 6 A alternatively on
the upper and on the lower plate, can be realized.
This configuration should be energetically advantageous, as repulsion between negative charges
is reduced to a minimum. It is interesting to note
that according to this assumption four negative
sites can be distributed over a distance of 18 A.
Such a good fit with the trimeric arrangement might
be a stabilizing factor for this form in the interlamellar space. The observed basal spacings
(Table 2) are consistent with a monolayer of
adsorbed species, the carbon chain being oriented
parallelly to the silicate sheet~ ( L r o n a r d et al.,
1962). In this position only one N - H of each'NHz +
group is able to hydrogen bond with an adjacent
NH2 group. The other two are in contact with the
clay surface and may interact with surface oxygens.
On this basis a trimer of the following configuration
seems to be excluded.
H
H
H... N-CH2-CH2-N -H
\+
+/
H-N-CH2-CH2-N- H
/
H
H
\
H~
-
I
groups and surface hydroxyls. The lower volatility
of E D A with respect to water and the presence of
two polar groups are probably the major reasons
for this behaviour. The absence of the 8 N H r sym.
band at 1508 cm -1 and the presence of the 1538
cm -1 absorption (Figs. 2,e,f and 3C,l,m) suggest
that all NH3 + groups are hydrogen bonded to
NH2 groups. F r o m nitrogen determinations
(Fig. 4,c) it can be inferred that in air-dry films
one N atom out of three carried a positive charge.
These requirements are satisfied by a trimer of
the following structure
q-
H~N-(CH2)z-NH2 . . . H3N-(CH2)2-NH2 9 9 9
H31~-(CH2)2-NH2
(IV)
as suggested by F a r m e r and Mortland (1965). F o r
samples outgassed at room temperature the
N § : N § + N ratio is 1 : 2.5 and increased to 1 : 2.25
after heating at 120~176
Though during this
treatment E D A molecules were desorbed, all
N H r groups remained hydrogen bonded to NH2
groups as evidenced by i.r. spectroscopy (Fig.
3C,m,n). This observation may be accounted for
by the following mechanism involving "condensation" of adjacent E D A H + . . . E D A
associations
with evolution of E D A molecules:
4 H2N-(CH2)2-NH2. 9 9Hzl~I-(CH2)2-NH2
. . . H31~I-(CHs)2-NH2
I
degassing at room temperature
~H
+/
.
2H2N-(CH2)2-NH2[... H31(I-(CH2)2-NH213
. . . H 3 ~ - ( C H z ) 2 - N H 2 + 2H~N-(CH~)2-NH2
H... N-CH2-CH2-N,~H
H
H
(III)
On evaporation of the unwashed clay suspensions (samples 3 and 4) at ambient temperature no
E D A is desorbed (Fig. 4,c). Since water was
removed during this process, equilibria (1) and
(2) in the liquid phase should continuously shift
to the left until the film was air-dry. Degassing at
room temperature caused only partial desorption
of amine, and in the temperature range 120-160~
the nitrogen content in the E D A - E D A H 2 montmorillonite system still amounted to 2.25
times the C.E.C. value (Fig. 4,c). Therefore, it
must be concluded that up to 160~ neutral E D A
molecules were firmly retained on the clay surface,
and competed on a favourable basis with water
molecules for interaction with protonated amine
heating at 120~176
H z N - ( C H z ) 2 - N H 2 [ . . . H31~I-(CH2)2-NH2] 7
. . . H31~-(CH~)2-NH2 + H2N-(CH2)2-NH2.
It is conceivable that, as a consequence of the
condensation process, a redistribution of the positive charges occurs in the "polymeric" associations
in order to fit best the distribution pattern of negative charges on the clay surface. This can be
realized by movement of a proton from one or the
other NH3 + group of an E D A H + ion to a NH2
group of a neighbouring E D A molecule or E D A H §
ion, giving rise to structures of types V and VI.
§
[H2N -(CH2)~-NH3
..
.In H2N-(CH2)2-NH~
[... H31~-(CH2)2-NH2]m
(V)
ADSORPTION OF EDA ON MONTMORILLONITE
H2N-(CH2)2-NH2[. 9 9H31q-(CH2)2-NH2].
. . . n 3~
+
. 9.
-(CH2)2-NH3
[H2N-(CH~)~-i#'IH3 99 .]m H2N-(CH2)2-NHz
(VI)
where n and m vary with the amount of E D A
molecules present and may be equal to 0,1,2 . . . .
A particular feature of the infrared spectra of
unwashed samples 3 and 4 is the broadening of
the deformation band in the 1600 cm -1 region with
the appearance of two maxima near 1600 and 1637
cm -1 (Figs. 2,e,f and 3C,k,l,m,n). The absorption
at 1637 cm -1 is very strong in the air-dry sample,
and on degassing at ambient temperature, decreases much more than the one located at 1600
cm -1. A similar behaviour is shown by the 3362
cm -1 band, assigned to vNH2 asym., with respect
to the absorption at 3226 cm -~. A t first sight one
is tempted to relate this decrease in intensity to the
loss of E D A molecules. But its extent is in no
way proportional to the fraction of E D A lost, and
the respective bands are hardly affected by further
desorption of E D A during heating the clay film.
Therefore, it seems reasonable to assume that the
main contribution to the 3362 and 1637cm -~
bands in the air-dry sample is due to adsorbed
water. On the other hand, since adsorption of E D A
in amounts largely exceeding the C.E.C. caused a
shift of the ~NH3 + sym. vibration to higher frequencies, a similar effect on the ~NH3 + asym.
band would be predicted. Hence, the 1637 and
1600cm -1 absorptions are assigned to 8NH3 +
asym. and 8NH2 sciss, vibrations respectively.
A shift of the deformation bands towards higher
frequencies, as a consequence of hydrogen bonding, is generally accompanied by a shift towards
lower frequencies of the corresponding stretching
vibrations. Therefore, it would be expected that
the prominent band at 3175 cm -~ in pure E D A H 2 montmorillonite would shift to lower frequencies
after adsorption of excess E D A ; however the
reverse is observed. Simultaneously two broad,
diffuse bands develop near 2500-2400 and 2000
cm -a (Fig. 2,e,f), which might be related to
+
N - H . . . N hydrogen bonding. Sample 4w also
shows these bands (Fig. 2,c). In their infrared
studies on hydrogen bonds in some adducts of
phenols with their phenoxides and other oxygen
bases, Had2i et al. (1963) attributed two broad but
discrete maxima near 2500-2600 and 1800-1900
cm -~ to stretching vibrations of O H involved in
strong asymmetrical intermolecular hydrogen
bonds. They also observed that the g-OH frequency increased but slightly. This pattern of
absorption matches fairly well the one discussed
here. The 3226 cm -1 band (Fig. 2,e,f) is probably
267
due to contributions of I~I-H groups not involved
in i ~ - H . . . N associations (as only one out of three
is able to participate in such hydrogen bonds), and
to v N - H sym. vibrations of NH2 groups.
Assuming that isotopic exchange will proceed
faster on NH3 + groups than on NH2 groups, we
deuterated samples containing increasing levels of
E D A to different extents, in order to check the
correctness of our band assignments. F o r this
purpose clay films were degassed and exposed for
1 hr at room temperature to the vapour phase of
H 2 0 - D 2 0 mixtures of varying H~O/D20 ratios.
The samples were again degassed and their i.r.
spectra were recorded. In these experiments the
clay films used were thicker than usual (10-13
mg/cm 2 instead of 3 - 4 mg/cm2), which resulted in
higher absorption intensities, and the recording
rate adopted was slower (0.04 ~/min instead of
0.25 tz/min), which caused an overall shift of the
bands to slightly lower frequencies. Figure 5
compares the spectra of pure EDAH2-montmorillonite and E D A - E D A H 2 - m o n t m o r i l l o n i t e containing an excess of 2 0 0 m e E D A / 1 0 0 g with
respect to the C.E.C. (sample 4 unw) after 50%
and 90% deuteration respectively. In case of unwashed sample 4 (curve b) the high frequency
30
35
F i g . 5. I . R .
40
45
s.o
ss
so
65
xo
spectra of EDAH~-montmorillonito
~s
H
(refor-
once), 50% (a), 90% doutoration (c) and of EDA-EDAH2montmorillonite (sample 4unw), 50% (b) and 90%
deuteration (d).
268
P. CLOOS and R. D. LAURA
band in the 1640-1590cm -1 region, assigned to
~NH3 + asym., disappears almost completely at
50% deuteration, while the low frequency band,
ascribed to 8NH2 sci., is much less affected. Likewise, the ~NH3 + sym. absorption near 1540
cm -1 is no longer visible. I n pure E D A H 2 montmorillonite (curve a), where deuteration could
effect only half of the NH~ + groups, the corresponding bands at 1605 and 1510 cm -a are still present.
Thus, it seems that the 1637 cm -1 band is due to
8NH3 + asym. vibration. In both samples the
1600 cm -1 absorption might contain a contribution
from NH2D + groups, and it is possible that the
new band, appearing after deuteration in the 14201433 cm -1 range, is due to 8 N - H vibration of the
NHD2 + group, as suggested by Powell (1960),
and perhaps of the N H D group in case of sample
4unw. At 90% deuteration (curves c and d) the
1600 cm -a band has disappeared, whilst the 14201433 cm -a absorptions are still well pronounced,
but less intense. On the basis of the proposed
assignment a decrease in intensity would actually
be expected as deuteration becomes nearly
complete. In the 3400-3000 cm -1 region the u N - H
vibrations persist up to 90% deuteration. They
decrease progressively with increasing degree of
deuteration and the corresponding u N - D bands
in the 2400-2000 cm -1 range become stronger and
stronger. A band near 2 7 0 0 c m -1 is obviously
related to physically adsorbed D~O. Its lower
intensity in E D A - E D A H 2 - m o n t m o r i l l o n i t e(curves
b and d) confirms the observation of Servais et al.
(1962), that water is largely replaced by E D A
molecules on the clay surface.
Another interesting feature concerns the absorption intensity near 1835 cm -~. Pure clay shows a
broad band in this region, b u t in sample 4 (curves
b and d) its intensity is considerably higher than in
reference EDAH2-montmorillonite (curves a and
c), though the clay films were of equal thickness.
The only reasonable explanation for the enhancement of intensity in this region is that it is due to
v ~ - D vibrations of N - D . . . N associations, the
hydrogen analogs of which absorb near 2440 cm -a
(Fig. 2,e). The 1980cm -1 band is undistinguishable; it might be hidden by the broad inflexion in
this region, or it might be shifted, on deuteration,
to lower frequencies and overlapped by the strong
~CH2 sci. absorptions near 1 4 6 0 - 1 4 4 7 c m -~. All
the samples show a band at 1914cm -1 which is
probably due to the clay structure, but which
cannot be distinguished on spectra taken with
thinner films.
Whether or not the amount of E D A adsorbed
exceeds the C.E.C. value, heating at 200~ under
vacuum generated NH4 + ions as indicated by the
3280 and 1429 cm -1 bands (Fig. 3, e, j and o). In
+
,
.
E D A - C u - m o n t m o r i l l o n i t e complexes,
NH4 +
formation was also observed in the same experimental conditions, but to a much lower extent
(Laura and Cloos, 1970). This indicates the E D A
is considerably more stable on a montmorillonite
surface when it is coordinated to Cu 2+ ion, than
when it is present in diprotonated, monoprotonated
or neutral form. The fact that NH4 + formation has
already started at 160~ in samples containing
excess amine is not explained (Fig. 3,i and n). It
might be due to a higher degree of dissociation of
residual water, present in smaller amounts in these
samples (Mortland and Raman, 1968).
A c k n o w l e d g m e n t s - T h e grant of a Fellowship to R. D.
Laura by the Belgian Ministry of National Education
during the investigation is gratefully acknowledged.
REFERENCES
Bellanato, J. (1960) I.R. spectra of ethylenediamine
dihydrochloride and other amine hydrochlorides in
alkali halide disks: Spectrochim. Acta 16, 1344-1357.
Conley, R. F. and Lloyd, M. K. (l 971 ) Adsorption studies
on kaolinites--II. Adsorption of amines: Clays and
Clay Minerals 19, 273-282.
Eeckman, J. P. and Laudelout, H. (1961) Chemical
stability of hydrogen-montmorillonite suspensions:
KolloidZ. 178, 99-107.
Farmer, V. C. and Mortland, M. M. (1965) An i.r. study
of complexes of ethylamine with ethylammonium and
copper ions in montmorillonite: J. Phys. Chem. 69,
683-686.
Fripiat, J. J., Servais, A. and L~onard, A. (1962)
Etude de l'adsorption des amines par les montmorillonites-III. La nature de la liaison amine-montmorillonite: Bull. Soc. Chim. Fr. 635-644.
Had~i, D., Novak, A. and Gordon, I. E. (1963) I.R.
spectra of, and hydrogen bonding in, some adducts of
phenols with their phenoxides and other oxygen bases:
J. Phys. Chem. 67, 1118-1124.
Laura, R. D. and Cloos, P. (1970) Adsorption ofethylenediamine (EDA) on montmorillonite saturated with
different cations- I. Copper-montmorillonite: coordination: Proc. Reuni6n Hispano-Belga de Minerales
de la Arcilla, Madrid 76-86.
Lronard, A., Servais, A. and Fripiat, J. J. (1962) Etude
de l'adsorption des amines par les montmorillonitesII. La structure des complexes: Bull. Soc. Chim. Fr.
625-635.
Mortland, M. M. and Barakr, N. (1964) Interaction of
ethylamine and metal ions on montmorillonite: Trans.
8th Intern. Cong. Soil Sci. 3, 433-443.
Mortland, M. M. and Raman, K. V. (1968) Surface
acidity of smectites in relation to hydration, exchangeable cation, and structure: Clays and Clay Minerals
16, 393-398.
Pimentel, G. C. and McClellan, A. L. (1960) The
Hydrogen Bond, p. 289, Freeman, San Francisco.
Powell, D. B. (1960) The i.r. spectrum and the structure
of ethylenediamine dihydrochloride: Spectrochim.
Acta 16, 241-243.
A D S O R P T I O N O F E D A ON M O N T M O R I L L O N I T E
Sabatini, A. and Califano, S. (1960) I.R. spectra in
polarized light of ethylenediamine and ethylenediamine-d4: Spectrochim. Acta 16, 677-688.
Servais, A., Fripiat, J. J. and L6onard, A. (1962) Etude
de l'adsorption des amines par les montmorillonites-I.
269
Les processus chimiques: Bull. Soc. Chim. Fr. 617625.
Weast, R. C. (1969)Handbook of Chemistry and Physics,
5th Edn p. D- 115. The Chemical Rubber Co, Cleveland.
R6surn6-La forme sous laquelle l'6thyl&nediamine (EDA) est adsorb6e ~ partir d'une solution
aqueuse par la montmorillonite saturge en protons et en ions 6thyl~nediammonium est 6tudi6e en
fonction de la quantit6 d'amine pr6sente dans le syst~me.
L ' E D A additionnge ~t l'argile acide en quantit6s plus faibles que ou 6gales h la capacit6 d'6change
cationique (C.E.C.) est exclusivement adsorb6e comme ion 6thyl6nediammonium (EDAH~2+). Lors
d'une addition suppl6mentaire de diamine le pH de la suspension monte h des valeurs alcalines, et
l'esp~ce monoproton6e ( E D A H § est le principal cation compensateur de charge.
L'6vaporation h temp6rature ordinaire des syst~mes "montmorillonite-H-EDA-H~O" ou
" m o n t m o r i l l o n i t e - E D A H 2 - E D A - H 2 0 " contenant 300 me d ' E D A / t 0 0 g d'argile ne provoque pas
de perte d'azote, contrairement au d6gazage sous vide pouss6 (10 -5 mm Hg). N6anmoins des mol6cules d ' E D A en exc&s par rapport h la C.E.C. sont retenues h la surface argileuse, aux d6pens de
mol6cules d'eau, par des ponts hydrog~ne asym6triques forts entre leurs groupes NH2 et les groupes
NH3 + des ions E D A H +. Lors du chauffage sous vide jusqu'~ 160~ le contenu en azote continue
d6croitre, mais se maintient toujours h u n niveau sensiblement sup6rieur ~ la valeur de la C.E.C.,
tandis que tous les groupes NHa + restent engag6s dans de fortes liaisons hydrog6ne. On sugg~re
qu'un processus de "condensation" a lieu, impliquant le dggagement de mol6eules d ' E D A et donnant
naissance h des associations "polym6riques" entre la diamine proton6e et non proton6e.
Le lavage h l'eau distillge des suspensions d'argile ne d6place pas non plus compl~tement l'exc~s
d ' E D A ; cela en raison de l'6quilibre existant entre les esp~ces ioniques en solution (EDAHz ~+ et
E D A H +) et ~t la surface argileuse. I1 semble que ces esp~ces sont adsorb6es pr6f6rentiellement sous
forme d'associations "trim6riques" dans lesqueUes deux des quatre groupes NHa + sont li6s par ponts
hydrog~ne aux groupes NH~.
Apr~s chauffage h 200~ l'azote retenue h la surface de l'argile s'y trouve principalement sous
forme d'ions NH4 +. La formation d'ammonium est favoris6e par la pr6sence d ' E D A en exc~s, et est
consid6rablement plus rapide que darts des syst~mes de montmori//onite contenant de I'EDA coordonn6e aux ions Cu z§
Kurzreferat- Die Form, unter welcher Ethylendiamin (EDA) aus wassriger L6sung von Wasserstoff
- u n d Ethylendiammonium-Montmorillonit adsorbiert wird, wird in Verbindung mit der im System
vorhandenen Aminmenge studiert.
Das dem sauren Ton zugefiigte E D A in Mengen, die das Kationenaustauschverm/agen (K.A.V.)
nicht iiberschreiten, wird ausschliesslich als Ethylendiammonium-ion (EDAH2 ~+) adsorbiert. Bei
weiterer Zugabe von Diamin steigt der Suspensions-pH zu alkalischen Werten, und die monoprotonierte Art ( E D A H +) ist das hauptsachlichste ladungsausgleichende Kation.
Ausdampfen bei Zimmertemperatur von " E D A - H - M o n t m o r i l l o n i t - H 2 0 " oder " E D A - E D A H ~ Montmorillonit-H20" Systemen verursacht keinen Stickstoffverlust, jedoch Ausgasen unter
Hochvakuum (10-amm Hg) wohl. Nichtdestoweniger wird eine Llbermenge yon EDA-molekeln,
im Vergleich zum K.A.V., auf Kosten von Wasser-molekeln an der Tonoberflache mittels starken,
asymetrischen Wasserstoffbriicken zwischen ihren NH2-gruppen und den NH3+-gruppen der E D A H +ionen zuriickgehalten. Wahrend Erhitzen bis zu 160~ unter Vakuum nimmt das Stickstoffgehalt
weiter ab, halt sich jedoch auf einem bedeutend h6heren Welt als das K.A.V., und alle NH3+-gruppen
bleiben in starken Wasserstoffbriicken eingegliedert. Es wird vorgeschlagen, dass ein "Kondensations"-prozess stattfindet whhrend dem EDA-molekeln ausgeschieden werden und "polymerische"
Assoziationen zwischen protoniertem und unprotoniertem Diamin hervorgerufen werden.
Es gelingt auch nicht, den (Jberschuss an E D A durch Waschen der Tonsuspensionen mit destilliertem Wasser ganz zu enffernen; dies als Folge des Gleichgewichts, das zwischen den Ionen-arten
in der L6sung (EDAH2 ~+ und E D A H +) und an der Tonoberflache besteht. Es scheint, dass diese
Arten vorziiglich als "trimerische" Assoziationen, in denen zwei der vier NH3+-gruppen durch Wasserstoffbriicken mit den NH~-gruppen verbunden sind, adsorbiert werden.
Nach Erhitzen auf 200~ ist der auf der Tonoberflache zuriickgehaltene Stickstoff hauptsachlich
in der Form von NH4+-ionen. Die Ammoniumbildung wird durch die Anwesenheit von UberschussE D A begiJnstigt und is bedeutend schneller als in Montmorillonitsystemen, die mit Cu2+-ionen
koordiniertes E D A enthalten.
P e a l o r a e - ~JIa onpe)lenerlri~ l~onaqecTBa aMrIHa B arperaxe, rt3yqanocb KaKrtM o6pa3oM 3TrlJIeH~rtaMHH
(EDA) a~cop6npyerca ~13BO~Hb~XpacTBopoB BO~IOpO~HbIM--rt 3TI~JIeH~4aMMOHffeablMMOHTMOpHflJIOHtITOM.
EDA ~o6aBJIeHHbll~ K KrlC3IOI2FJI~IHeB KOJIHtleCTBeHFI~e H3I!4paBHOM KaTHOHHOO6MeHHO.~ CrlOCO6HOCTFI
270
P. C L O O S
and R. D. LAURA
( C . E . C . ) 6 ~ i n a , ~ c o p 6 H p o B a H IICKJl~Oq!4TenbHO a B i ~ e HOHa 3THJleH~VlaMMO:a~Ifl ( E D A H Z + ) . H p u )~anbHe~tueM ~ o S a s n e H H H ~HaMIIHa, p H a 3 8 e c a ilo,atfnnc• )~0 ~ e n o ~ H o r o aHa~eNHn ~t <(MOHOrIpOTO~IpoBaiiHbt~>>
p n ~ ( E D A H +) cTaYt rnaBHS~M 6 a n a u c H p y m m i i M KaTHOHOM 3 a p n ~ a .
BI, triapHBaHHe n p r t KoMaaTHOR T e M n e p a T y p e a r p e r a T o a < < E D A - H - M O ~ I T M O p r I ~ O H r f T a - H 2 0 > ) I,I~tI
~ E D A - E D A H a - r , IOrtTMOpHnnOm~Ta-H20>), c o ~ e p ~ a m H x 3 0 0 m e rn~tHbt E D A / 1 0 0 e Me BeaeT r n o T e p e
a 3 0 x a , aO ~ e r a 3 i i p o a a n i i e n p H BblCOKOM 8aKyyMe ( 1 0 - s MM H g ) aeCteT. HeCMOTpn n a 3TO, n36b~roK MOneKy~
E D A OTHOCHTenbHO C . E . C . 6 b i n c o x p a a e a IIa n o a e p x n o c T r l r n r i n b t 3 a CqeT 80~aHbtX MO~qeKyJl ~ c n e ~ c T a r I e
CHnbHO~ aCHMMeTpHqHO-~ BO./Iopo~lHO~ CB,q3H Me~Jly r p y r m a M ~ N H 2 r~ N H 3+ I,~OttOa E D A H +. F I p u
a a r p e ~ a n I ~ n d o 1 6 0 ~ nO~ BanyyMOM c o ~ l e p x a H i i e a 3 0 T a ~ 0 6 a B o n u o r~oHa~aeTc~, IIo a c e g e o c T a e T c a a a
3HaaHTem, n o BblC/aleM ypoBHe, qeM 3 a a a e n u e C . E . C . , Bce r p y u n b ~ N H ~ OCTatOTC~ B c ~ n b a o ~ ~ o a o p o ~ H O ~
CB$13H. F I p e ~ n o n a r a r o T , qTo HpoiicXO]](HT npottecc KOH]IeHCaIs
3 a ~ o o q a v o u m g t B c e 6 e 3BOYIIoUHIO MO~leKyYI
E D A H BbI3blBa,IOIIIHPI <(l:[O~liiMepHbte>> aCCOHHalIHH Me)KLIy <(IIpOTOHHIOOBaHHblM>>H ((HeFIpOTOHHpOBaHHbIM)>
]IHaMHHOM.
F I p o M s m K a cycneH3H~t rJtrtHS~ ~IHCTItYlYlHpOBaHHO.~ ao~o~l T a ~ x e nOJ~iiOCTbrO He y ~ l a n a e r H3~blTKa E D A
Bcne2lcTBrle p a ~ H o ~ e c H n c y m e c T B y r o u l e r o Mez<~ly HOHHbIMP[ r p y n n a M ~ B p a c x s o p e ( E D A H ~ + ~ E D A H +)
14 Ha I1oBepxHOCTI4 FYlHHbl. OqeB~4~lHO, 3T~ r p y n n b t H36HpaTeJIbHO aclcop6rlpy~oTcfl KaK (<TpRMeprfMer>
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