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COVER SHEET
Kloprogge, J. Theo (2006) Spectroscopic studies of synthetic and natural beidellites: A review. Applied Clay Science 31:pp. 165-179 Copyright 2006 Elsevier Accessed from: https://eprints.qut.edu.au/secure/00003640/01/SPECTROSCOPIC_STUDIES_OF_SYNTHETIC_AND_NATURAL_BEIDELLITES.pdf
SPECTROSCOPIC STUDIES OF SYNTHETIC AND NATURAL
BEIDELLITES: A REVIEW
J. Theo Kloprogge
Inorganic Materials Research Program, Queensland University of Technology, GPO
Box 2434, Brisbane, Qld 4001, Australia
Correspondence: phone +61 7 3864 2184, fax +61 7 3864 1804, E-mail
Abstract
This paper represents an overview of the spectroscopic studies of both synthetic and
naturally occurring beidellites performed as part of my research over the past 16
years. It shows that detailed information on the local structure of beidellite and
changes in this local structure upon heating can be obtained by combining a range of
spectroscopic techniques such as mid- infrared, near-infrared, infrared emission,
Raman, nuclear magnetic resonance and X-ray photoelectron spectroscopy.
Key words : Beidellite, hydrothermal synthesis, infrared spectroscopy, Raman
spectroscopy, solid state Nuclear Magnetic Resonance spectroscopy, X-ray
photoelectron spectroscopy
Introduction
Clays and more specifically smectites have played an important role in our
society for many decades. Of special interest are modified smectites such as
organoclays (Lagaly, 1984; Breen et al., 1997; Frost and Parker, 1997; Komadel,
1999) and pillared clays with their specific properties in areas such as adsorption,
heterogeneous catalysis and molecular sieving (Ballantine, 1986; Burch, 1988;
Vaughan, 1988; Kloprogge, 1998; Vaccari, 1998; Ding et al., 2001). For example, the
use of clay minerals as heterogeneous catalysts asks for very high phase purity and
well-controlled chemistry. Therefore, synthesis of smectites has become an important
issue due to the high chemical purity and the ability to adjust the synthetic smectite
composition and structure. From this point of view beidellite is the most interesting of
the smectites due to its relatively high acidity and chemical simplicity.
Beidellite is a dioctahedral smectite named after Beidell, Colorado, U.S.A..
Weir and Green-Kelly (1962) and Ross and Hendricks (1945) defined it as the
aluminium endmember of the dioctahedral smectites with a general formula of
(0.5Ca, Na, K)xAl4(Si8-xAlx)O20(OH)4.nH2O based on the material from the Black
Jack Mine, Idaho. Other locations of natural beidellite include Unterrrupsroth
(Germany) and the so-called Ascan beidellite (Besson and Tchoubar, 1972; Tispursky
and Drits, 1984; Nadeau et al., 1985).
Synthesis of beidellite has been described following a variety of methods. A
detailed review on the synthesis of clay minerals including beidellite has been
published in 1999 (Kloprogge et al., 1999b).The earliest reports date back to halfway
the nineteen thirties with the work of Ewell and Insley (1935) who hydrothermally
treated aluminosilicate glasses at temperatures up to 390°C. Granquist and Pollack
(1967) and Granquist et al. (1972) reported on the hydrothermal synthesis of a
randomly interstratified dioctahedral smectite with only aluminium as the octahedral
cation and partial substitution of Al for Si (i.e. beidellite) from ion-exchanged Na-
silicate solutions and gibbsite. The first well defined beidellite crystals were
synthesised by Roy and Sand (1956) from a mixture of oxides at 400°C and 1 kbar for
2 hours. Low temperature hydrothermal experiments at temperatures ranging from
130 to 175°C at pressures to 8.8 bars were tried by De Kimpe (1976). Only in the case
of synthesis at 175°C and a pH of around 8 beidellite was formed. In all other
experiments the resulting materials were either amorphic or contained kaolinite or
zeolites.
In the second half of the sixties and early seventies the first patents were filed
on the synthesis of beidellitic materials aimed at catalytic applications (Capell and
Granquist, 1966; Granquist, 1966; Jaffe, 1974). Plee and coworkers (Plee et al., 1984;
Plee and Fripiat, 1987) and Schutz et al. (1985; 1987) were the first who described the
synthesis of beidellite followed by pillaring with the Al13 Keggin complex in order to
obtain permanent two-dimensional porosity between the clay layers.
This paper aims at giving an overview of a range of spectroscopic methods
used to characterise synthetic and natural beidellites as a part of my ongoing research
during the past 15 years. In addition to the more standard techniques such as Infrared
spectroscopy, examples will be given of information that can be obtained from
techniques such as Infrared Emission Spectroscopy, solid-state NMR and X-ray
photoelectron spectroscopy.
Experimental
Beidellite synthesis
Beidellite with composition Nax(AlVI)4Si8-x(AlIV)xO20(OH)4 have been synthesized
and described by Kloprogge and coworkers (Kloprogge et al., 1990b; 1990c; 1993).
This beidellite was synthesized from gels prepared according to the method of
Hamilton and Henderson (1968). In such a synthesis 50 mg of the stoichiometric Na-
Al-Si gel together with 70 µl water or NaOH solution was placed in a gold capsule
followed by hydrothermal treatment in a Tuttle- type, externally heated, cold-seal
pressure vessel using argon as the pressure medium (Tuttle, 1949). Beidellite BSK3
was synthesized by Yanagisawa et al. (1996) according to the method of Luth and
Ingamells ( 1965). They used a gel prepared from Al(NO3)3.9H2O, NaNO3 and Ludox
colloidal silica. Dried gel powders mixed with various amounts of H2O were treated
in an autoclave at 350°C under autogenous pressure with agitation by turning the
autoclave 20 times/minute in an oven. For this study we used a sample treated for 3
days at 350°C.
Natural beidellite
The natural beidellite was obtained from the CMS Clays Source Repository as sample
CMS Source Clay SBCa-1.
Scanning Electron Microscopy
The morphology of the beidellite was investigated with a Cambridge S150 Scanning
Electron Microscope operating at 15 keV. The sample was coated with carbon prior to
the analysis.
X-ray diffraction (XRD)
The XRD analyses were carried out on a Philips wide angle PW 1050/25 vertical
goniometer equipped with a graphite diffracted beam monochromator. The d-values
and intensity measurements were improved by application of an in-house developed
computer aided divergence slit system enabling constant sampling area irradiation (20
mm long) at any angle of incidence. The goniometer radius was enlarged to 204 mm.
The radiation applied was CuKa from a long fine focus Cu tube operating at 35 kV
and 40 mV. The samples were measured at 50 % relative humidity in stepscan mode
with steps of 0.02° 2? and a counting time of 2s.
Mid-infrared spectroscopy (IR)
All samples were oven dried to remove any adsorbed H2O and stored in a desiccator.
Each sample (1mg) was finely ground for 1 minute, combined with 250 mg oven
dried spectroscopic grade KBr (refractive index of 1.559) and pressed into a disc
using 8 tonnes of pressure for 5 minutes under vacuum. The spectrum of each sample
was recorded in triplicate by accumulating 64 scans at 4 cm-1 resolution between 400
cm-1 and 4000 cm-1 using the Perkin-Elmer 1600 series Fourier transform infrared
spectrometer equipped with a LITA detector. Data interpretation and manipulation
was carried out using the Spectracalc software package GRAMS (Galactic Industries
Corporation, NH, USA) and Microsoft Excel.
Near-infrared spectroscopy (NIR)
The NIR spectroscopy analyses were performed on a Perkin Elmer System 2000 NIR-
spectrometer. For the samples 32 scans were accumulated at a spectral resolution of
16 cm-1 using a mirror velocity of 0.2 cm-1/s to get an acceptable signal/noise ratio.
Fourier transform Infrared Emission Spectroscopy (IES)
FTIR emission spectroscopy was carried out on a Digilab FTS-60A spectrometer,
which was modified by replacing the IR source with an emission cell. A description
of the cell and principles of the emission experiment have been published elsewhere
(Vassallo et al., 1992; Frost et al., 1995). Approximately 0.2 mg of the beidellite
sample was spread as a thin layer on a 6 mm diameter platinum surface and held in an
inert atmosphere within a nitrogen-purged cell during heating. The infrared emission
cell consists of a modified atomic absorption graphite rod furnace, which is driven by
a thyristor-controlled AC power supply capable of delivering up to 150 amps at 12
volts. A platinum disk acts as a hot plate to heat the basic aluminum sulphate sample
and is placed on the graphite rod. An insulated 125-µm type R thermocouple was
embedded inside the platinum plate in such a way that the thermocouple junction was
<0.2 mm below the surface of the platinum. Temperature control of ± 2°C at the
operating temperature of the beidellite sample was achieved by using a Eurotherm
Model 808 proportional temperature controller, coupled to the thermocouple.
The design of the IES facility is based on an off axis paraboloidal mirror with a focal
length of 25 mm mounted above the heater capturing the infrared radiation and
directing the radiation into the spectrometer. The assembly of the heating block, and
platinum hot plate is located such that the surface of the platinum is slightly above the
focal point of the off axis paraboloidal mirror. By this means the geometry is such
that approximately 3 mm diameter area is sampled by the spectrometer. The
spectrometer was modified by the removal of the source assembly and mounting a
gold coated mirror, which was drilled through the centre to allow the passage of the
laser beam. The mirror was mounted at 45°, which enables the IR radiation to be
directed into the FTIR spectrometer. In the normal course of events, 3 sets of spectra
are obtained: 1) the black body radiation over the temperature range selected at the
various temperatures, 2) the platinum plate radiation is obtained at the same
temperatures and 3) the spectra from the Pt plate covered with the sample. Normally
only one set of black body and Pt radiation is required. The emittance spectrum at a
particular temperature was calculated by subtraction of the single beam spectrum of
the Pt backplate from that of the Pt + sample, and the result ratioed to the single beam
spectrum of an approximate blackbody (graphite). This spectral manipulation is
carried out after all the spectral data have been collected.
The emission spectra were collected at intervals of 50°C over the range 200 - 750 °C.
The time between scans (while the temperature was raised to the next hold point) was
± 100 seconds. It was considered that this was sufficient time for the heating block
and the powdered sample to reach temperature equilibrium. The spectra were
acquired by coaddition of 64 scans for the whole temperature range (approximate
scanning time 45 seconds), with a nominal resolution of 4 cm-1. Good quality spectra
can be obtained provided the sample thickness is not too large. If too large a sample is
used then the spectra become difficult to interpret because of self absorption.
Spectral manipulation
Spectral manipulation such as baseline adjustment, smoothing and
normalisation were performed using the Spectracalc software package GRAMS
(Galactic Industries Corporation, NH, USA). Band component analysis was carried
out using the peakfit software package by Jandel Scientific. Lorentz-Gauss cross
product functions were used throughout and peak fitting was carried out until the
squared correlation coefficients with r2 greater than 0.995 were obtained.
Solid-state Magic-Angle Nuclear Magnetic Resonance Spectroscopy (MAS-NMR)
27Al, 29Si and 23Na MAS-NMR spectra were recorded on a Bruker WM500 (11.7
Tesla) at the Department of Physical Chemistry, Faculty of Science, University of
Nijmegen, The Netherlands, at 130.321, 99.346 and 132.258 MHz, respectively.
Chemical shifts are reported in ppm relative [Al(H2O)6]3+ for 27Al, tetramethylsilane
(Me4Si) for 29Si and NaCl for 23Na. The samples were spun at a frequency of
approximately 10.5 kHz for for Al and Si NMR and 3 kHz for Na NMR. Standard 256
Free Induction Decays (FIDs) were accumulated at a repetition time of 1 s.
X-ray Photoelectron Spectroscopy (XPS)
The minerals were analyzed in freshly powdered form in order to prevent surface
oxidation changes. Prior to the analysis the samples were out gassed under vacuum
for 72 hours. The XPS analyses were performed on a Kratos AXIS Ultra with a
monochromatic Al X-ray source at 150 W at the Brisbane Surface Analysis Facility,
University of Queensland, Australia. Each analysis started with a survey scan from 0
to 1200 eV with a dwell time of 100 milliseconds, pass energy of 160 eV at steps of 1
eV with 1 sweep. For the high resolution analysis the number of sweeps was
increased, the pass energy was lowered to 20 eV at steps of 100 meV and the dwell
time was changed to 250 milliseconds.
Results and discussion
Synthetic beidellite
Fig. 1 shows an SEM image of Na-beidellite synthesised at 350°C and 1 kbar for 7
days. In general the beidellite is present as small flakes up to 30 µm with less than
10% amorphous material. At 350 and 400°C beidellite was the predominant
crystalline product (Fig 2a). At pressures above 2 kbar quartz was formed as an
additional crystalline product, while higher temperatures resulted in the formation of
paragonite and metastable cristobalite. Below 250°C kaolinite was formed as the only
crystalline product (Kloprogge et al., 1990c; 1993). The crystallisation of beidellite at
400°C and 1 kbar proceeded quite rapidly in the first 5 days and then slowed down
until a maximum amount of approximately 95 vol.% crystallisation was reached (Fig
2b). XRD data agreed well with results published by Brindley and Brown (1984) and
Weir and Green-Kelly (1962) with a basal spacing of 12.4 Å expanding to 16.5 upon
expansion with ethylene glycol. Saturation with Li and glycerol followed by heating
overnight at 300°C (Hoffmann-Klemen and Greene-Kelly test) resulted in a basal
spacing of 17.7 Å confirming that the smectite formed is indeed beidellite (Kloprogge
et al., 1990a). From a catalytic perspective H+-smectites are of interest. These
catalysts are normally prepared by heat or acid treatment of ammonium-exchanged
smectites. However, it is also possible to synthesise directly ammonium smectites.
Ammonium-beidellite was successfully synthesised by adding glycine to the oxidic
gel similar to that used for the Na-beidellite but without the sodium present followed
by hydrothermal treatment. Similar experiments with ammonium salts and urea were
not successful (Kloprogge and Vogels, 1995).
27Al and 29Si Solid-State NMR of synthetic beidellite
Solid-state NMR of smectites is a useful tool to get a better understanding of possible
substitutions in the octahedral and tetrahedral sheets. The presence of impurities,
especially iron, in the crystal structure can have a distrastrous effect on the quality of
the spectra. However, NMR of synthetic beidellite with no impurities and known
composition will not show these drawbacks. Fig. 3 shows the 27Al and 29Si spectra of
a Na-beidellite with composition Na0.6Al4.6Si7.3O20(OH)4 (Kloprogge et al., 1990d).
The substitution of 0.7Al for Si in the tetrahedral sheet is clearly visible in Fig 3a with
a small peak at 69.9 ppm, while the aluminium in the octahedral sheet is visible as a
much stronger peak at 3.9 ppm. The difference in band width and the sideband
structure made it impossible to directly calculate the substitution. The 29Si NMR
spectrum however could be used to calculate the amount of tetrahedral substitution as
the ratios of the three bands associated with Si(0Al) at 92.7 ppm, Si(1Al) at 88.4 ppm
and Si(2Al) at 83.3 ppm is related to the tetrahedral Al/Si ratio according to the
formula:
210
)212 3/4(2SiSiSiSiSiSi
++−+
Where Si0, Si1 and Si2 represent the intensities of the NMR signals Si(0Al), Si(1Al)
and Si(2Al) (Sanz and Serratosa, 1984). The result was a substitution of about 0.76,
which was, within instrumental accuracy, considered to be similar to the chemical
analysis of 0.7. The peak positions for both the 27Al and 29Si NMR spectra agree
well with those reported by Diddams et al. (1984) for synthetic beidellite and by
Nadeau et al. (1985) for natural beidellite from Unterrupsroth. The results presented
by Plee et al. (1985) for their 29Si spectra are however consistently 3 ppm shifted to
higher values.
Infrared spectroscopy of beidellite
The near- infrared (NIR) spectral region has been defined to extend from
roughly 14285 to 4000 cm-1 (Rossman, 1988; Kloprogge et al., 2000b). The only
vibrations in the NIR region between 4000 and 8000 cm-1 are those associated with
hydrogen atoms associated with hydroxyl groups in the case of micas and with
hydroxyl groups and water in the case of clay minerals. Rossman (1988) reported
average band positions for OH-groups and H2O in the NIR region around 4500 cm-1
as being due to M-OH motions, 5200 cm-1 as the H2O combination mode (bend +
stretch) and around 7100 cm-1 as the first OH stretch overtone. This means that NIR
spectroscopy is a very suitable technique to study phyllosilicates.
In order to come to a detailed interpretation of the NIR spectra of the synthetic
micas and clays it is necessary to have a more detailed understanding of the associated
bands in the mid- infrared spectra of these minerals. Fig. 4 shows the mid- infrared low
frequency region between 400 and 1900 cm-1 and the OH-stretching region between
2900 and 4000 cm-1. Table 1 reports the band centres for the structural OH-bending
and OH-stretching vibrations shown in Fig. 4.
Kloprogge et al. (2000a) have recently reported the effect of increasing layer
charge in synthetic beidellites on their mid- infrared spectra. They showed that an
increase in sodium and aluminium content together with a decrease in silicon content
in the starting gel resulted in an increase in the layer charge of the beidellite
(Kloprogge et al., 1993). However, they found that the resulting clay layer charge
could deviate substantially from the layer charge calculated from the chemical
composition of the initial gel. In this study the difference between starting gel and
product for the low charge beidellite was only small and within approximately 15 %.
For the high layer charge beidellites synthesised from Na1.5 gel the layer charge varied
between 1.68 and 1.87 and for the Na2.0 the layer charge was 1.89 for the beidellite
and 2.0 for the paragonite.
The mid- infrared spectra of the lower charge beidellites (0.6 and 0.7) are very
similar in the Si-O region around 1000 cm-1. The high charge beidellite spectra are
much more similar to the paragonite spectrum. In the low frequency region the OH-
libration modes associated with the octahedral Al-OH groups in the beidellite
structures are observed around, 878-882, 913-920 and 935-965 cm-1. Similar bands
were reported by Farmer (1974) around 915-950 cm-1 for the Al-OH in-plane
librational modes in all dioctahedral species and around 880 cm-1 for the out-of-plane
librational mode in pyrophyllite. Only the last band shows a clear shift towards higher
wavenumbers with increasing layer charge and has been interpreted as the in-plane
vibration (Kloprogge et al., 2000a). Small amounts of other silica species such as
amorphous material or quartz are indicated by the presence of a minor band around
810 cm-1 (Madejova et al., 2000a)..
For beidellite the OH-stretching vibrations are affected by the configuration
and charge distribution in the neighbouring tetrahedral layers. Vedder and McDonald
(1963) have shown that in dioctahedral clay minerals such as beidellite the OH-
transition moment is tilted by a small angle out of the 001 plane. A consequence of
this orientation is that the proton of the OH-group lies closely to two of the six oxygen
atoms at the apices of the tetrahedra forming a hexagonal cavity in the tetrahedral
layer. In the relatively low-charge beidellite structure this results in two OH-stretching
modes, one associated with hydroxyl protons located near charge-bearing oxygen
atoms of the Al substituted hexagonal rings and one associated with neutral oxygen
atoms of non-substituted hexagonal rings. Increasing the layer charge will
consequently be reflected in the intensity ratio between these two OH-stretching
modes. Very dominantly present in the mid- infrared spectra of the beidellites are two
bands due to interlayer water. The interlayer water in the beidellite samples is
characterized by a H2O bending vibration at 1635 cm-1 plus the associated OH-
stretching vibration around 3450 cm-1. This band is most likely associated with water
molecules in the outer hydration sphere of the interlayer sodium cation (Bishop et al.,
1994). The shoulder around 3240 cm-1 was ascribed to interlayer H2O chemically
bound or coordinated to the interlayer cation with an ice-like structure (van der Marel
and Beutelspacher, 1974). Clearly only one Al2OH band can be observed around 3668
cm-1. The small band at 3620 cm-1 is thought to be characteristic for the asymmetric
water OH-stretching vibration associated with the inner hydration shell of the
interlayer cation (Bishop et al., 1994). However, due to the presence of strong water
bands overlapping the 3668 and 3620 cm-1 bands, the positions and intensities of these
bands can deviate significantly and obscure the second Al2OH band. Therefore, no
definite conclusions can be drawn from this region of the mid- infrared spectra.
The NIR spectra of the synthetic beidellites are shown in Fig. 5, while Fig. 6
shows the band component analysis of a low charge beidellite. A detailed list of the
band centers for all samples is given in Table 2. As for the mid- infrared spectra the
NIR spectra of the low charge beidellites are very similar. Band component analysis
indicates the presence of two bands around 4545 (weak) and 4595 (strong) cm-1. This
split disappears in the spectra of the high charge beidellites. The range around 4500
cm-1 is characteristic for the combination bands of the Al-OH-stretching modes and
the Al-OH libration modes around 3660 cm-1 and 880 and 915 cm-1 respectively
(Cariati et al., 1981; 1983a; 1983b; Bishop et al., 1993; Madejova et al., 2000b).
Pyrophyllite shows a strong sharp band around 4615 cm-1 accompanied by two weak
bands at both slightly higher and lower frequencies. The presence of the extra band
around 4548 cm-1 may indicate the presence of a very small amount of beidellite, not
observed in the XRD, corresponding with the band around 854 cm-1 in the mid-
infrared spectrum. Kloprogge et al. (2000b)observed similar bands for both natural
and synthetic pyrophyllites. Clarke et al. (1990) reported a band at 4617 cm-1,which
agrees very well with the band observed in this study at 4615 cm-1, and a weaker band
at 4794 cm-1 with a clear shoulder at 4850 cm-1. This second weaker band with its
shoulder is identical to the two weak bands observed in this study around 4805 and
4844 cm-1.
Three bands can be observed for beidellite around 5140, 5240 and 5260 cm-1.
Isolated water molecules show an absorption band near 5333 cm-1, due to the
combination mode of the stretching and bending modes of the water molecule (Hunt
and Salisbury, 1970). The presence of interlayer water in smectitic clay minerals will
be observed as broad bands close to this position, due to the poorly ordered sites in
the interlayers of a smectitic clay (Clark et al., 1990). In the case of the synthetic
beidellites this means that the first two bands around 5140 and 5240 cm-1 can be
ascribed to the combination modes of interlayer water modes (Bishop et al., 1993).
Similar bands were observed by Sposito et al for montmorillonite around 5130 and
5250 cm-1 (Sposito et al., 1983). Band component analysis indicate that the relatively
broad band around 5250 actually contains two components around 5240 and 5260 cm-
1, which can probably be explained by the fact that a part of the interlayer water is
coordinated to the interlayer sodium cations, while the remaining water molecules are
less tightly bond to the clay structure, in agreement with dehydration studies that
indicate two dehydration stages (Koster van Groos and Guggenheim, 1984a; 1986a;
1987a; Kloprogge et al., 1992a). The strong intensity of these bands are due to the
presence of a relatively large amount of interlayer water. Clearly visible is a decrease
in intensity with increasing layer charge. This increase in layer charge is compensated
by the incorporation of more sodium interlayer cations leaving less interlayer space
for water.
The bands observed in the high wavenumber region can be attributed to the
overtones and combination modes associated with fundamental stretching and
bending modes observed in the mid- infrared region. For the beidellites this region is
relatively complex showing multiple overlapping bands. Two relatively sharp bands
occur around 7100 and 7150 cm-1 plus a much broader band around 6900 cm-1. This
broad band deceases in intensity with increasing layer charge of the beidellite and is
absent in the spectra of the pyrophyllite and paragonite. Therefore, plus the fact that
the free water molecule has an absorbance near 6878 cm-1 (Hunt and Salisbury, 1970;
Sposito et al., 1983), this band must be ascribed to the first overtone of the strongly
hydrogen bonded interlayer water OH-stretching mode (Madejova et al., 2000b). The
7100 cm-1 band is characteristic for the first overtone of the Al-OH stretching modes
of the beidellites. The origin of the second band around 7150 cm-1 is less clear though.
Earlier Infrared Emission Spectroscopy work on synthetic beidellites has shown
however that the broad band around 3660 cm-1 actually consists of two overlapping
Al-OH stretching modes around 3615 and 3650 cm-1 (Kloprogge et al., 1999c), while
montmorillonite SAz shows also two bands around 3622 and 3668 cm-1 after heating
to 110°C (Madejova et al., 2000a). This means that even though the two Al-OH
stretching modes cannot always be identified in the mid- infrared spectra, both bands
do show up in the NIR spectra.
In the very high wavenumber region the low charge synthetic beidellites show a
very weak band around 8670 cm-1. For the high-charge beidellite this band is shifted
to 8631 cm-1. Madejova et al. (2000b) described a similar band around 8661 cm-1 plus
a band at 10550 cm-1 for montmorillonite SAz, which they assigned to the second
overtone and combination of variously bound water molecules. Pyrophyllite exhibits a
weak absorption band at 8122 cm-1, close to the value of 8110 cm-1 reported by Clarke
et al. (1990) for natural pyrophyllite. The interpretation for the second band around
10550 cm-1 given by Madejova et al. (2000b) disagrees with the observations of
Clarke et al. (1990) for pyrophyllite, which has no interlayer water, with a similar
band at 10500 cm-1. A better alternative explanation for this weak band is that it is a
combination band of Al-OH in the phyllosilicate structure. No corresponding band
was observed for the synthetic paragonite in the 8000-10000 cm-1 region.
X-ray photoelectron spectroscopy of beidellite
Photo-electron spectroscopy as an analytical tool has only received limited interest in
the field of mineral science. Photo-electron spectroscopy, together with Auger
electron spectroscopy, gives information about the positions of the energy levels in
atoms or molecules. Therefore can be used to not only obtain a chemical analysis but
high resolution photoelectron spectroscopy can also give more insight in the local
environment of an atom in a crystal structure. In this case, where Al monochromatic
X-rays are used, the technique is known as X-ray Photo-electron Spectroscopy (XPS)
or Electron Spectroscopy for Chemical Analysis (ESCA). Fig. 7 gives an example of
a survey scan of natural beidellite SBCa-1. Each of the peaks visible corresponds not
only to a specific atom but also to a specific energy level in that atom. Table 3 gives
an overview of the transitions observed, the corresponding binding energies and the
chemical composition. The high resolution spectra of Al show two peaks at 74.30 and
74.87 eV associated with the tetrahedral and octahedral Al based on the chemical
composition based on the survey spectra. The high resolution spectrum in the region
of F 1s shows the presence of a trace of F in the beidellite structure.
Thermal behaviour of beidellite: Infrared emission spectroscopy and 23Na Solid-State
NMR
Dehydration reactions can provide important information about the nature of
the interlayer. Commonly used techniques are thermal analysis and differential
thermal analysis (TG and DTA), which show that for most smectites dehydration
takes place in two steps associa ted with a weakly bonded, outer hydration shell
around the interlayer cation and with a more strongly bonded inner hydration shell at
temperatures around 140-150°C and 200-210°C, respectively (Koster van Groos and
Guggenheim, 1984b; 1986b; 1987b; 1989). Solid-state NMR has been used in a
number of studies to elucidate the structural environment of exchangeable cations in
zeolites and clays (Chu et al., 1987; Bank and Ellis, 1989; Janssen et al., 1989; Weiss
et al., 1990a; 1990b).
Kloprogge et al. (1992a) used 23Na MAS-NMR to study the dehydration
behaviour of synthetic beidellite. At room temperature in the hydrated state the
spectrum shows a sharp resonance near 0 ppm, comparable to that observed for Na+ in
solution. This indicates that in the hydrated state the sodium cation behaves similar to
that in solution. Upon dehydration the resonance shifts in a linear fashion to 1.56 ppm
at 105°C, while the linewidth decreases by about one third (Fig. 8). The change in the
local environment upon dehydration and the collapse of the interlayer space makes the
resonance become more positive. Although an exact interpretation of the changes is
difficult, it seems that the tetrahedral sheet and especially the Al3+ substituted
tetrahedra have an increasing influence on the Na+ site. In contrast, no changes are
observed in the 29Si and 27Al spectra of the beidellite with increasing temperature.
Fig. 9a shows the infrared emission spectra of synthetic beidellite from 200° to
750°C. The hydroxyl stretching region between 3000 and 4000 cm-1 clearly shows the
dehydration and dehydroxylation reactions. Although some of the interlayer water has
already disappeared from the interlayer at 200°, still a large band remains visible
around 3420 cm-1 (Fig. 9b), while at 450°C this band has split in two much weaker
bands around 3350 and 3525 cm-1. In addition a band becomes visible at 3720 cm-1
(Fig. 9c). The band at 3720 cm-1 has been assigned to silanol groups that are formed
on the crystal edges during the dehydration and dehydroxylation as an intermediate in
the dehydroxylation as this band is not visible at lower temperatures (Kloprogge et al.,
1999c). Further heating results in a decrease of the Al-hydroxyl modes and the
disappearance of the silanol bands. Associated with the dehydroxylation and the
changes in the hydroxyl stretching region are the changes in the OH-bending and -
libration modes. Two bands at 788 and 820 cm-1 decrease in intensity during heating,
while two other bands at 876 and 929 cm-1 completely disappeared between 650 and
700°C, which indicates that these two bands are the Al-OH bending vibrations. The
other two bands are probably the librational modes. A new band is observed at 722
after the dehydroxylation associated with the formation of new Al-O bonds in the
dehydroxylated beidellite structure.
Pillared beidellite
For the preparation of Al-pillared clays a polyoxycation known as Al13,
[AlO4Al12(OH)24(H2O)12]7+, formed by forced hydrolysis of Al3+ by for example
NaOH, Na2CO3 or decomposition of urea (Akitt and Elders, 1985; 1985b; Bertsch,
1987; Kloprogge et al., 1992b; 1992c) is the mostly used pillaring agent. The cage-
like structure (or Keggin structure) of this complex was proposed for the first time by
Johansson (1960) based on X-ray diffraction work of basic aluminum sulphate. This
structure was later confirmed with other techniques like small-angle X-ray scattering
(Rausch and Bale, 1964) and 27Al NMR (see e.g. review (Akitt, 1989).
Based on differences between the 27Al and 29Si MAS NMR spectra of pillared
beidellite and Mg-smectites, Plee et al. (1985) suggested that calcining of pillared
beidellite results in linking the Al13 species to the tetrahedral layer. This process
involves the inversion of certain tetrahedra and the formation of terminal OH groups
(Si-OH-Al, Chourabi and Fripiat, 1984). Pillared beidellite exhibited basal spacings
around 17.5-18.0 Å after calcination at 350°C while the BET surface area increased to
values around 250 to 300 m2/g (Kloprogge et al., 1994). 27Al solid-state NMR was not
capable of distinguishing separate resonances from the tetrahedrally and octahedrally
coordinated Al in the beidellite structure and the Al13 complex, except for a change in
the relative intensities of both resonances. Upon calcination above 350°C however
two new resonances were observed at 54.9 ppm and 29.6 ppm. A similar resonance at
54 ppm has been reported for tetrahedral Al in zeolites (Fyfe et al., 1983; Kentgens et
al., 1983). In pillared beidellite this resonance might be due to a new tetrahedral Al
environment associated with the formation of a covalent bond between the Al-pillar
and the clay layer.
The structural changes of synthetic beidellite and Al13-pillared analogues
during dehydroxylation were studied in situ using infrared emission spectroscopy.
The OH-stretching region is characterised by 2 OH-stretching modes at 3605 cm-1 and
3650 cm-1. The Al13-pillared beidellite shows stronger OH-stretching bands in
comparison to beidellite alone associated with the water and hydroxyl group initially
present in the Al13 structure, while the silanol band, originally visible in the beidellite
spectra, is absent. The OH-stretching mode of the Al13 is visible around 3450 cm-1 and
a very broad band is present around 3200 cm-1 assigned to water molecules in the Al13
pillar. This band quickly disappears upon heating to 300°C while the OH-stretching
band at 3450 cm-1 diminishes in intensity.
Significant differences between the beidellite and its pillared analogue are the
splitting of the single band at 814 cm-1 into two bands at 812 and 830 cm-1 and the
bands associated with Al-OH modes show increased intensities for the pillared
beidellite (Fig. 10). Secondly the bands associated with Al-OH modes show increased
intensities for the pillared beidellite. This second observation agrees well with earlier
work by Kloprogge et al. (1994), who observed an increase in intensity of the Al-OH
bands at 921 and 849 cm-1 for Al13 pillared montmorillonite Swy-1. Increasing the
temperature results in a decrease in intensity of the bands at 945 and 889 cm-1 and
they disappear at approximately 600° and 700°C respectively. At 650-700°C two new
bands become visible at 642 and 730 cm-1 in both the beidellite and its pillared
analogue. No other bands indicating the formation of new bonds between the
aluminum oxide pillar and the clay structure.
These results show that upon calcination the pillars dehydroxylate, thereby
releasing protons which are able to diffuse through the tetrahedral sheet into the
octahedral sheet where they interact with the structural OH-groups and form water. In
addition the formation of Si-OH- groups is observed in the infrared emission spectra
of the Al13-pillared beidellite indicating that these protons can also interact with Si-O-
Al bonds upon calcination and form new Si-OH-Al bonds. A reaction between the
Al13 pillar and the protonated Si-OH-Al linkage will yield Altetrahedral-O-Alpillar
linkages (Kloprogge and Frost, 1999; Kloprogge et al., 1999a).
Conclusions
This review clearly demonstrates that beidellite can be synthesised in the laboratory.
Since its discovery both natural and synthetic beidellite have been thoroughly
characterised by a large variety of techniques, since beidellite has a for smectites
rather simple chemical composition and for heterogeneous catalysis interesting
acidic/catalytic properties. However, synthesis of beidellite at low temperatures and
pressures has been proven to be elusive. From the perspective of heterogenous
catalysis pillared beidellite would be preferred over other pillared clays. Therefore,
from an applied/industrial perspective the development of a low temperature/pressure
synthesis method is still of interest.
Acknowledgements
This work had not been possible without the help of many colleagues and students.
The author especially wishes to thank Olaf Schuiling, Ben Jansen, John Geus, Ad van
der Eerden, Arno Kentgens, Sridhar Komarneni, Kazumichi Yanagisawa, Jim
Amonette, Barry Wood, Ray Frost, Loc Duong, Liesel Hickey, Ernst Booij, Roland
Vogels and Robin Fry.
References
Akitt, J.W., 1989. Multinuclear studies of alumium compounds. Progress in Nuclear Magnetic Resonance Spectroscopy, 21: 1-149.
Akitt, J.W. and Elders, J.M., 1985. Aluminium-27 nuclear magnetic resonance studies of the hydrolysis of aluminium(III): Part 7. Spectroscopy evidence for the cation Al(OH)2+ from linebroadening studies at high dilution. J. Chem. Soc., Faraday Trans., 81: 1923-1930.
Akitt, J.W. and Elders, J.M., 1985b. The hexa-aquo aluminum cation as reference in aluminum-27 NMR spectroscopy. Possible detection of second sphere effects. J. Magn. Reson., 63: 587-589.
Ballantine, J.A., 1986. The reactions in clays and pillared clays. In: R. Setton (Editor), Chemical reaction in organic and inorganic constrained systems. D. Riedel Publ. Comp., pp. 197-212.
Bank, S.B.J.F. and Ellis, P.D., 1989. Solid-state 113Cd nuclear magnetic resonance study of exchanged montmorillonite. Journal of Physical Chemistry, 93: 4847-4855.
Bertsch, P.M., 1987. Conditions for Al13 Polymer Formation in Partially Neutralized Aluminum. Soil Sci. Soc. Am. J, 51: 825828.
Besson, G. and Tchoubar, D., 1972. Determination du groupde symmetry du feuillet elementaire de la beidellite. Comptes Rendues d'Academie des Sciences Paris, 275: 633-636.
Bishop, J.L., Pieters, C.M. and Burns, R.G., 1993. Reflectance and Mössbauer spectroscopy of ferrihydrite-montmorillonite assemblages as Mars soil analogues. Geochimica et Cosmochimica Acta, 57: 4583-4595.
Bishop, J.L., Pieters, C.M. and Edwards, J.O., 1994. Infrared spectroscopic analyses on the nature of water in montmorillonite. Clays and Clay Minerals, 42(6): 702-716.
Breen, C., Watson, R., Madejova, J., Komadel, P. and Klapyta, Z., 1997. Acid-Activated Organoclays: Preparation, Characterization and Catalytic Activity of Acid-Treated Tetraalkylammonium-Exchanged Smectites. Langmuir, 13(24): 6473-6479.
Brindley, G.W. and Brown, G., 1984. Crystal Structures of Clay Minerals and their X-ray Identification. Mineralogical Society, London.
Burch, R., 1988. Pillared Clays. Catalysis Today, 2(2-3): 185-368. Capell, R.G. and Granquist, W.T., 1966. Cracking catalyst and process of cracking,
U.S. Cariati, F., Erre, L., Micera, G., Piu, P. and Gessa, C., 1981. Water molecules and
hydroxyl groups in montmorillonites as studied by near infrared spectroscopy. Clays and Clay Minerals, 29(2): 157-159.
Cariati, F., Erre, L., Micera, G., Piu, P. and Gessa, C., 1983a. Effect of layer charge on the near- infrared spectra of water molecules in smectites and vermiculites. Clays and Clay Minerals, 31(6): 447-449.
Cariati, F., Erre, L., Micera, G., Piu, P. and Gessa, C., 1983b. Polarization of water molecules in phyllosilicates in relation to exchange cations as studied by near infrared spectroscopy. Clays And Clay Minerals, 31(2): 155-157.
Chu, P.J., Gerstein, B.C., Nunan, J. and Klier, K., 1987. A study by solid-state NMR of 133Cs and 1H of a hydrated and dehydrated cesium mordenite. Journal of Physical Chemistry, 91: 3588-3592.
Clark, R.N., King, T.V.V., Klejwa, M. and Swayze, G.A., 1990. High spectral resolution reflectance spectroscopy of minerals. Journal of Geophysical Research, 95(B8): 12653-12680.
De Kimpe, C.R., 1976. Formation of phyllosilicates from pure silica-alumina gels. Clays and Clay Mineralogy, 24: 200-207.
Diddams, P.A., Thomas, J.M., Jones, W., Ballantine, J.A. and Purnell, J.H., 1984. Synthesis, characterization, and catalytic activity of beidellite-montmorillonite layered silicates and their pillared analogues. Journal of the Chemical Society, Chemical Communications: 1340-1342.
Ding, Z., Kloprogge, J.T., Frost, R.L., Lu, G.Q. and Zhu, H.Y., 2001. Porous clays and pillared clay-based catalysts. Part 2: A review of the catalytic and molecular sieve applications. Journal of Porous Materials, 8: 273-293.
Ewell, R.H. and Insley, P.R., 1935. Hydrothermal synthesis of kaolinite, dickite, beidellite and nontronite. Journal of Research of the National Bureau of Standards, 15: 173-186.
Farmer, V., 1974. The Infrared Spectra of Minerals. Mineralogical Society, England. Frost, R.L., Collins, B.M., Finnie, K. and Vassallo, A.J., 1995. Infrared emission
spectroscopy of clay minerals and their thermal transformations. Clays Controlling Environ., Proc. Int. Clay Conf., 10th: 219-24.
Frost, R.L. and Parker, R.W., 1997. Drift spectroscopy for determination of organic acids on montmorillonite. Mikrochim. Acta, Suppl., 14(Progress in Fourier Transform Spectroscopy): 691-692.
Fyfe, C.A., Thomas, J.M., Klinowski, J. and Gobbi, G.C., 1983. MAS-NMR Spektroskopie und die Struktur der Zeolithe. Angew. Chem.: vol 95, 257-273.
Granquist, W.T., 1966. Synthetic silicate minerals, U.S. A. Granquist, W.T., Hoffmann, G.W. and Boteler, R.C., 1972. Clay mineral synthesis III.
Rapid hydrothermal crystalization of an aluminian smectite. Clays and Clay Minerals, 20: 323-329.
Granquist, W.T. and Pollack, S.S., 1967. Clay mineral synthesis II. A randomly interstratified aluminian montmorillonoid. American Mineralogist, 52: 212-226.
Hamilton, D.L. and Henderson, C.M., 1968. Preparation of silicate composition by a gelling method. Mineral. Mag., 36: 832-838.
Hunt, G.R. and Salisbury, J.W., 1970. Visible and near- infrared spectra of minerals and rocks: I silicate minerals. Modern Geology, 1: 283-300.
Jaffe, J., 1974. hydrothermal method for manufacturing a novel catalytic material, catalysts containing said material and processes using said catalysts, U.S.
Janssen, R., Tijink, G.A.H., Veeman, W.S., Maesen, T.L.M. and van Lent, J.F., 1989. High-temperature NMR study of Zeolite Na-A: detection of a phase transition. Journal of Physical Chemistry, 93: 899-904.
Johansson, G., 1960. Acta Chem. Scand., 14: 771.
Kentgens, A.P.M., Scholle, K.F.M.G.J. and Veeman, W.S., 1983. Effect of hydration o the local symmetry around aluminum in ZSM-5 zeolites studied by aluminum-27 nuclear magnetic resonance. Journal of Physical Chemistry, 87: 4357-4360.
Kloprogge, J.T., 1998. Synthesis of smectites and porous pillared clay catalysts: Review. J. Porous Materials, 5(1): 5-42.
Kloprogge, J.T., Booy, E., Jansen, J.B.H. and Geus, J.W., 1994. The effect of thermal treatment on the properties of hydroxy-Al and hydroxy-Ga pillared montmorillonite and beidellite. Clay Minerals, 29: 153-167.
Kloprogge, J.T. and Frost, R.L., 1999. Infrared emission spectroscopy of Al-pillared beidellite. Applied Clay Sciencce, 15: 431-445.
Kloprogge, J.T., Fry, R. and Frost, R.L., 1999a. An infrared emission spectroscopic study of the thermal transformation mechanisms in Al13-pillared clay catalsts with and without tetrahedral substitutions. J. Catalysis, 184: 157-171.
Kloprogge, J.T., Hickey, L. and Frost, R.L., 2000a. The effect of increasing layer charge on the infrared absorption spectra of synthetic beidellites. Journal of Materials Science Letters, 19(13): 1131-1134.
Kloprogge, J.T., Jansen, J.B.H. and Geus, J.W., 1990a. Characterization of synthetic Na-beidellite. Clays and Clay Minerals, 38(4): 409-414.
Kloprogge, J.T., Jansen, J.B.H. and Geus, J.W., 1990b. Characterization of synthetic sodium-beidellite. Clays Clay Miner., 38(4): 409-14.
Kloprogge, J.T., Jansen, J.B.H., Schuiling, R.D. and Geus, J.W., 1992a. The interlayer collapse during dehydration of synthetic Na0.7-beidellite: A 23Na solid state Magic-Angle spinning NMR study. Clays and Clay Minerals, 40(5): 561-566.
Kloprogge, J.T., Komarneni, S. and Amonette, J.E., 1999b. Synthesis of smectite clay minerals: A critical review. Clays and Clay Minerals, 47(5): 529-554.
Kloprogge, J.T., Komarneni, S., Yanagisawa, K., Fry, R. and Frost, R.L., 1999c. Infrared emission spectroscopic study of the dehydroxylation via surface silanol groups of synthetic and natural beidellite. J. Colloid and Interface Science, 212: 562-569.
Kloprogge, J.T., Ruan, H. and Frost, R.L., 2000b. Near- infrared spectroscopic study of synthetic and natural pyrophyllite. Neues Jahrbuch für Mineralogie, Monatshefte(8): 337-347.
Kloprogge, J.T., Seykens, D., Geus, J.W. and Jansen, J.B.H., 1992b. A 27Al nuclear magnetic resonance study on the optimalization of the development of the Al13 polymer. Journal of Non-Crystalline Solids, 142: 94-102.
Kloprogge, J.T., Seykens, D., Geus, J.W. and Jansen, J.B.H., 1992c. Temperature influence on the Al13 complex in partially neutralized aluminum solutions: an aluminum-27 nuclear magnetic resonance study. J. Non-Cryst. Solids, 142(1-2): 87-93.
Kloprogge, J.T., van, d.E.A.M.J., Jansen, J.B.H. and Geus, J.W., 1990c. Hydrothermal synthesis of Na-beidellite. Geologie en Mijnbouw, 69(4): 351-357.
Kloprogge, J.T., Van der Eerden, A.M.J., Jansen, J.B.H. and Geus, J.W., 1990d. Hydrothermal synthesis of sodium-beidellite. Geol. Mijnbouw, 69(4): 351-7.
Kloprogge, J.T., van der Eerden, A.M.J., Jansen, J.B.H., Geus, J.W. and Schuiling, R.D., 1993. Synthesis and paragenesis of Na-beidellite as a function of temperature , water pressure, and sodium activity. Clays and Clay Minerals, 41(4): 423-430.
Kloprogge, J.T. and Vogels, R., 1995. Hydrothermal synthesis of ammonium-beidellite. Clays and Clay Minerals, 43(1): 135-137.
Komadel, P., 1999. Structure and chemical characteristics of modified clays. NATO Sci. Ser., Ser. E, 362(atural Microporous Materials in Environmental Technology): 3-18.
Koster van Groos, A.F. and Guggenheim, S., 1984a. The effect of pressure on the dehydration reaction of interlayer water in. Am. Mineral, 69: 872-879.
Koster van Groos, A.F. and Guggenheim, S., 1984b. The effect of pressure on the dehydration reaction of interlayer water in Na-montmorillonite (SWy-1). American Mineralogist, 69: 872-879.
Koster van Groos, A.F. and Guggenheim, S., 1986a. Dehydration of K-exchanged montmorillonite at elevated temperatures and. Clays & Clay Minerals, 34: 281-286.
Koster van Groos, A.F. and Guggenheim, S., 1986b. Dehydration of K-exchanged montmorillonite at elevated temperatures and pressures. Clays and Clay Minerals, 34: 281-286.
Koster van Groos, A.F. and Guggenheim, S., 1987a. Dehydration of a Ca- and a Mg-exchanged montmorillonite (SWy-1) at elevated pressures. Am. Mineral, 72: 292-298.
Koster van Groos, A.F. and Guggenheim, S., 1987b. Dehydration of a Ca- and a Mg-exchanged montmorillonite (SWy-1) at elevated pressures. American Mineralogist, 72: 292-298.
Koster van Groos, A.F. and Guggenheim, S., 1989. Dehydroxylation of Ca- and Mg-exchanged montmorillonite'. Am. Mineral, 74: 627-636.
Lagaly, G., 1984. Clay organic reactions. Phil. Trans. R. Soc. Lond., A311: 315-332. Luth, W.C. and Ingamells, C.O., 1965. Gel preparation of starting materials for
hydrothermal experimentation. American Mineralogist, 50: 255-258. Madejova, J., Bujdak, J., Petit, S. and Komadel, P., 2000a. Effects of chemical
composition and temperature of heating on the infrared spectra of Li-saturated dioctahedral smectites. (I) Mid- infrared region. Clay Miner., 35(5): 739-751.
Madejova, J., Bujdak, J., Petit, S. and Komadel, P., 2000b. Effects of chemical composition and temperature of heating on the infrared spectra of Li-saturated dioctahedral smectites. (II) Near- infrared region. Clay Miner., 35(5): 753-761.
Nadeau, P.H., Farmer, V.C., McHardy, W.J. and Bain, D.C., 1985. Compositional variation of the Unterrupsroth beidellite. American Mineralogist, 70: 1004-1010.
Plee, D., Borg, F., Gatineau, L. and Fripiat, J.J., 1985. High-resolution solid-state 27Al and 29Si nuclear magnetic resonance study of pillared clays. Journla of the American Chemical Society, 107: 2362-2369.
Plee, D. et al., 1984. Zeolite-like materials from clays, France. Plee, D.G.L. and Fripiat, J.J., 1987. Pillaring processes of smectites with and without
tetrahedral substitutions. Clays & Clay Minerals, 35: 81-88. Rausch, W.V. and Bale, H.D., 1964. Small-angle X-ray scattering from hydrolyzed
aluminum nitrate solutions. J. Chemical Physics, 40: 3391-3394. Ross, C.S. and Hendricks, S.B., 1945. Minerals of the montmorillonite group. U.S.
Geological Survey Professional Papers, 205-B. Rossman, G.R., 1988. Vibrational spectroscopy of hydrous components. In: F.C.
Hawthorne (Editor), Spectroscopic methods in mineralogy and geology. Reviews in Mineralogy. Mineralogical Society of America, Washington D.C., pp. 193-206.
Roy, R. and Sand, L.B., 1956. A note on some properties of synthetic montmorillonites. American Mineralogist, 41: 505-509.
Sanz, J. and Serratosa, J.M., 1984. 29Si and 27Al high-resolution MAS-NMR spectra of phyllosilicates. Journal of the American Chemical Society, 106: 4790-4793.
Schutz, A. et al., 1985. Acidity and catalytic properties of pillared montmorillonite and beidellite. Proceedings of the International Clay Conf. Denver 1985: 305-310.
Schutz, A., Stone, W.E.E., Poncelet, G. and Fripiat, J.J., 1987. Preparation and characterisation of bidimensional zeolitic structures obtained from synthetic beidellite and hydroxy-aluminum solutiions. Clays and Clay Minerals, 35: 251-261.
Sposito, G., Prost, R. and Gaultier, J.-P., 1983. Infrared spectroscopic study of adsorbed water on reduced-charge Na/Li-montmorillonites. Clays and Clay Minerals, 31(1): 9-16.
Tispursky, S.I. and Drits, V.A., 1984. The distribution of octahedral cations in the 2:1 layers of dioctahedral smectites studied by oblique-texture electron diffraction. Clay Minerals, 19: 177-193.
Tuttle, O.F., 1949. Two pressure vessels for silicate-water studies. Geol. Soc. Amer. Bull., 60: 1727-1729.
Vaccari, A., 1998. Preparation and Catalytic properties of cationic and anionic clays. Catalysis Today, 41: 53-71.
van der Marel, H.W. and Beutelspacher, H., 1974. Atlas of infrared spectroscopy of clay minerals and their admixtures. Elsevier, Amsterdam, 396 pp.
Vassallo, A.M., Cole-Clarke, P.A., Pang, L.S.K. and Palmisane, A., 1992. Infrared emission spectroscopy of coal minerals and their thermal transformation. J. Applied Spectroscopy, 46: 73-78.
Vaughan, D.E.W., 1988. Pillared clays - A historical perspective. Catalysis Today, 2(187-198).
Vedder, W. and McDonald, R.S., 1963. Vibrations of the OH ions in muscovite. the Journal of Chemical Physics, 38(7): 1583-1590.
Weir, A.H. and Green-Kelly, R., 1962. Beidellite. American Mineralogist, 47: 137-146.
Weiss, C.A., Kirkpatrick, R.J. and Altaner, S.P., 1990a. The structural environments of cations adsorbed onto clays: 133Cs variable temperature MAS NMR spectroscopic study of hectorite. Geochimica et Cosmochimica Acta, 54: 1655-1669.
Weiss, C.A., Kirkpatrick, R.J. and Altaner, S.P., 1990b. Variations in interlayer cation sites of clay minerals as studied by 133Cs MAS nuclear magnetic resonance spectroscopy. American Mineralogist, 75: 970-982.
Yanagisawa, K. et al., 1996. hydrothermal synthesis of Na-beidellite from coprecipitated gel. Journal of Materials Science Letters, 15: 861-863.
Table 1. Mid-infrared spectral analysis (in cm-1) of the OH band centres of synthetic beidellite with increasing layer charge (assignment after (Farmer,
1974)).
Sample x Al-OH
lib Al-OH
lib Al-OH
lib Al-OH stretch
Al-OH stretch
B0.6 0.6 beidellite 882 913 934 3668 B0.7-2 0.7 beidellite 882 912 933 3662 B0.7-1 0.7 beidellite 882 915 936 3663 B1.5 1.5 beidellite 880 919 966 3638 B2.0 2.0 beidellite 878 913 965 3634
Table 2. Near-infrared band centres (in cm-1) of synthetic beidellite with increasing layer charge
Sample x
B0.6 0.6 4536 4597 - 5140 5237 5260 6963 7106 7160 B0.7-2 0.7 4553 4596 - 5139 5233 5258 6939 7073 7140 B0.7-1 0.7 4543 4596 - 5144 5241 5259 6999 7098 7157 B1.5 1.5 - 4571 - 5075 5172 5233 6938 7099 - B2.0 2.0 - 4570 - 5158 - 5221 6866 7094 -
Table 3a Element Binding energy (eV) FWHM (eV)
O 1s 530.0 2.903 Si 2p 101.0 2.789 Al 2p 72.5 2.725 Fe 2p 711.0 5.037 Mg 2s 87.0 2.906 Ca 2p 349.5 4.421 K 2p 291.0 4.422 Na 1s 1070.0 2.757
Table 3b
Element Atom % composition O 71.5 O: 20 OH: 4 H2O: 8
Si 15.2 6.78 Al 10.0 Tet: 1.22 Oct: 3.24
Fe3+ 1.4 0.62 Mg 1.0 Oct: 0.24
Int: 0.21 Ca 0.7 0.31 K 0.2 0.09 Na 0.05 0.02
Fig. 1
Fig. 2a
Fig. 2b
Fig. 3a
Fig. 3b
400 450 500 550 600 650 700 750 800 850
Wavenumber (cm-1)
Abs
orba
nce 429 cm-1
472 cm-1
531 cm-1
554 cm- 1
586 cm-1
630 cm-1
709 cm-1785 cm -1
813 cm -1
Fig. 4a
850 950 1050 1150 1250 1350
Wavenumber (cm-1)
Abs
orba
nce
882 cm-1
915 cm-1
936 cm-1
1026 cm -1
1058 cm-1
1117 cm-1
1219 cm-1
Fig. 4b
3000 3100 3200 3300 3400 3500 3600 3700 3800 3900 4000
Wavenumber (cm-1)
Abs
orba
nce
3240 cm -1
3450 cm-1
3668 cm -1
3620 cm-1
Fig. 4c
4400 4800 5200 5600 6000 6400 6800 7200
Wavenumber/cm-1
Rel
. Abs
orba
nce
B2.0
B1.5
B0.7-2
B0.6
B0.7-1
Fig. 5
0
0.1
0.2
0.3
0.4
0.5
0.6
4400 4800 5200 5600 6000 6400 6800 7200
Wavenumber/cm-1
Abs
orba
nce
4536 cm-1
4597 cm-1
5140 cm-1 5260 cm-1
5237 cm-1
6963 cm-1
7106 cm-1 7160 cm-1
Fig. 6
Fig. 7
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
25 35 45 55 65 75 85 95 105
Temperature (oC)
Che
mic
al s
hift
(ppm
)
20
22
24
26
28
30
32
34
36
FWH
M (
Hz)
Fig. 8
450 950 1450 1950 2450 2950 3450 3950
Wavenumber/cm-1
Rel
ativ
e E
mis
sivi
ty
200°C
750°C
Fig. 9a
3000 3100 3200 3300 3400 3500 3600 3700 3800 3900 4000
Wavenumber/cm-1
Rel
ativ
e E
mis
sivi
ty
Al-OH stretching modes
interlayer H2O
Synthetic beidellite at 200oC
Fig. 9b
3000 3100 3200 3300 3400 3500 3600 3700 3800 3900 4000
Wavenumber/cm-1
Rel
ativ
e E
mis
sivi
ty
strongly bonded interlayer H2O
Al-OH stretching modes
Si-OH mode
Synthetic beidellite at 450oC
Fig. 9c
450 550 650 750 850 950 1050 1150
Wavenumber/cm-1
Rel
ativ
e E
mis
sivi
ty
750°C
200°C945 cm-1
889 cm-1
812cm-1
627 cm-1
534 cm-1478 cm-1
830 cm-1
642 cm-1 730 cm-1
Fig. 10