Using Kaolinitic Clay for Preparation of a Hydrotalcite-Like Compound

doi:10.4236/msa.2011.26094

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Materials Sciences and Applicatio ns, 2011, 2, 684-691

doi:10.4236/msa.2011.26094 Published Online June 2011 (http://www.SciRP.org/journal/msa)

Using Kaolinitic Clay for Preparation of a

Hydrotalcite-Like Compound

Khaled Hosni*, Ezzeddine Srasra

Centre National des recherches en Sciences des Matériaux, Pôle technologique de Borj Cedria, Nabeul, Tunisia.

Email: [email protected]

Received December 24th, 2010; revised March 21st, 2011; accepted May 18th, 2011.

ABSTRACT

In this study, Mg-Al-CO3 hydrotalcite was synthesized from a kaolinite as natural source aluminium using two simple

methods. The first method uses the kaolinite in natural solid state, the second method use the filtrate of the kaolinite

after dissolution by acidic solutions. The structure of the materials was characterized by X-ray diffraction, Fourier

transform infrared spectroscopy, differential scanning calorimetry (DSC) and Brunauer, Emmett, and Teller (BET)

measurements.

Keywords: Hydrotalcite, Kaolinite, Layered Compound, XRD, Memory Effect

1. Introduction

A wide range of compositions are possible for synthetic

hydrotalcites based on the general formula

II IIIy+n

[ML(OH)][X][H O]



1-yy2y/n2z , where MII and MIII are

the divalent and trivalent cations in the octahedral posi-

tions within the hydroxide layers. The value y can have a

range between 0.17 and 0.33, while Xn– is an interlayer

anion with a negative charge n– [1,2], and z is the number

of water molecules. Many anions or anionic complexes,

both organic and inorganic, can be incorporated into the

hydrotalcite structure. The hydrotalcite can be abbrevi-

ated as [MII – MIII – X], where, MII = Mg2+, Zn2+, Cu2+,

Ca2+, Mn2+; MIII = Al3+, Cr3+, Fe3+, ; and Xn– = Cl–,

NO3–, CO3–, , etc.



Hydrotalcite-like compounds, also called layered dou-

ble hydroxides (LDHs), have received considerable at-

tention in recent years owing to their layered structure

and high anion-exchange capacity [3], which makes them

potential materials for technical applications in various

domains [4]. These materials have been investigated as

solid ionic conductors [5] and sensors [6]. Layered dou-

ble-metal hydroxides are, or may be used as, catalysts

[4,7], photo-catalysts, catalyst supports [8], adsorbents

[9,10], anion exchangers [11], medicines [12,13] and

bonding materials. The reason for the potential applica-

tion of hydrotalcites as catalysts rests with their ability to

make mixed metal oxides at the atomic level, rather than

the particle level. Such mixed metal oxides are formed

through the thermal decomposition of the hydrotalcite

[14]. Also, LDH materials have been extensively studied

in terms of their thermal evolution [15,16], textural

properties [16], and the formation of nanosized metal

particles [17] as well as for environmental purposes [18].

The present study reports simplified method to synthe-

size the carbonate forms of layered double hydroxides

from a natural source of trivalent cations. Mg-Al-CO3

hydrotalcite-like layered compounds have been synthe-

sized with Mg/Al ratios of 3 by a mechanochemical

method using kaolinite in solid state and by coprecipita-

tion using the under product of the acidic dissolution of

the kaolinite.

2. Experimental

2.1. Material Preparation

The Mg-Al-CO3 hydrotalcite-like layered compounds has

been synthesized by two simple methods using kaolinite

as a natural source of trivalent cations and an aqueous

solution of Na2CO3 as the precipitant.

Method 1

The sample was synthesized by crushing kaolinite with

the magnesium nitrate hexahydrate (their amounts were

so as to have the desired Mg2+/Al3+ molar ratio), fol-

lowed by heating at 500˚C for 4 hours. The product ob-

tained was dispersed under constant stirring in an aque-

ous solution containing Na2CO3 (100 mL). The pH of the

dispersion was maintained constant at 10 ± 0.1 by adding

NaOH or HNO3 when necessary. The slurry was subse-

Using Kaolinitic Clay for Preparation of a Hydrotalcite-Like Compound685

quently agitated at room temperature for 24 h, and then

aged at 150˚C for 24 h. The resulting products were col-

lected by centrifugal separation and washed thoroughly

with deionised water to eliminate excess Na+ followed by

drying overnight at room temperature.

The samples were identified as [Ksd3P10-T150], where

Ksd represents the trivalent cation source (kaolinite) used

to prepare the materials and “sd” represents the solid

state. For example, Ksd3P10-T150 stands for the product

prepared with kaolinite in solid state, a Mg/Al ratio of 3,

an aging temperature of 150˚C, and a pH of synthesis of

10.

Method 2

The sample was synthesized using as aqueous solution

of Na2CO3 as precipitant. The solutions containing

Mg(NO3)2·6H2O and Al3+, cation resulting from dissolu-

tion of the purified kaolinite by acidic attack, (their con-

centration varied so as to have the Mg/Al molar ratio of 3)

were added dropwise to the aqueous solutions of Na2CO3

with vigorous stirring. The pH of the dispersion was

maintained constant at 10 ± 0.1 by adding NaOH (10%).

The slurry was subsequently agitated at room tempera-

ture for tree day. The resulting products were collected

by centrifugal separation and washed thoroughly with

deionised water to eliminate excess Na+ followed by

drying overnight at room temperature.

The samples were identified as [Kliq3P10], where Kliq

represents the trivalent cation source (kaolinite) used to

prepare the materials and “liq” represents its liquid state.

For example, Kliq3P10 stands for the product prepared

with kaolinite in liquid state, an Mg/Al ratio of 3 and a

pH of synthesis of 10.

2.2. Characterization of Materials

The dried precipitates were characterized by X-ray dif-

fraction (XRD) in order to determine the species present

and their degree of crystallinity. Diffractograms were

obtained by using a ‘PANalytical X’Pert HighScore Plus’

diffractometer using monochromated CuKα radiation.

Nitrogen adsorption measurements were performed at

–196˚C with an Autosorb-1 unit (Quantachrome, USA)

for the determination of sample textural properties using

the multipoint Brunaner-Emmet-Teller (BET) method.

The samples were out gassed at 120˚C under a vacuum at

10–3 mmHg for 3.5 h. Fourier-transformed infrared (FT-IR)

spectra were recorded as KBr pellets using a Perkin-

Elmer FT-IR (model 783) instrument. KBr pellets were

prepared by mixing 5 wt% anionic clay with 95 wt%

KBr and pressing. Differential scanning calorimeter

(DSC) experiments were performed with Mettler Tole-

deo DSC-823 type thermal analyzer at heating rates of

20.0˚C·min–1.

3. Results and Discussion

3.1. Characterization of the Clay

The sample selected for this study is Tabarka clay (Tuni-

sian clay).

3.1.1. X-Ray Diffrac ti on

The nature of the impurities was determined by exam-

ining the crude samples. Quartz (reflection at 3.35 Å) is

the major impurity. The diffractogramme of purified

sample (Figure 1(a)) show the reflections at d = 7.21 Å

and 10.05 Å characteristic of the kaolinite and illite re-

spectively [19].

In Figure 1(b) is shown the powder XRD pattern of

the mixture of kaolinitic clay and the magnesium nitrate

after heating at 500˚C. Owing to the fact of the absence

of the peak corresponding of the d-spacing of 7.21 Å and

attributed of the kaolin in the XRD pattern of the product

shows that the structure of the original clay is completely

destroyed and indicates metal oxide peaks, suggesting an

almost total decomposition of the original clay. This ob-

servation is consistent with the result given by the study

of the thermal stability for the clay sample. Indeed, heat-

ing the sample clay in air above 500˚C (Figure 2(b)), the

peak at 7.21 Å disappears while the peak characteristic of

illite (d = 10.05 Å) persists. The treatment with ethylene

glycol does not have any effect (Figure 2(c)).

3.1.2. Infrared Spectra

Figure 3(a) shows the Infrared spectra of purified clay

over the frequency range of 4000 - 400 cm–1. The figure

shows that purified sample contain quartz (800 cm–1).

The spectrum exhibited the characteristic band at 3697

cm–1 confirming the dominant presence of kaolinite. The

band, at 1637 cm–1 and 3450 cm–1 corresponds to the

bonding modes of absorbed and zeolitic water.

3.1.3. Chemi c al Comp osition

The purified clay sample was attacked by a mixture of

three acids (HCl, H2SO4, and HNO3). All elements were

dissolved into solution expect for the Si which was de-

termined by gravimetric method analysis. The Al and Fe

were assayed by atomic absorption spectrophotometer

(AAS Vario 6). The chemical composition data (Table 1)

indicates that the percentage of Al2O3 is 30 % confirming

that sample is kaolinitic clay

3.2. Characterization of the Kliq3P10-LDH and

Ksd3P10-LDH

3.2.1. Powder X-Ray Diffraction

Figure 1 shows the XRD patterns for the precipitates

obtained by method 1 and method 2. It is shown that the

Ksd3P10-LDH and Kliq3P10-LDH samples patterns (Fig-

ures 1(c) and 1(d)) were comparable to that pattern of

Using Kaolinitic Clay for Preparation of a Hydrotalcite-Like Compound

686

Figure 1. X-ray patterns of clay sample: (a) purified clay; (b) Clay + Mg(NO3)·6H2O and heated at 500˚C; (c) Ksd3P10- T150;

(d) Kliq3P10. [(K) Kaolinite, (I) Illite, (Q) Quartz, (H) hydrotalcite.

Table 1. The chemical composition of the purified clay.

% SiO2 Al2O3 Fe2O3 CaO Na2O MgO K2O Ignition loss

Clay 48.75 30 3.39 0.33 1.45 0.07 1.95 13.93

the sample prepared by the conventional method. The

Kliq3P10-LDH sample showed a layered structure as ob-

served from the peaks at 7.82, 3.89 and 2.61 Å, corre-

sponding to planes (003), (006) and (009) for a layered

hydrotalcite-like material, respectively [20]. The

Ksd3P10-LDH sample display very weak and broad peaks

at a 2θ value of 11˚ compared to the sample prepared by

coprecipitation at the same conditions (pH = 10 and

Mg2+/Al3+ = 3). Ksd3P10-LDH shows a structure different

from the previous samples; it was an ill-defined hydro-

talcite contaminated with argillaceous phase (d = 4.5Å).

3.2.2. IR Spectroscopy

The FT-IR spectra of the Ksd3P10-LDH and Kliq3P10-

LDH hydrotalcite are presented in Figures 3(b) and 3(c).

It shows a broad band around 3470 cm–1 due to the

stretching mode of the structural –OH groups in the

metal hydroxide However, a small shoulder at 2900 -

3000 cm–1 suggests the presence of a second type of –OH

stretching vibration (possibl due to hydrogen bonding

Figure 2. X-ray patterns of: (a) oriented crude simple; (b),

oriented heated sample; (c) oriented sample treated with

glycol. y

Using Kaolinitic Clay for Preparation of a Hydrotalcite-Like Compound 687

Figure 3. Infrared spectra of: (a) purified clay; (b) Ksd3P10-T150; (c) Kliq3P10.

with carbonate in the interlayer spacing [21].

The two spectra show:

1) A shoulder at 1638 cm–1 is ascribed to the bending

mode of the interlayer water molecules [22].

2) The three characteristic bands of carbonate in hy-

drotalcite at around 1384 cm–1 (ν3), 877 cm–1 (ν2) and

~1020 cm–1 (ν1) [23,24].

3) The bands around 420 and 668 cm–1, which are as-

cribed to the bending mode Al-O and Mg-O.

The infrared spectrum of the Kliq3P10-LDH shows ad-

ditional bands appearing at 1193 and 1100 cm–1 which

could not be identified.

3.2.3. Surface Area and N2 Adsorption-Desorption

Studies

The N2 adsorption-desorption isotherm is of type II for

all samples, which is typical of mesoporous materials

(Figure 4) [25]. All of the materials possessed zero mi-

cropore volume. Adsorption isotherms of this type are

represented by mesoporous materials with no micropores

and strong interactions between adsorbent and adsorbate

molecules. This type of hysteresis loop is formed when

the adsorption and desorption curves do not coincide and

is caused physically by the phenomenon of capillary

condensation in the mesopores.

From Figure 4, it was determined that all samples

shows a horizontal course of the hysteresis branch over

an appreciable range of gas uptake (p/p0 ≥ 0.6), while it

is vertical above this ratio. This type of hysteresis loop is

often observed with aggregates of plate-like particles that

give rise to slit-shaped pores.

The textural properties for samples prepared by dif-

ferent method are gathered in Table 2. Starting from

these results we can conclude that Ksd3P10-LDH presents

significant textural properties. Indeed, the value of spe-

cific surface area (80 mg·g–1) is near that obtained for the

sample prepared by conventional method. While,

Kliq3P10-LDH prepared by method 2 has a very weak

value of specific surface area.

3.2.4. DSC St udy

The DSC curves of the Kliq3P10 and Ksd3P10 hydrotal-

cite prepared by mechanochemical synthesis method and

co-precipitation method usning kaolinite clay as aluminum

Using Kaolinitic Clay for Preparation of a Hydrotalcite-Like Compound

688

Figure 4. N2 adsorption-desorption isotherms: (a) Ksd3P10-

LDH; (b) Kliq3P10-LDH.

Table 2. Textural properties for various sorbent samples.

KsdP10 KLiqP10

SBET

(m2/g)

Vmacropore

(cm3/g) SBET

(m2/g)

Vmacropore

(cm3/g)

Before

calcination 80 0.2044 78 0.6052

After

calcination 178 -------- 165 ------

source are shown in Figure 5. Both the DSC profiles

exhibited two apparent endothermic events during the

thermal decomposition. The first event is at 200˚C for

Ksd3P10 and at 198˚C for Kliq3P10, the second thermal

event is at 410˚C for Ksd3P10 and at 361˚C for Kliq3P10.

In the first decomposition stage, the crystal water re-

leased. And in the second decomposition stage, the hy-

droxyl (OH–) octahedral structure is destroyed; the hy-

droxyl (OH–) and gas of H2O and CO anion release,

and CO2, MgO and Al2O3 are formed. The second ther-

mal event for Ksd3P10 (410˚C) which more larger than

for Kliq3P10 (361˚C) indicated that the sample prepared

by kaolinite clay in natural solid state possessed high

thermal stability, this observation can be explained by the

presence of SO2 in the sample.



3.2.5. Memory Effect of Calcined Kliq3P10 and

Ksd3P10 Hydrotalcite

The most important characteristic of layered double hy-

droxides is their ability to reconstruct themselves to their

original structure. It has already been reported that

Mg-Al hydrotalcites can be reconstructed when the sam-

ples are calcined below the temperature at which spinel

formation does not take place. Figures 6 and 7 show the

XRD pattern of samples calcined at 500˚C. From the

pattern it was observed that the layered structure was

Figure 5. DSC curves of: (a) Ksd3P10-LDH; (b) Kliq3P10-

LDH.

Figure 6. Powder XRD patterns of Ksd3P10-LDH (a) cal-

cined in air at 500˚C; (b) calcined at 500˚C and treated in

water for 2 days for reconstruction.

completely destroyed, which is clearly indicated by the

disappearance of the (003) and (006) peaks at lower 2θ

values in the original material (Figures 1(c) and 1(d)).

For Ksd3P10-LDH, the Figure 6(a) shows the pres-

ence of a peak at 4.5Å due argillaceous phase, which is

present as an impure phase, along with peaks due to

MgO. To find out whether the hydrotalcite synthesized

from the natural clay could be reconstructed to its origi-

nal structure, the Ksd3P10-LDH and Kliq3P10-LDH sam-

ples, which were previously calcined at 500˚C, was put

in water for 2 days. As shown in Figure 6(b) and Figure

7(b), the materials were completely reconstructed to its

Using Kaolinitic Clay for Preparation of a Hydrotalcite-Like Compound689

Figure 7. Powder XRD patterns of Kliq3P10-LDH (a) cal-

cined in air at 500˚C; (b) calcined at 500˚C and treated in

water for 2 days for reconstruction.

original layered structure, as indicated by the appearance

of the (003) and (006) peaks.

3.3. The Optimisation of the Operating

Conditions of Synthesis

3.3.1. The Effect of Mg2+/Al3+ Molar Ra tio

The XRD patterns of samples prepared by method 1 at

different Mg2+/Al3+ molar ratio show that no hydrotalcite

structure was formed when R < 3. From Figure 8,

well-crystalline LDH was obtained for Mg2+/Al3+ = 3.0.

From Figure 9, it was determined that as the Mg2+/

Al3+ molar ratio increases, from 0.5 to 4, the intensity of

003 and 006 reflections increases, are corresponding to

an increase of the formation of the LDH structure.

Well-crystalline LDH was obtained for Mg2+/Al3+ =1.0

(Figure 9) belong R = 1, the intensity of 003 and 006

reflections decreases corresponding to the decreasing in

cristallinity.

3.3.2. The Effect of of pH of Synthesis

The pH of preparation is important in the formation of all

hydrotalcite-type materials and the optimum pH depends

on the cations used. From Figure 10, it was determined

that samples prepared by method 1 and at pH = 8 dis-

played very weak, broad reflections at 2θ value of 11˚

compared to Ksd3P10-LDH and Ksd3P12-LDH prepared

at pH = 10 and 12 respectively (Figure 10). The XRD

patterns of Ksd3P8 (pH = 8) show that no hydrotalcite

structure was formed under these synthesis conditions.

The broadness of the reflections indicates that the sample

was poorly crystalline; brucite was formed instead of hy-

drotalcite. Samples prepared within the pH range of 10 -

12 show patterns similar to that of hydrotalcite. The dif-

ference between these samples is in the intensity of the

Figure.8. X-ray patterns of clay sample synthesized by

method 1 at different Mg2+/Al3+ molar ratio.

Figure 9. X-ray patterns of clay sample synthesized by

method 2 at different R (R = Mg2+/Al3+ molar ratio).

Figure 10. X-ray patterns of clay sample synthesized by

method 1 at different pH.

Using Kaolinitic Clay for Preparation of a Hydrotalcite-Like Compound

690

Figure 11. X-ray patterns of clay sample synthesized by

method 2 at different pH.

(00l) reflections. Ksd3P10 have the most intense and

sharpest reflections, and thus are the most crystalline

samples.

Samples prepared by method 2 and at pH = 9 dis-

played very weak, broad reflections at 2θ value of 11˚

The broadness of the reflections indicates that the sample

was poorly crystalline. Samples prepared within the pH

range of 10 - 12 show patterns similar to that of hydro-

talcite. The difference between these samples is in the

intensity of the (00l) reflections. The Kliq3P10 has the

most intense and sharpest reflections. Kliq3P12 (pH = 12)

shows a structure different from the previous samples; it

was contaminated with Al(OH)2.

4. Conclusions

Pure and well-crystalline phases of Mg-Al-CO3 LDH can

be prepared by coprecipitation and by mechano-chemical

synthesis method from the cationic clay (the kaolinite)

using an aqueous solution of Na2CO3 as a precipitant.

The pH of preparation was an important factor. At

pH = 10 well-crystalline LDH was formed. Below this

value, the crystallinity of the LDH decreased. Strong

alkaline conditions seem no favourable for the synthesis.

The optimum values of Mg2+/Al3+ molar ratio depend of

the method of synthesize. It was about 3 for synthesize

by the method 1 and about 1 for the method 2. Below

these ratios poorly crystalline products were obtained.

REFERENCES

[1] H. F. W. Taylor, “Crystal Structures of Some Double

Hydroxide Minerals,” Mineralogical Magazine, Vol. 39,

1973, pp. 377- 389. doi:10.1180/minmag.1973.039.304.01

[2] S. Miyata, “The Syntheses of Hydrotalcite-Like Com-

pounds and Their Structures and Physico-Chemical Prop-

erties I: The Systems Mg2+-Al3+-3

NO , Mg2+-Al3+-Cl−,

Mg2+-Al3+-4

ClO



, Ni2+-Al3+-Cl− and Zn2+-Al3+-Cl−,”.

Clays Clay Miner, Vol. 23, 1975, pp. 369-375.

doi:10.1346/CCMN.1975.0230508

[3] M. Bellotto, B. Rebours, O. Clause, J. Lynch, D. Bazin

and E. Elkaim, “Hydrotalcite Decomposition Mechanism:

A Clue to the Structure and Reactivity of Spinel-Like

Mixed Oxides,” The Journal of Physical Chemistry, Vol.

100, No. 20, 1996, pp. 8535-8542. doi:10.1021/jp960040i

[4] F. Cavani, F. Trifiro and A. Vaccari, “Hydrotalcite-Type

Anionic Clays: Preparation, Properties and Applications,”

Catalysis Today, Vol. 11, No. 2, 1991, pp. 173-301.

doi:10.1016/0920-5861(91)80068-K

[5] A. De Roy and J. P. Besse, “Conductivité Ionique de

Composés de Type Hydrotalcite,” Solid State Ionics, Vol.

35, No. 1-2, 1989, pp. 35-43.

doi:10.1016/0167-2738(89)90009-X

[6] J. E. Moneyron, A. De Roy and J. P. Besse, “Realization

of a Humidity Sensor,” Sensors and Actuators B: Chemi-

cal, Vol. 4, No. 1-2, 1991, pp. 189-194.

doi:10.1016/0925-4005(91)80197-R

[7] G. Carja and G. Delahay, “Mesoporous Mixed Oxides

Derived from Pillared Oxovanadates Layered Double hy-

Droxides as New Catalysts for the Selective Catalytic

Reduction of NO by NH3,” Applied Catalysis B: Envi-

ronmental, Vol. 47, No. 1, 2004, pp. 59-66.

doi:10.1016/j.apcatb.2003.07.004

[8] H. Schaper, J. J. Berg-Slot and W. H. J. Stork, “Stabilized

Magnesia: A Novel Catalyst (Support) Material,” Applied

Catalysis, Vol. 54, No. 1, 1989, pp. 79-90.

doi:10.1016/S0166-9834(00)82356-8

[9] P. C. Pavan, G. D. Gomes and J. B. Valim, “Adsorption

of Sodium Dodecyl Sulfate on Layered Double Hydrox-

ides,” Microporous and Mesoporous Materials, Vol. 21,

No. 4-6, 1998, pp. 659-665.

doi:10.1016/S1387-1811(98)00054-7

[10] P. C. Pavan, E. L. Crepaldi, G. D. Gomes and J. B. Valim,

“Adsorption of Sodium Dodecylsulfate on a Hydro-

tal-Cite-Like Compound. Effect of Temperature, pH and

Ionic Strength,” Colloids and Surfaces A, Vol. 154, No. 3,

1999, pp. 399-410. doi:10.1016/S0927-7757(98)00847-4

[11] M. Meyn, K. Beneke and G. Lagaly, “Anion-Exchange

Reactions of Layered Double Hydroxides,” Inorganic

Chemistry, Vol. 29, No. 26, 1990, pp. 5201-5207.

doi:10.1021/ic00351a013

[12] J. H. Choy, S. Y. Kwak, J. S. Park, Y. J. Jeong and J.

Portier, “Intercalative Nanohybrids of Nucleoside Mono-

phos-Phates and DNA in Layered Metal Hydroxide,”

Journal of the American Chemical Society, Vol. 121, No.

6, 1999, pp. 1399-1400. doi:10.1021/ja981823f

[13] J. H. Choy, J. S. Jung, J. M. Oh, M. Park, J. Jeong, Y. K.

Kang and O. J. Han, “Layered Double Hydroxide as an

Efficient Drug Reservoir for Folate Derivatives,” Bio-

materals, Vol. 25, No. 15, 2004, pp. 3059-3064.

doi:10.1016/j.biomaterials.2003.09.083

[14] M. Valcheva-Traykova, V. Davidova and A. Weiss,

“Thermal Decomposition of Mg, Al-Hydrotalcite Mate-

Using Kaolinitic Clay for Preparation of a Hydrotalcite-Like Compound

691

rial,” Journal of Materials Science, Vol. 28, 1983, pp.

2157-2162. doi:10.1007/BF00367577

[15] M. Del Acro, P. Del Malet, R. Trujillano and R. Rives,.

“Synthesis and Characterization of Hydrotalcites Con-

taining Ni(II) and Fe(III) and Their Calcination Prod-

ucts,” Journal of Chemistry of. Materials, Vol. 11, No. 3,

1999, pp. 624-633. doi:10.1021/cm9804923

[16] X. Hou and J. R. Kirkpatrick, “Thermal Evolution of the

Cl-LiAl2 Layered Double Hydroxide: A Multinuclear

MAS NMR and XRD Perspective,” Inorganic Chemistry,

Vol. 40, No. 25, 2001, pp. 6397-6404.

doi:10.1021/ic010671d

[17] P. Beaudot, M. E. De Roy and J.-P. Besse, “Intercalation

of Platinum Complex in LDH Compounds,” Journal of

Solid State Chemistry, Vol. 161, No. 2, 2001, pp. 332-340.

doi:10.1006/jssc.2001.9322

[18] Y. Seida and Y. Nakano, “Removal of Phosphate by Lay-

ered Double Hydroxide Containing Iron,” Water Re-

search, Vol. 36, No. 5, 2002, pp. 1306-1312.

doi:10.1016/S0043-1354(01)00340-2

[19] G. Brindley and G. Brown, “Crystal Structures of Clay

Minerals and their X-Ray Identification,” Mineralogical

Society, London, 1984

[20] A. De Roy, C. Forano, K. El Malki and J.-P. Besse,

“Anionic Clays: Trends in Pillaring Chemistry,” In: M. L.

Occelli and H. E. Robson, Eds., Synthesis of Microporous

Materials, Van Nostrand Reinhold, New York, 1992, pp.

108-169.

[21] J. Das, D. Das and K.M., Parida, “Preparation and Char-

acterization of Mg-Al Hydrotalcite-Like Compounds

Containing Cerium,” Journal of Colloid and Interface

Science, Vol. 301, No. 2, 2006, pp. 569-574.

doi:10.1016/j.jcis.2006.05.014

[22] G. Allegra and G. Ronca, “Crystal Powder Statistics. II.

Line Profiles in Diffraction Spectra of Identical Crystals

and of Gaussian Samples. Crystal Size Distributions,”

Acta Crystallographica Section A, Vol. 34, part 6, 1978,

pp. 1006-1013.

[23] E. Alvarez-Ayuso and H. W. “Nugteren. Purification of

Chromium (VI) Finishing Wastewaters Using Calcined

and Uncalcined Mg-Al-CO3-Hydrotalcite,” Journal of

Water Research, Vol. 39, No. 12, 2005, pp. 2535-2542.

doi:10.1016/j.watres.2005.04.069

[24] J. T. Kloprogge, D. Wharton, L. Hickey and R. L. Frost,

“Infrared and Raman Study of Interlayer Anions 2



, 2



and 4

ClO



in Mg/Al-Hydrotalcite,” Jour-

nal of American Mineralogist, Vol. 87, 2002, pp. 623-

629.

[25] S. J. Gregg and K. S. W. Sing, “Adsorption, Surface Area

and Porosity,” 2nd Edition, Academic Press, London,

1982.