Clay Surfaces: Fundamentals and Applications

558 Pages·2004·16.999 MB·1-553\558

by  Fernando Wypych and Kestur Gundappa Satyanarayana (Eds.)

Preface
The purpose of this book is to introduce the reader to the fascinating world of
the chemistry and physics of the clay mineral surfaces/interfaces and to demonstrate
that, in spite of lot of information that has been accumulated over the decades, a vast
field still exists to be explored. This book will not only be useful for the specialists
directly involved with clay science and related areas but also as a text or supplementary
reading for undergraduate and graduate students.
When a crystalline or amorphous solid is brought in contact with a liquid, a gas
or another solid, the possible reactions and interactions take place via their surfaces. The
study of the chemistry and physics of the surfaces plays a fundamental role in an
attempt to understand those phenomena in a general sense. Apart from the structure, the
composition is usually very different from the bulk of the crystal, mainly due to the
sorption of ions and/or neutral molecules on the surface of the crystal.
Another fundamental point in the reactivity of materials is related to the defects
on the crystals' surface and surface reconstruction, the first originating in the
preparation procedure and the second in a mechanism of compensation of the
unsaturated bonds when a surface is generated by growth or fracture. All these
phenomena are of fundamental importance for several branches of science. However,
many of them remain slightly misunderstood, mainly based on the fact that only in the
last few decades has appropriate equipment been developed and/or improved for this
kind of studies. Usually, the information generated by the atoms of the surface is
infinitely weaker than that by the atoms of the bulk, which makes it difficult or hinders
the studies of the interfaces of the crystals. Considering the clay minerals and the
possible interactions with multi components of the soil (that can be obtained by the
degradation of organic matter of vegetable or animal origin, deliberately introduced
through agricultural activities or via the decomposition cycle of rocks and minerals,
apart from the activity of microorganisms), it is easy to imagine the extreme complexity
of the phenomena on the surfaces involved in those systems. In this book, we have
made an attempt to describe the clay surface/interfaces phenomena with the main
purpose to try to understand the interrelations among the minerals, living organisms and
human activities on our planet. The above aspects of clays are presented in this volume.
This book contains 71 chapters, which have been classified under two main
headings, viz., Natural clays: theoretical aspects and applications and Synthetic clays:
Synthesis and applications with an introductory chapter by Prof. Femando Wypych.
This chapter defines layered materials and deals with derivatives of simple hydroxides,
hydroxysalts, synthetic clays (Layered Double Hydroxide (LDH)) and natural clays.
Herein various reactions such as adsorption, solvation, grafting, exfoliation, thermal,
mechanochemical modifications and intercalation have been explained in respect of the
mentioned derivatives.
The Section under Natural clays: theoretical aspects and applications includes
10 chapters. Chapters 2-5 deal with the theoretical aspects of clay surfaces. Knowing
that the electrokinetic properties of a substance are used to explain the mechanism of
dispersion and agglomeration in a liquid phase and identification of the adsorption
mechanisms of ions or molecules at a solid-liquid interface, the second chapter presents
an overview of the electrokinetic properties of clay minerals, elucidating the
electrokinetic behavior of clay surfaces and the mechanism of particle-particle
interactions in aqueous systems. On the other hand, considering various forces that
operate at the interface where the two surfaces interact and the importance of such
vi ecaferP
studies on colloidal materials such as clays, the third chapter presents the recent
thermodynamic study of clay surfaces, both swelling and non-swelling type, and relates
it to the data obtained by measurements of surface tension, immersion enthalpy and
sorption.
The properties of any material near surfaces or interfaces are different to the
properties of the same material in the bulk because of the different coordination
environment of surface atoms than that of those in the bulk. This special character of
surfaces has some thermodynamic implications, especially in terms of interaction with
molecules of other substances in close contact. This aspect is described in the fourth
chapter. Taking into account the vital role played by the adsorption/desorption processes
in determining the efficacy and environmental behavior of pollutants or nutrients in soil,
and most of the adsorption in natural systems occurs in the dispersed phase that consists
predominantly of inorganic colloids such as clays, the fifth chapter presents a model for
these processes and also other mechanisms and reactions for predicting the behavior of
reactive solutes in complex systems in both single and multi-component systems with
several interacting species. Characterization of clay surfaces, including modification of
kaolinite surfaces, intercalation by mechanochemical method as studied by Raman and
IR spectroscopic techniques are described in Chapter 6. It is well known that NMR
studies provide structural and dynamic information at a local and sometimes
mesoscopic scale. Hence a brief outline of the relevant NMR theory, starting with the
solid state and simplification brought about by the mobility increase in the liquid state
and studies of natural, synthetic, or modified clay suspensions along with some NMR
results on solid systems are summarized in Chapter .7
Some of the important applications of clays include ceramics, paper, paint,
plastics, drilling fluids, foundry bondants, chemical carriers, liquid barriers,
decolorization, and catalysis. Further, pesticides, toxic organic chemicals, greenhouse
gases, heavy metals, undesirable inorganic substances are as much targeted molecules to
be controlled for the preservation of flora and fauna and safety of the earth.
Accordingly, Chapters 8-10 deal with various application areas of natural clays
mentioned, including removal of a wide range of contaminants from industrial effluents
or wastewater by anion exchange and adsorption processes or catalytic remediation,
using LDHs, modified LDHs or calcined LDHs, pharmaceutical & cosmetics,
environmental remediation, waste treatment including nuclear wastes, heavy and toxic
metals removal, biological applications, etc. Removal of metals, particularly of
chromium in wastewater, by natural and modified clays is described in Chapter .01 The
catalytic and adsorption properties of modified clays is given in Chapter 11 covering
some general aspects of structure of clays, cation exchange capacity and swelling
capacity of clays, clay-organic cation- interaction and acid-activated organo clays with a
view to understand better the relationship between the clays and their catalytic uses.
The section on Synthetic clays: Synthesis and applications has six chapters.
Over the last two decades, interest has been growing in the availability for the
intercalation of various organic anions having flexible or rigid molecular frameworks
into LDH, not only from the scientific but also from industrial viewpoints. This includes
synthetic anionic clay materials. Accordingly, the state of the art for the materials
composed of the assembly between Layered Double Hydroxides (LDH) and Polymer
are described in these chapters and new trends in term of applications are identified. It is
pointed out here that the polymer/LDH assembly, not yet extensively studied,
constitutes an appealing new class of nanocomposites in numerous topical applications.
Chapter 21 is related to the synthetic methods of layered double hydroxides
and mechanism of decomposition studied by in-situ techniques. Chapter 31 concentrates
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on the newest research progress in the compositions, structures, synthesis methods and
photocatalytic and oxidation-catalytic functions of the POM-LDHs complexes. The
preparation and applications of a new emerging class of bio-clay hybrids are presented
and discussed in Chapter .41
A wide range of contaminants can be removed from industrial effluents or
wastewater by anion exchange and adsorption processes or catalytic remediation, using
LDHs, modified LDHs or calcined LDHs. With this background, Chapter 51 describes
the investigations on the potential uses of LDHs for decontamination of environmental
sites or prevention of pollutant dispersion in Nature.
Chapter ,61 dealing with Layered Double Hydroxide/Polymer nanocomposites,
gives a description of LDH materials including their natural occurrence, chemical
composition and aspects of the stacking sequence, the building of inorganic-organic
assemblies including synthetic pathways for the LDH/polymer assembly along with the
layer charge density and the colloidal and exfoliation properties.
Chapter 71 describes a broad spectrum of catalytic applications of layered
double hydroxides and possibilities of designing catalysts tailored for specific reactions
and/or substrates.
With the accumulation of the above knowledge, we expect to understand in the
future the mechanisms of the interactions of the soils when in contact with the wastes
originated from human activities. We also hope to understand what action should be
taken in the case of an accidental spilling of chemicals, how to improve the production
of food without affecting the ecological balance significantly, how to increase the
fixation of carbon in the soil to increase the production of cereal grains and reduce
carbon dioxide emissions to the atmosphere, and safely predict the effects of a certain
activity on the soil, waters and atmosphere of our fragile planet. We hope this book will
be good reading material for all concerned with all aspects of mother Earth.
It is not an exaggeration to say that this volume represents the expertise, time,
efforts and opinions of 27 specialists in their subject areas. The statements, views and
recommendations made by each of the contributors are their own and should be
considered to be made with appropriate responsibility. The editors express their sincere
and heartfelt gratitude to all these contributors for their devotion and providing the
chapters, for carrying out alterations/modifications as and when called for to suit the
overall uniformity of this volume. They also express their gratitude to Louise Morris
and Derek Coleman of Elsevier for their guidance and help from time to time and last
but not the least, to Dr. Arthur Hubbard for the invitation, encouragement and the first
table of contents of the book.
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Contributors
ALBERTO LOPEZ-GALINDO ,1 and CI~SAR VISERAS 2
11nstituto Andaluz de Ciencias de la Tierra (CSIC-UGR). Facultad de Ciencias, Campus
Fuentenueva. 18071 - Granada - SPAIN.
2 Departamento de Farmacia y Tecnologia Farmac6utica, Facultad de Farmacia.
Universidad de Granada. 18071, Granada- SPAIN. E-mail: [email protected]
* E-mail: [email protected]
ALEXANDER MORONTA
Centro de Superficies y Catdlisis, Facultad de Ingenieria, Universidad del Zulia,
Maracaibo 4003-A - VENEZUELA.
E-mail: [email protected]
B.S. JAI PRAKASH
Department of Chemistry, Bangalore Institute of Technology, k.r. road, Bangalore 560
004, INDIA.
E-mail: [email protected]
CHANGWEN HU 1. and DANFENG LI 2
l Department of Chemistry, Beijing Institute of Technology, Beijing, P.R. CHINA,
180001
2 Institute of Polyoxometalate Chemistry, Northeast Normal University, Changchun,
P.R. CHINA, 130024
* E-mail: [email protected]
CLAUDE FORANO
Laboratoire des Mat6riaux Inorganiques, UMRCNRS 6002, Universit6 Blaise Pascal,
63177, Aubi~re C6dex - FRANCE
E-mail: [email protected], fr
CRISTINA VOLZONE
Centro de Tecnologia de Recursos Minerales y Cer~imica - CETMIC
(CIC-CONICET-UNLP)- CC 49, Cno. Centenario y 506, (1897) M.B. Gonnet
Provincia de Buenos Aires- ARGENTINA
E-mail: [email protected] / [email protected]
ElM KANEZAKI
Department of Chemical Science and Technology, Faculty of Engineering, The
University of Tokushima, 1-2 Minamijosanjima, Tokushima 770-8506 - JAPAN
E-mail: [email protected]
FABRICE LEROUX * and JEAN-PIERRE BESSE
Laboratoire des Mat6riaux Inorganiques, UMR 6002-CNRS, Universit6 Blaise Pascal,
24 av. des Landais, 63177 Aubi~,re c6dex, FRANCE.
(cid:12)9 E-mail: [email protected]
FERNANDO WYPYCH
Centro de Pesquisas em Quimica Aplicada - CEPESQ.
Universidade Federal do Parami- UFPR- Departamento de Quimica
cP 19081 -Centro Polit6cnico- 81531-990 -Curitiba- PR- BRAZIL.
E-mail: [email protected]
Contributors ix
GIORA RYTWO
School of Environmental Sciences and Technology - Tel Hai Academic College, Upper
Galilee 12210, ISRAEL.
MIGAL, Galilee Technological Center, Kiryat Shmona, ISRAEL.
E-mail: [email protected]
JEAN GRANDJEAN
Universit6 de Liege - Institut de Chimie B6a- COSM Sart Tilman- B-4000 Liege -
BELGIUM
E-mail.: J.Grandj [email protected]
JEAN MARC DOUILLARD* and FABRICE SALLES
University of Sciences, L.A.M.M.I., CC015, Universit6 Montpellier 2. Sciences et
Techniques du Languedoc. .1P Eugene Bataillon, Montpellier Cedex 05 - FRANCE
* E-mail : [email protected]
JIN-HO CHOY* and MAN PARK
National Nanohybrid Materials Laboratory (NNML) -School of Chemistry and
Molecular Engineering- Seoul National University, Seoul, 151-747 - KOREA
* E-mail: [email protected]
JUAN CORNEJO*, RAFAEL CELLS, LUCIA COX and M. CARMEN
HERMOSiN
Instituto de Recursos Naturales y Agrobiologia de Sevilla, CSIC. P.O. Box 1052.41080
Sevilla- SPAIN.
* E-mail: [email protected]
MEHMET SABRI (~ELIK
Istanbul Technical University - Mining Engineering Dept., Mineral Processing
Section
Ayazaga 34469 Istanbul - TURKEY
E-mail: [email protected]
RAY L. FROST .1 and JANOS KRISTOF 2
Inorganic Materials Research Program, Queensland University of Technology, GPO
Box 2434, Brisbane Queensland 4001 - AUSTRALIA.
2 Department of Analytical Chemistry, University of Veszprem, H8201 Veszprem, PO
Box 158 - HUNGARY.
* E-mail: [email protected]
SIMONE ALBERTAZZI, FRANCESCO BASILE and ANGELO VACCARI*
Dipartimento di Chimica Industriale e dei Materiali, Alma Mater Studiorum - Universit~
di Bologna, INSTM-UdR di Bologna, Viale del Risorgimento 4, 40136 Bologna -
ITALY.
* E-mail: [email protected]
CHEMICAL MODIFICATION OF CLAY SURFACES
FERNANDO WYPYCH
Centro de Pesquisas em Quimica Aplicada- CEPESQ.
Universidade Federal do Parami- UFPR- Departamento de Quimica
CP 19081 - Centro Polit6cnico - 81531-990 - Curitiba - PR - BRAZIL.
E-maih [email protected]
Clay Surfaces: Fundamentals and Applications
.F Wypych and K. .G Satyanarayana (editors)
(cid:14)9 2004 Elsevier Ltd. All rights reserved.
2 .F Wypych
1 - Introduction
Layered materials belong to a special class of compounds in which the crystals
are built by the stacking of "two-dimensional" units known as layers that are bond to
each other through weak forces 1,2]. [
Intercalation reactions occur by the topotactic insertion of mobile guest species
(neutral molecules, anhydrous or solvated ions) into the accessible crystallographic
defined vacant sites located between the layers (interlayer spacings) in the layered host
structure. In this intercalation compounds, strong covalent bonds occur in the layers and
weak interactions, between host lattice and guest species or co-intercalated solvents.
Ionic and solvent exchange reactions are related to the replacement of solvated guest
species (cations and anions) located into the interlayer spacings. In this case, only the
solvent, the cations or the solvated cation can be replaced, depending on the reaction
conditions.
Grafting reactions occur by establishing covalent bonds between the reactive
groups of the layer and an adequate reactant molecule, which ensures higher chemical,
structural and thermal stability for the compound. These reactions can be restricted to
the crystal surface (the basal spacing remains unchanged) or layer surface (in this case
an interlayer expansion occurs). These compounds can be collectively defined as hybrid
materials, or more specifically, surface-modified inorganic layered materials.
One of the simplest families in the compounds with layered structures belongs
to the alkaline earth or transition metal hydroxides. Common examples involve the
structure of brucite (Mg(OH)2) [3,4], gibbsite, bayerite, nordstrandite and doyleite
(polymorphic modifications of AI(OH)3), among others.
Brucite has the most representative structure that is adopted by several simple
hydroxides. In brucite structure [3], atoms of magnesium are octahedrically bonded to
six hydroxyl groups, being these units linked to each other through the edges, producing
charge neutral two-dimensional layers. Both sides of the layers are covered in hydroxyl
groups, being potentially susceptible to be grafted by adequate organic/inorganic
molecules, producing grafted or pillared derivatives. Brucite layers are the fundamental
building units of a great variety of geologically important hydrous phyllosilicates,
including micas, clays and layered double hydroxides (LDH). Figure l(a) displays the
structure of brucite, Figure l(b), the schematic representation of a single layer and
Figure 1 (c), the layer top view
Figure 1 - (a) Structure of brucite, (b) the schematic representation of a single layer
and (c), the layer top view [5].
Modification Chemical of Surfaces Clay 3
Another class of compounds with a little more complex structures, is the
layered hydroxysalts, being typical structures of hydrozincite (Zns(OH)6(CO3)2) [6],
zinc hydroxide nitrate (Zns(OH)s(NO3)2.2H20) ]7[ or copper (II) hydroxide acetate
(Cu2(OH)3CH3COOH.H20) [8]. In these compounds, part of the hydroxyl anions is
exchanged by other anions. Water molecules may also be incorporated in the interlayer
region for stability. The typical formulation can be written as: M (OH)x_yB y/n.zH20 X+ n-
(M +x = metal cation and B =-n anion). Normally, the substituting ion neither needs to
have similar hydroxyl ion chemical characteristics nor the same size. In this case, an
interlayer expansion is expected in order to accommodate the solvated ion.
In hydroxysalts, the process of grafting of specific molecules to the
hydroxylated side of the layer (as in the case of the simple hydroxides) and processes of
anionic exchange, are also possible. The synthesis of the copper(II) hydroxide acetate is
presented in [Eq. 1 .]
2 Cu 2+ + 3 OH + CH3COOH"--~ Cu2(OH)3CH3COO.H20 (Eq. )1
Controlling the conditions, copper(II) hydroxide or copper(II) hydroxide
acetate can be precipitated. Figure 2(a) presents the structure of the zinc hydroxide
nitrate, Figure 2(b), the layer top view and Figure 1 (c), the schematic representation of a
single layer.
Figure 2 - (a) Structure of the zinc hydroxide nitrate, (b) the layer top view and (c), the
schematic representation of a single layer [5,8].
Other most typical examples of minerals belonging to clay minerals class are
hydrotalcite (Mg6A12(OH)16CO3.4H20) ]9[ and pyroaurite (Mg6Fe2(OH)16CO3.4.5H20)
[10], which have the layered double hydroxides (LDH) structure, also known as anionic
clays [11-14]. In these materials of variable compositions and mainly of synthetic
origin, the layered structure is intimately related to the structure of brucite, where
hydroxyl ions are hexagonally close packed and magnesium (or aluminum) ions occupy
octahedral sites. Both sides of the layer are covered in hydroxyl groups.
LDHs have a generic formulation 02Hn.m/x)'mA(+X]E)HO(x3+Mx.lE+M[ , where
M 3+ and M 2+ represent metal ions in octahedral sites and A -m represents the interlayer
4 .F hcypyW
anion. In these compounds, the trivalent metal substitutes isomorphically a metal in the
divalent state of oxidation of the hydroxide structure, generating charges that are
compensated by the intercalation of hydrated anions (Eq. .)2 LDHs can also be prepared
with a single metal in two different oxidation states (Ex.: mA(+X]2)HO(x3+eFx_12+eF[
)02Hn.mJx) producing the "green rusts".
0,67Mg 2+ + 0,33A1 3+ + 2OH + 3OC 2" ssecxe 02H~ n.561.0)3OC(2)HO(33.01A76.0gM
(Eq. 2)
When another interlayer ion is needed instead of carbonate, the reactions
should be performed under protective gas and using boiled and degassed solutions. In
the case of using alkaline metal hydroxides as precipitation agent, the excess carbonate
should be removed. The salts should preferably contain the anions to be intercalated or
an excess of the anion should also be added to the reaction media to compensate the
undesirable species (Eq. 2).
These hydrated anions are free to move, as they are located in the interlayer
spacings. They are exchangeable, being attributed to these compounds the characteristic
anionic exchange capacity (AEC). The anions class to be exchanged is wide, going from
organic [ 15], inorganic [ ]61 and even complexes 14,17], [ with varied oxidation states.
Figure 3(a) presents the structure of the layered double hydroxides and Figure 3(b), the
schematic representation of a single layer.
Figure 3 - )a( Structure of the layered double hydroxides and (b) the schematic
representation of a single layer [5].
Another class of similar compounds and of natural or synthetic origin involves
the clay minerals of the phyllosilicate group [18,19]. In these compounds, generically
two structural units are normally involved in the construction of their crystalline lattices.
The first is constituted of octahedrons of oxygen atoms and hydroxyl groups at the
comers with an aluminum atom in the center or of the gibbsite type. The other is
constituted of tetrahedrons with oxygen atoms at the comers and with a silicon atom in
the center or of the silica (tridymite) type. If we consider the connection of those
isolated units along the plane (octahedrons or tetrahedrons) we will have superposed
atomic planes that constitute a sheet. The superposition of the sheets build the layers,
the ones which were stacked and separated by the interlayer spacings constitute the
structural units [ 19]. Clay minerals are essentially hydrated crystalline aluminosilicates
lacimehC noitacifidoM of yalC secafruS 5
containing several main elements as iron, alkaline and alkaline earth metals. The
crystalline lattices are classified as three-dimensional, two-dimensional (layered) or
mono-dimensional (fibrous structures) [18,19]. The hydrated aluminosilicates can be
neutral or ionic exchangers and the groups treated in this work involve basically the
phyllosilicates of the smectite group (type 2:1 - derived from the idealized formula of
pyrophyllite (A12SiaO10(OH)2 dioctahedral = only 2/3 of the octahedral sites are
occupied) and kaolin group (type 1:1). More specifically montmorillonite (typical
formulation: 0104iS)33.0gM76.llA(+M33.0 (OH)2) and kaolinite (ideal formulation:
AlaSiEO5(OH)4). The composition of the montmorillonites is variable and depends on its
own genesis, which is attributed to the characteristic of different cationic exchange
capacity. However, in general, it is very superior to that of kaolinite. The low cationic
exchange capacity of kaolinite is justified by the low isomorphic structural substitution
(usually 1A § for Fe § or .)3+eF In other words, its composition can be considered fixed.
The nomenclature 2:1 and l:l refers to the construction of the layers: in the
case of the smectites, the layer is built by two sheets of silicon atoms tetrahedrically
bonded to oxygen atoms that involve a sheet of aluminum atoms octahedrically bonded
to oxygen atoms and hydroxyl groups. Both sides of the layer expose planes of oxygen
atoms (siloxane surface), having distorted hexagonal cavity formed by six-comer
sharing silica tetrahedron (Fig. 4(c)). The low interaction between the layers provides
the material easy cleavage and consequently, anisotropic properties. In nature,
aluminum atoms are isomorphically replaced by atoms of lower oxidation states, thus
producing negatively charged layers, in higher or lower degree. The negative layers are
charge balanced through the process of intercalation of hydrated cations in interlayer
vacant sites, which is being attributed to these clay minerals for their high cationic
exchange capacity characteristics (measured in meq/100g). Figure 4(a) presents the
structure of montmorillonite, Figure 4(b), the schematic representation of a single layer
and Figure 4(c), the silicate sheet top view.
Figure 4 - (a) Structure of the montmorillonite, (b) the schematic representation of a
single layer and (c), the silicate sheet top view [5].