Surface and Interface Chemistry of Clay Minerals

Robert Schoonheydt, Cliff T. Johnston, Faïza Bergaya

• Publisher: Elsevier
• Year: 2018
• Print ISBN: 9780081024324
• eBook ISBN: 9780081024331
• Topic: Physical Sciences
• Subtopic: Geology & Earth Sciences

Surface and Interface Chemistry of Clay Minerals, Volume 9, delivers a fundamental understanding of the surface and interface chemistry of clay minerals, thus serving as a valuable resource for researchers active in the fields of materials chemistry and sustainable chemistry. Clay minerals, with surfaces ranging from hydrophilic, to hydrophobic, are widely studied and used as adsorbents. Adsorption can occur at the edges and surfaces of clay mineral layers and particles, and in the interlayer region. This diversity in properties and the possibility to tune the surface properties of clay minerals to match the properties of adsorbed molecules is the basis for study. This book requires a fundamental understanding of the surface and interface chemistry of clay minerals, and of the interaction between adsorbate and adsorbent. It is an essential resource for clay scientists, geologists, chemists, physicists, material scientists, researchers, and students.- Presents scientists and engineers with a resource they can rely on for their own research and work involving clay minerals- Includes an in-depth look at ion exchange, adsorption of inorganic and organic molecules, including polymers and proteins, and catalysis occurring at the surfaces of clay minerals- Includes materials chemistry of clay minerals with chiral clay minerals, optical materials and functional films

1

Clay minerals and their surfaces

Robert A. Schoonheydt*; Cliff T. Johnston^†; Faïza Bergaya^{‡ *} Centre for Surface Chemistry and Catalysis, Catholic University of Leuven, Leuven, Belgium
^† Departments of Earth, Atmospheric, and Planetary Sciences and Agronomy, Purdue University, West Lafayette, IN, United States
^‡ Interfaces, Confinement, Matériaux et Nanostructures (ICMN), Centre National de la Recherche Scientifique (CNRS), Orléans, France

Abstract

Clay minerals are introduced with their main structural features and unit cell formulae. Isomorphous substitution creates a negative lattice charge, leading to cation exchange, swelling, and intercalation. Edge surfaces and interlayer space are defined together with the surface atoms: O, OH, and exchangeable cations. They are of primary importance to understand the interaction of adsorbed molecules and ions with the surface of clay minerals and for surface–surface interactions. The forces involved in all these interactions are always attractive and induce the organization of the system, which is counteracted by the thermal energy.

Keywords

TO and TOT clay minerals; Isomorphous substitution; Cation exchange; Swelling; Intercalation; van der Waals energy; H-bonding; Lennard-Jones potential

1.1 TO or 1:1 and TOT or 2:1 clay minerals

Clay minerals belong to the phyllosilicate family (Bailey, 1988b; Brigatti et al., 2013). Each layer of these layered silicates consists of T sheets of corner-sharing Si tetrahedra, [SiO₄], and O sheets of edge-sharing Al octahedra, [Al(OH)₂O₄]. The T and O sheets are connected with a common oxygen atom (Fig. 1.1).

Fig. 1.1 Association of T and O sheets (example: schematic structure of kaolinite). Red balls (dark grey in the print version) are oxygen; purple balls (grey in the print version) are aluminium, and grey balls are hydrogen atoms.

The possible combinations of T and O sheets among both TO and TOT layers lead to a classification of nine distinguished main groups of clay minerals reported in Table 1.1. The 2D connectivity of the planar layer at the molecular level should be distinguished from the morphology at an upper level of organization (Ras et al., 2007).

Table 1.1

The nine main groups of clay minerals

Group of clay minerals	T and O associations with more typical examples of clay minerals
Kaolinite and serpentine	TO Kaolinite (laths) and halloysite (nanotubes)
Pyrophyllite and Talc	TOT
Smectites	TOT
Vermiculites	TOT
Micas	TOT
Chlorites	TOT
Interstratified clay minerals	Regular or irregular combinations of TO and TOT and/or of different TOT
Sepiolites and palygorskites	TOT with a discontinuous O sheet Fibrous morphology
Allophanes and imogolites	TO of short range order Poorly crystalline clay minerals (X-ray amorphous)

The structure of TO (or 1:1) clay minerals layers, as shown in Fig. 1.1, is representative of the kaolinite structure. The chemical structural formula of the unit cell is [Si₂Al₂O₅(OH)₄] with two typ...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Dedication
• Contributors
• Preface
• Acknowledgements
• 1: Clay minerals and their surfaces
• 2: Determination of surface areas and textural properties of clay minerals
• 3: Quantum-chemical modelling of clay mineral surfaces and clay mineral–surface–adsorbate interactions
• 4: Clay mineral–water interactions
• 5: Adsorption of heavy metals including radionuclides
• 6: From transition metal ion complexes to chiral clay minerals
• 7: Organic pollutant adsorption on clay minerals
• 8: Protein adsorption on clay minerals
• 9: Clay mineral catalysts
• 10: From polymers to clay polymer nanocomposites
• 11: From adsorbed dyes to optical materials
• 12: Preparation and application of clay mineral films
• Index