F. Bergaya

CEC of clays: Measurement by adsorption of a copper ethylenediamine complex

Abstract A method for the rapid determination of CEC values in clays using au ethylenediamine complex of Cu was tested with different clays. The single-step procedure is fast and does not require sophisticated apparatus. The exchange with most cations—and even with those of heavy metals—is irreversible and can be carried out over a range of pH values. The results, which can be obtained using a wide variety of analytical techniques, are generally in good agreement with those given by the classical Kjeldahl method.

General Introduction: Clays, Clay Minerals, and Clay Science

Abstract Clays and clay minerals are recognized as the materials of the twenty-first century. Chapter 1 provides a general introduction into clay science, illustrates the classification of the clay minerals (planar and non-planar 1:1 and 2:1 clay minerals), shows the idealized formulae of some representative clay minerals, lists the current names of clays, and reports the important properties of clay minerals. As yet, there is no uniform nomenclature in clay science, a unifying terminology is proposed that should be acceptable to all disciplines, users, and producers. This mainly concerns the terms “clay and clay mineral“, “associated minerals and associated phases“, “particles and aggregates“, “swelling“, and “delamination and “exfoliation“. Finally, in addition to belonging to the class of silicates, three alternative concepts of clay minerals are proposed to extend the benefit to a wider scientific audience.

Chapter 1 General Introduction: Clays, Clay Minerals, and Clay Science

Publisher Summary This chapter attracts the attention of clay scientists in academe and industry as well as in politics (as research needs funding), and focuses on the importance of clay science to society and the quality of life. The economic benefits seem evident because clays are abundant, widespread, and inexpensive compared with other raw materials. The chapter discusses the industrial and environmental importance of clays and clay minerals. The great variety of physical, chemical, and thermal treatments that may be used to modify clays and clay minerals provide unlimited scope for future applications, particularly in terms of protecting the environment. Because of the multidisciplinary nature of clay science, its teaching is another challenging task. By learning about the mineralogical, physico-chemical, and industrial aspects of clay science, students would not only gain an appreciation of the “scientific method” and the physical environment but also find suitable employment and a fulfilling career.

REPORT OF THE ASSOCIATION INTERNATIONALE POUR L’ÉTUDE DES ARGILES (AIPEA) NOMENCLATURE COMMITTEE FOR 2001: ORDER, DISORDER AND CRYSTALLINITY IN PHYLLOSILICATES AND THE USE OF THE “CRYSTALLINITY INDEX”

The purpose of this report is to describe the appropriate use of indices relating to crystallinity, such as the ‘crystallinity index’, the ‘Hinckley index’, the ‘Kubler index’, and the ‘Arkai index’. A ‘crystalline’ solid is defined as a solid consisting of atoms, ions or molecules packed together in a periodic arrangement. A ‘crystallinity index’ is purported to be a measure of crystallinity, although there is uncertainty about what this means (see below). This report discusses briefly the nature of order, disorder and crystallinity in phyllo-silicates and discusses why the use of a ‘crystallinity index’ should be avoided. If possible, it is suggested that indices be referred to using the name of the author who originally described the parameter, e.g. ‘Hinckley index’ or ‘Kubler index’, or in honor of a researcher who investigated the importance of the parameter extensively, e.g. ‘Arkai index’. In contrast to a crystalline solid, an ‘amorphous’ solid is one in which the constituent components are arranged randomly. However, many variations occur between the two extremes of crystalline vs. amorphous. For example, one type of amorphous material might consist simply of atoms showing no order and no periodicity. Alternatively, another amorphous material may consist of atoms arranged, for example, as groups of tetrahedra ( i.e. limited order) with each group displaced or rotated ( e.g. without periodicity) relative to another. Thus, this latter material is nearly entirely amorphous, but differs from the first. Likewise, disturbance of order and periodicity may occur in crystalline materials. The terms ‘order’ and ‘disorder’ refer to the collective nature or degree of such disturbances. Although seemingly simple notions, ‘crystalline’ and ‘amorphous’ are complex concepts. Crystalline substances may show a periodic internal structure based on direction. For example, two-dimensional periodicity is common in phyllosilicates where two adjacent sheets or layers must mesh. For example, in serpentine, …

Pillared Clays and Clay Minerals

Abstract This chapter makes a general overview of pillared clay minerals. First, the general concepts of the process and the terminology recommended by the IUPAC are summarized, followed by the analysis of the host clay minerals and of the pillaring species, with special attention to the Al 13 polycation, mixed species, and new species. The main experimental pillaring methods are summarized, and also the main characteristics of the pillared solids, with special attention to the linking between the clay mineral layers and the polycations. Also, an overview of the mathematical modelling of pillaring processes is given. The chapter does not give exhaustive information in each item, available in review articles and books, but the general concepts needed for a general knowledge of the pillaring process and of the pillared solids.

Internally structured pickering emulsions stabilized by clay mineral particles

The present study aims to describe emulsion particles containing a dispersed phase composed of nanostructured lipid mesophases and stabilized by montmorillonite and/or Laponite clay platelets. The size distributions of these emulsion particles were found independent of the clay mineral content and of the initial internal composition that determines the internal structure. The stabilization of the droplets by a shell of smectite layers was found possible even by montmorillonite which has a length of the same order or more than the droplets to stabilize. The clay platelets give a local flatness to the droplets that may influence the internal structure. In this paper, we describe the conditions to obtain such soft particles of about 220 nm, and we show by direct visualization the internal mesophase complexity and the shape of the particles. In particular, TEM analysis showed elongated particles with bent-back channels at their center but a different morphology at the periphery due to flat border conditions imposed by the presence of the clay minerals.

Fixation of Zn2+ and Pb2+ by a Ca-montmorillonite in brines and dilute solutions: Preliminary results

Abstract This paper presents preliminary results on the fixation of Zn 2+ and Pb 2+ by a purified Wyoming Ca-montmorillonite, in different experimental conditions: variable (3 · 10 −5 I −2 M or constant ( I = 3.10 −2 M) low ionic strength solution, and high ( I = 3 M) ionic strength solutions at 20°C and 50°C. In low ionic strength solutions, the fixation of Zn 2+ and Pb 2+ appears to be controlled by ionic exchange mechanism; Zn 2+ and Pb 2+ adsorption are strongly favoured over Ca 2+ adsorption, Pb 2+ being more strongly fixed than Zn 2+ . In high ionic strength solutions, for both metals, amounts of exchanged heavy metals are very small. The fixation is higher in 1 M CaCl 2 than in 3 M NaCl solutions. Temperature has different effects on zinc and lead fixation. At 50°C, all the adsorption isotherms are shifted to higher values, except for lead in 1 M Cacl 2 solutions. XRD characterizations of samples exchanged in dilute solutions show a decrease of hydration states with increasing Zn 2+ and Pb 2+ contents in the interlamellar space. Systematic determinations of CEC were performed on these samples, using Cu(EDA) 2 Cl 2 . The CEC decreases with increasing Pb 2+ in clay, indicating that a part of exchanged Pb 2+ ecomes unexchangeable with (Cu(EDA) 2) 2+ . On Zn-exchanged samples, the CEC remains constant.

Preliminary results on the properties of pillared clays by mixed AlCu solutions

Abstract Three crude bentonites samples from USA (W), Tunisia (H) and Algeria (MR) have been used in order to prepare Cu-exchanged and new mixed AlCu pillared clays by three methods (i) a classical ‘dilute suspension and solution’ method by adding the nitrate pillaring solution to a 2% clay suspension, (ii) a ‘powder in solution’ method where the clay powder is dispersed in the pillaring solution and (iii) a ‘concentrated slurry’ method in which a dialysis bag containing clay-water slurry (33% w/w) is placed in the pillaring solution. These three methods are called D, P and CS respectively. Pillaring reactions was performed at 40°C with a OH/(Al + Cu) molar ratio ( R ) equal to 2 and at Cu/(Al + Cu) ratio of 0, 5 and 10%, respectively. Chemical analysis, X-ray diffraction, N 2 BET surface area and cation exchange capacity measurements were carried out to characterize the pillared materials. The results show that after calcination at 300°C, the three pillaring methods lead to a d 001 peak at about 1.8 urn which subsists after one year ageing, and which remains at 1.6 nm even at 800°C for some samples. Catalytic tests in oxidation reaction of phenol by H 2 O 2 in diluted aqueous solution performed at room temperature show an interesting activity of the Cu-clays.

Chapter 13.0 – Introduction to Clay–Polymer Nanocomposites (CPN)

Abstract Clay mineral–polymer nanocomposites were described for the first time in 1993. Since that date, they were the subject of thousands of research papers. Clay mineral–polymer nanocomposites must be carefully distinguished from microcomposites and intercalated composites. The following chapters describe polymer nanocomposites with smectites, kaolinites and fibrous clay minerals.

Chapter 7.5 Pillared Clays and Clay Minerals

Publisher Summary This chapter summarizes the vast volume of literature on (cationic) clay minerals that has accumulated over the past 30 years. A lot of fundamental work was realized in these three past decades on pillared interlayered clays (PILC), particularly with Al-pillared smectites. All the available data open the way to numerous questions and to the need of better understanding the hydrolysis of cations, even for the Al ion as the most studied one. Many other metal ions can act as pillaring species—for example, a few papers are published on PILC despite their high thermal stability and high acidity. The challenge will be to pillar modified kaolinite or sepiolite to take profit about its particular texture. These PILC must be used in some industrial or environmental applications. For this reason, one has to pay more attention to the fundamental point of view toward the pillaring in concentrated clay dispersions. Solid–solid state reaction remains a challenge for the future. In spite of the knowledge actually accumulated on PILC, two main questions remain (1) the real structure of the intercalated species before and after heating and (2) the type of bonds formed between the clay mineral host and the pillar guest that maintains the stability of the pillared clays minerals.