GeoScienceWorld
Volume

Surface Modification of Clays and Nanocomposites

  1. Page 1
    Abstract
    e-mail: cp21@txstate.edu

    Montmorillonite is an extraordinary, naturally occurring plate-like material ~1 nm thick with dimensions of at least 150-200 nm with robust mechanical properties (the modulus is ~ 180 GPa). It is non-toxic (the FDA classification of montmorillonite is GRAS (‘generally regarded as safe’ for most applications)). The surface area of the particle is enormous (>750m2/g). The capacity of montmorillonite to have a negative charge allows for the modification of the montmorillonite with quaternary ammonium ions (which have a positive charge) to displace the inorganic counter ions associated with the mineral. This displacement provides a wide range of hydrophilic-hydrophobic balance on the surface of montmorillonite which is key to the utilization of organomontmorillonites in a wide range of different markets (rheology control for coatings, inks, oil-well drilling fluids, grease, etc. and polymer nanocomposites). The utility of organomontmorillonite is not discussed here.

    The significant independent variables that relate to successful preparation of organo-montmorillonites are described below and listed in the conclusions.

  2. Page 13
    Abstract
    e-mail: gb11@txstate.edu

    Smectite clays have been modified with organic onium ions for more than 60 y and are important in a diverse range of industries including oil-well drilling, paint, grease, ink, cosmetics, environmental clean-up, polymer nanocomposites, and pharmaceuticals. The number of commercially available onium ions limits the variety of surface modifications that can be made. A substantial amount of research has been conducted on other methods of organic modification of smectite clays in order to remedy this situation. One method that has seen increased attention is the use of ion-dipole-bonding of organic molecules, oligomers, or polymers to the exchangeable cation on the clay surface. Utilizing this method, a unique class of surface-modified clays can be produced. In some cases self-assembly of certain organic molecules has been discovered in which the molecules form rigid posts around each cation on the surface. The intercalation/exfoliation behavior of smectite clays modified via ion-dipole bonding utilizing various small organic molecules and selected polar polymers is discussed here. The types of organic molecules that can be utilized to surface modify smectites is discussed in detail as are the characteristics of the complexes that are formed.

  3. Page 27
    Abstract
    e-mail: jmatusik@agh.edu.pl

    The kaolin-group minerals with 1:1 layered structure can be used for the synthesis of new hybrid organo-inorganic nanomaterials. An appropriate selection of the reacting molecules introduced via intercalation and/or grafting reactions and synthesis conditions may induce interesting properties, e.g. luminescence, catalytic activity, and affinity to sorb ions and molecules. To date, several new materials have been synthesized using the 1:1 layered structure as a building block. The most interesting materials could be obtained via grafting reaction involving the inner-surface OH groups of the octahedral sheet. Such materials show increased thermal stability as well as stability in aqueous solutions, unlike intercalation compounds. Note the susceptibility of the octahedral sheet of kaolinite to interact with selected organic molecules and the subsequent formation of Al–O–C bonds in the interlayer. Four different types of materials which could be obtained using kaolin-group minerals and their possible applications are discussed here: (1) kaolinite nanotubes in the synthesis of polylactide-based nanocomposites; (2) methoxy-kaolinite and intercalates with ammonium salts; (3) interlayer quaternized kaolinites and their anion-exchange properties; and (4) interlayer grafted kaolinites for heavy-metal sorption.

  4. Page 39
    Abstract
    e-mail: jocelyne.brendle@uha.fr

    The present chapter is devoted to recent developments in the area of surface modifications of commercially available synthetic clays by post treatments (i.e. intercalation or grafting) and by one-pot synthesis through a sol-gel process. Special attention is paid to the modifications aimed at forming pillared clays, organoclays, and organic-inorganic hybrids with a 2:1 layered structure. The different approaches are described and debated. The properties of the materials obtained are also discussed.

  5. Page 61
    Abstract
    e-mail: mengyzh@mail.sysu.edu.cne-mail: luyi.sun@uconn.edu

    In this work, we explored to The grafting of thiol group- terminated chains onto single- layer α-zirconium phosphate (ZrP) nanosheets, which were subsequently oxidized to sulfonic- acid groups, was examined here. The sulfuric acid- functionalized ZrP nanosheets were thoroughly characterized extensively and the results proved that sulfonic acid group- terminated chains were successfully grafted successfully onto the ZrP nanosheets surfaces with a high significant loading density. Such Such a strong a solid acid, based on inorganic nanosheets, can be well dispersed in polar solvents, leading to high good access to the acid functional groups. The acid Meanwhile, it can also be easily separated easily from the dispersion system by centrifugation or filtration. The sulfonic acid- functionalized ZrP nanosheets can serve as an effective heterogeneous catalyst for various reactions (such as the Baeyer-Villiger oxidation). The nanosheets y were also incorporated into proton- exchange membranes to form composite membranes, which exhibited excellent performance in single- cell evaluation, showing promiseing for fuel-cell applications.

  6. Page 73
    Abstract
    e-mail: rytwo@telhai.ac.il

    Three relatively unusual techniques that might deliver interesting information about the surface modifications performed on clay minerals are described here. The instruments used and the techniques were: (1) a streaming current detector (more commonly known as particle-charge detector) to monitor changes in the colloidal charge of the surfaces of modified particles; (2) a dispersion analyzer to monitor sedimentation/ dispersion behavior as a function of the modification, and in several cases even to yield a very good estimate of size of the particles (as long as they are between 10 nm and 10 mm); and (3) nuclear magnetic resonance-based specific surface area measurements, that yield information on the area and in some cases even on changes in the hydrophobic-hydrophillic surfaces formed due to the modification. As with all analytical techniques, these methods have advantages accompanied by problems, interesting research opportunities coupled with severe limitations that might lead to misinterpretation of the results. A few examples for each technique are presented here.

  7. Page 87
    Abstract
    e-mail: aranda@icmm.csic.es

    Fibrous clay minerals (sepiolite and palygorskite) have large specific surface areas which offer interesting opportunities for the assembly of diverse types of nanoparticles (NPs) which, in certain cases, remain bonded through the silanol groups located at the external surfaces of these clays. Various methodologies used in the preparation of new nanoarchitectures, based on the attachment of NPs to fibrous clays, with special emphasis on the use of the sol-gel approach combined with organosepiolites to build nanostructured porous functional materials for different applications (e.g. photocatalysis), are introduced here. Other examples refer to the in situ formation of NPs, e.g. zeolites, which become attached to the clay fiber during the synthesis process via covalent bonds. The use of ferrofluids allows the development of nanoarchitectures in which iron-oxide NPs decorate sepiolite fibers and add superparamagnetic properties to the resulting materials. Examples of various multifunctional materials based on magnetite-sepiolite nanoarchitectures are also introduced and discussed critically here.

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