Imre Dékány

Clay mineral-organic interactions

Abstract Organic compounds can interact with clay minerals by i) adsorption at the external surfaces, ii) adsorption at the external and internal surfaces, iii) by exchange of exchangeable ions at the external surfaces, iv) by exchange of exchangeable ions at the external and internal surfaces, and v) by grafting reactions with silanol and aluminol groups leading to covalent bonds. Kaolin minerals intercalate only are a limited number of compounds whereas the reactions of 2:1 clay minerals, in particular smectites and vermiculites, are very manifold. Special attention is given to the interaction with neutral organic molecules such as alcohols, fatty acids, amines, amino acids, aromatic compounds, macrocyclic compounds, and nuclein bases. The interaction with complexes and dyes also provides the basis of advanced applications of clay minerals. Binding of long chain alkylammonium ions is a fundamental reaction for hydrophobising clay mineral particles as needed in many applications. The interaction of clay minerals with polymers including proteins is not only an actual field of research but also of practical importance. Organo-clay minerals are used as effective adsorbents. As these materials also adsorb solvent molecules together with the adsorptive, the adsorption process must be considered as adsorption from binary solution which, therefore, is also described in this chapter.

ASPHALTENE ADSORPTION ON CLAYS AND CRUDE OIL RESERVOIR ROCKS

Abstract The adsorption of asphaltene on different clay minerals (kaolinite, illite, montmorillonite) and mineral oil reservoir rocks was studied. In toluene solution, specific adsorption was observed on kaolinite and a decrease in adsorption was found in the order illite-montmorillonite. In toluene/n-heptane mixtures a two-stage isotherm was recorded on the surface of the adsorbents. Surface modification by the adsorption of asphaltenes was characterized by a variety of structure-probing methods such as N2-adsorption, X-ray diffraction (XRD), small-angle X-ray scattering (SAXS) measurements, and FTIR spectroscopy. The hydrophobizing effect of asphaltene on clays was also checked by immersion microcalorimetry. According to XRD studies, no intercalation of asphaltene occurs in toluene and toluene/n-heptane mixture on montmorillonites. SAXS scattering curves measured on kaolinite samples deviate from each other in the angle range close to primary scattering, because of the preferential adsorption of asphaltene. The aggregation of clays by asphaltene also manifests itself in a decrease of specific surface areas determined by N2-adsorption.

Colloid Clay Science

Abstract The knowledge of the properties of colloidal dispersions is fundamental for designing and optimizing the usage of clays and clay minerals. The colloidal behaviour of these dispersions is very complex due to the anisometric (and often irregular) particle shape, the anisometric and pH-dependent charge distribution, the variable particle dimensions as a consequence of swelling, delamination and exfoliation, and the ion-exchange properties. Therefore, this chapter gives information on the structure, charge distribution, structure of the hydrates, diffuse ionic layer, and the interactions between the colloidal clay mineral particles (electrostatic, van der Waals, ion correlation, steric stabilization). A large section refers to the coagulation of clay mineral dispersions by salts, the influence of organic compounds, and the destabilization (flocculation by bridging or charge neutralization) or stabilization by polymers (by recharging or steric stabilization). In a further section is described the aggregation of clay mineral particles leading to different types of sediments (decisively determining sealing, plastering, stirring, filtration processes, plasticity) or resulting in gel formation, often with thixotropic properties. Also mentioned is the preparation of colloidal metal (hydr)oxides and sulphides within the network of clay mineral particles or even between the clay mineral layers.

Removal of 2-chlorophenol from water by adsorption combined with TiO2 photocatalysis

Abstract The results of a laboratory-scale study of an environmentally friendly water treatment method is presented, where the organic model pollutant 2-chlorophenol (2-CP) was first adsorbed and then removed by a direct photolytic or heterogeneous photocatalytic process. The adsorbent was an organically treated (with hexadecylpyridinium chloride) clay mineral (montmorillonite), and the photocatalyst was Degussa P25. The total organic carbon and total inorganic chloride contents were measured to monitor the mineralization process, while the degradation of 2-CP and the formation of intermediates were followed by HPLC. No negative effect of the suspended adsorbent was observed either in the direct photolytic process or in the heterogeneous photocatalytic degradation process. Although direct photolysis allows the highest degree of 2-CP removal, in this case the degradation of the organic pollutant is accompanied by destruction of the adsorbent. The removal of 2-CP through the combination of adsorption and heterogeneous photocatalysis was achieved in a reasonable acceptable time interval, and can therefore be suggested as an efficient, cost-effective and environment-friendly water treatment facility.

Functionalization of gold nanoparticles with amino acid, β-amyloid peptides and fragment

Gold nanoparticles (Au NPs) were functionalized by cysteine (Cys), beta-amyloid peptides (Cys(0)Abeta(1-28), Cys(0)Abeta(1-40), Abeta(1-42)) and a pentapeptide fragment (Leu-Pro-Phe-Phe-Asp-OH (LPFFD-OH)). Optical absorption spectra of these systems were recorded and the plasmon resonance maximum values (lambda(max)) of the UV-vis spectra together with the transmission electron microscopy (TEM) images were also analysed. Both TEM images and the appearance of a new absorption band between approximately 720 and 750 nm in the visible spectra of the Au-cysteine and Au-LPFFD-OH systems most probably indicate that upon addition of these molecules to Au NPs-containing aqueous dispersions formation of aggregates is occurred. The wavelength shift between the two observed absorption bands in cysteine- and pentapeptide-modified Au NPs systems are Deltalambda=185 and 193 nm, respectively. These results suggest that the monodisperse spherical gold nanoparticles were arranged to chained structure due to the effect of these molecules. For confirmation of the binding of citrate and cysteine onto the plasmonic metal surface (1)H NMR measurements were also performed. (1)H NMR results may suggest that the citrate layer on the metal surface is replaced by cysteine leading to a formation of organic double layer structure. In the presence of beta-amyloid peptides the aggregation was not observed, especially in the Au-Cys(0)Abeta(1-40) and Au-Abeta(1-42) systems, however compared to the cysteine or LPFFD-OH-containing gold dispersion with Cys(0)Abeta(1-28) measurable less aggregation were occurred. The spectral parameters clearly suggest that Abeta(1-42) can attach or bind to the surface of gold nanoparticles via both the apolar and the N-donors containing side-chains of amino acids and no aggregation in the colloidal gold dispersion was observed.

Synthesis and characterization of silver nanoparticle/kaolinite composites

Abstract Ag nanoparticles were synthetized in the interlamellar space of a layered kaolinite clay mineral. Disaggregation of the lamellae of non-swelling kaolinite was achieved by intercalation of dimethyl sulfoxide. The kaolinite was suspended in aqueous AgNO 3 solution and, after adsorption of Ag + , the ions were reduced with NaBH 4 . The interlamellar space limits particle growth ( d ave =3.8–4.2 nm); however, larger silver particles may be formed on the exterior surface of kaolinite with d ave =5.6–10.5 nm diameter. The diameter of the particles prepared in this way is depending on the initial AgNO 3 concentration. The silver nanoparticles prepared were characterized by UV–vis spectroscopy, X-ray diffraction (XRD), Small angle X-ray scattering (SAXS), X-ray photoelectron spectroscopy (XPS) and Transmission electron microscopy (TEM).

Nanoparticles in Solids and Solutions

Preface. Glossary of Acronyms. Membrane Mimetic Approaches to Nanoparticle Preparation - General Introduction J.H. Fendler. Epitaxial Growth of Nanoparticles - Mechanistic Comparisons of Physical and Chemical Processes G. Vidali. Physical Characterizations of Nanoparticle Interfaces U. Kreibig, et al. Nanocrystals at the Air/Liquid Interface as Transients in Crystallization M. Lahav, L. Leiserowitz. Crystalline Colloidal Array Optical Switching Devices S. Asher, G. Pan. Nanoparticles in Microemulsions: A General Approach J.B. Nagy, et al. Nanoparticles in Polymers and Polymeric Dendrimers I. Cabasso, Y. Yuan. Discussion I. Polarography and Voltammetry of Ultrasmall Colloids M. Heyrovsky, J. Jirkovsky. The Role of Semiconductors/Substrate Mismatch in the Formation of Electrodeposited Quantum Dots G. Hodes, et al. Mechanical, Electrical and Photoelectrical Energy Interconversion in Nanomembranes A. Petrov. M. Spassova, J.H. Fendler. Discussion II. Preparation and Properties of Well Defined Dispersions of Inorganic Fine Particles E. Matijevic, Y.-S. Her. Particle Aggregation: Modeling and Measurement J. Gregory. Smart Colloidal Systems B. Vincent. Stabilization of Colloidal Particles by Homopolymers and Block Copolymers G.J. Fleer. Discussion III. Preparation of Nanoparticles in the Interfacial Layer of Binary Liquids on Solid Support I. Dekany. Ferrofluid of Cobalt Ferrite Differing by Their Particle Sizes M.-P. Pileni. Chemical Approaches to Quantized Nanostructures H. Weller. Discussion V. Nanolayers of Liquids N.V. Churaev. Nanostructures and Nanoparticles in Thin Organic Films. X-ray, Neutron and Electron Diffraction Studies L.Feigin. Adsorption Induced Structural Changes of Supported Rhodium Nanoparticles F. Solymosi. Multiple Nanocontacts D. Meissner. Discussion V. The Photophysics of Mn2+ on ZNS Nanoclusters K. Sooklal, et al. A New Solution Phase Synthesis for Silicon Nanoclusters R. Bley, S.M. Kauzlarich. Diffraction of Visible Light from Colloidal Crystals of Silica in Polymer Composites J. Jethmalani, W.T. Ford. Raman and Photoluminescence Spectra of Diamond Particles with 1-5 nm Diameter E.D. Obraztsova, et al. On the Role of Nanoparticle Sizes in Monoelectron Conductivity S. Carrara, et al. Preparation of Colloidal Nanocrystals of AgX and AG2Se from Microemulsion P. Monnoyer, et al. Structural Characterization of Sol-Gel Dip-Coating CEO2 and CEO2/SNO2 Films Z. Crnjak Orel, et al. Inorganic Semiconductor Nanoparticles and Organic Semiconductor Nanowires in Clay-Minerals: Electrochemical and Fiber Optic Survey P. Joo, et al. Formation of Nanosize Particles in an RF Thermal Plasma Torch J. Szepvolgyi, et al. Preparation and Characterization of FeS and Fe2O3 Nanoparticles on Silica and Silicate Supports I. Dekany, et al. Single Nanosized Au Particle-Enhanced Fluorescence of J-Aggregates Probed by Near Field Scanning Optical Microscopy Y. Tian, et al. Concluding Discussions J.H. Fendler, I. Dekany. Subject Index.

The structure of acid treated sepiolites : small-angle X-ray scattering and multi MAS-NMR investigations

Abstract Structural changes in the chain silicate sepiolite brought about by acid treatment were studied by X-ray diffraction, gas adsorption and MAS-NMR methods. It was established that as the amount of iron and aluminum extracted from the mineral is increased, the specific surface area of the sample is also increased (from 195.2 to 306.6 m 2 /g) and the originally microporous structure is transformed into a mesoporous one. The ion exchange capacity of sepiolite (0.486 mequ/g) may be completely eliminated by acid treatment. The changes in the surface fractal dimension D s (from 2.35 to 2.03) and the correlation length l c (from 24.9 nm to 17.6 nm) were followed by SAXS measurements. 29 Si − and 27 Al−MAS−NMR studies yield information on changes occurring in the structure of the mineral, i.e., on the arrangement of Si and Al atoms in the lattice. During acid treatment the clay structure is progressively transformed into amorphous silica–alumina.

Two-dimensional ordering of Stöber silica particles at the air/water interface

Monolayers of Stober silica particles were prepared on the surface of water and deposited onto glass substrates by the Langmuir–Blodgett method. Prior to film formation the surface of the silica particles was methoxylated by washing with methanol at room temperature. The surface methoxylation was characterized by FTIR, 13C CP MAS NMR and 29Si MAS NMR investigations. Good quality hexagonally close-packed (hcp) films of silica particles were prepared from methanol dispersions of the methoxylated spherical (d=689 nm) monodisperse particles. Large (10×10 μm of size), perfectly hcp ordered domains were found in scanning electron microscopic pictures of such monolayers deposited on glass substrates. Addition of the cationic surfactant decyltrimethyl ammonium bromide (DTABr) to the spreading suspensions decreased the ordering quality. All the particle monolayers showed first and second order Bragg diffraction at the wavelengths λ=1450 and 780–790 nm, respectively. The SiO2 background light transmission decreased with loss of ordering caused by the addition of DTABr.

Sorption and immersional wetting on clay minerals having modified surface: II. Interlamellar sorption and wetting on organic montmorillonites

Abstract Adsorption of methanol-benzene mixtures and heats of immersion have been investigated on the organic derivatives of montmorillonite. The surface of the mineral was modified by n-alkyl pyridinium and dimethyldihexadecyl ammonium ions. In the case of completely exchanged samples the adsorption capacity volumes agree with the interlamellar volumes calculated from X-ray diffraction data rather well. The organophilicity is characterized by the proportion of the nonpolar/polar surfaces. The specific enthalpies of immersion have been measured in methanol, benzene, and their mixtures. The immersion shows endothermic-exothermic or endothermic heat effects.