Molecular Treatment of Nano-Kaolinite Generations.

A procedure is developed for defining a compositionally and structurally realistic, atomic-scale description of exfoliated clay nanoparticles from the kaolinite family of phylloaluminosilicates. By use of coordination chemical principles, chemical environments within a nanoparticle can be separated into inner, outer, and peripheral spheres. The edges of the molecular models of nanoparticles were protonated in a validated manner to achieve charge neutrality.

Surface Characterization of Mechanochemically Modified Exfoliated Halloysite Nanoscrolls.

Surface modifications fundamentally influence the morphology of kaolinite nanostructures as a function of crystallinity and the presence of contaminants. Besides morphology, the catalytic properties of 1:1-type exfoliated aluminosilicates are also influenced by the presence of defect sites that can be generated in a controlled manner by mechanochemical activation. In this work, we investigated exfoliated halloysite nanoparticles with a quasi-homogeneous, scroll-type secondary structure toward developing structural/functional relationships for composition, atomic structure, and morphology.

Adsorption of phenolic compounds by organoclays: implications for the removal of organic pollutants from aqueous media.

Montmorillonite (MMT) was converted to organoclays by intercalation of cationic surfactants into its interlayer space. Two types of organoclays were prepared from different surfactants (DDTMA and DDDMA) at different surfactant loadings, and the structural changes in the clays investigated using various techniques. The arrangements of surfactant molecules in the interlayer space was visually aided by molecular mechanical calculation (MM calculation), and the adsorption capacities of MMT and the organoclays for the removal of p-chlorophenol (PCP) and p-nitrophenol (PNP) from aqueous solutions were tested under different conditions.

Structural characterisation and environmental application of organoclays for the removal of phenolic compounds.

Modified montmorillonite was prepared at different surfactant (HDTMA) loadings through ion exchange. The conformational arrangement of the loaded surfactants within the interlayer space of MMT was obtained by computational modelling. The conformational change of surfactant molecules enhance the visual understanding of the results obtained from characterization methods such as XRD and surface analysis of the organoclays.

Kaolinite-urea complexes obtained by mechanochemical and aqueous suspension techniques--a comparative study.

Intercalation compounds of low- and high-defect kaolinites have been prepared by direct reaction with urea aqueous solution as well as by co-grinding with urea in the absence of water (mechanochemical intercalation). The complexes formed were studied by X-ray diffraction, thermal analysis, DRIFT spectroscopy, and scanning electron microscopy. In aqueous solution the degree of intercalation for the low- and high-defect kaolinites was found to be 77 and 65%, respectively.

Mechanism for hydrotalcite decomposition: a controlled rate thermal analysis study.

The mechanism for the decomposition of hydrotalcite remains unsolved. Controlled rate thermal analysis enables this decomposition pathway to be explored. Hydrotalcites containing carbonate, vanadate and molybdate were prepared by coprecipitation.

Investigation of mechanochemically modified kaolinite surfaces by thermoanalytical and spectroscopic methods.

The effect of mechanochemical activation (dry grinding), formamide intercalation, and thermal deintercalation on high- and low-defect kaolinite surfaces was studied by thermogravimetry and diffuse reflectance Fourier transform infrared spectroscopy. These investigations were completed with specific surface area and pore size distribution measurements. The surface acidity of the ground and the ground-and-intercalated kaolinites was probed with ammonia adsorption.

Modification of kaolinite surfaces through mechanochemical activation with quartz: A diffuse reflectance infrared fourier transform and chemometrics study.

Studies of kaolinite surfaces are of industrial importance. One useful method for studying the changes in kaolinite surface properties is to apply chemometric analyses to the kaolinite surface infrared spectra. A comparison is made between the mechanochemical activation of Kiralyhegy kaolinites with significant amounts of natural quartz and the mechanochemical activation of Zettlitz kaolinite with added quartz.

Complexity of intercalation of hydrazine into kaolinite--a controlled rate thermal analysis and DRIFT spectroscopic study.

Controlled rate thermal analysis (CRTA) allows the separation of adsorbed and intercalated hydrazine. CRTA displays the presence of three different types of hydrogen-bonded hydrazine in the intercalation complex: (a) The first is adsorbed loosely bonded on the kaolinite structure fully expanded by hydrazine-hydrate and liberated between approx 50 and 70 degrees C (b) The second intercalated hydrazine is lost between approx 70 and 85 degrees C. (c) The third type of intercalated-hydrazine molecule is lost in the 85-130 degrees C range.

Deintercalation of hydrazine-intercalated kaolinite in dry and moist air.

The deintercalation of hydrazine-intercalated kaolinite has been followed using a combination of X-ray diffraction and diffuse reflectance Fourier transform infrared spectroscopy. Upon intercalation of the kaolinite with hydrazine, the kaolinite layers are expanded to 10.66 A and remain expanded for up to 22 h upon exposure to moist air.

Surface modification of mechanochemically activated kaolinites by selective leaching.

Low- and high-defect kaolinites mechanochemically activated for different periods of time have been treated with sulfuric acid solution. These modified materials were analyzed using a combination of X-ray diffraction, thermogravimetry, chemical analysis, diffuse reflectance Fourier transform infrared spectroscopy, as well as specific surface area and pore size distribution measurements. In addition to the mechanochemically amorphized part, the disordered and the adequately distorted phases also reacted with sulfuric acid.

Identification of superactive centers in thermally treated formamide-intercalated kaolinite.

The thermal behavior of a formamide-intercalated mechanochemically activated (dry-ground) kaolinite was investigated by thermogravimetry-mass spectrometry (TG-MS) and diffuse reflectance Fourier transform infrared spectroscopy (DRIFT). After the removal of adsorbed and intercalated formamide, a third type of bonded reagent was identified in the temperature range 230-350 degrees C decomposing in situ to CO and NH3. The presence of formamide decomposition products, as well as CO2 and various carbonates identified by DRIFT spectroscopy, indicates the formation of superactive centers as a result of mechanochemical activation and heat treatment (thermal deintercalation).

A spectroscopic study of mechanochemically activated kaolinite with the aid of chemometrics.

The study of kaolinite surfaces is of industrial importance. In this work we report the application of chemometrics to the study of modified kaolinite surfaces. DRIFT spectra of mechanochemically activated kaolinites (Kiralyhegy, Zettlitz, Szeg, and Birdwood) were analyzed using principal component analysis (PCA) and multicriteria decision making (MCDM) methods, PROMETHEE and GAIA.

Modification of low- and high-defect kaolinite surfaces: implications for kaolinite mineral processing.

A comparison is made of the mechanochemical activation of three low- and one high-defect kaolinite using a combination of X-ray diffraction, thermal analysis, and DRIFT spectroscopy. The effect of mechanochemical alteration of the kaolinites is greater for the low-defect kaolinites. The effectiveness of the mechanochemical treatment is represented by the slope of the d(001) peakwidth-grinding time line.

The effect of mechanochemical activation upon the intercalation of a high-defect kaolinite with formamide.

The effect of mechanochemical activation upon the intercalation of formamide into a high-defect kaolinite has been studied using a combination of X-ray diffraction, thermal analysis, and DRIFT spectroscopy. X-ray diffraction shows that the intensity of the d(001) spacing decreases with grinding time and that the intercalated high-defect kaolinite expands to 10.2 A.

A DRIFT spectroscopic study of potassium acetate intercalated mechanochemically activated kaolinite.

Kaolinite has been mechanochemically activated by dry grinding for periods of time up to 10 h. The kaolinite was then intercalated with potassium acetate and the changes in the structure followed by DRIFT spectroscopy. Intercalation of the kaolinite with potassium acetate is difficult and only the layers, which remain hydrogen bonded, are intercalated.

Mechanochemical Treatment of Kaolinite.

Kaolinite surfaces were modified by mechanochemical treatment for periods of time up to 10 h. X-ray diffraction shows a steady decrease in intensity of the d(001) spacing with mechanochemical treatment, resulting in the delamination of the kaolinite and a subsequent decrease in crystallite size with grinding time. Thermogravimetric analyses show the dehydroxylation patterns of kaolinite are significantly modified.

The Modification of Hydroxyl Surfaces of Formamide-Intercalated Kaolinites Synthesized by Controlled Rate Thermal Analysis.

Controlled rate thermal analysis (CRTA) technology made possible the separation of adsorbed formamide from intercalated formamide in formamide-intercalated kaolinites. X-ray diffraction shows that the CRTA-treated formamide-intercalated kaolinites remain expanded after CRTA treatment. The Raman spectra of the CRTA-treated formamide-intercalated kaolinites are significantly different from those of the intercalated kaolinites with both intercalated and adsorbed formamide.