Stepwise dansyl grafting on the kaolinite interlayer surface

Integrating Structural and Thermodynamic Mechanisms for Methanol Intercalated Kaolinite Nanoclay: Experiments and Density Functional Theory Simulation

Methanol intercalated kaolinite (Kaol) plays an important role in the intercalation, exfoliation, and organic modification of kaolinite nanoclay. However, the evolution of the layer structure of Kaol and its thermodynamic stability during the methanol intercalation process have not been clarified at the atomic level. Here, by combination of density functional theory (DFT) calculation and experimental characterizations, the interlayer bonding, structure evolution, and energetics from dimethyl sulfoxide (DMSO) intercalated Kaol to methanol intercalated Kaol were investigated. Partial methanol molecules entered the interlayers of Kaol to form some intermediate structures with the same d-spacing as that of DMSO intercalated Kaol. Different numbers of grafted methoxy and water molecules coexist together in the interlayer to form the final structures of methanol intercalated kaolinite (MeOm/nH2O/Kaol). The whole intercalation process is energy-consuming, and the presence of DMSO would affect the intercalation of methanol. Meanwhile, the formation energy from intermediate structures to final structures was found reduced under the participation of water.

Characterization and Modeling Quality Analysis of Edible Oils Using Electrochemical Impedance Spectroscopy

The dielectric characteristics of six culinary oils were measured over the frequency range of 0.01 Hz–100 kHz. The results showed that the dielectric constants of oils had the same frequency relationship (i.e., they decreased with increasing frequency). The dielectric constants at lower frequencies for olive oil A, olive oil B, sesame oil, Nigella sativa, sunflower oil, and corn oil are approximately 2.75, 2.5, 2.0, 1.75, 1.5, and 0.9. An FT-IR analysis showed that the spectral differences were very small, because most vegetable oils contain the same type of fatty acids. The model built using COMSOL Multiphysics for the potential and electric field distributions for different oils and used to calculate the dielectric constant was simulated under various conditions in the AC/DC module. The model results were compared with the experimental results, which showed satisfactory convergence between them. The experimental and model results obtained in this study could be useful for evaluating the edible oil quality.

Swelling layered minerals applications: A solid state NMR overview

Swelling layered clay minerals form an important sub-group of the phyllosilicate family. They are characterized by their ability to expand or contract in the presence or absence of water. This property makes them useful for a variety of applications, ranging from environmental technologies to heterogeneous catalysis, and including pharmaceutical and industrial applications. Solid State Nuclear Magnetic Resonance (SS-NMR) has been extensively applied in the characterization of these materials, providing useful information on their dynamics and structure that is inaccessible using other characterization methods such as X-ray diffraction. In this review, we present the key contributions of SS-NMR to the understanding of the mechanisms that govern some of the main applications associated to swelling clay minerals. The article is divided in two parts. The first part presents SS-NMR conventional applications to layered clay minerals, while the second part comprises an in-depth review of the information that SS-NMR can provide about the different properties of swelling layered clay minerals.

Modelling, characterization and quality analysis of heated oil using electric moment and chemical properties

The effect of temperature (30-90 °C) on the electrical parameter: dielectric constant (ε_r) of Sunflower, Olive and Corn oil exposed to three cycles of heating to frying temperature (175 ± 5 °C) was studied to exhibit the quality analysis of oil. Dielectric constant of heated oil was measured using designed inter-digitated electrode capacitor at different frequency (10 kHz-5 MHz) and temperature (30-90 °C). Dielectric constant (ε_r) of oil samples increases with cycles of heating. Variation of dielectric constant with frequency was premeditated using quadratic equation and the dependency factor was observed to be R² > 0.914. Chemical kinetic dielectric constant with temperature was studied using Arrhenius law and observed that activation energy increases with cycles of heating. Andrade's equation was also fitted with the variation of ε_r with temperature and the dependency factor (R² between 0.978 to 0.999) was observed to be highly correlated. Experiential physical properties like density, refractive index and ε_r were significantly correlated with the pragmatic peroxide value. The observed relation between ε_r with chemical property divulges the suitability of measured dielectric constant in real time and continuous evaluation of edible oil quality analysis in food industry.

New organophilic kaolin clays based on single-point grafted 3-aminopropyl dimethylethoxysilane

In this study, the organophilization procedure of kaolin rocks with a monofunctional ethoxysilane- 3 aminopropyl dimethyl ethoxysilane (APMS) is depicted for the first time. The two-step organophilization procedure, including dimethyl sulfoxide intercalation and APMS grafting onto the inner hydroxyl surface of kaolinite (the mineral) layers was tested for three sources of kaolin rocks (KR, KC and KD) with various morphologies and kaolinite compositions. The load of APMS in the kaolinite interlayer space was higher than that of 3-aminopropyl triethoxysilane (APTS) due to the single-point grafting nature of the organophilization reaction. A higher long-distance order of kaolinite layers with low staking was obtained for the APMS, due to a more controllable organiphilization reaction. Last but not least, the solid state (29)Si-NMR tests confirmed the single-point grafting mechanism of APMS, corroborating monodentate fixation on the kaolinite hydroxyl facets, with no contribution to the bidentate or tridentate fixation as observed for APTS.