Influence of smectite suspension structure on sheet orientation in dry sediments: XRD and AFM applications

The structure-building phenomena within clay aggregates are governed by forces acting between clay particles. Measurements of such forces are important to understand in order to manipulate the aggregate structure for applications such as dewatering of mineral processing tailings. A parallel particle orientation is required when conducting XRD investigation on the oriented samples and conduct force measurements acting between basal planes of clay mineral platelets using at. force microscopy (AFM). To investigate how smectite clay platelets were oriented on silicon wafer substrate when dried from suspension range of methods like SEM, XRD and AFM were employed. From these investigations, we conclude that high clay concns. and larger particle diams. (up to 5 μm) in suspension result in random orientation of platelets in the substrate. The best possible laminar orientation in the clay dry film, represented in the XRD 0 0 1/0 2 0 intensity ratio of 47 was obtained by drying thin layers from 0.02 wt.% clay suspensions of the natural pH. Conducted AFM investigations show that smectite studied in water based electrolytes show very long-range repulsive forces lower in strength than electrostatic forces from double-layer repulsion. It was suggested that these forces may have structural nature. Smectite surface layers rehydrate in water environment forms surface gel with spongy and cellular texture which cushion approaching AFM probe. This structural effect can be measured in distances larger than 1000 nm from substrate surface and when probe penetrate this gel layer, structural linkages are forming between substrate and clay covered probe. These linkages prevent subsequently smooth detachments of AFM probe on way back when retrieval. This effect of tearing new formed structure apart involves larger adhesion-like forces measured in retrieval. It is also suggested that these effect may be enhanced by the nano-clay particles interaction

TEM, XRD, and Thermal Stability of Adsorbed Paranitrophenol on DDOAB Organoclay

Water purification is of extreme importance to modern society. Organoclays through adsorption of recalcitrant organics provides one mechanism for the removal of these molecules. The organoclay was synthesised through ion exchange with dimethyldioctadecylammonium bromide labeled as DDOAB of formula (CH3(CH2)17)2NBr(CH3)2. Paranitrophenol was adsorbed on the organoclay at a range of concentrations according to the cation exchange capacity (CEC) of the host montmorillonite. The paranitrophenol in solution was analysed by a UV-260 spectrophotometer at 317nm, with detection limits being 0.05mg/L. The expansion of the montmorillonite was studied by a combination of X-ray diffraction and transmission electron microscopy. Upon adsorption of the paranitrophenol the basal spacing decreased. The thermal stability of the organoclay was determined by a combination of thermogravimetry and infrared emission spectroscopy. The surfactant molecule DDOAB combusts at 166, 244 and 304 degrees Celsius and upon intercalation into Na-montmorillonite is retained up to 389 degrees Celsius thus showing the organoclay is stable to significantly high temperatures well above the combustion/decomposition temperature of the organoclay

Morphology and internal structure of Antarctic cosmic dust spherules: Possible links to meteorite fusion crusts

Petrographic and SEM comparison of the outer morphology of different Antarctic spherules with their internal structure helped to distinguish those spherules that resulted from melting of micrometeorites from the ablation products of meteorites. A chain of possible transformations beginning with unmelted micrometeorites was recognized. Such structural transformations could begin from unmelted cosmic dust of olivine aggregates through granular spherules, to vitrophyric spherules with ghost-olivine glassy ovoidal objects, to vitrophyric, and to skeletal spherules. The fusion crusts of meteorites studied, showed that ablation can also produce a variety of spherules. Achondrites could produce glassy smooth, and internally compact holohyaline spherules, whereas chondrites could generate spherules of the rough glazed, dendrite decorated morphological types

Castration du porcelet : évaluation de l'efficacité analgésique per-opératoire de l'huile essentielle Mentha arvensis (menthe des champs) par l'analyse des vocalisations

La castration des porcelets mâles est légalement pratiquée avant l'âge de 7 jours sans analgésie ni anesthésie, Cette castration chirurgicale cause une douleur importante aux porcelets. Dans un contexte où le bien-être animal a une place importante, et où l'engouement pour les "médecines alternatives" prend de l'ampleur, l'objet de notre projet est d'évaluer l'efficacité analgésique de l'huile essentielle de menthe des champs en application topique avant la castration, L'outil choisi pour évaluer la douleur est l'étude des vocalises des porcelets. La présente étude n'a pas permis de démontrer l'efficacité analgésique de l'huile essentielle de menthe des champs. La discussion porte sur l'évaluation à postériori du protocole choisi

Sodium Aluminosilicate Solid Phase Specific Fouling Behaviour

Process heat transfer equipment fouling due to sodium aluminosilicate precipitation is a serious problem that confronts high-level nuclear waste liquor and Bayer process alumina processing plants. The fouling of 316 stainless steel substrate by thermodynamically stable and unstable sodium aluminosilicate polytypes: amorphous solid, zeolite A, sodalite and cancrinite crystals, been has studied in an isothermal, batch precipitation system at 65 °C. Fouling invariably occurred via heterogeneous nucleation, crystal growth and particulate adsorption processes, accompanied by solution-mediated, phase transformation and morphological changes. For the thermodynamically stable cancrinite fouling, the amount of scale deposited increased systematically with increasing crystallization time before levelling off as a result of depleted supersaturation. Where the deposited scale involved a less stable phase (e.g., amorphous, zeolite A), transformation to a more stable phases (e.g., sodalite/cancrinite) occurred. The scale layer coverage/growth characteristically increased and then decreased in a periodic manner. The periodicity of this unusual behaviour appeared to be directly and kinetically related to polytypic phase transformation of amorphous to zeolite A, zeolite A to sodalite and sodalite to cancrinite

Smectite clay microstructural behaviour on the Atterberg limits transition

Particle space arrangement is a very important factor that determines the physico-mechanical properties of soil. Formations of three-dimensional (3D) structured networks within gelled or flocculated suspension may prevent clay particles and aggregates from building dense aggregates and by encapsulate water within the ultrathin and closed void network, lead to poor sludge dewatering. To better understand the water retention behaviour of smectite-rich clays, a microstructural investigation was conducted on Amcol Australian bentonite in aqueous suspension in near the liquid limit (LL) and the plastic limit (PL). The investigation was conducted with the aid of synchrotron-powered transmission X-ray microscope tomography (TXM), with subsequent computer reconstruction. Images from the microscopy studies were statistically analysed using the STatistical IMage ANalysing (STIMAN) system. The study found that clay particles form a spanned framework in which mineral particles, aggregates and water-filled voids assemble as hierarchic structural elements. The size of these structural elements was larger in the water suspension and subsequently became smaller as an effect of water loss in the suspension>liquid and>plastic limit conditions. The clay suspension structure was almost isometric, with a low anisotropy coefficient: K - 9%. This parameter increased to K - 17% in (LL) and increased further in (PL) conditions to K - 35%. Voids within structural elements were much smaller than the water filled inter-flock voids, with their median diameter 140nm (suspension), 120nm (LL) and 90nm (PL). Significant differences in Atterberg limits values were observed between powder freshly mixed with water and a seasoned sample. Therefore, careful consideration of the sample mineral composition, clay content and genesis must be given due to preparation for geotechnical examination

Simulation of Doxorubicin Delivery via Glucosamine(ethylene glycol) Carrier

This article focuses on the molecular modeling of the release of doxorubicin from capsules composed of glucosamine(ethylene glycol) oligomers. Doxorubicin forms micelle structures with glucosamine(ethylene glycol), and the drug release mechanism can be studied through the modeling of oligomeric bond breaking under acidic, neutral, or basic conditions. Under these conditions, the activation energies were calculated to be 145.51, 135.78, and 287.60 kcal/mol, respectively, at the B3LYP/6-31G//PM3 level. Based on these values, doxorubicin can be released into acidic and neutral solutions but not into basic solution. Ethylene glycol chain length in glucosamine(ethylene glycol) also effects drug release. As the length of ethylene glycol increases, the amount of drug released increases under acidic conditions, but decreases under neutral and basic conditions. When the drug is released from glucosamine(ethylene glycol) oligomers, the drug molecule and glucosamine(ethylene glycol) molecules form a micelle structure. Studies found that, as the length of the ethylene glycol chains increases, the micelle structure is more easily formed. The ethylene glycol group can deliver doxorubicin to cancer cells in micelle form

Binding and Docking Interactions of NO, CO and O2 in Heme Proteins as Probed by Density Functional Theory

Dynamics and reactivity in heme proteins include direct and indirect interactions of the ligands/substrates like CO, NO and O2 with the environment. Direct electrostatic interactions result from amino acid side chains in the inner cavities and/or metal coordination in the active site, whereas indirect interactions result by ligands in the same coordination sphere. Interactions play a crucial role in stabilizing transition states in catalysis or altering ligation chemistry. We have probed, by Density Functional Theory (DFT), the perturbation degree in the stretching vibrational frequencies of CO, NO and O2 molecules in the presence of electrostatic interactions or hydrogen bonds, under conditions simulating the inner cavities. Moreover, we have studied the vibrational characteristics of the heme bound form of the CO and NO ligands by altering the chemistry of the proximal to the heme ligand. CO, NO and O2 molecules are highly polarizable exerting vibrational shifts up to 80, 200 and 120 cm−1, respectively, compared to the non-interacting ligand. The importance of Density Functional Theory (DFT) methodology in the investigation of the heme-ligand-protein interactions is also addressed