Polyaniline/Montmorillonite Nanocomposites Obtained by In Situ Intercalation and Oxidative Polymerization in Cationic Modified-Clay (Sodium, Copper and Iron)

Polyaniline/montmorillonite nanocomposites (PANI/M) were obtained by intercalation of aniline monomer into M modified with different cations and subsequent oxidative polymerization of the aniline. The modified-clay was prepared by ion exchange of sodium, copper and iron cations in the clay (Na–M, Cu–M and Fe–M respectively). Infrared spectroscopy confirms the electrostatic interaction between the oxidized PANI and the negatively charged surface of the clay. X-ray diffraction analysis provides structural information of the prepared materials. The nanocomposites were characterized by transmission electron microscopy and their thermal degradation was investigated by thermogravimetric analysis. The weight loss suggests that the PANI chains in the nanocomposites have higher thermal stability than pure PANI. The electrical conductivity of the nanocomposites increased between 12 and 24 times with respect to the pure M and this increase was dependent on the cation-modification. The electrochemical behavior of the polymers extracted from the nanocomposites was studied by cyclic voltammetry and a good electrochemical response was observed.

Dissolved CO2 and Alkane Gas in Clay Formations

Characterization of dissolved CO2 and alkane gas in clayrocks may help assessing the confinement properties of geological barriers considered as potential host rocks for a deep geological disposal as well as for caprocks of gas storages. A monitoring of alkanes with CO2, combined with carbon isotopes was performed on core samples coming from Underground Research Laboratories (Bure, Mont Terri, Tournemire) and the Schlattingen borehole in France and Switzerland. Composition of hydrocarbon gas and delta C-13 of methane strongly suggest a dominant thermogenic origin of methane which is mixed with a bacterial origin for the Toarcian shales, Pliensbachien and Callovian-Oxfordian clayrocks. Results also evidence the contrasted behavior of CO2, which is controlled by chemical equilibrium between pore water and carbonate mineralogy, compared to the alkanes which are present in the porosity as a stock of dissolved gases which can be depleted during degassing experiments. (C) 2015 The Authors. Published by Elsevier B.V.

Distribution of grain size and clay minerals in surface sediments of the Kara Sea (Fig 4, 5)

In this paper, we summarize data on terrigenous sediment supply in the Kara Sea and its accumulation and spatial and temporal variability during Holocene times. Sedimentological, organic-geochemical, and micropaleontological proxies determined in surface sediments allow to characterize the modern (riverine) terrigenous sediment input. AMS-14C dated sediment cores from the Ob and Yenisei estuaries and the adjacent inner Kara Sea were investigated to determine the terrigenous sediment fluxes and their relationship to paleoenvironmental changes. The variability of sediment fluxes during Holocene times is related to the post-glacial sea-level rise and changes in river discharge and coastal erosion input. Whereas during the late/middle Holocene most of the terrigenous sediments were deposited in the estuaries and the areas directly off the estuaries, huge amounts of sediments accumulated on the Kara Sea shelf farther north during the early Holocene before about 9 cal kyr BP. The maximum accumulation at that time is related to the lowered sea level, increased coastal erosion, and increased river discharge. Based on sediment thickness charts, echograph profiles and sediment core data, we estimate an average Holocene (0-11 cal kyr BP) annual accumulation of 194,106 t/yr of total sediment for the whole Kara Sea. Based on late Holocene (modern) sediment accumulation in the estuaries, probably 12,106 t/yr of riverine suspended matter (i.e. about 30% of the input) may escape the marginal filter on a geological time scale and is transported onto the open Kara Sea shelf. The high-resolution magnetic susceptibility record of a Yenisei core suggests a short-term variability in Siberian climate and river discharge on a frequency of 300-700 yr. This variability may reflect natural cyclic climate variations to be seen in context with the interannual and interdecadal environmental changes recorded in the High Northern Latitudes over the last decades, such as the NAO/AO pattern. A major decrease in MS values starting near 2.5 cal kyr BP, being more pronounced during the last about 2 cal kyr BP, correlates with a cooling trend over Greenland as indicated in the GISP-2 Ice Core, extended sea-ice cover in the North Atlantic, and advances of glaciers in western Norway. Our still preliminary interpretation of the MS variability has to be proven by further MS records from additional cores as well as other high-resolution multi-proxy Arctic climate records.

Zr-Laponite pillared clay-based nickel catalysts for methane reforming with carbon dioxide

Zr-Laponite pillared clays were prepared and used as supports of nickel catalysts for the methane reforming reaction with carbon dioxide to synthesis gas. The structural and textural characteristics of supports and catalysts were systematically examined by N-2 adsorption/desorption and X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and transmission electron spectroscopy (TEM) techniques. The catalytic performance and carbon deposition were investigated. It is found that Zr-Laponite pillared clays are promising catalyst supports for carbon dioxide reforming of methane. The pore structure and surface properties of such supports greatly affect the catalytic behaviors of catalysts derived. Carbon deposition on catalysts was also affected by the property and structure of supports. The sintering of nickel metal and zirconia was another factor responsible for catalyst deactivation. This new-type nickel supported catalyst Ni/Zr-Laponite(8), with well-developed porosity, gave a higher initial conversion and a relatively long-term stability, and is therefore a promising catalyst for potential application to carbon dioxide reforming of methane to synthesis gas. (C) 2002 Elsevier Science B.V All rights reserved.