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2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a highly toxic environmental contaminant found in soils and sediments. Because of its exceptionally low water solubility, this compound exists predominantly in the sorbed state in natural environments. Clay minerals, especially expandable smectite clays, are one of the major component geosorbents in soils and sediments that can function as an effective adsorbent for environmental dioxins, including TCDD. In this study, TCDD was intercalated in the smectite clay saponite by an incipient wetness method. The primary goal of this study was to intercalate TCDD in natural K-saponite clay and evaluate its immunotoxic effects in vivo. The relative bioavailability of TCDD was evaluated by comparing the metabolic activity of TCDD administered in the adsorbed state as an intercalate in saponite and freely dissolved in corn oil. This comparison revealed nearly identical TCDD-induced suppression of humoral immunity, a well-established and sensitive sequela, in a mammalian (mouse) model. This result suggests that TCDD adsorbed by clays is likely to be available for biouptake and biodistribution in mammals, consistent with previous observations of TCDD in livestock exposed to dioxin-contaminated ball clays that were used as feed additives. Adsorption of TCDD by clay minerals does not appear to mitigate risk associated with TCDD exposure substantially., (Copyright © 2011 SETAC.)

Directly assembled wormhole mesostructures with high level functionalized mercaptan (MP-HMS) have been shown to be effective mercury(II) (Hg2+) trapping agents. Sorption of Hg2+ onto MP-HMS was investigated using X-ray absorption spectroscopy (XAS) to identify the structural coordination of the adsorbed Hg. Samples with different fractions of mercaptan functionalized groups (i.e., x = 0.1 and 0.5) with various Hg/S molar ratios ranging from 0.05 to 1.4 were investigated. XAS analysis indicates that adsorbed Hg first coordination shell is best fitted with an Hg-O path and an Hg-S path. The Hg-S atomic distance (R(Hg-S)) remained relatively constant while the Hg-S coordination numbers (CN) decreased as Hg/S loading increased. For the Hg-O path, both the CN and the R(Hg-O) increased with increasing Hg loading. XAS results suggest that at low Hg loadings, adsorbed Hg2+ forms mostly monodentate sulfur complexes (-S-Hg-OH) with the sulfur functional groups on the MP-HMS surfaces. At high Hg loadings, the Hg coordination environment is consistent with the formation of a double-layer structure of Hg attached to sulfur binding sites (-S-Hg-O-Hg-OH).

Silica mesostructures with well-expressed hexagonal and wormhole framework structures and up to 50% organo-functionalization of the framework silicon sites have been directly assembled from sodium silicate.

The in-situ graphitization of an as-made, large pore silica mesostructure templated by nonionic Pluronic 123 surfactant micelles provides a low cost pathway to the nanocasting of linear carbon nanotubes.

Abstract: Mesoporous forms of silica with wormhole framework structures prepared from tetraethylorthosilicate (denoted MSU-J-TEOS) or from sodium silicate (denoted MSU-J-SS) and an amine surfactant as the structure-directing porogen are highly effective reinforcing and toughening agents for rubbery and glassy epoxy polymers. The improvements in tensile strength and modulus provided by MSU-J silicas with a large average framework pore size (e.g., 5.9 and 21.3nm) are superior to those provided by the corresponding silicas made from the same TEOS or SS precursors but with smaller framework pore sizes (e.g., 4.2 and 5.2nm). The improved performance of the larger pore structures is realized even though the surface areas (∼670m2/g) are substantially lower than the surface areas of the smaller pore analogs (812–1025m2/g), most likely, because of more efficient polymer impregnation of the particle mesopores. In comparison to the MSU-J-TEOS silica assembled from TEOS, MSU-J-SS silica made from SS exhibits a more uniform pore distribution and smaller particles. These latter textural features lead to improved tensile strength and modulus without compromising the strain-at-break for both rubbery and glassy epoxy polymers. The exceptional strength and toughness provided by MSU-J-SS silica in comparison to MSU-J-TEOS silica are correlated with the high degree of dispersion of the mesophase particles in the epoxy matrix for the more effective distribution of stress and the deflection of microcracks. [Copyright &y& Elsevier]

The conversion of diphenylamine (DPA) and α-methylstyrene (AMS) to the antioxidants mono- and dicumenyldiphenylamine was carried out over mesostructured aluminosilicate catalysts with hexagonal (2% Al-MCM-41), wormhole (2% Al-HMS), and lamellar/vesicular (2% Al-MSU-G) framework structures. A commercial acid-treated clay catalyst, Engelhard F-20, was included for comparison perposes. The yields of the desired antioxidant, namely dicumenyldiphenylamine (DCDPA), increased in the order F-20 (∼57%)<2% Al-MCM-41 (∼85%)<2% Al-HMS, 2% Al-MSU-G (∼90%) when the reaction was carried out under stoichiometric reaction conditions at 90 °C. The DCDPA yields obtained with the mesostructured catalysts are the highest reported to date for this technologically important antioxidant. A heteropolyacid catalyst, H3PW12O40·xH2O (PW12) supported on mesostructured wormhole HMS and lamellar/vesicular MSU-G silica, also was examined as a catalyst for DCDPA production. The supported catalyst systems, however, afforded lower maximum yields of DCDPA (∼73–80%) in comparison to the mesostructured aluminosilicate catalysts. The exceptionally high yields of alkylated products obtained with the mesoporous aluminosilicate catalysts in comparison to the F-20 clay and the supported PW12 catalysts are attributable in part to intermediate acid strengths that minimize completing dimerization reactions of the AMS alkylating agent. Also, the pore structures of the mesostructured catalysts facilitate access to active sites on the framework walls and provide more efficient transport of reagents to framework reaction centers. Also, the regular mesoporosity of the aluminosilicate catalysts makes these structures less prone to pore plugging and to the masking of acidity through the adsorption of the high molecular weight reaction products. [Copyright &y& Elsevier]

Examines the effectiveness of framework sodium and local framework structure in determining the hydrothermal stability of MCM-41 mesostructures. Role of sodium ions in limiting the hydrothermal stability of the mesostructure; Device used in analyzing the MCM-41 mesostructures; Retention of residual sodium in the sodium silicate MCM-41.