No abstract

A one-step, direct method is described for the creation of synthetic smectite clays grafted with organics on the interlayer surfaces using an organotrialkoxysilane as the silica source. The silane employed most successfully is phenyltriethoxysilane (PTES). Aqueous slurries of LiF, magnesium hydroxide, and the silane are refluxed for 2−5 days, and desirable molar compositions are determined. X-ray powder diffraction, thermal analysis, IR, TEM, N2 sorption isotherms, and solid-state 13C and 29Si NMR techniques are used to characterize the products. The loading of organics on the PTES−hectorites is determined at 20−25% and is comprised of phenyl groups as Si−C linkages. Evidence of this linkage includes an IR peak at 1430 cm-1 and 29Si NMR assignments at −79 and −66 ppm for RSi(OMg)(OSi)2 and RSi(OMg)(OSi)(OH) species, respectively. The use of tetraethoxysilane (TEOS) resulted in a pure hectorite and comprises the first report of the successful use of a tetraalkoxysilane silicon source for crystallizing hectorite from an aqueous solution.

Interfacial liquid-liquid ion transport is of crucial importance to biotechnology and industrial separation processes including nuclear elements and rare earths. A water-in-oil microemulsion is formulated here with density and dimensions amenable to atomistic molecular dynamics simulation, facilitating convergent theoretical and experimental approaches to elucidate interfacial ion transport mechanisms. Lutetium(III) cations are transported from the 5 nm diameter water pools into the surrounding oil using an extractant (a lipophilic ligand). Changes in ion coordination sphere and interactions between the interfacial components are studied using a combination of synchrotron X-ray scattering, spectroscopy, and atomistic molecular dynamics simulations. Contrary to existing hypotheses, our model system shows no evidence of interfacial extractant monolayers, but rather ions are exchanged through water channels that penetrate the surfactant monolayer and connect to the oil-based extractant. Our results highlight the dynamic nature of the oil-water interface and show that lipophilic ion shuttles need not form flat monolayer structures to facilitate ion transport across the liquid-liquid interface.

The synthesis and characterization of the Eu-encrypted heteropolyanion [ E U P~W~O O I 1 0 1 '~-are presented. X-ray absorption near-edge structure experiments were used to determine that Eu is trivalent in the anion. Optical spectra confirm this finding. The unusual cyclic voltammogram obtained for the Eu heteropolyanion is discussed in terms of the stability of Eu" under reducing conditions. Time delayed optical fluorescence data are only consistent with two structurally inequivalent Eu ions, both inside the heteropoly cavity. Lifetime measurements of the 5Do state indicate that the two structurally different Eu sites are not occupied in the same anion. In addition, from complementary measurements on samples made in D20, it is determined that there are three waters coordinated to Eu in one site and only two waters coordinated to Eu in the second site. 31P NMR and cyclic voltammetry data, obtained from samples with either one or two sites occupied, are indistinguishable. Possible models to explain the presence of two sites are discussed.

Bloch Decay Solid-State 13C NMR Spectroscopy of the Samarium Iodide Treated Argonne Premium Coals Sir: Discussions concerning the quantitative reliability of solid-state 13C NMR spectroscopy for fossil fuels have been underway for a decade. Although some workers in the field believe that the spectra accurately portray the carbon atom distribution in coal, many others do not.1 234567"8 The problem is complex because different investigators have usually studied different coals and have used different equipment and techniques to obtain the NMR data. We wish to report our results on the negative impact of radicals on the solid-state 13C NMR information for the Argonne Premium contract No. W-31-109-ENG-38.Registry No. Sml3, 32248-43-4.