bluuebunny/crossref_metadata_2025_split huggingface dataset:
Coordination Complexes of p-Hydroxybenzoate On Fe Oxides
Authors: Kung King-Hsi , McBride Murray B. 
Published: August 2006

AbstractAdsorption of p-hydroxybenzoate anion on synthetic Fe oxides, hydroxides, and oxyhydroxides (hereafter referred to as oxides) was measured at pH 5.5, and the organic-oxide interaction was characterized using diffuse-reflectance Fourier-transform infrared (DRIFT) spectroscopy. Surface complexes with ferrihydrite, hematite, goethite, and noncrystalline Fe oxide were investigated. Infrared (IR) spectra of the oxides after separation from p-hydroxybenzoate solutions showed the organic to be coordinated by an inner-sphere mechanism to the oxide surface through the carboxylate group. Bidentate binding of the carboxylate was identified to be the dominant type of complexation on the oxides. Although the IR study suggested that goethite formed the strongest surface iron-carboxylate bond, the total amount of organic adsorbed was the least on this oxide. This result suggested that bond energy was less important than adsorption site density in determining the amount of organic anion adsorption. Increasing ionic strength had little effect on adsorption by the noncrystalline Fe oxide, but dramatically decreased adsorption on hematite and goethite. This difference might have been due to anion competition for binding sites. At pH 5.5, the amount of organic adsorbed per unit weight of oxides (in 0.05 M NaClO4) followed the order: ferrihydrite > noncrystalline Fe oxide > hematite ≫ goethite. Adsorption per unit of surface area however, followed the order: ferrihydrite > hematite > noncrystalline Fe oxide ≫ goethite. The hematite adsorption reaction appeared to be driven by entropy, inasmuch as the reaction was endothermic. The difference among the oxides in surface reactivity toward p-hydroxybenzoate is hypothesized to have been caused by differences in both quantity and structural arrangement of reactive sites on the oxide surface.
Growth of Clay Minerals in Natural and Synthetic Glasses
Authors: Tazaki Kazue , Fyfe W. S. , van der Gaast S. J. 
Published: August 2006

AbstractHigh-resolution transmission electron microscopy (HRTEM) has shown regions of crystallites within noncrystalline matrices of three types of glass (volcanic glass, alkalic igneous glass, and synthetic, nuclear-waste-form glass) The volcanic glass fragments showed domains having 3-Å spacings. About 30% of the fragments of this glass showed localized lattice images, having spacings of 5, 7, 8, 10, 13, 14, 16, 19, and 20 Å, which also contain regular fringes having 3.3-Å separations. In the alkalic igneous glass fragments 3-Å domain structures were also noted as were localized lattice images having 7- and 12.5-Å spacings. Well-developed hollow spheres of primitive clays were present in both the volcanic and alkalic igneous glasses. Synthetic, nuclear-waste-foTm glass, fused at 1400°C and annealed at 550°C, showed locally ordered regions having 3.3-Å spacings. Low-angle X-ray powder diffraction showed major reflections at 8.5, 15–16, and 19 Å, which agree with some of the HRTEM measurements. These observations of domain structures, localized lattice images, primitive clays, and 14-Å clays in such noncrystalline glass matrices may contribute to an understanding of the growth of clay minerals. Such domains can apparently trigger the growth of clay products on the glass substrate.
D-Glucosamine Sorption on Cu(II)-Montmorillonite as the Protonated and Neutral Species
Authors: Pusino A. , Micera G. , Premoli A. , Gessa C. 
Published: August 2006

AbstractThe adsorption of D-glucosamine (2-amino-2-deoxy-D-gIucose) in the protonated or neutral form on homoionic Cu2+-bentonite was investigated by infrared (IR) and electron spin resonance (ESR) spectroscopy and chemical analyses of solution. The results show that the interaction of the glucosamine hydrochloride with the clay complexed a small fraction of interlayer metal ions with neutral amino sugar molecules. In contrast, the adsorption of free glucosamine was much more favorable and resulted in interlayer copper(II) complexes, mainly those in which the ligand was coordinated through amino and deprotonated hydroxyl groups. Part of the amino sugar molecules, however, were transformed into glucosammonium, replacing copper as the saturating ion.
Shape-Selective Sorbents Based on Clay Minerals: A Review
Authors: Barrer R. M. 
Published: August 2006

AbstractA review is presented of work carried out over the last 40 years on non-porous sorbents and on microporous shape-selective sorbents derived from palygorskite, smectite, and vermiculite. Among such materials four kinds of behavior were observed. In some systems uptake was restricted to external surfaces; in others, intercalation also occurred but only above threshold pressures. If the interlayer region was completely filled by long-chain organic cations, imbibition was possible, but in amounts which were very strongly dependent upon the cohesive energy density of the sorbate. Finally, in certain permanently expanded derivatives of layer silicates intercalation proceeded without any threshold pressure, just as in zeolites.In this latter group, micropores existed which sometimes resulted in shape-selective sorption and molecule sieving. The micropores in clay minerals were modified by varying the size and shape of the interlayer cations, their charge, and the charge density of the siliceous layers. The interplay of these factors was investigated and the micropore sorbents were shown to be highly effective in the separation of mixtures.
Deuterium Nuclear Magnetic Resonance Studies of Water Molecules Restrained by Their Proximity to a Clay Surface
Authors: Grandjean Jean , Laszlo Pierre 
Published: August 2006

AbstractObservation of quadrupolar splittings for 2H and 17O nuclei from D2O solvent molecules in suspensions of the Ecca Gum BP bentonite points unambiguously to the ordering of water molecules with respect to a static magnetic field. The application of the magnetic field apparently orients the clay platelets as tactoids. Some water molecules adhere to the platelets and are oriented. The magnitude of the quadrupolar splitting depends strongly on the nature of the interstitial cations. The sign of the splitting changes as the ratio of divalent to monovalent cation increases, reflecting a switch in the microdynamics of water molecules next to the plates. With the entry of divalent cations, the clay becomes more cohesive due to the vertical electrostatic attraction of the counterions to the charged plates. More of these hydrated divalent ions compared with monovalent ions condense onto the charged sheet, thereby increasing metal coordination to those water molecules in contact with the clay surface. The dominant reorientation mode of the water molecules switches from rotation of water molecules around hydrogen bonds to the charged sheets to rotation around the electrostatic bond to the divalent metal cation. The effect is spectacular and important in understanding the chemical properties of cation-exchanged montmorillonites.
Distribution and Origin of Analcime in Marginal Lacustrine Mudstones of the Green River Formation, South-Central Uinta Basin, Utah
Authors: Remy Robert R. , Ferrell Ray E. 
Published: August 2006

AbstractX-Ray powder diffraction and thin section analyses indicate that marginal lacustrine mudstones of the Green River Formation in the south-central Uinta basin, Utah, contain abundant analcime. The analcime has a low Si/Al ratio (<2.31) and occurs as very fine grained disseminated crystals and, to a lesser extent, as coarser-grained pore-filling cement. Analcime-rich mudstones and associated sandstones, siltstones, and carbonates lack volcanic detritus and zeolites other than analcime, thus making it difficult to support the concept that the analcime formed from precursor zeolites derived from volcanic glass altered in saline, alkaline-lake water. Abundant dolomite, syneresis cracks, and the absence of freshwater pelecypods and gastropods suggest that the lake (Lake Uinta) was moderately saline and alkaline. The restricted illite-illite/smectite clay mineral suite in the analcime-rich mudstones suggests that detrital clays significantly altered in a moderately saline and alkaline environment, thereby providing a source of Si and Al for the formation of analcime.Red mudstones contain twice as much analcime as green mudstones (14 vs. 7 wt. %). Green mudstones have a day mineral suite consisting of illite (44 wt. %), mixed-layer illite/smectite (35 wt. %), smectite (12 wt. %), and minor kaolinite (4 wt. %) and chlorite (5 wt. %), whereas red mudstones have a more restricted day mineral suite consisting ofillite (68 wt. %) and mixed-layer illite/smectite (26 wt. %) with very minor smectite, chlorite, and kaolinite. Periodic minor fluctuations in lake level probably exposed large areas of shallow lacustrine-interdistributary green mud. Evaporative pumping on the exposed mudflats concentrated the moderately saline and alkaline-lake water, thereby producing Na-rich brines that enhanced the formation of analcime by accelerating the alteration of detrital clays and, perhaps, other minerals. Oxidation of iron from altered iron-bearing minerals stained the analcime-rich mud red with iron hydroxide or oxide (perhaps hematite). The overall reaction from green to red mud (mudstones) was probably: detrital phyllosilicates + Na-brine + iron-bearing minerals + oxygen → analcime + iron hydroxide or iron oxide.
Effects of Dry Grinding and Leaching on the Crystal Structure of Chrysotile
Authors: Suquet Helèné 
Published: August 2006

AbstractThe structural damage produced by dry grinding and acid leaching of chrysotile was studied by transmission and scanning electron microscopy, infrared spectroscopy, X-ray powder diffraction, and thermogravimetric analysis. Severe dry grinding converted the chrysotile fibers into fragments having strong potential basic reaction sites. These sites were immediately neutralized by molecules present in the atmosphere (e.g., H2O, CO2). Acid leaching transformed the chrysotile fibers into very porous, non-crystalline silica, which was easily fractured into short fragments. The damage produced in the chrysotile structure by grinding or leaching was assessed by monitoring the intensity of various infrared absorption bands.
Influence of Mn2+ and pH on the Formation of Iron Oxides from Ferrous Chloride and Ferrous Sulfate Solutions
Authors: Krishnamurti G. S. R. , Huang P. M. 
Published: August 2006

AbstractThe influence of Mn2+ on the formation of Fe oxides at pHs of 6.0 and 8.0 and varying Mn/Fe molar ratios (0, 0.1, 1.0, and 10.0) in the FeCl2-NH4OH and FeSO4-NH4OH systems was studied by X-ray powder diffraction (XRD), infrared absorption, transmission electron microscopic, and chemical analyses. In the absence of Mn2+, lepidocrocite (γ-FeOOH) and maghemite (γ-Fe2O3) were the crystalline species formed at pHs of 6.0 and 8.0, respectively, in the FeCl2 system, whereas lepidocrocite and goethite (α-FeOOH) and lepidocrocite were the crystalline species formed at pHs of 6.0 and 8.0, respectively, in the FeSO4 system. The amount of Mn coprecipitated with Fe (as much as 8.1 mole % in the FeCl2 system and 15.0 mole % in the FeSO4 system) increased as the initial solution Mn/Fe molar ratio increased from 0 to 10.0, resulting in the perturbation of the crystallization processes of the hydrolytic products of Fe formed. At pH 6.0, the perturbation led to the formation of poorly ordered lepidocrocite, as reflected in the increasing broadening of its characteristic peaks in the XRD patterns. At pH 8.0, poorly ordered iepidocrocite and a honessite-like mineral (Mn-Fe-SO4-H2O) formed in the FeCl2 and FeSO4 systems, respectively.
Infrared Study of Structural OH in Kaolinite, Dickite, Nacrite, and Poorly Crystalline Kaolinite at 5 to 600 K
Authors: Prost R. , Dameme A. , Huard E. , Driard J. , Leydecker J. P. 
Published: August 2006

AbstractThe resolution of the infrared spectra of structural OH in kaolin-group minerals increases with decreasing temperature. Poorly crystalline kaolinite gives typical infrared spectra, which suggest the existence of kaolinite-, dickite-, and nacrite-like configurations. The relative amount dickite- and nacrite-like configurations compared with kaolinite-like configurations increases with decreasing crystallinity. Low-temperature infrared spectroscopy is a more sensitive means of estimating the degree of order of poorly crystalline kaolinite than is X-ray powder diffraction.
Dioxon Sorption by Hydroxy-Aluminum-Treated Clays
Authors: Nolan Tim , Srinivasan Keeran R. , Fogler H. Scott 
Published: August 2006

AbstractThe treatment of smectites with a hydroxy-Al polymer produced chemically modified clays that had much greater affinities for chlorinated dioxins and biphenyls than untreated clays. For hydroxy-Al-treated kaolinite, the high affinity for chlorinated dioxins is thought to have arisen from an interaction between the hydroxy-Al polymer bound to the clay and the chlorinated dioxin in solution. Thus, the adsorption of dioxins from aqueous solution by hydroxy-Al-treated clays is similar to the adsorption of reactants from the gas phase by metals supported on mineral oxides during catalysis. In both systems, the essentially inert mineral oxide support effectively disperses the active adsorptive agent. At the concentrations of octachlorodioxin used in this study (≤5 ppb), hydroxy-Al-montmorillonite had a distribution coefficient of 90,000 (ml/g), corresponding to about 95% removal efficiency of the dioxin from solution per batch. For hexachlorohiphenyl, the distribution coefficient was 30,000 (ml/g), and the removal efficiency was 85%.
Zeolites in Pre-Caldera Pyroclastic Rocks of the Santorini Volcano, Aegean Sea, Greece
Authors: Tsolis-Katagas Panayota , Katagas Christos 
Published: August 2006

AbstractThe vitric matrix of pre-caldera acid tuff and tuff breccia of the Santorini volcano, Aegean Sea, Greece has been generally replaced by one or more of the following authigenic minerals: K-rich and (K,Ca)-rich clinoptilolite, mordenite, opal-CT, and clay minerals. Halite is also present in some samples. Initial compositional inhomogeneities between the dacitic blocks in tuff breccia and tuff seem to have controlled the type of K-rich heulandite-group zeolite that formed. Mordenite postdates the heulandite-group zeolites and opal-CT. Some mordenite has replaced the rims of glass shards. The alteration minerals are not related to vertical or lateral zonation, and the irregular distribution of their assemblages is attributed to variations in heat flow, ionic activity in interstitial waters, and permeability. The pyroclastic rocks were in a region of active heat flow during and after their emplacement. The formation of authigenic silicates may have led to the sealing of open spaces and fractures, imposing barriers to permeability and subdividing the original open system into smaller closed systems. As alteration progressed, some of the trapped water in each individual domain was consumed in hydration reactions. Salts could have been concentrated by such a process, and halite probably precipitated from solutions of appropriate composition in the individual closed systems.
Neutron Diffraction Study of a One-Layer Monoclinic Chlorite
Authors: Joswig Werner , Fuess Hartmut , Mason Sax A. 
Published: August 2006

AbstractA monoclinic IIb-2 clinochlore from the Achmatov mine, Ural Mountains, U.S.S.R., was investigated by neutron diffraction. The formula, based on electron microprobe and wet chemical analyses, is (Mg4.54Al0.97Fe2+0.28 Fe3+0.18Mn0.01)(Si2.85Al1.15)O10(OH)8. A refinement based on 512 unique reflections converged in space group C2/m to a final R =.066. Cation disorder was found in the two octahedral positions of the 2:1 layer, whereas partial Mg and Al ordering occurs in the interlayer sheet. The two hydroxyl dipoles are roughly perpendicular to the interlayer sheet, forming weak to medium hydrogen bonds with O…O distances of 2.859 and 2.881 Å. The OH-dipole of the 2:1 layer is perpendicular to the (001) plane.
Weathering of Hornblende to Ferruginous Products by a Dissolution-Reprecipitation Mechanism: Petrography and Stoichiometry
Authors: Velbel Michael Anthony 
Published: August 2006

AbstractHornblende of the Carrol Knob mafic complex (southern Blue Ridge Mountains, North Carolina) has weathered under humid, temperate conditions. Hornblende weathering appears to have been a dissolution-reprecipitation reaction, in which hornblende dissolved stoichiometrically, and the ferruginous and aluminous weathering products (goethite, gibbsite, and kaolinite) precipitated from solution (neoformation). During the earliest stage of alteration, ferruginous weathering products formed as linings of fractures within and around crystals and cleavage fragments of hornblende. Side-by-side coalescence of lenticular etch pits during more advanced weathering produced characteristic “denticulated” terminations on hornblende remnants in dissolution cavities bounded by ferruginous boxworks. Dissolution cavities are devoid of weathering products. Small “pendants” of ferruginous material project from the boxwork into void spaces. Because these products are separated from the hornblende remnants by void space, they must have been produced by dissolution-reprecipitation reactions. Complete removal of the parent hornblende left a ferruginous microboxwork or “negative pseudomorph.” Only Al and Fe were conserved over microscopic distances; alkali and alkaline-earth elements were stoichiometrically removed from the weathering microenvironment during the weathering process.
Pyrogallol Transformations as Catalyzed by Nontronite, Bentonite, and Kaolinite
Authors: Wang M. C. , Huang P. M. 
Published: August 2006

AbstractThe catalytic power of Ca-nontronite, Ca-bentonite, and Ca-kaolinite in promoting the abiotic ring cleavage of pyrogallol (1,2,3-trihydroxybenzene) and the associated formation of humic polymers was studied in systems free of microbial activity. The presence of Ca-kaolinite and especially Ca-nontronite in the pyrogallol solutions at pH 6.00 greatly enhanced the absorbance at both 472 and 664 nm of the supernatants. At an initial pH of 6.00 and at the end of a 90-hr reaction period, the amounts of CO2 released from the ring cleavage of pyrogallol and the yields of the resultant humic polymers formed in the reaction systems followed the same sequence: Ca-nontronite > Ca-kaolinite > Ca-bentonite. The data indicate that the catalytic power of Fe(III) on the edges and in the structure of nontronite was substantially greater than that of Al on the edges of kaolinite and montmorillonite and of a small amount of Fe(III) in the structure of montmorillonite in promoting the reactions. The infrared and electron spin resonance spectra and the solid-state, cross-polarization magic-angle-spinning 13C nuclear magnetic resonance spectra of humic polymers formed in the reaction systems resembled those of natural humic substances.
Effects of Iron Oxidation State on the Specific Surface Area of Nontronite
Authors: Lear Paul R. , Stucki Joseph W. 
Published: August 2006

AbstractThe effect of Fe oxidation state on the specific surface area, Sm, of nontronite was studied using the <2-µm, Na+-saturated fraction of the SWa-1 and Garfield nontronite reference clays. The reduction of structural Fe3+ in the octahedral sheet of the nontronite decreased Sm as measured by the adsorption of 2-ethoxyethanol (ethylene glycol-monoethyl ether, EGME). The swellability in water of the nontronite also decreased during reduction. The amount of nonexchangeable Na+, on the other hand, increased with increasing Fe2+ content and was highly correlated with EGME adsorption (r = -.985). The relationship between Sm and Fe2+ was attributed to the collapse of partially or fully expanded layers to unexpanded layers.
Interaction of Diclofop and Diclofop-Methyl with Al3+-, Fe3+-, and Cu2+-Saturated Montmorillonite
Authors: Pusino A. , Micera G. , Gessa C. , Petretto S. 
Published: August 2006

AbstractThe adsorption from chloroform solution of the herbicide diclofop, (RS)-2-(4-(2,4-dichlorophenoxy)phenoxy)propionic acid, and its methyl ester diclofop-methyl on Cu2+-, Al3+-, and Fe3+-exchanged bentonite samples was investigated. For comparison, the complexes formed by diclofop were synthesized and studied. Diclofop adsorbed on the clays and formed carboxylate bonds to the interlayer ions. Diclofop-methyl also adsorbed, but its interaction involved the formation of hydrogen bonds with water molecules in the interlayer. Traces of diclofop were observed in both the solution and the clays after adsorption of diclofop-methyl, indicating that some hydrolysis of the ester to the corresponding acid occurred. Thus, pesticides forming neutral complexes with interlayer cations in montmorillonite in soils may be extractable by solvents and therefore released into the environment.
Effects of Humic Acid on the Crystallization of Aluminum Hydroxides
Authors: Singer A. , Huang P. M. 
Published: August 2006

AbstractThe effects of humic acid (HA) on the crystallization of precipitation products of Al under mildly acidic to alkaline conditions were investigated. The extent of Al precipitation substantially decreased with increasing HA concentration (0 to 75 µg/ml) in the pH range 6 to 10 during the 80-day aging period. The X-ray powder diffraction (XRD) data show that, at pH 6.0, the amount of pseudoboehmite formed in the systems decreased with the increasing concentration of HA present. The proportion of Al hydroxide polymorphs (gibbsite and bayerite) was greatly influenced by the amounts of HA present in the systems. At pH 6.0 and HA concentration of 37.5 µg/ml, all the precipitation products of Al were noncrystalline. At pH 8.0 and a HA concentration of 12.5 µg/ml, the formation of gibbsite and bayerite was completely inhibited and only pseudoboehmite was evident in the XRD patterns. Further increase in HA concentration (25–75 µg/ml HA) at pH 8.0 resulted in no precipitation of Al, and only a broad peak at ∼3.3 Å, characteristic of HA, was observed. The XRD patterns of the precipitates of Al formed in the absence of HA at pH 10.0 showed the characteristic peaks of bayerite. At pH 10.0, the precipitation products of Al formed even at the HA concentration of 2.5 µg/ml yielded no XRD peaks. Infrared absorption spectra and transmission electron micrographs of the precipitation products of Al formed in the systems studied substantiate the findings obtained by XRD. The data obtained in this study indicate that HA affects the formation of Al hydroxide polymorphs, pseudoboehmites and short-range ordered mineral colloids.
Structural Fluorine in Sepiolite
Authors: Santaren Julio , Sanz Jesus , Ruiz-Hitzky Eduardo 
Published: August 2006

AbstractSepiolite from Vallecas-Vicálvaro, Spain, contains 1.3% fluorine. Laser microprobe mass spectrometry of this sepiolite suggests the presence of fragments of (SiO2)nOMgF and (SiO2)nOMgOH, which are typical of the sepiolite structure. During thermal dehydroxylation, the fluorine in this sepiolite is removed simultaneously with OH groups at about 750°C. Nuclear magnetic resonance spectroscopy (NMR) of 19F indicates that the fluorine is located in the interior of the sepiolite structure, probably substituting for OH groups, and is homogeneously distributed. In the Vallecas-Vicálvaro sepiolite, about one of every four OH groups bound to Mg2+ is substituted by fluorine. The kinetics of extraction of Mg2+ and F- ions by acid treatment (1 N HCl) shows a more rapid extraction of Mg2+, with a monotonous decrease of the Mg/F ratio as the extent of extraction increases. These results support the internal location of the fluorine, as suggested by the NMR data.