bluuebunny/crossref_metadata_2025 huggingface dataset:
Asymmetric Zonation of a Thick Ordovician K-Bentonite Bed at Kinnekulle, Sweden
Authors: Brusewitz Ann Marie
Published: August 2006

The clay fraction of a ∼2-m-thick K-bentonite at Kinnekulle in southwestern Sweden has been studied by X-ray powder diffraction, chemical analyses, and cation-exchange capacity determinations. Previous investigations of the upper half of this bed (B-bed) have shown the clay mineral to be illite/smectite (I/S), containing about 50% illite layers at the center of the bed and 65% illite layers at the upper contact. New data on six samples from the lower part of the bed show no zonation, the I/S containing about 50% illite layers in all samples. The bentonite occurs in limestones and shales overlying a 40-m-thick limestone bed and is overlain by limestones, marls, and shales (∼90 m), which in turn are overlain by a 40-m-thick diabase. The limestones are silicified in contact with the bentonite, particularly beneath the B-bed. The increased K content towards the upper contact may therefore have resulted from diffusion of K-bearing solutions from overlying shales, a process that was impeded in the lower part of the bed, probably by the silicification.
Interaction of Fluazifop with Al-, Fe3+-, and Cu2+-Saturated Montmorillonite
Authors: Micera G. , Pusino A. , Gessa C. , Petretto S.
Published: August 2006

The adsorption of the pesticide Fluazifop, (RS)-2-[4-[[(5-trinuoromethyl)-2-pyridin-yl]oxy]phenoxy] propanoic acid, on homoionic Cu2+-, Fe3+-, and Al-bentonites was investigated by infrared and electron spin resonance spectroscopy. For comparison, the binary complexes of the acid containing the above ions were prepared and characterized. On the whole, the results show that the interaction of the acid with the clay may have involved both the protonation of the pyridine nitrogen atom, due to a proton transfer from the acid metal-bound water, and the formation of direct bonds between the carboxylate groups and the exchange cations. The extent of these interactions was dependent on the nature of the metal ions, the Cu ions being more effective in producing CHCl3-extractable neutral carboxylate complexes, while Al and Fe favored the formation of species bearing protonated nitrogen atoms and un-dissociated carboxyl groups.
Infrared Studies of Surface Acidity and Reversible Folding in Palygorskite
Authors: Blanco C. , Herrero J. , Mendioroz S. , Pajares J. A.
Published: August 2006

The infrared absorption spectra of a palygorskite sample from Cáceres, Spain, showed two previously unreported bands in the OH-stretching region at 3420–3440 and 3220–3230 cm−1 after evacuation at 90°–230°C. These bands, which reached maximum intensity after the sample was heated at 150°C, were assigned to OH in the
$$\begin{array}{*{20}{c}} H \\: \\ {Si - O - Si\,and\,} \\ \end{array}\begin{array}{*{20}{c}} H \\: \\ {Si - O - A1} \\ \end{array}$$ groups, respectively. To characterize the nature of these OH groups, pyridine was adsorbed on the sample. The resultant spectra suggest that at 150°C the palygorskite folded and OH groups protonated, resulting in the formation of a deformed pyridinium ion between 150° and 290°C. A high concentration of thermally stable Lewis-acid sites on the surface of the palygorskite was also noted.
Acid Dissolution of Akaganiéite and Lepidocrocite: The Effect on Crystal Morphology
Authors: Cornell R. M. , Giovanoli R.
Published: August 2006

The rate of dissolution of akaganéite in HCl increased with time over the bulk of the reaction leading to a sigmoid dissolution vs. time curve. The bulk of the dissolution of lepidocrocite could be described by the cube root law. Transmission electron microscopy examination of partly dissolved crystals of akaganéite showed that acid attack proceeded mainly along the [001] direction. Initially, the tapered ends of the crystals became squared, and as dissolution continued the lengths of the crystals decreased steadily. At the same time, the crystals were gradually hollowed out. Acid attack was most pronounced at the edges of the crystals of lepidocrocite and appeared to involve a disruption of the hydrogen bonds that link the sheets of octahedra making up the structure. Defects also acted as sites for preferential acid attack. Dissolution of multi-domainic crystals involved preferential attack along the domain boundaries, as well as at the edges of the crystals. Single-domain crystals were well developed, but appeared to contain internal imperfections, which promoted the formation of holes on the otherwise unreactive (010) faces.
Reactions of Polynuclear Hydroxyaluminum Cations with Montmorillonite and the Formation of A 28-Å Pillared Complex
Authors: Singh S. Shah , Kodama H.
Published: August 2006

Polynuclear hydroxy-Al cations were prepared by partially neutralizing dilute solutions of aluminum chloride. These cations were introduced in the interlayer space of montmorillonite by cation exchange, which formed heat-stable pillars between the silicate layers. Polynuclear hydroxy-Al was preferentially adsorbed on montmorillonite compared with monomer-Al; the maximum amount adsorbed was ∼400 meq/100 g of montmorillonite. Of this amount 320 meq was non-exchangeable. The 001 X-ray powder diffraction reflection of the polynuclear hydroxy-Al-montmorillonite complex was at 27 Å, with four additional higher-order basal reflections, giving an average d(001) value of 28.4 Å. This complex was thermally stable to 700°C. An analysis of the basal reflections by the Fourier transform method indicated that the 28-Å complex had a relatively regular interstratified structure of 9.6- and 18.9-Å component layers with a mixing ratio of 0.46:0.54. This ratio implies that the hydroxy-Al pillars occupied every second layer. Considering the relatively small amount of Al adsorbed and the thermally stable nature of the structure, the hydroxy-Al pillars must have been sparsely but homogeneously distributed in the interlayer space.
Effect of Magnesium on the Hydraulic Conductivity of Na-Smectite-Sand Mixtures
Authors: Shainberg I. , Alperovitch N. , Keren R.
Published: August 2006

Changes in hydraulic conductivity (HC) and clay dispersion of smectite-sand mixtures as a function of exchangeable Na in Na-Ca and Na-Mg systems were measured. The charge density on the smectites had no effect on Na-Ca and Na-Mg equilibrium, and the affinity of the clays for Na was similar in both systems. A decrease in HC at 0.01 M concentration was found to be due to clay swelling. Mg was found to be less effective than Ca in preventing the breakdown of the packets by low concentrations of exchangeable Na, and Na-Mg-smectite swelled more than Na-Ca-smectites.

Na-Mg-clay particles dispersed more readily than Na-Ca-clay particles when the mixtures were leached with distilled water; however, if the electrolyte concentration in the clay-sand mixture was controlled by the leaching solutions, no difference between the Na-Mg- and Na-Ca-clays was noted. Thus, the effect of Mg on clay mixtures leached with distilled water was apparently due to the effect of Mg on the hydrolysis of the clays. Increase in charge density increased the stability of the R2+ clay packets, and higher concentrations of Na were needed to break the packets. Mg was less effective than Ca in stabilizing the packets, and lower concentrations of Na were needed to break the Mg-packets.
Stacking Order in a 14.30-Å Mg-Vermiculite
Authors: de la Calle Cristina , Suquet Hélène , Pons Charles-Henri
Published: August 2006

The stacking order of a 14.30-Å Mg-vermiculite from Santa-Olalla, Spain, has been determined from Weissenberg photographs. The results prove that the Mg-vermiculite structure is not a 2-layer polytype structure, but a semi-ordered one. Because the structure is semi-ordered, its resolution needed a dual approach: (1) a direct approach using an electron density projection along the y axis in conjunction with a one-dimensional electron-density projection onto the z axis; and (2) an indirect approach in which the observed intensities along the (0,k) and (1,k) reciprocal rods were compared to the calculated intensities given by model defect structures. The semi-ordered structure of the Mg-vermiculite results from ±b/3 shifts in the stacking of the silicate layers. The shifts are randomly either along +b or -b.
Analytical Electron Microscopy and the Problem of Potassium Diffusion
Authors: van der Pluijm Ben A. , Lee Jung Hoo , Peacor Donald R.
Published: August 2006

Diffusion of K during analytical electron microscopy (AEM) results in anomalously low count rates for this element. As the analysis area and specimen thickness decrease, count rates become disproportionally lower. Adularia and muscovite show different diffusion profiles during AEM; for muscovite a strong dependence of diffusion on crystallographic orientation has been observed. Conditions giving rise to reliable chemical data by AEM are the use of a wide scanning area (>800 × 800 Å) and/or large beam size to reduce the effect of diffusion of alkali elements, a specimen thickness greater than about 1000 Å, constant instrument operating conditions, and the use of a homogeneous, well-characterized standard sample. The optimum thickness range was obtained by determining the element intensity ratio vs. thickness curve for given operating conditions. The standard and unknown should have a similar crystal structure and, especially for strongly anisotropic minerals such as phyllosilicates, a similar crystallographic orientation with respect to the electron beam.
Hydrothermal and Supergene Alterations in the Granitic Cupola of Montebras, Creuse, France
Authors: Dudoignon P. , Beaufort D. , Meunier A.
Published: August 2006

A mineralogical investigation of the highly kaolinized Chanon granite and albite-muscovite granite of the Montebras cupola, Creuse, France, indicates that the magmatic stage was followed by two hydrothermal events related to successive cooling stages and by late weathering. The hydrothermal alteration was accompanied first by greisen formation and then a broad kaolinization process, which pervasively affected the granitic bodies. In the Chanon granite, the greisens are characterized by a trilithionite-lepidolite-quartz-tourmaline assemblage and are surrounded by concentric alteration zones. From the greisen to the fresh granite three zones were distinguished: (1) a zone characterized by secondary brown biotite (<400°C), (2) a zone characterized by secondary green biotite and phengite (300–350°C), and (3) a zone characterized by the presence of corrensite (180°–200°C) located around greisen veinlets. In the albite-muscovite granite the greisen is composed of lepidolite and quartz. This mineral assemblage was followed locally by Li-tosudite crystallization. During the second hydrothermal event (<100°C) an assemblage of kaolinite, mixed-layer illite/smectite (I/S), and illite formed pervasively and in crack fillings; the smectite layers of the US are potassic. Weathering produced Fe oxide and kaolinite. This kind of alteration developed mainly in the overlying Chanon granite. Here, Ca-Mg-montmorillonite formed in subvertical cracks, which transect the two granitic bodies, and hydrothermal I/S was obliterated by Ca-Mg-montmorillonite.

The hydrothermal parageneses were apparently controlled by magmatic albitization and the bulk chemistry of the two granitic bodies. The albitization, the formation of large micaceous greisens, and the successive recrystallizations of biotite (which was the most susceptible phase to alteration) provide information on the temperature range and chemical mobility during successive cooling stages. Si and Mg activities increased as the temperature of alteration decreased, and secondary Mg-biotite and Mg-phengite crystallized as long as the K activity was sufficient. The crystallizations of secondary biotite and phengite were followed by the crystallization of I/S during stages of low K activity. Secondary hydrothermal phases in the Chanon granite contain substantial Fe and Mg. Secondary hydrothermal phases in the albite-muscovite granite contain only small amounts of Fe and Mg, suggesting a lack of chemical exchange between the enclosing Chanon granite and the albite-muscovite granite, which is depleted in Fe-Mg-rich primary phases, such as biotite.
Weathering of Iron-Bearing Minerals in Soils and Saprolite on the North Carolina Blue Ridge Front: II. Clay Mineralogy
Authors: Graham R. C. , Weed S. B. , Bowen L. H. , Amarasiriwardena D. D. , Buol S. W.
Published: August 2006

The mineralogy of the clay fraction was studied for soils and saprolite on two Blue Ridge Front mountain slopes. The clay fraction contained the weathering products of primary minerals in the mica gneiss and schist parent rocks. Gibbsite is most abundant in the saprolite and residual soil horizons, where only chemical weathering has been operable. In colluvial soil horizons, where both physical and chemical weathering have occurred, the clay fraction consists largely of comminuted primary phyllosilicates —muscovite, chlorite, and possibly biotite—and their weathering products: vermiculite, interstratified biotite/vermiculite (B/V), and kaolinite. The clay-size chlorite contains Fe2+ as indicated by Mössbauer spectroscopy, and is more resistant to weathering than biotite. The vermiculite and B/V, both weathering products of biotite, contain Fe3+. Vermiculite in colluvial soils and, especially, surface horizons is weakly hydroxy-interlayered. The kaolinite in the clay fraction resulted at least partly from the comminution of kaolinized biotite in coarser fractions.

The hematite content ranged from 0 to 8% of the clay fraction and strongly correlates (r =.95) with dry clay redness, as measured by the redness rating: RR = (10 - YR hue) × (chroma) ÷ (value). The hematite is largely a product of the weathering of almandine; thus, the soil redness is dependent on the amount of almandine in the parent materials and its degree of weathering in the soils. Goethite (13–22% of the clay fraction) imparts a yellow-brown hue to soils derived from almandine-free parent rocks. The release of Fe in relatively low concentrations during the weathering of Fe-bearing primary minerals, particularly biotite, appears to have promoted the formation of goethite.
Diagenetic Alteration of Perlite in the Guryongpo Area, Republic of Korea
Authors: Noh Jin Hwan , Boles James R.
Published: August 2006

Perlite, which occurs at the contacts between dacite and lacustrine tuffs of Miocene age in the Guryongpo area, Korea, has undergone more sluggish and incomplete diagenetic alteration than the surrounding zeolitic tuffs. Alkali-clinoptilolite, mordenite, smectite, K-rich gel-like glass, low-cristobalite, and K-feldspar are characteristic diagenetic phases in the altered perlite.

Hydration of the glass to form perlite resulted in the expulsion of cations, mainly Na, from the glass into the pore fluid and in the relative enrichment of K in the perlite. Hydration of the glass also resulted in increased alkalinity of the pore fluid, which, in turn, affected the nature and behavior of subsequent glass dissolution. Textural observations and chemical data on the early diagenetic phases indicate a sequence of incongruent dissolution reactions, which depended on silica activity and alkalinity of the ambient pore fluid: Reaction (1) 12.5 perlitic glass + 3.88 K+ + 0.65 H+ + 15.4 H20 = smectite + 9.5 gellike glass + 4.03 Na+ + 0.25 Ca2+ + 10.55 H4SiO4 released Ca and silica which were consumed by reaction (2) perlitic glass + 0.1 Ca2+ + 0.1 H4SiO4 + 0.1 H+ + H20 = clinoptilolite + 0.1 K+ + 0.2 Na+. The paragenesis from glass via smectite to alkali zeolites in most glass-bearing rocks may be explained by a sequence of such dissolution reactions. Still later reactions involved the transition from less-silicic clinoptilolite to an assemblage of silicic Na-clinoptilolite + mordenite and the crystallization of the gel-like glass to K-feldspar.
Oxidation State of Iron in Glauconite from Oxidized and Reduced Zones of Soil-Geologic Columns
Authors: Fanning D. S. , Rabenhorst M. C. , May Leopold , Wagner D. P.
Published: August 2006

Glauconite from the oxidized and reduced zones of soil-geologic columns at two Coastal Plain sites, one in Maryland and one in New Jersey, was examined by Mössbauer spectroscopy. The data indicate that glauconite in the reduced zones had a higher proportion of its structural iron in the ferrous, as opposed to the ferric state. The Fe2+/Fe3+ ratio ranged from 0 to 0.2 for the glauconite from the oxidized zone and was about 0.35 for the glauconite in the reduced zones. Despite the presence of pyrite in the reduced zone, which might be expected to make ferric iron unstable because of the presence of sulfide S, about 75% of the Fe in the glauconite in the reduced zone was in the ferric state. Thin section analysis showed some glauconite in the reduced zones to be intimately associated with pyrite and some aggregates of fine pyrite crystals were locally present in cracks in glauconite pellets. In the oxidized zones, pyrite was absent and the glauconite was more yellow under plane-polarized light, as opposed to more green for the glauconite in the reduced zones. These data indicate that reports of studies of glauconite should stipulate whether samples are from the oxidized or reduced zone of soil-geologic columns.
Resolution of the Polytype Structure of Some Illitic Clay Minerals that Appear to Be 1Md
Authors: Austin G. S. , Glass H. D. , Hughes R. E.
Published: August 2006

Illite/smectite (I/S) and illite samples that appear to be 1Md polytypes on the basis of the lack of diagnostic reflections can be resolved as partly either 1M or 2M1 or both by either vapor solvation in ethylene glycol for 40 to 80 hr at ambient temperatures or for 4 hr at 80°C, or by heating to 375°C for 2 hr. If samples are so treated, a distinct narrowing of the I/S 003/005 peak occurs and diagnostic hkl reflections are revealed. These treatments, however, do not seem to affect diagnostic polytypic peak intensities, but rather the adjacent background. We propose that the 1Md term be restricted to its original definition—the disordered polytype associated with only the 1M ordered polytype. For illites in which disorder exists with a mixture of polytypes, the generic term Ad (disordered group A micas) should be used. Correct polytype determination of illitic material is significant because it reveals thermal history of the sediments and allows greater understanding of the depositional and diagenetic history of sedimentary basins.
Aqueous-Chemical Control of the Tetrahedral-Aluminum Content Of Quartz, Halloysite, and other Low-Temperature Silicates
Authors: Merino Enrique , Harvey Colin , Murray H. H.
Published: August 2006

Aqueous Al passes from octahedral to tetrahedral coordination over a narrow pH interval, or threshold. This interval is 5.5–6.5 at 25°C and shifts to lower pH as temperature increases. The concentration of aqueous tetrahedrally coordinated Al is a quasi-step function of the solution pH, and, by the mass-action law, so should be the amount of tetrahedral Al incorporated by a silicate that crystallizes from the aqueous solution. Qualitative support for this prediction (which applies to quartz, opal-CT, kaolin-group minerals, pyrophyllite, micas, chlorites, and other low-temperature silicates) comes from the very topology of equilibrium activity diagrams and from several pairs of associated waters and authigenic silicates from weathering, hydrothermal, and diagenetic environments. The uptake of tetrahedral Al also depends on the aqueous concentrations of monovalent cations and silica, and on the mineral's structural constraints.

Solid solution of tetrahedral Al in halloysite in turn produces the characteristic bent or tubular crystals of this mineral. This genetic link between aqueous chemistry (mainly pH), tetrahedral-Al uptake by a low-temperature silicate, and the mineral's crystal morphology may operate also in other silicates.
Mn-Substituted Goethite and Fe-Substituted Groutite Synthesized At Acid pH1
Authors: Ebinger M. H. , Schulze D. G.
Published: August 2006

Mn-substituted iron oxides were synthesized by coprecipitating Fe(NO3)3 and Mn(SO4) solutions with NH4OH, adjusting the suspensions to pH 4 or 6, and then keeping the suspensions at 55°C for 62 days. The Mn mole fraction of the final products ranged from 0 to 0.3. X-ray powder diffraction patterns showed that goethite and hematite formed in each Fe-containing system. Groutite formed in systems having initial Mn mole fractions ≥0.35. Only manganite and hausmannite formed in the pure Mn systems. The oxalate-soluble Fe in the samples increased as the Mn mole fraction increased and was slightly larger for the pH 6 series.

For samples that contained the largest Mn mole fraction, the b and c dimensions of the goethite unit cell were shifted toward those of groutite, and the b and c dimensions of the groutite unit cell were shifted toward those of goethite. Assuming the Vegard rule holds for the unit-cell c dimension, the goethite accommodated a maximum Mn mole fraction of 0.34, and the groutite accommodated a maximum Fe mole fraction of 0.31. The unit-cell dimensions of hematite did not vary systematically with the mole fraction of Mn in solution, probably because little Mn substituted into the hematite structure.
Adsorption and Desorption of N-Methyl 8-Hydroxy Quinoline Methyl Sulfate on Smectite and the Potential Use of The Clay-Organic Product as an Ultraviolet Radiation Collector
Authors: Vicente M. A. , Sánchez-Camazano M. , Sánchez-Martín M. J. , del Arco M. , Martín C. , Rives V. , Vicente-Hernández J.
Published: August 2006

The interaction between N-methyl 8-hydroxy quinoline methyl sulfate, a drug that absorbs erymathogenic near-ultraviolet radiation, and smectite was studied by X-ray powder diffraction (XRD) and adsorption and desorption techniques. From the adsorption studies, (1) the amount of the drug adsorbed by Na-smectite increased with the pH of the solution to pH 6.5 and then decreased as the pH was further increased; (2) the maximum amount adsorbed at pH 6.5 was 102 meq/100 g of clay; and (3) the maximum amount of drug adsorbed, according to the adsorption isotherms at pH 4, was close to the cation-exchange capacity of the smectite (80 meq/100 g). The XRD studies showed that the drug molecules were adsorbed in the interlayer space of smectite and that cation exchange was the chief mechanism responsible for these interactions. The results of the adsorption-desorption cycles of the drug by smectite showed that this clay is a good support for this compound. In addition, an alternative method was developed to obtain the intercalation compound to avoid the standard method of exchange by impregnation. The method consisted of grinding a mixture of the drug with the clay. The characteristics of the complex thus formed were similar to those of the complex formed by exchange at pH 4 to 7.

To gain insight into the pharmacological properties of the intercalation compound studied, its capacity for absorption of visible and near-ultraviolet light was investigated. The diffuse reflectance spectrum of the complex showed intense absorption bands, absent or weak in the spectra of the pure drug or the untreated clay, at 250, 290, and ~390 nm.
Clay Mineral Segregation by Flocculation in the Porters Creek Formation
Authors: Thomas Andrew R. , Murray Haydn H.
Published: August 2006

The Porters Creek Formation is mined as an absorbent clay in Illinois, Mississippi, Missouri, and Tennessee. The absorptive properties of the Porters Creek Formation are due to the high content of smectite which constitutes >50% of the minerals present. Analyses of 220 samples of the Porters Creek collected in Illinois, Missouri, and Tennessee indicate that the smectite content is highest on the western side of the Mississippi embayment and that the kaolinite content is highest on the northeastern side. The major influx of detritral clays appears to have entered the embayment from a large river on the northeast side. A major control of the distribution of clay minerals during the time of Porters Creek deposition was differential flocculation of kaolinite, illite, and smectite, as evidenced by the numerous syneresis cracks on bedding planes in the area of greatest kaolinite content. Estimates of the smectite, illite, and kaolinite contents suggest both horizontal and vertical variations among these clay minerals. In certain localities the oxidation of pyrite has created acid conditions, which apparently were conducive to the formation of authigenic halloysite.
Structures of Intergrown Triclinic and Monoclinic IIb Chlorites from Kenya
Authors: Zheng Hong , Bailey Sturges W.
Published: August 2006

Triclinic IIb-4 and monoclinic IIb-2 clinochlore polytypes from Kenya are intergrown laterally in (001) platelets and are separated optically in some places by sharp lines of demarcation and in other places by embayed boundaries. Electron microprobe analyses show no compositional differences between the two polytypes. Structural refinements of each show that the 2:1 layer is identical in the two structures with no tetrahedral or 2:1 octahedral cation ordering in either ideal or subgroup symmetries. The two interlayer sheets dilfer only in the distribution of A1 and Mg over interlayer sites M3 and M4, but not in the distribution of Fe3+, Fe2+, or vacancies. The monoclinic IIb-2 polytype is less ordered than the triclinic IIb-4 polytype. The mean M-O,OH bond length of 1.990 Å indicates significantly less of the smaller A1 present in the M4 site of IIb-2 than for the mean M-O,OH value of 1.957 Å for the M4 site of IIb-4. The textural relations and the structural refinements suggest that the monoclinic IIb-2 structure is inherently less stable than the triclinic form. This is in accord with the observed lesser abundance in nature of the monoclinic form.
Structure and Thermal Transformations of Imogolite Studied by 29Si and 27Al High-Resolution Solid-State Nuclear Magnetic Resonance
Authors: MacKenzie K. J. D. , Bowden M. E. , Brown I. W. M. , Meinhold R. H.
Published: August 2006

Solid-state nuclear magnetic resonance (NMR) spectroscopy, thermal analysis, and X-ray powder diffraction data on the tubular, hydrous aluminosilicate imogolite were found to be fully consistent with a previously proposed crystal structure consisting of a rolled-up, 6-coordinate Al-O(OH) sheet, bonded to isolated orthosilicate groups. The calculated 29Si chemical shift of this structure agreed with the observed shift within 3 ppm. Thermal dehydroxylation of the Al-O(OH) sheet produced predominantly NMR-transparent 5-coordinate Al, but a few 4- and 6-coordinate sites and some residual hydroxyl groups may also have formed, as shown by NMR spectroscopy. Changes in the 29Si NMR spectrum on dehydroxylation suggest a condensation of the orthosilicate groups, but steric considerations rule out bonding between adjacent silicons. To account for these observations, an alternative mechanism to orthosilicate condensation has been proposed, involving the fracture and unrolling of the tubes, followed by the condensation of fragments to form a layer structure. The layer structure has a calculated 29Si chemical shift of -95.6 ppm, in good agreement with the observed value of -93 ppm.
Coordination Complexes of p-Hydroxybenzoate On Fe Oxides
Authors: Kung King-Hsi , McBride Murray B.
Published: August 2006

Adsorption 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

High-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

The 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

A 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

Observation 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

X-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

The 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

The 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

The 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

The 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

The 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

A 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

Hornblende 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

The 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

The 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

The 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.