Thirty six bentonite samples from 16 different locations were examined in order to demonstrate the applicability of a new Rietveld description approach for quantitative phase analysis. X-ray diffraction patterns of the bulk material were obtained and analyzed by the Rietveld method. The samples contain up to ten different minerals, with dioctahedral smectite as the major component. A model for turbostratic disorder of smectites was formulated inside a structure-description file of the Rietveld program BGMN. The quality of the refinements was checked using an internal standard mineral (10.0 or 20.0 wt.% corundum) and by cross-checking results with X-ray fluorescence (XRF) data. The corundum content was reproduced with only small deviations from the nominal values. A comparison of the chemical composition obtained by XRF and the composition as re-calculated from quantitative Rietveld results shows a satisfactory agreement, although X-ray amorphous components such as volcanic glasses were not considered. As a result of this study, the Rietveld method combined with the new structure model for turbostratic disorder has proven to be a suitable method for routine quantitative analysis of bentonites with smectites as the dominant clay minerals.

Large transition-metal contents add desirable physical properties, such as redox reactivity, magnetism, and electric or ionic conductivity to micas and make them interesting for a variety of materials-science applications. A Mn- and F-rich tainiolite mica, , was synthesized by a high-temperature melt-synthesis technique. Subsequent annealing for 10 days led to a single-phase and coarsegrained material. Single-crystal X-ray diffraction studies were performed and characteristic geometric parameters were compared to the analogous ferrous compound, synthetic Fe-rich tainiolite, . Both tainiolite structures are outside the compositional stability limits for the 2:1 layer structure, and incorporating the relatively large cation Mn2+ requires significant structural adjustments in both the octahedral and tetrahedral sheets. As expected, increasing the ionic radius of the octahedral cation from 0.78 Å (VIFe2+) to 0.83 Å (VIMn2+) reduces the octahedral flattening angle from <Ψ> = 57.05° to <Ψ> = 56.4°, the smallest value ever observed for a tetrasilicic mica. However, even this small <Ψ> value is insufficient to match the lateral sizes of the tetrahedral and octahedral sheets and, in addition, unusual structural adjustments in the tetrahedral sheet are required. The average tetrahedral bond length <T-O> is much greater (1.643 Å) than the average value observed for tetrasilicic micas (1.607 Å,) and a significant difference between the <T-O>apical (1.605 Å) and the <T-O>basal bond lengths (1.656 Å) and an enlarged basal flattening angle (τbas = 106.29°) are noted. These parameters indicate: (1) that the 2:1 layer might be more flexible than previously thought, to allow matching of the lateral dimensions of the tetrahedral and octahedral sheets; and (2) that many other compositions that appear interesting from a materials-science point of view might be accessible.

Acid-base titrations and attenuated total reflectance-infrared (ATR-IR) spectroscopy of solutions containing Zn(NO3)2 and the herbicide 3-amino-1,2,4-triazole suggested that soluble complexes ZnL2+ and Zn(OH)L+ form, where L represents aminotriazole. Sorption experiments and modeling in systems containing K-saturated Wyoming (SWy-K) montmorillonite suggest that at low concentrations the aminotriazole sorbs primarily in cationic form via an ion-exchange mechanism. Sorption isotherms for aminotriazole are ‘s’-shaped, indicating a co-operative sorption mechanism as the concentration of the molecule increases. At higher concentrations, ATR-IR spectroscopy indicated the presence of cationic and neutral triazole molecules on the surface, while X-ray diffraction data suggest interaction with interlayer regions of the clay. When the concentration of the herbicide was high, initial sorption of aminotriazole cations modified the clay to make the partitioning of neutral molecules to the surface more favorable. Experiments conducted in the presence of Zn(II) indicated that below pH 7, Zn(II) and aminotriazole compete for sorption sites, while above pH 7 the presence of Zn(II) enhances the uptake of aminotriazole. The enhancement was attributed to the formation of an inner-sphere ternary surface complex at hydroxyl sites (SOH) on crystal edges, having the form [(SOZn(OH)L)]0.

Geological disposal is the preferred option for the final storage of high-level nuclear waste and spent nuclear fuel in most countries. The selected host rock may be different in individual national programs for radioactive-waste management and the engineered barrier systems that protect and isolate the waste may also differ, but almost all programs are considering an engineered barrier. Clay is used as a buffer that surrounds and protects the individual waste packages and/or as tunnel seal that seals off the disposal galleries from the shafts leading to the surface.

Bentonite and bentonite/sand mixtures are selected primarily because of their low hydraulic permeability in a saturated state. This ensures that diffusion will be the dominant transport mechanism in the barrier. Another key advantage is the swelling pressure, which ensures a self-sealing ability and closes gaps in the installed barrier and the excavation-damaged zone around the emplacement tunnels. Bentonite is a natural geological material that has been stable over timescales of millions of years and this is important as the barriers need to retain their properties for up to 106 y.

In order to be able to license a final repository for high-level radioactive waste, a solid understanding of how the barriers evolve with time is needed. This understanding is based on scientific knowledge about the processes and boundary conditions acting on the barriers in the repository. These are often divided into thermal, hydraulic, mechanical, and (bio)chemical processes. Examples of areas that need to be evaluated are the evolution of temperature in the repository during the early stage due to the decay heat in the waste, re-saturation of the bentonite blocks installed, build-up of swelling pressure on the containers and the surrounding rock, and degradation of the montmorillonite component in the bentonite. Another important area of development is the engineering aspects: how can the barriers be manufactured, subjected to quality control, and installed?

Geological disposal programs for radioactive waste have generated a large body of information on the safety-relevant properties of clays used as engineered barriers. The major relevant findings of the past 35 y are reviewed here.

Antibacterial clays in nature include a variety of clay mineral assemblages that are capable of killing certain human pathogens. Although clays have been used for medicinal applications historically, only in the last decade have analytical methods and instrumentation been developed that allow researchers to evaluate the antibacterial mechanisms of various clays applied medicinally. Comparisons of the mineralogical and chemical compositions of natural clays that kill bacteria have promoted a better understanding of the mineral properties that are toxic to a broad-spectrum of human pathogens, including bacteria that have developed resistance to antibiotics. Popular literature is filled with reports of ‘healing’ clays, that, when tested against pathogens in vitro and compared to controls, do not appear to have bactericidal properties. It is important, however, to differentiate what properties make a clay ‘healing,’ versus what makes a clay ‘antibacterial.’ Most antibacterial clays identified to date buffer pH conditions of a hydrated clay outside the range of conditions in which human pathogens thrive (circum-neutral pH) and require oxidation reactions to occur. It is the change in oxidation state and pH imposed by the hydrated clay, applied topically, that leads to a chemical attack of the bacteria. Healing clays, on the other hand, may not kill bacteria but have soothing effects that are palliative. This article reviews some of the historical uses of clays in medicine but focuses primarily on the common characteristics of natural antibacterial clays and early studies of their antibacterial mechanisms. In this era of bacterial resistance to antibiotics, mimicking the antibacterial mechanisms exhibited by natural clays could be advantageous in the development of new antimicrobial agents.

Interactions between smectite clay minerals and various organic dyes have been studied extensively, but little information has accumulated from dye interactions with mixed-layer illite-smectite (I-S) minerals, especially regarding relationships with clay layer expandability, layer charge, particle size/shape, and molecular aggregation of organic dye molecules. The purpose of this study was to investigate the surface interactions of a set of mixed-layer illite-smectites from different geological environments with Rhodamine 6G dye. The samples used have different amounts of expandable smectite interlayers, different particle size and/or shape, and different layer-charge density at the surface. Five smectites with differences in layer charge and some non-expandable layer silicates were also tested. The interactions detected by UV-vis spectroscopy show no reaction between R6G and non-expandable minerals (kaolinite, mica), and intense reactions forming H-aggregates and monomers with smectites and illite-smectites. The intensity of H-aggregate formation increases with increase in the layer charge of smectites. Mixed-layer illite-smectites interact with R6G more intensely than do smectites. H-aggregate and monomer formation increases with the illitization process for randomly ordered illite-smectites (R = 0) and decreases in the course of illitization for the ordered illite-smectites (R > 0).

Catholic social thought and teaching is sometimes conceptualised using an historical or principles-based approach. This paper proposes an alternative framing, construing Catholic social teaching (CST) as a multi-layered phenomenon that can be grouped into three broad tiers, each with a distinctive role. This framing is not intended to supercede the others, nor is it inconsistent with them. The proposal emerges out of a series of discussions hosted by the Catholic Agency for Overseas Development, a Catholic UK-based development agency, member of Caritas Internationalis, and an official agency of the Bishops’ Conference of England and Wales. The paper operates on two levels simultaneously: it attempts a distinctive reframing of CST using a distinctive source, and it attempts an enactment of CST methodologically and structurally. Construing CST as a multi-layered phenomenon that can be grouped into three broad tiers provides a clarity that empowers us in two ways. First, it clarifies the distinctive role of CST at each level. Second, it makes clear that CST is a work of the Spirit rather than a human phenomenon. Such an understanding of CST brings out with particular clarity a vision of the role, purpose, and even the agency of Catholic social thought in relation to a troubled world.

Layers of volcanic ash and Andosol soils derived from the ash may play an important role in preserving snow and ice as well as in the development of permafrost conditions in (a) the immediate vicinity of volcanoes at high elevations or at high latitudes and (b) land areas that are often distant from volcanic activity and are either prone to permafrost or covered by snow and ice, but have been affected by subaerial ash deposition. The special properties of volcanic ash are critically reviewed, particularly in relation to recent research in Kamchatka in the Far East of Russia. Of special importance are the thermal properties, the unfrozen water contents of ash layers, and the rate of volcanic glass weathering.Weathering of volcanic glass results in the development of amorphous clay minerals (e.g. allophane, opal, palagonite), but occurs at a much slower rate under cold compared to warm climate conditions. Existing data reveal (1) a strong correlation between the thermal conductivity, the water/ice content, and the mineralogy of the weathered part of the volcanic ash, (2) that an increase in the amounts of amorphous clay minerals (allophane, palagonite) increases the proportion of unfrozen water and decreases the thermal conductivity, and (3) that amorphous silica does not alter to halloysite or other clay minerals, even in the Early Pleistocene age (Kamchatka) volcanic ashes or in the Miocene and Pliocene deposits of Antarctica due to the cold temperatures. The significance of these findings are discussed in relation to past climate reconstruction and the influence of volcanic ash on permafrost aggradation and degradation, snow and ice ablation, and the development of glaciers.

Based on the open-source IIIF image viewer Mirador 3, the Specialised Information Service Art, Photography, Design - arthistoricum.net, in cooperation with NFDI4Culture, the consortium for research data on material and immaterial cultural heritage, provides a platform for collaborative exploration of image resources. Within the virtual research environment, users can create their own workspaces and image collections individually or in groups, share them for collaborative efforts, and jointly create persistent annotations. This article outlines the development and integration process of this web-based research platform and highlights future areas of improvement.

Deep sediments from the Red Sea have been studied extensively and provide a rich resource for understanding mineral transformations under hydrothermal conditions. Interrelationships among various sampling sites, however, are still rather incomplete. The purpose of the present study was to increase understanding of these systems by characterizing and comparing the Fe-Mn oxyhydroxides from the southern Atlantis II, Chain A, Chain B, and Discovery Deeps, using high-resolution transmission electron microscopy. Some of the hydrothermal sediments of Chain A are dominated by Si-associated Fe oxides (ferrihydrite, goethite, lepidocrocite, and short-range ordered, rounded particles) resembling the hydrothermal sediments of the SW basin in the Atlantis II Deep, indicating sub-bottom connections between the Deeps. Although some of the sediments of the Discovery Deep show a similar trend; short-range ordered, rounded particles were not detected in these sediments, implying that crystallization of this short-range ordered phase is sensitive to the Si/Fe ratio in the brine and only at elevated ratios does it crystallize out of the brine. Silicon-associated and Fe-enriched Mn oxyhydroxides such as groutite, manganite, todorokite, and Mn-dominated lathlike layers occasionally contain Ca and Mg impurities. Manganese substitutes for Fe and vice versa, leading to a solid-solution series between goethite and groutite and Mn-enriched ferrihydrite. Hematite is the only Fe oxide in the hydrothermal sediments that is found to be lacking in impurities, which is probably due to its formation by recrystallization from other Fe oxides.

Quantitative mineralogical analysis of clay-bearing rocks is often a non-trivial problem because clay minerals are characterized by complex structures and are often affected by structural disorder, layer-stacking disorder, and interstratification. In the present study, internal-standard Rietveld X-ray powder diffraction (XRPD) analyses were combined with X-ray fluorescence (XRF) chemical analyses for the mineralogical characterization and quantitative analysis of heterogeneous clay-rich sedimentary rocks that are involved in a slow-moving landslide in the Termini-Nerano area, Sorrento Peninsula (Italy), in order to investigate the relationship between the mineralogy of these rocks and landslides. Slow-moving landslides are usually considered to be associated with the more weathered and surficial parts of structurally complex slopes, and mineralogical analysis can help to clarify the degree of weathering of siliciclastic rocks. XRPD quantitative analyses were conducted by combining the Rietveld and internal standard methods in order to calculate the amounts of poorly ordered phyllosilicate clays (considered amorphous phases in Rietveld refinements) by difference from 100%. The vbAffina program was used to refine the amounts of mineral phases determined with XRPD using the element compositions determined by XRF analysis. XRPD analyses indicated that the samples mainly contain several different clay minerals, quartz, mica, and feldspars. Analysis of the clay fraction identified kaolinite, chlorite, and interstratified illite-smectite (I-S) and chlorite-smectite (C-S). The mineralogy of the materials involved in the landslide in comparison with the mineralogy of the “undisturbed” rocks showed that the landslide is located in the weathered realm that overlies an arkosic bedrock. The interstratified I-S and C-S occurred at landslide activity locations and confirmed that areas more susceptible to sliding contained the most weathered parts of the rocks and perhaps represent areas of past and currently active fluid flow.

LongYan kaolin has a large Fe content which affects the coloring. Bioleaching treatments to remove Fe impurities were conducted here using indigenous dissimilatory Fe(III)-reducing bacteria. The factors that affect bioleaching efficiency include bioleaching time, carbon source, pH, temperature, pulp density, and inoculum density and these were examined. Environmental scanning electron microscopy and X-ray diffraction were used to examine any textural or mineralogical changes at the surface of the kaolin that may have occurred during the bioleaching. Iron impurities in the kaolin were reduced from 0.88% to 0.48% with an increase in the natural whiteness index from 60.8% to 81.5% after 7 days of bioleaching treatment. A granulometric analysis of dispersed kaolin demonstrated that the bioleaching resulted in a decrease in particle size. The results demonstrated that the bioleaching was very effective at improving the quality of the kaolin, where insoluble Fe(III), either adsorbed to the kaolin surfaces or admixed as amorphous forms, was leached out by micro-organisms as water-soluble Fe(II).

Catalysts are very important in the use of cellulose, the main component of biomass, as a raw material for the large-scale production of liquid fuels and chemicals. 5-Hydroxymethylfurfural (HMF) is an extremely important intermediate in the fine chemical industry. HMF can be synthesized by acid-catalyzed dehydration of fructose, glucose, cellulose, or sucrose. The conversion of cellulose to HMF is challenging due to its chemical structure. The objective of the present study was to devise a more facile synthesis method using transition metal-doped montmorillonite catalysts (10Cr-Mnt, 10Cu-Mnt, 10Fe-Mnt, and 10Zn-Mnt) by wet impregnation. Samples were characterized by X-ray powder diffraction, specific surface area, and NH3-TPD analyses. The synthesized catalysts were used for the conversion of cellulose to 5-HMF in an aqueous medium. Among the metals studied, Cr showed the greatest catalytic activity. With the use of this catalyst, efficient conversion of cellulose to 5-HMF was achieved, affording a conversion yield of 93.47% and 5-HMF yield of 9.07% within 6 h at 200°C. The study described here could be useful for the efficient conversion of cellulose into 5-HMF, as well as into other biomass-derived chemicals.

The emergence of Sardis as an urban centre in the early Iron Age coincided with local production of fine painted pottery in a distinctive regional idiom. Examples of Lydian-style pottery found across western Anatolia from the eighth century BC attest the city’s growing cultural and economic contacts as well as consistent materials and craft methods. Archaeo- metric study using neutron activation analysis (NAA) at the University of Missouri Research Reactor (MURR) examined representative specimens of Lydian-style ceramics from Sardis and compared their composition with later examples of red-gloss and red-slipped pottery, fine grey wares and transport jars commonly found at the site. The results confirm the sustained activity of local workshops from the early Iron Age into later historical periods, as Lydia became part of the Seleucid and Roman empires and Sardis a centre of regional innovation.