Influence of temperature and time on the Eu3+ reaction with synthetic Na-Mica-n (n = 2 and 4)

Bentonite is accepted as the best clay material for the engineered barrier of Deep Geological Repositories (DGRs). The performance of clay as the main component of the engineered barrier in the DGR has been intensively studied and the structure of the selected clay mineral play a crucial role. In this sense, a new family of synthetic swelling silicates, Na-Mica-n, with tuned layer charge (n) values between 2.0 and 4.0 per unit cell has recently been synthesized and a general synthetic method has been reported. These swelling high-charge micas could be highly valuable for the decontamination of harmful cations. The ability of these micas to immobilize Eu3+ under subcritical conditions has been probed. The adsorption was in both non-specific sites (cation exchange mechanism) and specific sites (chemical reaction or surface defects adsorption). Moreover, its adsorption capacity, under the same conditions is higher than in saponite and far superior to the bentonites.Junta de Andalucía P12-FQM-567European Union 29178

GESUS, an Interactive Computer Application for Teaching and Learning the Space Groups of Symmetry

This paper describes a digital application designed for learning Space Groups of Symmetry (SGS). It teaches how to recognize the operations performed by the symmetry elements, both point (or 2D) operators (proper and improper rotations, including mirroring, inversion, and other rotoin-versions), and space (or 3D) operators (screw axes and glide planes), as well as their combinations with the translations of the lattice. The software applies a 3D space vision to identify the elements of symmetry compatible with the proposed structural models. The symbols of internationally accepted representation are used. The system, class, and space group of the crystal that agree with the proposed model are solved. Two settings are taken into account in the Monoclinic system. The application self-evaluates and assesses the knowledge acquired, allowing each exercise to be re-done until it is correctly completed with the appropriate recommendations. This application constitutes a useful and easy-to-use tool for SGS learning. It is aimed at beginner students of crystallography, with elementary knowledge about elements of symmetry, Bravais lattices, crystal classes, and wallpaper groups

A new route of synthesis of Na-Mica-4 from sodalite

Synthesis of Na-Mica-4 has been achieved by a ``mix and calcine¿¿ method using sodalite and magnesium fluoride as the only precursors. Previous research found sodalite as a key intermediate reaction product in the formation of Na-Mica-4 when the NaCl melt method was employed. Similarities in structure, chemical composition and cation distribution in products using the proposed method and the NaCl melt method are described and suggest that Na-Mica-4 is a very stable product. The use of sodalite as precursor provokes microporous formation in the final mica. The absence of excess Na leads to a lower particle size and to the presence of less impurity in the calcined product. Different sodalites could be used in the synthesis of different Na-Mica-4 with presumably different physicochemical propertiesPeer Reviewe

Interaction of hydrated cations with mica-n (n = 2, 3 and 4) surface

High charged swelling micas, with layer charge between 2 and 4, have been found to readily swell with water, and complete cation exchange (CEC) can be achieved. Because of their high CEC, applications like radioactive cation fixation or removal of heavy metal cations from wastewater were proposed. Their applicability can be controlled by the location of the interlayer cation in a confined space with a high electric field. In synthetic brittle micas, the interlayer cation has a low water coordination number; therefore, their coordination sphere would be completed by the basal oxygen of the tetrahedral layer as inner-sphere complexes (ISC). However, no direct evidence of these complexes formation in brittle micas has been reported yet. In this contribution, we mainly focus on the understanding the mechanisms that provoke the formation of ISC in high charge swelling micas, Mica-n. A whole series of cations (X) were used to explore the influence of the charge and size of the interlayer cation. Three brittle swelling micas, Mica-n (n = 4, 3 and 2), were selected in order to analyze the influence of the layer charge in the formation of ISC. The contribution of the ISC has been analyzed thorough the evolution of the 060 reflection and the changes in the short-range order of the tetrahedral cations will be followed 29Si and 27Al MAS NMR. The results showed that ISC was favored in X-Mica-4 and that provoked a high distortion angle between the Si-Al tetrahedra. When the content of aluminum decreases, the electrostatic forces between the layers are relaxed, and the hydrated cations did not interact so strongly with the tetrahedral sheet, having the opportunity to complete their hydration sphere. © 2014 American Chemical Society.Peer Reviewe

Evaluation of rare earth on layered silicates under subcritical conditions: Effect of the framework and interlayer space composition

Clay-based minerals are considered to be an important component in backfill barriers due to both their ability to seal and adsorb radioactive waste and to interact chemically with it under subcritical conditions. Herein, we describe a systematic study of the properties of layered silicates that could affect their hydrothermal reactivity, namely type of layers, octahedral occupancy, origin and total amount of the layer charge, and nature of the interlayer cation. The silicates studied were selected on the basis of their different characteristics associated with these properties and were treated hydrothermally at 300 °C for 48 h in a 7.3 · 10− 2 M Lu(NO3)3 · 3.6H2O solution. The final products were analyzed by X-ray diffraction and solid-state NMR spectroscopy. All the layered silicates studied were found to be able to generate a Lu2Si2O7 phase after hydrothermal treatment under subcritical conditions, thereby confirming the participation of a chemical mechanism of the clay barrier generating phases being stables with temperature and pH conditions. However, the extent of this reaction depends to a large extent on the physicochemical properties of the framework and the interlayer space composition, such as the presence or absence of an octahedral sheet, the degree of occupancy of this sheet, and the origin and total layer charge. Therefore, this study allows tuning the clay mineral framework characteristic that favors the rare earth cations (as trivalent actinide simulator) immobilization.Dirección General de Investigaciones Científicas y Técnicas CTQ2010-1487

Applying mobile technologies in the scientific collections knowledge spreading. An example of application in the Geology Museum of the University of Seville

La reciente aparición de dispositivos electrónicos móviles con acceso a internet (tablets, ipads, teléfonos móviles 3G y 4G) abre nuevas posibilidades didácticas y de difusión de colecciones científicas. El objetivo de este trabajo consiste en demostrar las ventajas de la utilización de códigos QR (Quick Response) en las exposiciones de colecciones museísticas de historia natural mediante su aplicación en la exposición del Museo de Geología de la Universidad de Sevilla, actualmente en el CITIUS (Centro de Investigación, Tecnología e Innovación de la Universidad de Sevilla). Esta exposición posibilitó que hace un año se creara la página web del Museo, alojada en la web del CITIUS (http://investigacion.us.es/scisi/sgi/exposiciones). En esta página se puede encontrar información actualizada acerca de la exposición. Actualmente se está elaborando una visita virtual a la exposición del CITIUS, así una persona desde su casa o cualquier otro punto de acceso a internet, podrá realizar una visita al museo de forma virtual, accediendo al contenido de las vitrinas, información de los posters o a cualquier otro material que en ese momento esté disponible. Por otra parte, para aquellos que realicen físicamente la visita, cada expositor dispondrá de un código QR que permitirá al visitante ampliar la información de aquello que está viendo en cada momento, guiándole y permitiéndole acceder a una mayor cantidad de información, como datos sobre las colecciones sistemáticas, referencias a ciertos ejemplares significativos, acceso a juegos/actividades, etc. La inclusión de los códigos QR en los productos creados por el propio Museo (paneles, trípticos,..) amplían la información que nos ofrecen, permitiendo interactuar con el visitante y hacer uso del aprendizaje en red y la educación virtual.The recent appearance of electronic devices with technologies that provide access to internet such as tablets, ipads and mobile phones with 3G and 4G is opening a new way to learning and to share the scientific collections. The aim of this research is to demonstrate the advantages of using QR codes (Quick Response) in the exhibition of natural history collections, in particular through its application to the Geology Museum of the University of Seville, currently in the CITIUS (Research, Technology and Innovation Centre of the University of Seville). This exhibition opened in 2011, and facilitated the possibility of creating the web site of the Museum, which is also part of the CITIUS web site (http://investigacion.us.es/scisi/sgi/exposiciones). In this web page it is possible to find updated information about the exhibition. Currently it is taking place the development of a virtual exhibition, therefore anyone with internet access could perform a virtual visit to the Museum, looking directly at the display stands and cabinets, obtaining access to the posters information or to any of the available resources. Also, for people who are physically visiting the Museum, a QR code will be provided in each of the cabinets, to allow the visitors to increase the initial information of the specimens shown. In this form the visitor could access to data about the systematic collections, literature references, significant specimens, and they will also have access to related games and activities. The inclusion of QR codes in each of the products developed at the Museum (posters, leaflets...) are going to increase the information displayed allowing the visitor interaction and making use of the e-learning

Cesium adsorption isotherm on swelling high-charged micas from aqueous solutions: Effect of temperature

The potential use of a new family of synthetic swelling micas for cesium immobilization from aqueous solution was evaluated and the structural modifications after adsorption were analyzed. The results have revealed that they are good cesium adsorbents compared to natural clays and as the layer charge increases, the adsorption capacity and affinity increase. The cesium ions are adsorbed through a cation exchange mechanism, but an inner sphere complex with the basal O atoms of the tetrahedral sheet is favored. These findings imply that is possible to design minerals with improved environmental applications.Junta de Andalucía (España) y fondos europeos FEDER - P12-FQM-567Programa Estatal Español de I+D+i orientado a retos sociales y Fondos Europeo FEDER - MAT2015-63929- REmpresa Nacional de Residuos Radiactivos de España (ENRESA) - 007900023

Bionanocomposites based on chitosan intercalation in designed swelling high-charged micas

Bionanocomposites based on layered inorganic components, as clays, and polymers of biologicalorigin, as chitosan, have a major impact in medical and environmental fields, being economical and environmentally friendly materials. Na-Mn micas (n = 2 and 4) with controlled surface charge, high cation exchange capacity and swelling behaviour, are attractive inorganic composite components that exhibit improved adsorption properties compared to other inorganic solids which makes them potentially useful for bionanocomposites. The goal of this research was to explore the potential use of those synthetic brittle micas to form eco-friendly bionanocomposites with chitosan biopolymer. Hence, chitosan-mica bionanocomposites were prepared by ion-exchange reaction between chitosan solution and synthetic high charge mica. X-ray diffraction, Fourier transform infrared spectroscopy, thermal analysis, MAS-NMR spectroscopy and zeta-potential have been employed for bionanocomposites characterization. The results showed that the adsorption of chitosan is effective, although a chitosan portion remains in the outer surface being hydrogen-bonded to the tetrahedral sheet of the silicate.The authors would like to thank the Junta de Andalucía (Spain) and FEDER (Proyecto de Excelencia de la Junta de Andalucía, project P12-FQM-567), to the Spanish State Program R + D + I oriented societal challenges and FEDER (Project MAT2015-63929-R) for financial support. F.J. Osuna thanks his grant to the training researcher program associated to the excellence project of Junta de Andalucía (P12-FQM-567). Finally, we thanks to the Colloidal Materials Group of the Instituto Ciencia de los Materiales de Sevilla (ICMS) for their help in the Zetapotential measurements

Novel Procedure for Laboratory Scale Production of Composite Functional Filaments for Additive Manufacturing

Successful 3D printing by material extrusion of functional parts for new devices requires high quality filaments. Uniform homogeneity and good dispersion of particles embedded in filaments typically takes several cycles of extrusion or well-prepared feedstock by injection molding, industrial kneaders or twin-screw compounding. These methods need specific production devices that are not available in many laboratories non-specialized in polymer research, such as those working on different material science and technology topics that try to connect with additive manufacturing. Therefore, laboratory studies are usually limited to compositions and filler concentrations provided by commercial companies. Here, we present an original laboratory scale methodology to custom-prepare the feedstock for extruding magnetic composite filaments for fused filament fabrication (FFF), which is attainable by a desktop single-screw extruder. It consists in encapsulating the fillers in custom made capsules that are used as feedstock and reach the melting area of the extruder maintaining the same concentration of fillers. Results have shown that our approach can create smooth and continuous composite filaments with good homogeneity and printability with fine level of dimensional control. We further show the good dispersion of the particles in the composite filament using X-Ray Tomography, which enabled a 3D reconstruction of the spacial distribution of the embedded magnetic particles. The major advantage of this new way of preparing the composite feedstock is that it avoids the hassle of multiple extrusion runs and industrial machinery, yet providing uniform filaments of well controlled filler concentration, which is predictable and reproducible. The proposed methodology is suitable for different polymer matrices and applicable to other functional particle types, not just limited to magnetic ones. This opens an avenue for further laboratory scale development of novel functional composite filaments, useful for any community. This democratization of complex filament preparation, including consumers preparing their own desired uniform novel filaments, will facilitate to unify efforts nearing 3D printing of new functional devices.Fondo Europeo de Desarrollo Regional MAT-201677265-RJunta de Andalucía US-1260179, P18-RT-74

A new route of synthesis of Na-Mica-4 from sodalite

Synthesis of Na-Mica-4 has been achieved by a ``mix and calcine¿¿ method using sodalite and magnesium fluoride as the only precursors. Previous research found sodalite as a key intermediate reaction product in the formation of Na-Mica-4 when the NaCl melt method was employed. Similarities in structure, chemical composition and cation distribution in products using the proposed method and the NaCl melt method are described and suggest that Na-Mica-4 is a very stable product. The use of sodalite as precursor provokes microporous formation in the final mica. The absence of excess Na leads to a lower particle size and to the presence of less impurity in the calcined product. Different sodalites could be used in the synthesis of different Na-Mica-4 with presumably different physicochemical propertiesDirección General de Investigaciones Científicas y Técnicas CTQ2010-1487