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

Autoaprendizaje experimental de contenidos científico-técnicos avanzados a partir de material didáctico elemental

Se describe la programación de actividades de autoaprendizaje experimental sobre contenidos cientí- fico-técnicos avanzados, a partir de un material didáctico elemental. Dichas actividades se han referido a la asignatura Química del Estado Sólido, correspondiente a la titulación Ingeniería de Materiales, de segundo ciclo, la cual se imparte por primera vez en la Universidad de Sevilla durante el curso 2005-06. La programación se ha aplicado por sus autores, miembros del Grupo de Investigación FQM 212 del PAI, de carácter multidisciplinar, en un contexto caracterizado por la diversidad de los estudios realizados previamente por los alumnos. Ello ha permitido llevar a cabo su evaluación y presentar los resultados obtenidos.The programmed activities for the experimental selflearnig of advanced scientific and technological contents are proposed. These activities fit into the subject Solid State Chemistry of the Materials Engineering (University of Seville) which has started the academic year 2005-06. The proposed activities have already been tested by the authors, which belong to the Andaluzian Research Group FQM 212, in a multidisciplinary group of students. This experimental trial has allowed the evaluation of the results

Revista de enseñanza universitaria

Resumen tomado de la publicaciónDescribe la programación de actividades de autoaprendizaje experimental sobre contenidos científicos avanzados, a partir de un material didáctico elemental. Dichas actividades se han referido a la asignatura Química del Estado Sólido, correspondiente a la titulación Ingeniería de Materiales, de segundo ciclo, la cual se imparte por primera vez en la Universidad de Sevilla durante el curso 2005-06. La programación se ha aplicado por sus autores, miembros del Grupo de Investigación FQM 212 del PAI, de carácter multidisciplinar, en un contexto caracterizado por la diversidad de los estudios realizados previamente por los alumnos. Ello ha permitido llevar a cabo su evaluación y presentar los resultados obtenidos.AndalucíaUniversidad de León. Facultad de Educación. Servicio de Biblioteca; Campus de Vegazana, s. n.; 24071 León; Tel. +34987291146; Fax +34987291145; [email protected]; [email protected]