Electrochemical behaviours of Eu(III)/E(II) and Ce(IV)/Ce(III) in H3PO4-H2O media : solvation and complexation reactions

Many kinds of rare earth elements (REE) such as europium and cerium have been make them essential elements in many high-tech components. The electrochemical studies can be presented as an interesting indication for europium and cerium extraction from phosphoric solutions, including solvation and complexation reactions. The normal redox potentials of Eu3+/Eu2+ and Ce4+/Ce3+ systems have been determined in H3PO4-H2O media with various phosphoric acid concentration. The solvation of these elements in phosphoric media is characterized by their transfer activity coefficients "f" calculated from the corresponding normal redox potentials. The corresponding solvation increases with increasing the H3PO4 concentration. For each REE, the electrochemical properties depend on its number of charges and on its basic properties. Results suggest that solvation and complexation of REE phosphates are important in controlling REE concentration

Electrochemical behaviours of Eu(III)/E(II) and Ce(IV)/Ce(III) in H3PO4-H2O media : solvation and complexation reactions

Many kinds of rare earth elements (REE) such as europium and cerium have been make them essential elements in many high-tech components. The electrochemical studies can be presented as an interesting indication for europium and cerium extraction from phosphoric solutions, including solvation and complexation reactions. The normal redox potentials of Eu3+/Eu2+ and Ce4+/Ce3+ systems have been determined in H3PO4-H2O media with various phosphoric acid concentration. The solvation of these elements in phosphoric media is characterized by their transfer activity coefficients "f" calculated from the corresponding normal redox potentials. The corresponding solvation increases with increasing the H3PO4 concentration. For each REE, the electrochemical properties depend on its number of charges and on its basic properties. Results suggest that solvation and complexation of REE phosphates are important in controlling REE concentration

Electrochemical behaviours of Eu(III)/E(II) and Ce(IV)/Ce(III) in H3PO4-H2O media : solvation and complexation reactions

Many kinds of rare earth elements (REE) such as europium and cerium have been make them essential elements in many high-tech components. The electrochemical studies can be presented as an interesting indication for europium and cerium extraction from phosphoric solutions, including solvation and complexation reactions. The normal redox potentials of Eu3+/Eu2+ and Ce4+/Ce3+ systems have been determined in H3PO4-H2O media with various phosphoric acid concentration. The solvation of these elements in phosphoric media is characterized by their transfer activity coefficients "f" calculated from the corresponding normal redox potentials. The corresponding solvation increases with increasing the H3PO4 concentration. For each REE, the electrochemical properties depend on its number of charges and on its basic properties. Results suggest that solvation and complexation of REE phosphates are important in controlling REE concentration

Estructura biotipológica de las principales redes hídricas rifeñas a través de los simúlidos (Diptera: Simuliidae)

El trabajo está basado en simúlidos recogidos a distintas fases de su desarrollo (larvas, pupas y adultos) entre 1998 y 1999 en las principales redes hidrográficas del macizo rifeño (norte de Marruecos). Se utilizó un análisis de los factores de correspondencias (AFC) para determinar las afinidades y relaciones ecológicas entre 28 especies y 85 estaciones. Se reconoció a cuatro agrupaciones de taxones y estaciones : una primera agrupación caracteriza las especies altícolas y estenotermas, las cuales caracterizan los altlos cursos de agua fría (fuentes y arroyos) ; la agrupación 2 incluye especies propias de zonas de montaña de media y alta altitud ; la nube 3 constituye una agrupación compuesta a nivel ecológico porque incluye una especie a tendencia hemistenoterma junto con las especies más euritermas capturadas en grandes cursos de altitudes medias o bajas ; una última agrupación 4, es formada esencialmente por las especies más termófilas y potamófilas que pertenecen a las zonas mas bajas de los ríos