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

Modélisation des propriétés d'excès et de la distribution des espèces H

Ce travail s'inscrit dans le cadre d'un effort de recherche portant sur la modélisation des propriétés des mélanges binaires H2O-H2SO4 . Plus précisément, on montre ici que l'on peut décrire à la fois les propriétés d'excès (coefficient osmotique) et les variations des concentrations des espèces H+, HSO4- et SO42- à l'aide d'une version tronquée du modèle de Pitzer à six paramètres. Le modèle proposé est fiable pour une concentration totale en H2SO4 allant de 0 à 27 mol.kg-1.·Les valeurs des paramètres d'interaction recommandées à 25°C sont les suivantes :[math

Mise en évidence de ruptures de métastabilité par une méthode électrochimique

An electrochemical method of détection of the metastable amalgams crystallization during a monotherm electrolysis is described. It permits to determine the molar fraction of metastability breakdown as well as the molar fraction of thermodynamical equilibrium. The method has been used in the case of mercury-cadmium binary and controlled by Differential Scanning Calorimetry. At ambient temperature, the metastability breakdown takes place at a molar fraction 12 % higher than the equilibrium one.On décrit une méthode électrochimique de détection de la cristallisation d'amalgames métastables au cours d'une électrolyse à température fixe. Elle permet de déterminer la fraction molaire de rupture de métastabilité ainsi que la fraction molaire d'équilibre thermodynamique. La méthode a été utilisée dans le cas du binaire mercure-cadmium et contrôlée par analyse Enthalpique Différentielle. A la température ambiante la rupture de métastabilité a lieu à une fraction molaire 12 % supérieure à celle d'équilibre