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

¹ Laboratoire de Chimie Appliquée des Matériaux, Université Mohammed V, Faculté des Sciences, Rabat, Morocco
² Laboratoire d’électrochimie et Chimie Analytique, Université Mohammed V, Faculté des Sciences, Rabat, Morocco

Abstract

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.