Wet-chemical synthesis of various iron(III) vanadates(V) by co-precipitation route

When the solubility products or other thermodynamic data are not known, the optimum experimental procedures for preparing complex mixed oxides/hydroxides can be approximately predicted by extrapolation of the solubility behaviours; of individual metal ions in aqueous solutions. This simple approach determined a probable co-precipitation domain ranging from pH = 0.7 to pH = 4 for Fe-III-V-V-H2O system. To control the kinetic aspect of condensation mechanisms in order to obtain crystallized compounds, three different experimental protocols were developed leading to successful syntheses of FeVO4. 1.1 H2O, Fe4V6O21.H2O and FeV3O9.2.6 H2O. These vanadates were characterized by X-ray diffraction (XRD), thermal analysis, scanning or transmission electron microscopy (SEM/TEM), and Brunauer-Emmett-Teller (BET) surface area measurements. The results notably revealed that FeVO4.1.1 H2O and FeV3O9.2.6 H2O have close structural similarities with two minerals fervanite and kazakhstanite, respectively. (C) 2003 Academie des sciences. Published by Editions scientifiques et medicales Elsevier SAS. All rights reserved.