Evaluation of the recovery of Rare Earth Elements (REE) from phosphogypsum waste – case study of the WIZÓW Chemical Plant (Poland)

The effect of precursor composition and reduction conditions on the characteristics of niobium powders obtained by magnesium reduction were studied. The hypothesis of the possible increase in the specific surface area of the powders by a large factor by using complex oxides as precursors was confirmed. With magnesium niobate Mg4Nb2O9 as the precursor, mesoporous powders, unprecedented in the world, with a specific surface area of up to150 m2 g–1 and an average pore size of 4.6 nm were produced.

Magnesium-vapor reduction of niobium oxide compounds

Advanced Materials Prepared via Metallic Reduction Reactions for Electrochemical Energy Storage

The metallic tantalum powder was successfully synthesized via reduction of tantalum pentoxide (Ta2O5) with magnesium gas at 1073~1223 K for 10 h inside the chamber held under an argon atmosphere. The powder obtained after reduction shows the Ta–MgO mixed structure and that the MgO component was dissolved and removed fully via stirring in a water-based HCl solution. The particle size in the tantalum powder obtained after acid leaching was shown to be in a range of 50~300 nm, and the mean internal crystallite sizes measured by the Scherrer equation varied from 11.5 to 24.7 nm according to the increase in reduction temperatures. The temperature satisfactory for a maximal reduction effect was found to be 1173 K because the oxygen content was minimally saturated to about 1.3 wt %.

Extraction of Tantalum Powder via the Magnesium Reduction of Tantalum Pentoxide

This paper examines the possibility of preparing high-purity sodium-reduced tantalum powders with a large specific surface area We demonstrate that such powders have a larger specific surface area when prepared using potassium heptafluorotantalate based melts containing tantalum oxyfluoride compounds The purity and specific surface area of powders thus prepared are suitable for the development of capacitor powders with a specific capacity of up to 100000 μFV/g

Preparation of high-purity tantalum powders by sodium-thermal reduction

The dependence of the specific surface area of a tantalum powder on the conditions of reduction of magnesium tantalates MgTa2O6 and Mg4Ta2O9 by magnesium vapors is studied. This factor is shown to increase the powder specific surface area by several times. The powders have a nanoporous structure. Tantalum powders with a specific surface area of 65 m2/g (calculated particle size of 6 nm) are synthesized during the reduction of Mg4Ta2O9, and the main part of the surface is formed by mesopores <10 nm in diameter.

Production of tantalum powders by the magnesium reduction of tantalates

Magnesium reduction of tantalum oxide compounds

Results obtained in thermodynamic modeling of the magnesiothermic reduction of niobium and tantalum from pentoxides under adiabatic conditions are given. The dependences of equilibrium temperature of the reactions on the composition and initial temperature of the raw material, along with the equilibrium composition, were determined in the systems Nb2O5-Mg-NaCl and Ta2O5-Mg-NaCl in the temperature range 1200–3000 K.

V. M. Orlov

Papers

Production of tantalum powders by the magnesium reduction of tantalates

Magnesium reduction of tantalum oxide compounds

Magnesium-vapor reduction of niobium oxide compounds

Preparation of high-purity tantalum powders by sodium-thermal reduction

Thermodynamic modeling of magnesiothermic reduction of niobium and tantalum from pentoxides