Modifying the physicochemical and electrical properties of tantalite and columbite surfaces under conditions of electrochemical treatment and high-voltage nanosecond pulses

Abstract

Structural and chemical modifications of tantalite and columbite surfaces, induced by treating the minerals with anolyte—a product derived via the electrolysis of aqueous solutions—and high-voltage electromagnetic pulses, are studied by means of X-ray photoelectron spectroscopy, scanning electron microscopy, energy-dispersive spectroscopy, atomic force microscopy, and electrophoretic light scattering. The mechanical properties of the surfaces are characterized via Vickers microhardness testing. Treating the minerals with anolyte removes iron-containing surface films and leads to considerable conversion of surface-confined Fe(II) species into Fe(III), increasing the differences between the physicochemical and electrical properties of these rare earth minerals. The nonthermal impact of high-voltage pulses results in effective surface softening, a reduction in microhardness, and the disintegration of mineral particles, yielding surface micro- and nanosized phases enriched with iron and oxygen.