Correlation between dielectric properties and aqueous oxidation rate for pulverized sphalerites and zinc concentrates

Abstract

In a previous paper the dielectric properties, including dielectric constant, dielectric loss tangent, and relaxation time, of six particulate sphalerite samples and four zinc flotation concentrates were measured using a packed bed condenser. In the current study, the same particulate samples were ground to an average size of 8.5 µm, and together with the concentrates underwent oxidation in an acidic sulfate solution, containing 100 g/dm³ H₂SO₄, 10 g/dm³ total Fe, and 30 g/dm³ Zn, at a controlled suspension potential of 0.55 V (Ptvs SCE) and at 90 °C (363 K). Under these experimental conditions, the Fe³⁺ concentration and the suspension potential had little effect on the oxidation rate. The oxidation proceeded mainly in the sulfur-forming type. The results were analyzed using a simplified kinetic expression for spherical particles with a logarithmic normal size distribution. It was found that the rate constant varied in proportion to the 0.6th power of the reciprocal of the equivalent parallel resistances for the dense substance and the packed bed. The rate constant also varied in proportion to the reciprocal of the dielectric relaxation time; however, this variation was influenced by the copper content of the samples.