Precipitation of ageing of iron sulphides

Abstract The oxidations of zinc and lead sulphides are important reactions in the extractive metallurgy of these metals. Their sulphide are concentrates contain significant amounts of iron sulphides, which affect the oxidation behaviour of ores. For oxidation studies, iron sulphides have been prepared by precipitation from aqueous solution under different conditions of pH, temperature, concentration and time of ageing. The effect of these factors on the surface and solid-state properties of the products has been studied. Precipitations were carried out with iron (III) chloride and iron (II) sulphates of varying concentrations using hydrogen sulphide gas and aqueous sodium sulphide as the precipitants. The precipitations were carried out at room temperature (20°C) as well as at elevated temperatures (85°C). The products were aged for different lengths of time. The phase compositions and crystallinity of the products were examined by X-ray powder diffraction. The specific surface areas of selected samples were determined by the BET method from the nitrogen adsorption isotherms recorded gravimetrically at −196°C on a CI Mark II vacuum microbalance. Preliminary studies of their oxidation were made on a Stanton-Redcroft mass flow balance. Results will be presented for a selection of precipitated iron sulphides and commercially available materials.