OXIDATION OF LEAD SULPHIDE

Abstract

Previous research on the precipitation and oxidation of lead sulphide has been reviewed especially in relation to thermodynamic and kinetic studies. Samples of lead sulphide have been precipitated from aqueous solutions of lead salts under varying conditions of pH, concentration, temperature and time of ageing. The precipitates were examined by optical and electron microscopy, X-ray diffraction and gas sorption analysis. Their crystallinity, particle size and phase composition have been correlated with the conditions of precipitation. The oxidation of selected samples of precipitated and commercial lead sulphide was investigated by thermal analysis and the above techniques. The phase composition of the oxidation products were studied under varying conditions of temperature, gas flow rate and oxygen content of air. For the low temperature oxidation (~500°C) the thickness of the lead sulphate product layer was estimated and attempts made to correlate this value with the kinetics of the oxidation. The stability of lead sulphate at high temperature (~900 °C) has been investigated. Sintering behaviour of the products in relation to their incomplete desulphurization was examined. Oxidation studies on lead sulphide were extended to lead-zinc ores with respect to the effect of moisture content and bentonite on sintering. This investigation was carried out on a sinter pallet using 22 kg mixes at ISP Research Department of Imperial Smelting Processes Limited, Avonmouth. The possible formation of lead sulphite as an intermediate in the low temperature oxidation of lead sulphide was investigated by studying the thermal stability of the sulphide under various gaseous atmospheres. These studies were extended to zinc sulphite in relation to previous studies on the oxidation of zinc sulphide . These researches form a part of a wider study in the oxidation of sulphides during shipment, storage and processing.