Thermal, analysis studies on multimetal sulphides: Characterisation, roasting and leaching

Thermal analysis (TA) studies have been made to understand changes in miner alogy that occur when pure sulphide minerals, single concentrates and diffe rent Cu-Zn-Pb sulphide concentrates are heated in air. The observed sequent ial oxidation behaviour of bath the synthetic and natural sulphide minerals is characterised by TA traces that are reasonably reproducible. It is show n that oxidation mechanisms of synthetic analogues during roasting are simi lar to those of bulk concentrates. The oxidation data thus obtained on sulp hide roast products are also found to be useful to characterise some partia l leach residues. During ammonia leaching of bulk concentrates, the pyrite grains are practically inert and remain in the leach residue along with oxi dated lead compounds and goethite. The TA data for roasting of partially le ached samples are compared with those for roasting of untreated feed concen trates. The oxidation behaviour of copper, zinc and lead mineral phases of leach residues is then characterised. The observations are corroborated by chemical phase analysis, X-ray diffraction (XRD) and optical microscopy.