The production of electrolytic zinc using sulphide ores consists mainly of four processes: roasting, acid leaching, purification and electrolysis. The roasting step plays an important role on zinc extraction due to the modification from sulphide to oxide structure which provides more reactivity in presence of acid solutions than the former. The two major obstacles in the hydrometallurgical extraction are the presence of highly stable zinc ferrite (ZnFe_2O_4) - formed in the pyrometallurgical step - and the incomplete particle roasting. The objective of this paper is to detect the roasting problems in an electrolytic zinc circuit using X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM/EDS) techniques in sulphide and roasted ores samples. The main structure found in sulphide and roasted ores
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