Beneficiation of a gold bearing enargite ore by flotation and As leaching with Na-hypochlorite

The deep mineralized bodies of the Italian Serrenti-Furtei gold-bearing deposit, located in southern Sardinia, contain substantial amounts of enargite-luzonite and pyrite with subordinate tennantite, covellite, chalcopyrite and arsenopirite. The gold, which occurs as grains of between a few tens of micrometres and submicron size, is not amenable to direct cyanidation. These ores are beneficiated by bulk flotation using sulphydryl collectors and the resulting concentrates are then pyrometallurgically processed to produce gold and copper. However, the concentrates contain significant amounts of arsenic, severely reducing their market value; the abatement of this highly toxic metal in the flue gas to comply with stringent emission limits, increases processing costs significantly. In order to reduce the arsenic content in the concentrates and hence the penalties incurred, we carried out an investigation on enargite leaching using sodium hypochlorite to selectively dissolve the arsenic. By suitably adjusting the main influencing variables, leaching was found to be effective, achieving 96% arsenic removal without significant Au and Cu losses, increasing the commercial value per tonne of concentrate

Gold recovery enhancement from complex sulphide ores trhough combined bioleaching and cyanidation

The recent discovery of gold$nely intergrown with the complex metal sulphides in the Tertiary volcanites of the Serrenti-Furtei district in central and southern Sardinia, prompted the investigation of gold extraction methods that are both economically viable and environmentally friendly. Here two types of integrated processes for gold extraction are compared: roasting plus cyanidation and bioleaching plus cyanidation. With the first process, overall gold recoveries as high as 85 % are achieved, whereas with a variant of the second, total gold recovered does not exceed 77%. Both types of processes investigated are described in detail. The jndings of the investigation suggest that the advantages ofsered by the biohydrometallurgical processes-especially from the environmental viewpoint-may compensate the lower gold recovery they yield. Q 1997 Elsevier Science Lt

Optimizatio of a productive system. The case of Mont'Ega mine

In the Mont'Ega mine (Sardinia) a complex orebody, composed of the juxtaposition of two heterogeneous mineralizations, selectively mined in the past, is being exploited. The modifications in the nature of the orebody wich have emerged over the years, have led to the revision of the technical solutions adopted wich had been derived from a model based on information available at the time. After a brief description of the preent configuration of the mineralizations, the mining method is illustrated which furnishes two distinct run-of- mines of different composition. The industrials results of the possible alternatives for beneficiating these ores are presented. The economic analysis of the choices feasible indicated the optimum flowsheet as the preliminary gravity concentration of each ore followed by flotation. In conclusion directives for further rationalization of the productive system are outlined