Lisciviazione dell’arsenico da un concentrato di flottazione enargitico contenente oro

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 concentrate that besides to be a serious environmental problem severely reduces their market value, we carried out an investigation on arsenic leaching from enargite-luzonite using two different leachant. In particular we tested NaClO and Na2S with NaOH. By suitably adjusting the main influencing variables both reagents was found to be effective. By using NaClO we achieved 96 % of arsenic removal without significant Au and Cu losses. By Na2S we leached almost 98 % of arsenic and also a not negligible quantity of gold, especially at Na2S high dosages, whereas not was Cu losses.