Acid and oxidizing leaching of chalcopyrite concentrate by ferric sulphateand fluorosilicic-nitric media

A hydrometallurgical treatment was applied to the Hajar Mine Cooper Concent rate (HMCC), Morocco, containing approximate to 28.1% copper (the major cop per mineral phase is chalcopyrite. CuFeS2), approximate to 26.3% iron, appr oximate to 5.8% zinc, approximate to 1.9% lead, approximate to 33.7% sulphu r, and small amounts of silver (269 g/t) and nickel (219 g/t). Three acid m edia were used: ferric sulphate in sulfuric acid, ferric sulphate in hexafl uorosilicic acid, and a hexafluorosilicic acid-nitric acid mixture. The results show that when a ferric sulphate reagent is used, in H2SO4, as well as in H2SiF6, media, dissolution of copper and iron do not exceed 30%, because of the formation of a passivation layer on chalcopyrite particles, whereas zinc is dissolved at about 90%. The final solid leachate residue r epresents 75% by weight of the initial solid and remains rich in copper (ap proximate to 28%) and iron (approximate to 25%). However, under strong acid and oxidizing conditions, in the hexafluorosilicic acid-nitric acid mixtur e, the dissolution of copper is more efficient, although it is nonselective , (92% Cu. 89% Fe, 98% Zn). The solid leachate residue represents only 40% by weight of the original sample, and assays 5.9% Cu, 7.3% Fe, 0.2% Zn, 4.1 % Pb, and 56.4% S-total. Mineralogical characterizations of the leachate solid residues show the for mation of both elemental sulphur and a Cu1-xFe1-yS2-z layer on the surface of the nondissolved chalcopyrite.