K. Elamari et al., Acid and oxidizing leaching of chalcopyrite concentrate by ferric sulphateand fluorosilicic-nitric media, SEP SCI TEC, 35(13), 2000, pp. 2143-2158
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.