Atmospheric oxidative and non-oxidative leaching of Ni-Cu matte by acidified ferric chloride solution
LM Sekhukhune, F Ntuli, E Muzenda
The atmospheric leaching of copper-bearing matte by acidic ferric chloride
solution was studied at the laboratory scale. The aim was to achieve
maximum copper and nickel recovery by investigating the mechanisms of
leaching, as well as identifying the effect of temperature, and concentration
of ferric chloride and oxygen. Djurleite (Cu1.96S), hazelwoodite (Ni3S2),
and Ni alloy were the primary phases detected in the matte. The quantitative
composition of the matte was Cu 31%, Ni 50%, S 13%. Fe and Co
constituted 2%, with platinum group metals (PGMs) accounting for 0.5%. A
maximum nickel extraction of 98% was achieved using two-stage oxidative
leaching at 90°C and 11 g/L Fe3+ as compared to 65% under non-oxidative
conditions. A copper extraction of 99% was achieved in the first 45 minutes
using two-stage non-oxidative leaching, and copper was recovered from
solution by cementation. Three processes took place simultaneously
throughout the leaching process, namely: dissolution, cementation/
metathesis, and oxidation. The leaching process was found to be diffusioncontrolled.
Keywords: Ni-Cu matte, acid leaching, cementation, ferric chloride, leaching
mechanism.