Abstract
The effects of ammonia concentration and leaching time were investigated to determine the
optimum leaching conditions. The experiments were conducted in a leaching cell submerged in a water bath,
with ammonia concentrations of 1.5 M, 2.0 M, 2.5 M and 3.0 M and varying leaching time from 0 to 300 min.
Ni-Cu matte containing 23% by mass Cu was used in this experimental study. Increase in the concentration
of the lixiviant was found to increase recovery when leaching for 130 minutes, with a recovery of 32.86% Cu
using 3 M solution of ammonia. An increase in the leaching time resulted in more copper being leached for
all lixiviant concentrations. However, leaching with 2 M ammonia solution gave a higher yield of copper
compared to higher concentrations. This anomaly could be a result of cementation; Cu is displaced by Ni as
Ni is a more electronegative metal than Cu .It was found that at higher concentrations more nickel was
extracted.