Abstract:
The extraction of copper from primary copper sulfide ores is much complicated and
expensive. However, the successful metal extraction from natural mineral resources
is very important, both environmentally and economically. The main objectives of
this research work are to examine possible ways to increase the copper extraction
from chalcopyrite (CuFeS2) using oxidative chemical leaching processes and to
investigate oxidative leaching kinetics of chalcopyrite in sulfuric (H2SO4) acid
medium. Chalcopyrite mineral sample was obtained from Geological Survey and
Mines Bureau (GSMB) in Sri Lanka. Initial investigations characterized the
chalcopyrite ore mineralogically and chemically. X-ray diffraction analysis of
chalcopyrite ore reveled that only chalcopyrite (CuFeS2), azurite (Cu3(CO3)2(OH)2),
pyrite (FeS2) and pyrrhotite (FeS) minerals were present. The copper content of the
chalcopyrite ore sample was found to be 16.6% by weight according to the chemical
analysis. The extraction of copper from chalcopyrite using hydrogen peroxide
(H2O2), ferric sulphate (Fe2(SO4)3), potassium permanganate (KMnO4) and
potassium dichromate (K2Cr2O7) oxidizing agents in acid solutions was studied using
the 63-90 μm particle size fraction of chalcopyrite. The effect of temperature ranging
from 30 ºC to 70 ºC, the effect of concentration of sulfuric acid ranging from 0.25
mol dm-3 to 5.0 mol dm-3 and the effect of pulp density ranging from 2% to 6% on
the rate of dissolution of copper from chalcopyrite ore were also studied. The
extraction rates are significantly influenced by the temperature and the concentration
of the acid solutions. According to the oxidative chemical leaching results, the
maximum extraction of copper was achieved with KMnO4 and then with K2Cr2O7,
followed by H2O2 and Fe2(SO4)3. In this study maximum extraction of 70.2 % of
copper was achieved at 0.1 mol dm-3 KMnO4 in 1.0 mol dm-3 H2SO4 acid. It was
found that oxidizing agents improved the leaching kinetics of chalcopyrite in sulfuric
acid medium saving both time and energy effectively and efficiently. A kinetic study
showed that the dissolution of copper from chalcopyrite ore was controlled by
chemical reaction process on the surface of particles. Based on the results obtained
in this investigation, the apparent activation energy for the dissolution of copper
using the Arrhenius expression was found to be 31.8 kJ mol-1.
