REMOVAL OF ARSENIC AND DISSOLUTION OF COPPER FROM ARSENIC BEARING
COPPER ORE BY HIGH PRESSURE OXIDATION LEACHING
ABSTRACT
Recently, arsenic (As) grade in copper ores is increasing year by year. Arsenic bearing minerals (enargite
(Cu3AsS4) and tennantite (Cu12As4S13)) are coexisting with typical Cu minerals such as chalcopyrite
(CuFeS2). Relatively high arsenic content in the copper minerals reduces their economic value and causes
serious operational and environmental problems. Therefore, it is necessary to develop separation processes
of As from dirty copper concentrates. In this study, arsenic removal from enargite (Cu3AsS4) by high pressure
leaching using ferric sulphate solution with sodium chloride was conducted and dissolution behaviour of Cu
and As into the solution was investigated under the high temperature and high pressure oxidation condition
which were fixed at leaching time of 60 min, pulp density of 100 g/L and total pressure of 1 MPa controlling
by oxygen gas supply with various temperature.
Figure 1 showed that more than 60% of copper was dissolved in 0.1M ferric sulphate solution under the high
pressure oxidation condition, while leaching rate of arsenic was less than 20%. It is confirmed that arsenic
was precipitated as a scorodite (FeAsO4) in the solution. SEM observation revealed that elemental sulfur was
deposited on the surface of enargite forming passivation layer and the residue was agglomerated. Those
phenomena may cause a decrease of the copper leaching rate in the solution. In order to increase the leaching
rate of Cu, 0.34 M of sodium chloride (NaCl) was added to the solution. More than 80 % of Cu was dissolved
in the solution whereas leaching rate of As was 2%.
100
Leaching rate, %
80
Cu
As
60
40
20
0
H2SO4
Fe2(SO4)3
Fe2(SO4)3 + NaCl
Figure 1 – Effect of leaching reagent for dissolution of enargite by high pressure oxidation leaching
(Leaching conditions: temperature of 160˚C leaching time of 60 min, pulp density of 100 g/L
and total pressure of 1 MPa controlling by oxygen gas supply)
KEYWORDS
Arsenic bearing copper ore, high pressure oxidation, copper leaching, ferric sulfate, scorodite.