1893
Selective Removal of Arsenic from Enargite-Scorodite Ore via
Alkaline-Hypochlorite Leaching
Terrence Louis A. Rosal, Djoan Kate T. Tungpalan and Manolo G. Mena
Department of Mining, Metallurgical and Materials Engineering, University of the Philippines-Diliman, Philippines
ABSTRACT: Arsenic leaching from an enargite-scorodite ore in alkaline condition using sodium hypochlorite
was investigated. The ore contains 1.06% As and 1.09% Cu with enargite and scorodite as primary arsenic
minerals. Scorodite was observed to readily dissolve in basic conditions and contributed to at most 33% As.
Results showed that arsenic dissolution increased with higher solvent concentration and reduced particle
size but decreased with increased temperature due to the accelerated decomposition of ClO–. About 85%
As was dissolved within two hours of leaching at room temperature and 0.6M NaClO. Leaching curves were
characterized by a fast initial dissolution rate followed by an abrupt decrease. Based on kinetic modelling, the
leaching behavior is typified by the Avrami model. This study demonstrates the application of NaClO-NaOH
for the removal of arsenic in Cu ores.
Keywords: Enargite dissolution, scorodite, sodium hypochlorite, arsenic leaching
INTRODUCTION
Copper is an essential metal that will support the move
towards a more sustainable low-carbon future. This move
is anticipated to drive the copper demand in areas such as
vehicles, wind turbines, and other green energy (Flores, et
al., 2020). To satisfy this increase in demand, the indus-
try will have to increase current production or develop
new copper projects. As a result, supply is forecasted to
be sourced from non-traditional copper resources partic-
ularly ores with lower grades, more complex mineralogy
and increasing levels of deleterious elements (Barrios et al.,
2011).
One of the most common toxic impurities found in
copper concentrates is arsenic. This element has shown to
exhibit extreme toxic potential with serious health implica-
tions including carcinogenic properties. Arsenic associated
with copper ores occur commonly as enargite (Cu3AsS4) or
tennantite (Cu12As4S13). Other rare copper-arsenic miner-
als include luzonite (Cu3AsS4), and sinnerite (Cu6As4S9)
(Filippou et al., 2007).
Mineral processing does not always achieve complete
separation of Cu-As minerals such as enargite from the Cu
minerals including chalcopyrite, and often these minerals
report to the flotation concentrates. The resulting high-
arsenic copper concentrate is not only a problem for smelt-
ers but to the mines as well since high impurity content
reduces the concentrate’s marketability and implies higher
costs from penalties. The presence of high arsenic in cop-
per concentrates imposes additional costs on the smelter
operators. These include environmental and occupational
health control costs, disposal costs, smelting and refining
costs. (Fountain 2013 Barrios et al., 2011)
Removal of arsenic impurity at an early stage of process-
ing is more advantageous compared to handling high arse-
nic wastes or extraction of arsenic from metallic product.
Selective Removal of Arsenic from Enargite-Scorodite Ore via
Alkaline-Hypochlorite Leaching
Terrence Louis A. Rosal, Djoan Kate T. Tungpalan and Manolo G. Mena
Department of Mining, Metallurgical and Materials Engineering, University of the Philippines-Diliman, Philippines
ABSTRACT: Arsenic leaching from an enargite-scorodite ore in alkaline condition using sodium hypochlorite
was investigated. The ore contains 1.06% As and 1.09% Cu with enargite and scorodite as primary arsenic
minerals. Scorodite was observed to readily dissolve in basic conditions and contributed to at most 33% As.
Results showed that arsenic dissolution increased with higher solvent concentration and reduced particle
size but decreased with increased temperature due to the accelerated decomposition of ClO–. About 85%
As was dissolved within two hours of leaching at room temperature and 0.6M NaClO. Leaching curves were
characterized by a fast initial dissolution rate followed by an abrupt decrease. Based on kinetic modelling, the
leaching behavior is typified by the Avrami model. This study demonstrates the application of NaClO-NaOH
for the removal of arsenic in Cu ores.
Keywords: Enargite dissolution, scorodite, sodium hypochlorite, arsenic leaching
INTRODUCTION
Copper is an essential metal that will support the move
towards a more sustainable low-carbon future. This move
is anticipated to drive the copper demand in areas such as
vehicles, wind turbines, and other green energy (Flores, et
al., 2020). To satisfy this increase in demand, the indus-
try will have to increase current production or develop
new copper projects. As a result, supply is forecasted to
be sourced from non-traditional copper resources partic-
ularly ores with lower grades, more complex mineralogy
and increasing levels of deleterious elements (Barrios et al.,
2011).
One of the most common toxic impurities found in
copper concentrates is arsenic. This element has shown to
exhibit extreme toxic potential with serious health implica-
tions including carcinogenic properties. Arsenic associated
with copper ores occur commonly as enargite (Cu3AsS4) or
tennantite (Cu12As4S13). Other rare copper-arsenic miner-
als include luzonite (Cu3AsS4), and sinnerite (Cu6As4S9)
(Filippou et al., 2007).
Mineral processing does not always achieve complete
separation of Cu-As minerals such as enargite from the Cu
minerals including chalcopyrite, and often these minerals
report to the flotation concentrates. The resulting high-
arsenic copper concentrate is not only a problem for smelt-
ers but to the mines as well since high impurity content
reduces the concentrate’s marketability and implies higher
costs from penalties. The presence of high arsenic in cop-
per concentrates imposes additional costs on the smelter
operators. These include environmental and occupational
health control costs, disposal costs, smelting and refining
costs. (Fountain 2013 Barrios et al., 2011)
Removal of arsenic impurity at an early stage of process-
ing is more advantageous compared to handling high arse-
nic wastes or extraction of arsenic from metallic product.