GOLD EXTRACTION_proof 26/07/2016 10:29 Page 7
GOLD EXTRACTION
The Intec pilot plant at Monument Mining’s
Selinsing gold mine in Malaysia
“The process can be run without the use of
cyanide for projects where this is a particular
advantage, or can be combined with conventional
technologies for efficient gold recovery with
minimal technical risk.”
In the second quarter fiscal 2016 the first trial
pilot plant run was successful in achieving
"steady state" for seven days where various
parameters were tested using different sulphide
feed stock materials drawn from selected ore
samples in Buffalo Reef.
It was the Conceptual Study: Use of the Intec
Process as Pre-Treatment Step to Conventional
Cyanidation of Buffalo Reef Concentrate
completed by DCS Technology in February 2014
that indicated that the Intec Technology, among
other alternatives, may provide an economic
solution to treat sulphide materials through
Monument's Selinsing gold plant and for other
gold projects.
In February 2015, the company acquired an
interim licence from Intec International Projects
Pty Ltd, under which Monument has the right to
exploit and test the Intec Technology in respect
of both copper and gold processes, and to use
the Selinsing plant as an alpha site.
74 International Mining | AUGUST 2016
The Intec test work
is a four-stage
program including
laboratory trial test
work, the pilot plant
trial test work,
building a
demonstration plant,
and building a
commercial plant.
The second trial of
the pilot plant is
planned for the
fourth quarter to test
the response of ores
containing varying
amounts of pyrite
and arsenopyrite
using sulphide ores
from Buffalo Reef. It
will allow the effects
on overall gold
recovery of sulphide
pre-concentration by
flotation methods to
be compared with the
first trial on gravity
concentrate. The
second trial will be
carried out following
recommendations by,
and in agreement
with Orway Mineral Consultants, engaged by
Monument to oversee and report on the pilot
plant operation.
During the third quarter, metallurgical drilling
for the Intec Project comprised of 14 RC
pre-collar drill holes for 1,107 m and 19 DD drill
holes for 1,901 m across Buffalo Reef South,
Buffalo Reef Central and Felda Land to collect
representative ore samples for the second pilot
plant run. Those samples have been
concentrated by flotation and will be fed into the
pilot plant for testing in the fourth quarter. The
results of this second pilot plant run were
anticipated to be available in July 2016 for Orway
to complete economic analysis of the Intec
technology based sulphide gold recovery process.
The economic analysis will be incorporated into
an updated NI43-101 technical report.
Ian MacCulloch, Managing Director at
Coomooroo Explorations reports that “for some
time, Leslie Thompson of Pintail, Denver,
Colorado and I have been researching and
conducting trials on the use of bacteria to
beneficiate both ferrous and non ferrous metals.
This work has had two approaches with one
being the direct reduction of ferrous and non
ferrous metals and the second approach has
been the removal of gangue minerals from ores.
This capacity has been created as a byproduct in
researching the removal of silicates from
refractory gold ores to then enable the follow on
dissolution of gold from these complex ores.
“Pintail has already been able to form goethite
along with copper supergene minerals such as
native copper and chalcocite from mine water
waste. This trial was witnessed by the Denver,
Colorado office of the USGS and formed the basis
of a feasibility study on the remediation of the
severely contaminated groundwater at the
Summitville mine, Colorado.”
Pintail has also been able to create elemental
chromium from chromium contaminated soils
sampled from the banks of the Clyde River,
Glasgow. Here the aquifer results for soils and water
can reach 30,000 ppm Cr. The bacteria are capable
of functioning normally in a very toxic environment
and producing lumps of chrome metal.
Direct reduction of arsenic has also been
achieved from other sites. In other mine waste
studies such as at McCoy Cove, Nevada, Pintail
has been able to lower the soluble metal load to
almost zero for transition elements
(USAEPA/McCoy Cove sponsored trials).
Pintail has treated up to 8 Mt at a time on
spent gold ore heaps. Treating large amounts of
iron ore for either upgrading or for on site direct
reduction is therefore not an issue as the
methods of creating large volumes of bacteria at
the right concentrations under non sterile
conditions have already been undertaken.
Future innovations
The CSIRO has begun early discussions with
industry for the development of a new goldprocessing technology. The concept hopes to
build on the patented technique developed by
the agency for recovering gold without the use of
cyanide.
The novel gold recovery process replaces
cyanide with thiosulphate – a non toxic chemical
– helping to reduce the risks and environmental
impact of gold processing operations.
Canada’s Barrick Gold is the only gold miner in
the world using thiosulphate to recover gold at
its Goldstrike operation in the US.
Thiosulphate is effective at dissolving gold in
leach tanks to create a gold-thiosulphate
complex. The gold-thiosulphate complex can be
recovered using ion exchange resins in what has
traditionally been a challenging process. Working
to improve this separation process, the CSIRO
researchers discovered that adding sulphite to
the solution used to remove the gold from the ion
exchange resin enabled easier separation.
The CSIRO process can be tailored for treating
high-grade gold concentrates, and is also
valuable for use in other applications. For example,
in-situ leaching in deep mines and for use in
treating ores that contain carbonaceous material or
those with high cyanide-soluble copper.