CYANIDE REDUCTION/REPLACEMENT
Reduce or replace?
The ReCYN II plant at the
Martabe mine in Indonesia
will fit into the 5.5 Mt/y
circuit and treat around 1.2
t/d of copper, GreenGold’s
Peter Mellor says
As mining looks to clean up its act in the face of environmental
and social governance concerns, the use of cyanide is, again,
being scrutinised. Dan Gleeson looks at some technologies
eradicating or reducing its use in metal extraction processes
The mere mention of cyanide has, in the last
few decades, proven enough to push
economically viable mining projects off the
development slate.
There are enough stories about cyanide
management gone wrong to turn communities
against mine developers at key approval stages.
This is on top of outright bans on the use of
cyanide in countries such as Germany, Czech
Republic and Hungary, and states and provinces
in North and South America.
For all the financial and operational benefits
that come with using cyanide, the industry
understands the lixiviant’s years are numbered.
This has been highlighted by a number of
companies exposed to the chemical making
concerted moves away from its use.
Competing with cyanide
EnviroLeach Technologies is helping facilitate
such moves, with the Canada-based company
coming up with a patented chemical compound
that, it says, is “superior” to cyanide and its
alternatives and comes with no negative
environmental impacts. In fact, the company
states the chemistry ingredients are FDA (US
Food and Drug Administration) approved for
human consumption.
The closed-loop process offers an almost zero
environmental footprint, with no off gassing, no
water effluent, and no landfilling of any waste
materials, according to the company.
Using its non-cyanide, water-based, neutral pH
treatment process, EnviroLeach extracts precious
metals from ores and concentrates using a
proprietary chemistry technology at ambient
temperature.
The process is effective on most gold ores and
concentrates, the company says, potentially
unlocking the value of many deposits located in
environmentally sensitive areas that cannot be
developed using conventional extraction
methods.
Jason Leikam, VP Corporate Development at
EnviroLeach Technologies, says the applicable
market for the company’s technology in mining is
vast, which has been proven in test work on reallife
ores and concentrates.
“The mining industry is ripe for disruption,”
Leikam said. “An increased focus on
sustainability and social licence to operate,
coupled with environmental and social
governance (ESG) and Impact investment factors,
all contribute to push a mandate for innovation.
“EnviroLeach is uniquely positioned for the
evolution of the industry. Our extraction process
is not only sustainable, but economically viable.
Applying our technology can reduce permitting
processes and improve project economics. That
means time and money for operators who are
subject to inherent cyclical industry risk.”
Back in February, the company released results
of EnviroLeach test work
carried out from 2019 field
testing at Golden Predator
Mining’s Secondary Recovery
Unit (SRU™) at its Yukon test
processing plant. The SRU is a
mobile batch recovery unit for
the recovery of gold from its
sulphide concentrate,
according to Golden Predator.
Eleven test batches
totalling around 2 t of a
previously announced 5 t test
sample from Golden
Predator’s then-owned 3 Aces
gold project, in the Yukon,
resulted in 93.17% recovery of
contained gold, yielding
132.23 oz of gold doré.
Recoveries improved as the tests advanced
with the final five test batches yielding an
average of 96.8% gold recovery, according to
Golden Predator and EnviroLeach.
Golden Predator said these results confirmed
processing and recovering environmentally
friendly gold from high-grade sulphide
concentrate can be achieved with greater
efficiency than cyanide.
EnviroLeach’s Leikam went a step further,
saying the efficiency and cost-effective nature of
the company’s technology meant it could put a
significant dent in the cyanide sector’s metal
extraction market share.
“EnviroLeach has demonstrated time and
again that our technology leach efficacy is either
comparable or superior to cyanide vat leaching,”
he said. “We achieve high recoveries and, in
many cases, are faster than cyanide.
“Our chemistry is also recoverable and
recyclable, which translates into chemistry cost
reductions over time. We are cost competitive
with cyanide vat leaching of gravity and flotation
concentrates.”
The more EnviroLeach test work carried out,
the wider the applicability and more favourable
the metal recoveries appear to be, with the
Golden Predator program demonstrating the
chemistry works well with arsenopyrite
concentrates, according to the company.
Leikam, on this development, said: “This can
be a game changer for many projects that are
otherwise unable to process concentrates with
high arsenic values. It broadens our applicability
to include an untapped niche market.”
Another case in point is the recent agreement
8 International Mining | JULY/AUGUST 2020