CYANIDE REDUCTION/REPLACEMENT
Eleven test batches totalling around 2 t of a
previously announced 5 t test sample from the
3 Aces gold project, in the Yukon, resulted in
93.17% recovery of contained gold, yielding
132.23 oz of gold doré, using EnviroLeach’s
non-cyanide, water-based, neutral pH treatment
process
EnviroLeach signed with Golden Predator and
enCore Energy Corp that could see its proprietary
process become part and parcel of in-situ recovery
operations in the future.
The three have established Group 11
Technologies Inc to focus
“primarily on non-invasive
extraction technology
utilising environmentally
friendly liquids to recover
gold and other metals”,
they say.
“Group 11’s new
proprietary process has
been tested on high-grade
concentrates and is now
ready for market and
testing on further
applications, providing the
mining industry for the
first time with a
commercially viable,
sustainable alternative to
standard cyanide
processes and
conventional mining practices which often face
community opposition and require slow-moving
and expensive regulatory compliance,” they
explained.
EnviroLeach brings the proprietary water-based
leach technology to the company, enCore the
proprietary expertise in in-situ metal recovery, and
Golden Predator the proprietary mobile recovery
unit, SRU.
This agreement takes the environmentally
friendly nature of the EnviroLeach process to a
whole new level, according to EnviroLeach
President and CEO, Duane Nelson.
“This application has the potential to change
the way the world mines,” he said. “It has the
potential to unlock the value of deposits in
environmentally sensitive areas and it could also
provide a viable solution for thousands of smaller
deposits worldwide that don’t justify the capital
expenditure of current conventional mining
methods.”
Leikam concluded on EnviroLeach: “Disruption
is difficult to achieve. EnviroLeach has proven
through test programs it has an industry changing
solution. Now the company has to validate it on a
commercial scale.
“The opportunities seem to be obvious;
industry adoption is the next step.”
CLEVR alternative
EnviroLeach is not the only company to have come
up with a cyanide alternative for metallurgical
extraction of gold.
Dundee Sustainable Technologies’ (DST) CLEVR
Process™ uses no cyanide and produces no toxic
liquid or gaseous effluent, according to the
company.
The process uses sodium hypochlorite with a
catalytic amount of sodium hypobromite in acidic
conditions to put the gold into solution. “Contact
time is short and the process operates in a closed
loop,” DST says, adding that all chemicals are
recycled within the circuit and sea water is
suitable where available.
The primary benefits of the technology,
according to DST, are:
n A short processing time (one to two hours);
n Efficient gold recoveries;
n A closed loop operation (no liquid effluent),
thus eliminating the need and environmental
liabilities associated with tailings pond;
n Produces a dry stacked, inert and stable
cyanide-free tailing; and
n Treats refractory ores and handles base metals.
The technology recently hit a new milestone,
with results from metallurgical testing on
mineralised samples from a Top Tier gold producer
achieving extraction yields of up to 95.6% with the
help of the CLEVR Process.
DST received a circa-10 kg sample of material
from an operating gold mine in South America,
with the company mandated by the producer to
conduct a metallurgical test program at its
facilities in Thetford Mines, Canada. The objective
was to define and quantify the gold extraction
amenability of the CLEVR Process on the provided
material.
In May 2020, DST completed the metallurgical
test program and said the direct application of the
CLEVR Process on the producer’s sample achieved
gold extraction yields of up to 95.6%. Given the
low sulphide concentration of the sample, no
10 International Mining | JULY/AUGUST 2020