MINING CHEMICALS
as significant grades of gold and silver. Slag is
costly and problematic to retreat by conventional
process technology, so it tends to be indefinitely
stockpiled or sold off as a construction material,
reported Tim Newton and Frank Trask of Mining
and Process Solutions (MPS), Australia at ALTA
2017. In the paper The recovery of copper and
precious metals from smelter slags by alkali
glycine leaching, they explain that “alkali glycine
leaching technology offers a new approach to
retreatment of slag. Glycine can selectively
extract copper, gold and other valuable
components while ignoring iron-rich gangue
minerals. Metals can be recovered from leach
solutions by conventional downstream methods.
Glycine losses are minimised by recycle of barren
liquor to the leach circuit.”
Following a metallurgical test program, MPS
has developed a process to treat slag from a
South American operation. Test results and a
conceptual process design are presented in the
paper along with indicative capital and operating
cost estimates. Comparison with alternative
processes shows a strong economic basis for
further development.
Cyanide
In a paper, The RECYN process - changing the
negative public perception of cyanide, presented
at ALTA 2017, Malcolm Paterson of PT Green Gold
Engineering, Indonesia, noted that “cyanide is
firmly established in the gold mining industry as
the overwhelming choice of solvent for gold and
silver recovery from ores. Several niche
applications for alternative reagents have been
proposed, but it’s unlikely the superiority of
cyanide will be seriously challenged for some
time.”
On February 22 this year the International
Cyanide Management Institute (ICMI) re-certified
Orica’s cyanide manufacturing facility in Yarwun,
Australia as compliant with the Cyanide Code.
The facility was initially certified in November
2006.
Orica is a global leader in the manufacture and
distribution of sodium cyanide to the mining
industry and says it is “committed to delivering
and maintaining the highest standards for the
safe manufacture, transport and use of sodium
cyanide. In order to achieve compliance with the
cyanide code, Orica’s manufacturing plant was
audited by an independent organisation, finding
Orica to be in full compliance with the code.”
The International Cyanide Management Code
for the Manufacture, Transport, and Use of
Cyanide in the Production of Gold (Cyanide Code)
was developed by a multi-stakeholder Steering
Committee under the guidance of the United
Nations Environmental Program (UNEP) and the
International Council on Metals and the
Environment (ICME). The code is a voluntary
industry program for gold mining and services
companies, which focuses exclusively on the safe
management of cyanide.
With effect from January 1, 2017, ICMI
extended the Cyanide Code to include the
production of silver from primary silver mines
that use cyanide in the production process. The
producers and transporters of cyanide used in
primary silver production will be included in the
expanded program.
A primary silver mine is defined as an
operation where silver is the main commodity
produced. About 30% of the world’s silver
production comes from primary silver mines; the
balance is produced as a co-product from
polymetallic, base metal, or gold mines.
The gold industry’s implementation of the
Cyanide Code continued to expand in 2016, and
the program has had a net gain of 17 signatories,
a 9.5% increase over 2015. Through December
16, ICMI had accepted applications from 27 new
signatories in 2016, while 11 signatories left
during the year. The 196 signatories now
participating in the program include 46 mining
companies, 22 cyanide producers, and 128
transporters.
The new signatories in 2016 consist of three
mining companies and 14 transporters. With a
fourteen-fold growth in signatories since the
program’s 2005 launch, the Cyanide Code is now
being implemented in 51 countries on six continents.
The growth in certified operations has also
continued over this year with 23 certifications
and 50 recertifications announced by mid-
December 2016 . Initial certifications show that
the program continues to attract new
participants, while recertifications indicate the
ongoing commitment of signatory companies to
employ best practices for cyanide management.
During this year, the program also has reached
new levels of certified operations. By December
16, 269 of the 344 signatory operations (78%)
were certified – a new high – which reflects that
the Cyanide Code is now an established and
mature program. More than 48% of the total
operations participating in the Cyanide Code
program are recertified, and, notably, over 58% of
the gold mining operations in the program (77 of
133) have been recertified, which shows the
considerable efforts of signatories to maintain
continuous compliance.
Cyanide alternatives
Is alkaline glycine a contender for copper? asked
Mike Dry of Arithmetek Inc, Canada, at ALTA 2017.
Work is being done on the use of alkaline
glycine as an alternative to cyanide for the
extraction of gold and silver from ores and
concentrates. In particular, he noted: “the
indications are that, where copper is present,
alkaline cyanide may well offer lower processing
costs than conventional cyanidation. Another
avenue that is being investigated is the application
of alkaline glycine to the extraction of copper from ore
or concentrate containing copper sulphides.
“A recent review shows that when the copper
concentrate meets the requirements for smelting,
smelting remains economically superior to
hydrometallurgical processing. The same review,
however, also points out that copper concentrate
grades are declining, and that and increasing
share of the world’s copper production will not be
amenable to pyrometallurgy. At present, pressure
oxidation (POX) is the dominant
hydrometallurgical option, but several other
hydrometallurgical processes are under
development.
“A new hydrometallurgical approach to the
extraction of gold, silver and copper from various
sources has recently been proposed. This
approach uses alkaline glycine as the lixiviant,
and a fair amount of exploratory laboratory-scale
work has been presented.”
His paper presents an early-stage evaluation
of the process economics potentially associated
with the application of alkaline glycine to the
processing of copper sulphide concentrate that is
not amenable to smelting because of its high
arsenic content. This work uses process and
capital cost modelling to generate preliminary
generic financial models for two circuits:
n Conventional POX processing, in which the
sulphide is oxidised in an autoclave
n A circuit using the proposed alkaline glycine
chemistry.
The paper presents the results of a comparison
between the established technology and new
technology via preliminary estimates of the
capital and operating costs and simple cash flow
analysis leading to return on investment
numbers.
Molecular Recognition Technology (MRT)
Ucore Rare Metals has entered an option to
purchase agreement with IBC Advanced
Technologies, whereby Ucore has an option to
purchase the outstanding shares of IBC.
“This Option to Purchase Agreement is a major
milestone for Ucore” said Jim McKenzie,
President and CEO of Ucore. “IBC is already a
world leader in MRT for the mining industry, with
an existing customer base spanning several
continents and including majors such as Asarco
Grupo Mexico (USA), Impala Platinum of South
Africa, Tanaka Kikinzoku K.K. of Japan, Sino
Platinum of China and LS Nikko of Korea.
Remarkably, this initiative places us in a position
to assume and accelerate a business platform
that IBC has established over almost 30 years in
business.”
“IBC and Ucore offer a high degree of synergy
as a combined entity,” continued McKenzie. “IBC
JUNE 2017 | International Mining 13