Mining in focus
It does however require the application
of adequate water management and
cyanide management plants, particularly
descriptions of how cyanide-
containing solutions and slurries
are to be handled, stored, contained,
and monitored, and in many cases, a
plan will also include a description
of treatment plants used to remove
cyanide from solutions or slurries.
According to a recent article written by
Martin Sadongdong in the Philippine
newspaper Manila Bulletin News, a
Singapore-based firm introduced a new
environment-friendly way of mining
through a powder solution in lieu of
toxic cyanide to extract gold and other
precious metals.
Zack Ho Xuan Yi, managing
director of a company called Perfect 9,
said in an interview with Sadongdong
that he has developed a new powder
solution, called P9 Au-568, that can
be used to replace cyanide. From tests,
Yi said that they realised that the
powder worked, along with the benefits
of it being faster, a higher extraction
rate, and being non-toxic to people
handling it.
Aside from being environmentally
friendly as it incorporates a non-toxic
process, Yi claims that the powder
solution can increase the gold
extraction rate up to 90% and is four
to eight times faster than the current
extraction method being used. “It
literally takes seconds to extract gold
from an electronic chip,” said Yi.
Future developments
Research continues on the
processing of gold, with the focus on
becoming more cost-effective and
environmentally friendly. Thiosulfate
and alpha-cyclodextrin, a substance
commonly extracted from corn starch,
respectively, are researched to process
and recover gold. Thiosulfate and
bromide are used to leach the gold, in
a similar way to cyanide, whilst the
alpha-cyclodextrin is used in a similar
fashion to carbon to recover the gold.
Work is also being done using
the amino acid glycine to extract
gold. Glycine is manufactured from
by-products of the natural gas industry.
It forms a stable soluble complex
with gold, which is soluble in water.
Technical-grade glycine is cheaper than
cyanide and available in roughly the
same quantities. It is used in a similar
[22] MINING MIRROR APRIL 2018
Miners in the Philippines exposed to cyanide, used to liberate gold.
manner to existing gold refining
processes such as CIL and CIP, while
it also eliminates toxic waste disposal
problems. The opportunity exists to
recover and reuse the glycine, lowering
the net costs. Amino acids need to be
heated to 40–50°C to dissolve gold,
thus reducing the energy requirements
for such a process. In sufficiently
warm underground environments, the
process could be applicable to solution
mining, where solvents are injected
into an ore body and recovered along
with the gold from a central borehole.
Future applications are aimed at in
situ heap leach extraction projects
— a process that is expected to make
mining low-grade deposits in remote
locations more viable. Being an
alkaline compound, it is well suited to
extracting gold in alkaline ores such
as dolomite, unlike sulphuric acid.
Another upshot of this method is that
the ores treated in this way require no
milling, reducing energy consumption
and associated costs.
As civilisation progresses
through the 21st century and
global population numbers grow
exponentially, the demand for water,
energy, food, land, and other natural
resources significantly increases.
Therefore, no matter what gold
recovery process is eventually
adopted for a mining business, all
stakeholders and the industry need
to be sufficiently responsible to
protect the environment, reduce
energy consumption, manage costs
responsibly, and forever find ways
to recover, re-use, and recycle waste
material produced. b
Environment friendly cyanide