restricted areas underground, is a major
problem. Osunmakinde’s study identifies an
unstructured underground environment as
having the most potential of being exposed
to toxic gases. This is due to the various
mining activities that take place, which then
lead to an underground terrain that becomes
“restricted, unknown, unstructured, and
particularly dangerous owing to the presence
of poisonous explosive gases”. The study
highlights that toxic gases in mines not only
pose a threat to mine employees’ health, but
they are also bad for the environment and
can lead to reduced visibility underground —
another health and safety risk for the mines.
With nanotechnology, it is possible
to develop gas sensors with a premium
performance in respect to both sensitivity
and selectivity. “Selectivity meaning, even if
you were to have a mixture of gases — a good
mixture of gases — you can have a sensor
that will be able to quantify each one of them
separately,” Sikhwivhilu adds. He explains that
the device was fabricated using clean room
infrastructure with the aim of detecting a single
molecule of a gas, in addition to the smallest
concentration. “That’ll be just when there’s a
possibility that there could be a bad gas. You
get it before it even spreads into anything.”
The sensors will come in the form of an
electronic device. The chip for the device
has already been developed. For this device,
several entities were involved to put together
a device based on a single nanowire. “In the
event where we are using wires for some of the
semi-conducting materials, we try and isolate a
single wire which you can’t even see with your
eyes.” Thanks to state-of-the-art equipment, it
is possible to isolate it and make a device that
is based on a single nanowire. “Hopefully that
will change the landscape of mining activities
in the country.”
Mwakikunga explains that during mining
activities, many nanoparticles are emitted.
He says that nanoparticles are not created
in the labs but already exist naturally. When
nanoparticles are emitted, they have an impact
on mine employees. Vehicles transporting
minerals also emit nano carbon particles.
“Nanotechnology, understanding how these
particles behave and how they impact the
people that work around there, is crucial to
the lifetime of the mines and the people that
work,” he says.
It must be noted that the breath analyser
can also be employed as a gas analyser. The
prototype gas/breath analyser has two input
ports: one for human breath and the other for
ambient air. “It has already been employed in
Mining in focus
The CSIR’s scanning breath analyser.
Top right: The final pocket-size scanning breath analyser could potentially be integrated on a mobile phone.
2017/18, in collaboration between the CSIR
and the Mine Health and Safety Council,
to detect diesel particulate matter (DPM) in
the mines as well as the following noxious
gases: nitrogen dioxide (NO2), ammonia
(NH3), carbon monoxide (CO), and hydrogen
sulphide (H2S),” adds Mwakikunga.
During his presentation at the workshop,
Professor David Motaung, principal researcher
at the CSIR and an affiliated associate
professor in physics at the University of the
Free State, mentioned that most of the gas
sensors currently available on the market
require maintenance at least every six months.
He also singled out methane as one of the
problematic gases in the mining industry.
With nanotechnology it is now possible to
produce sensors that are smarter and
that can save lives. “What we have managed to
do so far, was to make sure that we produce the
nano sensors of the gas sensors that can operate
at very low temperatures,” Motaung said.
Professor Gugu Mhlongo also gave a
presentation at the workshop, pointing out
that the Department of Environmental
Affairs was monitoring industries that are
major contributors to carbon emissions —
the mining industry being one of them. She
also referred to a fatal gas leak at a Pakistani
coal mine in 2011. The leak was caused by a
methane exposure. Closer to home, there have
been several mine disasters involving leakages
of toxic gases underground. “A good sensor
must be highly stable, reliable, and show high
sensitivity and selectivity,” Mhlongo said.
Water treatment technologies
Nanotechnology can also be used to treat
contaminated water, which can then be reused
or recycled. Sikhwivhilu mentioned two types
of water treatment technologies: membrane
technology and adsorbents.
Groundwater is often encountered during
mining activities. This water is extracted from
the mine using dewatering pumps. It is not
always possible to reuse the ground water
extracted from the mine for other activities
because of the water being contaminated. “You
are looking at things such as lead, chromium,
and many other heavy metals. These are
typically poisonous to human beings, so a
certain concentration will act as a poison,”
Sikhwivhilu says.
With nanotechnology, membrane
technology, which ranges from ultrafiltration
to reverse osmosis, has been developed to
treat all types of contaminants in water
from the mines. The membrane technology
is able to remove even the most stubborn
contaminants from the water. This is done
through smart membranes that can segregate
small irons and trap them, leaving clean
drinkable water. The technology also allows
for mine water to be treated to a potable level,
for agricultural uses.
The second water treatment technology
involves using adsorbents. With an adsorbent
it is possible for entities to attract something
and allow for it to stick firmly to its surface
so that it doesn’t move freely. “If there are
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