Gold is an important metal throughout
history we have adored it this jewelry
and valued it is currency nowadays we
are increasingly relying on it in some
medicines and notably and circuitry in
the contacts of modern electronics and
you can eat gold it even has an e number
but where does gold come from gold is
found naturally in rocks and doors but
only in a few places around the world
around 3000 tons of gold was mined in
2017 with China the US and Australia
being the major contributors even then
gold is found alongside other metals and
in really low concentrations you can
only get up to a gram of gold out for
every ton of rock mind this is a problem
we go to extraordinary lengths to get
the gold to each letter 90% of the
world’s gold comes from mining processes
that reach crushed rocker or with large
quantities of notoriously toxic cyanide
though these processes may allow for the
separation of gold from the rock through
accidental leakages and blatant dumping
of hazardous material cyanide reaches
local water supplies this has a
devastating effect on the local
environment for wildlife and workers in
fact the use of cyanide makes gold the
most toxic metal to produce we also use
incredible amounts of energy and
resources mining and processing tons of
rock to get just a few grams of gold out
to get gold from crushed rock into gold
ring requires many energy intense steps
including physical mining crushing
storing transporting separating refining
and many many more metal production in
general demands 10% of the world’s
energy supply and also produces
significant quantities of carbon dioxide
and other harmful emissions mining
processes in general also produce a lot
of waste and I’d like to give you a
sense of scale of this this is the
superpet gold mine formerly Australia’s
largest opencast gold mine producing 28
tonnes of gold a year
this single mine is one and a half
kilometres wide three and a half
kilometers long
and two and a half kilometers deep this
can be hard to visualize for a single
mind so here’s some perspective you
might be able to make out a single speck
on one of the roads in that pit that’s
actually a dumper truck like this one
that transports crushed rock from one
site to the next how big is that dumper
truck well here’s a worker standing next
to one these mines are vast think of how
much gold we get out of these mountains
compared to how much rock we’ve had to
displace the vast majority of which is
simply disposed of in fact it can take
20 tons of rock to make that one gold
ring this is the severe and detrimental
impact we have on the environment given
our reliance on gold it is important for
us to look to other sources of the metal
and for more efficient metal recovery
processes so we need a better solution
from one tonne of rock you can get up to
a gram of gold but you can get 300 grams
of gold from one tonne of mobile phones
as there’s much more gold in circuitry
than rocks it’s much more efficient and
environmentally friendlier to recycle
gold from waste electrical and
electronic equipment called we instead
of – think of how many phones you’ve had
in your lifetime nothing of what’s
happened to those phones when you got a
new one maybe you gave it to someone
else to use
maybe he threw it in the bin maybe is in
that drawer at home but how many were
recycles in the EU less than 20% of we
is recycled the vast majority of waste
electronics are sent straight to
landfill so you might be thinking well
how much gold is actually in my phone
what’s the point in recycling it the
phones we value so dearly have around 30
milligrams of gold in them are about 85
pence worth this might not seem like a
lot so if I was to gather everyone’s
phone in from this audience of 700
people or so then we’d have 21 grams of
gold are about six hundred and thirty
times worth enough to buy two-thirds of
this might not seem like the best deal
so how about this globally 40 million
tons of weed is sent to landfill every
year this is an urban goldmine in gold
alone this is worth nine billion Pines
if we were to include all the metals and
waste electronics we sent to landfill
this goes up to 22 billion pounds and
this is only set to rise as the sales of
electronic products and therefore amount
of electronic waste is increasing every
year so recycling goes from we really as
a golden opportunity we can minimize our
impacts on the environment by maximizing
the use of metals we already have but we
has many metals in it and gold is not
the most abundant one end there how do I
get gold out of your phone this is where
my research comes in I’m a chemist and I
investigate chemical methods for the
recovery of metals without having to use
toxic reagents I said metals are found
in low concentrations and alongside
other metals so we need some way to
separate and concentrate them one common
way of doing this is to use a technique
called pyro metallurgy which essentially
involves melting the metals out of your
products but this requires a lot of
energy high temperatures and could be
really highly polluting one more
efficient and cleaner way of separating
metals on an industrial scale is to use
a technique called solvent extraction
which has two liquids we can dissolve
all of the metals out of your phone and
into an acidic water solution this gives
us a mixture of metals including iron
and copper platinum and gold which is
the most valuable to recycle the other
liquid is an oil which sits on top of
the water and doesn’t mix into it much
like olive oil sits on balsamic vinegar
I design molecules called extractant
that transport the metal of choice out
of the water and into the oil if we can
do this selectively then we can separate
gold from the mixture this is a sort of
molecular level gold panning
we’re sifting through all the metals in
the mixture and only collecting the one
that we want so how do we get selective
gold separation
every metal in the water has a certain
size likes to form certain shapes has a
certain charge basically has a preferred
chemistry for example gold likes to form
flat squares platinum likes to form
octahedral
I designed molecules that can
discriminate between the metals based on
these features bind to gold and only
gold and transport it into the oil this
selectivity is a bit like the child’s
toy where you can’t get the round peg in
the square hole my molecules are
particularly efficient not only do they
recognize gold squares they transport
multiple at once as molecular at golden
nuggets this gives us more metal outs
from less commercial used we can then
separate off the gold containing oil and
treat it to give us back the gold we
treasure in an overall more efficient
and less damaging process compared to
traditional mining methods this is what
it looks like on the small scale in the
lab we taped your mobile phone and
dissolve it in the acidic water solution
to get what we like to call mobile form
solution for interest the supreme
solution is 10 forms per liter we
contact that mixture of metals with the
colorless oil that contains the
extracted molecules we mix the two
liquids together and as those two
liquids separate we see we see gold move
from the lower mixture up into the oil
achieving saturation we can then
physically separate those two liquids
and treats the oil and a couple of steps
to give us back the gold metal so how
does all of this fit into the bigger
picture what we’re trying to do is help
close the loop and help create what’s
called a circular economy that means
after going through all the effort of
getting our metals in the first place
instead of throwing our products away at
the end of their lives we should be
aiming to recycle as much as possible to
make the most of the metals we already
have to the benefit of the economy the
environment and society know this might
make it look like we’ve solved the
problem we can get gold out of your
phone and busted are many advantages to
recycling metals and gold from we that
are still some challenges we have to
address we need to work with scientists
and engineers to make sure we can deal
with bulk volumes of ever more complex
wastes we need to work with governments
and businesses to make sure we have the
info
structure incentives and framework in
place to be able to collect enough waste
to process it and dismantle it
efficiently because ultimately the value
of what we recover has to be greater
than the cost of recovering it we need
to work together to actively choose to
recycle we so that we can still have
access to metals that don’t cost us the
earth right back at the start I asked
where does gold come from
I’ll repose the question where should
gold come from the answer is we because together we are golden thank you