today we're gonna be processing a little
bit of gold from scrap computer parts a
lot of computer parts are plated with a
small amount of gold and with a little
bit of chemical treatment we can isolate
it the profitability of this endeavor
depends entirely on how cheap we can get
the chemicals and the computer scrap the
prices of the chemicals are pretty
consistent but the cost of the scrap can
vary greatly ideally you want to pay the
least for the most gold content but
getting good deals takes a surprising
amount of knowledge and research the
amount of gold in computer scrap varies
greatly and it depends on a lot of
things like the manufacturer the year of
production the particular part etc if
you really want to cut a profit by
processing the computer parts you really
have to know what you're paying for I'm
personally not even close to a master at
gold recovery so I made some bad
purchases and you'll see in the video
that I didn't even get close to breaking
even in this video the computer parts
that I'm getting the gold from are known
as printed circuit boards or PCBs for
short we could also get gold from things
like computer processors or connectors
but I decided I would stick with just
the PCBs the procedure for pretty much
all of the computer pieces is exactly
the same so I felt it would have been
redundant if I just kept repeating the
process in general there's three major
steps to recover gold from computer
scrap the first thing that we need to do
is to separate the gold from the circuit
boards by dissolving the metal that the
gold is plated on this step results in a
mixture of gold flakes and a bunch of
other debris so the second step is to
purify the gold in this second step we
selectively dissolve the gold and leave
behind pieces of circuit boards plastic
etc the three main ways to dissolve gold
is to use cyanide aqua regia or a
mixture of bleach and hydrochloric acid
at the time of making this video I
didn't have any cyanide so I didn't
include this but I do plan to
demonstrate it in the future the third
step is to precipitate the gold from a
solution and to recover it as a gold
powder there are a few ways to do this
but I'm going to use the meta bisulfite
method the
because I think it's one of the cheapest
and easiest ways after the third step we
do have an optional fourth step and that
is to melt the gold powder into a solid
piece
okay so these are the basic chemicals
that are needed to recover the gold for
step one the part where we separate the
gold from the boards we need three
percent hydrogen peroxide concentrated
hydrochloric acid and the computer scrap
for step two the part where we dissolve
the gold into solution we'll use
hydrochloric acid but we have an option
of either using nitric acid or bleach
depending on how we want to do things in
the last and final step where we
precipitate our gold from solution we
have our sodium metabisulfite the
computer scrap that we use here doesn't
really matter and it can vary greatly in
shape or form for this video I decided
to separately process PCBs from two
different sources so that I can compare
the yield that I got from each of them
at the end of the video I will also
process some gold that was sent to me by
a fan named Robert Bradbury Robert is
the one who actually suggested I'd make
this video and he sent me some free gold
so a big thanks goes out to him
to start things off I add the first
batch of computer boards to a 1 liter
beaker before adding it to the beaker I
weighed everything and it was advertised
to be about a pound and it actually came
out to be a little bit more than this at
around 472 grams it's pretty easy to see
here that some of the boards are too
long for the beaker so we're gonna have
to cut some things
most of the long pieces only had gold at
each end and there was no gold in
between so I simply just cut off the
ends and discarded the middle part
some of the longer pieces actually had
gold over the whole length of them and
for these I just cut them in half and
saved everything just after a few
minutes of cutting I was left with
mostly moderately sized pieces and I was
ready to move on what we need to do now
is separate the gold from the boards and
to do this we use a mixture of hydrogen
peroxide and muriatic acid the typical
ratio and the one that I'll be using is
a ratio of two to one
muriatic acid to hydrogen peroxide it's
really not important to measure things
out exactly and they just have to be
mixed in rough proportions I wanted to
have a total volume of 800 milliliters
so I pour it in about 250 milliliters of
the peroxide and just top things off to
800 the peroxide muriatic acid solution
is then poured into the beaker
containing our computer pieces the
moment that our solution is added you
can see that it starts to change colors
and there's visible bubbling occurring
we leave it here for several minutes and
over the course of something like an
hour it slowly takes on a darker and
darker green color
what we're trying to do here is separate
the gold from the boards by dissolving
the metal that the gold is attached to
most boards have a base layer of copper
which then has nickel plated on top of
that and then gold-plated on top of the
nickel muriatic acid alone is not strong
enough of an oxidizer to react with
either the nickel or the copper and this
is why we had to add the peroxide in the
presence of an oxidizer like hydrogen
peroxide or oxygen gas the reaction
occurs and we can dissolve both the
copper and the nickel even in the
presence of the hydrogen peroxide the
reaction is still pretty slow so the
general procedure is to leave things for
a week and to occasionally stir it even
though it's only been something like two
hours when we stir things around we can
see that some gold has already been
separated from the boards
to add more oxygen to the mixture and to
keep things agitated and mixed we can
use an aquarium air bubbler these things
are pretty cheap and you can probably
get it for something like ten to twenty
dollars but before you use it you're
gonna have to make a few adjustments the
bubbling here is a little bit too wild
the first thing that I did was I made a
few cuts in the hose to try to make it
so that all the air wasn't pouring at
the front and some of it can move out
the side to keep the tube fixed of the
beaker and to prevent it from flying
everywhere I just used a large piece of
tape I don't show it here but when I
want to run things it was a little bit
better but the airflow rate was a little
bit too high still to limit things
further I used one of my clamp holders
to pinch down on the tube and to
restrict the air flow when we turn
things on now we can see that the
bubbling is much cleaner and just to
prevent splashing I cover the top with
some plastic wrap it is very important
though not to completely cover the top
with the plastic wrap because we are
pumping air into the beaker after about
a week things should be done so we get
rid of the air bubbler and the plastic
wrap that's on top the contents of the
beaker are then poured into a basic
kitchen strainer the beakers washed a
few times to get all the gold out of it
and then this is poured on top of the
circuit boards when we take a look at
the beaker below the strainer we
consider I've used way too many water
washings you can also see a lot of the
gold flakes that we've separated from
the PCBs and for now we put the solution
to the side what I do next is I place
the strainer over another Bowl and I
manually wash all of the PCBs using a
squirt bottle this step is done to wash
away any loose gold flakes that might
still be there and to also find the PCBs
that still have gold attached to them
all of the boards that have been
completely cleaned can be disposed of
but the ones that self gold can be
included in future batches anyway after
several minutes of washing we get pretty
close to being done in the end almost
all of the boards were completely
stripped of their gold and there was
just a few left over that had a little
bit of gold left on them after the
strain is removed you can see that we're
left with a small amount of gold at the
bottom of the bowl going back to our
beaker with our gold flakes in it I
mixed it around to get a uniform mixture
and now we're ready to filter it
I use a doubled up coffee filter in a
plastic funnel and I slowly filter
everything through
some of the larger gold flakes have a
tendency to sink to the bottom of the
beaker so before I pour things I mix
everything up we're gonna be filtering
through a few liters of liquid here so
it's gonna take a little bit of time as
we filter more and more a decent amount
of gold starts to build up at this point
I filtered the last of our greenish
liquid and I do a couple final water
washings just to get all of the gold out
after all of the gold and the greenish
liquid have been washed out of the
beaker I swap out the container that's
below the filter once the container
swapped out we can start filtering the
stuff that we washed out of the strainer
the water that we're filtering here is
much cleaner and this is why we swapped
out the container below the filter all
of the green water that we first
filtered through is contaminated with
metals and it needs to be disposed of
properly the second portion is nearly
pure water so it can be simply poured
down the drain and if we combine both we
would just be increasing the amount of
waste that we have to dispose of
eventually everything is transferred and
I use a wash bottle to try to get as
much gold as I can to the bottom I let
it sit for a while for the water to
slowly drip out and this is what we're
left with I open up the filter paper
here to show we have and it does look
like we have a nice chunk of gold the
volume here is very deceiving though and
it looks like we have a lot more gold
than we really do the flakes of gold
don't pack very well so it looks like
there's a bigger volume and also there's
a lot of bits of plastic and other
things present I move things around with
a spatula and I get the gold on the
front so you can see what's really
happening in the next step
what we have to do now is dissolve the
gold and there's two main methods to do
this the first is by making something
called aqua regia and the other is by
mixing hydrochloric acid and bleach I'm
going to first show the aqua regia
method and the first thing that we do is
we try to cover everything with
hydrochloric acid
aqua regia is made by mixing
hydrochloric acid with nitric acid in a
ratio of about three to one so since it
looked like we had about 50 mils of
hydrochloric acid here I added 15 mils
of nitric acid it's important to note
that as long as you're near the
three-to-one ratio you should be fine
it really doesn't have to be super exact
at first it doesn't really seem like too
much is happening but after we leave it
for a little bit with occasional
stirring eventually all of the gold does
dissolve while we wait for things to
dissolve I'm gonna get into a little bit
of the details on how it actually is
dissolving the gold if we were to use
either of these acids alone it really
wouldn't do very much hydrochloric acid
alone pretty much does nothing but
nitric acid alone is able to transiently
oxidize an almost undetectable amount of
gold the reaction between nitric acid
and gold is in equilibrium and almost
immediately after the gold is oxidized
it turns back into metallic gold when
the acids are mixed though we can
actually dissolve gold pretty easily
when combined the nitric acid will still
oxidize very small amounts of gold but
this time the oxide doesn't revert back
to metallic gold almost as soon as the
gold ions form they react with the
chloride ions from hydrochloric acid the
reaction between the gold and the
chloride leads to the formation of very
stable chloro or eight anions by
sequestering the oxidized gold ions were
breaking the original equilibrium that
we had between the gold and the nitric
acid and the gold slowly dissolves in an
acidic solution the chlorate anions are
associated with a hydrogen and this is
known as chloroauric acid the
chloroauric acid is our final product in
this reaction and it's extremely soluble
in water
once all the gold has dissolved we'll be
left with a nice yellow solution
the gold solution is then filtered
through a coffee filter all of the gold
solution slowly filters through and our
original beaker is washed with a little
bit of water
the contents of the coffee filter is
then repeatedly washed with distilled
water to try to get it as much gold as
possible
Goldin solution will have a slight
yellow color so we'll know we're done
washing when the stuff that filters
through is colorless eventually it
looked like we were just filtering
through plain water so the filter was
removed
to our gold solution I then add a
heaping spoonful of sodium metabisulfite
the sodium metabisulfite quickly reacts
with both the nitric acid and the
hydrochloric acid to produce sulfur
dioxide gas this gas is very irritating
and toxic so it's extremely important
that this is done in a well ventilated
area some of the sulfur dioxide will
react with gold ions dissolved in
solution and it will produce metallic
gold the reaction doesn't appear to
occur immediately but upon standing for
a little bit it starts to darken as the
metallic gold precipitates out we
eventually reach a point where the
solution doesn't get darker and it looks
like all of the gold has precipitated
out when I let things sit there for a
while the gold should slowly sink to the
bottom now when I swirl things around
all of the gold should accumulate in the
center of the flask and when we look we
have a small clump of black gold one
stuff I didn't show here was the
stannous chloride test but I'm going to
show this later in the video
the basic purpose for this test is to
make sure that all of the gold is
precipitated and that there's no gold
left over in solution
to separate the gold we then have to do
another filtration but this time I use
proper filter papers and not coffee
filters
I found that the precipitated gold was
superfine and coffee filters really
didn't do a very good job catching it
even though the filter papers were a lot
better they still weren't perfect and a
small amount of gold still passed
through
anyway for now we'll let this filter
through and we'll get back to it in a
bit