Precious Metal Refining: Platinum From the Road

Abstract:
In this experiment, we go over the possibility of finding platinum along highways
through methods of metal refining and extraction. Since catalytic converters contain platinum,
we assumed that the platinum would be lost from the converter as you drive your car and most of
the platinum would end up on the side of the road. To initiate the experiment, we would collect
everything by the road and begin filtering and extracting the possible platinum out of the sample
with the use of heating and oxidation. After filtering the sample, we found small amounts of
platinum which may not be completely pure but with a big enough sample, we can conclude that
there is platinum present at least.

Introduction:
This experiment is conducted on a highway which has an approximate 10,000 cars that
drive it every day. Assuming that every 100,000 miles the converter loses half its platinum it is
possible that most of it is found on the side of the highway. In theory, over one mile stretch of
road every ten days, the 100,000 miles is reached and that half the platinum from the converter is
lost on the road. Which is why we believe that taking a sample from the side of the road may
yield platinum even though some of the platinum will most likely not be on the road as a result
of being dispersed.

Materials and Methods :

Materials:
• Sample
• Broom
• Furnace
• Sifter
• Crucible
• Sodium Carbonate
• Borax
• Lead oxide (with a little flour)
• Bone ash pot
• Oxy-map torch
• Scale
• Beaker
• Aqua Regia
• Ammonium chloride
• Sodium chlorate

Method:
To begin, after taking a sample from the road by sweeping and transferring into a bag, the
sample will initially contain larger objects like gravel, rocks, cigarette butts, and tire pieces. We
begin filtering the larger pieces from the dirt by using a sifter to get the smaller objects separated.
The platinum should be in the smaller pieces as the platinum particles are incredibly small and
will be mixed in with the other finer particles like ground-up concrete. After filtering we will do
a fire assay on the finer particles mixed with a flux containing sodium carbonate to dissolve the
rock dust. Next the borax is used to thin out the liquid and some lead oxide will be added and it
will react with the flour and oxygen. This will cause the lead oxide to form lead metal which
ultimately will dissolve the platinum and move it to the bottom of the crucible. Afterwards, we
put the sample into the furnace to dissolve and once done we are left with lead slag which will
contain the platinum inside. Afterwards, we put the lead back in the furnace on a bone ash pot
without the oxide coating to allow it to oxidize. The precious metal should not oxidize and will
be leftover as a bead at the end. In order to remove the last bits of lead on the bead to get the
shiny look, we will torch the bead at a higher temperature than the furnace with a oxy-map torch
which will leave us with a pure bead of metal. From there we use a couple drops of Aqua Regia to
dissolve the metal which will change the color of the liquid red proving it’s not silver as it
wouldn’t react at all. We take the solution out with a pipette and precipitate the platinum out
after evaporating the nitric acid by adding ammonium chloride which result in platinum
precipitate.

Result:
At the end of the experiment, we concluded that the platinum bead was not completely
pure and most likely contained half the amount of platinum in comparison to the bead prior. This
is proven after we dissolve all the other materials and are left with just the precious metals
meaning platinum and other precious metals are present.

Discussion:
From the beginning of the experiment, we assumed that there would be a lot of platinum
along the highway considering how many cars pass in a day and how much platinum is on newer
versions of catalytic converters. By collecting a large enough sample to filter and refine, I
believed that the experiment could result in a pure bead of platinum based on prior assumptions
and calculations in the experiment. After the experiment, although platinum is present, the
resulting bead was not completely platinum and after extracting the precipitate it was very
different from the bead we got from the furnace. Most of the other metals present were most
likely silver, iridium and ruthenium. Another aspect could be that the sample size used for the
experiment was much smaller in comparison to all the sifted dirt collected so maybe with a
bigger sample size a purer bead could be refined. After calculating, 6.7 grams per ton of sifted
dirt is the approximate value and is a reason I believe a larger sample size would be more
beneficial but more time consuming as well.

Conclusion:
With the end of the experiment, it turns out that the bead of precious metal at the end is
not completely platinum. The importance of this is to determine whether there would be anything
meaningful from gathering a much larger sample. Yet once we dissolve the bead and precipitate
out the platinum, the amount precipitated is much less than the original bead which means that
there isn’t much to extract and if extracted it would not be pure. This proves my hypothesis
incorrect that the final result would be a pure bead of platinum. Although there could be various
factors that affect this like the sample size, if it was larger we could’ve reached a more accurate
value since the bead for this sample size was small and a larger bead to compare to the
precipitate would be more beneficial.

References:
Cody’s Lab. “Precious Metal Refining & Recovery, Episode 10: Platinum From the
Road.” YouTube, 28 May 2016,
www.youtube.com/watch?v=v5GPWJPLcHg&ab_channel=Cody%27sLab. Accessed 25
Sept. 2020.