WARNING: This video deals with open flames and high temperatures.
Work outside or in a fume hood and have appropriate fire safety protocols.
Greetings fellow nerds.
There are plenty of videos on youtube about recovering platinum
from all sorts of common goods like catalytic converters and jewellery.
The process usually involves dissolving the platinum and other metals in the item
with a mixture of hydrochloric and nitric acid known as aqua regia.
While this works very well for those items it's not very good for laboratory chemical waste.
So in this video we're going to go over why that is
and demonstrate a procedure for treating laboratory chemical waste so the platinum can be recovered.
So let's get started.
Here i am boiling down the chemical waste to remove most of the solvents in it.
Most chemical waste just consists of volatile organic solvents.
The laboratory i got this from used different types of platinum in their work
and after they ran their experiments they dumped them into this bottle.
Any laboratory that uses platinum compounds on a regular basis will have a bottle of precious metal waste like this one.
Once it got filled I swiped it for platinum recovery.
Now looking back boiling off the solvent is the absolute most idiotic thing i could have done.
For one, the solvents are flammable.
And two, releasing toxic chemical waste into the atmosphere has got to be some sort of environmental protection violation.
So if you're doing this sort of work distill off the solvents using a proper distillation apparatus
and dispose of the distillate properly.
Do not just boil it off like i am.
Ok i'm going to add in more chemical waste and continue boiling down, so i'll skip ahead.
And here is the concentrated platinum waste solution.
I've transferred it into this 100 mL round bottom flask.
Now we're going to set up a high temperature heating mantle.
I've shown how to make these in a previous video.
I've also put in a condenser column.
We're not trying to reflux anything,
but just prevent the sputtering and frothing of the waste from losing our valuable platinum.
Now we turn on the heating and slowly ramp up the temperature to four hundred celsius.
Giving plenty of time for the volatile components to boil out.
Here it is while it's heating up and you can see the syrup of platinum wastes boiling.
Here we are an hour in and the bubbling and sputtering has coated the inside of the round bottom flask.
Keep going until most of the volatiles have come off
and it's just refluxing with whatever high boiling substances remain.
When you're confident it won't sputter or overflow,
remove the condenser column to allow the fumes to escape
and the material to thoroughly dry out.
We want the material to be a charcoal like solid rather than a syrup.
It will take some time and a few hours of heating so be patient.
The reason why we're going through all this trouble is that we want a solid mass of platinum rather than a syrup.
A dry solid mass shouldn't pop or sputter when we incinerate it later
And here we go.
Now scrape it out and transfer it to a crucible.
If you've dried it enough then it should crumble and fall out fairly easily.
But if it's still sticky or syrupy then you'll need to heat it again higher.
And there we go most of the platinum waste is in the crucible.
I'm not going to bother getting out everything since i have more platinum waste to process
and so i'll just reuse this same flask for additional boiling and volume reduction.
Now take the crucible of waste and set it up for ignition.
I'm using a simple propane torch.
So you're going to need a good fume hood or to do this outside.
Since i want to minimize soot build up in the ducts of my fume hood i'm doing this outside.
Now just simply heat it up until it's glowing red hot.
Okay so why are we doing this.
First a bit of background.
Some labs use platinum in their work and while electrodes and platinum wire lasts years,
what most often ends up in the waste bottle are platinum catalysts.
These spent catalysts are often just used once or at most a few times before they are discarded to avoid cross contamination.
The platinum itself is often not in metal form
but incorporated into organometallic complexes where the platinum atoms are surrounded by organic ligands.
This is done to tune their properties and make them even better catalysts.
Unfortunately this essentially clads the platinum in organic armor
that makes them extremely resistant to the effects of aqua regia.
We need to destroy that armor. To do that we incinerate it.
Organometallic complexes cannot survive excessive heating and they decompose into their base metals
while at the same time oxidizing the organic ligands into carbon dioxide, water and various salts.
Thiols and thiolates are decomposed into sulfur dioxide and sulfates.
Phosphines become phosphates. Amines become nitrogen and nitrogen dioxide and so on.
Those salts will not be able to protect the platinum when we dissolve in aqua regia later.
We're also destroying ammonium ions that would interfere with the recovery of platinum from aqua regia.
The extreme heating along with the organic residues also reduces the platinum ions into particles of platinum metal.
This will help us wash out the salts later.
Okay keep heating until the fuming stops and the ashes are red hot.
Now if you have a large enough crucible and have enough waste,
you might be able to boil, dry and char the chemical waste all right in the crucible
instead of going through the successive boiling and drying stages i showed earlier.
Since i had smaller quantities i went with a more controlled approach.
Just be careful of popping and sputtering.
And we are done. No more fuming so we turn off the heat and let it cool.
Now if you have a lot of waste and you're unsure if the all the material, especially at the top,
got hot enough to destroy the organometallic complexes then you can mix up the crucible contents
and then send it back for more heating to ensure all complexes are destroyed.
And there is our crucible of thoroughly burned and decomposed chemical waste.
Now it's composed mostly of platinum metal particles,
other metals that got reduced during the heating,
and various salts that are decomposition products of the original organometallic ligands.
The flaky green coating on the inner walls is nickel oxide.
I used a nickel crucible because i happened to have one.
The drawback was that nickel reacts with air at high temperature
to form nickel oxide which you see here as this green coating.
I should have used a porcelain or iron crucible but i didn't have one at the time.
Ah well. Now i know what to use next time i do this.
I'm not too worried about the nickel oxide contaminant because we'll remove it
along with the rest of contaminants when the platinum is recovered.
Nonetheless in future runs i'll be sure to get an actual iron or porcelain crucible.
Now transfer the contents of the crucible to a beaker of water.
Use about five to ten times the volume of the material.
Be sure to wash out the crucible as best you can.
Now with vigorous stirring heat up the beaker until it boils.
What we're doing here is dissolving all the water soluble salts.
Since we reduced all the platinum salts into platinum metal particles earlier we can separate them.
It's very important that we do this to remove the potassium ions that would interfere with our recovery of the platinum from aqua regia.
Now once it boils turn off the heating and let it settle somewhat.
Platinum is pretty dense so the particles should sink easily.
Now while it's still hot, carefully decant off the supernatant and vacuum filter it.
While most of the platinum should remain in the bottom of the beaker
some of the very fine particles will remain suspended
so it's best to filter to ensure as little loss of platinum as possible.
Now take the filter paper and wash the residue back into the beaker.
Add water again and reboil it.
We're repeating the process to ensure we leach out as much of the water soluble salts as we can.
Once again filter, wash, and reboil.
You can reuse the same filter papers to minimize platinum lost.
Although you will have to change to a new filter paper if you're close to tearing them.
Anyway, repeat the cycle for a total of five times.
At the final run dump the whole contents onto the filter paper and remove the stir bar if you used one.
Then allow the residue to completely dry under the air current of the vacuum filter.
Here is the residue as it's drying. Looks like dirt, but it's extremely valuable dirt.
Weigh out a vial and transfer the residue to it.
Looks like we have collected a total of 2.4g of burned and washed platinum rich chemical waste.
At this point we can't even call it chemical waste anymore, it's more of a ultra high grade platinum ore.
Most of troublesome organic wastes and soluble salts have been removed.
We can recover platinum from this the same way we recover platinum from say jewellery or catalytic converters.
Now i don't expect all 2.4g to be pure platinum as most labs use other metals in their work as well.
But i'd be happy just getting 20% worth of the platinum out of this.
You can do a lot of chemistry with just half a gram of platinum.
Now if you zealously cleaned and washed the crucible, beakers and funnels during the process.
All the platinum should be in the this vial and a small portion should still be stuck in the filter papers.
If you're really hell bent on getting absolute recovery
then you can place these papers in a crucible and burn them to recover the platinum residue.
Then you can add the dust to the final collection.
You'll have to have used ashless filter paper to ensure minimal contamination from the ash.
If you didn't, or if you're not that hell bent on absolute recovery and are patient.
Then just save these filter papers for the next time you process chemical waste
and add them to the crucible along with the other platinum waste.
This saves you the labor cost of doing it separately.
That's what i'm going to do with my filter papers.
Now this video was just on converting the liters of laboratory chemical waste into recoverable platinum rich dust.
In my next video i'll go over the common aqua regia based process of recovering platinum
which is applicable to a wide range of platinum sources.
Thanks for watching.
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Now if you would like to join them you can find my patreon page in the video description.
I really appreciate any and all support.