Latest Platinum Drop

So in another thread I was talking about just learning about extracting Pt by itself. I keep attempting to drop with any batch that through assaying is known to have a decent enough percentage of Pt. If nothing else it's great practice and experience!

I have over a dozen filters with the precip from that many different attempts over the last couple of weeks sitting in a tub waiting to be incinerated. Yesterday we were working as usual with a couple different batches at once and one of them was on the heater having just had the Au sponge filtered off. We raise the temperature to 170*F to 180*F and then add our amonium chloride and, (in the past, but not with this particular batch), HCl.

Now, normaly we would also prepare an apx. 1 lb of amonium chloride with 500ml of water for each 8 liters of Pt - Pd laden liquid. We mix it into a slurrry and add it in that fashion.

With this batch we got it up to 189*F. When we added the amonium chloride laden liquid from the top of the slurry we san an INSTANT reaction. That was unusual. Immediately Pt started to drop out faster than I've ever seen it drop out. Since all the other Pt drops we've done have taken considerable time to complete we gave it about 90 minutes and filtered. This is what we captured on the filter!

http://dl.dropbox.com/u/3358180/Pt drop 12-15-09.jpg

For scale, this is a 22 cm filter paper. This should be about 1/4 to 1/2 oz. t. Pt. Our preliminary assay with our X-ray shows a purity of >93%! I will need to schedule some oven time in the near future. We've gotta have a cook off!!!

:lol:
_platinum_

That picture is poetic.

Now where did i leave that filter. :shock:

So, are you saying it is greater than 93 percent platinum chloride, which is about 45.7 percent platinum metal?

Platdigger said:

So, are you saying it is greater than 93 percent platinum chloride, which is about 45.7 percent platinum metal?

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Well I can only say that when I have roasted and ignited other drops that measured in the 90% range with our x-ray in the chloride state, the metal button to come from the chloride was also in the same 90% when x-ray tested and assayed via ICP spectrometer.

I would put money on this batch being around 93% Pt in the final elemental stage.

Every 2.3 grams of ammonium chloroplatinate contains 1 gram of platinum. However if you rinse the salt with a solution containing ammonium chloride, which you should do because some of the salt will re-dissolve in distilled water, you are likely to have some ammonium chloride salt mixed in as well. Never an issue as it is driven off when calcining the salt anyway but my point is it could be less platinum than the 1 gram per 2.3 grams of salt which is the based on the formula weights.

4metals said:

Every 2.3 grams of ammonium chloroplatinate contains 1 gram of platinum.

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The weight of Pt metal to come from this is yet to be determined. The % values I mentioned in my last post pertain only to the purity of the Pt, not the quantity. And I did indeed rinse with amonium chloride solution and surely do have some added salts there.

Also the x-ray instrument we use detects only metals.

Quantity is always nice, but I am most interested in knowing how complete of a separation we have achieved in our processes. My goals are to be able to produce 99.9% shot form of Au, Ag, Pd, and Pt. Au and Ag are easy enough. But Pd and Pt are quite challenging. I have on one occasion managed to produce a button of 99 % pure Pt that weighed in at a whopping 0.53 troy ounces. That was last spring; that level of purity has eluded us since then.

:mrgreen:

The most straight forward way to get your platinum is to drop it first before the gold. Unfortunately that requires the 3x boil down to get rid of the nitric and is time consuming. Drop the platinum with saturated ammonium chloride and you should get the best yield both in quantities dropped and purity. Redissolving the salt, refiltering and dropping it again will improve purity but for the best purity you'll need to do a bromate hydrolysis.

Next you can drop your gold from the solution followed by dropping the Palladium via chlorination.

Bromate hydrolysis is a tedious procedure usually performed on larger quantities but it does produce a high quality product. If you're interested in the bromate hydrolysis let me know and I'll post the procedure.

4metals said:

Bromate hydrolysis is a tedious procedure usually performed on larger quantities but it does produce a high quality product. If you're interested in the bromate hydrolysis let me know and I'll post the procedure.

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Thanks, 4metals. I have been stockpiling all of our amonium chloroplatinate for further refinement. I also have many pounds of palladium amonium chloride that needs to be processed more to purity. We can save that for another time. But I am interested in learning how to purify our Pt. :mrgreen:

You can further purify the incinerated platinum sponge buy repeating the AR process on the sponge before melting.

Each successive cycle through the AR and ammonium chloride should increase the purity of the platinum.

The incinerated sponge dissolves very easily in hot AR.

Proper denoxxing and ammonium chloride washing is very important to the purity. Of course you will reach a theoretical limit to your purity depending on the contaminating metals.

Also Palladium ammonium chloride is soluble in excess ammonium hydroxide. The Palladium salt is then precipitated from the filtered hydroxide solution with HCl.


Steve

lazersteve said:

You can further purify the incinerated platinum sponge buy repeating the AR process on the sponge before melting.

Each successive cycle through the AR and ammonium chloride should increase the purity of the platinum.

The incinerated sponge dissolves very easily in hot AR.

Proper denoxxing and ammonium chloride washing is very important to the purity. Of course you will reach a theoretical limit to your purity depending on the contaminating metals.

Also Palladium ammonium chloride is soluble in excess ammonium hydroxide. The Palladium salt is then precipitated from the filtered hydroxide solution with HCl.


Steve

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Thanks Steve!

On the Pt, does that mean that the chloride neeeds to be incinerated after each subsequent drop?

And on the Pd, can you please explain what "excess ammonium hydroxide" is? I've looked it up, but I'm not getting the jist of the "excess" part of it.

Scrap

Bromate Hydrolysis

Impure platinum sponge which has been reduced from de-noxed aqua regia solutions treated with ammonium chloride are collected and processed in 100 ounce lots by a process known as bromate hydrolysis. The objective of this technique is to separate the platinum from other platinum group metals and base metals by the formation of their hydroxides. Platinum, not forming a hydroxide remains in solution for further refining.

Digest the impure sponge and destroy the nitrates by classic evaporation to syrup to drive off the excess nitric. Dilute the syrup with HCl to a concentration of 1.75 troy ounces of Platinum per liter of solution for hydrolysis. This is usually done in a glass lined reactor capable of stirring and either boiling via steam jacketing or heating mantle. Vessel should be sized to allow it to operate at ½ capacity. (for 100 ounces that is approx. 50 liters of solution)

Heat solution to boiling and add 5% of the precious metal weight in zinc chloride. This acts as a coagulating agent. Stir for a few minutes and begin adding a saturated solution of sodium bromate. Solution should be added slowly as it will boil up. Solution should be added below the solution level in the reactor by delivering through a glass tube which extends below the solution level in the reactor. Add a total of ½ ounce of sodium bromate (in a saturated solution) for each ounce of precious metal in the reactor. Go slowly as it will foam up, take your time and add water to maintain the original level of the boiling solution.

Siphon a saturated solution of sodium bi-carbonate into the vessel to neutralize the solution. Adjust the pH to exactly 7.5. Shut off the heat and adjust the volume with water to the original starting level.

Add 1 liter of a coagulant (magna floc) and allow solution to cool to 40 C.

Allow the solution to settle for at least 2 hours then decant the clear the liquid followed by siphoning the settled hydroxides which are collected on a filter and washed. Washes are added to the decanted solution.

The decanted solution is now acidified with 2 liters of HCl for every 100 ounces of metal and boiled for 1 hour. Add 5 ounces of oxalic acid for every 100 ounces of metal to precipitate any gold in the solution. If iridium is present, add 1 oz of sodium sulfite for every 100 ounces of metal. The solution is now filtered and transferred to precipitation tanks for conversion to ammonium chloroplatinate.

Heat the solution to 70 C and drop the ammonium chloroplatinate with ammonium chloride. Decant the solution and wash the collected salts in a room temperature solution of 1/3 saturated ammonium chloride solution, 1/3 HCl, and 1/3 H2O.

Either transfer the salts to a glass reactor and reduce with hydrazine or calcine in a silica tray at 800 C for 20 minutes.

If you started with relatively pure salts (99%) this will produce high purity sponge.

This procedure is completely scalable depending on your reaction equipment. The first time you do it will be the hardest, once you get the required addition volumes down, routine reproduction of results is predictable.

Wow, thank you 4metals!

That sounds like a very interesting process. I'm game!

Time to make my shopping list...... :lol:

Some of the things you say fourmetals, some would be displeased to hear. It's all in the literature though.

Some additional points to mention:
- use only sodium bromate, not potassium bromate (supposedly you can lose platinum to a potassium platinum double salt, plus it is less reactive than NaBrO3).
- use sodium carbonate, not bicarbonate--more acid neutralized per amount of mass
- if adding bulk Na2CO3, use overhead stirring to break the foam.


Also, the sulfite drops any Ir as its dioxide if I remember correctly. EDIT: Also forgot, sometimes it is necessary (especially after the sulfite, well known for reducing Pt (IV) to Pt (II) to sparge with chlorine gas or add extra HCl and sodium chlorate/bromate (either work, but chlorate is cheaper). This ensures that all platinum is "H2PtCl6".

Lou said:

Some of the things you say fourmetals, some would be displeased to hear.

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But by posting it here some are quite pleased to hear. I worked out the specifics of this method from the literature and trial and error. No-one was lining up to give me a procedure. I've used this process since the late 70's and for years produced multiple hundred ounce lots per month producing fine metal for resale.

The important part of what I said and the reason I posted it on scrappers request is that he also has a use for fine platinum that he produces. If you have no market to resell the platinum, either as jewelers alloy as I did or other reasons, it is not cost effective to do it. It's better to refine it to impure sponge and sell it as a refining lot. Unless you can get premiums for the pure metal it's better to bite the bullet and ship it than to put the time and expense into refining it only to have the buyers discount it anyway.

scrap said:

On the Pt, does that mean that the chloride neeeds to be incinerated after each subsequent drop?

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The platinum is reduced to the sponge form before each digestion.

scrap said:

And on the Pd, can you please explain what "excess ammonium hydroxide" is? I've looked it up, but I'm not getting the jist of the "excess" part of it.

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Excess means to add the ammonium hydroxide until all of the palladium salt is dissolved. The process is complete when subsequent additions of ammonium hydroxide with stirring do not dissolve any more of the solids. The initial addition will typically form a burnt orange colored ('flesh colored') precipitate, upon further addition of ammonium hydroxide the flesh colored precipitate will redissolve in the 'excess' ammonium hydroxide solution.

Filter out the solids, rinsing with ammonium hydroxide, and add HCl to the filtered solution. The purified yellow palladium salt will precipitate. Hoke covers this process.

Steve

sorry to hijack this thread...

steve, have you gut my PM ?

$metals
I mean 4metals, in that process you added a coagulant.
Magnafloc,

is this what you were talking about?
http://www.idswater.com/water/us/synthetic_flocculants_coagulants/1411/products.html

is this chemical needed for the process? will it coagulate another method,or can something else substitute here?

Scrapper the more questions you ask the more I learn.

That's the stuff! I don't know how difficult it is to obtain in lesser quantities, but it never had any shipping issues as a hazardous or corrosive material.

Either transfer the salts to a glass reactor and reduce with hydrazine or calcine in a silica tray at 800 C for 20 minutes.

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This was explained by 4metals
If anyone can give me more details that would be nice
THanks

I have this part figured out
Hydrazine Sulfate ?
http://goldrefiningforum.com/phpBB3/viewtopic.php?f=37&t=2503&hilit=hydrazine+sulfate


As for this part of the process I am still not sure about it

calcine in a silica tray at 800 C for 20 minutes

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