# PGM recovery diff method.



## kjavanb123

All,

Instead of hcl-cl and wait for a while to dissolve pgm of a cat, i added 700cc HCl and 200cc HNO3 and heat it for almost 5 hrs as you can see from the following pictures.






Now evaporating the NOxx from the solution using steam bath.



Few mins into NOxx evaporation and the color of solution changed.



After 2nd hydration with HCl , tap water added to dilute the solution



I think made two mistakes here, first added water was too much, or the solution was not near boiling, when i added ammonium chloride. So i assume temp of solution for ammonium chloride addition should be kept at below boiling, does it stay like that or should it be cool off to orange powder to percitipate?


Thanks
Kev


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## Harold_V

kjavanb123 said:


> I think made two mistakes here, first added water was too much, or the solution was not near boiling, when i added ammonium chloride.


It is not necessary for the solution to be heated in order to recover platinum. I did ALL of my recoveries of platinum with ambient temperatures, or even colder, but never heated. The solution is heated for the recovery of palladium, however. 
It is my opinion that your solution is too dilute. The color displayed in the last picture is very light. Platinum metals, unlike gold and silver, are not recovered chemically from dilute solutions. 

Harold


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## Lino1406

There is a misunderstanding about ammonium chloride - should be added
and heated - but be in excess to ensure saturation


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## lazersteve

I feel the reason for heating is to facilitate the rapid Pt salt formation (crashing) when the solution cools after the NH4Cl is added. 

Solubility curves dictate that a hot solution will hold more of a dissolved substance than a cold one, hence when heated the dissolved salts will form in the solution and upon cooling will crash out of the solution as the colored powder. This is not to say that heating is required for the reaction to occur, but heating does aid in the rapid formation of the colored salt.

This principle applies to all crystallization reactions and is commonly used to harvest crystals from solutions and is sometimes referred to as super saturation.

Steve


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## kjavanb123

lazersteve said:


> I feel the reason for heating is to facilitate the rapid Pt salt formation (crashing) when the solution cools after the NH4Cl is added.
> 
> Solubility curves dictate that a hot solution will hold more of a dissolved substance than a cold one, hence when heated the dissolved salts will form in the solution and upon cooling will crash out of the solution as the colored powder. This is not to say that heating is required for the reaction to occur, but heating does aid in the rapid formation of the colored salt.
> 
> This principle applies to all crystallization reactions and is commonly used to harvest crystals from solutions and is sometimes referred to as super saturation.
> 
> Steve



So i assume below boiling, add 5grams of ammonium chloride to 20cc warm water and pour that into the beaker containing solution then stop heating while Pt percipitate?

Thanks
Kev


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## lazersteve

Yes, as long as the solution is concentrated enough to facilitate the colored salt to crash out.

Steve


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## goldenchild

I just wanted to point out that you may want to use a watchglass on top of your vessel or you could be evaporating off alot of your values.


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## Lou

Harold, heat is not required for the palladium salt. In fact, it is better to do it in an ice bath because it is more efficient and quicker (uses less NaClO3).


Lou


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## Harold_V

lazersteve said:


> Yes, as long as the solution is concentrated enough to facilitate the colored salt to crash out.
> 
> Steve


That's really key to success. I recovered several ounces from a couple liters of solution at one point in time. I dissolved my ammonium chloride in hot water, which had turned quite cold by the time it was all in solution. I quickly poured that solution to the ambient temperature solution of platinum and can honestly say that was the one and only time I achieved a full recovery of values. *Concentration* is far more important than is temperature, at least with my experiences. 

Harold

My sincere appreciation to Platdigger for bringing to my attention a mistake in my original comment. I had typed hydroxide instead of chloride. Old age! Ain't it grand?


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## kjavanb123

All,

Some updates for this pgm project. After reading your posts here, This is what I did in with pictures

30ml of pgm solution was being evaporated to remove the NOxx and become syrup. as you can see from the picture below, a saturated ammonium chloride is being prepared at the same time, by adding 6grams of ammonium chloride to 20ml of warm tab water.



Saturated ammonium chloride solution



After half and hour or so, it seems like the solution is turned into a syrup.



I tested the syrup and the stannous turned it into a dark brown as you can see below.



Finally per Steve instructions, poured the saturated ammonium chloride solution onto syrup, while on steam bath, waited for 5mins and small white particles and few red crystals emerged which i filtered and this is what was left in the beaker.



Now couple of questions, in Pt Fund DVD, 5grams of ammonium chloride was added to 20ml of water, for 300cc of pgm solution, I used to the same measurement for my 30ml test solution. should i tune it down to match 30ml of solution?

I am gonna try your tips tommorow and let you all know, thanks for your adivce, Also happy new yr everyone.

Kev


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## lazersteve

You'll need to adjust the amount of water and NH4Cl you use based upon the expected yield of PGM in the pregnant solution.

Steve


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## Lou

Given that you have so little platinum, here is what I would do if I were in your situation and didn't want to get terribly involved:

Presuming that this mix contains platinum, palladium, and rhodium...

1.) cement everything with zinc (or even copper, but I caution anyone who wants to plate with their rhodium to never introduce copper!) [<1 hr]
2.) take this reduction product, rinse it clean with NaOH to remove zinc. [<1h]
3.) Add nitric acid and the solution will turn yellow then deep brown as the palladium dissolves. [<1h]
4.) decant, add water, decant, add more concentrated nitric and heat. Do this until the solution no longer goes yellow (shouldn't take long) [<1h]
5.) Digest the residues in concentrated sulfuric acid, it will go yellow then a very brown-red as temperature increases. Repeat until no color takes to the acid. [<4h]
6.) What's left is mostly pure platinum. Digest in HCl to which hydrogen peroxide is carefully added at room temp. then boil the solution once to rid it of chlorine. [<3h]
7.) precipitate by dropping your solution into a saturated solution of ammonium chloride. Whatever the weight of the platinum was, 1.1X that in ammonium chloride is perfectly sufficient to precipitate the platinum and leave enough ammonium chloride in the solution to drive solubility down.
8.) Your ppt. should be a nice yellow without reds and _especially_ any green (otherwise you had not removed all the rhodium down to <0.5%). If you do get some green, heat the precipitate in the minimum amount of water until it dissolves to give a yellow solution. Add a little more water and cool slowly down to 0*C. At that point, I add dropwise saturated room temp. ammonium chloride that is 0.05M in H2SO4. This should get rid of the rhodium.

Good luck, have fun, and don't get anything on your skin!

Lou


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## lazersteve

Great post Lou,

Thank you!

Steve


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## qst42know

Lou

In step 6 what would the concentration of hydrogen peroxide be?


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## Lou

I use 30%, but I want it to work quickly. I try to avoid aqua regia because any excess nitric acid will guarantee greater contamination of the platinum by other sister metals. The boil is to remove the free chlorine so palladium doesn't coprecipitate. 


Lou


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## kjavanb123

Lou,

Is your method practical for larger scale? or is it just lab scale? I am gonna try your method to see if i can get it right this way. also what do you mean by decant? 

I am willing to pay anything to some of you pros in PGM refining here to show me everything from A-Z in refining cat, this is getting on my nerve that I see stannous shows a concentrated Pt in solution yet I can't get it into orange sponge. So anyone please name your price and let's schedule a time and date, so I can come by and you show me how it is done. To me it seems like a great investment specially with my access to a large stock of foreign model cats.

Thanks
Kev


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## lazersteve

kjavanb123 said:


> Lou,
> 
> Is your method practical for larger scale? or is it just lab scale? I am gonna try your method to see if i can get it right this way. also what do you mean by decant?
> 
> I am willing to pay anything to some of you pros in PGM refining here to show me everything from A-Z in refining cat, this is getting on my nerve that I see stannous shows a concentrated Pt in solution yet I can't get it into orange sponge. So anyone please name your price and let's schedule a time and date, so I can come by and you show me how it is done. To me it seems like a great investment specially with my access to a large stock of foreign model cats.
> 
> Thanks
> Kev



Kev,

Your solution does not contain very much Pt. The stannous chloride test is very sensitive hence the dark color of your swab. 

Here's a photo of a solution of ~18 grams of dissolved Pt :







Everything I see in your posts indicates you are getting Pt extraction. Where are you needing help? Please don't take this the wrong way, but it seems like you have skipped around a lot using the processes and have not followed the directions as they were presented. Your most recent attempts indicate you are starting to get results and just need a little more practice and patience.

If I were you I would get a known sample of one or two grams of Pt and Pd then practice refining them until you are comfortable with the entire process.

I believe you have my Pt and Pd DVD and the methods on it produce good results for cats. For large scale cat extractions you may want to consider setting up gas phase extraction using a tube furnace.

PM me if you want to arrange something else.

Steve


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## Lou

I don't reclaim automobile catalytic converters, but I will refine reclaimed concentrates from them, so I suppose that is what you'd want to see and try your hand working with the platinum group. 

Your best and cheapest bet might be to purchase 10 g bars of platinum and palladium and dissolve them. I can send you some Rh since you won't find that material in small quantities for anything close to sane.

Try dissolving said bars in aqua regia, cold and hot. Weigh the bars after a period of time. You can get how many mg of material will dissolve per hour per square centimeter at a given temperature and concentration of reagents. You'll notice an increase in rate of dissolution as the surface area/volume ratio increases. You'll notice a decrease in rate of dissolution as the solution becomes more concentrated with values. Plenty of things that you must find out yourself because it won't be in the literature 

I'll level with you: most PGM refining (_especially_ for Rh, Os, Ir, Ru) is done at the bench in fume hoods. That's how I've always done it. It's not done on grand scale like it is for gold and silver. It simply isn't done that way regardless of the company. Platinum heats are small heats. If one refined only gold and silver but was never serious about platinum metals, he'd be in for a surprise when he tours refineries doing only PGMs. They're much lower volume and much more involved in processing. The chemist's tools in dealing with platinum and her sister metals are flasks ranging from 1L to 22L and batches in the several hundred ounce range (or less). Why do you think refining charges are so high on platinum, let alone rhodium? Much more labour involved, takes longer to dissolve, precipitations aren't 100% efficient, reductants aren't selective, and so on! There is no place for 5 gallon buckets like in gold or silver, let alone electrolytic cells (point conceded that rhodium can be electrorefined quite nicely in some situations). Gold (and silver) are refined by technicians, for one having technical knowledge may be competent. Refining various members of the platinum group, well that requires skills not needed for gold and silver. I realize that sounds terribly elitist, but how many people honestly prepare their own osmates and ruthenates? Calcine their own rhenium? Make purpereosalt out of rhodium? The explosive double nitrite of diammine platinum (II)?

As far as that method I gave you goes: yes, it will scale. But it's _all_ lab scale!!! I wrote that method (and included approximate times) to give you an idea how quickly it might be done in a general circumstance by one who knows his business. It's not how I would do it. Keep in mind though, what you're doing is very very small volumes at tens of grams. You will be very, very hard pressed to find anyone who will seriously tell you how they do it on large scale with all the specifics and hold your hand through the process. Why? Because that is developed by the company and their chemists and stays in the company. You're also not a chemist, so learning this will be irksome. Generalities are published in the literature and IPMI proceedings. It's fairly secretive. Even Raleigh Gilchrist himself (who you had better be reading) makes a great note of it in his splendid review on the platinum group metals and their processing:

"The chemical engineering problems in connection with the refining of platinum
are of a specialized nature, with the result that experience in other fields is not
always directly applicable. Moreover, the tradition of secrecy in the platinum
industry up to the present has prevented refineries from pooling their experience
except in a very general way. This state of affairs is in marked contrast with
what is known about the plant and processes for the refining of silver and gold.
Because of this tradition of secrecy concerning, particularly, the wet processes
used for refining crude platinum and platinum concentrates, very few details
find their way into the literature. The processes used for commercial refining,
once the platinum metals have been concentrated to a point where wet processes
apply, probably differ very little. The scale of operation is small; even the refining
of platinum is frequently described as large-scale laboratory work, and the
refining of the other metals of the group is on a still smaller scale."

Gilchrist, Raleigh._ Chem. Rev_., *1943*, 32 (3), p 295.

Very little has changed save for induction melting, instrumentation, S/X and perhaps some finer points in the aqueous chemistry. One thing that has certainly remained the same: people who refine platinum group metals do not like newcomers. They will not like you refining them. They don't like those who talk about refining them (incidentally, Gilchrist was well respected for his chemistry, not for his mouth). There are not many names in the game so to speak and most roads lead to Rome. Ponder that when you go to sell your first 10 ounces of fine metal!


Good luck to you.


EDIT: by decant, I mean to pour off or siphon away without disturbing the precipitate. It requires a steady hand. As you will come to learn, should you persist in your PGM work, chemistry is as much a trade as carpentry, and requires intimate knowledge of which tool to use to accomplish a given task. In some ways, it reminds me of football for it requires strategy, and the risk of physical harm is quite real.


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## jimdoc

Here is a link to a Raleigh Gilchrist picture in the lab.
Looks like he liked the pgm's so much,that he drank them.
Well,thats what it looks like. :shock: 

http://www.old-picture.com/american-legacy/010/Gilchrist-Raleigh-001.htm

Jim


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## butcher

homade CO2 gas?


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## lazersteve

Wash bottle.

Steve


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## kjavanb123

Lou,

Thanks for your complete review on Pt refining. in your step 1 cementing with zinc, do I need to dissolve the soda ash first before cementing with zinc? or just directly zinc into the AR pregnant solution?


Also this method works if all 3 elements are mixed or does it work if only 2 of them are in the solution?


Thanks
Kev


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## Lou

Complete review on PGM refining? I'm almost positive that you're being sarcastic with me; please desist. Sorry if I seem disparaging, but it's no easier than saying "I want to be a master woodworker or mason or star athlete".

You don't need to use soda ash. In fact, keep it out unless you have pH papers (if you do, get the pH to 2-3 and then start with zinc additions). Most importantly, remove the nitric acid from your solution. If you do not, it will take much more zinc to reduce the PGMs because the nitric will preferentially be reduced to laughing gas and other nitrogen oxides and not ever transfer its electrons to the platinum.

This method works well for any metal less active than zinc. This includes copper and iron.


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## kjavanb123

Lou,

I tried your method this morning and I think i was lost at step 2 and on lol. Here is some 
slide show for you all.

Per your last instruction, tried to remove the nitric in solution using evaporation method,



Tried the stannous test as I progressed each step of denoxx-ing and adding HCL to solution
View attachment 3


I am guessing this is syrup enough
..


After 2nd addition of HCL to solution and make it syrup again, I added soda ash to the soltuin



Cementing with zinc, added to solution, then added the NaOH to remove the zinc.



Forum won't allow more than 5 pics, so I just tell you what happenee then
Added nitric acid and it turned to yellow, not brown as I guess there was no Palladium. and still have some zinc or NaOH fizzling in the solution
I went ahead and added sulfuric acid slowly..it bubbled and turned into canary yellow with some white residue.

Here are my confusions.

1. the original solution which was concentrated AR, I added sulfuric acid, does that remove the NoXXX? verses HCL-CL solution which would react with soda ash and zinc and black powder would produce, i didn't see that reaction with AR. what is the problem here?

2. in step 2 of ur instruction, addition of NaOH to remove the zinc, NaOH should be mixed with warm water first then pour it to solution?


Thanks
Kev


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## Lou

Let me be clear: after you've cemented the PGM-bearing solution with zinc, filter or decant the solution to remove the *colorless* supernate. Then add some fresh water to the precipitate, stir, let it settle, and repeat. This removes excess acid and zinc chloride. After that, use a 20% weight/volume solution of lye to dissolve the excess zinc (this solution can be used *multiple* times if you're patient and sparing on the zinc turnings). Do this warm but not boiling. Look (through your goggles!!) and see if there are any bubbles of hydrogen being produced. If not, the zinc is removed as soluble sodium zincate. Pour off the lye solution and then you can add nitric acid to remove the palladium. Remember, nitric removes palladium and lesser base metals that may have been cemented. Hot, concentrated sulfuric acid removes the rhodium and also palladium (that's why you use the nitric acid to remove the palladium in the first step). The platinum is not affected by either sulfuric or nitric acid or combinations thereof. It should be pretty pure, but you can redissolve it in aqua regia or in cold to room temperature HCl to which you add small additions of hydrogen peroxide.

3.) Add nitric acid and the solution will turn yellow then deep brown as the palladium dissolves. [<1h]

If yours didn't go brown during the nitric addition, that means it's not very concentrated. The fact it went yellow means that the palladium was dissolving--if it didn't go green, then there's no copper but iron may still be present. I prefer small additions of nitric acid, and decanting and rinsing until color is no longer produced. Then it gets the same treatment for rhodium, except sulfuric acid is used and caution taking it in heating it and decanting. It's better not to rinse. You can always leave them altogether and separate conventionally, running bromate hydrolysis on the impure platinum yellow.


Lou


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## kjavanb123

Lou,

Thanks for your clearfying the instructions. I was wondering what happens if I add concentrated sulfuric acid to the AR pregnant solution at the begining.

H2So4 + H2PtCl6 ----> ?

or if addition of H2O2 at the begining would that releases the nitric?

20% weight/volume? can you plz give me some example? sorry no chemistry background here.

Thanks
Kev


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## Lou

Keep the sulfuric out of it except for removing rhodium from platinum (AFTER the palladium is removed).

20% w/v means 200 g of NaOH per 1000 mL of water.


Lou


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## goldenchild

Lou said:


> Very little has changed save for induction melting, instrumentation, S/X and perhaps some finer points in the aqueous chemistry. One thing that has certainly remained the same: people who refine platinum group metals do not like newcomers. They will not like you refining them. They don't like those who talk about refining them (incidentally, Gilchrist was well respected for his chemistry, not for his mouth). There are not many names in the game so to speak and most roads lead to Rome. Ponder that when you go to sell your first 10 ounces of fine metal!



Lou,

I finally got to thoroughly read this thread and what you said here reminded me of some pictures I once saw. I was able to find the article. I was wondering(without giving any trade secrets away) how long it would take a large scale refinery to accumulate the amount of Pt in two of the pictures. One being the guy holding the huge block of Pt and the other of the bucket of Pt sponge. Also, on average how long does it take to get scrap of say jewelry from jewelry, to sponge to melted bar?

Here is the link. Its 2nd and 4th post.
http://www.pricescope.com/forum/rockytalky/virtual-tour-of-precious-metal-refinery-t41704.html


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## Lou

Incoming scrap jewelery (say bands) have to be sorted, weighed, melted, shot, digested, filtered (to remove Ru and Ir), precipitated, calcined, assayed (if you use ICP-AES, you assay here), or melted and then assayed with XRF as the bulk. Large ingots like that are often not cast--it's rare to see one so big. Often one makes more 950 (usually Ru based, because Ir is so soft and doesn't take a Rh plate well) or 900 alloy and sells as casting grain, wire, or other fabricated goods. The alloys work harden much more than the Pt, so they have to be annealed. Time can be from 3 days of good work under the best conditions to weeks if you're making value-added product. It really depends on what you're set up to do. Most important in refining Pt is having it down to the right size. If you don't have it down to a high surface area material on an incoming refining lot, it'll take a very long time (dissolving massive platinum is about as frustrating and quick an endeavor as hand-chiselling one's own granite monuments with a spoon. 

Platinum bars are poured from zirconia crucibles that are "double bagged" inside an alumina crucible. The heavy wall alumina bears the weight of the ZrO2 crucible containing the Pt. Zirconia looses its strength after a few heats and must be replaced fairly often. Usually you have a "starter" plug or heal of platinum that soaks up the power because most melters are 10-12 kHz and won't heat powders for crap. Same thing for gold powder--most of the heat goes into the graphite or SiC crucible and melts it by conduction! It's a different story if you put a cylinder of gold in there. When the Pt plug melts you can add the sponge platinum. I much prefer to have not melted the material but have the sponge sit upon the bulk metal and heat, that way any moisture is steamed off. 

Pd is much of the same, except atmosphere control is more important as it is considerably more gassy than platinum.

Because quantities of Rh are so small, it is always more convenient to torch melt by hand with oxyhydrogen on a magnesia block while wearing shade 12s or 13s and averting your eyes. Shade 10 is good for platinum or quartz working.


EDIT: It's quicker to refine jewelry platinum rather than raw platinum concentrates (that's involved!) because all impurities are generally known and it's a fairly simple separation to rid it of the Ru, Ir, or Co.

Lou


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## HAuCl4

Had missed this nice thread. Thanks for the panoramic view and the descriptions Lou!.

Fascinating and unprofitable for 99.99% of people including myself, that's how I'd describe PGM refining!. :lol:


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## kadriver

HAuCl4 said:


> Fascinating and unprofitable for 99.99% of people including myself, that's how I'd describe PGM refining!. :lol:



Great way to have fun learning something new though - I am having a blast!

I want to thank Lou for posting this process. It is straight toward and practicle for a new guy like me.

I am printing the pages of instructions to keep at my shop for reference.

kadriver


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## HAuCl4

It can become an addictive hobby!. Beware!.


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## kadriver

Lou said:


> 6.) What's left is mostly pure platinum. Digest in HCl to which hydrogen peroxide is carefully added at room temp. then boil the solution once to rid it of chlorine. [<3h]
> 
> Good luck, have fun, and don't get anything on your skin!
> 
> Lou



I am new to PGM refining and plan on using this process - can I use HCL/Cl instead of HCL/H2O2 to dissolve the black powder in step 6? Is there an advantage to use H2O2?

Thanks - kadriver


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## lazersteve

Both work fine, no salt formation with peroxide.

Careful with high concentration peroxide (30%+) as it has a bad habit of delayed reactions. Be sure to wait a few minutes with lots of stirring to be sure you don't form a run away reaction and evertything boils over.

Steve


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## freechemist

Hello kadriver,

In his excellent posts about PGM-refining Lou wrote:

_6.) What's left is mostly pure platinum. Digest in HCl to which hydrogen peroxide is carefully added at room temp. then boil the solution once to rid it of chlorine. [<3h]

Good luck, have fun, and don't get anything on your skin!_

To me the most important paragraph reads: "don't get anything on your skin!" Keep that in mind, if you are inclined seriously to involve in platinum-recovery/refining. Hexachloroplatinates and hexabromoplatinates, in solid form or dissolved, are potent allergens, often showing it's effects after repeated exposures only after a long delay (weeks or even months).

To your question regarding use of HCl/H2O2 or HCl/Cl to dissolve the black powder in step 6: 

Definitely Yes! Both methods are functioning well. I personally preferred the HCl/Cl-method, using NaClO3 (sodium chlorate) in place of "Clorox" or NaOCl-solution. Commercially available NaClO3 usually is pure (98% or more), non hygroscopic and well soluble in water, so you can prepare a fairly concentrated solution and add this slowly to your digestion-mixture to generate the chlorine needed to dissolve the black powder. In addition, 1 equivalent of NaClO3 is theoretically able to oxidize 1.5 equivalents of Pt(0) (metal) to the Pt(IV)-state in PtCl6(2-), and thus the amount of sodium added to the solution is much smaller, than using "Clorox" or NaOCl. After my experience addition of some HBr (48% hydrobromic acid), about 10% the volume of the already used HCl, helps to accelerate the dissolution and keep oxidant losses by evaporation/outgassing of elemental halogen (Cl2, Br2) on a low level, especially if using a reflux-condenser on the reaction vessel, because the boiling point of Br2 is much higher than that of Cl2.

Regards, freechemist


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## Lou

@freechemist: Halogen and HCl with pressure and heat in a Pfaulder is the way to go. 


I omitted several steps earlier on--for instance, and I think everyone here knows, you don't dissolve bulk shot platinum in aqua regia or halogen/HCl. Just doesn't work quick enough. Fine with powders and foils but would never work on BBs or coarse powder.

Used to be that you'd make a 60-75% Pt balance nickel alloy and shot that. That dissolves in aqua regia as fast as gold does. Nickel is kind of looked down on these days...

Today, all the real platinum refining is done with s/x and runs through pretty little tubes. I think freechemist was at MetalorSA in Switzerland, so I'm sure he can confirm


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## goldenchild

Lou said:


> I omitted several steps earlier on--for instance, and I think everyone here knows, you don't dissolve bulk shot platinum in aqua regia or halogen/HCl. Just doesn't work quick enough. Fine with powders and foils but would never work on BBs or coarse powder.
> 
> Used to be that you'd make a 60-75% Pt balance nickel alloy and shot that. That dissolves in aqua regia as fast as gold does. Nickel is kind of looked down on these days...




How about silver? I think I read that Pt will dissolve using only nitric if alloyed with silver.


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## Lou

If it's in the right proportion. It's really a troublesome thing that is not easily explained. Anyway, you get your Pt back by adding HCl and forcing the silver out. Unfortunately, some of the silver entraps the platinum...


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## Dr. Poe

Lou said:


> If it's in the right proportion. It's really a troublesome thing that is not easily explained. Anyway, you get your Pt back by adding HCl and forcing the silver out. Unfortunately, some of the silver entraps the platinum...


When silver is alloyed with platinum in sufficient amounts, They dissolve together into nitric acid. HCl added to the solution precipitates silver chloride, but silver chloroplatinate hangs in solution as white cloud that resists settling. The two can be separated by decanting the white cloud from the silver chloride. Then heating with additional Aqua regia. The silver is released and precipitates as the pure chloride while the platinum remains in solution.
By the way guys, I've really enjoyed this thread. Kudos to you all. Dr. Poe :mrgreen:


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## Lou

Plain acidic water alone will decompose silver chloroplatinate.

Specifically though, it is indeed a weird phenomenon. 

For those who are interested in a historical work:

http://books.google.com/books?hl=en&lr=&id=sok6AAAAMAAJ&oi=fnd&pg=PA7&ots=rZIrRnk-By&sig=bhq86Xr73VX9V6OpiJj22D6qlUc#v=onepage&q&f=false


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## nickvc

Having just reread this thread to try and get some understanding of the processes to achieve a fairly pure product I have to agree with Lou,s assessment that refining the PGMs is much more involved and difficult than dealing with gold and silver hence my decision not to try, leave it to those that can and safely. My problem is not unique I have a batch of PGMs in solution from the stock pot and really don't want to refine each but just recover as a mixed precipitate. I tried cementation but find the powders adhere quite tenaciously to the copper bar so I was wondering if using fine copper powder would work, I'm not bothered if it's totally PGMs but I don't want to melt small amounts of PGMs with large amounts of copper to recover the values hence the reason I don't want to use zinc. If anyone has any better ideas I would be pleased to hear them so I can put this to bed and free up my beaker.


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## HAuCl4

nickvc said:


> Having just reread this thread to try and get some understanding of the processes to achieve a fairly pure product I have to agree with Lou,s assessment that refining the PGMs is much more involved and difficult than dealing with gold and silver hence my decision not to try, leave it to those that can and safely. My problem is not unique I have a batch of PGMs in solution from the stock pot and really don't want to refine each but just recover as a mixed precipitate. I tried cementation but find the powders adhere quite tenaciously to the copper bar so I was wondering if using fine copper powder would work, I'm not bothered if it's totally PGMs but I don't want to melt small amounts of PGMs with large amounts of copper to recover the values hence the reason I don't want to use zinc. If anyone has any better ideas I would be pleased to hear them so I can put this to bed and free up my beaker.


1-Evaporate stock pot to a crust, mix well with litharge and flour/powdered coal, and cupel?. (Add a little silver, silver oxide, or AgCl to help collect into a button free of base metals.)

2-Alternatively, you could use concentrated sodium formate in slightly acid (formic acid) solution to precipitate all precious metal blacks together after you concentrate the stock pot. The settling is a pain to watch. The blacks are a pain to handle, but they are really ready for further processing.

3-Or... use thin copper *foil* sparingly to cement. 

edit: I'd choose number 3 in 99.99% of cases. :lol:


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## HAuCl4

nickvc said:


> refining the PGMs is much more involved and difficult than dealing with gold and silver.


The main difficulty is in getting them in enough quantities. Everything is done in 8 hours or less these days for all 8 metals. Coming soon to a kitchen near you!. Rhodium is a bitch though.


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## goldenchild

Lou said:


> Specifically though, it is indeed a weird phenomenon.



Agreed. I believe it was Harold who I saw mention this oddity. I thought he had misspoke but he enforced and clarified.

Platinum... the goofball of PMs :lol:


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## freechemist

Hey Lou,

Your statement _"you don't dissolve bulk shot platinum in aqua regia or halogen/HCl. Just doesn't work quick enough."_ is perfectly right, as is your foregoing statement: _"Halogen and HCl with pressure and heat in a Pfaulder is the way to go"_. 
In my last post I spoke definitely only of relatively fine powder, like platinum-black, which dissolves after my experience much faster, if the dissolving acid contains some HBr, too. In my practice I found that addition of some HBr is also very effective in the dissolution of coarser grey, evidently metallic Pt-powders, like they are obtained by reduction of platinum-solutions with hydrazine sulfate or with formic acid/formiate in a strictly controlled buffered system at a pH-value around 2. What concerns the dissolution reactor, I preferred always a massive titanium-reactor over a Pfaudler for all operations with corrosive PM-solutions.
Your third statement _"Used to be that you'd make a 60-75% Pt balance nickel alloy and shot that. That dissolves in aqua regia as fast as gold does"_ I can partly confirm, too, except, that I preferred copper as alloying metal and a total Pt-content of about 80%. This receipe functions well, even for Pt alloyed with Ir or Rh.
I am sorry, that I can not confirm your last statement: _"Today, all the real platinum refining is done with s/x and runs through pretty little tubes. I think freechemist was at MetalorSA in Switzerland, so I'm sure he can confirm"_, because I never was employed by Métalor.

@Dr. Poe:

There is one simple, but very effective way, to avoid formation of sparingly soluble Ag2PtCl6 on adding HCl to a combined solution of Ag and Pt in HNO3. You just have to reverse the addition, that means, you add the silver and platinum containing nitric acid solution to a well stirred bulk of a great excess of hydrochloric acid. Thus precipitation of practically insoluble AgCl occurs immediately, whereas the formation of the complex anion PtCl6(2-) affords much more time.

Regards, freechemist


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## Dr. Poe

freechemist said:


> Hey Lou,
> 
> Your statement _"you don't dissolve bulk shot platinum in aqua regia or halogen/HCl. Just doesn't work quick enough."_ is perfectly right, as is your foregoing statement: _"Halogen and HCl with pressure and heat in a Pfaulder is the way to go"_.
> In my last post I spoke definitely only of relatively fine powder, like platinum-black, which dissolves after my experience much faster, if the dissolving acid contains some HBr, too. In my practice I found that addition of some HBr is also very effective in the dissolution of coarser grey, evidently metallic Pt-powders, like they are obtained by reduction of platinum-solutions with hydrazine sulfate or with formic acid/formiate in a strictly controlled buffered system at a pH-value around 2. What concerns the dissolution reactor, I preferred always a massive titanium-reactor over a Pfaudler for all operations with corrosive PM-solutions.
> Your third statement _"Used to be that you'd make a 60-75% Pt balance nickel alloy and shot that. That dissolves in aqua regia as fast as gold does"_ I can partly confirm, too, except, that I preferred copper as alloying metal and a total Pt-content of about 80%. This receipe functions well, even for Pt alloyed with Ir or Rh.
> I am sorry, that I can not confirm your last statement: _"Today, all the real platinum refining is done with s/x and runs through pretty little tubes. I think freechemist was at MetalorSA in Switzerland, so I'm sure he can confirm"_, because I never was employed by Métalor.
> 
> @Dr. Poe:
> 
> There is one simple, but very effective way, to avoid formation of sparingly soluble Ag2PtCl6 on adding HCl to a combined solution of Ag and Pt in HNO3. You just have to reverse the addition, that means, you add the silver and platinum containing nitric acid solution to a well stirred bulk of a great excess of hydrochloric acid. Thus precipitation of practically insoluble AgCl occurs immediately, whereas the formation of the complex anion PtCl6(2-) affords much more time.
> 
> Regards, freechemist


Sounds reasonable, I'll try that myself. Dr. Poe


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## Dr. Poe

HAuCl4 said:


> nickvc said:
> 
> 
> 
> refining the PGMs is much more involved and difficult than dealing with gold and silver.
> 
> 
> 
> The main difficulty is in getting them in enough quantities. Everything is done in 8 hours or less these days for all 8 metals. Coming soon to a kitchen near you!. Rhodium is a bitch though.
Click to expand...

I usually smack that b'''ch with sulfanyl chloride in solution or with sodium bi-sulfate in a melt. Dr. Poe


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## HAuCl4

Dissolving it (rhodium) is trivial. Ridding it of impurities isn't. :shock:


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## Dr. Poe

HAuCl4 said:


> Dissolving it (rhodium) is trivial. Ridding it of impurities isn't. :shock:


Quite so!,, One takes advantage of the trichloride's insolubility in ether. 8) Dr. Poe


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## butcher

Raleigh Gilchrist and Edward Wichers wrote an article, titled

A Procedure for the Separation of the Six Platinum Metals from One Another and for their Gravimetric Determination. 
1934-1935, publication national bureau of standards of U.S. Department of Commerce.

Here they use a different method of separation, than is normally done, it sounds like a method that produces or separates these metals from each other in high quality (less mix of the PGM metals, and the metal separation more complete).
Osmium and Ruthenium are distilled, (note these can be dangerous as gases), 
Their paper describes the distilling rig and absorption flasks, and reagents needed for the procedure.

The paper also describes the separation of platinum, Rhodium palladium and Iridium.

It is a very interesting article even if you never tried the procedures described, it also give clues to some of the problems we encounter with conventional methods of separation of these metals.


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## HAuCl4

butcher said:


> Raleigh Gilchrist and Edward Wichers wrote an article, titled
> 
> A Procedure for the Separation of the Six Platinum Metals from One Another and for their Gravimetric Determination.
> 1934-1935, publication national bureau of standards of U.S. Department of Commerce.
> 
> Here they use a different method of separation, than is normally done, it sounds like a method that produces or separates these metals from each other in high quality (less mix of the PGM metals, and the metal separation more complete).
> Osmium and Ruthenium are distilled, (note these can be dangerous as gases),
> Their paper describes the distilling rig and absorption flasks, and reagents needed for the procedure.
> 
> The paper also describes the separation of platinum, Rhodium palladium and Iridium.
> 
> It is a very interesting article even if you never tried the procedures described, it also give clues to some of the problems we encounter with conventional methods of separation of these metals.


Lou kindly posted that article in this thread below, and gave some other tips:
http://goldrefiningforum.com/phpBB3/viewtopic.php?f=37&t=11599&p=113821&hilit=cupferron#p113821

It is an analytical procedure, but many of the procedures can be adapted to the larger scale refining. Others, like the use of DMG for palladium, and titanous chloride for Rh/Ir separation aren't practical in large scale, but used as scavengers work great. (To scavenge traces of palladium with DMG, or traces of rhodium in nearly pure iridium solution with titanous chloride-cupferron).

In one refinery I visited, they routinely separated the metals to 99%+ , and then proceeded to re-refine them / purify them in several steps, that went relatively quickly, with routine lab equipment. The alloys of platinum are usually binary, so that helps a lot. It is rare to have more than 3 together, unless one melts them together. :shock:

Even ruthenium can be separated without distillation. That's handy because it is common as a platinum hardener.

Here's a summary of Raleigh Gilchrist's papers and life. A crash course in PGMs if there could be such thing. :lol:


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## g_axelsson

This is one of the best threads I've read for a long time. It deserves to not being forgotten so I'm bumping it up.

Thank you Lou, freechemist, butcher and everyone else that contributed to this thread!

By the way... is there a palladium analog to Ag2PtCl6? I'm getting an awful lot of white precipitate when I try to denox a palladium nitrate leach from MLCC:s. 

Göran


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## 9kuuby9

g_axelsson said:


> This is one of the best threads I've read for a long time. It deserves to not being forgotten so I'm bumping it up.
> 
> Thank you Lou, freechemist, butcher and everyone else that contributed to this thread!
> 
> By the way... is there a palladium analog to Ag2PtCl6? I'm getting an awful lot of white precipitate when I try to denox a palladium nitrate leach from MLCC:s.
> 
> Göran



Precipitate Ag with HCl as AgCl (to avoid this "Ag2PtCl6?" complex) let is settle then decant most of the solution and filter that last bit of solution with the AgCl together with the decanted solution. keep washing your AgCl until the solution becomes colorless and add the solution for filtering.

Ad more HCl to your Pd(NO3)2 solution along with heat and lots of stirring to convert it to PdCl2. (doubling the solution with HCl should suffice; any extra HCl will be used to Denoxx the solution afterwards)

denoxx the solution from NO2 (converting Ag to AgCl creates additional HNO3); then evaporate (with heat around 50C° and also some stirring) the solution down to 15ml to 20ml of solution per gram of Pd (average MLCC's yield max around 0.3% of Pd per gram of MLCC's) Then double the solution with HCl; then evaporate and repeat it for 3 times. Then evaporate it back to 15ml to 20ml of solution per gram of Pd. Now your solution is ready; for further selectively separating the Pd from the solution.


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## g_axelsson

9kuuby9 said:


> g_axelsson said:
> 
> 
> 
> This is one of the best threads I've read for a long time. It deserves to not being forgotten so I'm bumping it up.
> 
> Thank you Lou, freechemist, butcher and everyone else that contributed to this thread!
> 
> By the way... is there a palladium analog to Ag2PtCl6? I'm getting an awful lot of white precipitate when I try to denox a palladium nitrate leach from MLCC:s.
> 
> Göran
> 
> 
> 
> 
> Precipitate Ag with HCl as AgCl (to avoid this "Ag2PtCl6?" complex) let is settle then decant most of the solution and filter that last bit of solution with the AgCl together with the decanted solution. keep washing your AgCl until the solution becomes colorless and add the solution for filtering.
> 
> Add more HCl to your Pd(NO3)2 solution along with heat and lots of stirring to convert it to PdCl2. (doubling the solution with HCl should suffice; any extra HCl will be used to Denox the solution afterwards)
> 
> denox the solution from NO2 (converting Ag to AgCl creates additional HNO3); then evaporate (with heat around 50C° and also some stirring) the solution down to 15ml to 20ml of solution per gram of Pd (average MLCC's yield max around 0.3% of Pd per gram of MLCC's) Then double the solution with HCl; then evaporate and repeat it for 3 times. Then evaporate it back to 15ml to 20ml of solution per gram of Pd. Now your solution is ready; for further selectively separating the Pd from the solution.
Click to expand...

Thanks, I read about another trick (from freechemist) in avoiding creating the Ag2PtCl6 by pouring the silver - platinum nitrate into HCl. But that is still for dealing with platinum solutions. The solution from MLCC:s is silver - palladium based.
I made some searches and I could find many references to Ag2PtCl6 but no substance based on palladium instead of platinum. I haven't read up on PGM chemistry yet so I was wondering if there could be a similar compound created when I tried to denox my solution. I think I evaporated it too far and the next time I'll try your recommendations instead.
I tried to drop any silver before denoxing by adding NaCl but I didn't get any precipitate so I probably don't have any silver after all. I'm going to do some experiments with the precipitate to see if I can get it into solution again and find out what it is made of.

Göran


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## Richard NL

January 31st, 2012, 5:14 am


Lou said:


> For those who are interested in a historical work:
> http://books.google.com/books?hl=en&lr=&id=sok6AAAAMAAJ&oi=fnd&pg=PA7&ots=rZIrRnk-By&sig=bhq86Xr73VX9V6OpiJj22D6qlUc#v=onepage&q&f=false


Complete book:
https://www.docdroid.net/QxkICxV/the-chemistry-of-ruthenium-rhodium-palladium-osmium-iridium-and-platinum.pdf

Regards,


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