PGM recovery diff method.

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kjavanb123

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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.
concentrated AR 15 minutes into boiling.jpg

Solution at room temp.jpg

Now evaporating the NOxx from the solution using steam bath.
solution evporating the nitric started.jpg

Few mins into NOxx evaporation and the color of solution changed.
solution 10mins into evporating the nitric.jpg

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

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
 
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
 
There is a misunderstanding about ammonium chloride - should be added
and heated - but be in excess to ensure saturation
 
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
 
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
 
Yes, as long as the solution is concentrated enough to facilitate the colored salt to crash out.

Steve
 
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.
 
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
 
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?
 
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.
30ml of solution NOxx removal.jpg

Saturated ammonium chloride solution
20ml water plus 6grams NH3Cl.jpg

After half and hour or so, it seems like the solution is turned into a syrup.
30ml solution evaporated to syrup.jpg

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

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.
close up of left over.jpg

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
 
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
 
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
 
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
 
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
 
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 :

pt_18g_sol.jpg


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
 
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.
 
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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