Sciencemadness Discussion Board

Extraction of platinum metal from Sperrylite (PtAs2)

kuro96inlaila - 17-4-2011 at 08:48

Few month ago I recieved few grams of sperrylite,from my uncle who is geologist.Sperrylite,which is an ore comprising Platinum and Arsenic as PtAs2.



P3242276.JPG - 129kB
Here is the picture of among the ores he gave me.

I want to extract platinum metal from this ore,which then I can use it to explore platinum chemistry.

But I am confused on how to extract the platinum metal from this ore safely,which arsenic is also present?
Burning this ore in big amount can be disaster.Releasing arsenic oxide fumes.And I've searched the internet there was no other info on sperrylite ore other than its geological info.If you all have any text on this compound,can we share it here?

I have thought some way to extract it:

1)By passing hydrogen gas produced by zinc and hydrochloric acid reaction which then dried to heated platinum arsenide,making platinum metal and arsine.

PtAs2+3H2--->Pt+AsH3

I plan to bubble the arsine in hydrochloric acid to yield arsenic trichloride solution.
Another way was to burn the gas produced and glass plate is placed in the flame to condense arsenic.Which is similar to Marsh's test.

But the I realised that arsine will start to decompose rapidly in 230C ,which I thougt reachable when platinum arsenide is heated.This would make arsenic produced back in the reaction vessel.

This way isn't reliable,it will not guarantee the positive result and who wants to "play" with among the worst poisonous gas - arsine?

2)Platinum arsenide ore is attacked in both HNO3 and aqua regia producing nitrogen dioxide gas.

With HNO3 it produce lemon tinged solution,while in aqua regia it produce orange coloured solution.
I don't know the product in this solution and how to extract platinum from both solution.

Below are the question I asked in short question thread 3,which was not replied since:
Quote: Originally posted by kuro96inlaila  
These make me confuse:

Yesterday,I decided to conduct a couple of experiments with my sperrylite (PtAs2) mineral.

1.I put about half a gram of PtAs2 in nitric acid.Then I heat it.Sperrylite react with warm concentrated nitric acid producing a yellow solution.Then I add few milimeter of ammonium chloride solution,hoping that ammonium hexachloroplatinate will be precipitated.But nothing happen.

I guess ammonium hexachloroplatinate only will be precipitated if ammonium compounds solution is added to chloroplatinic acid.While I might have platinum nitrate in the yellow solution.So,I add magnesium ribbon,hoping that platinum metal precipitated out.It first bubbled,then a brownish orange compound start to precipitated.

I can't figure what compound it is,so I set it aside and conduct other experiment:

2.I react PtAs2 with aqua regia,then I add ammonium chloride.But no ammonium hexachloroplatinate precipitated.Then I add sodium bicarbonate to the solution.It first bubbled,releasing carbon dioxide.Then a brownish orange compound start to precipitate.The colour is similar to what was precipitated in the other experiment.

So,what is these thing actually?I guess it would be either platinum dioxide monohydrate or sodium platinum chloride.But I also doubt it is an arsenic compound.

And,if this is platinum's compound,roasting it should turn it to platinum metal right?


here is the first experiment pic:


P4092331.JPG - 122kB
And for the second experiment:


P4092332.JPG - 141kB

And I heated the orange compound produced in the second experiment,its color stay unchanged.This lead me nowhere.

So I was confused on how to extract the platinum metal from this ore.Worst to come,how can I make it while disposing the arsenic safely?
Is there any method we can share here?

(Here is some text which may useful):




Attachment: Disposal of arsenic soluble compounds.pdf (289kB)
This file has been downloaded 877 times

kuro96inlaila - 20-4-2011 at 04:52

Any idea,anyone?:(

watson.fawkes - 20-4-2011 at 06:26

Quote: Originally posted by kuro96inlaila  
Any idea,anyone?:(
First, Google "disposal arsenic insoluble". Next, find paper Arsenic Disposal Practices in the Metallurgical Industry. Third, read abstract and see "scorodite, FeAsO4.2H2O".

Wizzard - 20-4-2011 at 07:00

Maybe not the most efficient way, but try superheating it in a vacuum, and distilling out the arsenic? It boils at a reasonable furnace temperature.

ScienceSquirrel - 20-4-2011 at 07:07

The best way would be to find an analytical procedure that uses something like aqua regia to dissolve all the metal content of the ore and then precipitates the platinum as say ammonium hexachloroplatinate.
A bit of book work could save you a lot of pain!

Fleaker - 20-4-2011 at 08:28

Ehh, the best thing to do is leave it alone. Sperrylite in small quantities is worth FAR more as a geological specimen than for the platinum content. It's a very rare mineral.

The conventional way to do this is to pulverise it and then roast in a stream of oxygen: the arsenic will distill as its volatile trioxide As2O3 (As4O6 dimer when distilling).

If you have to ask questions on how to do this, I really think you should not be handling arsenic at all, especially arsine gas.

Does your Uncle have much sperrylite? To the right people, it's worth quite a bit...

arsphenamine - 20-4-2011 at 12:26

Become familiar with meso-dimercaptosuccinic acid.

kuro96inlaila - 20-4-2011 at 22:36

@watson.fawkes
Thanks!

@sciencesquirrel
I'll try that and I'll tell the result soon.;)

@wizard
Yes,I've think that way too.But I forgot to include it in the first post.But currently I dont have any vacuum pump and cold finger apparatus.:(

@Fleaker
How about channeling the arsenic oxides into hydrochloric acid?so the arsenic oxides did not escapes to the atmosphere.

Well,I did not see myself but,he tell me that if I can find a way to extract platinum from it,he will give his 4kg of sperrylite.:o

@arsphenamine
That compound is used to chelate platinum ions right?

[Edited on 21-4-2011 by kuro96inlaila]

blogfast25 - 21-4-2011 at 03:45

Quote: Originally posted by kuro96inlaila  
Well,I did not see myself but,he tell me that if I can find a way to extract platinum from it,he will give his 4kg of sperrylite.:o



Even if you succeed in extracting small amounts of Pt from a small sample, you’d probably kill yourself/seriously poison yourself treating the 4 kg (choose your poison: arsine or arsenic trioxide!)

Tell your uncle that if he loves you he should give you the 4 kg on the proviso that you sell the stuff in small amounts using the ‘right channels’ and that you share the huge windfall with him. Alternatively have him send the stuff to moi, I’ll be eternally grateful! :cool:

ScienceSquirrel - 21-4-2011 at 04:11

Nice sperrylite is worth a fortune.
http://cgi.ebay.co.uk/HUGE-11MM-SPERRYLITE-CRYSTAL-NORILSK-R...
The 4kg must be worth thousands of dollars even if it is not very good.
The extraction is going to produce huge amounts of highly toxic waste containing large amounts of arsenic.
What are you going to do with that?

kuro96inlaila - 21-4-2011 at 06:39

Quote: Originally posted by blogfast25  
Quote: Originally posted by kuro96inlaila  
Well,I did not see myself but,he tell me that if I can find a way to extract platinum from it,he will give his 4kg of sperrylite.:o



Even if you succeed in extracting small amounts of Pt from a small sample, you’d probably kill yourself/seriously poison yourself treating the 4 kg (choose your poison: arsine or arsenic trioxide!)

Tell your uncle that if he loves you he should give you the 4 kg on the proviso that you sell the stuff in small amounts using the ‘right channels’ and that you share the huge windfall with him. Alternatively have him send the stuff to moi, I’ll be eternally grateful! :cool:


Well,that's why I want to discuss this thing with sciencemadness comunity,to get the most reliable and safe way to extract this metal.

@sciencesquirrel

Hm,I plan to save beautiful sample among those 4kg.I do not want to process all of the mineral.:)

Well,for the toxic waste,I plan to use the instruction in the patent I include in my first post.Just I don't really understand the method,the way they write the patent give me a headache.I need some explanation on that.:(

Or another way I will sent them to Enviromental department or waste processing centre to be disposed.

Fleaker - 22-4-2011 at 05:58

Are you in North America? I know multiple parties that would be interested in buying.

kuro96inlaila - 22-4-2011 at 07:00

Quote: Originally posted by Fleaker  
Are you in North America? I know multiple parties that would be interested in buying.


No,I did not live there.I live in Malaysia.

blogfast25 - 22-4-2011 at 08:31

Someone should calculate how many people you could outright kill with the arsenic from 4 kg of that stuff :o !

Definitely a case of a 'poisoned chalice'!

[Edited on 22-4-2011 by blogfast25]

unionised - 22-4-2011 at 08:58

About 10,000 people give or take a bit.
However it would be difficult t distribute the As evenly among them.

I think the best thing to do with the stuff would be to sell it in small quantities to collectors. But ,assuming some of it is not going to sell, then smelting for Pt is not a bad option. You need to do something with the As- trapping it as the oxide or as sodium arsenate would look like the best bet but, unless you are really sure what you are doing, I think you should sell it to someone who does.

plante1999 - 22-4-2011 at 09:09

i think leaching with sodium sulfite and sodium hydroxide mix and evaporate the leach to get sodium arsenate crystals.


pretty good idee to be acused of terorism act.....killing 6000 people.

[Edited on 22-4-2011 by plante1999]

kuro96inlaila - 22-4-2011 at 09:30

I think I determined to extract the platinum metal from this ore,I have think this since last year.

So let's clear things up,how the procedure is going on.At this time,the most reachable way for me is Fleaker's idea on reacting it with oxygen:



P4232471e.jpg - 147kB

the above setup is what I imagine currently.

Oxygen is generated from 32% hydrogen peroxide with small chunks of MnO2,perhaps my pyrolusite ore.Oxygen ore is channeled to gas washing jar,which contains anhydrous calcium chloride to dry it.Then it is channeled to long horizontal tube which contains PtAs2 powder in it.

PtAs2 powder will be heated to react it with oxygen.The product (arsenic oxides) will be distilled to another flask immersed in ice bath to condense it.This receiver flask (and tubes) will be leached with either sodium hydroxide or sodium sulfite solution to get sodium arsenate solution which will be treated later.

How is this sound?is there any change to make it better here?

unionised - 22-4-2011 at 09:43

Plante,
I don't think a reducing agent like sulphite would help here.

I would use a small pump like the sort used for aquaria to pass air over the stuff rather than using oxygen from H2O2.
I'd also put a second trap after the ice bath. A trap with sodium hydroxide solution would be sure to catch the last of the As.

I'd also not do this unless I was really sure what I was doing.

[Edited on 22-4-11 by unionised]

kuro96inlaila - 22-4-2011 at 09:45

so we go with sodium hydroxide?

blogfast25 - 22-4-2011 at 12:38

Pure oxygen isn't necessary at all, air oxygen will do, as unionised suggests. That's how roasting is done and that simplifies things at least a bit.

The crucial step is to capture ALL the As2O3, as well as mking sure the remainder of the ore is largely As-free.

Because you’re dealing with a seriously dangerous substance, you can make no easy or lazy assumptions.

For instance, pumping As2O3 vapours through an NaOH solution may sound easy peasy but it’s far from so. Your gas is very hot, remember? It would make your NaOH washer solution come to the boil immediately, so the air/As2O3 mix needs to be cooled firstly. Run it through an empty washer bottle immersed in cold water for instance. Much of the As2O3 will condense in it, the rest of this toxin can be captured by the NaOH wash bottle. Use strong NaOH for maximum capacity and add a second wash bottle, identical to the first, after the first (two wash bottles in series).

Your apparatus needs to be of high quality and seriously air tight and properly secured (stable). Fittings and joints subjected to high temperatures must be able to withstand those for prolonged times. Cobbling something together from ‘stuff lying around the house' WILL NOT DO.

After roasting, by no means assume your roasted ore is completely arsenic-free. The next step would probably involve digesting the roasted mineral in aqua regia. Most of the Pt should dissolve in it but arsine may be formed during that step. You need some way to capture all the arsine, 100 %. But even if no arsine is formed but some As was left in the roasted ore after digestion in AR, you’ll have AsCl3 in solution alongside the PtCl4. After separating out the Pt (as (NH4)2PtCl6 e.g.) the remainder of the solution and everything that’s been in touch with it is basically potentially highly toxic waste.

You firstly need also to find as much information on the process as you can muster: none of us here have any experience with roasting/treating an arsenic bearing mineral and our advice is theory based, not borne out of practical know how.

Start with very small quantities, then ramp up if successful.

The more I think about it, the more I’m convinced this is a job for a very experienced chemist and I still fail to see how you would process 4 kg of this stuff as an amateur and without being a serious polluter with a deadly by-product



[Edited on 22-4-2011 by blogfast25]

watson.fawkes - 23-4-2011 at 07:53

Quote: Originally posted by blogfast25  
For instance, pumping As2O3 vapours through an NaOH solution may sound easy peasy but it’s far from so. Your gas is very hot, remember?
This is a misunderstanding of the proposed apparatus. The idea is to condense As2O3 vapor to solid, to desublime it, as it were. The leaching step happens after recovery. This seems like a reasonable idea. It's also clear, however, that a single stage condenser just isn't going to be efficient enough. Even after you've condensed it all, there are still particle fines to worry about. So it's reasonable, but it still shouldn't be underestimated. All your other concerns about subsequent stages still apply.

I do have an idea about how this might be tried safely:
The combination of all these three would allow a small-scale experiment to be done with an inverted U-tube, with a T-branch at the top for vacuum evacuation and seal-off. It still requires glassblowing and a vacuum source, but that seems like a lower barrier to a safe experiment than other apparatus I can imagine.

Fleaker - 23-4-2011 at 08:53

I'd really wish he'd just desist. This is very dangerous to do and is NOT for someone with no experience in handling this material. As it stands, he'd probably get more money for the sperrylite on eBay international.

Sperrylite itself isn't really toxic and can easily be shipped as a mineral specimen.

I wish Chemrox would take a look at this...sperrylite has several different grades; is all of the ore a crystalline mass? It's likely not all PtAs2.

blogfast25 - 23-4-2011 at 10:05

Watson:

Yes, fine particulate matter (As2O3) is likely to be a problem on (de)sublimation. Industrially, electrostatic removal of the dust particles or by means of cyclones would probably be used. Capturing such a 'mist' in NaOH solution may not even work AT ALL.

Xenomorph - 23-4-2011 at 13:01

I am mineral colector and I can assure that sperrylite specimens of this quality are worth much more than platinum they contain and also have significant scientific value. Please, please, please do not destroy them, I beg you! You can not imagine how much it hurts my soul to se such specimens being destroyed! You can put them on ebay and get enough $ to buy at least 10 times more platinum. Good sperrylite crystals can be sold for many thousands of $. I hope this will change your mind
http://www.minfind.com/mineral-20513.html
I also would be interested in buying one of them but have not much spare money right now.

Best regards,
Xeno

arsphenamine - 23-4-2011 at 16:13

re: meso-dimercapto succinic acid
Quote: Originally posted by kuro96inlaila  

@arsphenamine
That compound is used to chelate platinum ions right?
[Edited on 21-4-2011 by kuro96inlaila]
It is used to chelate arsenic in blood plasma and in the GI tract.

kuro96inlaila - 23-4-2011 at 22:58

watson.fawkes:

Can you give a simple sketch on apparatus you imagine suitable for this process?

blogfast25:

After the oxygen treatment,I plan to first leach the resulting product in hydrochloric acid,which will dissolve the trace of As2O3,but not platinum.Then the undissolve substance (platinum) is treated with aqua regia,and then adding ammonium chloride to percipitate ammonium hexachloroplatinate.How does it sound?

Fleaker:

The PtAs2 sample I put on the first post isn't all crystalline mass.It is crystalline PtAs2 embed in some kind of black rock,I'm not sure what kind of rock it is.

xenomorph:

Don't worry,I myself is also a mineral lover.I'll save the unique and beautiful sperrylites.I'll use only chipped and scrap sperrylite in this experiment.On the plan to sell the mineral,I have to discuss this with my uncle first,we will see how it goes.

Arsephenamine:

I see.It would make an antidote for arsenical poisoning.

To all:

For the fine as2o3 particle,how about we introduced a system that spray fine mist of NaOH to the flask containing arsenic oxides?But I'm not sure the system is best introcued in either condensing flask,NaOH solution bath bottle or both after the roasting was done.

And,concerning this experiment require to heat the sperrylite for quite some time,I plan to use silicone stopper insted of all rubber stopper in the apparatus.

blogfast25 - 24-4-2011 at 04:23

Quote: Originally posted by kuro96inlaila  


blogfast25:

After the oxygen treatment,I plan to first leach the resulting product in hydrochloric acid,which will dissolve the trace of As2O3,but not platinum.Then the undissolve substance (platinum) is treated with aqua regia,and then adding ammonium chloride to percipitate ammonium hexachloroplatinate.How does it sound?

To all:

For the fine as2o3 particle,how about we introduced a system that spray fine mist of NaOH to the flask containing arsenic oxides?But I'm not sure the system is best introcued in either condensing flask,NaOH solution bath bottle or both after the roasting was done.

And,concerning this experiment require to heat the sperrylite for quite some time,I plan to use silicone stopper insted of all rubber stopper in the apparatus.


Yes, selective leaching of the residual As from the roast maybe possible using the strongest HCl possible and using finely ground (high quality dust mask needed!) roasted ore. I’ve no experience with dissolving As in HCl but you should be able to find some relevant information on the net.

As regards capturing any fine particulate As2O3 matter using a spray, again that’s not a bad idea but will it work in practice? It depends largely on the wetting behaviour of the arsenic particles. Spraying would be best done in the last wash bottle.

I don’t much like the idea of silicone stoppers, unless they have been formulated and specified for use at some temperature. The heat and chemical resistance of silicone rubber varies HUGELY from one type to another. I’d prefer ground glass connectors, or Teflon or Viton based stoppers/connectors. Much depends on the temperatures reached of coarse but to successfully roast the ‘Satan’s Excrement’ you’ll need to reach about 800 C (or so I’d imagine). That can lead to any connectors down stream from the roasting area to seriously heat up.

Here’s an idea: ask your uncle to allow you to sell one or two fine specimens and invest the money in the best kit money can buy (as well as an antidote against As poisoning)

watson.fawkes - 24-4-2011 at 06:47

Quote: Originally posted by kuro96inlaila  
Can you give a simple sketch on apparatus you imagine suitable for this process?
I could, but I'll decline. This experiment is one where if you can't fully work out all the engineering consequences, you're at life risk.

It's occurred to me that you might proceed in doing some primary metal recovery by selling some of the sperrylite and acquiring a different primary platinum ore with fewer toxicity issues.

Neil - 24-4-2011 at 06:51

Route to 5Npure Pt from Sperrylite

The Sperrylite is first classified by size, shape and crystal habit.

The material is classified, photographed, numbered and placed into lined envelopes

The photos are then uploaded into Ebay where the samples are sold off to the highest bidder.

Using the funds recovered, 5N Pt is purchased and adored.

Doing a Google search suggests that it is possible for Sperrylite to sell for up to nine times the value of an equal weight of platinum, which means it is being sold for up to fifteen times the value of the contained Pt.

This is not uncommon for the rare ores of metals - for example, gold nuggets are normally worth two to five times the value of the gold if it were rendered to bullion.

Once samples are sold, purchase a large amount of Pt bullion and enjoy. Alternatively use the money from selling several pounds of the Sperrylite to purchase the equipment to remove the Pt safely from the remaining Sperrylite.

Bottom line, you are killing the goose for a golden egg if you break the stuff down. Refining metals is a very tricky and slow science. I’d google “Hoke” and try and find her book. Until you’ve memorized it, you’re more likely to lose values then gain metal.

Even if you are only getting twice the value of the metal in selling the ore, you’re still going to have a fortune, where as if you go through with the extraction on your own you're more likely to have large amounts of toxic sludge and several beakers full of PT solutions along with whatever else dissolved in the acid leach.

If you do manage to precipitate pure Pt, you still have to melt it without blowing the dust across the room.

Do to the toxicity and complications of working with values and the needed degree of safety, it is also very possible that you will spend more money on extracting the metal then you will gain by selling whatever values you recover.

Whatever you chose, good luck!


350$ 3mm crystal
http://cgi.ebay.ca/Sperrylite-Xl-Rare-Platinum-Mineral-TL-Su...

1056.00$ 3cmX4Cm piece of ore
http://www.adamsminerals.com/store/shop.php/adams-picks/sper...

Refining Precious Metals Wastes by CM. Hoke

Neil - 24-4-2011 at 06:57






http://www.scribd.com/doc/2815953/Refining-Precious-Metal-Wa...

Fleaker - 24-4-2011 at 07:23

Well said Neil. He can even afford to pay the 3X over spot that 5N zone refined platinum commands (as typical refining produces only 4N material).

kuro96inlaila - 24-4-2011 at 10:03

Quote: Originally posted by Neil  
Route to 5Npure Pt from Sperrylite

The Sperrylite is first classified by size, shape and crystal habit.

The material is classified, photographed, numbered and placed into lined envelopes

The photos are then uploaded into Ebay where the samples are sold off to the highest bidder.

Using the funds recovered, 5N Pt is purchased and adored.

Doing a Google search suggests that it is possible for Sperrylite to sell for up to nine times the value of an equal weight of platinum, which means it is being sold for up to fifteen times the value of the contained Pt.

This is not uncommon for the rare ores of metals - for example, gold nuggets are normally worth two to five times the value of the gold if it were rendered to bullion.

Once samples are sold, purchase a large amount of Pt bullion and enjoy. Alternatively use the money from selling several pounds of the Sperrylite to purchase the equipment to remove the Pt safely from the remaining Sperrylite.

Bottom line, you are killing the goose for a golden egg if you break the stuff down. Refining metals is a very tricky and slow science. I’d google “Hoke” and try and find her book. Until you’ve memorized it, you’re more likely to lose values then gain metal.

Even if you are only getting twice the value of the metal in selling the ore, you’re still going to have a fortune, where as if you go through with the extraction on your own you're more likely to have large amounts of toxic sludge and several beakers full of PT solutions along with whatever else dissolved in the acid leach.

If you do manage to precipitate pure Pt, you still have to melt it without blowing the dust across the room.

Do to the toxicity and complications of working with values and the needed degree of safety, it is also very possible that you will spend more money on extracting the metal then you will gain by selling whatever values you recover.

Whatever you chose, good luck!


350$ 3mm crystal
http://cgi.ebay.ca/Sperrylite-Xl-Rare-Platinum-Mineral-TL-Su...

1056.00$ 3cmX4Cm piece of ore
http://www.adamsminerals.com/store/shop.php/adams-picks/sper...


That good way too!
Obtaining more profit that way.
I'll discuss it later with my uncle on what to do with that huge amount of sperrylite.

But I might (just maybe) do just one experiment to find out whether it can extract platinum or not.

blogfast25:

"Satan Excrement",lol.:D
Good name for vintage looking bottle containing arsenic oxide!;)

arsphenamine - 24-4-2011 at 20:57

Quote: Originally posted by kuro96inlaila  
Arsephenamine:

I see.It would make an antidote for arsenical poisoning.


Later detox research references the administration of isoamyl mono-ester of
meso dimercapto succinic acid with taurine as a superior arsenic sequestration protocol.

Lest you disregard this as irrelevant, briefly consider my account name.

As is extremely toxic

lithea - 30-4-2011 at 13:59

Lethal dose of As2O3 is cca 100 mg ! Arsine is very toxic gas !

It can be made, but not by amateurs, it is very dangerous. First of all is needed to know, if it is really sperrylite. If yes, how pure it is, what is Pt content. Ore is not homogeneous. Samples with crystals are rare, these are better to sell separately on ebay.com. Samples without crystals can be processed for Pt.

Processing let to professionals - analytical chemists with laboratories. I am an analytical chemist and geochemist, I would process it, but have no idea how to do it with borders. If you send it uninsured, it is risky and if insured, customs officers will be crazy.