# Brainstorming the PGM ore.



## SapunovDmitry (Jan 16, 2014)

Hello Gentlemen,

How about some brainstorming.
Let's say we have the ore concentrate which consists mainly of Fe2O3 - (65%); Fe2O3/Cr2O3 - (15%); with the rest being FeOOH and alumosilicates.
Pt content of the ore is something between 200-800 gr/tn and daily amount of the concentrate is about 100 kg. I want that platinum badly.

I suggest a lead collector procedure.

Lead oxide is mixed with ore, soda, carbon and shredded glass. Then it is melted (5-6 melts with 15-20 kg of ore per melt).
Soda+ore+glass gives slag with Na2Cr2O7, NaFeO2, Na2SiO3, Na4SiO4 and other analogues with Ca, K being in the glass.
The mass of lead being extracted is something between 30kg/day with Pt content of 600-1800 gr/tn.

Now the fun part.....

Is there anyone with the experience of the oxidizing melts of PGM concentrates?

I want to perform an oxidizing melt in order to reduce the amount of lead from 30 to 3 kg.
I suggest melting it with pure quartz sand to get 2PbO*SiO2 glass, then shred it and return it to lead collector process next day.

The thing is that I badly want ALL, or at least 96-98% of my PGMs to remain in my 3 kg lead bar.

Is it somehow achievable or should i think of something else (for example electrolysis in acetic acid)?

Is there anyone having such an experience with oxidizing melts?

All other suggestions are welcome.


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## butcher (Jan 16, 2014)

Platinum and several of the platinum group resist oxidation.
most of the base metals can easily be oxidized.

As you noted you will form silicates in your melt and collect base metals in the glass slag like Iron, sodium...
lead also acts to form silicates (lead glass), when lead is in an oxidized state PbO, SiO2 and lead react with each other.

Silica SiO2 will combine with PbO to form lead glass silicate.
2PbO + SiO2 --> Pb2SiO4

Lead can be oxidized in the melt to litharge PbO using KNO3. 
Or the lead oxide in the melt can be reduced to lead metal in the melt with the addition of a carbon source, such as flour.
2PbO + C --> 2Pb + CO2


Lead metal is a collector of values in the melt, lead oxide will not collect metals and will react with glass to form the slag.

Lead can also be oxidize out side of the melt when heated strongly in an oxidizing atmosphere (like with an oxidizing flame from a torch, or a furnace with the door open in open air.

lead oxide as well as other oxides can be absorbed in a bone ash, Portland cement, or Magnesia crucible.

So in your melts you can oxidize lead using KNO3. Or reduce lead in your melts using carbon.

The other feedstock (or ore) in the melt can be oxidizing or reducing in nature, you can test this using lead or PbO, if the ore test melt oxidizes the lead to PbO it is oxidizing in nature, if the Ore test melt reduces PbO to lead it is reducing in nature, you can use this test to help decide your flux recipe to decide if you need to add an oxidizer like KNO3, or a reducing agent like flour as a carbon source...


I do not understand this comment:
" Melting it with pure quartz sand to get 2PbO*SiO2 glass, then shred it and return it to lead collector process next day".
This slag is a lead silicate glass and other base metal silicates, why would you want to return it to the collection process?


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## Adaptation (Jan 16, 2014)

I'm a novice but this is what I would try.

Dissolve out the Fe2O3 with acid, perhaps sulphuric. Then add sodium carbonate heat with an oxidizing flame until you have a molten goo with few solids. The Cr2O3 should turn into sodium dichromate which can be washed out with water leaving just you platinum groups.


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## SapunovDmitry (Jan 16, 2014)

to butcher
If you leave lead in a crucible and put just a bit of flux (you intentionally leave a space in the center of your melt exposed to the air) the lead will oxidize and form a crust that will dissolve in flux thus forming lead glass which will form bisilicate lead slag with a lead oxide maximum content of about 86%. By adding some additional flux and removing saturated one, you can reduce the amount of your metal. Saturated bisilicate lead slag is then shredded and used again in the first part of the next batch(the reducing one). 

The most important question here is if anyone has any real experience with that sort of process (I mean oxidizing lead to lead oxide and removing it from the melt).Because i personally have an intrinsic allergy on exposing metal to the air without the flux and slag at high temperatures, because for me it means lead oxide flying with off-gases and who knows what else it will take to the fume hood.


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## butcher (Jan 16, 2014)

Most of the lead you would want to oxidize in the melt and flux out in the slag as silicates, leaving a only small portion of the lead reduced as a collector, to collect the values, so that you do not have large volumes of lead mixed with your values, so you are not left with large volumes of lead to oxidize and cupel.
I only have played around with this on a small scale, to help me learn the principles, but I do not have experience on a larger scale.

I do not know if it would work, but I wonder if you used silver in the melt if you could use it to collect the Platinum group, and then use the Parkes process to seperate the silver and the lead, I wonder if you could get the PGM along with the silver scum.

Do you have to use lead as a collector, or could you use another metal?


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## Westerngs (Jan 16, 2014)

SapunovDmitry,

What you are proposing to do by reducing the lead by oxidation is merely a variation and upscale of the scorification process used in fire assay. If you read about it in the many assaying books, you will see that it is always associated with fairly large losses of values, sometimes as high as 5%. The losses are mainly to the lead oxide slag, but also to air emissions. If you return the lead oxide slag to the initial melting process, you will reduce the losses.

The air oxidation process stops once the slag builds up and covers the molten lead, so in your case it would be necessary to have a very shallow crucible with a large open surface to provide for maximum time to oxidize lead. I do not think you can get the 30kg of lead down to 3 kg. I have not seen a phase diagram for platinum/lead, but I think at a point near the 1:1 platinum lead ratio you will stop oxidizing lead. I could be wrong though.

I tend to agree with Butcher that a different collector metal would be better. I suggest copper because I think it will be easier to recover the Platinum values from copper than silver. Silver would work as well, but recovering all the Platinum values from silver would be a little harder.


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## skippy (Jan 17, 2014)

Platinum can be assayed with a nickel collector. Lead is usually not used - I guess there are problems getting complete assaying with lead, and hence probably a large scale molten lead collection isn't going to work too well for you either. They usually use nickel, or gold, but you probably don't want to use gold as a collector on the scale you seek :lol: 

Nickel collection, that puts the temperature of your melt a fair bit higher. Not as high as to directly collect the platinum like they do with cordierite auto catalyst in plasma furnace, but pretty high. You might check to see if a plasma smelter would be interested in your material though. 

Adaptations' idea is interesting, but the chromium in the ore could make for disposal problems for the solutions - it still could be worth looking into though. Concentrating your material perhaps by a factor of five is tempting. Might want to research chromium chemistry for leached chromite ore.

Have you looked into what platinum mines are doing with similar concentrates Dmitri? 
Would it be possible to leach the platinum out? It seems if all the iron is oxidized it might not be impossible to just dissolve the platinum with hot HCL plus chlorine gas. Particle size, agitation, concentrations, reaction time would all have to be played with. 96%-98% might be difficult. I know I read a paper out of South Africa on platinum recovery from concentrates using hydrochloric acid and hot chlorine sparging.


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