Nitric and Palladium

Hello guys (and gals),

Dose anyone know how much Palladium would be dissolved in Nitric acid at room temperature before all copper is digested?
Lets say ... I have 100g of material of which 2.5% is Palladium, 2% Gold 0.5% Platinum, 8.5% Silver, 0.8 Nickel and 85.7% Copper, it will take 2-3 hours for nitric to dissolve all the silver and copper, during this time how much of my Palladium would be dissolved in Nitric? I know it dissolves slowly but how slow?

Thank you!

Maybe i'm mistaken...
but i think it is next impossible to pre determine what you seek for...

On different matter, did you ever consider rasing the Cu content to >95% and simply part it electrochemically?
This way you would be left with slimes containing mostly PM's with very little Cu contaminate... sure will save you on acids...

Or couldnt you remove the copper with HCL

Thanks for reply, guys.

Samuel, I can not do it electrochemically as it's in a powdered state contaminated with glass, I could dissolve all in Aqua Regis and then use Zinc (or hydrazine, which is expensive but would drop more metal) to drop all metals, but ... I have 1.25 tons of this ... and not sure which will be the cost effective way of doing it. Glass contamination is about 68% plus some 2-3% polymer, which I will vaporize and distill.

shadybear, To dissolve it in HCL I will have to add Hydrogen Peroxide, what will produce small bubbles of Chlorine and form Auric Chloride (am I right?).

hcl acid alone will not dissolve gold or copper. add the material in question to hcl acid in a chamber big enough to hold the volume of material and chemicals with 1/4 of available space left. add H2O2 (peroxide) to the mix of a ratio of 1 US cup to 1 US gallon to start the reaction. it will immediately turn yellow then quickly turn green. add a source of oxygen such as an air supply in the form of a bubbler, if you are doing batches in a plastic drum you may need to use several, maybe 4 if your volume of chemicals is 30 gallons or more. set the air bubbling and leave it alone for 4-5 days, if the copper is bare copper as in particulate form it will go much faster. this will put the copper and tin in solution without effecting the PM's. after the solution turns brown to brown/black dip or siphon liquid down to the powders in the bottom and you have successfully removed the copper and tin from your material.

What if I get rid of polymers and melt the glass and metal ?
What will I end up with?
Any toughs?

OK... I'm going to try that tomorrow in the lab

P.S. The thing is I have 400kg of copper and not sure the best action here, if it was an alloy the best option was electrolysis.

xsspirito said:

What if I get rid of polymers and melt the glass and metal ?
What will I end up with?
Any toughs?

OK... I'm going to try that tomorrow in the lab

P.S. The thing is I have 400kg of copper and not sure the best action here, if it was an alloy the best option was electrolysis.

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If I understood you correctly, by using the present PM prices (which are dropping rapidly), I came up with these approx. dollar values: Pd-$177K; Au-$378; Pt-$93K; Ag-$33K; Cu=643#. Not including the Cu (which I wouldn't worry about), that's a total of about $681,000, if I did the math right. If this were mine, I would do a lot of experimentation to find the best and most efficient method, changing only one variable at a time. I would also want to own an AA (for the liquids) and fire assay setup (for the solids and maybe the liquids) to track the metals through the experiments and the process.

These ideas are just that, ideas. They may or may not work. They look good on paper but, when actually doing it, things crop up that you hadn't considered. However, you have to start somewhere. I'm sure there are other possible ways. Maybe, Lou, Harold, 4metals, and others can chime in.

Eliminating the organics and then melting was also my first thought. If you can make it work, that would certainly be the cleanest way to go. Ideally, you would end up with assayable bars containing all the metals, which you could either deal to a large refiner or process yourself (let's deal with that later), plus a lot of slag which could easily hang up BBs of metal unless you could thin it properly (maybe, fluorspar). The melting point of most glasses is quite high, but the melting point of many can be lowered (to maybe 1000C) by the addition of definite quantities of sodium carbonate. At this temperature, you could use a gas furnace. If the slag is thin enough, most all of the BBs will settle by casting into a large size, pre-heated, cast iron, cone mold, if you can keep the slag molten long enough. I have also heard of people casting into a large cone-shaped depression formed in pre-heated casting sand. That would keep everything molten for a long time.

If all the individual metals, glass, etc., are in separate particles, and the metals are not alloyed or bound up with the glass, you could leach out all the Pd, Ag, and Cu with nitric. For the whole lot, I estimate it would take about 600 gallons (11-12 drums) of 70% nitric cut 50/50 with distilled water and heated. You could use a non-magnetic stainless tank for the nitric. After this, I would use a huge vacuum filter and rinse well. Then, leach the Au and Pt with either aqua regia or HCl/strong H2O2. The latter might be best since you wouldn't have to deal with the elimination of excess nitric before dropping the metals. Besides being able to rinse all the values in solution from all of that glass, the biggest problems I see are dropping the Pd from the nitric solution and all of that dissolved copper present. Any excess of nitric will have to removed first. Therefore, try to use only a slight excess of nitric, no matter how slow it goes. To me, the simplest way to remove an excess of nitric is to use sulfamic acid.

http://www.goldrefiningforum.com/phpBB3/viewtopic.php?f=51&t=10799&p=105096&hilit=sulfamic+acid#p105096

You could probably leach everything but the silver with aqua regia or HCl/H2O2 (possibly best), and then go after the silver with nitric. However, depending on the particle size, a certain portion of the silver could be converted to silver chloride. This wouldn't dissolve in the nitric and would possibly be lost, since leaching out AgCl with ammonia, sodium cyanide, or sodium thiosulfate would be a bear.

What a great post Chris.

Though, i'm still in the opinion that he will benefit from melting and parting in a cell, even with the high silica content.
As GSP suggested, there are ways around that such as soda ash + fluorspar...

If it were me, i'd probably out source the smelting process to a professional smelter and ask 50-100 kilos anodes + all of the slag back (which will need to be assayed).

GoldSilverPro, Thank you for detailed reply.

Your math is right I was thinking of £400,000, and of course TESTING, I would say a lot of testing.
I have already tested a batch, chemically dissolved and recovered all metals including traces of the nickel.
I have a full lab so I can do lots of experiments.

First will try to melt with induction furnace, it's 30L (8 Gallons) so if successful will take me about 50 loads. Ideally it should work as 30% of the mass is metal. If it wont work will have to find a gas furnace. BUT! Some oxides, sulfates and metals mix in with glass, it might be a problem, not sure but ...

Will let you know tomorrow. ITS COOKING

Considering the high percentage metals in the material I would definitely start with melting. A good flux for this type of material can be made as follows;

15% Kryolite
35% Borax (anhydrous)
25% sodium nitrate
12 1/2% soda ash
12 1/2% slaked lime

This flux has served me well melting high yield ceramic substrates and there was only a minimal hold up in the slags which can be crushed and shipped as a low grade sweep to a copper smelter. Considering the high percentage of metal this flux can be mixed as 1 part flux to 3 parts of the glass metal mixture and you should get a nice thin slag for easy pouring. If it is not a fluid slag, slowly increase the flux proportions but you shouldn't have to go over 35% by volume flux.

The kryolite, which is sodium hexaflouroaluminate will perform as the the flourospar in GSP's suggestion to thin the flux and minimize the bead hang up.

I would pour these melts into a cone mold and closely examine the glass slag which should be a black color and free of beads with the right proportions. Once you come up with the right flux to material mix, assay the bar to determine the copper percentage and upgrade the copper content to make this a copper plating cell with very happy slimes.

My second choice would be the acid leach but unless you are in a well equipped and exhausted refinery, the fumes may be a bit much. Plus without good rinsing and vacuum filtration, the glass particles (depending on their shape and surface finish) may trap more values than you are willing to lose.

Would you be willing to sell small quanties of your material to come up with an answer? Say 0.5 - 1 pound samples?

OK guys, BAD news.

I melted it, and ended up with a very strange material, first of all glass turned greenish blackish brownish mass (or mess).
I added Borax, sodium nitrate, soda ash to bring the melting temperature down, it melted at 1240 C.

1. It should not have turned green, this indicates presence of tin oxide? Wen I refined a small batch first time, I boiled it first with Hydrochloric acid, and did not test for tin, further more the vacuum tubes did not have any solder on them.
2. I managed to get some metal to settle on the bottom about 20-22% of it, the rest is suspended in the mess (bead hang up).
3. I tried at range of temperature, the higher it got, the darker became the mass. I even boiled it which made a bigger mess out of it.
4. After it solidified I pulverized it, used a strong magnet to separate metals (I have a little nickel in the metal), ended up 15% short of what it was supposed to be.

Solution 1: I have access to atmospheric polymer distillation reactor (made from wolfram alloy), I can have the temperature increased from 700C to 2750C. WHAT IF I try to vaporise some of the materials and then distill it? The reactor has 3 distillation chambers at different temperatures. I know it sounds funny.

Solution 2: Do you think I can use a conductive polymer paste to bond the material and then try to clean it electrochemically, as suggested by Samuel?

Solution 3: Good old chemical leaching method.

P.S. I will try method suggested by 4metals today and post the results.

BTW how can I test the chemical composition of the galls I have? It might be some sort of an exotic glass. Will atomic absorption spectrophotometer work on glass?

The glass has to be crushed into a fine powder and fused in a litharge based flux and the resultant lead is cupelled, resulting in a dore bead containing total precious metals. That bead can be digested and fire assayed.

xsspirito said:

Solution 2: Do you think I can use a conductive polymer paste to bond the material and then try to clean it electrochemically, as suggested by Samuel?

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That was not my suggestion.

To part your material electrochemically, it depent on you melting your metals successfully and evenly.

Follow 4metals flux recipe and tweak it as needed. I also hope you will give it enough time to pool at the bottom.

Want to sell it?

Sorry guys, I can't sell it.

Just thinking about this.

Is this from vacuum tubes?
Could you look at this similar to mining, what size particles are the metal? If product was crushed fine would glass be smaller powder than metal, and maybe screened from metal (or majority of metal, or could metals be reduced in size (if already almost smaller than glass) with acids (not necessarily completely dissolved) and screened from glass?

Or

Could both be powdered and panned (shaker table or other mining method), glass would be lighter. Even if you did not get complete separation it may save acids, or fuel for furnace, and could limit waste generated.

Hello xsspirito,

Having read through all posts covering your problem, I stumbled over goldsilverpros answer, in which he makes a rough estimation about values in the material and quantities of nitric acid required, to leach out Pd, Ag and Cu, provided that all the individual metals, glass, etc., are in separate particles, and the metals are not alloyed or bound up with the glass. Under the same propositions the entire metal values, Cu, Au, Pt, Pd, exempt silver, could be leached out with a HCl/HNO3-mix, suspending the material to be treated in HCl, diluted with water, heating to ca. 80oC-90oC, and slowly adding HNO3 as oxidizer in such a manner, that reaction never becomes too violent. Thus, calculating the quantities of 32% HCl, 65% HNO3 and water, I came upon the following total numbers: 1'740 liters of 32% HCl, diluted with 870 liters water, and 470 liters of 65% HNO3 to oxidize all metals. Ideally you end up with a solution of Au, Pt, Pd and, of course the total Cu, and a residue consisting of glass- and polymer particles, together with some AgCl and undissolved metallic Ag. The filtered solution will contain maximally up to 3 g Au/liter, 0.7 g Pt/liter, 4 g Pd/liter. In place of cementing, this solution could be treated with a strongly basic anion-exchange resin in chloride-form, like Amberlite IRA-410, produced by Rohm & Haas, which in bulk-quantities probably will cost you about 20 - 30 $ per kg. This resin will absorb Au, Pt, Pd from the filtered solution as complex anions AuCl4(-), PtCl6(2-), PdCl4(2-) (and PdCl6(2-), eventually). The resin can be loaded with up to 10% of it's dry weight with precious metal-anions, leaving the copper (and also nickel) untouched, in a solution containg ca. 1 to
only a few milligrams precious metal in 1 liter. Thus, assuming a total of roughly 20 kg Au+Pt+Pd a minimum of about 200 kg of resin (4'000 to 6'000 $) are required for nearly quantitative absorption of total pm-values. After, the loaden resin can be carefully burned down and calcined (end: 800oC to 900oC) to a finely divided, essentially metallic residue.
An alternative approach, to work up the material would be, to dissolve the glass particles in hot concentrated aqueous NaOH under pressure at 150oC to 200oC, calculating the weight of glass as SiO2 (quartz), like ordinary water-glass is produced by dissolution of quartz at high temperature and high pressure. On filtering, the silicate solution is separated from metal- and probably polymer-particles, and this residue could be burnt, melted and further treated by known methods. Even another alternative is the dissolution of glass in an excess of hydrofluoric acid, producing a solution of H2SiF6, Na2SiF6 (and excess HF), from which metal and polymer particles can be separated by filtration.

Of course, like goldsilverpro stated in his post, all these suggestions mostly are just ideas, exempt the resin-treatment of precious-metal-solutions in presence of high copper-concentrations.

Good luck and regards, freechemist

4metals said:

This flux has served me well melting high yield ceramic substrates

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Can you elaborate? Do you mean crushed/ground substrate?Or in cpu form.I am looking for a more thorough method for extraction from crushed substrate,as opposed to thio.The fine powder is a huge pain when using thio on ground substrate.

Back in the day, I melted ceramic hybrid circuits (thick film ) whole with this flux mixture. The melt often stayed in the furnace for 8 hours to liqueify the substrates. Copper was used as a collector and the bars were electrolytically refined in a copper sulfate cell, the anode slimes is what we were after.

Considering the high copper in the material described in this thread, minimal or no copper would need to be added, that is why I would choose melting first.