Inquart mixed PGM's?

[Geo]

I have managed to produce metal with Pt, Pd and Rh by smelting filter ash. I am wondering if it is feasible to inquart this metal with silver and leach in nitric acid as you would with karat gold. It would digest the silver and palladium leaving only Pt and Rh. It is much easier for me to get a 2-way assay than a 3-way assay. I have found a reputable refiner that will accept relatively small amounts of a couple of ounces at a time. Is this something that can be done or is there a chance of dissolving Pt or Rh with just nitric acid?

 

[orvi]

I have managed to produce metal with Pt, Pd and Rh by smelting filter ash. I am wondering if it is feasible to inquart this metal with silver and leach in nitric acid as you would with karat gold. It would digest the silver and palladium leaving only Pt and Rh. It is much easier for me to get a 2-way assay than a 3-way assay. I have found a reputable refiner that will accept relatively small amounts of a couple of ounces at a time. Is this something that can be done or is there a chance of dissolving Pt or Rh with just nitric acid?

When I worked with PGMs, we have done experiments, when we alloyed PtRh in copper and aluminium, 20% PGMs concentration, 87:13 Pt:Rh ratio. When dissolving copper PGM alloy in nitric, we observed good ammount of Pt going to the solution. When dissolving alloys in nitric, there is always some Pt dissolved to the liquid, but not all of it. Rhodium required few days boiling in nitric (65%) to appear on XRF, leached into the solution very very slowly.

Inquarting with silver would work, but I cannot say what PGM content would be OK in terms of working temperatures. PGMs quite sharply raise the melting point of the alloy.

Alternatively, dissolve everything to the HCl/Cl2 and selectively precipitate Pd with DMG, if it isn´t too much of the material.

 

[Geo]

When I worked with PGMs, we have done experiments, when we alloyed PtRh in copper and aluminium, 20% PGMs concentration, 87:13 Pt:Rh ratio. When dissolving copper PGM alloy in nitric, we observed good ammount of Pt going to the solution. When dissolving alloys in nitric, there is always some Pt dissolved to the liquid, but not all of it. Rhodium required few days boiling in nitric (65%) to appear on XRF, leached into the solution very very slowly.

Inquarting with silver would work, but I cannot say what PGM content would be OK in terms of working temperatures. PGMs quite sharply raise the melting point of the alloy.

Alternatively, dissolve everything to the HCl/Cl2 and selectively precipitate Pd with DMG, if it isn´t too much of the material.

Thank you.
I'm sorry. I meant to say, add silver during the first smelt. My idea was to use cemented silver that is very nearly a powder as is. Just add the silver to the ash and flux and mill it all together. It can act as a collector metal and then leach the bead in nitric acid. I haven't tried yet. I was hoping someone has already tried and can give some insight on what they achieved. I haven't smelted the material the first time yet, only a few samples.

 

[orvi]

OK, that is bit new idea to me.
But all in all, why not. I will give it a try, it sounds like a good idea. If I am not missing some obvious things and problems
In the similar fashion as litharge smelting, I think you should be able to add like powdered silver oxide and it should be similar in action. But why not cement silver instead, clever
I would go for a test run, for sure.

 

[samuel-a]

Jeff,
Do you have an Rh assay for the initial ash material?
I would concern with the collection efficiency of Rh.

 

[nickvc]

Geoff with enough silver PGMs will dissolve with nitric which you can then use HCl to form silver chloride to filter off then cement the PGMs on copper then dissolve any Pd using dilute nitric which you can cement out , that should leave you with the Pt and Rh and I’m thinking that as Rh is very un reactive you may be able to separate by dissolving the Pt in AR leaving the Rh behind, none of the above may produce perfectly clean separate elements so further refining may be necessary depending on your needs.

 

[kurtak]

I have managed to produce metal with Pt, Pd and Rh by smelting filter ash. I am wondering if it is feasible to inquart this metal with silver

Geo - concerning the Rh Sam has a valid point --- Sam posted ------

Do you have an Rh assay for the initial ash material?
I would concern with the collection efficiency of Rh.

Here is a discussion wherein Lou made me aware of this back in 2016

https://goldrefiningforum.com/threads/buttons-and-bars.24639/#post-261083
I did have "some" gold in that smelt & I did recover "some" Rh when I processed the cones --- the question is - was it enough gold to actually get "good" recovery of the Rh - or did I suffer loses & if so how much loss - I will never know because like you the Rh was in filters so no idea how much Rh was in the filter ash to start with

Concerning the Pt - Yes - When alloyed with silver at least some Pt will go into solution with nitric - how much depends on the ratio of Pt to Ag

So - I guess the bottom line I am getting to is that you may be better served using gold as your collector metal - then go to AR which will dissolve Au/Pd/Pt (& likely "some" Rh) but leave most of the Rh behind (somewhat dependent on alloy percentages/ratio)

Then drop your gold with copperas - then drop the Pd with DMG (or other precipitant "selective" for Pd) then your Pt (ether with selective precipitant or cementing)

OR - after dropping gold with copperas - cement the Pd/Pt - then use nitric to dissolve the Pd from the Pd/Pt cement - then (again) cement the Pd from the nitric

To be clear - none of this is perfect - the separation/refinement of PGMs (especially when mixed) is a difficult task at best - due to their close relationship to each other they tend to follow each other (to some degree) so generally need to go through re-refining steps to get true separation

Which is why (unless already pure) they pay less for PGMs &/or why assays cost more

THEN - if there is also (already) silver in those filters - it adds another complication (to the above) depending on the amount of silver - IF - after smelting/alloying Au/Pd/Pt/Rh & there is only trace amounts of silver it's not a big problem - however IF the silver is to high in the alloy then the AR will have a hard time due to AgCl crusting on the surface during the dissolve

Bottom line - gold &/or (other) PGMs need to be high enough to prevent loosing Rh in the smelt

OR - if you have enough of these filters you "may" be better served to just send them in - take the hit on the payout AND the added cost of higher assay fees

As we know - working with PGM salts is a VERY toxic process - even if you know/understand the process & take proper precautions !!!

As you know - we have lost a few members to the refining of PGMs - that knew what they were doing !!!

For what it is worth

Kurt

 

[snoman701]

how much ash are we talking about?

 

[Geo]

Jeff,
Do you have an Rh assay for the initial ash material?
I would concern with the collection efficiency of Rh.

I sell to Elemetal Direct. I know the hard feelings some have towards the company but they have always been good to me. The associate that I deal will will assay a couple of samples for me every time I go in. He can't print a report as it only prints an invoice on sales but he lets me stand with him to read it for myself. The two samples I took was from different locations in the container. The first sample had 1.48% Rh along with all the various other metals you would expect. The other sample was 1.89% Rh. I have 9.6 pounds of milled and screened ash.

 

[Lino1406]

Literature says. Rh will not dissolve in silver

 

[orvi]

I sell to Elemetal Direct. I know the hard feelings some have towards the company but they have always been good to me. The associate that I deal will will assay a couple of samples for me every time I go in. He can't print a report as it only prints an invoice on sales but he lets me stand with him to read it for myself. The two samples I took was from different locations in the container. The first sample had 1.48% Rh along with all the various other metals you would expect. The other sample was 1.89% Rh. I have 9.6 pounds of milled and screened ash.

That sounds like a pay-day

 

[nickvc]

Literature says. Rh will not dissolve in silver

Lino is the literature true because if so Geoff has an easy way to separate the Rh.

 

[Yggdrasil]

I remember Lou say the same thing.
Gold is best and Copper work, Silver not so good.
So I'm guessing Silver pick up some, but not to a usable extent.
As Nick say, maybe a sufficient method for concentrates.

 

[Lino1406]

Phase diagram for silver rhodium shows that. I agree that copper is more suitable

 

[Geo]

I knew I was going to market today so I took another sample from a different spot and decided to go ahead and sell this one and get a print out. He also noted all the metals in the sample. The Rh was nearly double from the first two. They only pay on the dominant metal unless specified. So this is what I'm fighting.

 

[orvi]

I knew I was going to market today so I took another sample from a different spot and decided to go ahead and sell this one and get a print out. He also noted all the metals in the sample. The Rh was nearly double from the first two. They only pay on the dominant metal unless specified. So this is what I'm fighting.View attachment 49564

You are in similar situation that I was a year ago but my Rh percentage was more about 1-2%. Buyer over here paid only for metals with content higher than 15%.

14% Pt and more importantly 3,8 % Rh... That is a lot of value to be thrown off...
But you are in better position than I was, your Rh content is higher, so some home chemistry of "concentrating" individual metals could work relatively fine, and able you to get some decent percentage of Rh out as separate fraction.
If I was to do something with it, I will get rid of base metals and silver (easy one). This will bring the concentration of Rh in cemented metals even higher - you have roughly 20% "junk" inside.
Than I will focus on precipitating palladium - in smaller quantity with DMG.
Otherwise the second step will be platinum scavenging with stoichiometric NH4Cl. And then precipitation of (NH4)2PdCl6 salt. Both of tthese operation will drag some Rh to the precipitates, but I think you can get Rh fraction with more than 30% Rh content, which should be sellable.

Good luck with refining. I hope that you manage to get it out

 

[Justincase]

The Rh was nearly double from the first two. They only pay on the dominant metal unless specified. So this is what I'm fighting.

I have found this problem.
I was introduced to the owner of a very old and well-established refinery who was very friendly, we agreed to a very good level of liquidation and assistance.
I was quite chuffed as he does not normally even take a phone call let alone talk to and help someone so small in the industry.
Was told to talk to his people.
First, his refinery manager tried to take eight years of waste concentrate and only pay me for the silver return.
I asked about the other elements and pointed out the high Rh content which I would at least like to know about, was told tuff, and asked with incredulous ruddiness "Why would you want to know that".
I was flabergasted at the deliberate misinformation by one of the largest operators in the country.
So I called the facility manager to try and talk to the owner again, once I had explained the situation she called me "A Fantasist" and would not even try and ask the owner about our conversation.
I was very insulted and disapointed.
Having to build a much larger furnace so I can process the waste myself in the largest crucible I can manage, But still have not found anyone to help liquidate the P.G.M.'s without accessing it through my rectum.

 

[nickvc]

The problem you will have is PGM refining is still very much a closed shop and not all refineries actually refine it but concentrate and pass onto one that does who can set their own terms as to returns and what they will pay for, nice for them bad for the small refiner.
The only suggestion I have is if you have decent amounts is to either melt and get Sheffield to assay the bar or crush and sieve mix well and take several samples and have them assayed and then approach one of the refiners who does actually refine PGMs but as I said it’s very much a closed shop.

 

[Justincase]

The problem you will have is PGM refining is still very much a closed shop and not all refineries actually refine it but concentrate and pass onto one that does who can set their own terms as to returns and what they will pay for, nice for them bad for the small refiner.
The only suggestion I have is if you have decent amounts is to either melt and get Sheffield to assay the bar or crush and sieve mix well and take several samples and have them assayed and then approach one of the refiners who does actually refine PGMs but as I said it’s very much a closed shop.

I did do quite a large recovery for a client that was a Payne by name and a pain by nature.
Some were in the £15,000 range.
We initially sent a sample of Platinum(II)-ammonium chloride to Sheffield who gave a very low return considering the sample was quite pure and very dry.
Turned out they had calcined the salt in an open furnace.
That did not really strike me as very efficient so I declined to settle based on that return.
So my client took the entire lot to J.M. as it was just inside their threshold for such lots.
Sadly never did hear what the return was or receive any money.
The chap told me I was an idiot for trusting him and kept several thousand pounds of equipment, sabotaging most of what he did return to the chap I sent to collect.( Don't really trust myself in close proximity to him, came very close to stuffing him into a 20,000ml reaction vessel.LOL).
So never had any real luck with P,G,M's

 

[orvi]

Yep, interesting how this secrecy and practically divided monopoly evolved around PGMs. Why not the other metals.

That was why I invested so much time and effort to elaborate the PdPtRh "separation - recovery" method with acceptable losses. And failed miserably, to be honest. Then stuck with health issues, so I am out for several months and cannot perform experiments on PGMs. And I was relatively close to tuning the NH4Cl precipitation that way it do not drag too much Rh with it. That was the annoying step, so much Rh was trapped in the precipitates of ammonium platinate (nearly 40 % sometimes, from that 1-2% starting Rh content). Later steps were pretty much straightforward - cementing the PdRh remaining solution on zinc, boiling the precipitates with water to get rid of chlorides (practically) completely (AgNO3 test pass) and then digesting the cement with HNO3. Filter palladium nitrate and get enriched Rh cement fraction.

If I was ever to accomplish the recovery of more than 50% of the contained Rh to some enriched fraction, it will go straight here to the forum, for free and for anyone.