Simple questions, looking for simple answers (or maybe not so simple).

[BAGross85]

If I cement out a solution of various rhodium, platinum, palladium, magnesium, zinc, and iron chlorides by using copper, I should in theory, drop out all metals below on the reactivity series (Pd, Pt, Rh)

After proper washing, and perhaps a round of redissolution/recementation, is it practical to melt those metals into a bead, and confirm with XRF analysis? Will Pd, Pt, and Rh melt together, and be verifiable to a semi-accurate scale with the XRF gun? Or will I need to further seperate them in order to melt them all together? I may have missed it in Hoke: I want to be able to melt a sample of all of them into a bead and have it scanned at the local jewelry shop, and I’m not sure if it will give an accurate depiction of the % contents. I’m aware that powder will not produce accurate results with XRF. I plan to use a wesgo crucible, OXY-propane, and borax flux.

Please show me grace here, I am a newbie with thousands of hours of research, and very little laboratory experience related to PGMs. Due to their hazardous nature, I want to fill my brain with information and carefully plan, prior to jumping in. I’ve been reading books, forum posts, and articles for 6 years and haven’t even touched the material in this timeframe.

Edit to correct auto-correct

 

[Yggdrasil]

If I cement out a solution of various rhodium, platinum, palladium, magnesium, zinc, and iron chlorides by using copper, I should in theory, drop out all metals below on the reactivity series (Pd, Pt, Rh)

After proper washing, and perhaps a round of redissolution/recementation, is it practical to melt those metals into a bead, and confirm with XRF analysis? Will Pd, Pt, and Rh melt together, and be verifiable to a semi-accurate scale with the XRF gun? Or will I need to further seperate them in order to melt them all together? I may have missed it in Hoke: I want to be able to melt a sample of all of them into a bead and have it scanned at the local jewelry shop, and I’m not sure if it will give an accurate depiction of the % contents. I’m aware that powder will not produce accurate results with XRF. I plan to use a wesgo crucible, OXY-propane, and borax flux.

Please show me grace here, I am a newbie with thousands of hours of research, and very little laboratory experience related to PGMs. Due to their hazardous nature, I want to fill my brain with information and carefully plan, prior to jumping in. I’ve been reading books, forum posts, and articles for 6 years and haven’t even touched the material in this timeframe.

Edit to correct auto-correct

They will alloy quite fine, but there will be copper as well and you need some serious temperatures to manage it.

 

[BAGross85]

They will alloy quite fine, but there will be copper as well and you need some serious temperatures to manage it.

I planned to use an OXY/propane torch, I think that will work for the small quantity I’m planning to melt.

My other melting method I thought of was a large concave mirror: I have a 10-ft satellite that I can coat with mylar that *should reach the necessary temperatures.

 

[4metals]

The easiest way to re-dissolve cemented metals to refine them to higher grade metal is to leave them in the form they are in when cemented. I have experienced that while XRF is not particularly accurate on low grade sweeps, if it is used on concentrated metal powder it can be quite accurate.

I would try to dry it on a filter paper and have it shot with an XRF just to see what it gives you as a result. This is usually true when you have a respectable pile of cemented metal, a few grams total will likely not be as accurate.

If you do this, please let us know your results.

 

[BAGross85]

They will alloy quite fine, but there will be copper as well and you need some serious temperatures to manage it.

Also, I’m debating on which will produce a cleaner cementation/larger overall recovery.

Solid pure copper,
Solid pure copper turnings,
Solid pure copper powder.

 

[BAGross85]

The easiest way to re-dissolve cemented metals to refine them to higher grade metal is to leave them in the form they are in when cemented. I have experienced that while XRF is not particularly accurate on low grade sweeps, if it is used on concentrated metal powder it can be quite accurate.

I would try to dry it on a filter paper and have it shot with an XRF just to see what it gives you as a result. This is usually true when you have a respectable pile of cemented metal, a few grams total will likely not be as accurate.

If you do this, please let us know your results.

It will be some time, but happily. Maybe I will do both, with the melt as the independent variable to compare XRF analysis accuracy. I just don’t know that I’ll have enough

 

[4metals]

Also, I’m debating on which will produce a cleaner cementation/larger overall recovery.

Solid pure copper,
Solid pure copper turnings,
Solid pure copper powder.

The reason cementation can produce dropped metals which are not as pure as you expect is unreacted copper mixed in the dropped powders. This is why I would not use copper turnings because all that does not contact the values in solution will remain metallic copper and be melted with your target metals.

I would be using solid pure copper slab suspended in a circulating solution. Then to finish it I would sparingly use copper powder. Added slowly because once it falls to the bottom it adds to the copper content rather than the purity.

 

[anachronism]

If I cement out a solution of various rhodium, platinum, palladium, magnesium, zinc, and iron chlorides by using copper, I should in theory, drop out all metals below on the reactivity series (Pd, Pt, Rh)

The short answer is yes you should. I was going to write a longer answer but then I read 4metals post above mine and thought that it really says it all.

The only thing I would add is that if you keep the solution mobile using stirring then the copper powder has more chance to work fully. Used as a last "catch" option, if you are willing to accept that the last bits you get are by definition impure then you can treat it again or add to your next dissolve.

 

[4metals]

The only thing I would add is that if you keep the solution mobile using stirring then the copper powder has more chance to work fully.

I have set refiners up to do this both ways, first using a hanging slab in a bubbler setup and using the powders for the last cleanup. These were solutions from Platinum stone removal and the concentration was in the 2 oz per liter range as Platinum. The reason I do it this way is because I don't like to expose workers to the Platinum salts by going the ammonium chloride route. The cementing route produces metal which is melted and sold off to a refiner anyway.

Recently I have used an angled slow rotating 5 gallon bucket which can be rotated quite slow. (0 -110 rpm with an air powered motor with a speed control) This is effective because it even gets the copper (or zinc) on the bottom moving and exposing new metal to react with the Platinum in solution.

bucket mixer

 

[Shark]

I may need to sell one of those mixers one day. I had no idea they had got that expensive. I just picked up a motor for it and need to get it mounted.

 

[4metals]

They are pretty pricey. I like the air operated model because it allows complete speed control from zero to full speed.

 

[BAGross85]

The easiest way to re-dissolve cemented metals to refine them to higher grade metal is to leave them in the form they are in when cemented. I have experienced that while XRF is not particularly accurate on low grade sweeps, if it is used on concentrated metal powder it can be quite accurate.

I would try to dry it on a filter paper and have it shot with an XRF just to see what it gives you as a result. This is usually true when you have a respectable pile of cemented metal, a few grams total will likely not be as accurate.

If you do this, please let us know your results.

So you would say that the powder recovered by cementation with Cu, would be acceptable to scan with XRF?

 

[4metals]

If it is high purity and a reasonable percentage yes. But you need more than a few grams.

 

[kurtak]

The easiest way to re-dissolve cemented metals to refine them to higher grade metal is to leave them in the form they are in when cemented. I have experienced that while XRF is not particularly accurate on low grade sweeps, if it is used on concentrated metal powder it can be quite accurate.

I would try to dry it on a filter paper and have it shot with an XRF just to see what it gives you as a result. This is usually true when you have a respectable pile of cemented metal, a few grams total will likely not be as accurate.

If you do this, please let us know your results.

In my experience shooting "mixed metal" powders (Pt Pd Rh) with an XRF is difficult in providing you with a true &/or accurate reading of the percentages of each metal in the powders

When I was leaching CATs I used zinc to cement the Pt Pd Rh out of each batch of leach solution (so the cemented Pt Pd Rh was all from the same leach solution)

After filtering & drying the mixed metals the powders were put in a plastic baggie in order to take several readings of the powders with an XRF --- depending on the batch I was shooting anywhere from 3/4 ozt. to 2 ozt. powders taking 5 - 6 readings per batch of cemented powders

I don't think I ever got two readings the same on any one baggie --- at best - you "might" get readings close enough (percent wise) to get "somewhat" of an "average" of each metal in the powders but more often the multiple readings of the same batch of powders would very so much that it was next to impossible to even "average" the percentage of each metal in the mixed metal powders

You would think that mixed metal powders from the same batch would be somewhat homogonies & though that can sometimes be true you can't count on it when XRFing mixed metal powders

At least that was my experience with XRFing mixed (PGM) metal powders

Kurt

 

[kurtak]

As a side note to my last post it seemed like where the multiple readings of the mixed powders would come back relatively close percentage wise for each metal was when one of the metals (usually the Pd - sometimes the Pt) was HIGH

Example; - if the Pd was up in the 70% - 80% the multiple readings of each metal would come back within a percent or 2 of the high reading metal - in other words in the multiple readings it might say 69% pd - 70% Pd or 71% - & thereby attributing "closer" values (percent wise) on the Pt & Rh as well

If one of the metals was not dominate (high in percentage by a lot) the multiple readings for each metal could very by 5 - 8%

Kurt

 

[4metals]

At least that was my experience with XRFing mixed (PGM) metal powders

My experience is pretty much the same, it is not a result to replace the accuracy of a true fire assay with an instrument finish but it is a reasonable source of guidance for someone who isn't likely willing to spend hundreds of dollars on the complicated assay.

I guess it is a better description to call it "close enough for government work".

 

[4metals]

After filtering & drying the mixed metals the powders were put in a plastic baggie in order to take several readings of the powders with an XRF --- depending on the batch I was shooting anywhere from 3/4 ozt. to 2 ozt. powders taking 5 - 6 readings per batch of cemented powders

Was the zinc dissolved away before you took the readings or were these results PM plus zinc?

 

[kurtak]

Was the zinc dissolved away before you took the readings or were these results PM plus zinc?

No zinc - dilute cold HCl washes done to remove any trace zinc from cementing

However what I found interesting was that "some" CATs had "small" amounts of copper in them - there was one brand/type of CAT that was actually quite high in copper

And for what it is worth each batch of CATs was leached based on the same band/type of CATs going into the batch - never a bunch of different brands/ types of CATs thrown in a batch - which is why I know there was one particular brand/type CAT that was quite high in copper

Kurt

 

[4metals]

No zinc - dilute cold HCl washes done to remove any trace zinc from cementing

I never liked running converters in acid. The substrate of the cats always retained values, or put another way never leached completely. There was value in the leached converter dust but not much above the processing charges at the smelters. But this was 30 years ago and metal prices have risen considerably.

 

[kurtak]

I never liked running converters in acid. The substrate of the cats always retained values, or put another way never leached completely.

Per the bold print - you are absolutely right - other then "maybe" leaching a very small amount (like 50 - 100 grams) of CAT material you will NEVER get all of the PGMs leached out of the ceramic substrate of catalytic converters - this is especially true of the Rh

The larger you go in batch size the more difficult it becomes for the leach to leach out the PGM from the ceramic substrate & that is especially true if you crush the CAT comb to powder rather then leaching it as a whole CAT comb

That is because with crushed CAT comb -----------

1) you have to keep the crushed substrate stirred up in order for the leach to effectively get to the PGMs in the ceramic to dissolve them - and ------------

2) it is next to impossible - if not impossible - to wash/filter all of the leach out of the ultra fine ceramic mud created in the leach process --- the larger the batch the more difficult it is to get all the leach washed/filtered out of the MUD

As an example; - if you put 50 - 100 of crushed CAT comb in a beaker on a stir hot plate you can keep the very small amount of ceramic stirred up enough to effectively leach the PGMs & with that very small amount of ceramic mud you can effectively wash/filter most if not all the leach out with a vacuum flask set up

These are the university "experiment" papers BAGross85 has read & referred to in this thread ------------

https://goldrefiningforum.com/threads/the-platinumill-exposed-and-on-trial.1316/page-28

I have also read some of these university very small experiment papers & they all sound good on the very small scale experiment level to write a paper & pass the class for their class grade

The problem is these "experiments" simply DO NOT work when you scale them up - not even to doing just one single CAT comb which is about (plus/minus) 1 kilo of crushed CAT comb

With a kilo of crushed ceramic you are going to find it next to impossible - if not impossible to keep ALL of the ceramic stirred up enough to get full & effective leaching of the PGMs - even with a 10 or 20 liter reaction flask with overhead stirrer & then I can assure you that with 1 kilo of ceramic mud it is just not next to impossible but in fact impossible to get all the leach washed/filtered out of that MUD - even with vacuum filtering

You are better served to leach CATs as whole CAT combs but even then you need to come up with away to keep the leach solution circulating though the VERY small veins that make up the comb & even then you simply will NOT get all the PGMs leached out --- you will leave MOST of the Rh behind - get at best only 50 - 60% of the Pt & about 80 - 90 % of the Pd

There is a reason why the BIG BOYS do NOT leach CATs but smelt them - but even then it will cost more to smelt then what you can recover unless you go BIG --- VERY BIG --- like at the very least #100 crucible/furnace

For what it is worth - &/or ask me how I know

Kurt