Problems in platinum recovery

[100tific]

Hi guys,
After studying a lot I decided to start recovering platinum from an alloy. I tell you my story.
It had an initial alloy weight of 480g. This had the following proportions: 500 Au, 36 Pt, 250 Ag, 184 Cu, 6 Pd and a little Zn and Ni.
Since the amount of silver was high, I decided to add copper to lower the proportion to 10%. I added 739.2g of Cu and made shot from this.
I was left with a weight of 1227g of alloy with proportions:
Cu:684
Au: 189.63
Pt:17.25
Ag:91.58
and some Zn, Pd and Ni.
Now the silver ratio was low enough to be able to attack directly with AR and heat.
Since there was a lot of it, it took too long to react, I had to leave and the reaction was not over. So the next day I filtered it and added fresh aqua regia to continue reacting the grit that remained undissolved.
I watched as a green scab formed, the likes of which I had never seen before. I thought that since it had so much copper, it was possibly CuCl2, could anyone confirm? attached photo

I continued filtering the solution to remove any silver chlorides that might be present and leaving the solution clean.

After this point, I added 12.5g of ammonium chloride to my solution. and nothing happened.
Then I thought I had forgotten the step of removing the HNO3, I heated for several days to obtain the syrup, I also added sulfamic acid, and I still never managed to obtain the orange ammonium hexachloroplatinate powder.
I wanted to ask if you know if a large amount of copper can negatively affect the recovery of platinum, and if so, how could it act when the amount of silver is greater than 12%?
I hope you can help me, I don't know why sometimes platinum recoveries don't go well. I would like to understand what is happening.
Thank you very much and best regards.

 

[nickvc]

I’m no expert on PGM refining so I could well be wrong but with the percentages of metals you ended up with I would have been tempted to treat it with nitric first as the silver content would have been high enough to allow the PGMs to dissolve, then convert the silver to chloride and filter off the solution and then cement the PGMs out with copper for further refining, the gold would have been left ready for AR and easily refined.
Perhaps others may have better ideas but I gather PGMs are better refined from concentrated solutions.

 

[Martijn]

This had the following proportions: 500 Au, 36 Pt, 250 Ag, 184 Cu, 6 Pd and a little Zn and Ni.

Are these and the other numbers in ppm? If so, then I don't consider an alloy of 0.05% 0.025% silver as a high silver content.
0.05% 0.025% of 480 grams equals a total amount of 0.25 0,125 grams of silver.
Then there is 36 ppm Pt of 480 grams = a total amount of 0.017 grams of Pt.
Is that even visible with the naked eye?

I wanted to ask if you know if a large amount of copper can negatively affect the recovery of platinum, and if so, how could it act when the amount of silver is greater than 12%?

Again, I doubt you have 12.5 % Ag..

Edited to correct: I calculated with the Au content of 500 ppm in stead of the Ag content of 250ppm.

Martijn.

 

[Martijn]

Another reason I suspect this is the amount of AgCl you have in the flask. That does not look like 60 grams of silver in the form of AgCl, more like one gram, maybe.

 

[Yggdrasil]

Hi guys,
After studying a lot I decided to start recovering platinum from an alloy. I tell you my story.
It had an initial alloy weight of 480g. This had the following proportions: 500 Au, 36 Pt, 250 Ag, 184 Cu, 6 Pd and a little Zn and Ni.
Since the amount of silver was high, I decided to add copper to lower the proportion to 10%. I added 739.2g of Cu and made shot from this.
I was left with a weight of 1227g of alloy with proportions:
Cu:684
Au: 189.63
Pt:17.25
Ag:91.58
and some Zn, Pd and Ni.
Now the silver ratio was low enough to be able to attack directly with AR and heat.
Since there was a lot of it, it took too long to react, I had to leave and the reaction was not over. So the next day I filtered it and added fresh aqua regia to continue reacting the grit that remained undissolved.
I watched as a green scab formed, the likes of which I had never seen before. I thought that since it had so much copper, it was possibly CuCl2, could anyone confirm? attached photo

I continued filtering the solution to remove any silver chlorides that might be present and leaving the solution clean.

After this point, I added 12.5g of ammonium chloride to my solution. and nothing happened.
Then I thought I had forgotten the step of removing the HNO3, I heated for several days to obtain the syrup, I also added sulfamic acid, and I still never managed to obtain the orange ammonium hexachloroplatinate powder.
I wanted to ask if you know if a large amount of copper can negatively affect the recovery of platinum, and if so, how could it act when the amount of silver is greater than 12%?
I hope you can help me, I don't know why sometimes platinum recoveries don't go well. I would like to understand what is happening.
Thank you very much and best regards.

As Martijn ask is this per million or per mille?

I would say that after dissolving the alloy my best cause of action would be to drop the Gold, then drop the Silver as Chloride and then Cement the Pt on Copper.
The Silver Chloride would need to be washed thorougly before converting to Silver.

 

[FrugalRefiner]

Hi guys,
After studying a lot I decided to start recovering platinum from an alloy. I tell you my story.
It had an initial alloy weight of 480g. This had the following proportions: 500 Au, 36 Pt, 250 Ag, 184 Cu, 6 Pd and a little Zn and Ni.

They're proportions. So, like percentages but with an extra zero. 500 Au would be 50%, 36 Pt would be 3.6%, 250 Ag would be 25%, etc.

Dave

 

[nickvc]

Are these and the other numbers in ppm? If so, then I don't consider an alloy of 0.05% 0.025% silver as a high silver content.
0.05% 0.025% of 480 grams equals a total amount of 0.25 0,125 grams of silver.
Then there is 36 ppm Pt of 480 grams = a total amount of 0.017 grams of Pt.
Is that even visible with the naked eye?


Again, I doubt you have 12.5 % Ag..

Edited to correct: I calculated with the Au content of 500 ppm in stead of the Ag content of 250ppm.

Martijn.

Martijn I assumed the first figures given were percentages of metals , which apart from the copper and silver , appears to bear true in the list below.

 

[4metals]

Is there a reason you went for the Platinum before the Gold? Typically for this type alloy, I would use aqua regia as you did after lowering the Silver percentage and I would have dropped the Gold, after removing the excess nitric, using ferrous sulfate. After the gold is dropped, the solution is in a state where the Platinum are all at a valence state where the Platinum can be recovered using ammonium chloride.

 

[Martijn]

They're proportions. So, like percentages but with an extra zero. 500 Au would be 50%, 36 Pt would be 3.6%, 250 Ag would be 25%, etc.

Dave

Then I guess an alloy of 25% silver will not dissolve in AR!
Something does not add up here.
I still suspect an XRF reading in ppm. Or he has miracle AR?
Does that layer of AgCl layer correspond with 60 grams of silver?

 

[Martijn]

And he calculates a proportion of 250 or 25% Ag from 480 grams in total as 12.5 %

I was left with a weight of 1227g of alloy with proportions:
Cu:684
Au: 189.63
Pt:17.25
Ag:91.58
and some Zn, Pd and Ni.

12.5% of 480 grams is 60 grams, not 91.58.
12.5% of 1227 grams is 153 grams.
and if he went for 10% ag that would be 127 grams Ag.

calculus error?

 

[Martijn]

i also did not read anything about precipitating the gold from his AR, so where is that 240 grams of gold chloride color? no yellow at all.

 

[Yggdrasil]

And he calculates a proportion of 250 or 25% Ag from 480 grams in total as 12.5 %

12.5% of 480 grams is 60 grams, not 91.58.
12.5% of 1227 grams is 153 grams.
and if he went for 10% ag that would be 127 grams Ag.

calculus error?

He added Copper for inquarting to a total of 1227g.
But the math still do not add up I think.
I'll check a bit more.

 

[FrugalRefiner]

Again, 100tific is using proportions, in this case parts per thousand.

Original alloy was:
500 Au
36 Pt
250 Ag
184 Cu
6 Pd
and a little Zn and Ni.
They add up to 976 parts per thousand plus a little Zn and Ni.

After adding 739.2g of copper, the weight should have been 1,219.2 grams, not 1,227g. Not sure where the extra 8 grams came from, but
the proportions are:
Cu:684
Au: 189.63
Pt:17.25
Ag:91.58
and some Zn, Pd and Ni.
They add up to 982.46 parts per thousand.

There may be some minor math errors, but they're still proportions. And based on 100tific's avatar, I'm guessing she is a lady, not a he.

Considering the high proportion of copper to gold, I would expect the solution to be that deep green color. Look at the filter paper in the filter. I see the yellow there.

Dave

 

[Yggdrasil]

Frugalrefiner did the math.
Thanks!

 

[Yggdrasil]

Hi guys,
After studying a lot I decided to start recovering platinum from an alloy. I tell you my story.
It had an initial alloy weight of 480g. This had the following proportions: 500 Au, 36 Pt, 250 Ag, 184 Cu, 6 Pd and a little Zn and Ni.
Since the amount of silver was high, I decided to add copper to lower the proportion to 10%. I added 739.2g of Cu and made shot from this.
I was left with a weight of 1227g of alloy with proportions:
Cu:684
Au: 189.63
Pt:17.25
Ag:91.58
and some Zn, Pd and Ni.
Now the silver ratio was low enough to be able to attack directly with AR and heat.
Since there was a lot of it, it took too long to react, I had to leave and the reaction was not over. So the next day I filtered it and added fresh aqua regia to continue reacting the grit that remained undissolved.
I watched as a green scab formed, the likes of which I had never seen before. I thought that since it had so much copper, it was possibly CuCl2, could anyone confirm? attached photo

I continued filtering the solution to remove any silver chlorides that might be present and leaving the solution clean.

After this point, I added 12.5g of ammonium chloride to my solution. and nothing happened.
Then I thought I had forgotten the step of removing the HNO3, I heated for several days to obtain the syrup, I also added sulfamic acid, and I still never managed to obtain the orange ammonium hexachloroplatinate powder.
I wanted to ask if you know if a large amount of copper can negatively affect the recovery of platinum, and if so, how could it act when the amount of silver is greater than 12%?
I hope you can help me, I don't know why sometimes platinum recoveries don't go well. I would like to understand what is happening.
Thank you very much and best regards.

You need the Pt ions to be in its highest valency to properly react with the Ammonium Chloride.
Adding a bit of Sodium Chlorate might fix this.
Have you read Hokes book on this?
And since you are new to this I'd recommend dropping this part and go directly to cementing on Copper.
PGM salts are exeedingly toxic so most of us go the extra mile to avoid having them in solution.

 

[Shark]

There may be some minor math errors, but they're still proportions. And based on 100tific's avatar, I'm guessing she is a lady, not a he.

And based on other posts it appears she is fairly knowledgeable in PGMs as well. Myself, seeing more women become involved in the forum would be nice.