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.

 

[100tific]

Good morning, I am going to clarify all the issues that you mentioned to me, forgive me for not being so precise in my explanation or so exhaustive with my numbers.
Firstly, clarify that the values I mention are in parts per thousand. They are not exact values since X-ray fluorescence spectrometry gives approximate values, but I leave you a photo of the results before and after adding copper for inquartation.
Before,

weighing exactly 480.15g
After copper, (The operation consists of 480g x 254 grade of Ag = y x 100 new grade of Ag, y=1219.2g and 1219.2g - 480g =739.2g Cu must be added)

weighing exactly 1227.55 g
Ok, once this point has been clarified, I will tell you that, obviously later I would recover the gold. What I am trying is, in different alloys containing different proportions of precious metals, to be able to separate each one individually, and refine them to the maximum possible.
I started adding aqua regia because I read that if I applied only nitric to remove the silver, the platinum would also dissolve in the nitric acid, which would make its subsequent recovery difficult.
I don't have copper powder, so I try to avoid cementation, although I will end up buying it later to recover the stock pot. But I don't want cementation to become the usual technique, only using it when there is no other choice.
So, returning to the aqua regia, which is effectively green from copper and gold, I decided to first recover platinum. I don't know if the correct order would be gold first and then platinum, I could change it without a problem.

I want to know, do you who recover platinum, in alloys that contain a lot of silver, also do the inquartation with copper or how do you approach this problem? The nitric acid method is not very appropriate, which is why I had already mentioned that it dissolves part of the platinum. So, does copper negatively affect Pt recovery as well? Why did I get that green solid? what's that? Do you know the Jahn-Teller effect? could this be?
Maybe I used too much aqua regia, taking into account all the metals in the alloy and that each one reacts with different amounts of aqua regia, (for example copper needs more than gold), how could I estimate the minimum amount of aqua regia What should I use, so I have less time removing the nitrous compounds later? Does ammonium chloride react with dissolved copper? or with nitrous compounds?
These are all the questions that arise after this treatment.
Lastly, I would also like to clarify that yes, I am a woman. I don't know why this has caused such a stir. Women also do science, we also think, and we also love precious metals and their chemistry. I have been dedicating myself to this sector for 5 years, and I am very happy because I never stop learning and they never stop surprising me.
I would also like to say that I have read and studied Hoke's book, also a woman, and many other books before reaching this point.
Thank you very much colleagues, I love reading you and continuing to learn together. a hug.

 

[Yggdrasil]

Good morning, I am going to clarify all the issues that you mentioned to me, forgive me for not being so precise in my explanation or so exhaustive with my numbers.
Firstly, clarify that the values I mention are in parts per thousand. They are not exact values since X-ray fluorescence spectrometry gives approximate values, but I leave you a photo of the results before and after adding copper for inquartation.
Before,

weighing exactly 480.15g
After copper, (The operation consists of 480g x 254 grade of Ag = y x 100 new grade of Ag, y=1219.2g and 1219.2g - 480g =739.2g Cu must be added)

weighing exactly 1227.55 g
Ok, once this point has been clarified, I will tell you that, obviously later I would recover the gold. What I am trying is, in different alloys containing different proportions of precious metals, to be able to separate each one individually, and refine them to the maximum possible.
I started adding aqua regia because I read that if I applied only nitric to remove the silver, the platinum would also dissolve in the nitric acid, which would make its subsequent recovery difficult.
I don't have copper powder, so I try to avoid cementation, although I will end up buying it later to recover the stock pot. But I don't want cementation to become the usual technique, only using it when there is no other choice.
So, returning to the aqua regia, which is effectively green from copper and gold, I decided to first recover platinum. I don't know if the correct order would be gold first and then platinum, I could change it without a problem.

I want to know, do you who recover platinum, in alloys that contain a lot of silver, also do the inquartation with copper or how do you approach this problem? The nitric acid method is not very appropriate, which is why I had already mentioned that it dissolves part of the platinum. So, does copper negatively affect Pt recovery as well? Why did I get that green solid? what's that? Do you know the Jahn-Teller effect? could this be?
Maybe I used too much aqua regia, taking into account all the metals in the alloy and that each one reacts with different amounts of aqua regia, (for example copper needs more than gold), how could I estimate the minimum amount of aqua regia What should I use, so I have less time removing the nitrous compounds later? Does ammonium chloride react with dissolved copper? or with nitrous compounds?
These are all the questions that arise after this treatment.
Lastly, I would also like to clarify that yes, I am a woman. I don't know why this has caused such a stir. Women also do science, we also think, and we also love precious metals and their chemistry. I have been dedicating myself to this sector for 5 years, and I am very happy because I never stop learning and they never stop surprising me.
I would also like to say that I have read and studied Hoke's book, also a woman, and many other books before reaching this point.
Thank you very much colleagues, I love reading you and continuing to learn together. a hug.

I think the reference to beeing a woman only refers to that we don't have too many of you.
Science is science and has no gender.
Happy to have you with us

 

[nickvc]

The reason I suggested the nitric treatment is that it would remove the silver which been over 4 times the weight of PGMs would have also removed nearly all if not all of the PGMs , you can then create silver chloride which you could filter out and then cement the PGMs with copper leaving you a mix of platinum and palladium as metallics , rinse the recovered metallics in water and soak in nitric which will then remove the palladium leaving you with nearly pure platinum.
The gold would be easy to refine and recover using AR ,the silver chloride again easy to convert, the platinum is already fairly pure so the only value not recovered is the palladium which been such a small amount I’d simply again cement out and save the recovered metallics until I had enough to make the refining worth the effort.
To my mind this would produce the best outcome for your source material but I’m open to criticism and or other thoughts.

 

[Shark]

I don't know why this has caused such a stir.

There are other female members but only a very few that participate actively. Maybe you can start a trend by your participation.