Cement

[g_axelsson]

To g_axelsson,, I am glad you're on the forum. Again, I understand what you're saying, but what I'm not understanding is that if I process my stock pot, there is the possibility that PGM's could be in my solution, even after exhausting all the acids (copper won't dissolve anything) but still have copper left in the stock pot?

To both of you, .. I'll go for just the gold and silver FIRST. I did however recover the copper too, but never tested any of the solution to see if there were any PGM's still present.

I love you all here. I'm learning and keeping all of it close to my heart forever.

scrapparts

What I mean is that any pgm:s that you have cemented out in your stock pot could go through the process of gold recovery but in the end just being ignored and put back in the stock pot after the gold is extracted. It will build up over time.

This is just an example of how you can treat the stock pot. I might have left out some clues or procedures so don't use it as a blue print for stock pot treatment.
- Filter or decant the stock pot to separate liquid from cemented metals in the sludge.
- The liquid (old stock pot) should be tested and if barren of values it goes off to the waste treatment.
- The solids contains some gold, silver chloride, pgm:s but also other crap from the refining process.
- Treat the slime with aqua regia, now pgm:s and gold should be in solution. Silver chloride in solids.
- Remove solids and treat separately, for example recover silver.
- Denox and drop the gold from the liquid. Wash and melt.
- The liquid after recovering gold now contains any pgm:s from the old stock pot. his can now be added to a new stock pot with more copper, the pgm:s should cement out on the copper and any gold still in suspension sinks to the bottom.

If you have small amounts of pgm in the waste liquid from the old stock pot then testing with stannous will give you a hint if it is a lot or just traces.
If you cement the copper on iron then any pgm:s should follow the copper and you can recover it from the copper in the future, for example in a copper cell.

I don't know how powerful copper (II) chloride is but I know it can dissolve palladium. Iron chloride seems to be weaker so it should have harder to dissolve palladium, if even possible. At least with a lot of copper powder around the palladium is easily cemented out and embedded in the copper powder. So when you recover copper from your waste it also extracts any gold or pgm:s that you missed.

I'm collecting any copper I'm cementing out in my waste stream and I'm going to do a copper cell some day to see if I left any values behind... and because it's a cool thing to do.

Chemistry is messy and no process is ever 100%. There is always losses along the way. By designing your refining and waste stream properly you can get back some of the losses you made during refining. The question to ask, is it worth it? That answer is quite different if you are a hobby refiner or a professional refinery with staff on salary.

I hope this answers your question.

Göran

 

[Geo]

Geo, you're full of knowledge I've never heard of before. Great new things to consider thanks to what you've pointed out!
E.g. the boiling of floating powder in H2SO4 , great tip. You should write a book! (or have you already?)

Back on topic: FeCl also is a powerfull etchant, can I expect that any of my 0,001ppm traces of cemented Pd from the iron displacement reaction in the waste treatment dissoved back into solution and ended up in the hydroxides? Or is FeCl not able to dissolve Pd cement?
I've searched the internet and did not find an answer.

If i'm not mistaken, FeCl can be formed in the waste treatment by adding a piece of iron to CuCl and such?
Where will the Pd end up if no special precautions are taken?
Not in the stockpot I presume, if there is Cu2Cl present, which usually is?
Again purely theoretical, I am not to worried about losing 0,001ppm :wink:
Martijn.

FeCl3 will dissolve and hold Pd in solution. The composition of the solution is not as important as PH and ORP which is closely related. If the PH value is low enough, it will dissolve finely divided Pd powder. Pd solids would be a little more difficult or take a longer time to dissolve a certain weight of metal but if left in solution long enough, it will most surely dissolve it.

No, sorry. No book, yet.

 

[Geo]

Breaking a colloid is actually the one thing that I can credit Dr Poe with. If you can believe that. The one time that we communicated and he didn't act like a pompous ass was about breaking the colloidal bond and clearing solutions.

 

[scrapparts]

Sorry all,

But I meant to ask this question.....

After I gather my sludge from my stock pot, and then move the solution to drop the copper, after that is done, I should return that solution back to the stock pot after testing solution? What if the solution is negative on testing? Do I neutralize the solution and dispose of properly?

This is some cool stuff here. Not talking computers or politics, talking about "How-To-Refine".

scrapparts

 

[g_axelsson]

Sorry all,

But I meant to ask this question.....

After I gather my sludge from my stock pot, and then move the solution to drop the copper, after that is done, I should return that solution back to the stock pot after testing solution? What if the solution is negative on testing? Do I neutralize the solution and dispose of properly?

This is some cool stuff here. Not talking computers or politics, talking about "How-To-Refine".

scrapparts

No, after the copper is cemented there are no reason to believe that there are any precious metals dissolved in the liquid.

When you cement the copper you also cement any traces of precious metals at the same time, most of it will be embedded in the copper grains.

Göran

 

[Martijn]

IF I read Geo's answers correct, when having HCL in your stockpot solution, the stockpot black will not contain any/much Pd, because of Cu2Cl formation, most of it will be in solution, since all blacks in there are cemented blacks and very fine.

Advancing to the iron pot, the iron will cement out on the copper, and with the air bubbler eventually create FeCl3. This iron chloride will also dissolve Pd. So again no, or very little cemented Pd to be expected in your cemented copper, nickel, and other less reactive base metals below iron in the reactivity series. It will still be in solution.

So always test after the Stockpot to make sure no Pd is remains in solution. If you expect Pd in your waste solutions. An AP solution will also have Pd in solution if any was present and left in there long enough (from MLCC's e.g.)
Test before and after cementing on copper.
And like with free nitric in AR, Pd would redissolve in AP, so the test result may disappear after some time.
I think the old stockpot solution needs to be diluted a bit for testing with stannous? (Only a bit, not the entire bucket.)
This test result can also give you an indication of how much it needs to be diluted to keep cemented Pd out of solution.
Martijn.

 

[g_axelsson]

FeCl₃ is used as a circuit board etchant, so it will dissolve copper as well and preferentially.

If you run out of iron in the copper cementing, the iron chloride can dissolve both copper and palladium, but copper more easily which will add copper chloride to the mix too.

As always in chemistry, yes, you will have some copper and palladium in the liquids after cementing copper on iron, but in very low concentration. Just as you have some gold still in the solids and filters when refining gold. It's all a matter of knowing when you got enough metal out and it doesn't pay off to hunt the last bit.

When you run the leftovers from a process a second time with fresh acids you can actually find out if there is enough gold left or if your first extraction was good enough. Often the second extraction is so low in gold that the only thing you get out of it is ease of mind.

Göran

 

[scrapparts]

All of this is making more sense. I'm going to take notes and put some of the methods to work immediately. After all the sludge I have, I'll be dealing with my waste filters that is almost 5-gal bucket full.

Thanks again for all the help and information to expand the understandings of why certain things must/should be done.

It's starting to warm up here, so hopefully tomorrow I can get to my stock pot sludge and start processing that..

scrapparts

 

[Geo]

If you are treating your waste responsibly, the last bit of Pd in your waste stream will report in the oxides, hydroxides or carbonates, which ever you use to neutralize the remaining acid. It doesn't take much to realize that even this can be captured and reclaimed in enough quantity to make it worth the effort. If prices keep on with the upper trend, what is trivial now may not be in the future. Rhodium was such a low value not long ago, that it was plated over silver. I bet at $21,000 per ounce, no one is plating it over silver today.

 

[kurtak]

Geo

There should be NO reason why you can't cement Pd (&/or other PGMs) from acidic solutions & get ALL the Pd/PGMs to cement out of the solutions (at least concerning cementing them from nitric or AR solutions)

Palladium, when finely divided, will dissolve in HCl alone or nitric acid alone.

That is true

It is difficult to cement out of solution because of it's tendency to redissolve in acidic solutions.

That should be true ONLY as long as there is "free" acid available to dissolve metal

If there is free acid in the solution - then yes - when you put the copper in - the copper will start to cement the metals below it (in the reactive series) but the free acid will re-dissolve the metals cementing out (whether it is gold, silver or PGMs) as well as dissolving the copper

This is a "redox" reaction which is a reaction wherein reduction & oxidation are taking place at the same time

So the Pd (or other PMs) are being reduced by the copper (being cemented out) - BUT - at the same time is being oxidized (re-dissolving) as a result of the "free" acid

The reactive series tells us not only how reactive acid is to different metals - but also tells us that the acid has a "preference" to dissolve the more reactive metals over that of the less reactive metals

so - because the copper is more reactive then the PMs it "will" dissolve at a faster rate which means eventually the free acid will be used up (completely) by the copper

In other words - the acid is is now "pregnant" with metal to the point the acid can no longer dissolve MORE metal

At the point where the acid is pregnant & can no longer dissolve more metal is when actual cementing takes place (the less reactive metal starts to drop out & STAY dropped out)

That's because though the acid can no longer dissolve more metal - the acid still has the preference to dissolve the copper over that of the less reactive metal (in this case the Pd) - so the acid does just that --- it continues to work at dissolving copper - but the acid is now to weak to any longer dissolve the Pd - so the solution has NO choice but to drop the Pd out - & it will continue to do so until the acid is "loaded" with copper - & at the point of being load with copper ALL the Pd (&/or any other less reactive metal) should be cemented out

The bottom line here is that there should be NO reason why you can't cement ALL the Pd from an acidic solution

However - it is true that cementing Pd (&/or PGMs) is "more" difficult then cementing gold or silver --- but that difficulty is not for the reasons you posted

You posted

I have often fielded the complaint from people saying that after cementing with copper, the solution still tests positive for Pd. The Pd will redissolve about as fast as it cements from solution.

Back in 2014 I was having the same problems (as I suspect you & others are having) with cementing Pd with copper

I posted about this problem in this thread

:arrow: Fuzz Button Interconnects, need some advice

Thanks to 4metals --- HE resolved the problems I was having with cementing Pd (so the credit goes to 4metals - not me) & after this full discussion with 4metals I have never again had a problem cementing Pd (&/or PGMs) & getting it ALL to come down

To summarize that discussion

The problem --- unlike cementing gold or silver which has a tendency to fall off the copper - thereby allowing the solution to stay exposed to the copper until all the gold or silver comes down --- PGMs tend to make a "tight" bond on the surface of the copper (actually "plate" to the surface) --- & this tight bond will happen very quickly

once the Pd (or PGMs) plate (in a tight bond) to the copper it will shut the cementing down because the solution can no longer make contact with the copper for the cementing to continue - even if you have free acid in the solution

to prevent that problem --- you need agitation of the solution - & - that agitation NEEDS to be VERY aggressive so that as the PGMs cement out they don't have time to bond to the copper

Therefore you need to start the agitation "before" putting the copper in or the bonding will happen as soon as you put the copper in - shutting the cementing process down before it even gets started

If the agitation is not aggressive enough it may well allow cementing for a while - but without enough agitation some bonding can start - which then limits exposed copper - which then allows more bonding to take place & eventually the copper will become fully plated with PGMs & likely shut the cementing down before all the PGMs are cemented out

So - you NEED to start the agitation before putting the copper in & the agitation NEEDS to be aggressive

Also - LOTS of copper surface area helps - the more copper surface area the better --- lots of copper surface area allows more copper to go into solution faster thereby pushing out the PGMs faster & coupled together with the agitation prevents the PGMs from having time to bond to the copper - provided the agitation is aggressive around all surfaces of the copper

If you read the link where 4metals got me pointed in the right direction for cementing PGMs - along with what I posted here - there is absolutely no reason why anyone should have a problem with cementing PGMs from acidic solutions & get it all to come down - & it should come down at least at 95% or better with the 5% (or less) being copper

Kurt

 

[kurtak]

I have often fielded the complaint from people saying that after cementing with copper, the solution still tests positive for Pd. The Pd will redissolve about as fast as it cements from solution.

Geo

As a follow up to my post yesterday concerning the above quote

Are they sure what they are seeing is in fact positive for Pd - &/or are they doing a stannous "only" test

I ask because there is such a thing as a Pd "false positive" that will show up with stannous

This is usually the result of an Fe/Ni alloy in solution which will show up as a "light" lime green instead of the deeper green of Pd

The Pd false positive looks like this

:arrow: Here is one for the experts here

A stannous test for Pd should always be followed up with a DMG test to in fact confirm that the stannous test is in fact Pd

Just like to much SMB can result in a false positive - there are a number of base metals in solution(s) that can produce false positives with stannous

Molybdenum (from moly/steel alloys) is another false positive that will show up with stannous --- it will fool you to think there is Pt in solution

The false positive for Pt looks like this

:arrow: Stannous Test Result, Platinum ???

So again - if you "suspect" Pt from a stannous test - but then can't get any Pt to cement out with copper it is likely molybdenum

You can (should) test further to confirm

:arrow: Stannous Test Result, Platinum ???

The point here being that you can in fact get a number of false positives with stannous & unless you do further testing to confirm the "suspected" stannous test you can end up chasing your tail trying to recover a metal that actually is not there

If a stannous test is telling you that you have PGMs in solution (or at least suspect PGMs) but are unable to cement then out of solution - then more likely then not one of two things are going on

1) your putting the copper in with out any agitation - &/or not enough agitation

2) you stannous test is (possibly) a false positive - so further testing should be done to confirm that the stannous test is in fact positive & not a false positive

Kurt

 

[kurtak]

Some other false positives you can get with a stannous test

selenium = red color result (so can fool you to thinking PGMs are in solution)

tellurium = black color result (so can fool you to think gold or PGMs are in solution)

mercury = grey color result (so can fool you to think silver is in solution)

Kurt

 

[Geo]

Most people that are asking me questions are beginners or have only worked with one metal for a long time and have decided to try something new. A couple of years ago I was posting that CuCl2 was a good way to concentrate Pd from electronics. That's because I process a lot of high grade boards whole in CuCl2 and then sort out the mess once everything is stripped. I've done it so long that I've experienced about everything that can happen in the process and have learned how to overcome it. It's not for a beginner or novice but it doesn't stop people from trying, I have about three hundred gallons of of CuCl2 stored that has varying amounts of Pd according to assay on recovered metals. With The price of Pd as it is, it is attractive to recover any amount from solutions like this. As I've demonstrated that the recovery can happen, but it can be difficult, in the least, to recover the metal without destroying the solution in the process. Cementing on copper is not feasible in those amounts because, as you said, copper tends to passivate if the PH is too low. To cement using copper effectively, I would need to dilute the solution by 2 or 3 times with water or adjust the PH using a base. I hate using sodium hydroxide because the cemented metal tends to be light and fluffy and stays suspended and needs to be filtered which adds extra steps. Other bases have there own problems as well. Copper carbonate tends to follow Pd into the melt. You can't remove the carbonate using acids without the possibility of redissolving the cemented Pd. It's a big prize if I can figure out how to recover the Pd without destroying the solution because it's my stock of pregnant CuCl2. I process whole boards in 30 gallon drums, 6 drums at a time.

 

[kurtak]

Cementing on copper is not feasible in those amounts because, as you said, copper tends to passivate if the PH is too low.

per the underlined - although Ph plays "somewhat" of a role concerning passivation (the Pd bonding to the copper) that passivation is easy to overcome no matter how low the Ph is (&/or for that matter how concentrated the acid in the solution is) in other words you can do it - without worry of passivation - from a straight up concentrated AR as long as you follow the three rules that prevent the Pd from bonding to the copper

1) Aggressive agitation of the solution

2) copper surface area - more is better - just be sure you don't put so much that it interferes with the agitation

3) DO NOT put the copper in until AFTER the agitation is started

Example; - you can lets say do a batch of white gold or dental gold (which will have PGMs) - dissolve it in AR - drop your gold - pour off the "concentrated" AR & cement that to recover the PGM with out any issues - as long as you follow the three rules

You have two options with the copper

1) heavy solid copper (like bus bar)

2) copper powder

You have two agitation options

1) actual stirring - magnetic stirrer for smaller batches or paddle stirring with a drill for larger batches (I used my drill press for this - but you can certainly figure out a way to secure a hand held drill to do the stirring - so you can walk away while waiting for the cementing to do its thing)

2) bubbler - a single hose bubbler will work fine for say a 5 liter beaker - when I was cleaning up may waste before moving I had three 20 gallon drums - 15 gallons solution per drum - with a 4 hose bubbler per drum

To put it in perspective - I had about 800 gallons of waste - about 200 gallons of that was AR PGM stock pot (PGMs left after dropping gold) when I cemented that (if memory serves me right) I got 43 grams of PGM cement (mostly Pd with some Pt) which I melted with oxy/propane - which in turn helped pay for my move from Wisconsin to Oregon

As a Side note; - I also had a couple kilos of silver used as a collector in smelting - which over the years had become loaded with PGMs - between the two (cement & silver collector) it "more" then paid for the move

I posted about that cost here

:arrow: Silver Cementing

I've done it so long that I've experienced about everything that can happen in the process and have learned how to overcome it

& I guess that is my point also - there is no question that cementing PGM is more difficult then cementing gold or silver - but as long as you follow the three rules - there is no reason why you can't cement it using copper - get it all to come down - & get it to come down relatively clean (95% or better) --- even if it is a low Ph high concentrated acidic solution

As a note; - concerning strong/concentrated acidic solutions --- though I have used both solid copper with a bubbler - & copper powder with stirring - I have found that what works best is to use copper powder - once "most" (but not all) the Pd is dropped with the copper powder - put your bubbler hose in - hang your solid copper & let it finish --- that way you don't risk putting to much copper powder in at the end thereby contaminating the Pd with un-dissolved copper

Now - all that said (& sorry this is turning out so long) considering what Goran posted about the Wacker process --- I have "never" used the CuCl2 process in my refining - cementing Pd from CuCl2 "may" have issues that I an unaware of ---so :?: :?: :?:

All of my experience is with nitric &/or AR solutions --- in the case of nitric - or AR solutions I know three things for sure

1) if you have free acid capable of dissolving more metal - the copper will at some point use up the free acid - at which point the copper will start cementing the PGMs & they will stay cemented out

2) you can do it whether it's a strong/concentrated acidic solution - or a weak/diluted solution

3) adjusting Ph with a base is something I would never do (again) - it's just not needed & can/may cause problems - it only complicates the chemistry with a chemical soap that can cause unintended reactions (not saying it will - but certainly can)

Kurt

 

[Shark]

Thanks Kurt, that reply will require reading several times for me as there is much there to consider. It also explains some things I have ran into in the past and will help with future waste clean ups.

 

[Dbaschiera]

per the underlined - although Ph plays "somewhat" of a role concerning passivation (the Pd bonding to the copper) that passivation is easy to overcome no matter how low the Ph is (&/or for that matter how concentrated the acid in the solution is) in other words you can do it - without worry of passivation - from a straight up concentrated AR as long as you follow the three rules that prevent the Pd from bonding to the copper

1) Aggressive agitation of the solution

2) copper surface area - more is better - just be sure you don't put so much that it interferes with the agitation

3) DO NOT put the copper in until AFTER the agitation is started

Example; - you can lets say do a batch of white gold or dental gold (which will have PGMs) - dissolve it in AR - drop your gold - pour off the "concentrated" AR & cement that to recover the PGM with out any issues - as long as you follow the three rules

You have two options with the copper

1) heavy solid copper (like bus bar)

2) copper powder

You have two agitation options

1) actual stirring - magnetic stirrer for smaller batches or paddle stirring with a drill for larger batches (I used my drill press for this - but you can certainly figure out a way to secure a hand held drill to do the stirring - so you can walk away while waiting for the cementing to do its thing)

2) bubbler - a single hose bubbler will work fine for say a 5 liter beaker - when I was cleaning up may waste before moving I had three 20 gallon drums - 15 gallons solution per drum - with a 4 hose bubbler per drum

To put it in perspective - I had about 800 gallons of waste - about 200 gallons of that was AR PGM stock pot (PGMs left after dropping gold) when I cemented that (if memory serves me right) I got 43 grams of PGM cement (mostly Pd with some Pt) which I melted with oxy/propane - which in turn helped pay for my move from Wisconsin to Oregon

As a Side note; - I also had a couple kilos of silver used as a collector in smelting - which over the years had become loaded with PGMs - between the two (cement & silver collector) it "more" then paid for the move

I posted about that cost here

:arrow: Silver Cementing



& I guess that is my point also - there is no question that cementing PGM is more difficult then cementing gold or silver - but as long as you follow the three rules - there is no reason why you can't cement it using copper - get it all to come down - & get it to come down relatively clean (95% or better) --- even if it is a low Ph high concentrated acidic solution

As a note; - concerning strong/concentrated acidic solutions --- though I have used both solid copper with a bubbler - & copper powder with stirring - I have found that what works best is to use copper powder - once "most" (but not all) the Pd is dropped with the copper powder - put your bubbler hose in - hang your solid copper & let it finish --- that way you don't risk putting to much copper powder in at the end thereby contaminating the Pd with un-dissolved copper

Now - all that said (& sorry this is turning out so long) considering what Goran posted about the Wacker process --- I have "never" used the CuCl2 process in my refining - cementing Pd from CuCl2 "may" have issues that I an unaware of ---so :?: :?: :?:

All of my experience is with nitric &/or AR solutions --- in the case of nitric - or AR solutions I know three things for sure

1) if you have free acid capable of dissolving more metal - the copper will at some point use up the free acid - at which point the copper will start cementing the PGMs & they will stay cemented out

2) you can do it whether it's a strong/concentrated acidic solution - or a weak/diluted solution

3) adjusting Ph with a base is something I would never do (again) - it's just not needed & can/may cause problems - it only complicates the chemistry with a chemical soap that can cause unintended reactions (not saying it will - but certainly can)

Kurt

Hi Kurt I am new to this site I have been following for a while and I’ve been reading and learning. While reading your post, I noticed that you were from Wisconsin I too am from Wisconsin just curious as to what part of the state you were from…. I have enjoyed reading your posts and learning a tremendous amount about this process thank you so much for participating and being one of the people to help individuals like myself learn this process.

 

[Cap1]

What I mean is that any pgm:s that you have cemented out in your stock pot could go through the process of gold recovery but in the end just being ignored and put back in the stock pot after the gold is extracted. It will build up over time.

This is just an example of how you can treat the stock pot. I might have left out some clues or procedures so don't use it as a blue print for stock pot treatment.
- Filter or decant the stock pot to separate liquid from cemented metals in the sludge.
- The liquid (old stock pot) should be tested and if barren of values it goes off to the waste treatment.
- The solids contains some gold, silver chloride, pgm:s but also other crap from the refining process.
- Treat the slime with aqua regia, now pgm:s and gold should be in solution. Silver chloride in solids.
- Remove solids and treat separately, for example recover silver.
- Denox and drop the gold from the liquid. Wash and melt.
- The liquid after recovering gold now contains any pgm:s from the old stock pot. his can now be added to a new stock pot with more copper, the pgm:s should cement out on the copper and any gold still in suspension sinks to the bottom.

If you have small amounts of pgm in the waste liquid from the old stock pot then testing with stannous will give you a hint if it is a lot or just traces.
If you cement the copper on iron then any pgm:s should follow the copper and you can recover it from the copper in the future, for example in a copper cell.

I don't know how powerful copper (II) chloride is but I know it can dissolve palladium. Iron chloride seems to be weaker so it should have harder to dissolve palladium, if even possible. At least with a lot of copper powder around the palladium is easily cemented out and embedded in the copper powder. So when you recover copper from your waste it also extracts any gold or pgm:s that you missed.

I'm collecting any copper I'm cementing out in my waste stream and I'm going to do a copper cell some day to see if I left any values behind... and because it's a cool thing to do.

Chemistry is messy and no process is ever 100%. There is always losses along the way. By designing your refining and waste stream properly you can get back some of the losses you made during refining. The question to ask, is it worth it? That answer is quite different if you are a hobby refiner or a professional refinery with staff on salary.

I hope this answers your question.

Göran

I was wondering, can I use the copper collected from the iron stock pot and put it back into my copper stock pot. This way you keep recycling the copper.

 

[FrugalRefiner]

True, but you'll also potentially be recycling any metals below iron in the electromotive series, including cadmium, cobalt, nickel, tin, lead, tungsten, antimony, arsenic, and bismuth. It depends on what might be in your waste stream.

Dave

 

[cejohnsonsr1]

I was wondering, can I use the copper collected from the iron stock pot and put it back into my copper stock pot. This way you keep recycling the copper.

You can recover the copper, but it's cheaper to just buy copper for cementing.

 

[Jado]

True, but you'll also potentially be recycling any metals below iron in the electromotive series, including cadmium, cobalt, nickel, tin, lead, tungsten, antimony, arsenic, and bismuth. It depends on what might be in your waste stream.

Dave

would this be possible to circumvent by cold precipitation? Should keep tin, bismuth & antimony in suspension at least I think