Ceramic CPU recovery gonne wrong. Help please.

[Wingedcloud]

Hello fellow refiners.

It's been a long time since i last wrote on the forum, mainly because all the learning i received from it have granted me the knowledge to perform quite well on my recovery ventures

However, one does not possess all the knowledge there is, and there is always room for some mistakes, even in processes you thought you have already mastered (at least, that's what I think :lol: )

I come in search of help regarding a Ceramic CPU recovery process.
I have employed the usual AR leach of said CPU, followed by an addition of ice and some H2SO4, to remove some silver chloride and lead from the solution.
Turns out that I was careless and added a little too much nitric at the end of the leaching, resulting that my solution ended up with too much free nitric at the precipitation step.
Since I do not have access to sulfamic acid, urea or any other "denoxing" chemicals, I decided that I would denox my way through with SMB (KMB in my case). Did no go well.
I ran out of KMB (approx. 225g) and pushed through with copperas (FeSO4).
I noticed a white precipitate forming, similar to the one we get when removing silver in the form of chloride, from a silver nitrate solution.
I stopped adding copperas, as I realized I was not doing any good, and let the whole thing settle for a day.

This morning I add this.



I filtered my solution and did a stannous test. Seems to have yet some small amount of gold in it.


Did a test on the white precipitate by adding HCl, to understand if it would dissolve it.


The filtered precipitate can be seen in the picture below. It seems to have hydroxide consistency, but how could I have gotten an hydroxide, if I have added no hydroxide to my solution and it is still quite acid ?


Given that before I added SMB and Copperas to my solution, it gave me a strong stannous test result for gold, and now it's weaker, am I to conclude that most of the gold is in the white precipitate?

How should I proceed from now on? Dissolve the white precipitate again in AR and try to precipitate the gold again?

Would appreciate some advice from any experienced member or from someone that has gone through some similar situation.

Kind regards,
Winged

 

[Lino1406]

Too many variables. Where lead comes from? Why sulfuric acid will "remove" it? Where the ceramics in your process? For begining

 

[Wingedcloud]

Too many variables. Where lead comes from? Why sulfuric acid will "remove" it? Where the ceramics in your process? For begining

Hello Lino1406.

Regarding your question:

"Where lead comes from? Why sulfuric acid will "remove" it?"
When added to the AR solution, sulfuric acid will remove lead in the form of lead sulfate. I believe lead may come from solder present in old ceramic CPU.

Where the ceramics in your process?
I am not sure what you mean by this, but the ceramics are completely free of gold. I have them stored for now.

Winged.

 

[Lino1406]

So if lead is there then tin is there too? In this case put in AR, it will dissolve only the gold but not expect a meaningful amount

 

[archeonist]

Next time, in this case, you should use the evaperation method to get rid off free nitric. Another method is to dissolve some 24k gold, If you have it laying around.., it will get rid of the nitric too.
For now, don't panic your gold is still there. Just wait for someone to help you. I never had a problem like this because I always followed my mentioned methodes, I have ideas but there are members Who have had the same problem. But a question for you, did you really put 225g KMB in solution? :shock:

 

[nickvc]

To recover your gold I would suggest adding a copper bar to cement it out and start over on the refining.

 

[archeonist]

To recover your gold I would suggest adding a copper bar to cement it out and start over on the refining.

That sounds like the way to do it. The excess copper will use up the nitric and the rest of the copper will cement out the gold and all other metals above copper in the reactivity series.
After everything has settled to the bottom (I would wait a few days up to a week), decant the remaining clear solution. Wash the precipitate using tap water and boil some time so all salts will dissolve and decant, you could repeat this once or twice.
Now add HCl and 50% tap water and a little bit of heat, not to much because your gold is a powder and that alone will increase the reaction rate when you start to drop nitric in, you could get a boil over, so use drops! Look at the reaction, of all fizzing and gas formation stops, drop some more untill the point that dripping nitric has no effect anymore. From here you can put ice in and filter and finally SMB

 

[Wingedcloud]

To recover your gold I would suggest adding a copper bar to cement it out and start over on the refining.

That sounds like the way to do it. The excess copper will use up the nitric and the rest of the copper will cement out the gold and all other metals above copper in the reactivity series.
After everything has settled to the bottom (I would wait a few days up to a week), decant the remaining clear solution. Wash the precipitate using tap water and boil some time so all salts will dissolve and decant, you could repeat this once or twice.
Now add HCl and 50% tap water and a little bit of heat, not to much because your gold is a powder and that alone will increase the reaction rate when you start to drop nitric in, you could get a boil over, so use drops! Look at the reaction, of all fizzing and gas formation stops, drop some more untill the point that dripping nitric has no effect anymore. From here you can put ice in and filter and finally SMB

Hello archeonist and thank you very much for you precious advice, building on nickvc reply.
I have little to no experience with the cementation process.
Just after some copper as dissolved by the action of nitric acid, and all the acid is used, will the gold cement on the remaining copper, if I understood correctly. I suppose I will have to test my solution with stannous to know when all the gold has cemented. Will zinc work for cementation too? Because I have some zinc sheet stored.
What about the white precipitate? Am I to assume it is gold free?

 

[Wingedcloud]

Next time, in this case, you should use the evaperation method to get rid off free nitric. Another method is to dissolve some 24k gold, If you have it laying around.., it will get rid of the nitric too.
For now, don't panic your gold is still there. Just wait for someone to help you. I never had a problem like this because I always followed my mentioned methodes, I have ideas but there are members Who have had the same problem. But a question for you, did you really put 225g KMB in solution? :shock:

I may have exaggerated a bit, but for sure more than 125g. More like 175-200g
Thought I could KMB my way through nitric. Was terribly wrong.

 

[Shark]

You can get through an excess of nitric with the SMB or KMB. The thing is you can't make it work if the excess is very large. If you expect 10 grams of gold and use 20 grams of precipitant the odds are you need to use another method to denox. As suggested heat will work just fine. With each drop that redissolves it will consume a small amount of the nitric. If you have a large excess it is waste of SMB (in your case KMB) such that it is easier and more effective to go another route. I don't quite know why but it seems to happen with me a lot when doing ceramic CPU's or even ceramic IC's. Especially when using Poorman's AR it seems I always have to use a combination of heat and Sulfamic acid to get it under control.

 

[archeonist]

Zinc will work too. The white precipitant could be various salts like some PbSO₄, AgCl, and I think also KMB. The saturationpoint for KMB is 540g/L, you put in like 200g, if the volume of your solution was around 250 mL than a lot of the precipitant is just undissolved KMB. In acidious solutions the saturationpoint would be a bit different but it is just a guideline

 

[Wingedcloud]

Yeah I have pushed through nitric with KMB before, but this time it was just too much for it to handle :roll:
If I may ask, how exactly will heating up my solution remove free nitric? I know Hoke talks about it on he book, when she mentions heating down to a pulp, but what is the phenomenon behind this action?
On a related note, I was whole day out and when I came back, I noticed something about the stannous test I posted in the morning.



Does the purple color means gold in solution? I usually get a black spot, but I recall reading somewhere that purple is also an indication of gold presence.

Thank you all for your tips on cementation. I will make arrangments to do it and will post results when I am done

Winged

 

[kernels]

Nick is 100% right, at the point where you realized that you had used way too much Nitric, my first step would have been to grab a Copper bar, heat to 40 deg C and wait for an hour or two for all the Nitric to be consumed and all the Gold to be cemented. Then, decant the liquid (after testing), add some fresh HCl and re-dissolve the Gold. This way you also end up with a much cleaner solution.

 

[Shark]

I am no chemist but my understanding is that nitric acid is an acid dissolved or trapped in water. By heating it the bond that holds it in water is broken and aids in the release of the acid leaving it's water behind. While I have read Hoke a few times, I have never reduced it as much as she recommends. Sulphamic acid will neutralize the nitric and convert to Sulfuric acid which then aids in the reduction of any lead that may be present. While that can help, I would still use heat if there was a large excess of nitric to start with.

While cemetation will also work well I haven't used it that often. It does seem to work best in the recovery area better than precipitation does quite often. I am working towards trying a process for the first time where using a copper bar will save hours of time and may have to change my view on it's use afterwards. But learning new things is the excitement of this refining for me.

 

[kernels]

To remove excess Nitric with heat, you end up having to evaporate your solution down to almost nothing, like a few goopy tablespoons, then add fresh HCl a few times. It takes forever and you end up evaporating a ton of acid fumes off.

Nice clean Copper bar, heat the solution a little bit (I go for around 40 deg C or so), at first you will see the Nitric consuming the Copper aggressively (lots of brown fumes as usual), then after the excess Nitric is consumed, your Gold cements out very fast and you end up with reasonably settled brown powder at the bottom of your beaker. Too easy.

 

[kernels]

Youtube is generally not that popular here, but this shows what you can expect: https://youtu.be/InH8eC9Imtg?t=851

 

[Shark]

I for one watch YouTube quite often. There are many knowledgeable people on there. The downside is for every one who knows what they are doing there are 100's who are causing more harm than good. Knowing which to follow isn't easy for those who are just getting started as I have removed many links there from my list as I learned more on the subject over the last few years.

Any way, I have watched the video you linked to several times, often out of boredom with other channels. I often learn many small things from some videos that aren't always concerned with the actual subject matter, such as how to fold a filter paper properly.

 

[archeonist]

I for one watch YouTube quite often. There are many knowledgeable people on there. The downside is for every one who knows what they are doing there are 100's who are causing more harm than good. Knowing which to follow isn't easy for those who are just getting started as I have removed many links there from my list as I learned more on the subject over the last few years.

Any way, I have watched the video you linked to several times, often out of boredom with other channels. I often learn many small things from some videos that aren't always concerned with the actual subject matter, such as how to fold a filter paper properly.

I think you better could say: there are only a few knowledgeable people on there.. A lot of them do dangerous things concerning their health on a long term, they make it look easy burning chips in their gardens, dealing with dust, not wearing gloves etc.

If you know what you are looking at you could actually learn something from it but be carefull not to learn the bad things.

 

[kurtak]

The excess copper will use up the nitric and the rest of the copper will cement out the gold and all other metals above copper in the reactivity series.

Per the underlined --- you got that wrong --- copper cements "only" the metals BELOW copper

That's why we use copper

Zinc will work too.

In this case - NO - you do NOT want to use zinc --- he started with CPUs &/or ceramic ICs - zinc is "way high" in the reactive series & will therefore cement "everything" BELOW zinc which means you will end up with a mess of just about everything dissolved in the "first place"

zinc is used (only) when your solution is relatively clean to start with - such as cementing PGMs "after" gold has been dropped with SMB (or other chem precipitant)

Edit to add; - in this case - cementing with zinc is BAD advice :!:

Kurt

 

[Wingedcloud]

Zinc will work too.

In this case - NO - you do NOT want to use zinc --- he started with CPUs &/or ceramic ICs - zinc is "way high" in the reactive series & will therefore cement "everything" BELOW zinc which means you will end up with a mess of just about everything dissolved in the "first place"

zinc is used (only) when your solution is relatively clean to start with - such as cementing PGMs "after" gold has been dropped with SMB (or other chem precipitant)

Edit to add; - in this case - cementing with zinc is BAD advice :!:

Kurt

Hello,

Exactly my thought after examining the reactive series kurtak !!
Since I wanted to restrict the cementation to gold only (since i doubt PGM will be in solution), I thought it would be best to use copper
I refered zinc because it is usually used to drop gold, but, as you said, in much cleaner solutions.

Updating on my initial post, and following the helpful advices given, I started the cementation process Tuesday in the morning.
I am currently standing on this:





Considering the red gases, I believe there is still some copper being consumed by nitric and the stannous test tells me there is still some gold in solution (in need of a more keen and trained eye for this one :lol: )
Got already some deposit at the bottom of the jar, but still not over I guess.

Can someone consolidate on these conclusions?

Thanks !!
Winged