# reverse electroplating



## joekbit (Jan 18, 2015)

Ok I saw some things in the tutorial area on the subject of reverse electroplating. I built a cell, 12v at 1.aph with 50% sulfuric. Sometimes I get beautiful foils, sometimes no foils. The question is, is the brown looking sludge the gold from the material that does not produce foils? My solution stays very clear, just a slight tint of blue, so everything is very visible in the solution. Like I said, some material just flakes off as foils and other material the gold just seems to disappear and the sludge builds up on the cathode. Is that the gold, because I have a lot of it. 

The material I am running is etching test plate material, no solder, no chips, nothing but flat boards with many different size holes, dots and so on.


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## Geo (Jan 18, 2015)

50% sulfuric is too diluted to use for electrolyte. It needs to be as concentrated as you can get it. If you can't buy it concentrated, then you may have to concentrate it yourself.


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## necromancer (Jan 18, 2015)

#1: are these fibre boards ? i would suggest the AP method, personally you may not be getting all the gold with the cell

#2: the blue colour in your cell is the copper being dissolved by the dilute sulfuric acid. the brown looking sludge is the gold.

i have never had foils using my cell, just very fine powder. i have only used it on small metal gold plated items


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## goldsilverpro (Jan 18, 2015)

Just remember that, in order to strip the gold from each piece, each piece must make direct electrical contact to the power supply. This stripper doesn't strip just sitting in the solution. It has to have some juice pushing it. However, in my studies, there sometimes is about a 1/2" area around the connection where even unconnected parts will strip. Thinking about this, I think it might be that this fog area is duly high in oxygen, which you would expect the anode to produce.


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## joekbit (Jan 18, 2015)

Well I got the answers I needed, thanks. The sulfuric was fuming but I diluted it. I also concentrated it, that's easy to do. It was 35%, I evaporated 100ml down to about 30, did that 3 times so it was very concentrated, then I took 100ml of water and added 100ml of the concentrated sulfuric. As far as the foils, they are big, some I would guess as large as 1/2 cubic inch. No problem seeing them floating around. 

This material has 3/4 inch strips 2 sides and the edges. Lengths vary from 12 inches to 6 inches, plus all the dots and shapes on them. I have 10lbs to process. Really nice material.

I tried AP and it breaks the gold down so small I need to use a 3 micron filter to catch it. Plus I end up with this plastic like material floating around making it impossible to separate out during filtration. So the cell seems to be my best option.

Thanks again


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## goldsilverpro (Jan 18, 2015)

joekbit said:


> Well I got the answers I needed, thanks. The sulfuric was fuming but I diluted it. I also concentrated it, that's easy to do. It was 35%, I evaporated 100ml down to about 30, did that 3 times so it was very concentrated, then I took 100ml of water and added 100ml of the concentrated sulfuric. As far as the foils, they are big, some I would guess as large as 1/2 cubic inch. No problem seeing them floating around.
> 
> This material has 3/4 inch strips 2 sides and the edges. Lengths vary from 12 inches to 6 inches, plus all the dots and shapes on them. I have 10lbs to process. Really nice material.
> 
> ...


I think I know the stuff you're doing and I must warn you that it's pretty thin gold. There have been a few threads discussing it.


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## Geo (Jan 18, 2015)

I seriously doubt you managed to put gold into solution with such diluted acid. I would be afraid to guess what any sludge or precipitate you may have but I would assume that the only gold content of it is what foils are locked up in it. I wouldn't just toss it but I wouldn't just add it blindly to any recovered gold until you have tested it first.


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## necromancer (Jan 18, 2015)

if you get gold flakes, foils or powder with the plastic, it should not be a problem with AP, when you put the gold into solution either with AR or HCL/CL and filter, your plastic will get caught in the final filter & you will be left with your clean AuCl.

sorry, can never remember if this is AuCl(II) or AuCl(III)

but if there is enough copper on your boards to carry the current into the cell & it works for you all the better.

i do like the cell due to the fact that it does not leave lots of liquid waste & it's recyclable.


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## Harold_V (Jan 19, 2015)

goldsilverpro said:


> Just remember that, in order to strip the gold from each piece, each piece must make direct electrical contact to the power supply. This stripper doesn't strip just sitting in the solution. It has to have some juice pushing it. However, in my studies, there sometimes is about a 1/2" area around the connection where even unconnected parts will strip. Thinking about this, I think it might be that this fog area is duly high in oxygen, which you would expect the anode to produce.


In reality, persulfuric acid is generated in the proximity of the anode, and that's what dissolves the gold. As it (the gold) migrates away from the anode, the persulfuric acid ceases to exist, so the gold self precipitates (sulfuric acid won't hold gold in solution) as the familiar black slime that is eventually recovered.

Harold


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## joekbit (Jan 22, 2015)

Harold_V said:


> goldsilverpro said:
> 
> 
> > Just remember that, in order to strip the gold from each piece, each piece must make direct electrical contact to the power supply. This stripper doesn't strip just sitting in the solution. It has to have some juice pushing it. However, in my studies, there sometimes is about a 1/2" area around the connection where even unconnected parts will strip. Thinking about this, I think it might be that this fog area is duly high in oxygen, which you would expect the anode to produce.
> ...



Thanks Harold, I use the 90% but diluted it, Example: I had 200ml H20 and added 300ml 90% sulfuric. So its' 50% +. As far as sulfuric holding gold in solution, yes I know, it will not. My way of describing it is like this. Looking at the elements we see things in a particular place by electron value. Some transition metals are or have a positive charge, some negative and some are neutral. 

So to me, I see an electron interaction or exchange which breaks the bond of the gold to the base metal, the gold then follows the electron flow seeking electrons to bind to. Yes or No? The reason we have lead and copper in lead acid batteries is because of the efficiency of the 2 metals to transmit electrons / share. The presence of any metal between that results in that metals electron bond being broke it then seeks a new bond. 

I know this is more physics and electrical than chemical and many may not understand. I may be way off base, I'm recalling my physics and metallurgy from 30 years ago. To me everything about recovery and refining involves electron bonds, break the bond however you desire or can and you have the metal in your grasp.


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## Geo (Jan 22, 2015)

It's about the same of chemical and electrical. You are not trying to break the bond between the gold and the base metal. You are actually dissolving the gold at the gold/liquid interface. The sulfuric is actually electrolized and is converted to persulfuric acid (Peroxymonosulfuric acid) which dissolves the gold in the vicinity of the anode. The persulfuric is short lived and is converted back to sulfuric acid once it leaves the direct vicinity of the anode. The dissolved gold gets carried by the electrons flowing away from the anode towards the cathode. Once the persulfuric acid decomposes, the gold precipitates as a metal resembling black powder.


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## g_axelsson (Jan 24, 2015)

joekbit said:


> Thanks Harold, I use the 90% but diluted it, Example: I had 200ml H20 and added 300ml 90% sulfuric. So its' 50% +. As far as sulfuric holding gold in solution, yes I know, it will not. My way of describing it is like this. Looking at the elements we see things in a particular place by electron value. Some transition metals are or have a positive charge, some negative and some are neutral.


All metals are neutral, when a metal takes on or loses an electron it becomes an ion or part of a compound.



joekbit said:


> So to me, I see an electron interaction or exchange which breaks the bond of the gold to the base metal, the gold then follows the electron flow seeking electrons to bind to. Yes or No? The reason we have lead and copper in lead acid batteries is because of the efficiency of the 2 metals to transmit electrons / share. The presence of any metal between that results in that metals electron bond being broke it then seeks a new bond.


The electron transmission that takes place is between the persulfuric acid and the gold, gold is dissolved.
The movement of the gold ions is dominated by diffusion, not electromotive forces. That is true for most electrolytic cells and the reason why larger plants uses pumps to agitate and move the electrolyte to keep fresh electrolyte close to the electrodes and minimize polarization effects.
There is no copper in lead acid batteries, it's lead, lead oxide and lead sulfate. Ref : Wikipedia
A gold ion is just as happy as an ion (having it's own extra electrons) as it is as a metal (sharing it's electrons with it's neighbor). The driving force in chemistry and every other process is to maximize the entropy of any closed system. http://en.wikipedia.org/wiki/Gibbs_free_energy#Gibbs_free_energy_of_reactions
If we want to drive a reaction towards a non spontaneous result then we need to add energy from another source, for example when we create persulfuric acid by electrolyze sulfuric acid. The persulfuric acid isn't created spontaneously but needs the extra energy to be created. The smart thing with using concentrated sulfuric acid is that base metals are passivated by the concentrated acid and not dissolved. When using diluted acid the base metals are also dissolved and weakens the acid, consuming it, while the gold takes a lot longer to dissolve.
My experience is that pure gold will dissolve or erode when used in a cell with diluted sulfuric acid, at least when the voltage is high enough. 



joekbit said:


> I know this is more physics and electrical than chemical and many may not understand. I may be way off base, I'm recalling my physics and metallurgy from 30 years ago. To me everything about recovery and refining involves electron bonds, break the bond however you desire or can and you have the metal in your grasp.


Yes, you are quite way off base. That's my opinion as a physicist.

Göran


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## joekbit (Feb 6, 2015)

Thank you all for your input, I completed all 10 pounds. Some in the cell and some in AP. My cell was a 600 ml beaker so I could only do a couple pieces at a time. It worked very quick due to the proximity of the anode to the cathode but required a lot of observation. Back and forth to the cell to change out the pieces. As far as the material, well the primary base metal was copper so it was easy to just clip my electrical / positive lead directly to the material. No copper mesh was needed. 

I accumulated all the mud in a jar and washed it numerous times with hot water to remove as much sulfuric as possible. I just kept washing and decanting the mud over and over until the water was clear. At that point I used 70% HNO3 added in small increment to dissolve the copper from the mud. In short I kept the reaction going until there was no reaction. I then decanted and just to make sure the copper was gone I put a few drops of HNO3 on the remaining mud. The end result was no reaction at all. So I felt confident I had clean gold powder. I was wrong, read below.

Once again I went through numerous washes and my powder is currently drying. Wet weight was close to 6 grams, current weight 3.47 grams, still slightly damp but dry enough to hold its' shape. I'm seeing small traces of copper crystals. Suspect Cu(NO3)2, so for now I'm just going to let it be. In the future when I do some AR I will add it in for another refine. I still have a lot of filtered foils I need to deal with from the AP batches. Weight of foils minus filter weights just under 9 grams. Yes I do expect a dramatic weight loss, that 9 grams is very dirty / contains mostly base metals. So far for me I noticed if I move the decimal 1 place it's pretty close. So I figure about 1 gram refined from the foils. 

The spent AP solution checks positive with stannous but it's black as coal (the solution) so I'm not sure how I want to recover the Au from it at this point. Slightly over 2 liters.

In short I still have a lot of work to complete to get the final result. :roll:


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## goldsilverpro (Feb 6, 2015)

joekbit,

90% sulfuric is about the perfect strength. I don't understand why you diluted it.

Diluting it will strip the gold but, at the same time, a lot of base metals will dissolve, which is undesirable. The gold will be more difficult to recover and the solution's life will be much shorter.


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## joekbit (Feb 6, 2015)

goldsilverpro said:


> joekbit,
> 
> 90% sulfuric is about the perfect strength. I don't understand why you diluted it.
> 
> Diluting it will strip the gold but, at the same time, a lot of base metals will dissolve, which is undesirable. The gold will be more difficult to recover and the solution's life will be much shorter.



I was wondering about that. I found it out that's for sure, a lot of copper in my mud. In the future 90%., but I got everything cleaned up. I do like the process, it seems far more efficient with a whole lot less chemical waste. When the stripping reaction slowed I just filtered the solution and reused it. Actually I decanted it, removed the mud then filtered it. Due to evaporation some volume was lost so I just added some more 90% sulfuric and pressed on. In all it only required about 800 ml to process about 8 lbs. The AP on the other hand was about 1400 ml per pound. That's a huge difference in waste solution to deal with. The truth is, as far as I can tell, my 800 ml of sulfuric can still be used for more processing. The AP is done for, 2800 ml of waste. I started treatment of it today because I don't want it building up.

The nice thing about this material was its' simplicity, base metal (copper) and gold plating.


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## nickton (Dec 27, 2017)

From what I understand you can also use AP solution indefinitely by cementing out the copper, tin, and silver with the right kind of metal. There is that list somewhere that tells the order of metals to get out what's below (or is it above) it. I know that's a bit vague but I'm hoping someone will chime in here who knows more about what I'm talking about. I haven't been on this forum for a while and am a bit oxidized in the gray area if you know what I mean.


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## niks neims (Dec 27, 2017)

please double-check what I am about to write, as I am mainly doing it to test my current understanding about AP 

first of, "Acid Peroxide" is a misnomer, correct name would be copper II chloride; it is an awesome method for dissolving copper (mainly for processing gold-fingers) first developed by GRF user lazersteve. AND it needs copper II chloride to work - it is the ingredient that is doing all the work - dissolving copper metal and becoming copper I chloride in process, to tur it back you must oxidize it, either by bubbling air(oxygen) through it or adding hydrogen peroxide

once you have a batch of it going you can re-use it for many runs, you just need add oxygen to solution (bubble air through it) once it becomes dark brown to make it become emerald green again... I think there is a limit for how much Copper HCl can hold, I think it was about 1:4... if you have saturated you solution (I think it won`t change color then) you must either add more HCl, discard the solution or remove copper. I don`t think that can be done by cementing copper on other metal - this other metal just goes in to solution and you have basically ruined your "AP" (it is easier to write than copper II chloride) - there is no more copper II chloride; there is information on forum about removing copper electrolytically, I tried it, and it worked very well - I used graphite anode and iron cathode and had very nice copper deposite growing there, I think that any other metals in the solution (gold, tin, iron) deposits at the same time and you are left with somewhat clean HCl - in this case I think that you can re-use it almost indefinately, just be careful to regulate your current - if not, it gets quite hot - eaven boiling at the anode, and HCl decomposites - Cl gas escapes...

step with cementing everything on copper, then iron, is important part of waste treatment but it should not be done if you want to re-use your "AP"


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