# Gold Stratification?



## Meh1 (Dec 4, 2012)

Ok I just have a quick question. I used AR to recover gold from cell phone components. No problems there, everything went well. I cleaned the powder with hot water three times. Now this is where it gets kinda weird. I went to clean the gold powder again with hydrochloric acid and an equal amount of water. I let this sit over night. When I returned the gold powder had gone back into solution. Odd but no problem I dropped it again with SMB. Now I have nice heavy red flake gold powder at the bottom of my container. The strange part is that there also appears to be gold powder suspended in what I assume is a stratification of the acid/water mixture. But that shouldn't happen because the acid is water soluble right? Is that gold floating above? Or is it just another contaminant? I have an idea of how I should proceed from here but I would like the expert opinions from this forum before making a mistake and losing values. Thanks in advance -John


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## Geo (Dec 5, 2012)

is it solids floating on the surface or powders floating in the solution? a picture would help.


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## Meh1 (Dec 5, 2012)

Ill try to get a picture posted later today. It's the end of the semester so I'm really busy. It is solids floating. It looks suspiciously like the red gold flakes that settled to the bottom of the container. And if I drop a little more SMB into the solution it causes it to drop back down. But then a few hours go by and it stratifies again. Has anyone experienced this before?


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## kronix (Dec 6, 2012)

You might have oils in your solution causing the powder to float. 

I would decant what you can to get most of the powder, hen maybe add a surfactant like jet dry 1 drop should do. This should settle your remaining powder.

Incinerating your foils ( red hot but not melted) prior to dissolution solved this problem.

-Ian


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## Geo (Dec 6, 2012)

use a spray bottle like the type you mist a plant with and spray the top of the solution. this usually breaks the water tension and the powders will sink. if the spay doesnt work,put on a latex or rubber glove and place a small drop of dish soap on your finger tip and touch the surface of the solution. spray the solution again to make sure it all drops.


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## NobleMetalWorks (Dec 6, 2012)

Meh1 said:


> Ok I just have a quick question. I used AR to recover gold from cell phone components. No problems there, everything went well. I cleaned the powder with hot water three times. Now this is where it gets kinda weird. I went to clean the gold powder again with hydrochloric acid and an equal amount of water. I let this sit over night. When I returned the gold powder had gone back into solution. Odd but no problem I dropped it again with SMB.



You washed three times, but was the solution clear? Sometimes it takes more than three washes. If your Au was dissolved by HCl, that means an oxidizer had to be present. That could possibly have been weak HNO3 but more likely the water you mixed your HCl with was oxygenated, and this was enough to dissolve your gold powder back into solution. Strictly speaking HCl will not dissolve Au, but if oxygen in enough quantity is present in your solution, it will. 



> Now I have nice heavy red flake gold powder at the bottom of my container.



Can you provide a picture of the heavy red flake? You are describing it as red, but it should be a brown color if it's Au.



> The strange part is that there also appears to be gold powder suspended in what I assume is a stratification of the acid/water mixture. But that shouldn't happen because the acid is water soluble right? Is that gold floating above? Or is it just another contaminant?



Sometimes when the Au is precipitated fine, and specially if you are precipitating out of dirty solutions, you may see stratification of the fine gold suspended in solution. Remember, you added HCl to dissolve any base metals in your solution, so I am going to assume your solution is dirty, meaning you have other metals in your solution. Some of that might have been dragged down when you precipitated with SMB. If that happened, that might also be causing the stratification that you are seeing, with the heavier Au crystals falling faster to the bottom, and whatever other metal you might have in solution taking more time to settle, thus causing the stratification in your solution.

Sometimes it's just simply your Au settling out and there is nothing wrong with your solution, sometimes it takes a long time to settle.

Scott

I have an idea of how I should proceed from here but I would like the expert opinions from this forum before making a mistake and losing values. Thanks in advance -John[/quote]


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## Meh1 (Dec 7, 2012)

Thanks for the advice to everyone. I describe the gold powder as reddish. Perhaps i'm color blind  . I decided to filter the solution and place all of it back into AR with some other powder I had been meaning to refine further. Ill drop it with SMB this weekend and let you know the results. As of now I haven't lost anything but time and acids. But again thanks for the advice everyone. -John


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## butcher (Dec 7, 2012)

I am interested to hear how easy the solutin will filter.


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## Meh1 (Dec 7, 2012)

It filtered alright and I moved the dry solids into AR last night. Ill check on it tomorrow and drop SMB hopefully, I just finished a hellish week at school since its the end of this semester. So i intend to drink a few beers, sit on my bum and work on some arduino stuff ive been meaning to do. Kinda a nerd I know..but it keeps me outta trouble  thanks again for the interest and advice everyone. -John


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## patnor1011 (Dec 7, 2012)

He dissolved in AR, dropped and washed with hot water. Then washed with HCl. 
One can never wash out nitric with just water. That is why your dropped gold went back in solution.


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## Meh1 (Dec 8, 2012)

Thats what i assumed happened. Would washing with sulphuric remove the nitric? How does a person remove the residual nitric? I was confused by the way the powders/acids separated. Could this be due to temperature? The place that I work on stuff never gets below freezing but does dip into the low 40's throughout the night without a heater running.


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## patnor1011 (Dec 8, 2012)

Incinerate.


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## Meh1 (Dec 29, 2012)

Thanks everyone for the information..turns out the floating bits were just more contamination..still unsure how the water/acid was able to stratify..but doesn't matter problem solved..also patnor1011..I would like to thank your for the information on recovering gold from IC's..very very informative..Ive memorized your process and it serves very well..thanks to everyone again.


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## bswartzwelder (Dec 30, 2012)

If you had an excess of Nitric, I would think you could have gotten rid of it by heating the original solution or by treating it with Urea until it no longer fizzed. This would get rid of excess Nitric. If you read the forum, you will find that almost everyone except Harold_V who is familiar with AR tells you to put your gold in the HCl and slowly add Nitric untill it all dissolves. Harold_V tells you that once all the gold has dissolved, add more gold until it will no longer dissolve. That shows you have used up all the Nitric in solution. If I am wrong, I am sure someone will correct me.


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## Meh1 (Dec 31, 2012)

No you are absolutely correct..That is the correct way to go about using AR..One thing that I do as opposed to adding more gold or urea is to use SMB to neutralize the nitric..I have found in my limited experience that urea just makes cleaning harder whereas SMB seems to be easier to remove..I could be incorrect..in fact i most likely am ..but I buy SMB in 10lb lots..and I also have access to urea that is very pure for free (agriculture comprises most of the economy in this region)..but I like to use the SMB because at the very least if I have added to much I will only be dropping minute values and it washes away with hot water..Thanks for the input and happy new years!


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## AndrewSuperD (Dec 5, 2021)

Meh1 said:


> No you are absolutely correct..That is the correct way to go about using AR..One thing that I do as opposed to adding more gold or urea is to use SMB to neutralize the nitric..I have found in my limited experience that urea just makes cleaning harder whereas SMB seems to be easier to remove..I could be incorrect..in fact i most likely am ..but I buy SMB in 10lb lots..and I also have access to urea that is very pure for free (agriculture comprises most of the economy in this region)..but I like to use the SMB because at the very least if I have added to much I will only be dropping minute values and it washes away with hot water..Thanks for the input and happy new years!


Hi all. New to the forum but trying to read it all, especially as I run into interesting things. I’ve really just started my journey as of 6mos ago when my company began to eWaste old equipment that I knew was “good stuff” for gold recovery. Perhaps other metals also, but I’m not there yet. I’m not getting rid of any solutions until I am further in my refining experience. I try to use as little acid as Possible and do my best not to mix metal solutions so I can reuse my AP or Nitric solutions etc. I’ve done a few gold drops (from pins) with success and decided to move onto my IC stash. (Incinerate, ball mill, gravity separate, magnetic separate, Nitric acid, decant, distilled H2O wash, decant, add HCl, bring to 85C, wait/watch, add 1ml more Nitric till reaction stops, repeat 1ml each time till no reaction, raise to 90C, add sulfamic, let cool/cotton filter/dilute with tap H2O, add SMB / stir till some white foam happens). After 8 hours I have this…layered or stratified solution. Looks to be same powder on bottom, 1/2” below surface, and on surface. Stannous of surface layer shows no gold in solution. But what about in second layer? How to test that? Pipette? Is this normal? Fell to 39F over night. High of 63F expected today. Should I just wait 24 hours, or add some jet dry, or more SMB (would middle layer has more gold??), or filter and do second drop?


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## butcher (Dec 5, 2021)

The Stannous surface layer shows no gold in the solution. But what about in the second layer? How to test that? Pipette? Is this normal?

Please explain how you tested your solution for gold, how did you do this stannous chloride test?
Your test procedure does not sound normal and could be suspect of the problem.


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## AndrewSuperD (Dec 5, 2021)

Hi. Thank you for your quick reply. Yes. I tested the top layer of the solution with a piece of filter paper dipped into just the top layer and then two drops of Stannous Chloride on same spot of paper. No color change at all. 

The part of my post about the pipette was regarding if and how I should/could test the lower layer. Should I squeeze the pipette bulb and insert the pipette in through the top layer then release bulb to only allow a sample from the lower layer to enter the pipette. Then test same as above.


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## orvi (Dec 5, 2021)

AndrewSuperD said:


> Hi. Thank you for your quick reply. Yes. I tested the top layer of the solution with a piece of filter paper dipped into just the top layer and then two drops of Stannous Chloride on same spot of paper. No color change at all.
> 
> The part of my post about the pipette was regarding if and how I should/could test the lower layer. Should I squeeze the pipette bulb and insert the pipette in through the top layer then release bulb to only allow a sample from the lower layer to enter the pipette. Then test same as above.


yes, that is exactly what you need to do. still, i cannot understand how it is possible to obtain two-phase mixture from such operation, but if gold is present, it will show up


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## butcher (Dec 5, 2021)

When you said "the stannous surface layer shows no gold in solution" it sounded like you may have added stannous directly to your solution, now we know that is not the problem.

If you dipped a piece of paper into the solution and tested it with stannous chloride that should tell you the gold is reduced, you can try to pipette a few drops of the heavier liquid if you wish and see what it shows. Dipping a Q tip in the mix should get the tip wet with both solutions.

The gold looks like it came from a dirty solution of base metals, black and fluffy, this and other contaminants or organics, oils, could give you a situation where you have two different densities of liquids and where gold can begin to stick to the glass or get hung up in a layer of salts with organics or oils...

I cannot tell from the picture but it also looks like there was very little gold, to begin with, or much here now.
How does the solution filter? Does it just sit on the filter paper, or does it freely pass through the paper, (some metals can give problems with filtering is the reason I asked.


I would probably try to heat the solution and then see if the gold would settle overnight, or just filter the gold from the solution and move on.

When gold is in the solution you normally see sort of a halo or a yellow ring on the top edge of the surface of the solution at the glass's edge, I do not see that in your picture, yours looks clear, making me suspect your gold is reduced


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## AndrewSuperD (Dec 5, 2021)

butcher said:


> When you said "the stannous surface layer shows no gold in solution" it sounded like you may have added stannous directly to your solution, now we know that is not the problem.
> 
> If you dipped a piece of paper into the solution and tested it with stannous chloride that should tell you the gold is reduced, you can try to pipette a few drops of the heavier liquid if you wish and see what it shows. Dipping a Q tip in the mix should get the tip wet with both solutions.
> 
> ...


Thank you again for the help. ”Fluffy” .. great description. I wound up boiling for 30 min or so. My rationale was that little bubbles existed on everything in the beaker and seemed to be holding up the lighter material. I thought boiling would drive more gases out. Don’t know if that makes any sense. The result was that stratification disappeared, all gold at bottom turned black and clumped together. I washed with boiling water. Im now boiling in HCl. (Took a break from it). Seems back on track now. Thank you for the advice. 

So “not much gold”. Im going to wager it’s just shy of 1.5g. Which is very much less than I expected. So I ask myself, “where is my gold?”. I move slowly through these processes so I still have the original beaker with the “post incineration” carbon. Well well well…. It’s settled further over night and there’s a Golden yellow liquid in the beaker again. I hold it up in the sunlight, and man…there are more bond wires in the bottom of the beaker as I can see the gold grouped together. I guess the yellow liquid came from the remaining Nitric mixed with the tap water I washed with as I was pouring off my AR solution. I filtered that cleanly. Btw, the solutions filter cleanly and easily. Slowly because I’m using #4 lab filter + cotton ball crammed in funnel tube. 

I thought my solution was clean, but based on the outcome of my first drop and the fact that gold bond wires remain in the original beaker, I have no reason to suspect the other base metals were removed by my original Nitric soak. I added nitric till there was no more reaction when I was performing the first nitric soak and processing with AR. But it doesn’t appear to have gotten to all the metals. I think that’s because the acid couldn’t get to the entire body of metals through the dense carbon mixture. So you’re right I’m sure, “dirty metals solution”. 

You think I could just mix up another nitric bath and boil the heck out of it to remove base metals, then rinse and then boil in AR? I suggest boiling to agitate the suspension and allow the acids to reach the metals. 

So I just checked on my boiling gold and now there’s something white in the beaker. Assume HCl salt driven out of solution due to evaporation? Added tap water, gave it a swirl and looking normal again. Pictures attached. Stannous Chloride test is colorless. I’ll decant, wash and melt tonight here in a few. Would love to have a recommendation on my thoughts above on the dense carbon suspension.


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## butcher (Dec 5, 2021)

The gold has not been refined in my opinion, you have recovered gold from a dirty solution.
Refine the recovered gold.

Not always needed but helpful. It would not hurt to incinerate the gold powder, you could do this with filter paper or without, if paper or carbon or oils are involved, incinerate the gold till it glows red hot under the flame in the air, and where all the paper decomposes to white ash, besides oil or carbon, this can help if tin is involved to oxidize it and help remove any salts of previous acids.
If you suspected tin, a wash of the gold HCl of the cooled gold will help,
Harold's gold wash technique works wonders.

It takes only a very small amount of acids to re-refine the gold powders. Start with about 4ml HCl and 1ml HNO3 (dropwise as needed with a little heat and time till all the gold dissolves), for each gram of gold powder.
If lead, sulfuric acid, or forming sulfuric in a reaction will help precipitate the lead sulfate from the solution. Being mindful of settling time, decanting, and filtering...

The second pictures look like you have more gold than the first picture did, looking good so far.


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## AndrewSuperD (Dec 5, 2021)

Thanks a bunch. You are exactly right, the gold needs to be refined. However, I need to finish the other 1/2 of this batch and button this project up till after Christmas so I’ll refine then. I have four beads that need to be refined. I just made my fourth bead. Not the best, but attached is a picture of all four. Gold is apparently very difficult to photograph. I don’t know why the left two look black on top, they are beautifully shiny gold. 

If I can discuss in terms of basic processing method AP or Nitric for initial gold separation; the first two are from pins and processed with AP then AR. The third from left is from small batch of old A drive pins and processed with Nitric then AR. The fourth from left is from 2 sided IC chips and processed with Nitric then with AR. The pictures don’t do the first and second beads justice. The third and fourth are no where near as pure or attractive as the first and second. The third and fourth need refining the most. Especially with needing refinement, I think I should have had more gold in today’s button from the IC chips so I’m very disappointed. Based on the amount of gold still in the original beaker, i may have a little more than I processed today. Very disappointing over all. Maybe my Nitric processing needs improvement, Or maybe the IC chips I had were just really low quality, Or maybe there’s more than I think still in the original beaker?

At any rate, thanks a ton for the help and encouragement. I’ll tackle the rest of the original beaker this week.


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## orvi (Dec 6, 2021)

AndrewSuperD said:


> Very disappointing over all. Maybe my Nitric processing needs improvement, Or maybe the IC chips I had were just really low quality, Or maybe there’s more than I think still in the original beaker?
> 
> At any rate, thanks a ton for the help and encouragement. I’ll tackle the rest of the original beaker this week.


processing chips is sometimes hit or miss. one batch you score 2,5g/kg, other 0,4g/kg  could happen anytime to anyone. incinerating and recovering gold from ICs is matter of quantity. below 0,5g Au per batch, whole process and recovery of fine gold drop is very painful and not much rewarding  on the other hand, getting few kilos of IC chips incinerated without health hazard and annoying neighbors with smell or fumes is the other thing 

dissolving entrapped gold from complex matrix of burnt plastics ashes, silica filler, fire retardants and stuff is tedious process. if you have more of this material, in your position, i will be thinking more about smelting incinerated chips with proper flux. separating magnetic and non-magnetic stuff will help. magnetic stuff (separated from bulk of burnt trash) should be readily dissolved in HCl/AP or even AR. non magnetics smelted down with some borax flux recipee to mainly copper/little AuAg ingot...if done with oxidizing flux and in non-graphite crucible, good portion of tin and lead will be removed to the slag too. and you go from there, with "clean" metal, either dissolution with AR or electrorefining, if ingot is sufficiently pure copper.


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## AndrewSuperD (Dec 7, 2021)

Hmpf!!! Well, tonight I checked on the solution. I boiled the lot in AR again and the whole mess is now brown and testing negative for gold. The bit of yellow liquid I decanted from the exact same beaker (before making fresh AR an boiling) tested and is still testing positive for gold with Stannous Chloride. I imagine the gold could have cemented onto something in suspension but what? Or it just wasn't really there. I may be ready to move on from this batch :\


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