Gold Stratification?

[Meh1]

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

 

[Geo]

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

 

[Meh1]

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?

 

[kronix]

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

 

[Geo]

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.

 

[NobleMetalWorks]

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]

 

[Meh1]

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

 

[butcher]

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

 

[Meh1]

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

 

[patnor1011]

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.

 

[Meh1]

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.

 

[patnor1011]

Incinerate.

 

[Meh1]

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.

 

[bswartzwelder]

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.

 

[Meh1]

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!

 

[AndrewSuperD]

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?

 

[butcher]

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.

 

[AndrewSuperD]

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.

 

[orvi]

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

 

[butcher]

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