Please help! Gold/silver not precipitating

lvicknair

Member
Joined
Dec 4, 2020
Messages
5
First off, this is my first attempt to recover gold/silver from e-waste and even with hours upon hours of research I have already realized a few of my mistakes and hoping I can make some recovery from them. My issue is that I can not get any gold or silver to precipitate.

My process was putting computer boards into 1 part nitric and 1 part TAP water, not distilled (I know this was a mistake). After letting the metals dissolve completely and filtering out the gold flakes and trash from the solution, I tried to precipitate the silver from the nitric acid mix using non-iodized salt. I did not cement with copper but can try that if you think it will help.

With the gold foils I put in aqua regia but added nitric acid in small increments until all the gold foils dissolved. I then added SMB to solution until it stopped reacting and added a few spoonfulls afterwards but still no gold powder appeared at the bottom.

Another factor to keep in mind is I did this outside with the acids at points being exposed to cold temperatures. This also caused glass like crystals to form that I still have no idea what they are and could not find it anywhere doing my own research.

Any help or advice would be greatly appreciated!
 

lvicknair

Member
Joined
Dec 4, 2020
Messages
5
Forgot to mention that I filtered the AR again after dissolving the foils and before adding SMB
 

butcher

Moderator
Staff member
Moderator
Joined
Jan 6, 2008
Messages
9,905
Location
Pacific NW
How do you know you had these metals in solution?
Would you recognize these metals if they did precipitate?
How many grams or ounces or pounds of these metals such as silver or gold did you have in solution?
How do you know that they did not cement out of the original leaching process and that the solutions may have contained very little er non of these precious metal ions?

Leaching Trash with solutions may only hold trash in the solutions...

Some metals from electronic scrap may resist nitric treatment yet the metals may still be able to cement gold from the next leach...

Without knowing details it is hard to form answers.
 

Lino1406

Well-known member
Joined
Nov 1, 2007
Messages
2,117
Location
Israel
Assuming SMB = really SMB, (it should have SO2 smell in action), the gold (in minor amounts) should be found in the glasslike crystals
 

lvicknair

Member
Joined
Dec 4, 2020
Messages
5
Thanks for the speedy reply. Again, I am still learning everything and do not mind reading and doing my own research, but am having trouble finding sources to my questions.

Q-How do you know you had these metals in solution?
A-I only know the gold was in solution due to the amount of flakes I had before using the AR. I plan on doing a stannous test this weekend when I have free time. I have tried looking up how to test if silver is in a solution but can only find test that are performed on solid metals to check if it is real silver.

Q-Would you recognize these metals if they did precipitate?
A- Per the videos/reading I have seen, gold should form a black or brown powder like substance that has to be filtered off and dried. I did not get any powder like substance at the bottom of the beaker at all. Just the clear glass like rods that are anywhere from 1-3 inches long. It's clear I have made some mistakes, just trying to learn from them at this point.
As for the silver, I had no reaction at all when adding the salt and no formation at the bottom. Is it possible that the left over nitric in solution would dissolve the precipitation? I plan on adding copper to the solution this weekend to see if I can cement the silver out. But also want to know if I am suppose to get rid of excess nitric before trying to precipitate. If you know of any links/literature that are accurate to educate myself I would be more than happy doing my own reading.

Q-How many grams or ounces or pounds of these metals such as silver or gold did you have in solution?
A- I had about 10 pounds of scrap boards that were supposedly from an old satellite. I put the entire boards into nitric which did have the plastic on them and not sure how to weigh the amount of metals before that. Is there a way of doing this? Or is there a way to remove metals from the trash before the nitric?

Q-How do you know that they did not cement out of the original leaching process and that the solutions may have contained very little er non of these precious metal ions?
A- I still have the trash leached from the original nitric and can tell it is a lot of plastic with a silver powder/sludge like substance that I assumed was due to me using tap water instead of distilled due to the research I have done about using tap water said the minerals in it would cause a sludge like substance to form. Is it possible that this sludge is where my silver is at? If so, would I have to put it in a nitric bath again or what is the best way to get it out?

Leaching Trash with solutions may only hold trash in the solutions...
Is there a way to remove trash like plastic prior to the nitric?

As for the SMB, the container does say Sodium metabisulfite, so can only assume it is correct SMB.
 

Martijn

Well-known member
Joined
Aug 3, 2014
Messages
668
Location
Netherlands, Zeeland
Ivicknair, welcome to the forum, judging by the comments you leave: you really need to read a lot more before proceeding any further!! Don't hurt or kill yourself with inexperience. And starting with a truckload of material and dumping another truckload of acid on it is not the best learning approach. Mistakes will create bigger dangers, more toxic waste, more deadly gases, and more of a mess to clean up once done wrong!. So start small, and get some experience first before trying to get gold out of a trash pile.

Forget You-tube until you know what you are talking about. A lot of them are life threatening; not pointing out the risks or the finer (most important) details left out.

Some links to educate yourself:
Dealing with waste:
Dealing with Waste

Guided tour to the forum:
Welcome to all Newbies
A list of very usefull links put together by Lazersteve.

C.M. Hoke's book: (our bible)
look in Frugalrefiners signature or in this post:
Screen Readable Copy of Hoke's Book

The left over sludge in the bottom of the first tapwater / nitric mix will most likely contain: metastannic acid AKA tin paste, since you did not remove solder before going to Nitric. Maybe traces of silver assuming there was silver on the PCB's.
Silver chloride is insoluble in hot water, HCL and Nitric. Only very slightly soluble in AR.
Lead Chloride will dissolve when heated. Silver chloride will not. When cold PbCl can form glasslike- white needle Crystals.
gray sludge: tinpaste, white sludge: lead chloride or silver chloride, the latter will discolor in the sunlight. the first is soluble in hot water.

Separating components and PCB's before recovering any pm's is important. Trash in > Trash out!
There is no machine or process where you can trow in garbage and expect shiny gold on the other end. it will take some preparation> work.

If only a little bit of gold was in solution, the yellow color can disappear when adding SMB, and it will take the gold some time to clump together and even become visible as a fine layer on the bottom.
A stannous test is the best way to know what in solution.

To test if any silver is in solution you could put a bit in a beaker and add table salt or a bit of HCL to see if any AgCL forms, not excpecting that to happen, since you used tap water, and the littlbe bit of silver that may have been there, is already converted to AgCl and will be in said sludge.

The silver is not worth that much to be worried about, i.m.o.
Separating silver from tinpaste, could prove more expensive than the the actual value of the silver there is.
Maybe incinerating and leaching in HCL will take care of the tin paste.

Martijn.
 

lvicknair

Member
Joined
Dec 4, 2020
Messages
5
Really, thank you so much for everyone's help and the links provided. Will do some more research and my next attempt will be with simple gold plated pins so as to eliminate some of the waste. This forum is amazing and full of some helpful people.
 

Martijn

Well-known member
Joined
Aug 3, 2014
Messages
668
Location
Netherlands, Zeeland
Great! have fun studying.
Before you attempt the next thing: describe your intended steps and have a plan. Present your plan here and wait for advice.
I read for a couple of years before feeling confident enough proceeding with my very own 'that looks too easy You-tube mess'.. as a hobby.
Keep gathering and separating e-waste-'ore' as you study. If you decide not to recover it, E-bay will provide some refunds. Shiny stuff sells good.

One thing that did turn out very good for me by jumping in head first and way too fast:
I bought a bunch of stuff including 5 liters of HNO3 the first week in 2014, not knowing it would be nearly impossible to obtain a few years later..! Lucky me.. 8)

Martijn.
 

Latest posts

Top