reocery of gold from scrap CPU or PCB

[ecosage]

I have stripped all gold from the scrap CPU with superstrip100 and potassium cyanide. But the electroplating process is failed to recover
gold. I got alloy (more like cupper come out ). Can anyone advice
how to rectify my process. I guess the etching solution wash everything
including copper, silver from the contactor of CPU.

P.S. I used a DC conveter to provide a DC system.

Pls help.

 

[nickvc]

I feel you may be on your own on this one, most members don't have access to cyanide and advice is usually only given to those who have a good knowledge of the inherent dangers if using it, while it does the job of removing the gold really well you only make one mistake with it....and it's you last!
My advice for what it's worth is to see how other members of the forum treat plated scrap such as fingers,pins and CPUs. Use the search function and read the forum handbooks and visit lazersteves site where many processes are shown on video. A real must is C.M.Hokes book available as a free download of many members signature line.
I wish you luck but unless you really know what your about lose the idea of using cyanide.

 

[ecosage]

Hi nickvc,
Many thanks for your advice. Could you more directly point out what is that "LAST".

 

[jimdoc]

I think he was saying; one mistake and its your last.

Jim

 

[ecosage]

yes, please DO tell me what is the LAST Mistake, how to recover the gold instead of alloy. I have waste a lot of time........deadline is coming for
my project. I dont want to use chemical method. I have no time to go back to the starting point or try other method.

 

[martyn111]

yes, please DO tell me what is the LAST Mistake, how to recover the gold instead of alloy. I have waste a lot of time........deadline is coming for
my project. I dont want to use chemical method. I have no time to go back to the starting point or try other method.

The last mistake is the one that kills you. Cyanide is a dangerous chemical, if you make a mistake in handling it, that mistake could be your last mistake is what nick was implying

 

[Harold_V]

Some of the cyanide based stripping preparations make recovery of the values from the solution very difficult, if not impossible. Obviously, there's a way to accomplish the task, but it may be proprietary information, not available to the public at large. GSP has written about this problem in the past.

I would expect that zinc flour (dust) will extract the values. It works perfectly well with cyanide. A lot depends on the buffers that have been added to the specific preparation you have used.

Have you tried zinc? If so, was there a small excess of cyanide present?

Harold

 

[ecosage]

Thanks Harold,

sorry I didnt catch your point. I did know some of the gold extraction (chemical means) using zinc as displacement. However, I prefer to use electrodeposition method because it seems to be very effective (reported by most of books or articles). of course, i am in a very difficult suitation that
alloy comes out instead of pure gold. The echtant consists of copper (sure!)
silver (I guess coz i see silverish material at the cathode) and gold.

My question is very simple. Can i get the pure gold using existing cell?

 

[Harold_V]

Thanks Harold,

sorry I didnt catch your point. I did know some of the gold extraction (chemical means) using zinc as displacement. However, I prefer to use electrodeposition method because it seems to be very effective (reported by most of books or articles). of course, i am in a very difficult suitation that
alloy comes out instead of pure gold. The echtant consists of copper (sure!)
silver (I guess coz i see silverish material at the cathode) and gold.

My question is very simple. Can i get the pure gold using existing cell?

No!

When you recover from a cyanide solution, it isn't selective. A gold chloride cell can be (and generally is so long as you keep contaminants to a minimum).

You may well be recovering some of the gold now, along with the other elements. Hard to say from my vantage point, where I can't see what's happening.

What you prefer may not have anything to do with reality. If you make decisions based on what you want instead of what is known to work, you may be in for some unhappy experiences.

I'm not suggesting that you should use zinc, but if you're not achieving your desired goal, zinc is a damned good solution. It's fast, easy and will recover gold and silver to the point where it's difficult to detect in solution. I dare say that isn't going to happen with an electrolytic extraction. Zinc may be the solution to your problem, like it, or not. In any case, you will NOT recover pure gold. If you could, it would (possibly) be used in the refining process. It isn't.

Harold

 

[ecosage]

Dear all,

Thanks alot your valuable input and advice. I accept my failure. Now, I turn
to zinc displacement method. I will still use strip100 + potassium cyanide
as etching solution to stripp gold from scrap. Then i will use zinc displacement method to catch the gold. Could you pls advice the detail procedure that I need to follow. Of course, i will search the method online
. However, should you have the experence on hand, pls do help me coz
i am running out of time.

thanks alot.

P.S. pls also advice any safety precaution i got to be taken when using zinc method.

 

[Harold_V]

A lack of dissolved oxygen in solution is suggested, but I never worried about that when I used zinc. It's cheap enough to use that I figured an excess would manage the oxygen.

For me, the process was very simple. I used a 20 gallon Nalgene vessel, which I would fill nearly to the top (about 16 gallons of solution). Using an ounce of zinc for every ounce of value I expected to recover, I'd stir the solution until it was spinning well, then I'd introduce the pre-weighed powdered zinc to the solution. Conversion was virtually instantaneous---you could see the zinc turn brown, which was the gold replacing the zinc, which goes in to solution. I'd allow time for the solids to settle, then siphon off the solution to a secondary container, where the operation was repeated, only this time with just a small amount of zinc, to assure that I had removed all values. Simple.

In your case, you may wish to do a little more work on the electrical cell. I am of the opinion that you are recovering gold along with base metals, which is going to happen with zinc as well. Process a small amount by dissolving in nitric, to see what remains. I expect you'll discover you have gold, with silver and copper in solution.

Back to the solution (from your cell), so long as you recycle the same solution over and over, that you make a complete recovery of values from each iteration doesn't matter---it remains for the next round----so you can use your method except for cleanup, at which time there is likely a benefit in using zinc. You may wish to give that some thought.

If you choose to do some testing on the recovered material from the electrical cell, rinse the material well before introducing (dilute) nitric, and work in a fume hood to insure you avoid hydrocyanic acid exposure. It kills by binding red blood cells, making it impossible for them to carry oxygen, so you suffocate. A quiet and painless death, but dead none the less.

How about a report after you've conducted some experiments?

Harold

edit:
I am not familiar with strip 100. It may create a solution from which gold may not be recovered with zinc. That was my point in making mention of the information posted by GSP. I'd suggest you perform a test before jumping in.

 

[goldsilverpro]

On the internet, I found that Superstrip100 contains a thallium compound and, I would guess, lead acetate. These are added to lower the rate of attack on the base metals, primarily copper. I don't have specific experience with SS100, but I have used TechniStrip AU, a very similar product (I think) made by Technic. It was virtually impossible to precipitate the gold from the TS AU using zinc because of the presence of the thallium and lead. Technic sold another product (which I think is nothing but sucrose = sugar) that supposedly could be added to the pregnant TS AU solution to allow the gold to be plated out but this didn't work well either. We had about 1000 gallons of pregnant solution and ended up using a dangerous and very involved method with sodium hydrosulfite. On this link, there is a method of using sodium hydrosulfite to get the gold by Till_Eulenspiegel.
http://www.sciencemadness.org/talk/viewthread.php?tid=5700#pid80768

The moral of this story is to avoid most types of commercial strippers if you want to easily get all the gold out. These products are designed for platers to strip faulty plating, without damaging the parts, so the parts can be re-plated. The platers usually ship the pregnant gold stripper back to the manufacturer for refining.

If you look, there are most probably brownish flakes in the dry SS100. This material is m-NBSS (called meta nitro benzoic acid sodium sulfonate and various other technical names). A common name for it is Ludigol and it is used primarily in the textile industry. When combined alone with sodium or potassium cyanide in the same weight ratio (and operating conditions) you used to make up the SS100, it will strip gold readily and the solution can be easily zinced to obtain the gold. It does attack the copper a little more, but this, along with the excess zinc that was used, is easily removed from the well rinsed zinced gold sludge using weak nitric acid (UNDER THE FUME HOOD!!!).

I noticed that the SS100 manufacturer has another product called Superstrip108, which is said to contain no thallium. I would guess it only contains m-NBSS and, therefore, it may be zincable.
http://www.chestech.co.uk/processes/MetalStrippingProcesses.html

In general, no matter what stripper you use, plating is a poor way to get all the gold (or any other metal) in a batch situation. As the metal(s) plates out, the concentration of the metal(s) in solution decreases. As it decreases, the deposition efficiency decreases and part of the current splits water (and/or, performs other cathode reactions) instead of depositing metal. At some point, virtually all of the current splits water and some of the gold (or other metals) always remains in solution. Also note that, in a cyanide solution, the gold is in the form of a negative complex ion. It is repelled by the negative cathode instead of being attracted. Therefore, when the gold concentration gets low in the solution and there isn't excellent agitation to mechanically provide fresh gold ions to the cathode surface, the system will lean towards the splitting of water (or other reactions) at the cathode.