LCD screen scrap

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landofme

New member
Joined
Nov 2, 2017
Messages
2
Hello friends
i used many lcd screen scrap . i cut from the fingers and didnt use the circuit elements. i just used fingers.
i put them AR and boiled up. (850 mg HCL and 250 mg Nitric Acid ) 1 hour later my scrap totaly clean. Everting disolved over it then i filtered it. İt was very dark green solution.
IMG_20201218_122724.jpg

After filtering my solution had became 1600 mg with water. Then I boiled it on low heat 5 hour until my solution become 1000 mg . i added some URE for see to reaction of nitric acid and i saw reaction. i added one food spoon ure to the solution and go on to add until stay no reaction. totaly i added 2 spoon ure. After being sure no nitric in the solution , i added dry SMB maybe 10 spoon. it was always giving brown reaction when i added smb. İ had tought that brown was gold :D . After 10 spoon smb i cut the give.( but if i gave more smb it would be more reaction, i m sure about that. juts i tought that even 10 spoon much.)

Videoframe_20201217_001955_com.huawei.himovie.overseas.jpg

After added smb my solution become dark browm. i thought that gold will down a few hours later . But 2 hour later there was many cyrstals.
Just i wanna ask
1- are gold inside of cyrstal or stil inside of solution?
2-if inside of solution. how can i precipita it.
tnx for your helping

IMG_20201217_115031.jpg

IMG_20201217_115023.jpg
IMG_20201217_115020.jpg
 
There should be little gold at the end of processing 40 of these strips. The thing is it is so little it probably ended up stuck on other still undissolved metal. Like in your picture you can see black IC still attached to the board with undissolved legs or connectors.

When you go AR way treating this kind of material you must depopulate boards to remove as much of metal present there as possible otherwise you end up spending more money wasting acid on base metals chasing very little gold.

I would leave it as it is and write it off as a learning expense. While I do not have any data on value of these I do have plenty of them but the plating on them is so thin and many times covered by some remnants of glue and foil where they were attached to screen. I will only think about processing them with cyanide, ferrocyanide or iodine and even this only after gold price multiply few more times. At the moment AR processing of depopulated boards will probably not cover the cost of doing so.
 
He ONLY used the (close?) cut fingers, no components… the last picture is to illustrate that.
He should have gone for AP instead of AR...
Have you tried a stannous test?

As others have repeated many times: when in doubt, cement it out? if not allready cemented out on the sides of the copper traces at the edges of the laquer coating. Gold could be trapped under this lacquer/epoxy edge?

If there is anything to be cemented that will be visible. So little gold can get lost quickly.

Martijn.
 
Martijn said:
He ONLY used the (close?) cut fingers, no components… the last picture is to illustrate that.
He should have gone for AP instead of AR...
Have you tried a stannous test?

As others have repeated many times: when in doubt, cement it out? if not allready cemented out on the sides of the copper traces at the edges of the laquer coating. Gold could be trapped under this lacquer/epoxy edge?

If there is anything to be cemented that will be visible. So little gold can get lost quickly.

Martijn.

Have a look at his picture which show processed boards. Some of them show backside of processed "fingers" and there you can see IC's, connectors... With undissolved metal so gold may be pretty much cemented on these.
 
There is visual metal left on the processed boards, so plenty of opportunity to cement the little gold that you had at the beginning.

The numbers given is also erroneous, but I guess that "mg" isn't milligram but you mean milliliter, ml. I'll assume that's a typo.

We want to see a stannous test.

My guess is that the white crystals are just copper chloride. Pour off the liquid and check if the crystals dissolve in a bit of HCl.

If you add enough SMB to a heavy copper chloride solution it will reduce Cu2+ to Cu+ and first turn the solution dark brown and in the extreme precipitate white CuCl crystals when the concentration gets too high.

Göran
 
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