Solution has turned black

[RajunCajun84]

Relocated my set-up to a friend's house due to work area restrictions. While away he thought he would be helpful... (Deep breath) Here we go.

Finders and some pins in 1 container, different sorts of cpu's in another. All drowned with HCL and h2o2. When I asked how much of each was used I got a dear in a headlight stare... I now have 2 containers of components in a solid black concoction. I know gold is in there somewhere, please help. How can i recover my values from this?

 

[lazersteve]

If the AP is dark black (or chocolate brown) it is very likely saturated with copper and copper I chloride and contains no dissolved gold. A simple test is to spray in some water. If you see a white cloud the solution is trump tight with copper and won't hold any dissolved gold. A stannous test will confirm this.

Depending on how much scrap you started with the gold is likely in the bottom of the buckets.

Siphon or gently pour off the liquid until you see gold flakes or powder in both buckets. Once you see the gold, stop pouring. Combine the two gold laden solutions rinsing one bucket into the other. Add more HCl to thin them out. Now that you have a more fluid solution let the liquid settle again and siphon. Repeat until the HCl is no longer discolored by the solution. With each cycle you should see more and more gold and have less and less solution. The rinse solution can be used as the HCl portion in the in the next batch of AP.

Finish up with a few good water washes of the gold powder/foils until clear, then dissolve them with HCl-Cl.

Steve

 

[RajunCajun84]

Solution stays black,nothing settling on the bottom. I will post more as time goes on. I was told I could add some costic to balance the ph, and knock EVERYTHING out of solution. Input?

 

[glorycloud]

Could it be that there was not much gold to start with? How much material
was "drowned" to start with? It takes a pound of decent fingers to get 2 - 2.5 grams
of gold for example. If you only have a few ounces of fingers / pins, you won't
have much gold to retrieve.

 

[lazersteve]

Here's a recent post that you should read:

Spent AP solutions

As for the question as to how much AP to use, the answer is as much as is required to dissolve all the copper. You can start with an arbitrary amount then, since the process is regenerative, all you have to do is to keep rejuvenating the CuCl2 to keep it active.

Rejuvenation is easily accomplished by bubbling air through the solution via:

2CuCl (copper I chloride) + 2HCl + 1/2O2 --> 2CuCl2 (copper II chloride) +H2O

or Chlorination via:

2CuCl + Cl2 --> 2CuCl2

or Peroxide via:

2CuCl +H2O2 +2 HCl --> 2CuCl2 + 2H2O

The copper I chloride is insoluble in water and dilute acids, but soluble in strong acid, so the acid levels must be kept high enough to keep the reaction moving to the right.

Theoretically computed, for regenerating 1 kg of copper, 1.36 liters of 35 percent hydrogen peroxide and 3.1 liters of 32 percent HCl are required. On the basis of these quantities, the dosing ratio of H2O2 : H2O : HCl is 1 : 4.2 : 2.3.

It should be taken into account, however, that these values are theoretically computed ones and that there are losses caused by sucking off and the side reactions.

Everyone interested in AP should study all the literature referenced above for a solid understanding of how to use AP.

Steve

 

[Anonymous]

Here's a recent post that you should read:

[
The copper I chloride is insoluble in water and dilute acids, but soluble in strong acid, so the acid levels must be kept high enough to keep the reaction moving to the right.


Steve

Heres a little note about what I have been doing with the insoluble copper chloride. Since it is really excess copper that I no longer need I have been filtering it out. My belief is that since it has formed crystals they should be pretty darn pure. One report I read stated that it could be used to precipate gold, I thaught about that, but decided not to go there. When I filter out the copper I chloride it often contains little bits of foils mixed in. After all of original solution has drain off, I seperate the foils with an HCL rinse leaving the gold foils in the filter and HCL with copper chloride solution which I add the iron as usuall but the copper that results is really clean and I have been able to get #2 price for it.

Jim