All,
Recently I have had many questions about dissolved gold in spent AP solutions. I have also had many questions about what to do with old AP solutions. For this reason I have decided to summarize information that I have posted in the past into this single post.
Here is what I've stated in the past about left over AP solutions:
The black powder must be removed / filtered out before adding any iron to the mix. Once iron is added the copper will precipitate and the solution is no longer usable.
To get gold out keep dissolving copper based items (fingers, some non-magnetic types of cpus and pins) until the color of the solution turns nearly black. Once the AP solution is black there will be no gold dissolved in the solution. At this point let it settle 24 hours and filter out the fine black powder (gold + contamination) Refine this material with HCl-Cl to get your gold back.
After the gold has gone into solution don't expect to see gold flakes any longer, only black powder as the copper saturates the solution. Gray or off white powder in the bottom of the bucket is a sign of copper I chloride saturation.
After you remove the black powder from the solution and confirm saturation with a few drops of tap water (a white cloud forming indicates copper I saturation), you should decide how much of the saturated solution you want to save for recycling in the next batch. A final test with stannous will confirm no gold is present.
Pour off the solution you don't need into a separate bucket and add in a large surface area piece of steel (zinc plated is fine) to push the copper out of the solution. Scrape the copper off of the steel plate periodically to expose more bare metal to the solution.
Here's a photo of me harvesting copper from one of my spent AP buckets today:
Once all the copper is out, remove the steel plate.
The solution is now a greenish rusty brown.
Here's another photo:
Add lime ($4.50 for forty pounds at WalMart) dissolved in water until it turns clear and test pH 7 to litmus paper. The solution foams vigorously as the lime water is added. The neutralized salt water can now be disposed of without worries. The red brown iron compounds in the sediment can be dried out and sent to the local dump or melted with carbon to form crude iron.
Clean up the copper with several dilute (5%) HCl rinses and finally with two or three water rinses. Let the copper powder dry under a heated vacuum or with forced heat (direct sun works fine) to prevent green copper carbonates or brown/black copper oxides from forming on it's surface from air exposure. Store powder in an air tight container.
Here's what properly washed and dried copper powder looks like:
The remaining solution (the part you did not add the steel to) should have air bubbled through it until it turns emerald green again. If it's color doesn't lighten after 24 hours of bubbling add a cup of ~32% HCl and 1/2 cup of 3% peroxide. It is now ready for reuse on your next batch of fingers.
You should study the copper chloride document on my website in the documents section.
All of the above information is already posted on the forum in various older posts.
Steve
Recently I have had many questions about dissolved gold in spent AP solutions. I have also had many questions about what to do with old AP solutions. For this reason I have decided to summarize information that I have posted in the past into this single post.
Here is what I've stated in the past about left over AP solutions:
The black powder must be removed / filtered out before adding any iron to the mix. Once iron is added the copper will precipitate and the solution is no longer usable.
To get gold out keep dissolving copper based items (fingers, some non-magnetic types of cpus and pins) until the color of the solution turns nearly black. Once the AP solution is black there will be no gold dissolved in the solution. At this point let it settle 24 hours and filter out the fine black powder (gold + contamination) Refine this material with HCl-Cl to get your gold back.
After the gold has gone into solution don't expect to see gold flakes any longer, only black powder as the copper saturates the solution. Gray or off white powder in the bottom of the bucket is a sign of copper I chloride saturation.
After you remove the black powder from the solution and confirm saturation with a few drops of tap water (a white cloud forming indicates copper I saturation), you should decide how much of the saturated solution you want to save for recycling in the next batch. A final test with stannous will confirm no gold is present.
Pour off the solution you don't need into a separate bucket and add in a large surface area piece of steel (zinc plated is fine) to push the copper out of the solution. Scrape the copper off of the steel plate periodically to expose more bare metal to the solution.
Here's a photo of me harvesting copper from one of my spent AP buckets today:
Once all the copper is out, remove the steel plate.
The solution is now a greenish rusty brown.
Here's another photo:
Add lime ($4.50 for forty pounds at WalMart) dissolved in water until it turns clear and test pH 7 to litmus paper. The solution foams vigorously as the lime water is added. The neutralized salt water can now be disposed of without worries. The red brown iron compounds in the sediment can be dried out and sent to the local dump or melted with carbon to form crude iron.
Clean up the copper with several dilute (5%) HCl rinses and finally with two or three water rinses. Let the copper powder dry under a heated vacuum or with forced heat (direct sun works fine) to prevent green copper carbonates or brown/black copper oxides from forming on it's surface from air exposure. Store powder in an air tight container.
Here's what properly washed and dried copper powder looks like:
The remaining solution (the part you did not add the steel to) should have air bubbled through it until it turns emerald green again. If it's color doesn't lighten after 24 hours of bubbling add a cup of ~32% HCl and 1/2 cup of 3% peroxide. It is now ready for reuse on your next batch of fingers.
You should study the copper chloride document on my website in the documents section.
All of the above information is already posted on the forum in various older posts.
Steve
