AP method help needed

[bswartzwelder]

I made an AP rig some time ago. Used a 5 gallon bucket for the outer bucket and a smaller bucket for the inner bucket. Inner bucket had hundreds of holes drilled into the sides near the bottom and on the bottom. Next, I tied some plastic aquarium airline tubing to the bottom. Sealed the ends of the tubing and punched a bunch of holes in the tubing with a hot paper clip. I had a nylon rope tied through two holes in the top of the inner bucket to act as a handle for lowering/lifting the inner bucket.

Laid the inner bucket on its side and stacked a bunch of circuit boards into the bucket. I also had a bunch of smaller circuit boards, so I alternated the stack with a large one, then a small one. The idea was to prevent the boards from nesting together with smaller boards serving as spacers. None of the boards ever had any components mounted on them so there was no danger of contamination with solder.

Poured 1 gallon of Hydrochloric acid (31.45%) into the outer bucket and added 2 quarts of 3% hydrogen peroxide. Connected the hose ends to an aquarium air pump and gently lowered the inner bucket into the outer bucket. One week later I found some trimmed fingers and added them to the inner bucket. They weren't completely covered by the AP solution, so I added a half gallon more HCl and another quart of peroxide. Continue the aeration for another week and a half.

Today, wearing rubber gloves, I lifed the inner bucket out of the outer bucket. The nylon rope tied to the inner bucket has seemingly vanished. The AP solution has turned a dark emerald green. I rinsed the inner bucket and its contents in another 5 gallon bucket filled with water. Some of the trimmed finger contacts still have contacts on them. It seems the AP did not even clean off the loose fingers on the top. I haven't checked the stacked boards underneath as something came up and put a stop to my hobby for the time being. I did purchase some gold chloride. Using two stirring rods, I put a drop of gold chloride on a paper towel and a drop of the AP solution on the towel several inches away. Next, I added a drop of Stannus Chloride to each spot on the towel. The yellow spot with the gold chloride solution turned dark brown to purple as expected. The yellow AP spot turned clear. It appears (correctly so) that there is no gold in the AP solution. Why didn't the AP solution dissolve the trimmed finger contact foils? I will check the other circuit boards in a day or two and let you know what happened to the other circuit boards.

 

[maynman1751]

AP is not supposed to dissolve the foils but simply remove them from the boards. Leave it another week and stir it occasionally to circulate the liquid. Are you in a heated or cold area? Mild heat really helps this process.

 

[Pantherlikher]

Sounds like you are doing everything right as instructed. 3 quarts of 3% hydrogen peroxide sounds like too much and disolves gold. You tested and came up no so that's good. The AP will disolve unwanted metals allowing gold to settle, on everything.
My thought would be to rinse well all pieces, using a tooth brush to wipe anything loose and put anything with visible gold back into the bucket for further processing.
AP can and will disolve gold but will also drop it back out as copper is being removed. So save all material that accumulates as that should be your gold. ie: black stuff.
If my learning ability serves me well, great but please correct anything I am wrong on or forgot to add.
BS.
I try to write the process and have it all there and correct before even stepping into a pile of BS.... (Pun intended)

 

[butcher]

I had a nylon rope tied through two holes in the top of the inner bucket to act as a handle for lowering/lifting the inner bucket.
. The nylon rope tied to the inner bucket has seemingly vanished.

The HCl may have dissolved the rope into solution.

Stacked a bunch of circuit boards into the bucket. I also had a bunch of smaller circuit boards, None of the boards ever had any components mounted on them so there was no danger of contamination with solder.

Circuit boards can have traces under solder mask or in between layers of fiberglass multiplayer circuit boards, the acids if contain dissolved gold can plate out dissolved gold onto the copper under the solder mask, or plate gold to remaining copper between the layers of fiber glass, whole boards are not a good idea, and could lead to lose of values, if the boards had solder (tin on these boards or components, the problems would multiply (since you did not have solder or components you will not have those problems now)

Poured 1 gallon of Hydrochloric acid (31.45%) into the outer bucket and added 2 quarts of 3% hydrogen peroxide.
With a lot of oxidizer in solution the gold can go into solution and plate back out onto remaining copper as black powder.

The AP solution has turned a dark emerald green

Some of the trimmed finger contacts still have contacts on them.


Not all of the copper is dissolved and your solution needs refreshed or rejuvenated to dissolve more copper.
Color of your solution Indicating solution is a mix of copper II chloride and copper I chloride, needing more air or oxygen at this point, if white powders may need a little more HCl
At this point the solution is not actively dissolving more copper, and is loaded with copper ions, the solution needs rejuvenating to finish dissolving the copper, you have left. Until all of the copper from the boards are dissolved the foils may not release, or if gold has plated back to the copper the gold will stay with that undissolved copper, this would be a problem if that gold was now under the solder mask or inside layers of a circuit board where acid will have a hard time reaching, this gold plating this may now make it hard for the acid to get to the copper under these covers, also bubbles trying to escape from the space under the solder mask or from space between fiberglass layers can prevent new solution, from entering this space to dissolve away the copper.

 

[bswartzwelder]

Things are not as bad as I thought. Yesterday I used a toothbrush on some of the finger contact boards. Most of the foils came right off. The circuit boards in the bucket are a bit confusing to say the least. On one type of board, EVERYTHING is gone. I assume the copper dissolved and the foils fell off. There are a lot of foils in the rinse water. The other style of board has the appearance that some of the copper may still be present. Because of the dark color of the boards, it is hard to tell if there is anything left on the board. Also, on some of the finger contact boards, it appears there may still be some copper traces still there. I have ordered the large filter papers and once they get here I'll filter all the solutions and come up with a yield.

This was all done outside here in Southern Marylandm so it was pretty cold at night. I still need to brush of all the boards to see what they look like. I will be cutting up the smaller boards into thin strips and using the strips to separate the larger boards. At any rate, what I once thought was a total bust has actually turned out to be plesantly surprising.

After filtering out the foils, I'll give them several HCl baths then try my hand at HCl/Chlorox. The videos, books, and all the posts have really been most helpful and have restored my confidence since the Shor fiasco. Thank you to all.

 

[Pantherlikher]

You still sounded a bit unsure you got everything off.
My thinking when I venture into doing this, will be to run the batch and drain off the solution and rinse everything and brush. Then when I'm ready to do another batch, do the 1st batch for a day or so with fresh solution. It would ease my doubts about getting it all and start the process for the next batch.

Just save the boards untill you are ready for another go at it.
BS.

 

[qst42know]

The nylon rope tied to the inner bucket has seemingly vanished.

If you need a replacement handle, the polyester banding for pallets I have exposed to acids hold up well. It doesn't take a knot worth a darn though you have to melt weld it.

 

[bswartzwelder]

Thank you Pantherlikher. The boards all look like the gold is gone, but there are several different colors where there used to be gold. I will try to post some pictures in the next couple of days.

Someone wrote to rejuvenate the solution. What is the best method? Bubbling more air into it, adding H2O2, adding water, or adding more HCl? I'm really thinking about getting rid of it and starting with another fresh batch. If the answer is adding more water, I will soon have more than a bucketful of the stuff. Also, when I am ready to dispose of the used solution, I would think the best way to do it would be to get rid of as many of the heavy metals as possible. I would think this would entail cementing things out with an out aluminum can or some scrap copper wire. The more I look at it, the more I am convinced I am doing things right and just want to continue in that direction. One of my sons will be visiting before Christmas and I would like to take some Hydrochloric acid/bleach solution with foils dissolved in it and show him how to precipitate the gold with a SMB/water solution.

 

[maynman1751]

No need to throw away. AP will last a long time. All you need to do is bubble air through it or just leave it set uncovered and it will draw oxygen from the air. AP is reusable until it gets saturated with copper (brown). Keep it to do your next batch with. I just let mine set for a week or so, add a little HCl and add a new batch of fingers.
Something else you can do is make a fresh batch and add some of the used, green solution to kick start the reaction.

 

[Geo]

No need to throw away. AP will last a long time. All you need to do is bubble air through it or just leave it set uncovered and it will draw oxygen from the air. AP is reusable until it gets saturated with copper (brown). Keep it to do your next batch with. I just let mine set for a week or so, add a little HCl and add a new batch of fingers.
Something else you can do is make a fresh batch and add some of the used, green solution to kick start the reaction.

actually, excess copper will precipitate out as copper(I)chloride. a white granular powder that is mostly insoluble in water but highly soluble in hcl. as the saturation of copper exceeds the solutions ability to hold the copper in it will precipitate out as this white square "sand". the solution has the ability to digest more copper than it can hold due to the over saturation of oxygen from the air supply.cut off the air and the excess copper will precipitate out.

what will make the copper chloride leach ineffective is a saturation of other base metals like iron,tin,cobalt,nickel.the tin will precipitate out with added oxygen as tin oxide.the other contaminants will build until the solution is ineffective.

 

[Pantherlikher]

Someone wrote to rejuvenate the solution. What is the best method? Bubbling more air into it, adding H2O2, adding water, or adding more HCl? I'm really thinking about getting rid of it and starting with another fresh batch. If the answer is adding more water, I will soon have more than a bucketful of the stuff. Also, when I am ready to dispose of the used solution, I would think the best way to do it would be to get rid of as many of the heavy metals as possible. I would think this would entail cementing things out with an out aluminum can or some scrap copper wire. The more I look at it, the more I am convinced I am doing things right and just want to continue in that direction. One of my sons will be visiting before Christmas and I would like to take some Hydrochloric acid/bleach solution with foils dissolved in it and show him how to precipitate the gold with a SMB/water solution.

Ok. So if you pour the solution into another bucket and let it sit, it will evaporate as well as drop excess copper out there by reducing it as well as getting rid of some copper. This would be good for the next batch.
Maybe make a small batch and put a couple questionable boards in for a day or so and see if anything comes off....just to be sure...

Patience it seems is in order no matter what... While reading, go find and read about spent solution and what to do with.

You want to show your kid the Hydrochloric acid/bleach process. Also remember to show all the safety precautions involved. Like treat with the utmost respect so it doesn't bite your hand off.

Good luck and let us know and see the good results..

BS.
Wishing psycoticically emotional problem kids were as easy as all of this.

 

[Geo]

dissolving copper takes hydrogen from the solution, when you add oxygen it drives the reaction forward but when oxygen is dissolved it releases chlorine.by using oxygen to enhance the process, you are losing both hydrogen and chlorine. both of these are gasses and would (on their own) gas off and leave only water albeit it would take awhile to do. to keep the solution rejuvenated, add a little fresh hcl periodically as the solution loses volume due to evaporation.

 

[kadriver]

Things are not as bad as I thought. Yesterday I used a toothbrush on some of the finger contact boards. Most of the foils came right off.

You can also use a squart bottle set on "solid stream" to force the foils to come off the boards as well. Just squirt a forceful stream right at the foils that are adhered to the boards. They will usually come right off.

kadriver