How to calculate the ratio between Hydrochloric acid to Hydrogen peroxide?

[BigiFoot]

Hi all,

I've 8 PCB's covered with gold (total weight: 703gr) and i dont know how much to use from HCI and how much from Hydrogen peroxide.
There is some formula to calculate this ratio?

Usually i use 200ml from Hydrochloric acid 32% and 150ml from Hydrogen peroxide 3%



Thanks.

 

[FrugalRefiner]

You've been using far to much peroxide. Use enough HCl to cover the scrap, then add a tiny amount of peroxide. By tiny, I mean perhaps enough to fill the cap of the peroxide bottle.

Better yet, if you have old solution you've used, add a bit of that to the HCl instead of peroxide. In fact, you can just use HCl. Oxygen from the air will dissolve into the acid and oxidize the copper. The peroxide just gets the reaction started more quickly. Using too much will dissolve some of your gold. It will eventually cement back out as a fine, black powder, so it's not lost forever, but I prefer the gold foils since they're easier to work with.

Dave

 

[BigiFoot]

Thanks alot,
yeah i have old solution, so you recommend to use 200ml Hydrochloric and just cover the boards with some old solution?

 

[goldsilverpro]

I have never used the HCl/Hydrogen Peroxide method and probably never will. To me, it's not a money-maker unless you can set it up so, by making adjustments, the same solution could be run continuously. In my mind's eye, this could involve things like analyzing the solution, crystallization, and a copper cell. I've also thought that, through control by analysis, one could continually meter in H2O2. It would react faster than air, I would think.

For most of the basic processes covered on the forum, the best early source of info is this post by lazersteve.
http://goldrefiningforum.com/phpBB3/viewtopic.php?f=60&t=562&p=4766&hilit=hydrochloric+peroxide#p4766

In it, he starts off with 2 parts muriatic and 1 part 3% hydrogen peroxide (H2O2 - a source of needed oxygen). Your 32% HCl is close to the same HCl strength as muriatic. For a long time, most people used this formula and many still do. Notice that Steve says it will dissolve gold also if you heated it. Some people started having trouble with gold dissolving along with the copper. This is not good because it turns a simple operation into a more complicated one. To combat this, some started adding no H2O2 at all and replaced the needed oxygen with air. They just, from the start, continually bubbled air through it to continually provide the necessary oxygen. This is the best way for you to do it, although the H2O2 is faster than air. The copper will just continue to dissolve until all the HCl is used up or when the copper chloride starts crystallizing. It's almost a set-it-and-forget-it thing. You will find a lot of info on this with a search.

In any case, you originally used 50 ml too much H2O2, according to Steve's formula. The one thing you want to avoid is dissolving the gold and, therefore, I would suggest using air instead of H2O2. As frugal said above, you can get things started with a TINY bit of H2O2.

I am by no means an expert in this process. If I'm wrong on anything, somebody let me know.

 

[BigiFoot]

Thanks alot for quick answer,

Maybe i use my air stone with air from my pump, and try and see the result.
if it's dont work i will kill you.. :lol:

Thanks.

 

[glorycloud]

Welcome to the forum.

"if it's dont work i will kill you" :shock:

This kind of "humor" is not at all regarded as humorous here on the forum.
Please save it for other places that you visit on the internet.

I have been reusing AP for a long time. I got rid of the "stone" for the bubbler
as it seem to just get clogged up with the gold foils that fall off in the AP solution.

 

[patnor1011]

There is not much gold in your boards. Probably enough to cover cost of HCl and H2O2.

 

[upcyclist]

I got rid of the "stone" for the bubbler as it seem to just get clogged up with the gold foils that fall off in the AP solution.

I hear that. Actually, I still have a stone in my stockpot, but I pulled the one in my 2nd stage waste processing because it got clogged with copper. I just made a loop or two through an old brass nut to weight the tubing at the end.

 

[UncleBenBen]

I got rid of the "stone" for the bubbler as it seem to just get clogged up with the gold foils that fall off in the AP solution.

I hear that. Actually, I still have a stone in my stockpot, but I pulled the one in my 2nd stage waste processing because it got clogged with copper. I just made a loop or two through an old brass nut to weight the tubing at the end.

I heated the end of the tubing with a lighter and squeezed it closed to seal it. Then poked a bunch of holes in the last 3-4 inches with a safety pin. It makes a nice screen of tiny bubbles and didn't have much problem with clogging.

 

[glorycloud]

"I heated the end of the tubing with a lighter and squeezed it closed to seal it. Then poked a bunch of holes in the last 3-4 inches with a safety pin. It makes a nice screen of tiny bubbles and didn't have much problem with clogging.

Smart solution there!

 

[Grelko]

"I heated the end of the tubing with a lighter and squeezed it closed to seal it. Then poked a bunch of holes in the last 3-4 inches with a safety pin. It makes a nice screen of tiny bubbles and didn't have much problem with clogging.

Smart solution there!

I use the non-flexible tubing, heat it, and bend to around 75-90 degree angle (don't accidently pinch it shut), so that it's bubbling near the middle bottom of my bucket. Larger bubbles, but no clogging at all yet.

It's pushed inside of the flexible tube I have running through a small hole, that's been drilled about an inch from the top of the bucket.

Does anyone happen to know if the larger or smaller bubbles would make much of a difference?

Edit - added

 

[UncleBenBen]

"I heated the end of the tubing with a lighter and squeezed it closed to seal it. Then poked a bunch of holes in the last 3-4 inches with a safety pin. It makes a nice screen of tiny bubbles and didn't have much problem with clogging.

Smart solution there!

I use the non-flexible tubing, heat it, and bend to around 75-90 degree angle (don't accidently pinch it shut), so that it's bubbling near the middle bottom of my bucket. Larger bubbles, but no clogging at all yet.

It's pushed inside of the flexible tube I have running through a small hole, that's been drilled about an inch from the top of the bucket.

Does anyone happen to know if the larger or smaller bubbles would make much of a difference?

Edit - added

Ive thought about putting a length of the soft tubing with the holes poked in it on the end of a piece of the stiff tubing to help keep it on the bottom.

I think by dividing the air into smaller bubbles it would give more surface area being exposed to the solution as opposed to the same amount of air in larger bubbles. The more contact the air has with the solution, the more O₂ can be dissolved into the leach.

That's the way my brain reasons it anyway...

 

[Grelko]

I think by dividing the air into smaller bubbles it would give more surface area being exposed to the solution as opposed to the same amount of air in larger bubbles. The more contact the air has with the solution, the more O₂ can be dissolved into the leach.

That's the way my brain reasons it anyway...

I've thought about taking the non flexible tubing, pinching the end shut, going across the bottom middle, then having it loop around the entire bottom. Place holes every half inch or so, but by the time it gets near the end of the tube, you wouldn't have any pressure to make bubbles there. Maybe if you leave the end of the tube open, there would be enough air flow?

That would basically turn the entire bottom of the bucket into a bubbler.

Edit - I think you''re right, the smaller bubbles seem like they would work better. It would give the HCL more time to gain O2, when compared to large bubbles that would get to the top of the bucket faster. Or in other words :lol: The small bubbles would slowly "fizz" to the top, where as the large bubbles would just "bloop" and be gone.

 

[FrugalRefiner]

As I recall from my days of taking care of aquariums, it's not really the bubbles that oxygenate an aquarium, it's the movement of the water at the top of the tank and the disturbance of the surface tension as the bubbles break. Tiny bubbles might be slightly more effective, but probably not by much. It's more important that the water (or in our case, the solution) be able to mix and move as the bubbles rise.

Dave

 

[anachronism]

As I recall from my days of taking care of aquariums, it's not really the bubbles that oxygenate an aquarium, it's the movement of the water at the top of the tank and the disturbance of the surface tension as the bubbles break. Tiny bubbles might be slightly more effective, but probably not by much. It's more important that the water (or in our case, the solution) be able to mix and move as the bubbles rise.

Dave

One of the best ways to oxygenate a small leach tank is to make a vortex. Exactly the same principle Dave. That and plunging liquid into it from above.

 

[goldsilverpro]

This is a typical air sparger placed in the bottom of a plating tank to produce air agitation. I have built several of them. When the air is turned on high (always from a blower, not a compressor), solution levels can raise 2"-3". The one in the drawing is made wrong, in that the holes in the pipes should be directed downward at about a 30-45 degree angle, Also, every one I've seen has 2 rows of holes in each pipe, with about a 60-90 degree angle between the 2 rows, here again, the holes are directed downward at an angle. The sparger should be raised off the bottom at least a half inch.

The one in the drawing has 2 legs. I've seen them with 1, 2, or 3 legs. A problem with all these spargers is that, since the air is directed somewhat downward, they want to raise up. In a big plating tank, say 1000 gallon, they solve the problem by pacing lead weights, coated with Plastisol, on top of the bottom pipes. With a small tank, it can be solved by using rigid plastic pipe and clamping the vertical pipe well. One could also use a a vertical pipe on each end and securing each pipe at the top. I've also used small round plastic spargers that fit into a 600ml beaker.

The one in the drawing is probably not the best arrangement for what you're doing. As far as hole diameter, pipe diameter, etc., I have no idea. I would probably design it for an aquarium air pump and use much smaller holes. Being directed toward the bottom really fills the tank with air.

I'm not saying this is a good way to go. I'm just throwing another thing into the discussion. Forget about the dimensions in the drawing and the hole spacing. It can be any shape or size. Also, you might be able to soak the pipe in hot water and semi-permanently form some pipe into a curve or circle.

 

[UncleBenBen]

This is a typical air sparger placed in the bottom of a plating tank to produce air agitation. I have built several of them. When the air is turned on high (always from a blower, not a compressor), solution levels can raise 2"-3". The one in the drawing is made wrong, in that the holes in the pipes should be directed downward at about a 30-45 degree angle, Also, everyone I've seen has 2 rows of holes in each pipe, with about a 60-90 degree angle between the 2 rows, here again, the holes are directed downward at an angle. The sparger should be raised off the bottom at least a half inch.

They one in the drawing has 2 legs. I've seen them with 1, 2, or 3 legs. A problem with these is that, since the air is directed somewhat downward, they want to raise up. In a big plating tank, say 1000 gallon, they solve the problem by pacing lead weights, coated with Plastisol, on top of the bottom pipes. With a small tank, it can be solved by using rigid plastic pipe and clamping the vertical pipe well. One could also use a a vertical pipe on each end and securing each pipe at the top. I've also used small round plastic spargers that fit into a 600ml beaker.

The one in the drawing is probably not the best arrangement for what you're doing. As far as hole diameter, pipe diameter, etc., I have no idea. I would probably design it for an aquarium air pump and use much smaller holes. Being directed toward the bottom really fills the tank with air.

I'm not saying this is a good way to go. I'm just throwing another thing into the discussion. Forget about the dimensions in the drawing and the hole spacing. It can be any shape or size. Also, you might be able to soak the pipe in hot water and semi-permanently form some pipe into a curve or circle.

That's what I had thought about doing with the air tubing, and make it into a ring to fit the bottom of a 5 gallon bucket.

Now that Dave and anachronism have cleared up why the screen of bubbles I mentioned seemed to run the leach faster by keeping the solution in motion, I have a much better idea on how to build it.

Thanks guys, y'all are awesome!!

 

[Grelko]

These are really good ideas. I may need to switch the way I have mine set up.

It's more important that the water (or in our case, the solution) be able to mix and move as the bubbles rise.

Instead of a bubbler, what if you actually mixed the solution with a pump used for a small yard fountain? It would suck up the solution and dump it back out of the top. I'm not sure how the pump would hold up against acids, but certain ones have plastic gears.

I don't mean the spray fountains, just a simple waterfall type.

If you had it too low in the bucket, it would get clogged easily, but if it was higher in the bucket, it could cycle the solution without disturbing much, if any, of the sediment at the bottom.

 

[jason_recliner]

As I recall from my days of taking care of aquariums, it's not really the bubbles that oxygenate an aquarium, it's the movement of the water at the top of the tank and the disturbance of the surface tension as the bubbles break. Tiny bubbles might be slightly more effective, but probably not by much. It's more important that the water (or in our case, the solution) be able to mix and move as the bubbles rise.

This may be true. But I can only offer my experience with "AP" (copper II chloride leach) and the observations that followed.
I could not pretend to be a physicist, not even on a radio show, but I have my ideas about what's going on.

Initially I used an open tube with a fast stream of wide bubbles, and leaching took several weeks, maybe 7-8. The surface had constant, semi-violent bubbling but only over the tube's position; it didn't splash more than about an inch or two above the surface.

When I added an aquarium "stone" to a similar batch, I saw leaching occur in about a week. The fine bubbles cause a lot more fizzing of tiny bubble splashes on the surface that greatly increase the need of a watchglass or loose lid even 200mm up the bucket walls. They turn the surface almost into a "vapour zone" compared the plain, boil-like effect of the bare ended tube. As you said Dave, dramatic oxygenation.

Very tiny bubbles also drift in the current and rise more slowly over a wider area. Therefore each one spends more time in contact.

I suspect that different aquarium stones with different pumps will exhibit different behavior. Twenty years ago when I first had fish, I used a tank-length aerator tube which made bubbles so fine, and caused so much above-surface effervescence, that I was concerned about my electric lamp. I ended up piercing the line with a pin in a dozen locations to keep the pressure down and each bubble size up.

For whatever reason, whether more underwater surface area or tension breaking on the top, I'll never revert from using a stone with copper II chloride leach. To each, his own. For me, it's just better.

 

[g_axelsson]

To keep spinning on GSP's post, a thick walled rigid tube can be filled with quartz pebbles. It is unaffected by the leach and keeps the tube on the bottom. Though, I would put in a few drainage holes at the end so any copper chloride that leaked in could easily be drained when harvesting the gold foils.

Göran