A passive stripping system

[Pilgrim2850]

Hi everyone,

The copper sulfate I used is "Roebic root killer for sewer and septic", active ingredient: copper sulfate pentahydrate 99%......inert ingredients 1%. Got it at the local hardware store (Best). I think it was around $9 for 2 lbs. If I get a chance this weekend I will run another batch with a silverplate item and take pictures and all that. Also I used hydrogen peroxide 3% from walmart.

larry

 

[eagle2]

I`m still expeimenting with the process, but I have noticed several things about the results, so far.

First, Cupric Sulfate is very soluble in water and the solution stays very clean. With no heating, no agitation some fingers and a few broken chip sockets had the copper stripped very cleanly and the gold foils/coatings, loosened very well from their surfaces. Took about a week. The solution turned very blue and a small dark precip deposits on the bottom along with the loose Gold foils.

Next, there dosn`t seem to be any such compound as Cuprous Sulfate; But a Cuprous Sulfite exists. (Cu2SO3). For the Cupric ion to be reduced to Cuprous (which is necessary in order to dissolve the Copper metal under the Gold) some Cuprous complex must exist, then possibly the H2O2 in solution reoxidizes the Cuprous ion back to Cupric.

While the process is working there is a fine stream of bubbles coming from the metal surfaces, so a reaction is continuously working.

My solution had a small amount of dilute Sulfuric acid, H2O2 and distilled water.

You can make a small amount of Cupric Sulfate, by putting Copper wire in hot Sulfuric.

Al

 

[Shecker]

It is Copper (III) Sulfate which is an oxidizer. So the correct name is Cupric Sulfate but they call it Copper Sulfate in the stores.

Randy in Gunnison

 

[eagle2]

Hi Randy.

Copper only has valences of +1 and +2

Cupric is +2 (Copper II) and Cuprous would be +1 (Copper I)

 

[Shecker]

It is the cupric form. My fingers sometimes hit too many keys at one time and I don't notice it -- an effect of arthritis and sinful living.

Randy in Gunnison

 

[OMG]

So does this method dissolve the gold and immediately precipitate it again, or does it just etch away the copper underneath, not affecting the gold at all?

If it just etches, maybe you should try something with iron(3) chloride (and h2o2), it dissolves copper rather quickly. If I were stripping computer components, I would definitely try iron(3) chloride. From what I read, it is commonly used to etch copper, and from my experience with iron chloride it does it quite easily. Using iron chloride I don't think you'd have any chance of dissolving any of the gold at all - as opposed to HCl and peroxide. Although if you heat up/dry out/concentrate iron(3) chloride enough it released HCl(g) and forms black iron oxychloride.

 

[Shecker]

Give it a try and issue a report. My effort in this was to provide an alternative method for stripping e-scrap.

Randy in Gunnison

 

[maltfoudy]

i am not a chemist but i have a question/concern. does this give off any fumes and or gas my concern is for H2S. some people believe H2S has a rotten egg smell but at a certain point you cannot smell it and it is lethal. i may be way off base with this,but the make up of the 2 chemicals kinda got the rusty wheels in my head moving. i do hazmat clean-up in the oilfield so i have a working knowledge of H2S. just a concern,i will leave the answer to the chemical experts.

 

[Shecker]

I have not noticed the product of any hydrogen sulphide gas. Since I work with this in an enclosed area I would have noticed this very quickly. I don't add any acid either. CuSO4 is naturally highly acidic.

Randy in Gunnison

 

[maltfoudy]

thanx for the response, i just read this and since everyone uses these i thought it might be worth a concern.


A series of suicide cases in Japan in which the victims killed themselves by producing toxic hydrogen sulfide fumes by mixing household cleaning products (such as toilet cleansing liquids) with bath salts have highlighted the danger posed by such common use substances and prompted censorship of internet sites who posted advice for aspiring suicides.[4]

 

[eagle2]

Good Grief, some one always has to try a new way of ending it all.

I`ve been experimenting with Cu SO4. It gives off no H2S by itself or with H2O2 or with dilute H2SO4.

A solution of CuSO4 with the above additves strips Copper very well and very cleanly. It does not dissolve Gold, but seems to easily get under it to dissolve the copper and tin.

I tried the same solution with Silver plate. A butter dish top that had a copper underbase. It loosened the Silver so I could scrap it off with a little work. I don`t know yet if any Silver went into solution, but definetely most of the Silver metal went to the bottom.

The Sulfuric and Peroxide do get used up and have to be replenished or the reaction will stop. I kept the PH under 1, when it went over 5 the action would stop. The leach solution lasts a long time without going bad (action slowing up, no matter how much Sulfuric and Peroxide you add). I think its the amount of other metals like Tin, Lead and Nickel, that eventually poison it.

Copper Sulfate is very soluble in water and dilute Sulfuric and it will hold a lot in solution until saturated and some copper sludge begins to form at the bottom. There is a patent that uses this process to leach Copper ores and along with this solution it highly recommends adding a small amount of Chloride ions, such as HCl or Salt or most any other Chloride salt compound. This speeds up the leaching 2 or 3 times quicker.

However I would say do not add any Chlorides if you have any Silver in your material to be leached. The Silver Chloride formed will cover the active leach areas and stop or slow it down.

Al

 

[Shecker]

When run this process I found a lot of AgSO4 developing in solution and going to the bottom of the tanks. It would keep the solution yellow colored.
I would periodically examine the boards and I would notice a definitely decrease in gold plated fingers and pins -- and in a few days that gold would be gone from them. There are factors on the boards (steel and aluminum pieces that cause precipitation of copper) and the gold and palladium would be in this sludge while most of the silver remained either in solution or as a precipitate as AgSO4, also in the sludge. The sludge assumes a grayish color enough though it will be high in copper. The grayish color should be a combination of silver and palladium. I was surprised at how much palladium this recovered. I also use this process on computer hard drives -- the copper sulfate is precipitated by the aluminum in the hard drive and the silver/platinum surface layer flakes off, sometimes in rather large pieces. I consider this be a combination of a transport mechanism and a metallic replacement mechanism rather than a leach, but it does work.

Randy in Gunnison

 

[OMG]

eagle2,
I am experimenting with h2so4 and h2o2(/o3), and I am just writing to make sure you (and everyone else reading) know about that combo and how dangerous it can be. Look up caro's acid, it is also called piranha solution, and Peroxymonosulfuric acid (h2so5). Keep any particles of organic solvents away from it because it can explode (never seen it happen, just read about it everywhere - at sciencemadness.org too). I'd just keep all organic matter away from it. particularly fingers.

 

[eagle2]

Thanks for the info OMG. I looked it up. You have to use highly concentrated Sulfuric and Peroxide to make it. But its something to be aware of.

 

[eagle2]

Randy, my solution never turned yellow, it pretty much stayed a clear blue. Silver Sulfate is not very soluble, so not much can be in solution. My tests were with only simple materials like fingers and chip sockets. Sounds like you have every kind of scrap in there at once and no telling what was reducing something else. My gold fingers fell off the pc material, stayed in the bottom of the beaker and never dissolved.

Al

 

[warrendya]

I was rereading this thread and had a question. Randy, it sounds like you break your e-scrap up before treatment with a hammer or such, which results in pieces large enough to physically separate from the sludge which occurs with treatment.

When I mill flatpacks and chips with either a ball mill or an old wheat grinder, the result is essentially flour. If I tried this process on this flour, I can't think of how to effect the mechanical separation of the sludge. Am I missing something?

Dan

 

[Shecker]

Like anything else in the chemical world of stripping pm's from e-scrap it won't work on unexposed materials. Since I leach the mother boards and all others in tact, first I break up the surface coverings of IC's and the CPU
so that the copper sulfate can get to them.

Reducing this material to the flour size would necessitate a different approach to recovery. At that point you may wish to burn off the organics and smelt the rest or treat it was an HCl-Cl leach (or even HCL/H2O2).

I use this passive stripping method because I can forget about for days or even a week on end and pm's will be right there for me to recover from the sludge on the bottom. It does take time to work.

Randy in Gunnison

 

[Shecker]

Yeah I throw in everything -- whole boards, connectors, exposed silver/copper wiring, whatever I can find. I particularly like boards with lots of monolithic capacitors. They leach really well.

Randy in Gunnison

 

[warrendya]

Reducing this material to the flour size would necessitate a different approach to recovery. At that point you may wish to burn off the organics and smelt the rest or treat it was an HCl-Cl leach (or even HCL/H2O2).

Yep, that was how I tried my experiment. Took 2 pounds of chip flour, treated with AP for 2 weeks, discarded solution (after checking with stannous), then treated with AC. Got busy and have left it alone for 2 weeks but still no sign of PMs still when tested. Next step planned is AR. All this is an experiment to satisfy my curiosity about PMs in flatpacks. So far I'm less than thrilled. I should have tried incineration, I had a lot of wetting problems with the dust.

Yeah I throw in everything -- whole boards, connectors, exposed silver/copper wiring, whatever I can find. I particularly like boards with lots of monolithic capacitors. They leach really well.

Do you smash each little surface mount monolithic cap or just soak them as is on the board?

Dan

 

[lazersteve]

Dan,

The monolithic caps will dissolve slowly in AP at room temperature.

The flatpak flour should be constantly stirred for the HCl-Cl to attack the fine gold wires in the mix. Heat is a defininte plus, even it's heat from the sun. A second possiblity is that the wires all ended up getting separated out in the screening or milling processes. The bottom of the ball mill may have your missing hair fine gold bonding wires.

I did a sample of one epoxy style chips and found that when the fine powder is shaken with excess water the gold wires all settle to the bottom of the test tube.

The wires were difficult to dissovle in room temperature HCl-Cl.

Another test I performed indicated that silver is a main ingredient used in the ground planes of the plastic quad style flatpaks. Silver will convert to silver chloride (insoluble) with AR or HCl-Cl.

Steve