Saturated AP filtering tip

[DJPGold]

Hello guys,
I’ve got roughly 10 litres of copper 2 chloride (Acid peroxide) very full of copper, so much that it’s a heavy liquid that is much more viscous than water and it is also full of gold foils and smaller gold particles. I’ve used this solution to do many kg of gold fingers.

Because of how dense the liquid is, it takes forever to filter and gets clogged easily. I’m waiting for a vacuum pump to arrive but need this job finished.
I was wondering if anyone has experience, or whether it’s possible, to use rinse aid in the solution to lower the surface tension of it, allowing it to flow easier through the accumulation of gold in the filter and through the filter medium itself.

I would be willing to try it myself but I don’t know what rinse aid is comprised of and I’m not a fan of “experimental chemistry” so maybe if someone knows if it’s safe and won’t ruin the solution, I’ll test it out for everyone.

 

[Martijn]

If it's still clear, let it settle and siphon off the majority of the liquid. Most of the gold will be on the bottom.
I assume you have a layer of white copper chloride on the bottom that is clogging the filter.
Add a bit of HCl and air to dissolve the insoluble copper 1 chloride. Let that settle when clear green and then siphon off and filter te last bit, rinse the filter with HCl, not with water.
Repeat the whole thing on the siphoned off liquid if any gold has settled out after some time. Then go for the stockpot and waste treatment.
It will get those last traces out.
Don't go chasing a couple of molecules.

Martijn.

 

[Martijn]

I siphon my AP off with a piece of filter wool ty-wrapped around the end of the tube.
The tube is connected to a catch flask with a slight vacuum.
The advantage of this setup is that you can skim the last bit of surface liquid off without having backflow in the vessel disturbing the particles on the bottom like with a normal gravity siphon. The capillary effect of the filter hairs pulls it up, with the tube end above the liquid.

Watch out with overfilling the catch flask.

 

[orvi]

Hello guys,
I’ve got roughly 10 litres of copper 2 chloride (Acid peroxide) very full of copper, so much that it’s a heavy liquid that is much more viscous than water and it is also full of gold foils and smaller gold particles. I’ve used this solution to do many kg of gold fingers.

Because of how dense the liquid is, it takes forever to filter and gets clogged easily. I’m waiting for a vacuum pump to arrive but need this job finished.
I was wondering if anyone has experience, or whether it’s possible, to use rinse aid in the solution to lower the surface tension of it, allowing it to flow easier through the accumulation of gold in the filter and through the filter medium itself.

I would be willing to try it myself but I don’t know what rinse aid is comprised of and I’m not a fan of “experimental chemistry” so maybe if someone knows if it’s safe and won’t ruin the solution, I’ll test it out for everyone.

If you have time, let it settle for a day or two as Martijn suggested. If there are some gold foils which float on the surface, spray them down with water spray - it will knock them under the surface of solution and they will sink.

And also as Martijn suggested, if there is white ppt of CuCl, add HCL to redissolve it. If just redissolving the CuCl with HCL, you will need more than when you aerate the solution - converting the CuCl to soluble CuCl2 - for this conversion you just need stechiometric HCL and oxygen to oxidize the Cu(I) to Cu(II).
But just adding some HCL to it is quicker and it does the thing you want.
Filtering ultrafine particles of gold is sometimes nightmare, they can pass practically any filters... But from AP, you should have decent sized particles. Not micro gold. So decantation should work nicely. Just go slow with siphoning, as very floaty small bits can be easily sucked to the tube

Better to decant just 2/3 or 3/4 of solution, then check if everything is still nicely settled, and continue. If not, pour it to the another container for re-settling. New container would be smaller, and you can effectively reduce the solution down to practically zero with this low-end no-cost technique

 

[DJPGold]

If you have time, let it settle for a day or two as Martijn suggested. If there are some gold foils which float on the surface, spray them down with water spray - it will knock them under the surface of solution and they will sink.

And also as Martijn suggested, if there is white ppt of CuCl, add HCL to redissolve it. If just redissolving the CuCl with HCL, you will need more than when you aerate the solution - converting the CuCl to soluble CuCl2 - for this conversion you just need stechiometric HCL and oxygen to oxidize the Cu(I) to Cu(II).
But just adding some HCL to it is quicker and it does the thing you want.
Filtering ultrafine particles of gold is sometimes nightmare, they can pass practically any filters... But from AP, you should have decent sized particles. Not micro gold. So decantation should work nicely. Just go slow with siphoning, as very floaty small bits can be easily sucked to the tube

Better to decant just 2/3 or 3/4 of solution, then check if everything is still nicely settled, and continue. If not, pour it to the another container for re-settling. New container would be smaller, and you can effectively reduce the solution down to practically zero with this low-end no-cost technique

Cheers guys. About 5 days in and I’ve finally got everything into one funnel I was using distilled water to do rinses when necessary and also noted a white precipitate forming on the surface. Is this copper 1 chloride forming from me diluting the solution?

 

[orvi]

Cheers guys. About 5 days in and I’ve finally got everything into one funnel I was using distilled water to do rinses when necessary and also noted a white precipitate forming on the surface. Is this copper 1 chloride forming from me diluting the solution?

Exactly That indicates that you thoroughly spent all free Cl- in the solution
CuCl alone in water has exceptionally low solubility. But if you add free HCl, it form CuCl2(-) anions which are soluble. As this is a complex anion, it is in eqilibrium with free CuCl and HCl. And if concentration of HCl goes down (rinsing with water), it goes towards former reactants and CuCl precipitates.

Same thing happen when you overadd SMB when dropping gold from heavy Cu solutions. You will observe white crystals growing in your solution - because CuCl2 gets reduced with SO2 forming Cu(I) - which is insoluble in low HCL solutions.

So next time, rinse with dilute HCL if you want to prevent this. Or add HCL and re-oxygenate the solution for a day - this will convert all Cu(I)Cl to Cu(II)Cl2 - which is soluble. And you does not need to waste additional HCL to washing, as CuCl2 is also soluble in plain water.

And last, in my opinion, using distilled water for washing AP remains is quite wasteful you will be also completely fine with regular tap water. If it was something like AgNO3 solution, then it is completely rational to use distilled water (containing chlorides). But now you already have saturated chloride solution, where using ultrapure Cl free water makes no sense

 

[DJPGold]

Exactly That indicates that you thoroughly spent all free Cl- in the solution
CuCl alone in water has exceptionally low solubility. But if you add free HCl, it form CuCl2(-) anions which are soluble. As this is a complex anion, it is in eqilibrium with free CuCl and HCl. And if concentration of HCl goes down (rinsing with water), it goes towards former reactants and CuCl precipitates.

Same thing happen when you overadd SMB when dropping gold from heavy Cu solutions. You will observe white crystals growing in your solution - because CuCl2 gets reduced with SO2 forming Cu(I) - which is insoluble in low HCL solutions.

So next time, rinse with dilute HCL if you want to prevent this. Or add HCL and re-oxygenate the solution for a day - this will convert all Cu(I)Cl to Cu(II)Cl2 - which is soluble. And you does not need to waste additional HCL to washing, as CuCl2 is also soluble in plain water.

And last, in my opinion, using distilled water for washing AP remains is quite wasteful you will be also completely fine with regular tap water. If it was something like AgNO3 solution, then it is completely rational to use distilled water (containing chlorides). But now you already have saturated chloride solution, where using ultrapure Cl free water makes no sense

Awesome reply mate thanks heaps. Screen shorted and noted I have about 3-4 litres in the funnel so I added about 150ml of HCL and gave it a good mix, hopefully oxygenating the solution somewhat as well. I noted the level in the funnel so hopefully after my 8 hour class I should see a difference.
If nothing has really happened I’ll siphon the liquid the out of the funnel, wash any foils and sludge into my beaker and then return the solution to the funnel after bubbling air through it for an hour or so.
This 10L of solution has done its job on 6.6kg of fingers so it’s pretty heavily saturated with copper and foils

 

[war_child]

I wonder:

What would happen if you had a large vessel filled with well used, saturated clcu2. Say this acid had been used for many batches of trimmed fingers and the like. Consequently, this solution also contains obvious flakes of gold that are very small, maybe from ribbon wires or something. They flow right through the filters when you try to recover them.

If you add HCL with a bubbler AND a large dose of hydrogen peroxide (maybe even heat the AP), would that dissolve the gold flakes into solution? It's kind of like the warning people give to someone who is going to try the AP method for removing gold foils: "don't use too much h2o2, you can start dissolving your gold" IF so, would you be able to get the gold back out? Perhaps by cementing onto copper?

...just asking for a friend. He has a large bucket of old AP with tiny gold flakes in it

Thanks,
mike

 

[DJPGold]

I wonder:

What would happen if you had a large vessel filled with well used, saturated clcu2. Say this acid had been used for many batches of trimmed fingers and the like. Consequently, this solution also contains obvious flakes of gold that are very small, maybe from ribbon wires or something. They flow right through the filters when you try to recover them.

If you add HCL with a bubbler AND a large dose of hydrogen peroxide (maybe even heat the AP), would that dissolve the gold flakes into solution? It's kind of like the warning people give to someone who is going to try the AP method for removing gold foils: "don't use too much h2o2, you can start dissolving your gold" IF so, would you be able to get the gold back out? Perhaps by cementing onto copper?

...just asking for a friend. He has a large bucket of old AP with tiny gold flakes in it

Thanks,
mike

I assume that would be possible. I usually like to just pour off as much acid from the bulk of the foils as I can, and then run the AP through a very dense filter like packed cotton, this usually gets all the gold and the gold that it misses will be recovered from the stock pot process. I keep my filters seperate from the foils when I refine them because I use HCl and bleach, and it’s a pain to stir the foils when the beaker contains lots of filtering medium

 

[Shark]

If you add HCL with a bubbler AND a large dose of hydrogen peroxide (maybe even heat the AP), would that dissolve the gold flakes into solution?

Look into the history of AP. The original intent was to dissolve the gold. Once the gold was in solution it could then be dropped with most common precipitants. AP was later developed to make an easier method of recovering foils and flakes from gold fingers and boards by limiting the volume and strength of the peroxide. This limit would dissolve the copper base but leave the gold layer intact.

 

[orvi]

I wonder:

What would happen if you had a large vessel filled with well used, saturated clcu2. Say this acid had been used for many batches of trimmed fingers and the like. Consequently, this solution also contains obvious flakes of gold that are very small, maybe from ribbon wires or something. They flow right through the filters when you try to recover them.

If you add HCL with a bubbler AND a large dose of hydrogen peroxide (maybe even heat the AP), would that dissolve the gold flakes into solution? It's kind of like the warning people give to someone who is going to try the AP method for removing gold foils: "don't use too much h2o2, you can start dissolving your gold" IF so, would you be able to get the gold back out? Perhaps by cementing onto copper?

...just asking for a friend. He has a large bucket of old AP with tiny gold flakes in it

Thanks,
mike

I would rather not do this.

As I regularly process material through AR dissolution (pins, transistors...) I know how painful is recovering it through this route, when material runs lower than 2g/kg gold. That is roughly 2g Au per 5L of solution, thus 0,4g/L. After de-NOx-ing, you are left practically with same solution as you will get by dissolving bits of gold in AP. You usually obtain very very fine purplish-blackish precipitates that settle for more than a day, not to mention they pass any filter paper (also quality analytical thick ones for sure) and are nightmare to decant quantitatively, as slightest disturbance mess all your hard work and swirl the dust in the beaker.

If you dissolve that little ammount of gold back into the solution, you will obtain very very dilute gold solution, which would be extremely difficult to manage. Cementation would work, but again making ultrafine gold dust, which would be also hard to collect.

If you already have the gold in upper micron sizes (visible individual particles), you better settle and decant for sure

 

[Martijn]

You usually obtain very very fine purplish-blackish precipitates that settle for more than a day, not to mention they pass any filter paper (also quality analytical thick ones for sure) and are nightmare to decant quantitatively, as slightest disturbance mess all your hard work and swirl the dust in the beaker.

My filterwool-dotted-vacuum-tube siphon works great for this problem too. I once had a blueish purple color in solution which took weeks to settle. Skim-siphoned the clear liquid off and redissolved the blue bottom layer along with a dirty AR digestion.

 

[Martijn]

Yes i was chasing molecules in this case

 

[orvi]

My filterwool-dotted-vacuum-tube siphon works great for this problem too. I once had a blueish purple color in solution which took weeks to settle. Skim-siphoned the clear liquid off and redissolved the blue bottom layer along with a dirty AR digestion.

I also once experienced blueish-purple madness but when refining cut contact points. For the matters of buy/sell, whole lot was smelted down to ingot (2,7 kg, average 30-33% Ag). So I started to dissolve it in nitric, and ended up with visibly turbid purplish solution. I started to filter it through large fritted glass filter (ca 10L of soln. in the end, fritted glass diameter around 18cm - plain utopia ), after like 1 hour of drop to drop filtration my nerves ruptured, and I didn´t filter that goo... Saying - I will cement that Ag out on copper, it will be fine, I will run it through the cell anyway. MAN, what an epic mistake.
When I sticked the copper plate into the solution, I didn´t realized from the start what is happening. Superfine silver mud was forming (as it cannot grow larger due to colloid/goo in the solution), impossible to filter, impossible to flocculate, impossible to decant. Anger level 9999.
In the end I dissolved everything back to the solution with nitric, dropped the bulk as silver chloride and converted that to Ag by lye sugar. As large ammount of AgCl formed, it covered the colloid nicely, packed and could be decanted very easily. I relied on this to happen, and luckily it worked nicely.

Long story short, I discovered the purple goo to be colloidal gold (some gold plated contacts were also present in the batch, but not enough to measure on XRF when shooting the melted bar) mixed with tin metastannic goo

It could be that in your case, you had a bigger ammount of solder that has dissolved gold in it (from gold plated traces or pins - gold has perfect solubility in solder/tin even at soldering temperatures) - and as AP chewed through it, it left ultrafine gold particles.