Sciencemadness Discussion Board - Gold Recovery Computer Scrap Complete Process

I really want to see a whole process, so there's 3g of .999 Au winging it's way from Istanbul to see what will happen.

This will be solid gold, which might take ages to dissolve.

Would it be better to melt it and chuck it in a bucket of water to make shot ?

Does that even work with gold ?

There's no chance that i'm going to file 1g of metal into filings.

If you melt the 3g of pure gold and pour it in a METAL container of cold tap water it will flatten out and present more surface area to the acid, and dissolve quicker.

Be careful not to get the gold too hot when you melt it, let it cool a second or two before you pour the molten gold into the water. If you pour it while it's real hot it will make a loud pop and bust up into tiny gains smaller than sand. No problem, but it could cause you to lose some of the metal because it will be so small.

Then take the flakes of gold from the tap water, and put in a 250ml beaker with a watch glass. Next add about 100ml HCl. Place on LOW heat (under no circumstances should you boil it) and add concentrated nitric acid a drop at a time until all the gold dissolves - should only take about 1 or two ml of nitric.

Once it's all dissolved, filter out any solids making sure to rinse the filter free of color. Return the clear filtered chloroauric acid to the beaker and place it inside a Corning ware dish in case you get a boil over. Add a spoon of sodium meta bisulfite
And watch the gold precipitate almost immediately. Test the solution with stannous chloride! If positive then add some more SMB until all the gold comes down and the stannous test is negative.

Wait for the gold powder to settle then decant the barren liquid by siphoning with a small tube or use a transfer pipette, then rinse the gold powder with some HCl and decant after settling. You can dry the gold powder over low heat while it's still in the beaker.

You will be left with about three grams of brown powder that is pure gold. You can then try to dissolve as per step two from deltaH.

I could have sold you 3g of pure gold powder in a nice little glass vial for about $40 per gram - let me know if you need some gold in the future.

kadriver

kadriver - 7-10-2015 at 18:10

It'll be a 1g bar of solid gold, specifically this :
http://www.ebay.co.uk/itm/301586182892?_trksid=p2057872.m274...

Your show deltaH, so do as much calculating as you can in the time before the gold arrives.

When it arrives, there's dissolving to get done.

I ordered 3 so one can go into an aqua regia solution for comparison.

I wish you would have checked with me. I could have poured the shot/flakes for you at $40 per gram then shipped as a gift with no duty to the UK.

Here is a gold bar that I just finished;

kadriver - 7-10-2015 at 18:23

To make this a fair test for a comparison to aqua regia, we should match up the concentration of chloride in both. That way we will compare on oxidising ability alone. What recipe will you be using for the aqua regia?

The oxidation potential of 1M HClO solution at pH 4.5 is ~1.4V or about the same as chlorine gas. I'd say this is very comparable to aqua regia and so expect similar dissolution rates.

[Edited on 7-10-2015 by deltaH]

It is best NOT to premix the Aqua regia. Prefixing guaratees that there will be excess nitric that causes problems when you go to precipitate the gold.

Instead add just HCl, cover, place on low heat, and add concentrated nitric a drop at a time until all the gold dissolves. With 1 gram I would add only 20 or 30ml HCl. Then just drops of HNO3.

Also, if you have any, add about three or four drops of H2SO4 just before you filter the chloroauric acid solution as a precaution to precipitate out any lead as lead sulfate. It can then be filtered out. It doesn't hurt a thing, but lead, even in trace amounts, will ruin the ductility of the gold.

Hope this helps.

kadriver

kadriver - 7-10-2015 at 18:39

That's pretty kadriver and your yields are thoroughly consistent!

The way I see it, this process has three important sections:

Mineral acid-free 'fish and chips' gold refining process

(1) Base metal leaching: vinegar + salt + air bubbling + initial H2O2
(2) Gold foil dissolution: vinegar + salt + bleach
(3) Base metal recovery: ?

Comments:

* Step (1) has now been tried on small and larger scales thanks to the pioneering work of aga and kadriver. Step (2) has only been tried on a small scale by aga and Step (3) is largely completely open.

* Step (3) is vitally important though. Without it, the process doesn't deal with its waste and is incomplete.
Also, part of the copper containing solution from step (3) could be recycled into step (1) so that peroxide is no longer needed, then this thing would come full circle and you would have a reliable, low cost and safe complete process that could be used again and again.

Looking forward to someone continuing the research into this, i.e. scaling up of step (2) and development of step (3).

[Edited on 7-10-2015 by deltaH]

How about 2a; precipitating the pure gold powder?

There are several choices. I prefer sodium meta bisulfite. It is sold at the hardware store as "Stump Out" stump remover by BONIDE. Stump out by spectracide is NOT sodium meta bisulfite, it is potassium nitrate! So be sure it's stump out by BONIDE.

Another good one is copperas (ferrous sulfate) it is also sold at gardening shops and the hardware store. To use I pour about 200ml of the green powdered ferrous sulfate into a 600ml beaker, then fill with tap water to about 500ml and stir over low heat until dissolved.

It will look orange in color, I add about 10ml of hydrochloric acid to turn it green. I set up a filter station with a ring stand and filter the dissolved ferrous sulfate directly into the clean chloroauric acid solution. The gold precipitates quickly and cleanly.

Ferrous sulfate produces no noxious fumes, but SMB make lots of sulfur dioxide gas and must be done in a fume hood.

kadriver

kadriver - 7-10-2015 at 18:49

Another though; using gold powder vs gold shot will more closely match gold foils as the foils are just microns in thickness where as the gold flakes/shot could be several millimeters thick.

kadriver

Little_Ghost_again - 8-10-2015 at 00:08

Out of interest do you know what happens to the rest of the board after they cut the fingers off and sell on ebay?

kadriver - 8-10-2015 at 00:44

Quote: Originally posted by Little_Ghost_again

Out of interest do you know what happens to the rest of the board after they cut the fingers off and sell on ebay?

Some of the chips have traces of gold. They can be removed and the gold recovered and refined, but it takes a lot of them to get any gold.

The actual boards have copper and nickel, only the connection points, the "fingers" are gold plated.

I don't know what happens to them once the fingers are trimmed off.

kadriver

deltaH - 8-10-2015 at 02:38

That's a good point about adding in the nitric acid as required and thanks.

Back to matching chloride concentrations, aga, if you're using 37% HCl, that a 12M solution of chloride ions, which means you will need a 12M solution of NaCl, that's 701g/l... NOT POSSIBLE :mad:

The best you can do is half that i.t.o the solubility of the NaCl in pure water, probably much lower in pure vinegar (the 5-10% acetic acid would make the salt less soluble).

[DON'T be tempted to use ammonium chloride, it will kill you!

[Edited on 8-10-2015 by deltaH]

deltaH - 8-10-2015 at 02:47

Another good point, yes the reducing agent does indeed warrant some thought.

The whole idea with the fish and chips process is to use benign and also environmentally benign, cheap OTC reagents.

Nothing too wrong with the ferrous sulphate nor sodium metabisulfite, but... there's always a but

... I would favour an even more benign and environmentally friendly reducing agent.

In that sense, I am thinking a non-toxic organic agent is better. Something like ascorbic acid (vitamin C)? It's cheap, you can chuck it down the drain with no impact on the environment and it's completely non-toxic and benign to the user working with it.

Can you share your experience with us on this kadriver? Can it be used?

deltaH - 8-10-2015 at 02:49

Another though; using gold powder vs gold shot will more closely match gold foils as the foils are just microns in thickness where as the gold flakes/shot could be several millimeters thick.

kadriver

I think aga wants a 'show stopper' of sorts, i.e. to see if this can match aqua regia head-to-head in the really tough dissolution... bulk gold pieces.

Little_Ghost_again - 8-10-2015 at 03:37

I know everyone is chasing gold, BUT there is alot of copper compared to gold in pcb's, while the spot price isnt fabulous I have spotted another outlet with good returns.
I would be very interested in buying the scrap boards with gold already recovered and the copper left in place

, I figure they have to be cheaper by a long way. If you look carefully there are places copper is worth more than gold, then look at the copper process used here, do you have a rough idea of mesh size from the copper powder you recover?

aga - 8-10-2015 at 05:59

I think aga wants a 'show stopper' of sorts

Not at all !

I just don't fancy the idea of spending hours machining the gold down into a fine powder.

deltaH - 8-10-2015 at 09:29

Though if it works, it would be one

kadriver - 8-10-2015 at 10:11

I've used SMB, copperas (ferrous sulfate), oxalic acid (wood bleach), SO2 gas, and cement the gold on copper. I've never even considered vitamin C. How would that work? That would be something!

kadriver

deltaH - 8-10-2015 at 11:36

Ascorbic acid (Vitamin C) is a mild reducing agent that gets oxidized to dehydroascorbic acid by two electrons, so you need a minimum (an excess would be wise) of 3/2 moles ascorbic acid per mole of gold.

It can reduce most oxidizing metallic solutions with boiling. You're supposed to use 100% ascorbic acid, not lemon juice aga

Here's an example:

https://www.youtube.com/watch?v=J-rZXQNFauI

Note: with copper the yields are not very good, but then copper(II) is a weak oxidant, unlike silver and gold, which should be much faster and better yielding.

I was just wondering if anyone actually tried it with gold and how well that worked.

EDIT:

Here's a brief video of the reaction with silver nitrate... definately much faster as expected.

https://www.youtube.com/watch?v=V7r2gUA9gTM

Again, boiling it would probably be wise to help the nanoparticles coalesce and then settle out overnight.

EDIT: using sodium ascorbate might work better for chloroauric acid solutions.

[Edited on 8-10-2015 by deltaH]

kadriver - 8-10-2015 at 18:27

Can I get ascorbic acid from a health store like GNC? I could do this experiment tomorrow if I had the vitamin C.

j_sum1 - 8-10-2015 at 18:38

Most vit C tablets are high purity ascorbic acid. Capsules if you can find them are even better. you can always recrystallise if you think those impurities are likely to be problematic.
Or, you can buy it as a lab reagent fairly easily if you have the contacts. probably easily available on eBay too.

Bert - 10-10-2015 at 05:32

$9.50 US per lb. in bulk-

http://www.amazon.com/gp/aw/d/B00YO53APY/ref=mp_s_a_1_5?qid=...

It also makes a decent propellant when mixed with Potassium nitrate...

kadriver - 10-10-2015 at 20:34

OK, here is part 1 of 2 of the video where I scale up the Vinegar - Salt - Hydrogen Peroxide recovery of gold foils from the trimmed circuit card fingers.

Now that I kind of know what to expect I should be able to complete the experiment on VIDEO.

Many thanks to deltaH and aga for the help they provided!

https://youtu.be/ouYW_7-Njbs

kadriver

deltaH - 10-10-2015 at 21:23

Very nice indeed, well done and thank you for making the excellent videos! There's small things that you do that just makes it a cut above the rest, like the way you place the glass rod in line with the beaker lip when you pour ans the controlled movements throughout, it's chemical choreography :cool:

I can not tell you how disappointed I was to see the video end where it did... I know, patience

You should consider making this part of a series of 'Gold Recycling using Green Chemistry'. From all that has been discussed, there could be several videos in it already and I think once news gets out of a complete series of these videos, you will have excellent viewership.

Please try to cut out HCl completely throughout, then we would have really accomplished something here. For the gold dissolution step, I strongly suggest you raise the pH of the salted vinegar BEFORE adding bleach with 0.2M sodium hydroxide solution to 4.5 so that one avoids the copious production of chlorine gas (hopefully).

You could finish off everything with an ascorbic acid reduction to make the process really Green and interesting. Like Bert showed, it's cheap stuff in semi-bulk scale.

[Edited on 11-10-2015 by deltaH]

violet sin - 10-10-2015 at 21:36

cool stuff you guys are doing here. I have been following in silence. the notion of green chem in a field that is so full of harsher verities is really awesome. this also gives more people access to a process that won't get the cops called by ordering multi gallon shipments of HNO₃, like LGA said. kudo's

Agari - 10-10-2015 at 21:40

I can't possibly be the only one who thought of this,but using Aqua Regia would have been less time-consuming in my opinion.

kadriver - 10-10-2015 at 21:44

Very nice indeed, well done and thank you for making the excellent videos! There's small things that you do that just makes it a cut above the rest, like the way you place the glass rod in line with the beaker lip when you pour ans the controlled movements throughout, it's chemical choreography :cool:

I can not tell you how disappointed I was to see the video end where it did... I know, patience

Wow! These are great suggestions. The bubbling took about 4 or 5 days to get about 98% of the foils off the fingers. I'll shoot video of the bubbler at 12 hour intervals to give a good picture of what's happening.

Aga has already dissolved the foils in the salt vinegar solution just by adding heat and bleach, completely eliminating any HCl.

I'm embarrassed to say that I have no idea how to make and add 0.2M NaOH solution. And I only have paper test strips to read pH. Can you give me a little help there. Where can I get a good pH meter that will stand up to these chemicals? I don't mind paying a little extra for a good meter.

I'd like to dissolve some gold foils ahead of time, off camera, using the directions you've given above. That way when it comes time to actually dissolve on camera I know what to expect.

I'll get some of the chemical Bert referenced to do the precipitation. This will be unbelievable if it works as expected.

You guys really know your stuff. I am so grateful to everyone who has input to this chemistry/gold refining adventure!

kadriver

kadriver - 10-10-2015 at 21:56

I can't possibly be the only one who thought of this,but using Aqua Regia would have been less time-consuming in my opinion.

Absolutely, but I think we are trying to find a process that completely eliminates those corrosive mineral acids.

So far we are only using;

01) white distilled vinegar
02) sea salt
03) hydrogen peroxide 3%
04) lye to raise pH
05) bleach to dissolve the gold foils
06) ascorbic acid for reduction - precipitation

So far no nitric, hydrochloric or sulfuric acids!

If we can eliminate the chlorine gas by raising the pH as deltaH proposes, then this would almost be suitable as an eight grade science project - but NOT recommended as such.

kadriver

j_sum1 - 10-10-2015 at 22:05

Developments have been thick and fast here and I will admit to not having read the whole thread or viewed all of the videos. But, in my view, this is really exciting. Please, when done, as well as the videos, do a write-up in prepublication. This great work deserves all the recognition it can get. And as for school projects, I can really see it working. I am going to put it on the list of suggestions for my students next year.

aga - 10-10-2015 at 22:27

no idea how to make and add 0.2M NaOH solution

Look up the molecular weights of each element (Na, O, H) on the periodic table http://ptable.org

The M.W. is the bottom left number in each box.

Na = 22.99
O = 15.99
H = 1.01

Add them up and the weight per Mol of NaOH = 39.99

So if you dissolve 39.99g of NaOH in 1 Litre of water, you'd have a 1 Molar concentration of NaOH in that solution.

You'd write that as '1.0M NaOH solution'.

That's 5 times too strong for the 0.2M required, so you can either add 5 times more water (5 litres + 40g) or 5 times less NaOH (1 Litre + 8g) to reach 0.2M concentration.

deltaH - 10-10-2015 at 22:42

Quote:

Very nice indeed, that should look great!

Quote:

Aga has already dissolved the foils in the salt vinegar solution just by adding heat and bleach, completely eliminating any HCl.

Yes but aga added the bleach to neat vinegar and salt which evolved 'tons' of chlorine gas. The real benefit here is going to come from finding the sweet spot for pH, where chlorine gas is not evolved in copious amounts, but where the solution is still strong enough of an oxidant to dissolve the gold.

As a first guess, pH 4.5 according to those diagram I attached earlier looks close to being right. I'd go slightly higher if necessary, but not lower, unless higher or 4.5 doesn't work, in which case going lower is the last remaining choice, but then one will evolve some chlorine.

Quote:

I'm embarrassed to say that I have no idea how to make and add 0.2M NaOH solution.

Don't be embarrassed, we're all learning. The molar mass of sodium hydrogen is the sum of the atomic masses of the elements in its formula multiplied by the number of one element, in this case all 1: NaOH, read off a periodic table: 23 for sodium*1 + 16 for oxygen*1 + 1 for hydrogen*1 = 40g/mol. 40g is thus one mole of sodium hydroxide. 0.2M means a concentration of 0.2 moles dissolved in 1 litre of water. so 0.2 moles is 0.2*40g, or 8g NaOH which has to be dissolved in 1 litre of water to get a 0.2M solution.

Quote:

And I only have paper test strips to read pH. Can you give me a little help there. Where can I get a good pH meter that will stand up to these chemicals? I don't mind paying a little extra for a good meter.

pH strips can work here, you can target pH 4-5. You're adjusting pH before adding any oxidants so you should worry about bleaching the dye at this stage.

For a good pH meter, there are others and threads on SM that can advise better. Just don't forget to calibrate the meter before each use.

Quote:

I'd like to dissolve some gold foils ahead of time, off camera, using the directions you've given above. That way when it comes time to actually dissolve on camera I know what to expect.

A good idea. The pH 4.5 is an educated guess, but may require tweaking. If you still see fizzing after adding bleach, then it's too low and I would try pH 5 and so on until you have the lowest pH that doesn't release large amounts of chlorine.

If you see no fizzing at pH 4.5 as expected, then next time you might want to try pH 4 and see if that fizzes etc.

Optimal is the lowest pH at which you don't release lots of chlorine.

Quote:

I'll get some of the chemical Bert referenced to do the precipitation. This will be unbelievable if it works as expected.

I am 99.99% sure ascorbic acid will reduce gold. The only problems I anticipate is that you might have residual oxidant (bleach) in your gold dissolution solution which will require more ascorbic acid to neutralise than for the gold alone and also that the gold will initially be in a colloidal form (nano-gold). So the trick here will be to coalesce and merge those so they get large enough to settle. That means boiling it after adding the ascorbic acid.

As a procedure, I'd say in a fume cupboard, add 3% H2O2 drops to your dissolved gold until it doesn't fizz when the drop hits. This is to destroy excess bleach by making oxygen. The fast reaction is:

ClO^- + H2O2 => Cl^- + H2O + O2(g)

Then pre-dissolve 2g ascorbic acid in 8 ml water and add it the solution with stirring. Then boil the mixture in a fume cupboard and then set aside to cool and settle the gold (overnight if necessary) before filtering and washing at the filter with clean water.

deltaH - 10-10-2015 at 22:46

I can't possibly be the only one who thought of this,but using Aqua Regia would have been less time-consuming in my opinion.

He he, I see in the time it took for me to write my long response, there's been a 1000 responses already lol HOT TOPIC!

You can actually substitute the lye which is corrosive with sodium bicarbonate, then it can become a junior lab project

Kid's love adding bicarb to vinegar after all!!!

Little_Ghost_again - 11-10-2015 at 01:52

A couple more weeks and this process should be down to using vinegar and just a packer of aga'a special nitrogen!

I hope he has it in bulk

kadriver - 11-10-2015 at 15:33

no idea how to make and add 0.2M NaOH solution

So I could add 0.8 grams NaOH to 100ml distilled water to make a 0.2M NaOH solution, rather than dissolving 8grams in 1 liter.

Great explanation by the way, thank you.

kadriver - 11-10-2015 at 16:11

You can actually substitute the lye which is corrosive with sodium bicarbonate, then it can become a junior lab project

Kid's love adding bicarb to vinegar after all!!!

Do you think that the bicarbonate would do? If you think it will work then I'll use it instead of lye.

I shot some more video at noon on Sunday, I'll get some more footage at midnight. There were just a few foils at noon today, Sunday.

aga - 11-10-2015 at 16:20

So I could add 0.8 grams NaOH to 100ml distilled water to make a 0.2M NaOH solution, rather than dissolving 8grams in 1 liter.

Yep. You got it.

If you already made a 1.0M concentration solution of NaOH, you can use the formula

C1V1 = C2V2

to make a different LOWER concentration.

So, if you got 1000ml of a 1.0M concentration solution of NaOH (40g in 1 litre)

You need 0.2M concentration.

C1 = what you got = 1.0 M concentration
V1 = 1 litre = 1000ml of water containing that stuff.

C2 0.2M = the concentration you want

V2 = the Mystery Number.

rearrange the formula and you get V2= (C1 x V1) / C2

So V2 = ( 1.0 x 1000 ) / 0.2 = 5000ml, or 5 litres.

So just add an extra 4 litres of water and your 1.0M solution becomes a 0.2M solution.

The [M] thing is how many Moles there are.
A Mole is defined as 6.022 x 10<sup>23</sup>
Usually written as M, [M] or Mol to avoid embarassment, or confusion with moles.

So if you dissolve 39.99g of totally pure NaOH in 1 litre of totally pure water (to make a 1.0M solution) then there are about 602200000000000000000000 molecules of NaOH in that water.

The number is too big to handle easily, so we use the Mol as a measure instead.

Incredible that i'm explaining this to somebody else now, as two years ago i had absolutely no idea at all.

Knowledge is a wonderful thing, as is this forum.

[Edited on 12-10-2015 by aga]

Agari - 11-10-2015 at 16:33

I can't possibly be the only one who thought of this,but using Aqua Regia would have been less time-consuming in my opinion.

I would have used AR anyways since all you have to wait for is for it to dissolve the material(which happens much faster),use a reducing agent to precipitate the solute,then just separate the gold from plastic with a torch.Since gold and plastic have different melting points, it is possible to melt one of them and then separate the liquid, then keep doing it until the gold is surely separated.

aga - 11-10-2015 at 16:47

Rethink or erase that Agari.

You clearly have not read this thread or understood the direction it is going in.

Is Agari another other persona of a well known SM member ?

It could just be my innate paranoia, but there seem to be a few similar personae emerginging recently, related to some not-so-recent.

Agari - 11-10-2015 at 17:02

Rethink or erase that Agari.

You clearly have not read this thread or understood the direction it is going in.

Is Agari another other persona of a well known SM member ?

It could just be my innate paranoia, but there seem to be a few similar personae emerginging recently, related to some not-so-recent.

I actually did not read all of the above lol.

Little_Ghost_again - 11-10-2015 at 17:08

I can't possibly be the only one who thought of this,but using Aqua Regia would have been less time-consuming in my opinion.

AR isnt OTC for many, especially in the UK and next year its going to be a whole lot harder to get Nitric acid.
From next year just having it is going to be a serious no no for most.

The point of the thread is to develop a process that not only recovers the metals, but a process that cuts down the needless pollution generated in doing so.

Each person using AR dosnt use much but add up the number of people doing it? Also a good many are poorly equipped to handle the waste or even the material in the first place.
So it takes a little time longer but its open now for just about anybody and dosnt use anything that would get you a unwanted visit.

While the talk is normally about restricted chemicals it isnt going to take a genius at some point to work out how much tax is being lost. So unless refiners are declaring the gold and paying the duty etc then they are tax avoiding. Here in the UK thats worse than murder or being kiddy fiddler.

Take a penny from the queen and they want your balls on a plate, so my view is this process apart from being utter genius and eco friendly shouldnt draw much attention, then again I doubt that many think about the day the tax man will kick in the door and ask about your ebay sales.

That day is just around the corner in the UK, easier to fuck over 3 million easy pickings from ebay than go after the clever fuckers who are non doms etc, look at the land deals the chancellors family have done in the last five years, try and find the developers who they sold the land too, the trail suddenly stops.

Sorry I sound like I am paranoid now

, but the farm down the road repairs a few boats got on ebay, does them up and makes a few quid selling back on ebay. hasnt declared a penny of it for five years, and got a knock last year. It isnt looking good for him and probably will cost him his home in the end

aga you are one of the most paranoid people I have ever met, I learn from that

[Edited on 12-10-2015 by Little_Ghost_again]

kadriver - 11-10-2015 at 17:18

The [M] thing is how many Moles there are.
A Mole is defined as 6.022 x 10<sup>23</sup>
Usually written as M, [M] or Mol to avoid embarassment, or confusion with moles.

So if you dissolve 39.99g of totally pure NaOH in 1 litre of totally pure water (to make a 1.0M solution) then there are about 602200000000000000000000 molecules of NaOH in that water.

The number is too big to handle easily, so we use the Mol as a measure instead.

[Edited on 12-10-2015 by aga]

Avogadro? I recognize that from Khan Academy. I studied a little there. Found out about the S-block, the P-block and the D-block. Also how to find the electron configuration of the elements off the periodic table.

I've got to get off my butt and enroll in some chemistry classes at our community college. I'd like to be able to know what's going on inside those beakers at the atomic level.

kadriver

kadriver - 11-10-2015 at 17:53

Quote: Originally posted by j_sum1

Developments have been thick and fast here and I will admit to not having read the whole thread or viewed all of the videos. But, in my view, this is really exciting. Please, when done, as well as the videos, do a write-up in prepublication. This great work deserves all the recognition it can get. And as for school projects, I can really see it working. I am going to put it on the list of suggestions for my students next year.

I've got a friend that is a Mathematics Professor at The College of Charleston. He has published several papers with new discoveries in mathematics (polynomial zeta function gamma stuff). He's got some videos on YouTube but it literally sounds like Greek to listen to them, even though they are done in English! He could advise on the format, and you chemistry folks could edit the content. Is it possible to submit such a paper for publication? I'm no academic with just an undergrad degree in aviation from Embry Riddle. That would be cool!

https://www.youtube.com/watch?v=2i5PQiueW_8

I've not seen or heard of doing this process in this way any place. Especially the use of vitamin C to precipitate the gold. But I have only been refining precious metals as a hobby for about 5 years and then only at an amateur level.

I can't wait to get into refining platinum group metals and making some videos. There is MUCH more chemistry involved. I am particularly interested in the Gilchrist Hydrolysis of platinum where sodium bromate is used to form the hydroxides of the sister metals leaving the pure platinum "mother liquor" that can be drawn off and then precipitated into really pure platinum salt that is calcined in a fused Quartz dish to form pure platinum sponge. I've got everything to do it, just lack the know-how.

Colloidal gold is very pretty, but not very easy to collect (it goes right through even the finest filter paper). As recommended by deltaH, boiling during precipitation to coalesce the colloidal gold is new stuff to me also. Good stuff here. It has pumped new enthusiasm into my hobby, which was becoming sort of like work, or a job.

kadriver

kadriver - 11-10-2015 at 18:58

Here is a snapshot of the experiment after about 24 hours. It was crystal clear and blue in color. It turned cloudy after I stirred it. There are just a few gold foils that have been released from the fingers with the aerator in operation the whole time.

deltaH - 11-10-2015 at 21:02

You can actually substitute the lye which is corrosive with sodium bicarbonate, then it can become a junior lab project

Kid's love adding bicarb to vinegar after all!!!

The only purpose of the lye was to raise the pH of neat vinegar (~3?) a little higher to 4.5 by making some sodium acetate, but pH 4.5 is still acidic, so you can use much weaker bases to achieve it. Sodium bicarbofinate will work and generate much fizzing by making CO2. Washing soda (sodium carbonate) would also work and generate half as much fizzing.

The important thing is to get to pH 4.5-5 by hook or by crook

Remember, this is only an educated guess.

deltaH - 11-10-2015 at 21:27

Quote:

Colloidal gold is very pretty, but not very easy to collect (it goes right through even the finest filter paper). As recommended by deltaH, boiling during precipitation to coalesce the colloidal gold is new stuff to me also. Good stuff here. It has pumped new enthusiasm into my hobby, which was becoming sort of like work, or a job.

Some more on this... colloidal particles in a solution are kept from coellescing by charging up their surface so that the particles in solution repel each other electrostatically. Often this is done with an organic compound that absorbs strongly on the surface. Ascorbic acid, vitamin C, may well play this role.

But colloidal solutions are often metastable, so I'm hoping that heat, as with many metastable things, will shift it to a more stable state which is that of larger metal particles (in the same way that heat can collapse micelles, another type of colloidal metastable state).

I strongly suggest you do this on the test tube scale first to determine which conditions precipitates the gold nicely before doing it to the rest of the volume of your solution. Remember after boiling it for some time (I don't really know what is long enough, might be instant, might need an hour?), place it aside vertically overnight to see if it settles out. I also do not know how fast the settling will be, might even happen immediately as well, but if not, leave it overnight.

deltaH - 11-10-2015 at 21:35

[As an aside] While bulk gold is fairly inert, nanosized gold particles are very active catalysts for some reactions, typically oxidations. It's a classic example of the big differences that can occur in going from bulk materials to nano-sized materials.

[/end fact of the day]

kadriver - 12-10-2015 at 20:56

Please try to cut out HCl completely throughout, then we would have really accomplished something here. For the gold dissolution step, I strongly suggest you raise the pH of the salted vinegar BEFORE adding bleach with 0.2M sodium hydroxide solution to 4.5 so that one avoids the copious production of chlorine gas (hopefully).

You could finish off everything with an ascorbic acid reduction to make the process really Green and interesting. Like Bert showed, it's cheap stuff in semi-bulk scale.

I ordered 500 grams of ascorbic acid for the reduction. But I think there might be a problem with this.

The vinegar-salt-peroxide solution will have dissolved copper and possibly some other metals in solution with the gold after dissolving the foils with bleach.

The ascorbic acid will likely precipitate these other metals with the gold and thus contaminate the pure gold.

Not a problem, we'll just have karat gold instead of pure gold.

Or, I could do this;
1) prepare a fresh batch of vinegar-salt-peroxide (or just vinegar and salt)

2) add the thoroughly rinsed gold foils to the fresh batch of solution

3) raise pH to 4.5 with sodium bicarbonate to eliminate production of chlorine as per deltaH

4) dissolve the foils by adding bleach to the foils in the bicarbonate adjusted solution

5) precipitate the gold with ascorbic acid - boil to coalesce - settle overnight

6) collect the gold in a filter paper

7) melt the gold into a bead

I may try this procedure off camera with some pure gold powder just to see if it works. If I can't get it to work with some gold powder then it probably won't work with foils either.

If this off camera experiment with gold powder using the seven-step process above does work then I'll complete the video of the experiment with the foils.

But, if I can't get it to work, or if I have some other problem then I'll revert back to using HCl and bleach so that I can publish the video as scheduled (I've already put part one of two out there).

If anyone has any input then that would be greatly appreciated.

This evening at the 48 hour point the foils are about 65 to 70 percent lifted from the fingers (estimated). They will probably be ready by the 72 hour mark. I have footage of the bubbler at each 12 hour interval (4 shots so far) so the progress can be viewed during the video.

kadriver

deltaH - 12-10-2015 at 21:18

That's great kadriver. Rinsing the gold should eliminate the copper contamination (crosses fingers).

I'm very excited and hope it works for this will be first complete and videoed process using the OTC green reagents.

[Edited on 13-10-2015 by deltaH]

aga - 13-10-2015 at 11:11

Local Holidays are over and there are several parcels waiting in the local town.

Hopefully there will be some Gold !

For the non-videoed theoretical stuff, 2g of .999 gold will be available.

I'll cut it up a bit, but not more machining than that (as it takes a lot of time).

Suggestion: we take a 1 g bar, cut it in half and experiment on each 0.5g bar in turn to fine-tune the dissolution.
Elemental Copper and Tin can be aded to simulate more real-world applications.

Once tuned, cut the other bar in half and subject one to the new 'green' process and the other to aqua regia dissolution.

Melting the results back into gold lumps should not pose any problem.

Non-OTC Reagents avalable :

20% HCl
35% HNO₃ (can distill some 98% if needed)
NaOH
KOH
(plenty more, just not sure what is needed)

OTC stuff:

White vinegar : 8%
Sodium Bicarbonate

Sodium Metabisulphite is on hand for the precipitation plus borax (or is it boric acid?) for the melt.

For the 'fine tuning' i do not mind if the gold is lost, so we can cut the first bar down into 0.2g chunks (or less) and test the process at least 5 times if not 10, varying the parameters each time.

Over to you deltaH for the process(es) and ingredients.

deltaH - 13-10-2015 at 11:44

Place 40ml of acetic acid in a small beaker and saturate it with an excess of salt (sodium chloride). After stirring and allowing it to settle, decant the supernatant liquid into a clean flask. Drop in a small piece of pH indicator paper and raise the pH to 4-5 by mixing in spatula-tip-fulls of sodium bicarbonate, waiting for effervescence to subside between each addition. Gravity filter the solution if cloudy when complete.

Now cut approximately 1/5th of your gold 'bar' (~0.2g) with a pair of scissors and add to your beaker containing the previously prepared buffer solution. Then add 10ml of additive-free (perfumes, surfactants, etc.) household bleach and magnetically stir for an extended period of time.

Record detailed observations and depending on the results, we can devise changes as required.

We will need a comparative test with aqua regia, but that's for a later stage.

Thank you for your efforts aga!

[Edited on 13-10-2015 by deltaH]

aga - 13-10-2015 at 11:56

Additive free ?

Surely they ALL have additives.

We can only go with OTC bleach, so it will have to be the same stuff that successfully made chloroform (i.e has hypo in it).

deltaH - 13-10-2015 at 12:03

By us each brand has some 'plain' version that's just sodium hypochlorite and salt.

Baby sterilising solution is another way to go for simple sodium hypochlorite and salt, except the new chlorine-free ones based on dimethyldidecylammonium chloride. YUCH! Give me chlorine anyday

aga - 13-10-2015 at 12:09

OTC bottle of bleach it is then ...

Be aware that Baby sterlising solution is not intended for use on the actual Baby.

deltaH - 13-10-2015 at 12:15

lol

Little_Ghost_again - 13-10-2015 at 14:41

OTC bottle of bleach it is then ...

Be aware that Baby sterlising solution is not intended for use on the actual Baby.

That sounds as daft as car shampoo is not for use on cars

. So let me get this straight.... Baby bleach is bleach for beginners?

kadriver - 13-10-2015 at 20:49

Now cut approximately 1/5th of your gold 'bar' (~0.2g) with a pair of scissors and add to your beaker containing the previously prepared buffer solution. Then add 10ml of additive-free (perfumes, surfactants, etc.) household bleach and magnetically stir for an extended period of time.

Then check for the presence of chlorine gas evolving from the reaction?

I know that the prediction is no chlorine gas here, but, "making predictions is risky business - especially if it's about the future." - Yogi Berra. It is possible that you could start making chlorine gas. I'd have a plan in place to deal with it ahead of time just in case it happens.

I washed the blue precipitate from my previous experiment and to my surprise, found quite a bit of gold foils in the bottom of the container. I'm going to follow the procedure above using these newly discovered foils and see if I can get a result on video and post it.

I'll do the bleach reaction several feet from my "fume cupboard" as a precaution. If I start to smell chlorine I'll quickly move the reaction to the cupboard. If there is no chlorine smell then the experiment will be good to go.

kadriver

deltaH - 13-10-2015 at 21:35

Please, this must be strictly done in a fume cupboard before we can confirm that it doesn't evolve a lot of chlorine, not several feet from it.

Also, even if it doesn't evolve chlorine by bubbling, it might still smell strongly of it as there should be some in solution!

kadriver - 14-10-2015 at 03:14

In the fume cupboard - got it.

aga - 14-10-2015 at 05:06

Gold has arrived in the form of perfectly formed 1g ingots.

Now to damage, deface and dissolve them

kadriver - 14-10-2015 at 06:52

Gold has arrived in the form of perfectly formed 1g ingots.

Now to damage, deface and dissolve them

Dissolving the pieces of ingot is going to take much longer than foils as the foils are just microns in thickness.

MrHomeScientist - 14-10-2015 at 09:31

Remember that gold is extremely soft and ductile - you can easily flatten the ingots with gentle taps from a hammer on a hard surface. Then cut (or tear!) to size. Shouldn't be all that difficult.

Also ascorbic acid will definitely precipitate base metals. I did just that as part of a 'copper cycle' lab I did with local kids. At that point they had a solution of copper(II) chloride, and simply adding a solution of vitamin C causes lots of very nice looking copper powder to precipitate. So if there's any copper (or likely lead, tin, etc. too) contamination it will come down with your gold. Easily fixed with later purification I'm sure, but something to be aware of.

aga - 14-10-2015 at 11:03

40ml of 8w% OTC white vinegar was put in a plastic cup with a stirbar.

With stirring, NaCl table salt was added until no more would dissolve at room termperature (approx 25 C today).
At no point was Heating employed (plastic cup, duh !).

14.01g of NaCl was added in total.

The saturated vinegar/salt solution was poured off from the excess salt crystals.
Filtering was unnecessary.

The Stirbar was retrieved, washed and added to the liquid.

A digital pH meter was added and showed a pH of 1.8 at this time.
A wooden support was used to raise the pH meter to allow some space for the stirbar to move.

In small portions OTC (NaHCO₃) sodium bicarbonate was added until a reading of pH 4.5 was obtained.

4.60g of NaHCO₃ was used to achieve this pH.

10ml of OTC bleach was added.

Immediately there was a pungent smell which is exactly like that of dry TCCA, so probably a mix of HCl and Cl₂.

There was no bubbling or obvious gassing occurring, and the temperature did not change significantly (by touch).

A strip was cut from the gold ingot with tin snips.

The Au weight was 0.19g.

The strip is 0.40mm x 8.55mm x 3.33mm (approx - the cut is not too straight or clean).

With stirring, the strip was added to the solution at 18:17 local time.

We'll see what happens ...

[Edited on 14-10-2015 by aga]

deltaH - 14-10-2015 at 12:24

Quote:

Immediately there was a pungent smell which is exactly like that of dry TCCA, so probably a mix of HCl and Cl2.

There was no bubbling or obvious gassing occurring, and the temperature did not change significantly (by touch).

Excellent, this sounds perfect, looks like pH 4.5 is good then.

I'm worried that the acetic acid will be chlorinated because of the length of time this will take... well let's wait and see. Be warned that monochloro acetic acid is quite toxic, so don't let it touch the skin!

[Edited on 14-10-2015 by deltaH]

aga - 14-10-2015 at 13:43

Roughly 5 hrs have passed.

The gold bar was retrieved and dried on paper towels until no more water marks were seen.

The bar weight is now 0.16g so dissolution is proceeding at 21 C.

The liquid is now very much less pungent.

It might be that the Cl₂ is being lost as Gas in an Open setup.

Status Quo :-

deltaH - 14-10-2015 at 13:53

15% in five hours. Not too bad, it's a bulk piece of gold after all. I wonder what the pH is doing, but maybe your pH probe might get damaged by the chlorine in there.

Is it an optical illusion or is the solution noticeably light yellow like on the photo?

Well done, who would have EVER guessed that you could dissolve even bulk gold with things in your kitchen.

[Edited on 14-10-2015 by deltaH]

aga - 14-10-2015 at 14:03

The solution started a light lime green colour.

It is going more Yellow/Gold.

kadriver - 14-10-2015 at 23:50

I just got done with the dissolution of the recovered foils video part 2. I've got the pregnant gold solution ready to precipitate (see photo)

The video is being uploaded to YouTube as I write this.

I had to make this a three part video in order to get this posted this morning.

I don't have ascorbic acid yet, it's on the way.

When it comes in I'll do part 3 showing the precipitation with the vitamin C (ascorbic acid).

The blue precipitate showed up again, I must say it does muck things up a bit. I don't think I'd use this process again because of the precipitate that forms on day 4 or 5 of lifting the foils. It makes the process cumbersome extra long (not easy for a novice to deal with it).

But it was fun doing it for this video - it was 3 AM when I left my shop and I had to force myself to leave!

I used deltaH's process outlined above but scaled up to accommodate a full gram of pure gold.

That green color in the gold bearing solution usually indicates copper, nickel, or iron. I have some potassium thiocyanate that I can use to test the solution after the gold is dropped.

I must say that this video would not have been possible without the gracious help given by deltaH and aga - Thank You!

kadriver

kadriver - 15-10-2015 at 00:00

OK, here is part 2 of 3:

https://youtu.be/TUxJ0YhATxM

kadriver

aga - 15-10-2015 at 00:27

Brilliant !

deltaH - 15-10-2015 at 01:34

Wow kadriver, that was SO interesting! Great job :cool:

You know what? Now that I see it in all its glory, that cyan precipitate looks a helluva lot like copper hydroxide

Perhaps the pH climbed too high over the course of the whole dissolution and then it started precipitating. You might try putting a little in a test tube and see if it dissolves in an excess of ammonia to form a clear deep blue solution, the copper tetraamine complex.

As for recovering that copper, you could maybe filter it under suction to concentrate it with a fine filter, then redissolve the resulting slime on the filter paper in just enough HCl to do the job. Then you could boil it with ascorbic acid to reduce to copper metal.

When you do the copper reduction, use an excess of ascorbic acid and really boil down the solution so that you can reduce the maximum amount of it. Don't worry about the reduced ascorbic acid crystallising when you boil it down, when it's done, just wash everything with water and it will redissolve. I think the poor yields people get with copper reductions and ascorbic acid is because towards the end, the concentration of copper and ascorbic acid is low and so the chemical kinetics is too slow, but if you boil it down, you keep concentrating it so it should drive it up an give decent yields.

Very nice and well done again!

deltaH - 15-10-2015 at 03:39

Copper chloride salts can also precipitate as a mixed copper chloride - hydroxide material, namely dicopper chloride trihydroxide, but this is described as being slightly greenish.

https://en.wikipedia.org/wiki/Dicopper_chloride_trihydroxide

Maybe there's an acetate version.

UPDATE: Indeed there is, see this paper:

http://onlinelibrary.wiley.com/doi/10.1002/crat.201100262/ab...

[Edited on 15-10-2015 by deltaH]

aga - 15-10-2015 at 03:50

Copper acetate maybe ?

https://en.wikipedia.org/wiki/Copper%28II%29_acetate

Seems historically it was made with acetic acid & copper sheets.

deltaH - 15-10-2015 at 03:52

Copper acetate is reasonably soluble, hence why I suggested a mixed hydroxide, much more insoluble. Damn those crystals are pretty!

Hmm... maybe it is just the acetate after all if the vinegar precipitates it.

Either way, HCl should dissolve it quite quickly.

[Edited on 15-10-2015 by deltaH]

Little_Ghost_again - 15-10-2015 at 04:00

At around 1.11 in the video I see a large ring of deposit around the beaker, could it be with the bubbling as it dries on the side of the beaker you are altering the chemistry?
You might be able to avoid the precipitate with some kind of pH control like dosing pump? Or simple very slow drip rate

kadriver - 15-10-2015 at 06:52

I'll be heading to my shop after all-day appointments with ascorbic acid in hand.

The process used to dissolved worked perfectly.

What would be the procedure for precipitating the gold with the vitamin C?

deltaH - 15-10-2015 at 07:39

You probably know most of this, but for others who might read it for the first time, I'll be more detailed:

Work out how many moles of gold you have in solution (I'll leave that as an exercise for you

). You need a minimum of 1.5 times this of moles of ascorbic acid to reduce it, but I'd say use 2 to have an excess and make sure the ascorbic acid doesn't limit the reduction, it's cheaper than gold after all

The molar mass of ascorbic acid is 176g/mole.

People normally dissolve the ascorbic acid in a minimum amount of water (it's solubility is about 33g/100ml water) and then add this to the metal salt solution with stirring, then boil for a while, then leave to stand to settle out.

Not so sure if this predissolving of the ascorbic acid is necessary, I'd add it straight in under stirring and then boil the solution.

After recovering your gold, check that the filtrate doesn't contain any dissolved gold with stannous chloride NOR that it's coloured. A coloured solution might contain colloidal gold yet give a negative test for gold with stannous chloride!

PLAN B: If for some reason your gold doesn't settle out but remains as a coloured solution, then boil the solution right down to get a dry solid. You can then scrape the solids out and simply burn off the reduced ascorbic acid containing the metallic gold in the crucible with a torch (it will char first but then quickly burn off to nothing). The reduced ascorbic acid molecule is sugar-like so it will char to carbon and then burn quite easily. Bert even commented that you can use it as solid rocket fuel

[Edited on 15-10-2015 by deltaH]

deltaH - 15-10-2015 at 07:56

Oh forgot to add, after adding the ascorbic acid the gold solution, if you don't see an immediate colour change, try raising the pH with sodium bicarbonate to about 7, but I doubt this will be necessary.

kadriver - 15-10-2015 at 23:52

Part 3 of 3

Thanks to you guys for helping me with this video!

https://youtu.be/CAhh6p4E6-I

kadriver

deltaH - 16-10-2015 at 01:42

WOOOOOW I can't beleive the ascorbic acid works so well. I'm now happy for you that you bought a bulk bag of it!!!!!

Very nicely done kadriver! Pro video as always.

I think this is a first ascorbic acid reduction of gold on youtube AFAIK. Hopefully you'll get some extra viewership. Crossing fingers.

Thank you for the acknowledgement, I'm really honoured!

[Edited on 16-10-2015 by deltaH]

deltaH - 16-10-2015 at 01:45

Looks like aga was right, that precipitate behaves like copper acetate, well done aga, you win 50 kudo's, don't spend it all at once

Kadriver your recovery was 20% less this time, do you think this was because of gold not recovered properly by the process or just less gold to start with in the fingers?

[Edited on 16-10-2015 by deltaH]

kadriver - 16-10-2015 at 04:28

Kadriver your recovery was 20% less this time, do you think this was because of gold not recovered properly by the process or just less gold to start with in the fingers?

Good observation. It is because there is still much gold foils left on the fingers. If the fingers had been left in the bubbler longer then the yield would have been much higher, in fact possibly up around 1.1 to 1.2 grams.

The first batch I did, where I broke the 5 liter beaker, had actually continued to bubble for about three more days AFTER the thick precipitate showed up. I just let it go for lack of knowing what to do next.

Then, after I removed the air hose, the fingers spent another 5 days just sitting in the precipitate until the beaker got broken, then ANOTHER day or two until you emailed me asking about it!

The result is the one gram of pure gold that I got from the strainer from the broken beaker, PLUS another undetermined amount as unprocessed loose foils still sitting at my shop, would have totaled well over 1 gram.

The yield from part 3 in this video only spent 90 hours (less than 4 days) in the bubbler. That is why I only got 0.8g of gold. There is probably another half gram or so left on those fingers. I saved these fingers and will process them in acid peroxide until I get 100% of all the gold - I'll let it go until each finger is totally stripped of gold.

I hope I've made it clear why this video part three yield was lower - it's because the fingers where not allowed to bubble longer which left foils attached to the fingers.

I have learned so much from processing the fingers in this way. I was going to just go ahead and use copperas (ferrous sulfate) to precipitate because I was ready to drop the gold but the vitamin C had not arrived - I'm glad I waited and followed the process you had in mind. I'm still wondering how in the heck you came up with it!

There has been a tremendous gain in experience and knowledge for me from this and I owe much to you and aga - Cheers!

kadriver

kadriver - 16-10-2015 at 04:35

Looks like aga was right, that precipitate behaves like copper acetate, well done aga, you win 50 kudo's, don't spend it all at once

I agree. If I had to do this over again, I would just add enough HCl to dissolve all the precipitate, then quickly and easily filter out ALL the foils into a coffee filter.

kadriver

kadriver - 16-10-2015 at 06:46

Adjusting pH was done to minimize or eliminate chlorine gas when adding the bleach. It would be nice to know if buffering the solution prior to adding the bleach worked to eliminate chlorine gas.

How can I test to see if it worked?

kadriver

aga - 16-10-2015 at 07:57

Smell it ! Chlorine has a distinct and strong smell.

Waft some of the air above the beaker towards you - don't just dunk your schnozzle right in there and take a big sniff.

Loving the videos.

Great job kadriver !

Edit:

I tend to wet some pH paper and stick it in the air in the pot to see if there's anything 'gassy' happening in there.

If there's enough Chlorine or HCl coming off, it'll go pink/red.

[Edited on 16-10-2015 by aga]

aga - 16-10-2015 at 07:59