# Melting e-scrap in an arc furnace



## HDTVinc (Oct 11, 2016)

Hello all,

I am relatively new to this whole procedure, however I have a lot of experience working in labs and the like. I have an arc furnace, capable of melting steel in seconds, and I was wondering if anyone had ever used such a furnace to melt down e-scrap so that all of the metal components form a bead. I have not tried this myself yet, but I do not know why it wouldn't work. Once I have metal buttons, I would use a cyanide bath to remove any precious metals. 

Does anyone have an opinion on this approach?

Thank you so much for your time.


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## nickvc (Oct 11, 2016)

Welcome to the forum.
You have a lot to learn I'm afraid to say, if you mean whole boards then you are in danger of poisoning yourself or neighbours, if you mean gold plated components then unless you have a way of seperating and collecting the base metals as well as the values you are up poo creek.
The idea of using cyanide on melted metals is a no no, on plated scrap yes, if you melt all the metals together you are heading for a very large mess as a home refiner, if as you say you have worked in laboratories then start reading here and learn the best ways to recover and refine.


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## 4metals (Oct 11, 2016)

The reason melting the material into an ingot is not a good idea is surface area. If you were to incinerate or pyrolyze the boards first and end up with powdered ash and metallics you would be better served to leach the individual metallic scraps taking advantage of their surface area. If you make it one block you have just shot yourself in the foot. And even if you pour it into shot to increase the surface area, the chances of the values being so embedded in the other metals may mask them from your selected leach. 

I do not know if this is possible but if an arc furnace could be used in an oxygen free environment, you could use it to pyrolyze the boards, don't know if anyone has tried that method yet.


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## HDTVinc (Oct 11, 2016)

Thank you very much! This is one of two methods that I had thought about, so you have helped me to determine that the second is a much better choice. I will make a separate post about the other method as it is much more complicated that this one.


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## anachronism (Oct 11, 2016)

Please feel free to post it on this thread as it will keep it all in one place.


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## HDTVinc (Oct 11, 2016)

The second method that I had thought might work utilizes glow discharge of an inert gas, like helium, in order to selectively make precious metals, and lead, fall out of solution in their elemental form. 

I read an article, http://pubs.acs.org/doi/abs/10.1021/acssuschemeng.6b00305, in which floating Au/PVP films are produced by exposing the surface of a liquid to glow discharge in a vessel. This process reduces metals with a high reduction potential like gold, silver, platinum, and lead, and does so quickly. If you had a solution with gold, silver, and platinum dissolved, then you could selectively make each fall out, one at a time, and each would fall out of solution as tiny nanoparticles. The liquid could be monitored for a change in the appearance of particles falling out of solution in order to determine when gold vs silver vs platinum is falling out of solution. 

If you had a solution with all three metals present, you could expose the liquid to glow discharge until the particles change the first time. You could then filter the solution, collecting any solids which were produced, and all solids collected would be gold, with a tiny bit of platinum. 
You could then repeat the process with the liquid, however the solid would then be platinum, with a tiny bit of silver. Finally, you could repeat the process a third time to recover nearly pure silver. 

Each filter could be washed several times with distilled water, and the filter, as well as the solid could be incinerated with a little bit of borax. This should result in three beads, one of platinum, one of gold, and one of silver. 

While it is possible to have one solution with all three present, this would really only be used for one metal at a time, so I would never actually add all three metals to one solution. 

my question to the community is, has this process been used for this purpose before? Has anyone been successful? 

Thank you very much for your time.


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## nickvc (Oct 12, 2016)

I quickly read your second idea and no disrespect why try and reinvent the wheel.
Your first problem is getting all the metals into solution this is going to consume a lot of acids and to what end, if you selectively dissolve the values it uses less acid and produces better final product and there are many ways to remove the values from the solutions that are known to work and are fairly cheap.
With a mix of metals in solution especially tin you are creating a nightmare solution, look up stannic acid and it's love of gold.
My advice study and read here to understand why we do certain things in certain ways, some processes work for one type of material but are useless for others but you need to know why. If your looking for a fast simple method to do this then your wasting your time and ours, it doesn't exist, if it did we would be all over it, of that you can be sure.


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## g_axelsson (Oct 12, 2016)

Interesting article about glow discharge reduction but utterly useless for refining. At least for now.

It is another article written by a scientist who doesn't know how the craft of refining is done in reality, only comparing his numbers with other publications.
I have a hard time to see how glow discharge in a low pressure argon atmosphere could scale up from a petri dish experiment to real life scenarios.
Other methods are smelting and then running a copper cell, from leaching ore you could use carbon in pulp and for various fluid medias we could use liquid-liquid extraction. All these methods are easy to scale up and is used in working plants.

As I read the article it sounds like a simple electrowinning cell would work just as great and be even simpler to scale up. For example the carbon felt cell that Jon built with the help of Deano.

With that review of the article done, I'd like to welcome you to the GRF. Here you will find answers on virtually every question you might have, it just takes some digging to extract it from the quarter of million posts we have here.

Göran


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## Lou (Oct 12, 2016)

Likely useless except in systems with very high turbulence where effective mass transfer is possible.


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## HDTVinc (Oct 12, 2016)

Glow discharge was used for reduction of precious metals around the time it was first discovered. But it was harder to achieve the conditions at the time. I will do independent testing and see if I can make a working apparatus. Please accept my apologies for being a noob. 

I know that this process would use lots of acid, but I have access to acid, and I plan on refining as many metals as possible, even the copper. Not necessarily to make a profit, but to use in other projects.

Thank you for your time.


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## g_axelsson (Oct 12, 2016)

I don't get it, what is so hard about mixing a teaspoon of white powder with a pregnant solution and in a minute having the gold powder ready for washing. I don't need an elaborate vacuum device with high voltage generator to form a floating film of impure gold that would still take more work and refining until I have a decent product.

... maybe it's too simple to do as every one else is doing. :roll: 

Göran


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## HDTVinc (Oct 12, 2016)

I'm specifically looking for catalytically active particles. Sorry I didn't really make that too clear in past posts.


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## g_axelsson (Oct 12, 2016)

HDTVinc said:


> I'm specifically looking for catalytically active particles. Sorry I didn't really make that too clear in past posts.


Exactly what do you mean by that? In your first post you mention e-scrap, not catalytic material.

Göran


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## HDTVinc (Oct 12, 2016)

The local university uses catalytically active gold in numerous research projects. As far as i know, this sort of research is fairly popular, at least here in the states. The local university pays something like $50 USD for 25 mL of 0.05 mg/mL solution. Meaning they are paying $50 USD for 1.25 mg of gold. 

the article that I mentioned earlier in the posts shows the process for making PVP films, but it really will embed itself onto most carbon containing molecules, and even activated carbon. It can also be produced without being embedded as free floating particles. I thought if i could get the process down, I could give them a much better rate. I may just be dreaming, but it seems like a LOT of profit could be made in that front. BUT, even if doesn't wind up being the gold mine that it seems to be, I am very interested in working through this process to see if other metals exhibit catalytic activity. Meaning they act similarly to the platinum in catalytic converters.


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## g_axelsson (Oct 13, 2016)

Good luck with that, that's advanced chemistry.

Göran


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## HDTVinc (Oct 18, 2016)

Thanks.

I am fairly sure that this process should work with HCl acid and H2O2. This will produce HAuCl4, which contains an Au3+ ion, which then gets reduced by the electrons from the glow discharge. The resulting Au2+ isn't very stable, so it auto dissociates into Au3+ and Au+. Au3+ gets cycled again, and Au+ is reduced again to produce elemental gold. 

I cant use Nitric for this process, because once the gold falls out of solution, it would essentially just react with the AR and I would be back where I started, but i'm thinking that as long as I allow the H2O2 to evaporate off, I shouldn't have this problem. 

I am thinking about putting crushed up bits of IC chips gold fingers all in one large container, taking care to remove as much non-metalic bits as I can along the way, and dissolving all of the metal content in HCl and H2O2. I will have to replinish the H2O2 a few times, but that should get the job done hopefully. I know that HCl and H2O2 are NEVER used on raw e-scrap, because you would generally need to remove the copper and what not from the scrap before you tackle the gold, but the beauty of the glow discharge is that it is so selective in removing gold from the solution. 

Now all I have to do is get a vacuum pump, and figure out what gas to use.


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## mls26cwru (Oct 18, 2016)

what kind of vacuum are you looking to be operating at? Are you talking about RF plasma like used in plasma enhanced chemical vapor depositions? It almost sounds like you are describing an argon sputtering system.

If you are thinking about putting a liquid into those kind of low vacuums you are going to run into problems as you will boil off (rather violently) your solutions. RF Ar sputtering can be done at some higher pressures, but I know the higher the pressure you operate at, the higher the power output is needed the RF power supply, so you could be talking about some pretty heavy duty pieces of equipment.


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## HDTVinc (Oct 18, 2016)

I would only need a very small amount of suction to be on the vessel. Just enough to make the pressure within the tube less then ambient pressure. This helps with initiating glow discharge, rather than an arc being struck whenever power is supplied to the system. the current supplied to the vessel needs to be in the mA range, and the voltage should be in the 100V+ range. As far as i understand it, smaller particles are produced whenever the ratio of V/I is very high, so the higher the voltage, and the lower the amperage, the better the results should be. I would have to purge the system a few times in order for this to work, because i have a suspission that any nitrogen may be converted to a bit of NO and NO2 whenever the glow discharge is going. Im not 100% sure if the presence of nitrogen gas would do much, but it may reduce yields, as NO2 could get into solution and create small amounts of Nitric acid. 

I don't know much about the sputtering that you mentioned, but from what I found with a quick google search they a much different, however you may be able to combine the ideas of both in order to plate things with very small layers of gold which could be cool. 

I could probably get away with rigging a shop vac up in order to produce the level of suction that is needed, as it would hopefully be just strong enough to induce glow discharge rather than the production of an arc. It will be a bit of trial and error on my part to figure that out.


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## kurtak (Oct 19, 2016)

HDTVinc said:


> I could probably get away with rigging a shop vac up in order to produce the level of suction that is needed, as it would hopefully be just strong enough to induce glow discharge rather than the production of an arc. It will be a bit of trial and error on my part to figure that out.



Per the above underlined -----------

Go to Harbor Freight & get a vacuum pump - they sell them for evacuating refrigeration & air conditioning systems - they have two CFM sizes & when they are on sale they sell for $100 - $150 --- if I remember right (off the top of my head) the small one is 2.5 CFM & the bigger one is 3 CFM

You can then get a vacuum gauge to hook up in line along with a bleeder valve to adjust the vacuum to the desired vacuum you want

Here is a pic with the vac pumps from Harbor Freight

:arrow: http://goldrefiningforum.com/phpBB3/viewtopic.php?f=40&t=19965&hilit=scrubber#p205136 

Kurt


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## HDTVinc (Oct 22, 2016)

Thank you so much for the information! I will definitely be getting a vacuum gauge to see what kind of suction i am getting. Thank you all so much.


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