# need help seperating gold flakes from coarse al2o3



## andycourson (Nov 30, 2008)

hi everyone this is my first post. I have big jar filled with coarse aluminum oxide and gold flakes. this came out of a shop vac used to suck out used al2o3 and all particles / flakes from a vaccuum deposition chamber. 
I already used a kitchen type strainer screen to sort out all the dust and small flakes. what remains is flakes mixed with coarse al2o3. does anyone have any ideas how I could seperate the flakes out without having to use alot of acid. :?:


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## Platdigger (Nov 30, 2008)

If it truly is aluminum oxide, it will be impurvious to most acids.

Therefore, you could go after the gold just about any way you want to.

Randy


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## andycourson (Nov 30, 2008)

yeah it is pure al2o3 it gets evaporated in a vaccuum to form insulators on an electronic substrate. i could put everything in ar to get the gold but i dont want that much volume of ar.


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## Platdigger (Nov 30, 2008)

Have you tried to pan it?


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## Harold_V (Dec 1, 2008)

andycourson said:


> i dont want that much volume of ar.


Have you considered using dilute AR and heating? You need not use a great deal of acid, just a considerable amount of water. It will work slowly, but that way you can avoid the excess acid. You're going to end up with a fairly large volume of water, anyway----when you rinse the dissolved gold from the aluminum oxide. I see some evaporating in your future, regardless of the direction you choose. 

If the gold particles are quite thin, you'd enjoy success with cyanide, too. 

Harold


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## Platdigger (Dec 1, 2008)

One way you may be able to limit the amount of liquid involved would be to set up a small leach column.

Just a piece of pvc pipe with a plastic screen small enough to hold back your media.

Pump your leach (dilute AR or what) to the top, and let it flow through and back to your pump.
Randy


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## DNIndustry (Dec 1, 2008)

I think you have something else...
Aluminium Oxide -> Alumina is how they mine Al

They electrolysize it. The O3 is cleaved off leaving molten aluminum. Its white, granular, and extremely fine. Between sand and talcum powder


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## Platdigger (Dec 1, 2008)

OK, but how does this help Andy?


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## DNIndustry (Dec 1, 2008)

where did those crystals come from or develop? What was your gold source material you were working with?

->save him from wasting time if it is not.


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## Bernie Foley (Dec 1, 2008)

Hi Andy&friends,
I think Harold has the answer.It appears that alot of the gold is plated or deposited onto the material. Some would come out by panning it.
It shure looks like a shower of AR would be the way. Alumina so called can be made to any size you would like if you can afford it. If the material
was from a sputtering type machine or a coating machine of some sort the
grade of the gold maybe alloy if it is it was very pure to start with.
Good luck Andy and welcome to the forum!!....Bernie


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## Lou (Dec 1, 2008)

That is likely very pure alumina and is impervious to many acids. Cyanide would work a treat on this. Also dilute AR. Harold gave good suggestions. If you really don't want to deal with nitric, you can simply use HCl-H2O2. You have very many options.

This is also a case example when gas phase extraction would be extremely convenient.


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## andycourson (Dec 2, 2008)

oh yes the gold we evaporate at my company is 5 9s pure. we e-beam evaporate CdSe, Al, NiV, Au, and al2o3 all in the same chamber. this builds up and starts peeling on the inside walls and shields of our vac chamber. this gets scraped and then sand blasted. The scrappings i save and have already recovered over on ounce of gold from them. see the pics. 
I first gave everything a Hcl bath. then rinsed and filtered every thing, oven dried, then let AR do the rest of the work. filtered with a homemade vac filter (very close to the one in the back of the GRF hand book) neutralized with urea then dropped with smb. and melted in electric furnace with graphite crucible. then after it solidified transfered to cupel, remelted, then poured off into bucket of water to make cornflake. just thought i would share and would love some feedback. 

I have been lurking the forum for weeks now and just cant stop absorbing all of your wisdom. :wink: All of you have such great knowledge and I thank you. I think I will try what harold sugested with alot of dilute AR I will probably split up the mixture in two batches to make it more managable.

something else I have been wondering is if the CdSe has also been digested with the AR or was it with the Hcl bath. the reason I ask when I melted the gold initially there was a brown powder (very close aperance to the gold powder) that would not melt with the rest of the gold. after looking at all the ingredents all the other metals would have been gone in the hcl bath right? if this is so than if the cdse did not go with the first bath, but dig get digested in the AR than did it precipitate out with the gold? 

Also the filtering rig I made is with a 5 gal bucket with a pvc parts funnel arangement. the funnel has a 1" tube that goes almost all the way down to the bottom. there are two ports in the top on either side of the funnel one for vac the other to relieve the vac pressure. this works great if you are filtering after the hcl bath. but when it comes time to filter the auric chloride :lol:  :shock: (awesome stuff, great color, really cool to watch change from yellow all the way up to dark orange) the filter shows its weak spot. the liquid in the bucket just splatters all over the inside and top. and can even get sucked into the vac  . this just wont do. Any sugestions :?: :?:


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## andycourson (Dec 2, 2008)

hear is the pic


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## andycourson (Dec 2, 2008)

Also there was considerable amount of Al in the mix from the shop vac. i screened the mix in a kitchen screen strainer. and all of the mix was digested in Hcl last night and it almost boiled over a couple of times due to everything being fine powder. There was also alot of organic dust and such that made a slimey mess that floated on top of the mix. I read here that the slimey stuff was actually aluminum hydroxide? anyways that was very messy and hope to get around that some how next time. any sugestions how I should proces this further, maby to eliminate the Cdse?

Then there is the matter of the 55 gal drum of used sandblasting media also al2o3 just not as pure and finer. I know this has alot of gold in it, but it also has mostly sand. when we scrape off the deposited material it is just real quick so big flakes dont clog the pickup tube in the sand blaster. (this will change now that i know how much gold is going to waste we will scrape much more). this barrell is full and has been collecting for years.
I would love to get back all that gold but dont know where to start. :?:


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## Harold_V (Dec 2, 2008)

I'm not sure if HCl dissolves Cd, but I'm inclined to think it does. I am not a chemist.

Unless the picture you posted has extremely bad color balance, there's something wrong with your gold. It should have a bright yellow surface----exactly like the picture I'll post, below. While I don't claim 4N's quality, I'm confident what you see is far better than 3N's. The gold in the picture was melted sans flux, aside from a light coating on the dish, to prevent gold from sticking. It was not pickled, the color you see is the color of the gold as poured. Yours should be the same. Any darkness is a sure sign of contamination. 

I advise you abandon the filtration of gold chloride via vacuum. It's too easy to lose some that way. I routinely used a Whatman #2 to filter my gold chloride solutions, using a Nalgene funnel, which accommodated 32 CM papers. The only exception is when I filtered gold that was refined a second time, in which case I used a Whatman #5, same size. I allowed only gravity filtration for these solutions to avoid any losses. My vacuum source was a water powered evacuating pump, so any losses went down the drain. If you have a catch chamber and prefer to continue the coarse, you'll probably be fine. Just insure that you can't lose the values. 

On that subject, if you have done your home work, the solutions you filter will not have issues with filtration, so gravity serves your needs perfectly well. There are washing procedures that can be employed to assure that solutions will filter. A hard boil in HCl before dissolving gold is one of them, although it should be accompanied by at least two rinses with tap water, each of which, along with the HCL wash, are decanted, not filtered. 

Harold


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## andycourson (Dec 2, 2008)

yeah mine looks just like that. but I was having trouble taking a good picture, it is a dark pic


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## andycourson (Dec 2, 2008)

harold that is quite a "pot o gold" it is beautiful. how much is in there, and did you find it an the end of a rainbow :?:


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## Harold_V (Dec 2, 2008)

I don't recall the amount that was placed in the bowl, but it's a common household one, about five inches in diameter. I'd suggest there is about 20 ounces or so. 

In a sense it was found at the end of a rainbow. I processed all my waste materials towards the end of my refining career and recovered in excess of 200 ounces of gold. That represented more than 20 years of gold refining, commercially. 

Harold


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