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gold fever mr behemoth?
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Nick



Joined: 02 Nov 2004
Posts: 33660
Location: Hereford
PostPosted: Wed Nov 18, 15 12:19 pm    Post subject:  Reply with quote    

Behemoth wrote:
The best place to start recycling is the design and construction phase.


From a global perspective, yes.

However, if you're a site manager with a degree in chemistry, a stack of waste, a massive chemistry set, someone else's budget, an enquiring mind and no supervisor on site, Chris' office/lab is a close second.

dpack



Joined: 02 Jul 2005
Posts: 32882
Location: yes
PostPosted: Wed Nov 18, 15 12:41 pm    Post subject: Reply with quote    

yep get the planning correct and the result follows

the aqua regia route does seem to be the best way to get noble metals into solution and therefore recoverable.

teflon here we come

afaik the stuff eats incaloy and hastaloy so my metals of choice are a non starter,glass is too probably too fragile for industrial scale,i spose there are suitable ceramics but teflon coating seems a promising option.

my next thought is how to transfer batch tech into a continuous process with as much recycling of reagents as possible and acceptable waste protocols.

spose something a bit similar to the engineering of thorp without the obvious extra problem they have might work.different chemistry but basically a similar process chain .
mixed solid,dissolve the metals,neutralise,collect the bits you want ,repackage the waste.

it cant be as difficult as never being able to maintain the plant unless you use a robot:lol:

Mistress Rose



Joined: 21 Jul 2011
Posts: 8726

PostPosted: Thu Nov 19, 15 6:59 am    Post subject: Reply with quote    

You can't design all electronic components to be recycle friendly. I used to work in the industry and just at the basic board level then there were PCBs which were generally copper and gold with some intervening nickel or similar on plastic, thick film, which is a mixture of glass and metal printed onto ceramic, and thin film which is a thin layer of gold and nichrome plated up and again on ceramic or glass. Then you get the plating and base metal on the legs of components, solders etc.

I am sure it is quite possible to extract the metal from this, which is a potentially rich ore, and then refining them into individual metals, but an interesting chemical challenge to start, and then you have to make it economic. From the point of recycling, it is certainly worth while, but making it economic is another thing.

dpack



Joined: 02 Jul 2005
Posts: 32882
Location: yes
PostPosted: Thu Nov 19, 15 10:14 am    Post subject: Reply with quote    

separating the metals can be as simple as burning them in a bone ash dish ,cupellation has been used since the bronze age ,the oxidisable stuff burns and the dish absorbs the oxides leaving very pure gold (99% +).i have done this with scrap 9ct and got it well above 22 ct.burning zinc out of yellow 9ct is a bit nasty and 9ct redish has a bit of a problem with copper "freezing" on the edges of the liquid gold if the temp isnt quite high enough ,this requires a bump in temp and some stirring to get the copper back in "solution" so as it oxidises.

the roman way to get precious metals(silver) from lead uses a series of crucibles at decreasing temps and a ladle to move the liquid stuff towards cool( using the principle causing the copper problem above)and moving the solid bits back to the hottest part of the series and repeating the process until the centre pot is very pure silver.im not sure if there is evidence of from viking scandinavia of them using this method but the silver in viking decorative work and hack silver "coinage"is often 99% so they definately had some good refining methods.

etc etc .

once one starts to play with acids to make solutions ,chelating agents,cyanide and electricity the possible isolations are such that most metals can be seperated.

if we are considering gold,platinum,palladium,rhodium etc etc the economics are such that a fair bit of effort will still turn a nice profit

avoiding poisoning the staff and locals is probably the biggest problem

Mistress Rose



Joined: 21 Jul 2011
Posts: 8726

PostPosted: Fri Nov 20, 15 7:06 am    Post subject: Reply with quote    

The cost of the different metals will decide whether it is economic Dpack, and as you say there are various methods of separation and refining, but the health and safety is of paramount importance.

I hadn't heard about the silver refining. I knew that gold was separated by removing all the dross at high temperature, and that quite a lot of this would have been other metals as oxides.

dpack



Joined: 02 Jul 2005
Posts: 32882
Location: yes
PostPosted: Fri Nov 20, 15 8:45 pm    Post subject: Reply with quote    

there are chemical followed by electro chemical ways to isolate gold (and other noble metals)from a mix as well.

the mercury amalgam method has some merit for concentrating from a mostly not metal "ore"(especially as the mercury can be recycled) but it does take up quite a few metals so there is still the refining/seperation to do.

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