amaaamy2
مشرف قسم
انا من بلده : china
 عدد المساهمات : 744
نقاط : 29459
السٌّمعَة : 106
تاريخ التسجيل : 04/07/2010
 |  موضوع: Process of Gold Extraction from Motherboards--عملية استخراج الذهب من لوحات الأم aditional الأزياء  الأحد يناير 09, 2011 8:28 am | |
| It
seems like too much work for so little gold. Even when gold prices hit
record high. But it's still very interesting. Let's see how to extract
gold from old motherboards.
Gold
is found in numerous places on a motherboard: IDE connectors, PCI
Express slot, PCI, AGP, ISA, and other ports, jumper pins, the
processor socket, and DIMM (SIMM on older motherboards) slots.
All of these connectors are often covered with a fine layer of gold a few microns thick, deposited by flashing or plating.
So,
the first stage of the experiment is to recover all these pins and
connectors. We need pliers and cutters, flat and Philips screwdrivers,
and liberal amounts of elbow grease...
You need a lot of pins to conduct this experiment, and that's exactly what our donor boards provided...
along with some equipment and chemicals 
To
recover the few micrograms of gold deposited on the pins, we're going
to use an electrolytic cell. The bath consists of a 95% solution of
sulfuric acid. The cathode is lead and the anode is copper. The pins
are placed in the copper anode, which we've formed into a basket shape.  By
running an electrical current through the cell, using an ordinary
battery charger, the copper in the anode (and in the pins) dissolves
and is deposited on the lead cathode. The gold, detached from the
copper, forms a sediment at the bottom of the cell. Also note that the
temperature of the bath increases significantly during this process.  Once
all of the gold has detached from the pins, the bath is allowed to
settle. Then, we recover as much of the sulfuric acid as possible,
before diluting what remains in the bottom of the electrolytic cell.  Be
careful to always pour acid into water, and not the other way around!
If you do it wrong, the first drops of water that touch the surface of
the sulfuric acid will immediately be vaporized and could cause acid
splashes.  We
end up with a diluted solution of sulfuric acid, various metals
(including gold), and waste that then needs to be filtered. Why not
just filter the solution directly, without diluting it? Because paper
filters don't stand up well to strongly concentrated sulfuric acid.
That's why.  What
remains in the filter is a mixture of various metals and impurities. We
now dissolve everything in a mixture of hydrochloric acid at 35% and
chlorine bleach (sodium hypochlorite) at 5%, in a proportion of 2 to 1. 2 HCl + NaClO -> Cl2 + NaCl + H2O  Careful!
The reaction is highly exothermic and produces chlorine, a highly
dangerous gas. Chlorine gas was used as a chemical weapon during the
first World War, under the name bertholite.  In
fact, the chlorine produced by mixing hydrochloric acid and chlorine
bleach is what will dissolve the gold to form gold(III) chloride. 2 Au + 3 Cl2 -> 2 AuCl3
Now,
all we need to do is filter everything once again. The filter will
retain all the impurities, leaving only a gold(III) chloride solution.
To
recover the metallic gold, we now need to precipitate the gold that’s
in solution. For that, we use powdered sodium metabisulfite. In the
presence of water, the sodium metabisulfite produces sodium bisulfite.
Na2S2O5 + H2O --> 2 NaHSO3
This sodium bisulfite is what will allow the gold to precipitate.
3 NaHSO3 + 2 AuCl3 + 3 H2O --> 3 NaHSO4 + 6 HCl + 2 Au
We
let the solution settle, then we recover the brown powder collected at
the bottom of the beaker. We have to be careful not to lose any--that's
metallic gold!
Now, all we need to do is to melt the powder in a crucible.
The melting point of gold is around 1064° C (1947.52 °F), so an oxy-butane torch will do the job.
And here's the result!
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الثعلب
المراقب العـــام
انا من بلده : مصر
  
عدد المساهمات : 2492
نقاط : 35251
السٌّمعَة : 554
تاريخ التسجيل : 31/07/2010
العمر : 34
الموقع : www.shbabpolak.7olm.org
| | موضوع: رد: Process of Gold Extraction from Motherboards--عملية استخراج الذهب من لوحات الأم aditional الأزياء الإثنين يناير 10, 2011 10:20 am | |
| thank you  | |
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