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Message: <blockquote data-quote="shiyan_786" data-source="post: 8186797" data-attributes="member: 184072"> Process of Gold Extraction from Motherboards 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. <img src="http://acidcow.com/pics/20100829/gold_extraction_from_motherboards_01.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /> 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. <img src="http://acidcow.com/pics/20100829/gold_extraction_from_motherboards_02.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /> 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... <img src="http://acidcow.com/pics/20100829/gold_extraction_from_motherboards_03.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /> You need a lot of pins to conduct this experiment, and that's exactly what our donor boards provided... <img src="http://acidcow.com/pics/20100829/gold_extraction_from_motherboards_04.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /> ...along with some equipment and chemicals. <img src="http://acidcow.com/pics/20100829/gold_extraction_from_motherboards_05.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /> 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. <img src="http://acidcow.com/pics/20100829/gold_extraction_from_motherboards_06.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /> 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. <img src="http://acidcow.com/pics/20100829/gold_extraction_from_motherboards_07.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /> 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. <img src="http://acidcow.com/pics/20100829/gold_extraction_from_motherboards_08.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /> 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. <img src="http://acidcow.com/pics/20100829/gold_extraction_from_motherboards_09.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /> 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. <img src="http://acidcow.com/pics/20100829/gold_extraction_from_motherboards_10.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /> 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 <img src="http://acidcow.com/pics/20100829/gold_extraction_from_motherboards_11.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /> 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. <img src="http://acidcow.com/pics/20100829/gold_extraction_from_motherboards_12.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /> 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 <img src="http://acidcow.com/pics/20100829/gold_extraction_from_motherboards_13.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /> 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. <img src="http://acidcow.com/pics/20100829/gold_extraction_from_motherboards_14.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /> 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 <img src="http://acidcow.com/pics/20100829/gold_extraction_from_motherboards_15.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /> 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! <img src="http://acidcow.com/pics/20100829/gold_extraction_from_motherboards_16.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /> 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. <img src="http://acidcow.com/pics/20100829/gold_extraction_from_motherboards_17.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /> And here's the result! <img src="http://acidcow.com/pics/20100829/gold_extraction_from_motherboards_18.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /> <img src="/styles/default/xenforo/smilies/default/D.gif"  class="smilie" loading="lazy" alt=":D" title="Big grin    :D" data-shortname=":D" /><img src="/styles/default/xenforo/smilies/default/D.gif"  class="smilie" loading="lazy" alt=":D" title="Big grin    :D" data-shortname=":D" /><img src="/styles/default/xenforo/smilies/default/D.gif"  class="smilie" loading="lazy" alt=":D" title="Big grin    :D" data-shortname=":D" /><img src="/styles/default/xenforo/smilies/default/D.gif"  class="smilie" loading="lazy" alt=":D" title="Big grin    :D" data-shortname=":D" /> </blockquote>

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