Reverse electroplating for gold recovery

A. Hi Jared. The gold plating on circuit boards will usually be 24 kt, or very close, but the issue is that the plating is very very thin. On reasonably current computers it's probably something like 20 millionths of an inch on the tabs -- and half of that in other areas. Calculate how many square feet of gold plating it takes to get a worthwhile amount of gold. On boards that are 50 years old or more, the plating thickness was quite a bit greater.

Regards,

A. Hi Yogesh. "GC" probably means gold cyanide, or more exactly, potassium gold cyanide.

Regards,

A. You must crush the chips in order to get inside of them, a rock crusher works quite well for this, I understand that you can recover between 1/20 and 1/100 of a gram per chip depending on what chips you are processing.

A. Hello, these following (non business) hobby websites mention the same article dealing with the security of microprocessors, and details how one might dissolve the packaging materials (using fuming nitric acid) I think.
Now, I don't know how this might affect the following processes for gold extraction, in fact I think it might dissolve everything EXCEPT the silicon wafer - wasting acid and leaving you with a messy sludge! which is why I probably won't be using a method similar. You want to expose as much gold as possible. crushing preferred...

My personal chip website:
http://www.chips.5u.com ⇩
and from whence the article came:
http://www.cl.cam.ac.uk/~sps32/mcu_lock.html

My process has been to heat the chip cover over a Bunsen flame, and pop off the gold plated (both sides!) cover. Now very careful - ceramic gets VERY HOT and retains heat for a few minutes! In small 286, and larger 386 and 486 chips, there are many pure gold bonding wires, easily seen and accessible. In ALL gold-top pentiums, and pentium pros, and IBM etc/other CPU's there is the same. Later CPU's have less and less. See my website to view some nice gold-tops. The smaller black chips generally have no gold content worth the trouble. i.e., if you can't see it on the outside, there isn't much on the inside! but if you are dealing in millions of chips, this becomes a differing story!
I initially scraped the fine gold bonding wires off with a fine blade onto a glass plate for collection. Now, there is more gold in them there chips, however it is plated on the pins, it is on both sides of the cover, and it is also internal to the ceramic, you can see the plated traces running into a layer of ceramic, actually many layers.
What I intend to do is crush/grind/pulverize the complete ceramic chip, and extract the gold with the aqua-regia method. I would like to try the electroplate salt-water and ceramic tray method and have finally figured all the steps and chemicals involved. However just trying to source the ceramic dish/tray/cup and chemicals in new Zealand is proving to be a royal pain in the ears!

I hope I may have enlightened and educated some. And please please, take notes of all the concerns of the experts - this isn't really a home hobbyist project, nor is it a great earner for a home hobbyist either. Try and work with a simple cup of water, practicing not to spill a drop in transferring, filtering etc - and see if you can! Remember that simple microscopic drop could mean a serious burn, or blindness from a miss-wiped face.
Also, personally, I would not attempt the cyanide processing method unless you are prepared to invest into a serious refinery, requiring serious people with serious knowledge and expertise, the cutting of lots of red-tape, lawyers, legalities, zoning, health and safety, etc etc....

[Ed. update: The above link is broken -- don't go there. Thankfully, The Internet Archive is preserving a copy
Unlike the days when a paper record was probably somewhere, when information disappears from the internet, it's simply gone forever. If that causes you concern, please consider a donation to support The Internet Archive.

A. Hey TEE SIM & DAVID A. HARTNESS

I have idea for you just strip the isolation and keep the core inside sale those to the people who making jewelry , they can use that to make gold plating necklace etc. Easier and better for you

"Chemistry of Gold Extraction"
by Marsden & House

on AbeBooks

or eBay or

Amazon

(affil links)

A. Hi everyone, I've been refining my own gold from computer scrap for years now. I use a nitric digest on gold pins and components that are gold plated, that puts almost all the other metals into solution (except the gold), which I pour off most of, then filter the rest. What is left on the filter is "dirty gold". Then I take that and put it into aqua-regia solution. Makes a pretty bright yellow solution. Then I drop the gold out of the solution with sodium sulfite. That leaves the gold looking like a nice reddish brown dirt on the bottom of the jar. I filter this out using Whatman ashless filter paper. Then I burn off the filter paper and I'm left with 99.999% pure gold! Some times, however, I have to deal with "the blue goo" which plugs up my filtering, (in the nitric digest phase).This happens when I haven't gotten all the solder off the parts. You can't have solder on anything. That's my method in a nutshell. Any feed back is welcome.

A. My short answer is that mechanical separation & sorting sound worthwhile and may extend to such measures as smashing plastic connectors to get to the gold, cutting circuit boards to separate gold contact areas from the bulk of the board, etc. But please remember that all of the major environmental organizations are begging you not to do this for two reasons: first, amateur recycling is a wrecking ball that spreads the e-waste toxins everywhere instead of keeping them in manageable units like a computer or TV; second, when people "cherry pick" the waste, the recovery of the balance of the equipment becomes economically prohibitive which means it will not be recycled; rather the toxins will be left to contaminate the earth.

Any operation which involves burning or chemical treatment should be left for a real refinery anyway. Proper refineries cost tens to hundreds of millions of dollars.

I realize that others may disagree, but in viewing pictures from China and India, you see the human toll and environmental toll of e-waste recycling by amateurs; plus, you also realize that your competition is starving waifs working for pennies a day :-(

The best long-term solution to e-waste (as far as I can see, and not taking into account the law of unintended consequences) seems to be laws that require the manufacturer to take it back at no charge for disposal at end of life.

The subject of do-it-yourself gold refining has raised it's ugly head on this forum many times. With the present high gold prices, interest in this subject is building and isn't going to go away. There is very much dangerous misinformation on the internet. On eBay , there is a fair sized cottage industry providing gold refining info, some good and some bad - mostly overpriced. Several months ago, a gold refining forum was set up (not by me) to provide honest, free information, keep amateurs safe, and properly handle waste. In 6 months, there are over 700 members and over 8,000 posts. There are 2 or 3 of us on the forum who have been professional gold refiners for many years, that attempt to act as a stabilizing factor. Personally, I feel that refining should be done by the pros but, if amateurs are going to do it, they should do it right: goldrefiningforum.com. I would imagine that this forum has already taken some of the burden off of finishing.com.

Ed. note: Chris has been a great responder at finishing.com and we thank him for his efforts and the education! Also a number of people have been very complimentary about his forum.

A. THANK YOU BROTHERS AND SISTERS,
I've got it. I've been reading this page and others to figure out the process and I've got gold from old e-scrap that I collected for 3 years and got a nugget the size of a quarter and 3/16 of an inch thick. Well here's your answer: titanium metal, a white flame heat source and ⇦this on eBay or Amazon [affil links] is all you need, these chemicals. Please work in fresh air also butane don't waste your time and money, think hot heat and even consistent heat does a nice easy job.

THANKS
THE CLYDE
PS. I've got gold so let this economy go to double tooth picks RRRReal money!

A. This is Very Simple and is the basis of all Chemical Gold recovery in the Au gold mines in the early days.

Take the gold coated item , (we do this with gold tailings in exploration) Boil it in a solution of Concentrated household bleach ⇦ bleach/sodium hypochlorite in bulk on eBay or Amazon [affil links] , 50% water to bleach 50% for 45 Min.

Drain off the solution

Put in plastic pail

Put in stainless Steel rod (one side)

Put in roll of wire wool (other side)

Get a powerful battery charger ⇦this on eBay or Amazon [affil links]

Attach (plus) to wool and minus to SS rod.

Turn on battery charger .

leave 40 mins, Gold will be converted from solution to the wire wool.

Take wire wool and dissolve in crucible in hydrochloric acid, carefully drain off the acid and keep sludge at bottom.

Place crucible over Bunsen burner and melt.

Small gold nugget will form in the bottom.

Thank you

PS be careful to vent off the hydrogen gas with the electrowinning stage.

A. The answer to most of those questions are trade secrets of sorts, so it seems. If you discovered a gold vein, would you go broadcasting it and start a stampede to it?

In short, it's worth going for if you know what you're after. Computers for instance, the older the better, cause back in the 286, 386, n P1 days the manufacturers were using heavy but expensive plating. So go after those sources and you won't go wrong. You would be surprised at the amount of old Gold Rich abandoned units are sitting in basement rooms of schools, office bldg's, Hospitals, etc.:)

A. Hi Al.

In these days of prolonged recession there are "We buy gold!" stores on every other street corner in the cities and suburbs. If none of them are uninterested in buying it, it should give you a sense of its value vs. the cost of recovery. Modern gold plating tends to be from 10 to 40 millionths of an inch thick, often even thinner. You will see many costume jewelry manufacturers rejecting the idea of "micron gold" (coatings of 40 millionths thick) as being much thicker than they are willing to apply. Please do a simple volume calculation of how much gold you actually have. Good luck.

Regards,

A. Hi Toni. If you have indeed plated out gold metal foil, it should be worth plenty without any worry of remelting and further purifying it ... and no buyer is going to trust a bullion bar from you anyway. Why waste money and time doing that? Peel the foil off of your passivated stainless steel starter sheets and sell that.

Luck & Regards,


Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

A. Hi Sam.

Acids are readily available.

But cell phones are new technology with the thinnest possible gold plating. Please calculate how much gold you have before investing in acids, and before undertaking the required education and the risks of gold recovery.

Regards,

A. Firstly, I am not an authority on this subject. That said, is abrasion an option? A firearms cartridge tumbler with an aggressive abrasive. Pan the residue, then melt it. Gold will be at the bottom, won't it? Perhaps just skip to the melting. Even the copper will have value.

Thanks, Jonathan. I understand that some people concentrate on the gold plated tabs of circuit boards, scraping the gold off with a razor blade (don't forget safety glasses or goggles for this). But if this has any practicality at all, it's only for very old (50 year old or more) boards. With today's gold plating of 20 millionths of an inch or less, if you were able to scrape off 100% of it, you'd need 5 layers just to equal the thickness of a human hair; 100 layers to equal the thickness of your thinnest (0.002") feeler gauge. There is very little gold in cell phone. I'm reminded of the alliterative crude-ism "small as a nit on a gnat's nut" :-)

Regards,

A. Refining cannot be done by simply melting it. You might be able to oxidize and remove a small amount of the copper by adding 3 or 4 pearls (BBs) of sodium nitrate ⇦this on Amazon [affil link] along with a pinch of borax ⇦this on eBay or Amazon [affil links] to the melt. The small amount of copper oxide produced will end up in the slag. This can be repeated. Some of the zinc in the alloy will be oxidized at the same time and this could affect the casting properties.

Gold scrap often contains solder and solder often contains lead. Since it only takes about 5-10 ppm of lead to make the casting brittle, it is usually a bad idea to re-cast scrap gold. Most all reputable jewelers that I know of don't even try to re-cast scrap gold.

There is no safe method to refine (purify) gold. It always requires the use of aqua regia, which is a combination of nitric and hydrochloric acids. Both are quite dangerous and, in combination, they are even more so. When in use, very toxic fumes are emitted and, therefore, a fume hood is an absolute necessity. Also, it takes a lot of hands-on experience and knowledge to successfully refine karat gold.

The only safe way to raise the purity to 14K is to melt the 10K and add pure gold to it. If you have 10 grams of 10K, you would have to add about 4 grams of pure gold to it to raise the purity to 14K. However, you won't know what color you'll end up with until you do it.

A. Hi Marie,

Leave chemicals to the chemists.

The earliest method for refining gold is cupellation.

The gold is simply melted, preferably in a bone ash cupel, and the base metals (except silver) are oxidised. If you have a bone ash cupel, the oxides are absorbed by the cupel, otherwise discard the slag. This method produces gold pure enough for assay purposes and then you can add whatever you need to get back to 14 ct.

Or with a bit of calculation, you could refine a small part of your sample and add it to the remaining 10 ct part.

Search the net for "Fire assay cupel" and use an oxidising flame (a kiln is better)

A. Hi Jared. Either will work equally well after a fashion, it just depends on the volume of material you are processing (a 10 Amp unit processes more material faster) -- but neither will be great because they are designed to charge batteries, not as power supplies for electroplating. As Geoff warns, it's really best to leave chemical and electrochemical processes to people who are trained in it because there are dangers at every step in the process.

Regards,

A. The gold refining forum that I act as a moderator on [ed. note: goldrefiningforum.com] has done much work with the so-called "reverse electroplating" method of gold stripping using concentrated sulfuric acid as the electrolyte. It can be used to strip gold from most anything, including aluminum, without attacking the substrate metal (unless the solution gets too hot). The gold precipitates as a black powder and settles to the bottom. After settling, the top solution can be siphoned off and reused. It will also strip silver and palladium but separating these from the solution is more difficult than with gold.

The biggest problem with a small cell is regulating the amperage. If too much current is used, the solution will overheat and this can cause big time problems down the line. I once had a 50 gallon cell that I ran at 250 amps. Even in sunny L.A., the solution never exceeded about 110 °F.

I would recommend not exceeding 5 amps per gallon, which will strip most gold plating in just a few minutes. This is difficult to do with a battery charger although I have never used one for this application. I do know that an automatic charger won't work. A manual one will work. Also, unlike an automatic charger, the output of a manual charger can be varied by plugging it into a Variac.

Being an old plater, I prefer the one knob, one ammeter, one voltmeter, and fuse (one or two) type rectifier as a power supply.

Just remember that an electrical connection must be made to each isolated gold-plated portion of the part you are stripping. For this reason, circuit board fingers are not a candidate, since the individual fingers are not connected to each other.