A modern gold mine can extract about 10-15 grams of gold per ton of processed ore on average, whereas an e-waste recycling facility can achieve 90-150 grams of gold processing a ton of e-waste material.
A much higher returns, ten times more gold per weight unit of raw materials processed. And that's only the gold output without factoring in the platinum, palladium, silver, copper, tin, ..etc!
While urban mining as they call it might be a lucrative business to own and run, the entry cost can be very high if you want to make good profits. Otherwise, like any other aspect in life, the smaller your business the less profit you can squeeze out of, or it might even end up in a loss when you're not factoring in your running costs correctly.
Being the tiny fish that I am 😁, I like doing some gold recovery in my spare time for fun as a hobby more than any other reason. I collect and recover what I can from various e-waste PCBs that I come across.
To do it properly, you'd have to depopulate the PCBs first. Picking up and separating the components that potentially contain some gold.
Depending on what kind of electronic components you are dealing with, the recovery methods and processes would differ.
Some require more steps and/or different chemicals to do it. But the basic idea is the same, you separate the gold or precious metals from all other trash.
I will talk about one of the easiest components to deal with, RAM Stick fingers.
Memory sticks or RAM as they're commonly known are one of the main parts of PCs and laptops. They have visible gold-plated fingers and gold-bearing IC chips.
The thickness of that plating differs by many factors, age being most crucial because as the technology advances the more precision and control they have over manufacturing, so the plating gets thinner and thinner the more recent it is. And that's generally true for all other gold or precious metals bearing components. (They love reducing their costs)
Now to recover that minute amount from one stick or a dozen would be ridiculous, to say the least. While it is possible it would be impractical and super inefficient. You need pounds/kilos to start getting meaningful results.
As I said, it's just a hobby for me, but still, I save up what I can until I have a somewhat viable amount of components to tackle.
WARNING
Gold recovery and refining processes use highly corrosive, toxic chemicals and deadly fumes that can be very dangerous and harmful to your health, and they can even kill you or cause permanent damages to yourself and/or others around you.
This post is for educational purposes only. I'm not encouraging anyone, and I will not take any responsibility for any misuse or harm that you might cause if you decide to do it.
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And now since that's sorted, let's begin the process! 😀
What chemicals I'm using?
• Hydrochloric Acid (Muriatic)
• Sodium Hypochlorite (Bleach)
• Hydrogen Peroxide (Not really needed)
• Copperas (Iron II Sulfate) -or- Stump-out (Sodium Metabisulfite)
All of which can be bought from any grocery stores or Home Depot.
Preparing the material:
The first step in dealing with RAM sticks would be cutting the fingers, separating them from the rest of the stick. The fingers have a more direct approach for processing, while dealing with the IC chips is different and requires a more thorough process to get the gold hidden inside of them. Fingers are what we will deal with here today.
Separating the foils:
Once the fingers are cut and clean, they're ready to go!
Multiple different chemicals can be used to get the gold foils detached from the fiberglass and the base metals. However, I prefer to do it with the slower but safer and cheaper method.
I cover the material with HCL (Muriatic acid). Then can add a small amount of H2O2 (Hydrogen Peroxide) to kickstart the reaction faster. Adding too much can and will make you lose some of the gold.
A ratio of 10 to 1 respectively is more than enough, and I actually only use a fishtank air bubbler instead nowadays.
The point is to oxidize the copper underneath the gold plating so the HCL can digest it along with any nickel and/or tin that might be present.
Once soaking in the acid, it's left for a few days to do its thing, you'd notice the light green color gets darker and should notice the gold foils start releasing and swimming around.
When all the foils get liberated, using a coffee filter or a cotton ball in a funnel, filter the solution and collect all the foils.
Dissolving the gold:
After cleaning up the collected foils a bit with some HCL washes, getting rid of as much of the waste solution traces as possible, it's time to dissolve the gold to purify it!
To do that, a solution of Aqua Regia is usually used, composed of Nitric Acid and Hydrochloric Acid. However, for foils, HCL and Sodium Hypochlorite (bleach) can be used instead to dissolve the gold.
Covering the foils with clean HCL, I add few drops of bleach at a time and stir, they get dissolved almost immediately.
Careful not to breathe any fumes though. ☠
Once the foils completely dissolve, we are left with a beautiful golden yellow-colored solution 💛 of HAuCl4 (Chloroauric Acid).
My camera doesn't do it its justice at all 🙁
The solution gets filtered to make it crystal clear, getting rid of any small debris or undissolved contaminations.
Precipitating the gold:
Again, there are multiple options and Sodium meta-bisulfite is most commonly used to do that nowadays. I prefer to do it using Copperas (Iron II sulfate) FeSO4 instead. Either way, it's a beautiful slightly delayed color-changing reaction that will cause the gold to precipitate as a tan/brown powder.
Once it settles to the bottom completely, the left-over solution is decanted and the powder gets a final wash with HCL and then water to clean up any small contaminations.
If everything is done correctly, we end up with a very high purity 24 karat fine gold!
Melting:
The amounts I recover are usually small to melt on their own, so I just keep adding them up together until there is sufficient amount to warrant a melt into a nice button.
Thank you for reading! Hope you enjoyed it and learned a thing or two about recovering the gold from e-waste and refining it. 🙂
If you have any feedback, suggestion, or questions, feel free to ask in the comments!
Thanks for stopping by, really appreciate it.
Have a wonderful day, and stay safe!
