Get Pure Gold From Electronic Scrap in One Place

The following presentation will describe the process of refining gold from electronic scrap.   The descriptions and instructions given in text below are supplemented with video taped demonstrations of the process.  The videos are closed captioned, so be sure to click the "CC' in the lower right of the YouTube viewer.

The "no duh" first step is to collect a bunch of electronic scrap.  In this series we focus on simple gold fingered computer connector cards.  Simply shear off the part of the electronic card which contains the visible gold connectors.  Other scrap sources include processor chips and connector pins.  It is best practice to keep each specific type of scrap in separate batches at least until you've gone through the whole process a couple of times.

The cards can still be sold to a scrap yard minus the gold fingers. Watch out for the occasional high end electronics that have gold plated traces under the green paint.

For the second step, here are the materials you will need:

1.  32% HCL (muriatic acid).  This can be found at any pool supply store and some hardware stores.

2.  Two clean five-gallon buckets with lids

3.  PC cards with only the gold connector strips

4.  Safety gear, goggles, latex gloves, eye wash bottle, and baking soda

5.  Filtering station ... for small scale a 12 cup coffee pot and coffee maker will do

6.  Filters and paper napkins

7.  Container to collect paper filters (with gold)

8.  Container for all napkins and used gloves

9.  Jugs to store fluids in.

10. Hot Plate -- MOUNTED OUTDOORS, AWAY FROM ANY METAL

11. 24" plastic stir rod ... half of a wand from mini-blinds will do.

Simply put the IC cards with the gold fingers into the five-gallon bucket and cover with acid.  Some distilled water can be added to raise the level of fluid if needed.  Swish the stuff in the bucket around every day for a week or so.  Of course, be careful with all the fluids.  Once copper starts to dissolve, the fluid will turn green and it will be toxic to people, animals, and especially to fish.  Make sure to keep everything locked away where no neighbor's kid can get to it.

After inspection of the cards reveals that there is no gold on any card, remove the cards.  Squirt them off with distilled water to wash gold as much gold as possible down into the acid bucket.  Now filter the acid in the five-gallon bucket to separate the gold flakes from the copper chloride acid solution.  

Put all filters and gold flakes into a coffee pot and cover with clean 32% HCL.   Bring this to a boil and stir vigorously to break up the paper filters.  Now pour off the acid (save for re-use) . Only gold, paper goo, and a few small fragments remain now

Now we need some more materials:

1.  A second filter station

2.  A small jug for the gold solution

3.  Clorox bleach

4.  (Ice cubes made with distilled water) ...not needed in cool weather

With all the gold foils and insoluble junk in one coffee pot, add more clean 32 % HCL.  If the temperature is over 75 deg in your work area, add a few cubes of ice made from distilled water to help chlorine stay in solution.  Now dribble small amounts of Clorox bleach into the coffee pot while stirring.  Stop with the Clorox if excessive fizzing begins or if the fumes bother you.  Swish it around, let it sit, swish it around again, let it sit overnight, swish it around again.  If it is hot outside, you can set the coffee pot in a cooler with regular ice in it.  The object is to keep chlorine gas, which is released with the Clorox, in your solution.  The chlorine is what reacts with the gold to dissolve it.

Make sure all the gold flakes are dissolved into a golden to golden green solution.   Now we can filter this solution to separate the gold in the solution from all the paper goo and any other insoluble fragments.   Now we have clean clear liquid with AuCl dissolved in it.

Now it is time to get back to a solid form.  Here are the materials we must add to our list now:

1.  Sodium Metabisulfite powder -- Na2S2O5 (readily available on eBay or restaurant supply store).

2.  95% tin solder wire

You can test for the presence of gold in the solution using the stannous chloride test.   It's easy, just allow a strip of tin solder wire to dissolve in a "tiny" cup of HCL ... you only need a few drops really.  Wet a paper napkin with the gold bearing solution, and then dab the stannous chloride solution onto the napkin with a q-tip.  A purplish-brown splotch should appear quickly if gold is present in good concentration.  If the gold test reaction is weak, you should consider trying to dissolve more gold into your solution.

Transfer the solution back to a good coffee pot, preferably an old-school flame proof glass coffee pot.  Bring the solution to a boil for a couple of minutes to drive off excess chlorine gas.  Then double the volume of your solution with distilled water.  Now the solution is ready to precipitate the gold back out of solution as a solid brown powder.   Now add a few table spoons of the Sodium Metabisulfite to the gold solution. There needs to be room in the container to allow for fizzing.  Be sure to go outside for this step, as it releases noxious fumes.   

Stir the pot until everything turns cloudy brown and ugly.  The Na2S2O5 reacts in solution to steal the chlorine ions away from the gold, leaving the gold behind as solid metal.  So, let the gold settle and you can pour the liquid off and leave the gold powder in the coffee pot.  Filter the fluid in case any gold floats out with it, and save the fluid too, in case more gold is in solution.  Now it is time to refine the purity of the gold powder.  It may be disappointing to know that over half of the powder could still be copper.

Add more clean HCL to the powder, not a lot, just enough to swish it all around in.   Bring this to a boil while swishing from time to time.  Let it cool and pour off the acid.  Be sure to filter lest any gold float out, and save the acid for re-use.   Repeat the swish, boil, swish routine two more times with HCL and then 3 more times with distilled water.

The gold powder is now mostly pure.  We will also use potassium nitrate when we melt it to help burn off any remaining atoms of base metals like copper, nickel, iron, tin, and zinc.   The following materials are required at this time:

1. Graphite crucible

2. Borax

3. Potassium nitrate.

Transfer the gold powder to the graphite crucible.  For every spoon full of gold, add one spoon full of potassium nitrate and five spoon fulls of borax.   The crucible should not be over half-full at this point.  The borax does expand and bubble as it is heated.

To melt the gold, have these items ready:

1. Leather gloves

2. Furnace, acetylene torch, or my "microwave kiln kit" and a microwave oven

3  Graphite ingot mold, or carbonized iron mold

4. Tongs to handle and pour the hot graphite crucible

The microwave kiln is made from a light weight refractory fiber board.   It comes in two inch thick panels.  Aluminum silicate works well, and so do other similar refractory materials.  It can be easily cut into the correct shape with a drywall hole saw.  Two inches is a sufficient thickness of insulation around all points of the crucible to protect the microwave oven.

All metal melting should be done outside as well.  The insulation may off-gas worse on it's first time use.   It takes about 30 minutes to melt about 5 grams of gold in a regular 1000W kitchen microwave.  Be sure to watch closely and check frequently to make sure your microwave is not getting too hot.

If you need to stir the mixture of gold and borax, use a clean graphite rod.  Give the gold plenty of time to heat up in the microwave, and then have you tongs and mold ready so that you can flip the crucible quickly to pour out your gold into a graphite ingot mold.  A less expensive alternative is a piece of angle iron or cast iron depression.  Be sure to coat the surface of the iron with a layer of soot (from acetylene torch or candle.

Project End: Proper Waste Disposal and Recycling

 Please dispose of all materials, leftovers, acids, metals, and toxins appropriately.  This will help you get more gold out and save the little fishes of the sea.

Here is a list of additional items that are needed to recycle and dispose of the waste stream materials:

1.  Plastic storage bin
2.  five-gallon bucket with lid
3.  UPS power supply (or other source for 2 to 3V)
4.  Wire, electrical clips
5.  tywraps
6.  strong plastic bag
7.  10' x 1/2" PVC pipe
8.  graphite anodes - maybe be recovered from some D-cell batteries
9.  stainless steel straps and screws
10. PC fans
11. plastic mesh washable home A/C air filter
12. coffee pot (glassware capable of boiling fluids)
13. hotplate
14. 2' x 3/4" Copper pipe

The first step here is to verify that there are no precious metals remaining in the CuCl acid solution using the stannous chloride test.  If there is any suspicion that precious metals remain, a large scrap of copper can be added to the solution to make sure that all precious metals precipitate out of solution.   After some time is given to allow solids to settle, the waste fluid can be siphoned off the top and base metals can be removed via electrolysis.  Any sludges that form at the bottom of the bucket should be treated as if they contain precious metals, and they should be run back through the whole process with the next batch of gold bearing electronic scrap.

 Video: Making a graphite anode rack

A high-end UPS backup power supply can be used as the power source for the electrolytic tank, but do verify that the voltage settles in the 2V to 3V range when everything is hooked up.  If the voltage goes higher, gases will be generated, electricity will be wasted, and the surface quality of the copper plate will be jagged and unsalable. A plastic five-gallon bucket can still be used as the tank although a secondary containment system is recommended to catch spills and drips.  A plastic storage bin is adequate.

An anode rack should be made from graphite rods because the acid bath is too corrosive for any metal to exist on the anode (+) side of the electrolytic cell.  Graphite anodes can be recovered from some used D-cell batteries.  Besides the method shown in the video above, stainless steel screw clamps are another handy way to attach a lead wire to the graphite anodes.  In order to keep the solution free of solid particles, simply wrap the anodes with coffee filters since they will eventually deteriorate.  In the case of an electrolytic cell, the anode should be attached to the positive terminal of the power supply. 



Video: Prepare a copper starter plate to serve as the cathode.

The cathode, a flattened piece of copper pipe, should be attached to the negative terminal of the power supply.  Metal from the solution will accumulate on this copper starter plate.   If the rate of accumulation is too fast, and a rough surface develops, the voltage should be lowered and/or a physical barrier should be placed around the pipe to slow the ions in solution from getting access to the copper pipe.

On my first attempt, the rate of deposition of copper got too high at some locations on the starter plate.  That led to rough formations of copper deposits.  The copper would flake off in places, and that is not a desirable form to sale it in. The first thing to check is voltage if that happens.  If the voltage is staying between 2 and 3 volts, then you will need a physical barrier around the pipe to control deposition rates.   Cut the ends off flexible plastic drinking bottles and slide them over the copper plate.  It will be good if the plastic tubes are deformed into an oval shape in order to fit around the copper plate as that will prevent deposition on the edges of the copper plate.  Holes can be drilled into the plastic tube as needed to increase deposition if a higher rate is needed.

 

Video: Electro-cell operation and copper recovery

If you are starting with solution that is saturated with copper, it will be dark, opaque, and chemically it will have one copper ion associated with one chloride ion -- Cu(+)Cl(-) or just CuCl.  As electric current is run through the system, oxidation and reduction reactions occur and the result is that soon there will only be one copper ion available for every two chloride ions -- Cu(+2)Cl(-)2 or CuCl2.   The extra copper ions come out of solution as solid metal on your cathode plate.  You will know when that process is done because the solution will turn into a beautiful emerald green liquid that you can see through.

The solution can now be reused with a new batch of gold bearing electronic scrap.  This process helps save you the need to buy more clean HCL, and it reduces the volume of metallic salt bearing solution that must be disposed of in an environmentally friendly way later.

 

Video:  CuCl solution ready for reuse.

If you continue to run current through the electrolytic cell, the rate of copper deposition will begin to fall sharply.  When the amount of copper ions drops below the number of chloride ions, the chlorine will begin to associate with hydrogen in the water, and regenerate the HCL in solution.  But, other reactions also occur which can lead to the generation of H2 and Cl2 gases.  That could possibly result in a fire risk, but also chlorine gas is very corrosive to tools or anything you have in the area.   There is no need to run the electrolysis for that long however.  Simply run it until the solution goes emerald green and clear, and it will be ready to dissolve more copper.

After your last batch, you must dispose of everything in a safe way, or find a market for all waste stream.  All solid materials must be washed repeatedly with clean water to get all the metal salts out.  To deal with the volume of water, you will need a dryer unit.  Fans from computers can be used with plastic buckets and plastic air filter mesh materials to evaporate the solutions.  As the solutions are re-concentrated, metals can be electroplated out again.  Finally as the solutions are dried completely though, only metallic salt crystals will remain.  These can be sent off for assay to a precious metal refiner.  For a fee, they will let you know exactly what metals are present.  Then you can plan best how to sell or dispose of the salts once their composition is known.