Gold recovery from circuit boards is not only easy, it can be done at home! The highest concentration of gold in any computer hardware is contained on the gold fingers found on slot cards and RAM. Recovering gold from RAM and slot card fingers is also one of the easier processes. For this reason, this is where many DIY e-waste refiners begin their journey. Note: this process only works for gold foil and gold fingers. This process does not work very well for gold plated pins. Visit the Resource tab to see where I purchased everything needed for gold recovery.
Equipment and Chemicals you will need:
- Quality Beaker Set
- Personal Protective Equipment – Gloves, eye protection, and acid/vapor mask. Note: The mask must be rated for acid/vapors. If you’re not sure what that means, visit the Resource tab.
- Hydrochloric Acid (AKA Muriatic acid)
- Hydrogen Peroxide (3%)
- Household Bleach or Nitric Acid
- Sodium Metabisulfite (SMB)
- Filters
- Tap water
- Optional: Air bubbler
Gold Recovery Preparation
Step 1: Collect all your gold fingers and weigh them. This will be used at the end for a final yield.
Step 2: Collect ALL of your safety items.
Note: Anytime you are working with any of the chemicals, you should be wearing gloves and safety glasses or face shield.
Dissolving Base Metals
Step 3: Place all the gold fingers into a beaker. Add enough Hydrochloric acid to cover all the fingers.
Step 4: Add a few drops of Hydrogen Peroxide.
Hydrogen Peroxide acts as an oxidizer. An oxidizer is required to dissolve the copper layer under the gold foils. This process can take anywhere from a few days to a few weeks depending on ambient temperature and if a bubbler and oxidizer is used. This process will remove any of the copper, nickle, and zinc that may be present.
Step 5: Sit back and be patient.
This process may take a few days or even a few weeks. If you are not using a bubbler, stir or agitate the solution at least once a day.
Separating Gold Foils from Solution
Step 6: Remove the gold fingers from the solution.
As the base metals dissolve, the gold foils should start falling off the fingers and collecting in the bottom of the beaker. Some of the foils may need to be sprayed or scraped off the fingers. If you have a better way to accomplish this, leave a comment below!
Step 7: Separate the foils from the solution.
Pour the solution through a filter into a second beaker. Using a spray bottle, rinse the gold foils out of the beaker into the filter.
Step 8: Test the filtered solution for any precious metals.
Dip a piece of filter paper into the solution. Place a drop of stannous chloride onto the wetted paper. Pour the filtered solution into your stock pot.
Dissolving the gold
Step 9: Dissolve the gold foils (and filter) using Aqua Regia.
NOTE: THIS STEP WILL CREATE HAZARDOUS FUMES! BEFORE MIXING THESE CHEMICALS, PUT ON YOUR P100 MASK, GLOVES, AND FACE PROTECTION!!!
Place the filter with the foils into a clean beaker. Add approximately 100ml of hydrochloric acid to the beaker. Slowly add nitric acid (or household bleach). It is best to add in 5ml increments. Adding incrementally will prevent the solution from boiling over. This solution should now be a golden color. The solution is now Auric (gold) Chloride.
Step 10: Filter the Auric Chloride solution to remove any solids.
Gold Recovery
Step 11: De-nox the Auric Chloride solution to remove any excess Nitric acid
If you used Nitric acid, you will need to de-nox (remove any free Nitric acid) by adding Urea or Sulfamic acid. I prefer to use Sulfamic acid for several reasons that are beyond the scope of this tutorial. Click here for an explanation of different methods of denoxing.
Step 12: Drop the gold from the solution using Sodium Metabisulfite (SMB).
Mix a few spoonfuls of SMB into a small, clean beaker of warm water. Once most of the SMB has dissolved, pour into the filtered Auric Chloride. Depending on the amount of gold in solution you may or may not see a reaction immediately. The solution should turn a dark brown.
Step 13: Allow the gold powder to settle to the bottom.
The gold may take up to 24 hours to fully settle to the bottom of the beaker.
Step 14: Filter, melt and weigh your recovered gold!
Step 15: Test solution to ensure all gold has been dropped.
Dip a piece of filter paper into the solution. Place a drop of stannous chloride on the wetted paper. There should be no color change. If there is a color change, you may still have gold in solution and should re-perform steps 12-15.
Congratulations! You should now have gold powder that is 99% pure! You can now melt the gold into a button. If you perform any of the steps differently than I described, leave a comment below with how you prefer to do it.