If you have access to a large amount of e-waste, you may literally be sitting on a gold mine. There is gold that can be recovered from discarded computer circuit boards--but in such small amounts that the time-consuming and dangerous process required to remove gold from computer circuits is only worth your while if you have at least 1.5 tons of used boards.
- Skill level:
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Things you need
- Glass beaker
- Steel forceps
- Steel tweezers
- Metal pics (similar to dental tools)
- Melting furnace
- Small steel crucible
- Metal plate mould
- Metal plate holders
- Glass tank
- Copper plate
- Steel plate
- Hydrochloric acid
- Nitric acid
- Shallow glass dish
Take your circuit boards and using tweezers and small pics, strip all the metal from the ceramic board. The metal will contain gold, silver and copper in mixed amounts too small to be separated by hand.
Place the metal you pulled off your circuit board into your steel crucible. Heat your furnace and melt all the metals together until they are liquid. Pour the liquid into your metal plate moulds and let cool.
Prepare a "plate bath" in your glass tank by filling it almost to the top with distilled water. Put one of the metal plates from your mould into your plate holder and submerge the plate completely in the bath. Do the same with the copper plate and submerge the plate two inches away from the metal plate you made.
Apply a positive charge to the plate you created and a negative charge to the copper plate. Let them sit for an hour. The copper from your plate will be drawn to your copper plate, as if it were a magnet. Remove both plates from your bath and let dry.
Repeat Steps Three and Four, using a steel plate instead of a copper plate. The steel plate will draw all the silver from your plate in the form of crystals, and all that will remain in the plate you created will be gold. Again, let both plates dry.
Mix the hydrochloric acid and nitric acid in your glass beaker in a 3:1 ratio. You will want enough of the mixture so you may completely submerge your plate. This mixture is known as "aqua regia" or "royal water."
Submerge your plate in the acid. You will see it begin to turn an orange colour and be cloudy. This will show you that you have the right mixture and the gold is being dissolved. Once there is no more "cloudiness" in the mixture, you are done dissolving the gold and can remove the remaining plate. This takes about a hour.
Pour small amounts of your acid mixture into your small glass dish and wait until that amount has evaporated before adding more,. Repeat this process until all the liquid has evaporated, leaving a dusty residue in the dish. The dust that remains will be pure gold.
Tips and warnings
- Melt down the metal contents from several circuit boards at once rather than separating the metals board by board; the amounts of metal on each board are so small that the more you strip at once, the faster the process will be.
- Hydrochloric acid and nitric acid are extremely poisonous, so use great caution in working with these acids. Wear appropriate safety equipment and make sure you are working in a well-ventilated area.
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