911Metal

Did you even see the footer article on Gold that was recovered from scrap electronic 60-40 (tin-lead) solders by drossing with aluminum or zinc at elevated temperatures? The gold, together with other metallic impurities, collected in the dross phase which could then be separated from the molten solder by skimming or filtering. Drossing upgraded the gold concentration by a factor of 10, Further upgrading was achieved by a combination of steps including an oxidation roast and either a combined cyanidation-amalgamation treatment or an aqua regia leach. The gold was then recovered in highly concentrated form from the aqua regia or cyanide solutions by cementation and from the amalgam by volatilization or dissolution of the mercury.

Here is more about Agua Regia & Gold https://www.911metallurgist.com/blog/extraction-recovering-gold-silver-jewelry-electronics-escrap + https://www.911metallurgist.com/blog/how-to-use-aqua-regia-to-purify-gold BE CAREFUL! The Dangers Of Aqua Regia: Aqua regia cannot be boiled or simmered in the house or where it is not well ventilated. This can cause serious illness or KILL YOU! Use a vent hood with an exhaust fan or simmer in the open. Hydrochloric acid is very dangerous. It CAN BURN TO THE BONE and is extremely painful. In most cases, it has burned you before you know it. Nitric acid can be absorbed through the skin, causing nitric acid poisoning, which makes you very ill. WEAR RUBBER GLOVES! Aqua regia, nitric acid and hydrochloric acid CAN KILL IF SWALLOWED. Always wear rubber gloves, plastic safety glasses and a plastic or rubber apron. Aqua regia can ruin your clothes and shoes.