Place your circuit boards in a glass vessel. In another container, mix two parts hydrochloric acid and one part weak hydrogen peroxide (a concentration of three per cent). Pour this mixture over the circuit boards so they are completely submerged.
Pour nitric acid into the glass container over the circuit boards. Stir the mixture with the glass or metal rod until the contents become a uniform fluid. Once the gold has separated from the plates — it may take some time — strain the nitric acid from the mix using the filter. Take out the pieces that aren't melted.
Sodium metabisulfite is a popular choice in this process because it is more selective in precipitating gold by itself. In the process of gold extraction from scrap computer electronics parts, Sodium Metabisulfite is usually used along with Urea.
Known for being very corrosive, aqua regia consists of a mixture of nitric acid and hydrochloric acid that, in the correct ratio, can dissolve nonreactive elements such as gold and platinum.
Use Nitric Acid
If you have a circuit board with gold plating, you can remove the gold using nitric acid. The acid will dissolve the metal and leave the non-metallic components of the circuit board intact. Be sure to wear goggles and gloves when working with nitric acid, as it can cause chemical burns.
The Canadian researchers' alternative is a solution of acetic acid and an oxidant — a nontoxic technique to dissolve gold, which is stripped from circuits in about 10 seconds, leaving intact copper, nickel, iron, and other metals in printed circuit boards.
However, gold is readily dissolved in a number of solvents, including oxidizing solutions of hydrochloric acid and dilute solutions of sodium cyanide. Gold readily dissolves in these solvents because of the formation of complex ions that are very stable.
The acid mixture aqua regia, or royal water, dissolves gold and is used to purify scrap alloy containing gold. Aqua regia is a mixture of hydrochloric acid and nitric acid in a 3:1 ratio.
In order to distinguish gold from other base metals, the gold-containing item is rubbed on a black stone/surface which will leave a visible mark. Nitric Acid is then applied to the mark. If it easily dissolves, the item is not Gold. If the mark remains, Aqua Regia (Nitric Acid and Hydrochloric Acid) is then applied.
Circuits in modern CPUs and Laptops weigh around 100 gm so you can expect to extract 0.150 grams of Gold. Additionally, the wires and connector pins have gold which will amount to another 0.070 gram and another 0.090 grams for gold plated contacts.
Magann: A PC circuit board, where the gold is, weighs about a pound. If you had a ton of those boards, you should have 5 troy ounces of gold.
While extracting gold from electronics is not without its challenges, it can be worth it for individuals looking to recover valuable metals and reduce e-waste. However, following safety precautions and using personal protective equipment when handling hazardous chemicals is essential.
In fact, computer parts contain the most gold. It is possible to recover gold from computer boards; it is also possible to extract gold from motherboards, integrated circuits, contacts, pins and printed circuit boards.
Removing Gold Using Fire
Use steel tongs to turn over the burning circuit boards. Get a metal bin or tray, and put the circuit boards into it. Break the boards into smaller pieces so they burn faster. Light the boards on fire.
Aqua Regia Solution Preparation:
Slowly add the nitric acid to the hydrochloric acid (NEVER the other way around) to form a 3:1 ratio solution of three parts hydrochloric acid, and one part nitric acid. Stirring with a stir bar and plate is recommended.
CitriSurf® - The replacement for nitric acid.
Add 120 milliliters of hydrochloric acid for every ounce of gold in the container. For 5 ounces of gold, that would be 600 milliliters of HCL. The addition of hydrochloric acid turns the mixture brown and can result in fumes. As the chemicals react and heat up, the gold will dissolve.
Aqua regia is a fuming liquid. Freshly prepared aqua regia is colorless, but it turns yellow, orange or red within seconds from the formation of nitrosyl chloride and nitrogen dioxide. It was named by alchemists because it can dissolve the noble metals gold and platinum, though not all metals.
The only way gold could truly be destroyed is through nuclear reactions. However, there does exist a way to dissolve gold using “Aqua Regia,” which is a mix of hydrochloric and nitric acids.
Mercury and gold settle and combine together to form an amalgam. Gold is then extracted by vaporizing the mercury. Although mercury is a naturally occurring element, it is highly toxic to humans, animals, and the environment when not handled properly.
The solution replaces cyanide with a safe, alternative reagent known as thiosulphate. Thiosulphate dissolves the fine gold out of ores (the gold that has not recovered by gravity) at similar rates to conventional techniques. It's safe and lowers environmental impacts.