How to recover gold from aqua regia
Those who want to learn gold recovery process from e-waste, extensively use the keyword, how to recover gold from aqua regia. This is because most people have the conception that aqua regia process is the only and the best method to extract gold from e-waste. The fact is that there are many methods to remove gold from e-waste, and aqua regia is also one of them. When we choose a method to remove gold from e-waste, the first thing that has to be kept in mind is the economic viability and the easy availability of the material or chemicals used in the gold recovery process.
Undoubtedly, the aqua regia method is an easy gold recovery process. To prepare aqua regia we need to mix one part of nitric acid and three parts of hydrochloric acid. These acids are very corrosive and produce toxic fumes. So, while mixing them, we should be careful to avoid splashing as it might cause burns. In case we happen to have some splashes on our body, we should immediately wash them with plain water.
Jewelers, normally use aqua regia to get their gold from old jewelry, scrap jewelry pieces, filings and jewelry bench work etc. . . One kilogram of scrap jewelry can be digested by 3.5 liters to 4.5 liters of aqua regia. Either Teflon plastic or glass can be used for aqua regia gold recovery method. First gold scrap should be placed in the digesting pot and then aqua regia should be poured onto it slowly and carefully. The scrap metal starts dissolving into the aqua regia. The aqua regia is poured till the whole metal is dissolved. The solution is filtered after the metal is digested. If only gold metal is present in the filtered solution, the color of the solution is yellowish, if other metals such as copper and nickel, etc. are mixed in the solution; the color of the solution is green. We should neutralize the excess nitric acid from the solution to ensure easy and complete precipitation of gold. It is either done by boiling the solution to almost dryness or by adding some chemical that neutralizes the nitric acid.
By now you have got only half the answer to how to recover gold from aqua regia. Precipitating hundred percent gold from the gold chloride solution is not as easy as it sounds. Many precautions are taken to ensure the complete recovery of gold from the aqua regia solution, and, the correct choice of the gold reducing chemical is also very important part of this gold recovery process. Sometimes, some particles of other metals also settle to the bottom with gold dust due to some reasons. In that case, the whole process may have to be repeated to ensure the maximum purity of gold.
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