Commercial Refining of Precious Metals

Precious metal refining refers to the separation of the precious metals from the noble metal containing materials. These materials are chemically called ores or scrap. The most precious metals include gold and silver. These two metals have a very strong position in the development of any nation. So, the improvements in their refining process are the most interested subject of the alchemists and metal smiths. Hence, on the commercial scale, such methods are employed that are economically manageable and have reduced chances of the precious metal loss, during the refining process.

The commercial process of refining is a multistep process. The first and the most important step is the receiving of the sample. The source of the sample is of key importance. Many geologists predict potential percentage of the precious metal in the scrap. The sample from that location is provided to the refining plants. When the sample is received at the refineries, they are weighed by the standardised calibrated scales.

After receiving, the sample is prepared for further processing. The professionals examine the sample and prepare the best sampling preparation process, based on the type of the received material. The further processing may involve incineration, milling, screening and smelting processes.

These processes give initial information of the type and the amount of required material. This step is followed by the melting of the scrap in an electric induction furnace. This is then sampled in the molten state in the vacuum glass tubes. After the process of melting, the dust is blended by the use of a rotating blender.

The treated material is then subjected to assaying. This assaying determines the amount and the type of the material present. On the other hand, the removal of the impurities still carries on along with the process. In this process, the material is oxidised to remove the impurities like copper, lead and iron, in the form of their respective oxides.

It is then subjected to the traditional weighing procedure or the mass spectrometry. It is the latest and efficient technique. After the spectrometry, the assay data is entered into the computer network. The computer then calibrates the actual precious metal content present in the sample.

The next step is the isolation of the precious metals. For this purpose, various procedures are used. One of the procedures is pyrolysis. This process involves the solidification of the impurities. After this process, the melted required material can be separated. The solidified material is called slag. The other form is the oxidation of the impurities. Refining can also be done with hydrolysis procedures. This includes the addition of aqua regia. It is chemically composed of hydrochloric acid and nitric acid in a definite proportion. It has the ability to dissolve gold in it. The dissolved gold is then obtained through further processing.

The responsibility of the commercial refineries does not end here. After the extraction of a particular metal, the leftover material is then subjected to a further refining process. In such steps, the non-precious metals are generally obtained. Thus, no or very less material ends up in the landfills.

Source by Jack Wogan

Commercial Refining of Precious Metals