What Is the Process of Refining Silver?
Silver is found embedded in several different minerals, namely copper, zinc, and lead, and the refining process varies depending on the source. Silver derived from copper and its derivatives, including copper sulfide, requires different handling and refining techniques than silver minerals taken from zinc deposits and lead sources. These metals have different physical properties, which accounts for the different methods needed for proper extraction.
However, silver can also come from two other sources – recycling and silver mining. Old pieces of jewelry can be repurposed into brand-new accessories at silver recycling centers. Silver miners aim to find “native silver” – the absolute rarest and purest form of silver available. In those sparse occasions when native silver is found, nuggets are smelted down in devices like muffled furnaces at 2100 degrees Fahrenheit.
There are actually many different methods for refining silver – each with its own pros and cons. Pyrometallurgical processes center around melting metals, as the name implies. Calcining is a pyrometallurgical process wherein organic compounds and sensitive, often volatile materials are burned off the silver.
There’s also the Electrorefining process – wherein a silver anode is subjected to electrolysis in low-acid silver nitrate to produce pure silver crystals. This is a very simplified explanation of a complex process. Suffice it to say that electrorefining typically produces some of the highest quality silver available.
Lastly, Electrowinning is another well-known and effective process for refining silver. Using a pump, rectifier, and tank, one can produce high-quality silver frequently and reliably. Modern electrowinning processes incorporate sophisticated cylindrical cells that drastically improve mass transfer rates. The result is a high purity product (silver in this case) that lacks impurities.