Precious metal separation
Precious metal divorce ( English Precious Metals Refining ) is a generic term for the separation of precious metal-bearing raw materials. The precious metals are extracted from used catalysts , electronics , ores or alloys , for example . Precious metal separation is a costly and laborious process.
Procedure
In order to recycle materials containing precious metals, pyrolysis processes, wet chemical processes or a combination of both are used.
In pyrolysis, the precious metal-containing products are freed from the lower accompanying materials by pouring them into a melt as slag or by eliminating (oxidizing) them according to the incineration principle.
In the wet chemical process, the products containing precious metals are either dissolved in aqua regia (consisting of hydrochloric acid and nitric acid ) or dissolved in chlorinated hydrochloric acid. One therefore speaks of the digestion process . Then certain metals can be precipitated or reduced directly in connection with a salt, gas or an organic and / or amine-containing compound. For example, gold is reduced with the gas sulfur dioxide or platinum (as tetrachloridoplatinate) is precipitated with ammonium chloride. Depending on the purity of the salt complex, the color varies between light orange and sand yellow. They then go through certain intermediate purification stages or are recrystallized again. At the end, the precious metal is released from the precious metal-salt compound either by calcination , (melting) electrolysis or extraction with special chemicals.
In most cases, both methods are used. The materials containing precious metals are first thermally decomposed ( pyrolysis ) and then processed using wet chemical methods. This happens especially when it comes to catalysts from the chemical sector or the customer wants a particularly high level of purity of the metals, because these materials usually also contain other metals and foreign substances that disrupt the refining process or drag it on. The catalysts themselves can also consist of several (precious) metals. For this reason, the individual (precious) metals are removed step by step from the recycling product and recycled several times.
The intermediate and end products are constantly checked for content and purity. This is the only way to ensure that the customer is first and foremost properly remunerated for the metals, and also that the customer ultimately gets the desired product. Loss of precious metal and poor quality are severely punished by customers in this expensive and tough business. For example, the recycler has to compensate for the losses with his own resources and the customer will look for a new recycler. It is not uncommon for a "sampler" to be present during the entire recycling process. On behalf of the customer and recycler, this documents every process as a kind of arbitrator.
Products
Mostly silver and gold are separated, followed by platinum , palladium and rhodium . Iridium , ruthenium , osmium and rhenium are rarely recycled. At the moment, however, the demand for ruthenium is increasing as it is used to coat smaller, more powerful hard drives .
Market participants
These high-quality materials and work are only entrusted to companies that specialize in this and have a good repute and good bank ratings . This is one of the reasons precious metals trade like foreign exchange. These metals are re-assessed daily ( fixing ). As is customary in the industry, most precious metal recyclers have an integrated precious metal trade, which in principle works in a similar way to a bank. So-called precious metal accounts are kept there, on which there is even some interest .
Individual evidence
- ↑ Umicore: Precious Metals Recycling - Status and Developments ( Memento of July 17, 2013 in the Internet Archive ) (accessed on May 1, 2011; PDF; 520 kB)