Industrial wastes such as slags, dust, or precipitation residues contain significant amounts of valuable metals like zinc, lead, and copper as well as precious metals like silver and indium. Nevertheless, a lot of these waste materials are not recycled, and therefore, many valuable metals end up being sent to landfills. Because of harmful components in the waste, it is often necessary to send it to specialized landfills for hazardous wastes, which leads to environmental problems as well as additional costs. Consequently, the recovery of the valuable metals from the residues represents a sensible task to decrease the negative impact on the environment and to reduce costs for maintaining a landfill. In addition, recycling helps to decrease the dependency from primary resources. The present study deals with the behavior of different metals in a pyro-metallurgical treatment for a mixture of jarosite and electric arc furnace dust with a special focus on indium and silver.

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Elements defined as critical by the European Commission, like platinum group metals (PGM), indium, cobalt, gallium, silver, gold, germanium and antimony are often contained in copper-, lead-and zinc-ores. During the metal production process of the above-mentioned base metals different residues accumulate, which can contain these critical elements as well. By depositing thousands of tonnes of these residues from the metallurgical industry, the contained valuable metals are no longer available. Next to that the security of supply in Europe for especially those metals is bad. Due to these problems and an increased environmental awareness, the recovery of critical elements from residues gets more and more important. Because of carrying high amount of silver and indium, the precipitation residue jarosite or also neutral leaching residue from the hydrometallurgical zinc production are potentially interesting for reprocessing. By adding of different additives and a treatment at higher temperatures, critical elements as well as other valuable metals get vaporized in various chemical compounds. If the mentioned metals are recovered successfully during a recycling process it can contribute to the overall production economy. The paper summarizes carried out thermochemical calculations investigating a possible recovery of silver as well as indium in a pyrometallurgical process by selective vaporization.