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ePaper created 2013-09-24, 11:56:35 | version 1.25.20
98 MOLECULAR SORTING – RECOVERY OF METALS Dr. rer. nat. Thomas Schiestel, Dr. rer. nat. Iris Trick, Alexander Karos M.Sc. Waste as a source of raw materials The recycling of raw materials, in particular special metals, because of their value (precious metals), their availability (rare earths) or their toxicity (heavy metals) is of great importance, both for industrial production and for the environment. Pro- cess and wastewater streams, for example from alkaline so- lution baths in the electroplating industry, and also landfill leachate, may contain significant quantities of dissolved met- als. Also in the recycling of solids such as waste electronic equipment or ashes from combustion processes, the dissolu- tion of metals (leaching) in bioreactors (bioleaching) can be an efficient method of transferring these metals to an aqueous solution. After that, further processes such as “enrichment”, “separation” and “deposition” are necessary to recover a uti- lizable metal. The design of these process steps is of decisive importance for the efficiency and sustainability of the whole process. Need for new technologies Economical and ecological efficiency on the industrial scale is only possible to a limited extent with the technologies avail- able today, especially when there are only low concentrations of the metal ions in a solution. Of course, there are technolo- gies for the selective separation of individual metals from a solution. However, these technologies are generally very cost- intensive, and neither environmentally friendly nor universally ENVIRONMENT 1 A 1 B Process chain for an efficient recovery of metals 2 SELECTIVE DISSOLUTION Bioleaching of metal containing materials Adsorptive concentrating SELECTIVE ENRICHMENT Selective separation by means of free-flow electrophoresis Reduction/deposition of metal ions SELECTIVE SEPARATION METAL