Advanced biotechnology for extraction and recovery of metals


Advanced biotechnology for extraction and recovery of metals

Raff, J.; Lehmann, F.; Moll, H.; Kutschke, S.; Pollmann, K.

In an era of dwindling resources and rising prices new procedures for the exploitation, beneficiation and recycling of especially industrial relevant metals are in demand. Such elements are essential for modern high tech industry and development of future techno¬logies. Interestingly, nature itself offers promising approaches in these fields. Some organisms are thusly able to mobilize metals not only from ores but also from electrical and electronical equipment waste by bioleaching [Bosecker K. 1997, Brantley et al. 2001, Brandl H. et al. 2001]. Bioleaching is already used for the large scale production of copper especially in ores with low metal content. Furthermore, other species or biomolecules are able to selectively bind and accumulate metals [Pollmann et al. 2006], allowing the con-struction of metal selective filter materials. In addition, some organisms trigger the formation of minerals or are able to form different kinds of biominerals by themselves, representing also a way to separate metals [Wang X. and W.E.G. Müller 2009]. In combination with established physical and chemical processes, such biotechnological approaches have a high potential to improved metal beneficiation and recycling.
Within the biotechnology group at the Helmholtz Institute Freiberg for Resource Technology such new procedures for extracting, treating and recycling metals such as copper or rare earths using microbes are under development. Whereas the bioleaching related research is just at the beginning and the investigation of biomineralization pro¬cesses for metal separation is planned for the future, the group has long-term experience in the investigation of the interaction of metals with biomass and especially in the selective metal binding by proteins and other bioligands. Within radioecological research, bacterial isolates were investigated that possess so called surface-layer (S-layer) proteins, forming a closed protein lattice on many bacteria and archaea protecting the cells from being affected by environ¬mental influences. In case of such bacteria living in highly heavy metals contaminated environments, their S-layers have high metal binding capacity and high stability. Furthermore, they possess different metal binding sites. There are many less specific binding sites, binding large amounts of precious metals such as Pt, Pd and Au as well as radioactive metals such as U. Metals such as Fe, Co, Ni, Cu and Zn are not bound or only in small quantities. In addition, there are several highly specific binding sites, binding Ca, Cm and Eu. First results indicates, that the binding affinity of these metals differs significantly. As the metal binding additionally depends on the pH and differs from metal to metal, S-layer proteins possess a high application potential for the specific separation of industry relevant metals.

Keywords: Biotechnology; biosorption; bioleaching; metals

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Publ.-Id: 17840