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discovered_01_2013

COLLABORATION// The HZDR Research Magazine WWW.Hzdr.DE 36 37 Saxony’s ore mining industry ceased operations early in the 1990s but large residual amounts of metals like tin, zinc, and lead exist to this day. They are contained in the remnants of mechanical and chemical processing of the ore that ultimately ended up inside tailings dams. "Archival data tell us that up to 50 percent of the original quantities of tin are being stored there," says Philipp Büttner of the Freiberg Helmholtz Institute. The project he coordinates is entitled "Strategic Metals and Minerals from Saxony’s Mine Tailings." As part of the project, researchers from the TU Bergakademie Freiberg and their industry partners are hoping to determine the exact amounts and distribution of raw materials inside the tailings and how to recover them. The project is part of a larger program funded by the Federal Ministry of Education and Research (BMBF) that is concerned with the recycling and replacement of industrially relevant raw materials ("r3 " – Innovative Technologies for Resource Efficiency – Strategic Metals and Minerals). In today’s economy, resources that didn’t hold much appeal in the past have suddenly become economically attractive. "Back then, nobody gave high-tech metals like indium, germanium, and lithium much thought and their occurrence and distribution were rarely studied," explains Büttner. "However, we suspect that the residual amounts that were produced during ore processing and that are now stored inside the tailings do include these high-technology metals. We’re trying to find out how much of it is stored there and what the distribution is." The researchers have to carefully study the tailings and analyze large numbers of samples because in many cases the raw materials that are key ingredients of generators, batteries, and television or computer screens have a complex distribution and occur in only small concentrations. Frequently, the minerals that contain the metals in question can only be seen using high-resolution microscopes or special probes. The HIF and the TU Bergakademie Freiberg have all the necessary analytic equipment available for these kinds of investigations. This cutting-edge equipment was funded by the BMBF and the Free State of Saxony. According to Anke Dürkoop, "it is available to all members of the "r3 " program, who are given preferential treatment, but other HIF research partners are also welcome to use the equipment." Dürkoop coordinates another project of the "r3 " initiative at HIF called "INTRA r3 +," which links up the 27 separate "r3 " projects. "Thanks to the HIF equipment pool, we have several options for quantitatively characterizing raw materials." Under the electron beam A number of research facilities are all working in parallel as part of the tailings project. At this point, the sample material, which was obtained from several different tailings in Saxony’s Ore Mountains, is still being stored inside buckets or packed inside PVC pipes. Soon, it will hit the research labs. Inga Osbahr of the TU Bergakademie‘s Institute for Mineralogy is one of the first to work with the samples. Osbahr’s job is to screen prepared mixtures of fine and coarse grain sand particles using a scanning electron microscope. The X-ray radiation that is reflected by the minerals in the process is unique for each mineral. This allows the researcher to learn about the composition of the materials inside the tailings and which minerals occur in combination. However, the method does not allow for an identification of the materials’ distribution patterns. For that, the samples would have to be split into their atomic building blocks using high heat and then analyzed with the help of a highly sensitive mass spectrometer. An X-ray powder diffractometer can then be used to assess the samples’ constituent elements in order to determine the minerals’ exact structure. Finally, the data are entered into a super-regional database along with related info from other German mine tailings. This tailing registry of sorts is being co-developed by several "r3 " partners. In the end, the data will show whether it is ecologically compatible and economically feasible to use the remaining raw materials that are currently stored inside the tailings. Progressive technologies could also play a role in the decision-making process. The researchers’ guess is that they will know more within three years’ time, which is how long their investigations will run for. VALUABLE SOIL: At the beginning of this year, Philipp Büttner and Inga Osbahr obtained soil samples from several former tailings dams in Saxony's Ore Mountains. The material that is thought to contain remnants of important industrial raw materials is prepared for measurement by Thomas Leißner (from left to right). Photo: VNG - Detlef Müller ContaCt _Helmholtz Institute Freiberg for Resource Technology at HZDR Philipp Büttner Coordinator of the joint project "Strategic Metals and Minerals from Saxony’s Mine Tailings" p.buettner@hzdr.de Dr. Anke Dürkoop Coordinator of the BMBF Networking Project "INTRA r3 +" a.duerkoop@hzdr.de www.r3-innovation.de

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