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ePaper created 2016-03-17, 15:06:18 | version 1.45.01
8 8 Recycling magnet material Under the Fraunhofer Lighthouse Project entitled “Critical Rare Earths”, Fraunhofer IGB has been responsible for Work Package 7 entitled “Recovery of Rare Earth Metals from Permanent Magnets and Industrial Waste”. It has set itself three goals to be met by the Midterm Meeting with its project partners. Firstly, sintered magnets from used electric mo- tors should be recycled in such a way that the reprocessed granulate can supplement primary magnet production by at least ten percent without having an impact on the properties of the new magnets produced. Secondly, the extent to which this recycled granulate can be utilized for manufacturing composite magnets comprising granulate with a polymer binder should be tested and proven nd finally, magnets and/or particulate material arising from production should be physically processed in such a way that metal oxides or metals are recovered, which can then be re-introduced as recycled industrial feedstock in a production process. Physical processing All milestones and objectives were successfully reached. Fraunhofer IGB’s priority in the research project was to focus on the area of physical processing. The most important results from the three technologies investigated and developed are presented below. Bioleaching Bioleaching involves processes that have been known for thousands of years in metal mining and can be employed for processing tailings that contain metals using contemporary biotechnology. Prior to commencement of the project, howev- er, little was known about suitable strains of microorganisms that might be employed for processing used magnets and ideally for leaching out neodymium specifically The research group therefore investigated known bacterial strains as well as organisms isolated from soil samples and evaluated them with regard to their ability to liberate and accumulate neodymium at the laboratory scale. Both stirred and fi ed-bed bioreaction vessels were employed for this suitable mixed population of various aerobic soil bacteria was enriched and isolated from the soil samples, characterized and visualized by scanning electron microscopy. In an aerobic process at laboratory scale we could show the microbial popu- lation liberating neodymium from used magnets. Summary: An aerobic process using a suitable heterogeneous microorganism population was set up and demonstrated that this is capable of specifically liberating and accumulating neodymium. Membrane adsorption Membrane adsorbers were able to be produced in the form of both film membranes and membranes constructed of hol- low fibers The active adsorber layer was introduced in the form of modified particles ig shows M images of a film membrane with particle loading of 40 percent by weight. The membrane thickness is 107 ± 9 µm. Different particles were tested as adsorber materials. Fig. 1 shows a selection of the chemically functionalized particles employed. FRAUNHOFER LIGHTHOUSE PROJECT “CRITICAL RARE EARTHS” Uwe Vohrer, Thomas Schiestel, Klaus Niedergall, Christopher Hänel, Thomas Scherer, Max Kotzur, Lea König, Gabriele Beck-Schwadorf, Susanne Größchen, Hedwig Pilgram, Iris Trick 1 2 adsorbedmetalmassing/m2 volume of metallic solution in L 0,0 1,0 2,0 3,0 4,0 2,0 0,0 0,5 1,0 1,5 30 % w/w 40 % w/w REF particle chemical function possible targets –COO– carboxyl weak cation-IEX (heavy) metals –SO3 – sulfate strong cation-IEX (heavy) metals –NH2 amine weak anion-IEX arsenate, diclofenac-Na –NMe3 + quaternary ammonium strong anion-IEX Penicillin G K salt –PO3H– phosphonate complex-forming rare earth materials, iron, aluminium –NHSNH2 thiourea affinity noble metals – heteroaromatic hydrophobic adsorption bisphenol A – aromatic hydrophobic adsorption carbamazepine 88 12 0,01,02,03,04,0