2012|13 Annual Report Fraunhofer IGB

102 Electrophysical processes For the fractionation and subsequent deposition of the various metal ions as a metallic solid we give preference to further de- veloping electrophysical processes such as electrophoresis and galvanic deposition. For the separation of various metal ions in solution we have developed a laboratory prototype that works on the principle of free-ﬂow electrophoresis (Fig. 10). This pro- cedure also permits the separation of metal ions which are very similar due to their chemical and physical properties and which can therefore only be separated to a limited extent us- ing conventional technologies (e.g. rare earth ions). The experiments to date conﬁrm the feasibility of a fractiona- tion with a high degree of selectivity of the metal ions. Here, for example, the metal ion mixtures copper-iron, neodymi- um-iron and the three-component mixture iron-copper-ne- odymium were separated (Fig. 11). In the case of the two- component mixtures we were able to increase the purity of the fractions to over 90 percent by means of a single cycle. In order to increase the efﬁciency even further, complexing agents were used, resulting in an almost complete separation of the substance mixtures. A transfer of the proven successful separation to other systems of substances is planned for sub- sequent experiments. For the deposition of rare earths and metals following the fractionation, suitable ionic liquids were chosen as electro- chemically stable electrolytes. In order to test the application, a trial setup including a reactor system was developed. First experiments to investigate the stability of the selected ionic liquids were carried out successfully and, compared with wa- ter, they show a very broad electrochemical window (Fig. 12). ENVIRONMENT Sample Buffer Anode buffer Cathode buffer – + Power supply (DC) Separated fractions Outlet Buffer inlet Sample inlet Electrode chamber with electrodes Blue, red and green samples: cations with different properties Separation chamber 10 11 Pure fraction Neodymium 65 % Pure fraction Iron 43 % Three- component mixture iron- copper- neodymium Mixed fraction (contains Copper) Pure fraction Neodymium 80 % Pure fraction Iron 53 % Two- component mixture neodymium- iron Mixed fraction Pure fraction Copper 71 % Pure fraction Iron 63 % Two- component mixture copper-iron Mixed fraction

2012|13 Annual Report Fraunhofer IGB

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