Since decades, the demand of strategic elements is increasing. On the one hand, the industrialization of emerging countries is advancing due to the desire of a higher standard of living. On the other hand, the technical progress of the industrial countries leads to an enhanced provisioning of raw materials, such as strategic elements. Therefore, the supply is becoming increasingly difficult and supply bottlenecks might occur. Hence, the potential of secondary mining has to be exploited to uncover yet untapped resources. In the present study, the potential of a Theisenschlamm mono-landfill, a residue of German copper smelting with various strategic elements (e.g. Co, Ge, Mo, Re, Sb) included, shall be illustrated. By means of a hybrid process, consisting out of bioleaching and downstream processing, the target elements shall be mobilized and processed. As part of the element-specific procedures, the presented study investigates the applicability of nanofiltration to separate mono- and divalent metal ions in aqueous solution. Three thin-film polymeric nanofiltration membranes were investigated to determine the pH-dependent separation performance of Ge, Mo, and Re. Membrane screening experiments were conducted in dead-end set-up (15 bar, 25 °C) with the single and combined elements and aimed at identifying a suitable membrane for the proposed cross-flow set-up. The results demonstrate that rhenium could be separated from the multicomponent solution by the utilized RO90 membrane, which accounts for a market potential of approx. 19 Mio. $.