Two commercially available nanofiltration membranes (NF99HF, NP010) were investigated in order to separate In and Ge from pregnant leaching solutions (PLS) resulting from a bioleaching process. The PLS contains Zn, Cu and Fe as major components while In and Ge are minor constituents. In and Ge are assessed as critical raw materials (CRM) by the European Commission since there reliable and unhindered access is of growing concern for the European economy. NF experiments were conducted in cross-flow mode for model solutions containing equal concentrations and a model PLS at pH 2, respectively. Experiments with model solutions of increasing solute content revealed a negligible effect on ion retention and permeate flux. In order to discuss transport phenomena, diffusion coefficients of In3+ and Ge(OH)(4)(0) were researched or estimated. Ge(OH)(4)(0) revealed high diffusivity and hence mass transfer is primarily favored due to its low diffusion resistance. Owing to its Stokes radius which is greater than all the other species considered, In3+ revealed noticeable steric hindrance beside electrostatic interactions. The considered membrane NF99HF is able to selectively separate In and Ge in a PLS by accumulating In, Zn, Cu and Fe in the retentate, while Ge is enriched in the permeate.