Whey is a highly polluting by-product obtained from the elaboration of cheese. Its high content in organic matter, mainly proteins and lactose, makes it a valuable candidate for multiple applications in the food industry. However, mineral salts have to be previously eliminated. The main objective of this work was to eliminate mineral salts from model solutions with different nanofiltration membranes: NF200, NF270, Ds-5 DK and Ds-5 DL polyamide. Although all four membranes showed fairly good results in the demineralisation of the used samples, the most promising results in terms of good permeate flux and low solute retention were obtained with the NF200 and Ds-5 DL membranes, respectively. The effect of the salt mixture concentration on permeate flux and solute retention was further evaluated for Ds-5 DL membrane.