Nanofiltration (NF) has attracted increasing attention over the recent years due to the development of new applications. This paper presents the separation of heavy metal ions such as nickel from synthetic wastewater of nickel electroless plating industry. The wastewater from nickel electroless plating industry contains various metals such as nickel, sodium, magnesium and zinc. In order to ascertain the effect of ion rejection in a mixed salt system, the rejection behaviour of nickel ion in synthetic wastewater of Na2SO4, NiSO4, MgCl2 and CaCl2 is tested by using NF300. The maximum observed solute rejection of nickel ion is 97.96% and 96.87% for an initial feed concentration of 5 and 10ppm, respectively. The NF300 membrane is characterized by using combined film theory-Spiegler-Kedem (CFSK) model based on irreversible thermodynamics and ion transport model based on the extended Nernst-Planck equation. Boundary layer thicknesses, enrichment factors, concentration polarization modulus as well as membrane transport parameters are estimated by using the Levenberg-Marquadt method. The estimated parameters are used to predict the membrane performance and found that the predicted values are in good agreement with the experimental results.