In this paper, nanofiltration (NF) polymer membranes based on polyestersulphone (PES) were prepared by the phase inversion method. Polyethyleneimine (PEI) and zinc nitrate (Zn(NO3)2) as a surface modifier and glutealdehyde (GA) as cross-linker was used. Fourier transform infrared spectroscopy analysis (FTIR) was used to confirm the chemical composition on the membrane surface. Membranes were also characterized using field emission scanning electron microscopy (FESEM) and 3D surface images. Water contact angle, average pore size and porosity measurements, water flux, salt rejection, and membrane anti-fouling ability were discussed. Modified membranes showed a smoother surface than the original membrane. The amount of pure water flux decreased with increasing the concentration of modifiers at the surface, but the yield of Na2SO4 salt increased, 53% in virgin membrane and 83% in M3 membrane. Modified membranes had better anti-fouling and hydrophilicity properties than primary membranes. The lowest contact angle value was 26.2 for M4. Also, the best anti-clogging comparable properties were for the M3 membrane with FRR = 63.37%, Rr = 10.69%, Rir = 36.6%, and Rt = 47.3%. By increasing the concentration of modifiers, the removal of CuNO3 and CuSO4 improved that the M1 membrane (97.59%) had the highest Cu(NO3)2 separation and the M4 membrane (87.5%) had the most increased CuSO4 separation.
