Performance of a thin-film composite polyamide nanofiltration membrane has been studied to separate cadmium ions from aqueous solutions. The operating variables studied are pressure, concentration and feed flowrate. It is observed that the solute rejection increases with increase in applied pressure and decreases with increase in feed concentration at constant feed flowrate. The maximum observed rejection of the metal ion is found to be 82.87 and 64.86% for feed concentration of 5 and 250 ppm, respectively. Cadmium ion rejection is sensitive to pH change. Membrane transport parameters and mass transfer coefficients are estimated using different models.
Keywords: nanofiltration, rejection, flux, cadmium separation, membrane transport models, thin-film membranes, composite polyamide membranes, mass transfer, water pollution