Removal of ions in nickel electroplating rinse water using low-pressure nanofiltration

This study investigated the performance of nanofiltration (NF), which is mo re economic than reverse osmosis (RO) and requires lower pressure for the r emoval of cations and anions in simulated nickel electroplating rinse water environments. Removal rates according to changes in basic parameters such as pressure, crossflow velocity, pH, ion types and ion concentrations were observed. In single-salt system experiments NF removed more Ni2+ in NiSO4 s olution than in NiCl2 solution. As concentration increased in single-salt s ystems, removal rate of sulfate salts and some chloride salts tin the syste m with cations of +1 valency) decreased, whereas chloride salts with cation s of +2 valency increased. In the experiment with multi-salt systems, the r emoval rate of ions showed a logarithmic increase with pressure until 3 kgf /cm(2) (0.294 MPa), and beyond this value the removal rate stabilized. Chan ge in crossflow velocity did not affect the ion removal, but change in pH w as a significant factor for Cl- removal rate. Furthermore, the removal rate of Cl- was heavily dependent on the amount of SO42- present in the same sy stem. In experiments using simulated nickel electroplating rinse water belo w a pressure of 3 kgf/cm(2), the removal efficiencies of ions increased gre atly with increased influent salt concentration and pressure, whereas beyon d 3 kgf/cm(2), the removal efficiency stabilized. This result indicated tha t 3 kgf/cm(2) is the optimum pressure for NF application against nickel ele ctroplating rinse water.