Microscopical characterizations of nanofiltration membranes for the removaludof nickel ions from aqueous solution

摘要

The nanofiltration (NF) process is electrostatically governed and the surface free energy plays a key role inudthe separation of particulates, macromolecules, and dissolved ionic species. Streaming potential measurement and theudsurface charge mapping by Kelvin probe atomic force mircoscopy (AFM) have been carried out. Forces of interactionudnear the surface of nanofiltration membranes were further studied by a force spectroscopy using atomic force microscopy.udThe two membranes used are more negatively charged at high pH values; hence the higher the solution chemistry,udthe higher and faster will be adhesion of ions on the surface of the nanofiltration membranes. It was observed thatudthe three acquired signals from non-contact AFM (contact potential difference, amplitude and phase) were rigorouslyudconnected to the surface structure of the nanofiltration membranes. In addition to the surface structure (roughness),udelectrostatic interactions can also enhance initial particle adhesion to surfaces of nanofiltration membranes. The performanceudof the NF membranes was further investigated for the removal of nickel ions from aqueous solution, and theudresults were correlated to the mechanical responses of the nanofiltration membranes obtained from AFM and the streamingudpotential measurement.