Preparation and characterization of positively charged polysulfone nanofiltration membranes

Charged nanofiltration (NF) membranes were prepared from aminated polysulfone (APSF) via a phase inversion technique, by varying the polymer and solvent weight ratios. A two-step phase inversion technique, adopted for the preparation of NF membranes, involved chloromethylation, and subsequent amination of the polymer, polysulfone (PSF). Fourier-transform infrared (FT-IR) and proton nuclear magnetic resonance (H-1-NMR) spectroscopic analyses of the prepared chloromethylated PSF (CPSF) membrane confirmed the incorporation of chloromethylated groups on the polymer backbone. Also, the separation capability of the prepared membranes was evaluated by compaction studies, pure water fluxes (PWF) at different pressures, and hydraulic membrane resistance measurements. Furthermore, scanning electron microscopic (SEM) and atomic force microscopic (AFM) images revealed that the pore size and pore distribution decreased with increase in the polymer weight ratio. In addition, the functionality of the prepared membranes as a nano-filter was analyzed by constructing a stirred batch NF cell and evaluated towards a feed solution containing different concentrations of Cr (III) ions. The performance of the prepared membrane was compared with commercially available (NFT-50) NF membrane.