Preparation and characterization of nanofiltration composite membranes using polyacrylonitrile (PAN). I. Preparation and modification of PAN supports

Polyacrylonitrile (PAN) supports useful for the formation of nanofiltration (NF) composite membranes were prepared from PAN solutions in N-methylpyrrolidone (NMP), using a phase-inversion method. The compositions of the PAN/NMP solutions used were as follows: 10/90, 15/85, and 20/80 (in wt %). The PAN supports were treated with various concentrations of NaOH aqueous solutions (0.1, 0.5, 1, and 2 mol) for certain periods of times (0.5, 1, 2, and 3 h) in order to modify their surface chemically and morphologically. The characteristics of the supports, modified or unmodified, were carefully studied. The morphology of those were observed with field-emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). The change of the chemical structure of those by the NaOH treatment was studied using FTIR-ATR spectroscopy and ESCA. The permeation properties of those were also determined at 1-5 bar of operation pressure using a PEG 35,000 aqueous feed solution. (C) 2001 John Wiley & Sons, Inc.