Spiral-wound polyaniline membrane modules for organic solvent nanofiltration (OSN)

Spiral-wound modules of solvent stable integrally skinned asymmetric nanofiltration membranes made from polyaniline (PANI) are reported. PANI membranes were made by phase inversion and crosslinked by chemical and thermal processes. In the chemical crosslinking process, PANI membrane cast on polypropylene non-woven backing was crosslinked using glutaraldehyde, and a 1.8 in. spiral-wound module was prepared. To crosslink membranes thermally, a 1.8 in. spiral-wound membrane module prepared from PANI membrane cast on polyester non-woven backing was heated at 180 °C for 2 h. The resultant membranes and modules were found to be stable in various organic solvents including acetone, tetrahydrofuran and N,N-dimethyl formamide. Filtrations carried out in acetone, tetrahydrofuran and dimethyl formamide gave stable permeate fluxes and good separation performances in the nanofiltration range. Molecular weight cut-off (MWCO) of the membranes was dependent on the nature of the solvent and temperature. MWCO of PANI membranes in different solvents was found to lie between 150 and 300 g mol−1 at 30 °C. The membranes were also found to be stable for operations at elevated temperatures up to 65 °C and possibly higher. These membranes retain their nanofiltration properties even after drying so the use of conditioning or preservative agents can be avoided.