Effect of non-solvent additives on the morphology and separation performance of poly( m -phenylene isophthalamide) (PMIA) hollow fiber nanofiltration membrane

Abstract

• PMIA hollow fiber NF membranes were fabricated.• Effects of non-solvent additives on the morphology and separation performance were studied.• High content of non-solvent additives resulted in narrow pore size, pore size distribution and high rejection. Newly designed poly(m-phenylene isophthalamide) (PMIA) hollow fiber nanofiltration membranes were fabricated containing non-solvent additives, i.e., lithium chloride (LiCl), acetone and PVP by dry-jet wet spinning technology. The effects of non-solvent additives on the morphology and separation performance were investigated. The addition of non-solvent additives in the dopes enhanced the viscosity significantly. The membrane crosssections were monitored by scanning electron microscopy (SEM). The results indicated that by increasing the concentration of non-solvent additives, the morphologies changed from finger-like to sponge-like, and the outer skin-layer thickness was slightly increased. The rejections to various salts and pure water permeability (PWP) of these membranes were determined. The mean pore size and molecular weight cut-off (MWCO) were estimated using the solute rejection method. The results showed that the salt rejection of the membranes decreased in the order of R(Na 2 SO 4 ) N R(MgSO 4 ) N R(NaCl) N R(MgCl 2 ), and as the concentrations of non-solvent additives increased, the PWPs, mean pore sizes and MWCOs of the PMIA membranes all decreased. The atomic force microscope (AFM) experiments demonstrated that a smooth membrane surface was formed by adding non-solvent additives. Furthermore, the stress values at break, the elongation at break and the elastic modulus of the fibers increased as non-solvent additive contents increased. a b s t r a c t a r t i c l e i n f o

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Preparation and application of zinc oxide/poly(m‐phenylene isophthalamide) hybrid ultrafiltration membranes

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