Tailoring of Narrow Pores, Pore Size Distribution and Structural Details in Asymmetric Nanofiltration Membranes via Polyvinyl-pyrrolidone Additive

Abstract

The roles of polyvinyl-pyrrolidone (PVP) additive in the tailoring of pores, pore size distribution, morphologies and molecular weight cut-off (MWCO) in phase inversion asymmetric nanofiltration membranes was addressed. Using established solute transport method, scanning electron microscopy (SEM) and Minitab software, details analysis of the enhanced performance-properties of narrow pores nanofiltration membranes were verified. Experimental and analysis data revealed that the membranes prepared with 2 wt% of PVP demonstrated fine performance-properties. At this concentration, the fabricated nanofiltration membranes possessed narrow pore size and molecular weight cut-off of 1.14 nm and 2290 Da, respectively. In addition, the fabricated nanofiltration membranes displayed fine structural details of narrow pore size distribution, good morphology and critical key properties. With the combinations of thinner skin layer, fine structures and narrow pores, it can be concluded that the 2 wt% of PVP is the optimum PVP concentration to produce selective narrow pore nanofiltration membranes. Eventually, summary data on pores, pore size distributions (PSDs) and key properties proved that the PVP additive is effective for controlling performances-properties and structural details in asymmetrical based membranes.

Elucidation on Performance and Structural Properties of Skinned Asymmetric Nanofiltration Membrane Based on Theoretical Models

“…It was revealed that at higher polymer concentration the narrower pore size distribution was produced. Hence, high polymer concentration (> 20 wt%) not only improved the membranes performances but also produced good membranes characteristics as well as the narrowest pore size distribution as reported by other researchers [9,18,32].…”

“…A skinned, thin and dense asymmetric nanofiltartion (NF) membrane could be prepared by using dry/wet phase inversion technique [4,5]. In this technique, the formation of fine skinned membranes depends on two major factors of kinetic and thermodynamic factors which including of interactions between solvents and polymers, interactions between sol-vents and non-solvents, interfacial stability, solvent de-mixing rate [6][7][8][9]. Polymers like polyvinylidene fluoride (PVDF), cellulose acetate (CA), polysulfone (PSf), polyethersulfone (PES) have been used for the making asymmetric membranes due to their good thermal stability, outstanding oxidative and good mechanical strength [10,11].…”