Positron Annihilation Spectroscopic Evidence to Demonstrate the Flux-Enhancement Mechanism in Morphology-Controlled Thin-Film-Composite (TFC) Membrane

Citations Over TimeTop 10% of 2005 papers

Abstract

In this study, positron annihilation lifetime spectroscopy (PALS) is applied to explain the flux-enhancement mechanism in thin-film-composite (TFC) membranes prepared by using dimethyl sulfoxide (DMSO) as an additive in the interfacial polymerization. The TFC membranes show a large increase in water flux, up to 5-fold, compared to nonadditive membrane. Atomic force microscopy (AFM) shows that surface roughness and surface area increase when DMSO in the aqueous phase solution phase works to increase miscibility of the aqueous and the organic phase by reducing the solubility difference of two immiscible solutions. X-ray photoelectron spectroscopy (XPS) reveals the variation of the chemical compositions to the extent that there is a considerable increase in the cross-linked amide linkages of the flux-enhanced TFC membranes. The effects of these structural changes on the molecular-size free volume properties are evaluated by PALS studies. The PALS results are the first to experimentally show that the thin films of cross-linked aromatic polyamide RO membranes are composed of two types of pores having radii of about 2.1-2.4 A from tau3, network pore, and 3.5-4.5 A from tau4, aggregate pore. The increase in the size and number of network pores by means of DMSO addition during interfacial polymerization enhances the water flux notably. The size of aggregate pores also increases and may contribute to enhance water flux, although their number inevitably decreases as the number of network pores becomes increased. Details on the correlations between RO performances and o-Ps lifetime parameters are clearly described based on the pore-flow model of reverse osmosis developed by Sourirajan et al.

Related Papers

• → Tailoring the Structure of Thin Film Nanocomposite Membranes to Achieve Seawater RO Membrane Performance(2010)215 cited
• → Influence of l-arginine on performances of polyamide thin-film composite reverse osmosis membranes(2019)27 cited
• → Corolliform morphology thin film composite polyamide membrane constructed via Tröger's base PIM for enhancing nanofiltration separation performances(2022)15 cited
• → Polyamide Chain Growth and Crosslinking: The Controlling Determinants for Properties of Thin Film Composite Membrane(2019)2 cited
• → Preparation of thin-film composite polyamide reverse osmosis membranes(2006)1 cited