The Impact of Polysulfone Solution Concentration on the Morphology of the Support Layer in Thin-Film Composite Membranes

Document Type : Research Paper

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Department of Polyurethane and Advanced Materials, Faculty of Polymer Science, Iran Polymer and Petrochemical Institute, P.O. Box: 14975-112, Tehran, Iran

Abstract

Hypothesis: Among different membrane processes, reverse osmosis is widely used in desalination, water treatment, and the preparation of ultra-pure water. Reverse osmosis membranes usually consist of three layers: a non-woven polyester, a porous polysulfone as a support layer, and a thin polyamide layer. The support layer of thin film composite membrane is an interface where interfacial polymerization occurs, therefore, the surface thickness and the porosity of the support layer have a significant effect on the formation of an integral and defect-free polyamide layer. Tiny pore size can lead to the formation of a defective polyamide layer, because of inadequate m-phenylenediamine monomers impregnated within the pores. On the other hand, the pore size cannot be very large, because when the polyamide layer goes down deeply into the pores, it could lead to an unstable and non-uniform selective layer that will eventually affect the performance of the thin film composite membrane
Methods: First, polysulfone was synthesized from bis(4-chlorophenylsulfone) aromatic nucleophilic substitution condensation polymerization reaction with bisphenol A. To prepare a flat porous membrane, phase inversion method was used and synthetic polysulfone was dissolved in dimethylacetamide solvent with different concentrations. The relationship between the concentration of polysulfone solution and the morphology of the porous layer was investigated. The interfacial polymerization of m-phenylenediamine and trimesoyl chloride was performed to form the polyamide layer on the polysulfone support layer
Findings: The structure of polysulfone was confirmed by FTIR and 1H-NMR spectroscopy. The molecular weight of PSF was determined. The morphology of the porous membrane prepared from polysulfone solution with different concentrations was examined by SEM, and finally, the performance of the thin film composite membrane, including water flux and salt rejection was measured

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