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Interfacially Polymerized Thin Film Composite Membranes Based on Microporous Polypropylene Hollow Fibers

Praveen B. Kosaraju, Alexander P. Korikov, and Kamalesh K. Sirkar. Chemical Engineering, New Jersey Institute of Technology, Membrane Separations, 161 Warren St., Newark, NJ 07102

Interfacial polymerization (IP) is a powerful technique to fabricate thin film composite (TFC) membranes having a selective layer of about 20nm or higher. The polymers used most often as support are polysulfone (PS) or polyethersulfone (PES). However, these supports are not stable for non-aqueous media applications. In this work, microporous polypropylene (PP) hollow fiber membranes are used as a support to fabricate TFC membranes for ultrafiltration and nanofiltration by the technique of IP. Porous polypropylene membranes can provide substantial chemical, pH, and solvent resistance and are therefore suitable as supports for fabricating TFC membranes functioning as solvent-stable NF/UF membranes. The surface at the internal diameter of polypropylene hollow fiber membranes was hydrophilized first. A standard procedure to coat the hydrophilized hollow fiber membranes was developed next. Among a number of factors which hold the key to a successful coating/membrane are hydrophilization of the different surfaces of the porous hydrophobic support via an appropriate procedure, order of introduction of the monomer-containing solutions, exposure of the nascent film to controlled shear conditions, and heat treatment of the IP layer formed. Monomer reactants for the interfacial polymerization reaction were diacyl chlorides such as sebacoyl chloride or iso-phthaloyl dichloride and diamines such as hexanediamine or polyethyleneimine (PEI). The membranes fabricated were characterized by scanning electron microscopy (SEM), ultrafiltration and nanofiltartion of different solutes in alcoholic solutions. These TFC membranes were observed to have substantial solvent stability.