PEBAX®-based Composite Hollow Fibre Membranes For Gas Separation

The preparation of PEBAX®-based composite hollow fibre membranes according to different coating methods was investigated. PEBAX®-based composite membranes on PAN porous hollow fibre support were prepared according to the following methods: outer surface dip coating, direct spinning and inner surface coating by cross flow filtration. The outer surface dip coating [1] was carried out by immerging end-sealed PAN porous hollow fibres into a PEBAX® solution for fixed time at room conditions. Direct spinning coating was carried out according to the dry-wet spinning method [2,3] using a triple nozzle device fed contemporary by two different polymer solutions (PEBAX® and PAN) and an inner coagulant fluid. The PEBAX® inner coating was realised by cross-flow filtration of a dilute PEBAX® solution through PAN porous hollow fibre membranes under controlled conditions. Scanning electron microscopy analyses allowed to evaluate the morphology and the thickness (fig. 1) of the composite membranes which strongly depend on the selected coating method. Fig.1: Cross section of the PEBAX®-PAN composite membrane. Single gas permeation tests were carried out to assess the transport properties of the prepared composite membranes in comparison with those of a dense PEBAX® flat sheet membrane used as a reference. An ideal selectivity ?CO2/N2 = 60 was measured for this dense flat membrane. Preliminary experiments showed better results with the dip coating approach than ones obtained by direct spinning. Intermediate results were obtained with the cross flow filtration method. Low gas permeance values (ca. 0.04 m³/m² h bar for CO2), suggest that a PEBAX® thin layer could be present on the whole surface of PAN porous support, but with few pinhole defects which reduce the selectivity of such composite membranes. Further investigations on the operating conditions might lead to the reduction of such defects allowing viable and easy going methods for the preparation of composite hollow fibre membranes. Acknowledgements The work leading to these results has also received funding from the European Community's Framework Programmes (FP7/2007-2013) under grant agreement no. NMP3-SL-2009-228631, project DoubleNanoMem. Dr. C. Cantoni (Arkema Italy) is gratefully acknowledged for providing the Pebax® samples. References [1] F. Bazzarelli, P. Bernardo , F. Tasselli, G. Clarizia, V.G. Dzyubenko, P. Vdovin, J.C. Jansen, Sep. & Purif. Tech. 80 (2011) 635-642. [2] F.Tasselli, J.C. Jansen, E. Drioli, J. Appl. Polym. Sci., 91(2) (2004) 841-853. [3] F.Tasselli, J.C. Jansen, E. Drioli, J. Membr. Sci., 255(1-2) (2005) 13-22.