Membrane and Desalination Technologies - TCE Moodle Website

CONTENTS
INTRODUCTION
MEMBRANE CLASSIFICATION
MEMBRANE MATERIALS
PHASE INVERSION MEMBRANES
2
Preparation of Polymeric Membranes
Jizhong Ren and Rong Wang
PREPARATION OF ASYMMETRIC MEMBRANES BY PHASE INVERSION TECHNIQUE
ACRONYMS
NOMENCLATURE
REFERENCES
Abstract This chapter mainly describes the principles of membrane formation process for
polymeric membranes. With a brief introduction of relevant background information such as
various membranes and membrane processes, a comprehensive list of polymer materials,
which are suitable for making membranes, has been given. The most common technique used
to prepare polymeric membranes – phase inversion process, including thermally induced
phase separation (TIPS) and diffusion induced phase separation (DIPS), is discussed in detail.
The thermodynamic behavior of the casting polymer solution, the process of membrane
formation, and the fabrication of hollow fiber and flat sheet membranes are involved.
The thermodynamic description of the polymer solution is based on the concepts of
spinodal, binodal, vitrification boundary, gelation boundary et al. in the phase diagram. The
linearized cloud point curve correlation is presented. In addition, two important parameters, the
approaching ratio of the polymer solution and the approaching coagulant ratio, are discussed in
association with membrane formation. For the membrane formation process, the delay time
and gelation time are two macroscopic time scales, which influence the membrane morphologies
simultaneously. The formation of nascent porous membranes, the vitrification of the
membrane morphology and the membrane surface formation are described. The macrovoid
formation is related to the viscous fingering phenomenon. In the fabrication of hollow fiber
membranes, the shear flow of the polymer solution inside the spinneret and the elongation flow
in the air gap strongly influence the performance of resultant membranes. Thus, the shear flow
and elongation flow are discussed in great detail. The hydrodynamics of the polymer solution
at the casting window in the process of preparing flat sheet membranes is also concerned.
From: Handbook of Environmental Engineering, Volume 13: Membrane and Desalination Technologies
Edited by: L.K. Wang et al., DOI: 10.1007/978-1-59745-278-6_2 # Springer ScienceþBusiness Media, LLC 2011
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