Abstract

The increasing research in the field of polymeric multi-channel membranes has shown that their mechanical stability is beneficial for a wide range of applications. The more complex interplay of formation process parameters compared to a single-channel geometry makes an investigation using Design of Experiments (DoE) appealing. In this study, seven-channel capillary membranes were fabricated in a steam–dry–wet spinning process, while varying the composition of the polymer solution and the process temperatures in a three-level fractional factorial linear screening design. The polymers polyvinylidene flouride (PVDF) was the chemically resistant main polymer and polyvinylpyrrolidone (PVP) was added as hydrophilic co-polymer. Scanning electron microscopy and atomic force microscopy were applied to study the membrane morphology. Fabrication process conditions were established to yield PVDF/PVP multi-channel membranes, which reached from high flux (permeability P = ///bar, dextran 500 retention R = 18.3%) to high retention (P = ///bar, R = 80.0%). The concentration of the main polymer PVDF and the molecular weight of the co-polymer PVP showed linear relations with both P and R. The permeability could be increased using sodium hypochlorite post-treatment, although retention was slightly compromised. The obtained membranes may be suitable for micro- or ultra-filtration and, at the same time, demonstrate the merits and limitations of DoE for multi-channel membrane screening.

Highlights

  • Membrane technology has received increasing attention over the past decades due to its many advantages in various industrial processes

  • Multi-channel membranes may provide enhanced productivity per volume and better mechanical stability compared to flat-sheet and single-channel arrangements if designed properly

  • Particular interest lies in the fabrication of polyvinylidene flouride (PVDF) multi-channel membranes, as they provide enhanced chemical stability compared to, for instance, PES

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Summary

Introduction

Membrane technology has received increasing attention over the past decades due to its many advantages in various industrial processes. Membrane technology is a key element in the fields of water treatment, food and pharmaceutical processing, and gas purification [1]. The main market share is held by polymeric membranes due to their versatility and inexpensive production [2], whilst the polymer polyvinylidene flouride (PVDF) is one of the most promising materials due to its robust mechanical strength, favorable thermal stability, and—most importantly—excellent chemical resistance [3,4,5]. In an attempt to create a sufficiently large filtration area, membrane modules have been developed, which feature either a tubular or flat sheet membrane arrangement. In particular capillaries or hollow fibers, offer several merits over the flat sheet configuration, such as higher

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