  Wetting of the membrane to displace air or conditioning liquids is important
to exploit the complex porosity of a filtration membrane. This study reveals
the details of wetting in multibore membrane-based filtration modules. Using
magnetic resonance imaging (MRI), we quantify the fluid distribution patterns
during initial membrane wetting in dead-end permeation mode. The
spatio-temporal evolution of aqueous copper sulfate solution wetting the
membrane fibers was investigated as a function of the applied flux, packing
density, and position along the membrane module length. Three initial wetting
conditions were examined: delivery-state membranes, ethanol-washed and dried
(air-filled) membranes, and ethanol-filled membranes. Significant changes in
wetting patterns were observed due to interfacial and polymer swelling effects.
This in-situ investigation reveals a slow wetting progression over six hours
and more to obtain complete wetting, even at high fluxes of 200 LMH. However,
an increased flux leads to faster wetting kinetics as the evolving wetting
patterns are flux dependent. The packing density of the multibore fibers
additionally impacts the wetting kinetics by shifting the prevalent pressure
conditions. Although in dead-end mode, the wetting progression is non-uniform
along the membrane module length. In addition to this parameter study,
different pre-wetting agents' effect on the displacement behavior was
investigated in depth. This study helps to understand (a) complex wetting
phenomena inside multibore membranes in dead-end filtration, (b) the membranes'
interaction with their surroundings due to neighboring membranes, and (c) the
effect of the used fluid system for displacement on the resulting wetting
patterns.
