(419ak) Polydopamine Modified PVDF Nanofibers Supported Thin Film Composite Membranes for Osmotically Driven Membrane Processes

Polydopamine modified PVDF nanofibers
supported thin film composite membranes for osmotically
driven membrane processes

Malgorzata Chwatko, Jason T.
Arena, Liwei Huang, Jeffrey R. McCutcheon

One key area of
research in the development of osmotically driven
membrane processes (ODMPs) is the development of new membranes. Though viable
commercial membranes have been featured in industrial processes [1], few
membranes such as the cellulose triacetate and thin film composite forward
osmosis (FO) membranes manufactured by Hydration Technology Innovations are
available for study. All of the membranes used industrially are built from
wet-dry cast cellulose acetate or thin film composite structures. 

Thin film
composite (TFC) membranes, comprising the newest generation of membranes for
ODMPs, are composed of a three-tiered structure, with a very thin selective
layer on top of a support layer and lastly backing layer. This design offers
high flexibility of optimizing the selective and support independently. A new
membrane platform which has gained interest in recent years expands upon the
classical thin film composite structure, but replaces the normal phase-inverted
polymer support with one prepared via the electrospinning
technique. Electrospun supports characteristically
have a highly porous and interconnected pore structure. Some of the most recent
work on nanofiber support membranes was done by Huang
and McCutcheon using hydrophilic Nylon 6,6 nanofiber support and identified a unique swelling behavior
which hindered performance [2]. Hydrophobic materials have reduced interaction
with water and as a result have a tendency for less swelling. One such polymer
recently reported on by Tian, et al. used a polyvinylidene fluoride (PVDF) support in their preparation
new membrane for FO [3].

The membrane
prepared in this work expands on this approach by also using electrospun PVDF nanofibers as a
support of an interfacial polymerized TFC membrane. Here seeking to address a
limitation of hydrophobic supports identified in work by McCutcheon, et al. that
observed the importance of support layer hydrophobicity and the resulting lack
of support layer wetting which dramatically impairs water flux due to severe
internal concentration polarization [4].
Work later done by Arena, et al. hydrophilized
the hydrophobic supports by applying polydopamine (PDA) to the surface of
commercial TFC membranes. Modified membranes illustrated significant
improvements in water flux following PDA modification [5, 6].  The work presented here will detail the
preparation and performance of the PVDF supported TFC membrane, which have had
a hydrophilic character imparted to them through the addition of PDA to the
surfaces of the PVDF support layer combining the mass transport advantages of a
nanofiber support, the low swelling propensity of a
hydrophobic support and thanks to the PDA modification a hydrophilic character
essential for good performance in osmotically driven
membrane processes.

Figure 1: Scanning
electron micrograph a cross-section of the PVDF membrane support

Works Cited:

[1] McGinnis RL, Hancock NT,
Nowosielski-Slepowron MS, McGurgan
GD. Pilot demonstration of the NH₃/CO₂ forward osmosis
desalination process on high salinity brines. Desalination (2013) 312:
pp. 67-74

[2] Huang L, McCutcheon JR.
Hydrophilic nylon 6,6 nanofibers
supported thin film composite membranes for engineered osmosis. Journal of
Membrane Science (2014) 457: pp. 162-169

[3] Tian
M, Qiu C, Liao Y, Chou S, Wang R. Preparation of
polyamide thin film composite forward osmosis membranes using electrospun polyvinylidene
fluoride (PVDF) nanofibers as substrates. Separation
and Purification Technology (2013) 118: pp. 727-736

[4] McCutcheon JR & Elimelech M. Influence of membrane support layer
hydrophobicity on water flux in osmotically driven
membrane processes. Journal of Membrane Science (2008) 318: pp.
458-466

[5] Arena JT, McCloskey BD,
Freeman BD & McCutcheon JR. Surface modification of thin film composite
membrane support layers with polydopamine: enabling use of reverse osmosis
membranes in pressure retarded osmosis. Journal of Membrane Science
(2011) 375: pp. 55-62.

[6] Arena JT, Manickam SS, Reimund KK, Freeman BD & McCutcheon JR. Solute and water transport in
forward osmosis using polydopamine modified thin film composite membranes. Desalination
(2014) 343: pp. 8-16.