(487f) Hydrophilic Electrospun Nanofibrous Mat: An Effective Support for High Osmotic Water Flux Thin-Film-Composite Membrane

Hydrophilic
electrospun nanofibrous mat: An effective support for
high osmotic water flux thin-film-composite membrane

Nhu-Ngoc
Bui, Jeffrey R. McCutcheon*

 Department of Chemical, Materials & Biomolecular
Engineering and Center for Environmental Sciences and Engineering; University
of Connecticut; Storrs, Connecticut, USA

Abstract

Electrospun
nanofibers supported polyamide composite membranes have been recently found to
be an effective candidate for the next generation of engineered osmosis (EO) membranes
^[1]. The highly porous nanofibrous supports with interconnected
pores structures play a critical role in minimizing the internal concentration
polarization effect occurring inside the support layer during osmosis
processes. It enables the capability of producing high osmotic water flux using
EO technology. In this study, robust thin film composite membranes supported by
hydrophilic nanofibers electrospun from blends of polyacrylonitrile (PAN) and
cellulose acetate (CA) at different weight ratios were reproducibly fabricated
and investigated. These membranes exhibited two to three times higher osmotic
water flux than the standard commercial forward osmosis membrane made by
Hydration Technology Innovation (HTI). Results shown that the nanofibrous mat
is more hydrophilic when more PAN was blended. The contact angles of PAN and CA
nanofibrous mats were 69.86±15.83^o and 107.43±5.60^o,
respectively. The hydrophilicity of the electrospun nanofibrous supports was
found to correlate well with the flux performance of TFC membranes. The more
hydrophilic PAN-supported TFC membranes performs the highest average osmotic
water flux of 55 L/m²h in pressure-retarded osmosis mode and about
30 L/m²h in forward osmosis mode when using 1.5M NaCl as the draw
solution at 25^oC. The corresponding reverse salt flux ranged from
0.5 to 2 g/m²h. To the best of our knowledge, these membranes
outperformed almost all forward osmosis flat sheet membranes have been reported
in open literature. These results suggest that electrospun nanofibrous
supported polyamide composite membranes may effectively enable applications
like forward osmosis where internal concentration polarization is the
performance-limiting factor.

Figure
1. Cross-sectional
SEM image of polyamide thin-film-composite (TFC) membrane supported on a
polyacrylonitrile (PAN) nanofibrous mat.

Figure
2. Osmotic water
fluxes (a) and reverse salt fluxes (b) of TFC membranes supported on
nanofibrous mats electrospun from blends of cellulose acetate and
polyacrylonitrile at different weight ratios: 80/20, 50/50, 20/80 and pure PAN.
Experimental conditions: 1.5M NaCl draw solution, deionized water feed
solution, measured volumetric flow rate  of the feed and draw solution were 0.5
lpm, temperature of both feed and draw solution was 25.0±0.5 ^oC.

References

[1]
N.N. Bui, M.L. Lind, E.M.V. Hoek, J.R. McCutcheon, Journal of Membrane Science,
385-6, 10-19, (2011).