(703f) Thin-Film Composite Membranes for Osmotic Power Generation

Pressure
retarded osmosis (PRO) is a membrane-based technology that harvests the energy
of mixing two solutions from different salinity and converts it to electricity
with the aid of a semi-permeable PRO membrane and a hydro-turbine. In addition
to utilize seawater and river water as the feed pair, the PRO process can use
highly concentrated RO retentate and recycled municipal wastewater as the feed
pair for power generation. By doing so, not only can the environmental issue
such as the disposal of RO retentate be solved, but also produce much higher
osmotic energy. Therefore, the development of PRO membranes for osmotic power
generation will have repercussion effects on the production of both clean
energy and clean water.

As the heart of
PRO processes, more studies on PRO membranes are expected to further accelerate
the process in the near future. The thin-film composite (TFC) membranes, a
commonly used PRO membrane nowadays, consist of a TFC layer of cross-linked
polymers which acts as the primary barrier to salt and is responsible for
giving a reasonable selectivity. In PRO processes, the draw solutions are
pressurized by high hydraulic pressures to later push the hydroturbine and
convert osmotic power into electrical power. However, under high pressures, membranes
inevitably lose selectivity because of deformation and damage of both TFC layer
and supporting layer. In our work, a systematical investigation has been
demostrated on the evolution of morphological deformation and membrane
performance in terms of compacted structure, water flux, reverse salt flux, and
power density as a function of hydraulic pressure for membranes used in
high-pressure PRO processes. In addition, an insight to PRO membranes will be
given on the effects of membrane modifications and post-treatments.

Acknowledgments

This research was funded under the project entitled
?Membrane development for osmotic power generation, Part 1. Materials
development and membrane fabrication? (1102-IRIS-11-01) and NUS grant number of
R-279-000-381-279. This research grant is supported by the Singapore National
Research Foundation under its Environmental & Water Technologies
Strategic Research Programme and administered by the Environment
& Water Industry Programme Office (EWI) of the PUB. Special thanks are due
to Dr. Panu Sukitpaneenit, Dr. Sui Zhang, and Miss Xiuzhu Fu for their valuable
suggestions and kind help.