  Osmotic energy (or salinity-gradient energy) is the energy released when
water with different salinities is mixed, such as rivers and oceans. By
employing a semipermeable membrane to control the mixing process, the osmotic
pressure gradient energy can be generated in terms of electrical power via
pressure retarded osmosis (PRO) without causing adverse environmental impacts.
This work presents the fabrication of thin film nanocomposite (TFN) membranes
which are customized to offer high flux in forward osmosis (FO) and high
osmotic power in PRO. In this study, the TFN membrane was fabricated by forming
a polyamide thin film on the polysulfone substrate through the interfacial
polymerization process. One of the challenges in this process is the fouling of
PRO membranes. Fouling is one of the major characteristics that results in the
decline in the water flux of the membrane. The hydraulic pressure during PRO
processes is less than RO processes so membranes that are used for PRO are less
likely to foul. Experiments show that TFN membranes are more tolerant of
fouling than TFC membranes because of the nanomaterials which has higher
surface hydrophilicity. The structure of the membrane is a very significant
characteristic that has an influence on fouling. Especially, the structure of
porosity that is coherent to the thickness.
