Engineering the polyamide selective layer of thin film composite membranes for osmotic power generation

University of Technology Sydney. Faculty of Engineering and Information Technology.Population increase and economic growth have played huge parts in the continuously increasing global energy consumption, which has led to the fossil fuel reserves decline and greenhouse gas emissions. Thus, there is a significant increase in interest in alternative renewable energy sources, among which is osmotic power or salinity gradient energy. Osmotic power is harnessed upon the mixing of water streams with different solute concentrations and osmotic pressures (typically, freshwater and saltwater). Pressure retarded osmosis (PRO) is a process which exploits the osmotic pressure difference between the water streams and allows water to pass through a selectively permeable membrane from the less concentrated stream to the pressurised more concentrated stream. While PRO presents itself as an environmentally benign energy-harnessing process, its wide-scale implementation and technological development are hindered by challenges, among which is the available of suitable and high-performance membranes. Thin film composite (TFC) membranes are conventionally utilised for PRO, due to their porous membrane substrate and dense thin film selective layer, which, together, can exhibit outstanding separation performance and withstand the application of hydraulic pressure during PRO operation. In this thesis, TFC membrane development for PRO was conducted by engineering specifically the polyamide thin film selective layer. Several techniques were conducted in this thesis, which include: (1) nanomaterial filler incorporation; (2) surface functionalisation via nanomaterial incorporation; (3) chemical treatment; and (4) substrate-and-selective-layer interface modification