Abstract
Pressure-retarded osmosis (PRO) can convert difference in salinity between two streams into energy as it allows water transport through a semipermeable membrane against the application of hydraulic pressure. So it gained attention due to its use as a salinity-gradient energy-generating membrane process. However, development of high-performance PRO membranes has received increased concerns yet still under controversy in practical applications. Indeed, despite several improvements on PRO over the past decades, there still exist several technical issues pertinent to its adequate implementation that remains unresolved such as membrane material, fouling, process efficiency, techno-economic viability. Different process parameters such as type of draw solution, feed concentration, and membrane type directly affect the efficiency and power density of PRO. Since potential side benefits of PRO include electricity production and the treatment of rejected brine from desalination, the process presents a unique path to utilize all these advantages. The amount of useful energy from PRO would probably be enormous if this was exploited globally. There are several questions that remain unanswered about the overall feasibility of PRO as a stand-alone process. This chapter offers a comprehensive background and overview of the developments of PRO membranes to enhance their power density and feasibility.