Forward Osmosis Process: State-Of-The-Art of Membranes

Forward osmosis (FO) is a membrane-based process that explores the osmotic pressure difference between a feed solution and a draw solution to induce water transport across a semipermeable membrane. Water transport results in the dilution of the draw solution which is reconcentrated using a recovery process. Different from the reverse osmosis process, FO requires lower grade energy and has other advantages, namely, a wide range of applications and a reversible fouling phenomenon of FO membranes. In spite of its many advantages, the FO process is facing drawbacks among which the lack of high-performance membranes. Today, the development of improved FO membranes, capable of achieving a high water flux with a very low reverse salt flux is one of the biggest concerns of membrane scientists. This paper summarizes the basic principle of the FO process, some modern applications, and the main challenges related to membranes. It also describes the progresses in FO membrane development, particularly regarding the membrane manufacturing techniques, commercially available, and R&D membranes.