Forward Osmosis Essay

The forward osmosis (FO) process is an emerging separation/desalination process. It is rapid process compared to other membrane processes such as reverse osmosis. The physical phenomenon of forward osmosis (FO) can demonstrated as the motion of water molecules through a semi-permeable membrane due to difference in osmotic pressure driving force through the membrane. The membrane enables only water molecules to pass through when salt molecules are rejected. The forward desalination technique makes use of a draw solution with high osmotic pressure to draw the water molecules from a inlet solution such as brackish with lower osmotic pressure in contrast to the draw solution. As illustrated in Figure 1, water flux directions in forward osmosis and reverse osmosis. In forward osmosis, the inlet solution of high water chemical potential is separated from the draw solution of low water chemical potential by a semipermeable membrane (as shown in figure 1 (a)). Figure 1 (b) shows water molecules are transported from the inlet to the draw solution in FO because of the difference in osmotic pressures. However, in reverse osmosis (figure 1 (c)), hydraulic pressure is applied to the inlet to overcome the osmotic pressure. The application of …show more content…
Water flux in (a) and (b) for forward osmosis. Water flux in (c) and (d) for reverse osmosis There are many advantages for FO over RO processes. In FO, it requires less energy and fouling is more capable of reversing [25,26__,27],. On the other hand, RO requires high energy consumption and there are fouling is less capable of reversing. Also, there are some advantages for RO over FO. In RO, permeate water = high quality product than FO. Also, FO requires second separation step.
Currently, the crucial challenges of FO processes are (i) inefficient membranes that are heart of most FO-based processes; (ii) lack of cost effective draw solutes that can be simply recycled; and (iii) little researches focusing on