Control of Concentration Polarization in Forward Osmosis Processes by Membrane Vibration

In this research, membrane vibration was examined as a new way to control the phenomena of concentration polarization (CP) in forward osmosis (FO) processes. A batch reactor was developed for dynamic studies on FO's flux behavior. The performance of "fresh water" production and reverse diffusion in the FO process were evaluated by vibrating the FO membrane under different experimental conditions. Results indicate that, with a NaCl solution (concentration = 1.0M) as the draw solution, the flux was 20-50 L/m2-h for the membrane vibration, which is much higher than that generated by the magnetic stirring method (1-6 L/m2-h). The energy consumption of the method was relatively high, but was lower than that of a RO process. It is concluded that membrane vibration could increase the flux of fresh water production and thus may be used to control the CP better than the methods being used currently.