In forward osmosis (FO) process, concentration polarization (CP) serves to reduce the solute concentration difference across the membrane, thereby lowering its flux, which is actually much lower than theoretical values. To reduce CP, the most commonly used way is to reduce the film thickness by increasing turbulent mixing at the membrane surface, including magnetic stirring (lab-scale) and increasing the fluid flow velocity past the membrane surface (industry-scale), etc. However, the water flux difference between the expected and the experimental is still very big.In this research, membrane vibration was examined as a new way to control the phenomena of concentration polarization (CP) in 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 are 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.

Control of concentration polarization in forward osmosis processes by membrane vibration

246th National Meeting (2013)

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