Low-frequency ultrasound to improve dead-end ultrafiltration performance

Low-frequency ultrasound (20 kHz) has been used to facilitate dead-end ultrafiltration of polymer solutions. The influence of ultrasonic irradiation on permeate fluxes and retention ratios was investigated and compared with conventional stirred and unstirred operations. In addition, the effect of the ultrasonic field on the membrane permeability and on the polymer solution was examined. The efficiency of ultrasound in enhancing ultrafiltration performance was demonstrated. This improvement is due to a decrease of the boundary layer resistance against permeation flow, which may be attributed to disturbance induced within the cell and at the membrane surface by physical effects associated with ultrasonic waves propagation.