Flux recovery in the ultrafiltration of suspended solutions with ultrasound

The use of a hom sonicator (Misonix, 20 kHz) to recover the flux in the ultrafiltration (UF) of suspended solutions was studied. Two types of solutions. i.e.. the Cu2+-polyethylenimine (PEI) solution and the W/O emulsions dispersed in aqueous solution, were selected, which were widely found in binding-UF and liquid surfactant membrane (LSM) processes, respectively, for removal of toxic heavy metals from effluents. The Amicon YM10 membrane (regenerated cellulose, MWCO 10,000) was used. Experiments were performed as a function of tip position, ultrasonic power, and solution properties such as target ion concentration, percentage of emulsification, and volume ratio of W/O emulsions to the external aqueous phase. It was shown that ultrasound associated with a hydraulic pressure of 10 psi was a promising method for the recovery of UF flux, particularly for the solution with less fouling potential. Careful control of the ultrasonic intensity could keep the membranes durable and prevent the organic compounds (PEI in the Cu2+-PEI Solution; carrier, surfactant, and solvent in the W/O/W Solution) from degradation. Finally, the fouling of membrane during UF of W/O[W solutions was analyzed by the resistance-in-series model. (C) 2004 Elsevier B.V. All rights reserved.