Acoustically driven collection of suspended particles within porous media

A method for collecting fine particles using a porous medium subjected to a standing ultrasonic wave field is described. Proof-of-concept experiments using aqueous suspensions of polystyrene spheres demonstrated the collection of particles up to two orders of magnitude smaller than the size of pores within the porous medium. Two types of porous media were studied; unconsolidated beds formed from glass spheres, and aluminum foam meshes. Removal of particles from the porous media is readily accomplished by deactivating the acoustic field and flushing the particles from the porous medium through continued liquid flow. The effects of processing conditions (suspension flow rate, acoustic power, and feed concentration) on the retention of particles were assessed. Explanations of the mechanism by which the collection occurs are postulated and an assessment of the practicality of the concept for suspension processing is presented.

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