Ultrasound-Assisted Agglomeration or Aggregation

The removal of fine particles from gases and liquids is a subject of permanent industrial interest. By contrast, only solid-liquid systems are analytically or clinically relevant in this respect. Ultrasound power may help improve the efficiency and performance of analytical separation methods. The specific mechanisms by which separation processes can be ultrasonically enhanced vary with the nature of the medium to be treated. 

In gas suspensions, where very fine particles have to be removed, US action involves agglomeration of particles in order to increase their size and, consequently, to improve the collection efficiency of conventional filters (e.g. electrostatic precipitators, cyclone separators). These filters, while effective for large particle separation, are inefficient for retaining particles smaller than 2.5 pm. Therefore, acoustic agglomeration provides a means for separating fine particles released from industrial, domestic or vehicle sources, which, analytically, constitutes an excellent method for sampling in environmental analysis. 

In solid-liquid separations, particle agglomeration can also be used to prevent filter clogging and increase the separation efficiency in general, however, the procedure is less efficient than with gases. 

The capabilities of ultrasonic radiation forces for manipulating suspended particles have been the subject of a broad spectrum of experimental research. The effectiveness of particle-liquid separation by ultrasonic radiation forces depends on the acoustic distribution in a standing-wave field. In a US standing wave, suspended particles of appropriate 

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