The enhancement of foam generated by low power ultrasound and its application to foam fractionation

Abstract

Foam fractionation is a well established technique for the separation of dissolved surface active species from aqueous solutions. In this work, we report the use of ultrasound to produce finer foam that is more effective for this type of separation. A range of acoustic frequencies from 20 to 4520. kHz were tested, but only 20. kHz proved effective in this regard. Significant decreases in bubble sizes within the bulk solution were recorded at modest acoustic power inputs and this translated into a reduction in foam cell size. The use of higher power inputs was less effective due to gas bubbles collecting at the antinodes of the acoustic field where bubble coalescence was enhanced. Higher powe..