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

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 power levels were effective at reducing the size of nascent bubbles produced by the sparger, but this did not translate into a reduction in foam cell size. The relative position of the sparger with respect to the transducer was also found to be important. The application of 20 kHz ultrasound was shown to enhance the removal of surfactants and a bioactive agent between 125 and 320%.

The enhancement of foam generated by low power ultrasound and its application to foam fractionation.Figure optionsDownload as PowerPoint slideResearch highlights
► Ultrasound-assisted foam fractionation is used for the separation of bioactives.
► Frequencies from 20 to 4520 kHz were tested, but only 20 kHz proved effective.
► 20 kHz ultrasound has enhanced the separation efficiency between 125 and 320%.
► Low power level was effective indicating that it is an economically viable process.