Ultrasonic Monitoring of Oil-in-Water Emulsions Undergoing Depletion Flocculation

The paper describes a three-part experiment on flocculating emulsions in order to determine whether ultrasonic spectroscopy could be used to detect and characterize the flocculation process. Three emulsions which represented unflocculated, partially flocculated, and fully flocculated systems were prepared. They were characterized independently using direct microscopic examination and their creaming behavior. Ultrasonic spectroscopic measurements of the flocculating emulsions showed large changes during the flocculation process, which were not readily modeled using single particle scattering theory. The ultrasonic properties of the unflocculated emulsion did not change during the measurement period. The results demonstrate that ultrasonic techniques are capable of detecting the flocculation process. There is clear potential to use ultrasonic techniques to characterize flocculated structures, but more work is needed on the theoretical analysis of the interaction of ultrasound with particle aggregates.