Bridge between mass transfer behavior and properties of bubbles under two-stage ultrasound-assisted physisorption of polyphenols using macroporous resin

Ultrasound is efficient to enhance various mass transfer processes. This study demonstrates that both ultrasound pretreatment and ultrasonication during adsorption promote the physisorption of polyphenols. The time to reach the adsorption equilibrium was shortened by more than 90 % when the resin diameter deceased from 592 μm to 60.23 μm in the intensive ultrasound pretreatment. The mass transfer mechanism of adsorption under mild sonication differs from that of adoption with intensive ultrasound pretreatment. Mild sonication during adsorption strengthens the influence of surface diffusion of polyphenols on intraparticle diffusion. In contrast, severe disruption of resin particles due to intensive ultrasound pretreatment weakens the surface diffusivity of polyphenols and reduces the contribution of surface diffusion. Also, the physics and sonochemistry of cavitation under sonication environments were explored. Under intensive and mild ultrasound treatments, the calculated bubble numbers were approximately 18789 L-1 and 6312 L-1, respectively. Moreover, a relationship was established between adsorption capacity from mass transfer modeling and bubble properties including the bubble collapse pressure, bubble number, processing time, and processing scale. This bridge between mass transfer behavior and properties of bubbles provides guidance and new insight for the design and scale-up of the ultrasound-assisted adsorption.