Insight into mass transfer during ultrasound-enhanced adsorption/desorption of blueberry anthocyanins on macroporous resins by numerical simulation considering ultrasonic influence on resin properties

Abstract

The mass transfer mechanism about ultrasonic enhancement of blueberry anthocyanin adsorption and desorption on macroporous resins were investigated. Ultrasound treatment led to the decrease of resin size, whereas average pore diameter, specific surface area, total pore volume were less affected. Then, the pore volume and surface diffusion model considering ultrasound-induced changes of particle size and surface area was employed to model anthocyanin adsorption process numerically. Generally, sonication enhanced external mass transfer coefficient (kL) and surface diffusion coefficient (Ds) during adsorption. The values of kL and Ds under sonication at 279 W/L and 20 °C were 7.578 × 10−2 cm/s and 2.000 × 10−9 cm2/s, which were 2.0% and 140.1% higher than the kL and Ds values under orbital agitation at 20 °C. Accordingly, anthocyanins penetrated into the interior of macroporous resins faster under sonication. The overall intraparticle diffusion for anthocyanin adsorption was dominated by pore volume diffusion with the contribution percentage higher than 50%. Sonication enhanced the contribution of surface diffusion to the overall diffusion, which was consistent with the increase of Ds with ultrasound energy. Moreover, a general diffusion model also incorporating the variations of particle size and surface area was utilized to model anthocyanin desorption process. The overall anthocyanin diffusivity increased with both ultrasound energy level and temperature. Anthocyanins distributed more homogenously inside resins under sonication at 279 W/L than under other treatments. This work could be a reference for the valorization of anthocyanins in food industry, especially juice and wine industries.