Ultrasonication assisted forward osmosis process: A comparative study on beetroot juice concentration

Internal concentration polarization (ICP) presents significant challenges in the forward osmosis (FO) concentration process, as it leads to a considerable reduction in transmembrane flux crossways the membrane. Mitigating ICP is difficult, as the phenomenon happens within the membrane's porous support layer, and attempts to induce turbulence or alter hydrodynamic conditions are often unsuccessful. In the study, the inclusion of 33 kHz ultrasonication on FO beetroot (Beta vulgaris) juice concentration was investigated. The beetroot juice (5°Brix) was concentrated (∼61°Brix) using forward osmosis (FO) and ultrasonication assisted forward osmosis (USFO). The study process utilizes two different ultrasonication application combination with every 10 min ultrasonication with 5 min off (USFO 10:5) and with every 5 min ultrasonication with 10 min off (USFO 5:10). The results indicate that the applied ultrasonication effectively partially mitigated the ICP effect, enhancing transmembrane flux and reducing concentration time by 2 h. It was also observed that USFO 10:5 was more effective in mitigation of ICP process compared to USFO 5:10. Although transmembrane flux was improved, ultrasonication led to an increased reverse draw salt permeation across the membrane into the feed solution. Additionally, the effect of USFO on the quality parameters of beetroot juice concentrates was measured, and it was found that ultrasonication has affected the nutritional quality parameters, but the color parameters were not much effected.