Investigating the potential of bubbling and ultrasonic processes in reducing the fouling of the ultrafiltration membrane during the purification of raw sugar beet syrup 

Abstract

Effective removal of impurities and appropriate decolorization in raw or thin beet juice are considered as important processes to obtain premium sugar industrially. Environmentally friendly processes, such as membrane processes, have the potential to replace some old processes in the sugar industry completely or partially. However, membrane fouling and flux reduction are important challenges facing this process. One of the methods to reduce fouling and improve the flux is bubble generation or cavitation in the inlet flow to create a turbulent flow and as a result reduce the concentration polarization. In this research, the injection of nitrogen gas along with ultrasound was used in the raw beet syrup inlet stream during its purification by ultrafiltration to investigate the efficiency of the membrane such as the improvement of the permeate flux, fouling, membrane resistance and the refining properties of the filtrated syrup. During the bubbling, by increasing the amount of nitrogen gas from 0.5 to 1.5 Lit/min, the permeate flux improved and the overall membrane fouling decreased. This reduction was more evident in the continuous gasification than in the interrupted method. Also, the results showed that the continuous gasification caused a slight disturbance in the purification properties such as purity, color and turbidity due to the improvement of the permeate flux. Furthermore, the results showed that the application of the ultrasonic process in the pulse form simultaneously with the gassing process could put the flux in a higher and more stable state than the gassing state alone during the ultrafiltration process.