improving uf membrane flux by bubbling and ultrasonic process for raw beet syrup purification

Effective removal of impurities and proper decolorization in the process of raw sugar beet syrup purification is an important step to obtain premium sugar. traditional processes can replace membrane processes with environmentally friendly processes. however, membrane fouling is an important challenge facing this process. one approach to minimize fouling is through the generation of bubbles or cavitation, which helps to alleviate concentration polarization. to achieve this, nitrogen gas was injected at rates of 0.5, 1, and 1.5 l/min in both continuous and interrupted modes, while ultrasound at frequencies of 40 and 70 khz was utilized in continuous and pulsed modes during the ultrafiltration of raw beet syrup. this approach aimed at examining permeate flux, fouling, membrane resistance, and refining characteristics. an increase in nitrogen gas rate from 0.5 to 1.5 l/min during the bubbling process causes enhancement in permeate flux to approximately 0.2 l/m²h in continuous mode, in contrast to the control state, which recorded a flux of 0.135 l/m²h. also, the overall fouling decreased to about 40%. on the other hand, during the pulsed ultrasonic process in combination with the gassing process, membrane fouling decreased by approximately 11.7%. the ultrasonic process in pulsed mode, in conjunction with the gassing process, resulted in achieving a higher and more stable flux of 0.21 l/m²h compared to the 0.16 l/m²h observed with the gassing mode alone after 30 minutes. however, due to the improvement of the diffusion coefficient, a little weakness in the color and turbidity was created by 0.5% and 1.5 iu, respectively in permeate. the total hydrodynamic resistance in the gasification process reached about 8e09 1/m in the control state to about 5.5e091/m at the maximum gasification rate. also, in the combined process of gasification with ultrasonic in pulse mode, the resistance reached from 2.2e09 to 0.8e09 1/m.