How to achieve air resistance control in hollow fiber membrane process: Membrane vibration or inner surface modification?

As a factor affecting the efficiency of hollow fiber membrane filtration, air resistance is gradually being discovered. To obtain a better air resistance control strategy, in the study, two representative strategies have been proposed, namely, membrane vibration and inner surface modification, which was achieved by aeration combined with looseness-induced membrane vibration and dopamine (PDA) hydrophilic modification of the inner surface, respectively. The performance of two strategies was based on Fiber Bragg Grating (FBG) sensing technology and ultrasonic phased array (UPA) technology to achieve real-time monitoring. Mathematical model result shows that in hollow fiber membrane modules, the initial appearance of air resistance causes a rapid reduction in filtration efficiency, while this effect diminishes as the air resistance increases. Besides, experimental results show that aeration combined with fiber looseness helps to inhibit air aggregation and accelerate air escape, while inner surface modification enhances the hydrophilicity of inner surface, weakens the air adhesion and increases the drag force of fluid on air bubbles. In the corresponding optimized state, both strategies perform well in optimizing the air resistance control, and the improvement in flux enhancement ability for the two strategies is 26.92 and 34.10%, respectively.