疏水膜的污染、润湿与干燥探讨

Discussions on pollution,wetting and drying of hydrophobic membranes

明确了疏水膜概念,分析了有机-无机复杂体系的疏水膜污染机理,通过在料液中鼓入压缩空气,可以降低料液在膜表面的浓差极化和温差极化,提高膜通量,缓解膜污染.膜润湿是气-固界面被液-固界面逐渐取代的过程,分析了疏水膜润湿机理,处理料液中的表面活性物质是疏水膜分离过程中膜润湿过程的“加速器”.采用气-液界面萃取法作为疏水膜分离过程中料液的预处理过程,可有效延缓疏水膜的亲水化渗漏进程.针对疏水膜材料润湿后的干燥问题,提出了疏水膜材料的临界润湿深度概念,在膜孔润湿深度小于临界润湿深度时对疏水膜进行常规清洗,再用纯水清洗,此时膜孔中的水会在水的界面收缩力的作用下,被自动从疏水膜孔中排出,实现疏水膜的自脱水干燥,通过这种膜分离-清洗的工艺循环,可以实现疏水膜分离进程的持续进行.

In this paper,the concept of hydrophobic membrane has been clarified,the fouling mechanism of hydrophobic membrane in organic-inorganic complex system was analyzed.By pumping compressed air into the feed,the concentration polarization and temperature polarization of the feed solution on the membrane surface can be reduced,the flux of the membrane can be increased and the membrane fouling can be alleviated.The membrane wetting is a process in which the gas-solid interface is gradually replaced by the liquid-solid interface,the wetting mechanism of hydrophobic membrane was analyzed,The surface active substances in the feed are“accelerators”in the process of membrane wetting during the separation of hydrophobic membranes.The method of gas-liquid interface extraction is used as the pretreatment process of feed liquid in the hydrophobic membrane separation process,which can effectively delay the hydrophilic leakage process of hydrophobic membrane.Aiming at the drying problem of hydrophobic membrane after wetting,the concept of critical wetting depth of hydrophobic membrane was proposed.When the wetting depth of the pore channel is less than the critical wetting depth,the hydrophobic membrane is cleaned routinely and then cleaned with pure water.At this time,the water in the pore channel will be automatically discharged from the pore channel of the hydrophobic membrane under the action of the contraction force of the water interface,thus realizing the self-dehydration and drying of the hydrophobic membrane.Through this process cycle of membrane separation and cleaning,the continuous process of hydrophobic membrane separation can be achieved.