Enhanced wetting and fouling resistance of ZIF-8/PVA@PTFE Janus membrane in air-bubbling-assisted membrane distillation

Hydrophobic membranes, such as polytetrafluoroethylene (PTFE), are prone to pore wetting during membrane distillation when treating wastewater containing amphiphilic contaminants. In this study, a Janus membrane composed of zeolitic imidazolate framework-8 (ZIF-8) and polyvinyl alcohol (PVA) was fabricated via vacuum filtration and employed in air-bubbling-assisted direct contact membrane distillation (DCMD). The optimal membrane, with a 0.815 mg/cm 2 ZIF-8 loading, achieved a desalination rate of 99 %, a stable vapor flux of 20.53 L/(m 2 ·h), and a permeate conductivity of less than 1.44 μS/cm during 25 h of operation. However, the increasing concentration of SDS in the feed solution over time led to an increase in conductivity, which pointed to a reduction in the membrane's anti-wetting performance, suggesting the limitations of ZIF-8 alone in mitigating wetting. To overcome this, continuous air bubbling was introduced, which significantly enhanced wetting resistance and extended the membrane's operational lifespan to 48 h. Higher airflow rates (5.93 L/min) yielded optimal performance. Furthermore, a Random Forest machine learning model was employed to predict permeate flux and conductivity based on key operational parameters, achieving a coefficient of determination (R 2 ) greater than 0.73. Collectively, this study demonstrates the synergistic potential of the ZIF-8/PVA@PTFE Janus membrane combined with air-bubbling assistance to effectively suppress wetting and enhance the efficiency and durability of membrane distillation for challenging wastewater.