Modification of PVDF hollow fiber membrane with ZnO structure via hydrothermal for enhanced antifouling property in membrane distillation

This study aims to provide a close insight into the possibilities and constraints associated with the development of ZnO structures on polyvinylidene fluoride (PVDF) hollow fiber membranes using the hydrothermal method to enhance membrane surface roughness for improved fouling resistance in membrane distillation (MD). Due to the flexible nature of polymeric hollow fiber membranes, there is a considerable risk of the ZnO structure detaching from the membrane surface when the membrane is bent. To address this issue, the hydrothermal duration was varied between 4–16 hours to optimize the ZnO structure for high integrity, followed by fluorination. The results reveal that the membrane treated with hydrothermal for 8 hours exhibits stable coating integrity, imparting the membrane with the highest contact angles with various liquids. This membrane demonstrates a flux of 4.0 kg/m2h and excellent salt rejection (>99.9 %) in direct contact MD (DCMD) when treating a 35 g/L saline solution. Additionally, the membrane exhibits outstanding antifouling performance with minimal flux reduction over 24 hours when treating a saline solution containing humic acid. However, the upscaling of the hydrothermal approach may pose challenges due to the difficulty in maintaining the consistency of ZnO structure formation.