Preparation and properties of PTFE hollow fiber membranes for desalination through vacuum membrane distillation

Polytetrafluoroethylene (PTFE) hydrophobic hollow fiber membranes were prepared through a cold pressing method including paste extrusion, stretching and sintering. The effect of stretching ratio on the characteristics of PTFE hollow fiber membranes was investigated. The morphological property of the PTFE hollow fiber membrane was studied in terms of field emission scanning electron microscopy (FESEM). It was observed that the PTFE hollow fiber membranes with four stretching ratios (120%, 160%, 180% and 220%) showed the microstructures of nodes interconnected by fibrils. Increasing stretching ratio was positive for pore size and porosity but negative for water entry pressure and mechanical property. The result of water contact angle measurement showed that the prepared PTFE hollow fiber membrane was a superior hydrophobic membrane material. Finally, the PTFE hollow fiber membranes were tested for their performances in the process of desalination through the vacuum membrane distillation (VMD). An increase in stretching ratio significantly improved the permeation flux. The salt rejections achieved 99.9% for all the PTFE hollow fiber membranes with four stretching ratios in this study, indicating the prepared PTFE hollow fiber membranes exhibited satisfying salt rejection performances.