Non-solvent Flux Augmentation of an LDPE-Coated Polytetrafluoroethylene Hollow Fiber Membrane for Direct Contact Membrane Distillation.

Abstract

Membrane distillation (MD) is a thermal technology for the desalination process that requires a hydrophobic microporous membrane to ensure that the membrane can maintain the liquid–vapor interface. This work aims to enhance the water permeation flux of the previously coated membrane by modifying the surface of the polytetrafluoroethylene hollow fiber (PTFE HF) membrane with a selected non-solvent such as acetone, cyclohexanone, and ethanol in low-density polyethylene as a polymeric coating solution. However, the modification using acetone and cyclohexanone solvents was unsuccessful because a reduction in membrane hydrophobicity was observed. The modified PTFE HF membrane with ethanol content exhibits high wetting resistance with a high water contact angle, which can withstand pore wetting during the direct contact MD process. Since MD operates under a lower operating temperature range (50–90 °C) compared to the conventional distillation, we herein demonstrated that higher flux could be obtained at 7.26 L m–2 h–1. Thus, the process is economically feasible because of lower energy consumption. Performance evaluation of the modified PTFE HF membrane showed a high rejection of 99.69% for sodium chloride (NaCl), indicating that the coated membrane preferentially allowed only water vapor to pass through.