Preparation of nano-porous poly(ether ether ketone) hollow fiber membrane and its performance for desalination in vacuum membrane distillation

Abstract

Nano-porous poly(ether ether ketone) (PEEK) hollow fiber membranes were successfully fabricated from PEEK/polyetherimide (PEI) blends via thermally-induced phase separation (TIPS) followed by chemical extraction of PEI method. The gas permeation rates, morphologies and mechanical properties of membranes were systematically investigated under different spinning conditions. The content of PEEK in blends substantially determined the gas permeation rates following the order: PEEK30/PEI70 (~9000 GPU) > PEEK40/PEI60 (~5100 GPU) > PEEK50/PEI50 (~1700 GPU) > PEEK60/PEI40 (~300 GPU) > PEEK70/PEI30 (below 1.0 GPU). Faster winding rates and bigger N2 bore fluid flow rates would result in bigger pores, higher porosity and larger gas permeation rates, while would cause lower mechanical strength. Furthermore, the silane-grafted hydrophobic PEEK hollow fiber membranes were successfully prepared via one-step reduction followed by silane modification. The performance of virgin and modified membranes was evaluated by treating saline feed containing 3.5 wt% sodium chloride in vacuum membrane distillation (VMD) process. Compared with virgin PEEK membrane, the modified membranes exhibited a more stable flux and higher salt rejection over 99.9 % for 33 h, indicating the significant improvement in the anti-wetting property caused by silane modification. The application attempt expands the research direction of PEEK membranes and promotes its further application potential in VMD process.