Preparation of Hyflon AD60/PVDF composite hollow fiber membranes for vacuum membrane distillation

Preparation of Hyflon AD60/PVDF composite hollow fiber membranes for vacuum membrane distillation

Tong,Daqing Wang,Xiaozu Ali, Mohammad Lan,ChristopherQ Wang,Yong Drioli, Enrico Wang, Zhaohui Cui, Zhaoliang


Highlights

•A novel Hyflon AD60/PVDF composite hollow fiber membrane was fabricated.

•Hydrophobicity of the PVDF hollow fiber membrane was significantly enhanced.

•The Hyflon AD60/PVDF composite membrane presents high VMD performance.

•The VMD stability of the PVDF hollow fiber membrane was significantly improved.


Abstract

Hydrophobic membrane is desired to avoid pore wetting phenomenon in membrane distillation (MD). In the present paper, highly hydrophobic Hyflon AD60/PVDF composite hollow fiber membranes were prepared by coating a copolymer (Hyflon AD60) of tetrafluoroethylene (TFE) and 2,2,4-trifluoro-5-trifluoromethoxy-1,3-dioxole (TTD) on poly(vinylidene fluoride) (PVDF) membranes. The effects of Hyflon AD60 concentration, coating time, heat-treatment temperature and heat-treatment time on the structures and performances of Hyflon AD60/PVDF composite hollow fiber membranes in vacuum membrane distillation (VMD) process were investigated. The results show that the hydrophobicity of PVDF hollow fiber membrane was significantly improved by coating Hyflon AD60. The optimized Hyflon AD60 concentration, coating time, heat-treatment temperature and heat-treatment time were 0.1 wt%, 10–20 min, 40–50 °C and 9 h, respectively. Employing NaCl solution with concentration of 35 g × L−1, under a vacuum of 0.09 MPa and feed temperature of 70 °C, the water flux and salt rejection of the composite hollow fiber membrane in VMD process reached to approximately 10 kg × m−2 × h−1 and higher than 99.9 %, respectively, and kept stable, indicating that Hyflon AD60/PVDF composite membrane is an excellent candidate for operation in VMD operation.

Keywords

Poly(vinylidene fluoride)
Hyflon AD60
Composite hollow fiber membrane
Vacuum membrane distillation
Hydrophobic modification


Outline

  1. Highlights

  2. Abstract

  3. Keywords

  4. 1. Introduction

  5. 2. Experimental

    • 2.1. Materials

    • 2.2. Preparation of Hyflon AD60/PVDF hollow fiber membranes

    • 2.3. Membrane characterization

    • 2.4. VMD test


  6. 3. Result and discussion

    • 3.1. Membrane properties

    • 3.2. Effect of Hyflon AD60 concentration

    • 3.3. Effect of coating time

    • 3.4. Effect of heat-treatment temperature

    • 3.5. Effect of heat-treatment time

    • 3.6. Mechanical properties

    • 3.7. Long-term performance of the Hyflon AD60/PVDF composite membrane


  7. 4. Conclusion

  8. Acknowledgments

  9. Appendix A. Supplementary material

  10. References