Search

Highly porous polyvinylidene fluoride (PVDF) hollow fiber membranes are of great interest for membrane contactor applications such as sea water desalination by membrane distillation in order to enhance the flux of the process. For the first time in this paper, porous hydrophobic PVDF asymmetric hollow fiber membranes with a high outer surface porosity for use in vacuum membrane distillation (VMD) were successfully fabricated by applying a simultaneous co-extrusion spinning process through the non-solvent induced phase separation (NIPS) method. In this approach, five kinds of dual-layer composite membranes were prepared by employing different inner and outer polymer dopes. Single-layer membrane was also fabricated through the conventional dry-jet wet phase inversion method. Results revealed that the introduction of the simultaneous co-extrusion spinning process greatly increased the outer surface porosity of the dual-layer composite membranes. It was also observed that the VMD flux of the dual-layer membranes spun through the simultaneous co-extrusion spinning process was 54% higher than the single-layer membrane fabricated by the conventional dry-jet wet phase inversion method. A VMD flux as high as 61.8 kg/(m 2 h) at 70 °C was obtained for the novel dual-layer composite membranes. [ABSTRACT FROM AUTHOR]

Mixed matrix membranes combining the processibility of polymers with the properties of porous nano-additives is an effective method to enhance the performance of membrane distillation (MD) process. In this work, a new type of hydrophobic hybrid PVDF hollow fiber membranes doped with aluminum fumarate metal-organic frameworks (AlFu MOF) was fabricated and their performance in direct contact membrane distillation were studied experimentally and theoretically. The results showed that the addition of MOF particles efficiently enlarged the effective porosity of membrane and increased the water flux as well as the thermal efficiency of MD process. At 1 wt% MOF loading, the effective porosity of membrane was enlarged by 52.4%, which induced 55.9% increment in overall mass transfer coefficient of the hybrid membrane, and the thermal conductivity of the membrane was decreased by 38.6%, which contributed to the reduction of sensible heat loss of MD. Correspondingly, the experimental water flux of the hybrid 1 wt% MOF/PVDF membrane was improved by 50.5% and the thermal efficiency increased by 46.2% (0.58 vs 0.31) at a feed temperature of 40 °C. Moreover, the MOF/PVDF membrane exhibited stable flux and retained high salt rejection (>99.9%) for 3.5 wt% NaCl solution over a 50 h desalination test period. Overall, this study provides an insight into the positive effects of AlFu MOF additives on the enhancement of membrane performance in distillation process. Image 1 • Aluminum fumarate MOF was blended with PVDF to fabricate hollow fiber membranes. • Effects of nanoparticle on membrane structure and performance were investigated. • Hybrid membranes showed 50.5% higher flux and 46.2% higher thermal efficiency. • The mechanism on the enhancement of heat and mass transfer performance were revealed. [ABSTRACT FROM AUTHOR]