Green preparation of PVDF hollow fiber membranes with multiple pore structure via melt spinning method for oil/water separation

Poly(vinylidene fluoride) (PVDF) is one of the most widely used membrane forming polymers with good processability, outstanding mechanical properties, excellent thermal and chemical stability. In this work, PVDF hollow fiber membranes were prepared through the melt spinning method with CaCl2 and PEG as the composite pore forming agents. The influence of different contents of CaCl2 and PEG on the membrane's structure and properties were studied based on the pore size distribution, porosity, permeation flux, and oil/water separation test etc. There was no obvious dense layer on the PVDF hollow fiber membrane surface, which exhibited multiple pore structure. With the increase of PEG contents, the pore size, the porosity and oil flux improved effectively, correspondingly, the water contact angle and liquid entry pressure decreased. The permeation fluxes of kerosene also increased obviously with the increase of PEG contents, and the maximum flux of M-3 reached as high as 398.4 L center dot m-(2)center dot h(-1). Applied to oil/water separation test, M-3 exhibited good oil/water separation performance, and its separation efficiency for water-in-kerosene emulsion can still reach more than 95 % after ten cycles. In particular, there were not any solvents and diluents used in the preparation process, which was a relatively green preparation process.

Automated summary

Poly(vinylidene fluoride) (PVDF) hollow fiber membranes were prepared through melt spinning method with CaCl2 and PEG as composite pore forming agents. The addition of PEG effectively improved the membrane's pore structure and permeation performance, while reducing the water contact angle and liquid entry pressure. The membranes also exhibited good oil/water separation performance.