Spraying-assisted construction of robust polyvinylidene fluoride membrane with superhydrophobic property for water-in-oil emulsions purification

Construction of the hierarchical surface topographies is advantageous to develop the highly-permeable mem-brane with super hydrophobicity, which is conductive to the precise purification of water-in-oil emulsions. Herein, the robust superhydrophobic poly(vinylidede) fluoride (PVDF) membrane with the artificially tunable surface topographies was constructed by spraying the hydrophobic silicon dioxide (SiO2) particles onto the nascent cast film prior to the thermally induced phase separation. Benefiting from the self-adhesive property of PVDF, the SiO2 particles of two different sizes were firmly immobilized to the membrane surface, endowing resultant membranes with the micro-nano coarse structure and therefore the specific characteristic of super-hydrophobicity. The resulted membrane prepared at the optimal conditions exhibited the water contact angle and the water sliding angle of 160 & PLUSMN; 4 degrees and 3 & PLUSMN; 2 degrees respectively, accompanied with the averaged pore size of 330.8 & PLUSMN; 11.0 nm. Accordingly, it displayed the improved permeation fluxes of 1698 & PLUSMN; 119 L & BULL;m- 2 & BULL;h-1 and 2000 & PLUSMN; 129 L & BULL;m- 2 & BULL;h-1 with regard to the separation of the water-in-toluene and water-in-chloroform emulsions respectively, along with the separating efficiencies of 99.0 & PLUSMN; 0.2% and 98.7 & PLUSMN; 0.2% in terms of the oil purity in the penetrated solutions. Besides, the favorable reusability and stability of fabricated membranes demonstrated by the destructive experiments and cyclic performance tests might provide guarantee for the industrial water-in-oil emulsions purification.