Effect of different concentrations of spraying chitosan solution on structure and properties of PVDF porous membrane.

Polyvinylidene fluoride (PVDF) porous membranes were prepared by a two-step method of surface gelation-immersion precipitation phase inversion. The effects of spraying CS solution concentrations on the structure and properties of membranes were investigated. The results showed that with the concentration increasing of CS solution spraying on the surface of the casting solution film, the porosity of PVDF membranes gradually increased, the mean pore diameter of membranes firstly increased and then reduced, the surface contact angle decreased, and β crystal content in the top surface of membranes gradually decreased. The top surface of membrane without spraying CS solution displayed a dense structure, while the top surface of membranes after spraying CS solution exhibited a porous structure, while the cross-sectional structure of all membranes was composed of the finger-like voids. When the concentrations of spraying CS solution increased, the water flux of membranes firstly increased and then decreased. [ABSTRACT FROM AUTHOR]