Preparation and characterization of PVDF/TiO2 hybrid membranes with different dosage of nano-TiO2

PVDF/TiO2 hybrid microfiltration membranes with different nano-TiO2 dosage were prepared via thermally induced phase separation (TIPS) method, and dimethal-phthalate (DMP) was used as a diluent. The membranes prepared were characterized by scanning electron microscope, transmission electron microscope, X-ray diffractometer, Fourier-transform infrared spectroscopy and differential scanning calorimetry. Their properties such as pure water flux, contact angle, porosity and mechanical performances were also determined. Results showed that PVDF and PVDF/TiO2 hybrid membranes were formed by solid–liquid phase separation and had spherical crystallites structure with cells. The addition of nano-TiO2 particles to the PVDF/DMP mixtures had a strong effect on the crystallization temperature of hybrid membranes and crystallization formation in the TIPS process. The addition of the nano-TiO2 particles did not affect the type of PVDF crystal form (α phase). Nano-TiO2 particles were well distributed in PVDF matrix at the lower concentration and exist in a continuous phase and aggregated in PVDF matrix at the higher concentration. Pure water flux, contact angle, porosity, tensile strength and elongation at break first increased, then decreased with the increase of TiO2 dosage.

► PVDF and PVDF/TiO2 hybrid membranes are formed by S–L phase separation and have spherical crystallites structure with cells.
► The nano-TiO2 particles act as crystal nuclei in the phase separation process and affect the crystallization process.
► TiO2 particles are well distributed in PVDF matrix in nanometer size at lower content and aggregate at higher content.
► Hybrid membranes with certain amount of TiO2 dosage have small pore size, high porosity and narrow pore size distribution.
► The optimum TiO2 dosage for hybrid membrane by TIPS method is 0.45 wt%.