Development of phosphorylated silica nanotubes (PSNTs)/polyvinylidene fluoride (PVDF) composite membranes for wastewater treatment

• Phosphorylated silica nanotubes (PSNTs) were successfully prepared.
• PSNTs were doped to PVDF to prepare a novel PSNTs/PVDF composite membrane.
• The property of anti-fouling and anti-compaction of PVDF membranes are enhanced.
• PSNTs/PVDF membranes are desirable in the treatment of wastewater.

PVDF membranes are broadly applied in many fields owing to their good physicochemical stability, resistance to oxidation and chlorine. However when treating with wastewater, PVDF membranes are easily contaminated by pollutant, degrading their properties due to the hydrophobicity and poor anti-compaction capabilities. It leads to declining flux and shorting lifespan of PVDF membranes, which further limits their large scale applications. In order to enhance the integrative capabilities of PVDF membranes, PSNTs were firstly prepared and then doped to PVDF to form a novel PSNTs/PVDF composite membrane through a phase inversion technique. The preparation conditions of PSNTs/PVDF composite membranes were studied. And the effect of PSNTs on performance of composite membranes was investigated through the Fourier transform infrared (FT-IR), contact angle measurements, tensile strength measurements, flux of membranes and oil retention ratio experiment. The results show that the contact angle of PSNTs/PVDF membrane is declined from 68.0° to 43.2° and the tensile strength of PSNTs/PVDF membrane is improved from 1.18 MPa to 2.76 MPa. When treating with wastewater containing oil (45 mg/L), the flux of PSNTs/PVDF composite membrane reaches 251 L/(m2 h) while the flux of PVDF membrane only is 152 L/(m2 h). Meanwhile, the oil retention for PSNTs/PVDF membrane is improved from 86.00% to 95.51%. Therefore, PSNTs/PVDF composite membranes are desirable in the treatment of wastewater containing oil and wastewater.