PVDF mixed matrix ultrafiltration membrane incorporated with deformed rebar-like Fe₃O₄–palygorskite nanocomposites to enhance strength and antifouling properties

A novel PVDF mixed matrix ultrafiltration membrane was prepared by blending PVDF with the deformed rebar-like Fe₃O₄–palygorskite nanocomposites (MPGS) using the chemical coprecipitation method. Fe₃O₄ nanoparticles were anchored on the surface of the palygorskite nanofibers to form deformed rebar-like structures. MPGS were then distributed uniformly on the membrane matrix. PVDF chains firmly wrapped by the deformed rebar-like nanocomposites consequently enhanced the tensile strength of the PVDF membrane. At 7.0 wt % MPGS, the tensile strength increased from 1.59 MPa to 2.66 MPa. The overall thickness, skin layer thickness, finger-like voids, average pore size and surface roughness of membranes decreased with increasing amounts of MPGS. The rejection of the membrane increased to 99.09% at 7.0 wt % MPGS. The contact angle of membranes decreased from 99.14° (pure PVDF) to 78.76° (PVDF/7.0 wt % MPGS). On the other hand, the pure water flux of membranes increased from 123.57 L m⁻² h⁻¹ (pure PVDF) to 356.16 L m⁻² h⁻¹ (PVDF/7.0 wt % MPGS). The flux recovery rate of the mixed matrix membranes (PVDF/7.0 wt % MPGS) was as high as 80%. This was more than twice that of the pure PVDF membrane (31.6%). These results demonstrated that the deformed rebar-like structure of the MPGS played a critical role in determining the structures and properties of PVDF mixed matrix ultrafiltration membranes. The hydrophilicity, thermal stability, permeation flux and antifouling property of the mixed matrix membranes increased with addition of MPGS. As such, PVDF/MPGS membranes had excellent comprehensive properties thus making them ideal for application in numerous fields.