Rice husk ash and Zr-MOF nanoparticles improve the properties and ultrafiltration performance of PVDF nanomembranes

Abstract

Herein we demonstrate the effects of rice husk ash (RHA) and two Zr-metal organic frameworks (MOFs; OPA-UiO-66 and OPA-UiO-66-SO3H) nanoparticles on the properties and performance of polyvinylidene fluoride (PVDF) composite membranes. The nanoparticles and PVDF dope were pre-blended and fabricated as thin-film nanomembranes via soft lithography. The new membranes had uniform pore structures and demonstrated high permeability and durability. Improved tensile strength was associated with increased β crystalline formation of the PVDF, with the greatest increase observed for PVDF/RHA due to the high silica content of the RHA. RHA increased membrane hydrophilicity whereas the MOFs increased hydrophobicity. In ultrafiltration, the new membranes exhibited superior performance compared to conventional PVDF composite membranes made with titanium oxide and nanoclay. High rejection rates and significantly improved antifouling properties were achieved in both PVDF/RHA and PVDF/MOF membranes for high concentration aqueous solutions of sulfamethoxazole, bovine serum albumin, and SARS-CoV-2. This improved performance was attributed to multiple functional groups in RHA and MOFs that promote various surface interactions between contaminants and PVDF membranes. The new high-performance nanomembranes have potential applications in separation and purification processes, biosensing, and in personal protective equipment.