Optimizing electrospinning parameters for piezoelectric PVDF nanofiber membranes

In this study, nanofiber membranes were fabricated using electrospinning to induce piezoelectric properties. Optimization of the piezoelectric properties was achieved using the Taguchi design method to systematically vary the electrospinning parameters (acetone fraction, tip-to-collector distance (TCD), flow rate, and voltage setting). The optimized settings for piezoelectric properties were a solvent ratio of 60 v% DMF/40 v% acetone, a TCD of 16 cm, a flow rate of 0.8 mL/h, and a voltage setting of 14 kV. Additionally, the effect of three solvents (dimethylformamide, N-methylpyrrolidone, and dimethyl sulfoxide) on fiber formation and piezoelectric properties was compared; dimethylformamide (DMF) created the smallest fiber diameter and highest piezoelectric properties. During filtration of a synthetic solution mimicking biofouling, severe fouling was observed for both the commercial flat-sheet PVDF microfiltration membranes and unactivated electrospun membranes, although fouling occurred at different times for the electrospun membranes fabricated with different solvents. Little to no flux decline or increase in TMP was observed for the piezoelectrically activated nanofiber membranes. Total suspended solids removal of anaerobic digester mixed liquor for the electrospun membranes were comparable to the commercial PVDF microfiltration membrane. The results demonstrate that piezoelectrically activated nanofiber membranes have the potential to mitigate fouling in water treatment applications, particularly for systems with high levels of biofouling that require suspended solids separation (i.e., membrane bioreactors).