Improving the electrospinning process of fabricating nanofibrous membranes to filter PM2.5.

To mitigate PM2.5 emissions is becoming a pressing concern, because these particles pose a threat to public health. Evidence shows that bead-free nanofiber with diameter of <100 nm is more likely to capture the PM2.5, however, currently it is impossible to fabricate bead-free nanofiber with such diameter without introduction of other substances. To fabricate bead-free polyacrylonitrile (PAN) nanofibers with diameter of <100 nm, we improved the electrospinning process of membrane fabrication via design of experiment (DOE), and we then used these nanofibers to filter PM2.5 emissions from burning cigarettes and fused deposition modeling (FDM) three-dimensional (3D) printing. The DOE was based on a L27 (313) orthodoxy array, which consists of six controllable factors, that is, the concentration of solution, the spinning voltage, the rotating speed, the tip-to-collector distance, the flow rate of the syringe pump, and the electrospinning temperature, each of them has three levels. The results showed that the nanofibers of the least diameter (i.e., 77 nm) can be fabricated under the following condition: 8 wt% PAN solution, 12 kV voltage, 5000 r/min, 12 cm tip-to-collector distance, 0.6 ml/h flow rate, and 50 °C electrospinning temperature. Range analysis and analysis of variance (ANOVA) showed that the concentration of PAN solution has the most significant effect on the diameter, and their values are positively correlated. An examination in a two-chamber filtering device showed the PAN membrane with the least fiber diameter has a PM2.5 filtration efficiency of 99.26%. A filtration test on standard FDM 3D printing process showed the membrane has a PM2.5 removal efficiency of 81.16%. This work could mitigate PM2.5 emissions from cigarette tobacco and FDM 3D printing, and it would be used to other scenarios, such as industrial and traffic emissions.