Abstract:

Objective In recent years, the rapid development of the economy has been accompanied by increased air pollution, leading to frequent hazy weather conditions. Consequently, particulate matter has emerged as the primary pollutant in outdoor air pollution in our country, posing serious health risks to people. Electrospun nanofiber membranes show promise in air filtration due to their small diameter, three-dimensional porous structure, and large surface area. However, the low strength of these nanofiber membranes limits their large-scale industrial application. In this study, we employ chitosan, known for its antibacterial, biodegradable, and biocompatible properties, to prepare an environmentally friendly antibacterial air filter.

Methods The raw materials used were chitosan spunlaced nonwovens (CS), chitosan (CHI), and polyethylene oxide (PEO). By electrospinning technology, a layer of chitosan/polyethylene oxide (CHI/PEO) nanofibers membrane was electrospun on the surface of CS, and then a composite air filter (CHI/PEO-CS) was obtained. Then, the micro-morphology, fiber diameter, pore size distribution, and air permeability of CHI/PEO nanofiber membranes with different PEO concentrations were measured. Finally, the antibacterial properties of the CHI/PEO-CS composite membrane were studied by testing the filtration performance of the composite membrane and selecting the appropriate PEO concentration.

Results The average fiber diameter of CHI/PEO fibrous membranes gradually extends from 111 nm to 198 nm with incensing the concentration of PEO. And the average fiber diameter of the CS spunlaced nonwoven fabric is relatively large and about 11.5 μm. With the combination of CHI/PEO nanofibers and CS spunlaced nonwoven fabric, an air filtration membrane was constructed, while the electron microscopy images demonstrate a good adherence between CHI/PEO nanofibers and the CS substrate. The combination of CHI/PEO with CS is solely a physical composite, indicating that there are no chemical reactions between the components. When the concentration of PEO varies between 0.3% and 0.6%, the strength of CHI/PEO-CS remains relatively constant, indicating that the electrospun CHI/PEO nanofibers exert a minimal impact on the mechanical strength of the spunlaced nonwoven fabric. This observation suggests that CS significantly enhances the mechanical properties of CHI/PEO-CS.The pore size distribution of the CHI/PEO-CS composite membrane shows two distinct peaks. The first peak corresponds to the CHI/PEO fiber membrane, while the second represents CS, and the change in pore size follows the trend in fiber diameter. With the increase of PEO concentration, the air permeability was improved accordingly, although the filtration efficiency initially increases and then decreases. Based on these results, we chose a PEO concentration of 0.45% with the highest quality factor for further study. At this concentration, the filtration efficiency of CHI/PEO-CS for 300 nm NaCl aerosol particles significantly increased from 1.6% (in original CS) to 99.56%, with a pressure drop of 63 Pa. Furthermore, after multiple cycles and prolonged testing, the filtration performance of CHI/PEO-CS consistently remained above 99%. Additionally, the interception ratios for E.coli and S.aureus were 99.97% and 99.88%, respectively, significantly surpassing that of pure CS, providing enhanced protection in practical applications.

Conclusion In order to prepare a kind of environmentally friendly antibacterial air filtration material, a layer of chitosan/polyethylene oxide (CHI/PEO) nanofibers membrane was electrospun on the surface of chitosan spunlaced nonwovens (CS), it was found that the CHI/PEO-CS composite membrane with PEO concentration of 0.45% had better comprehensive properties, including fiber morphology, air permeability (246.2 mm/s), and mechanical properties (2.26 MPa), excellent antibacterial performance (interception ratio >99.88%), high filtration efficiency (99.56%) and lower pressure drop (63 Pa). Therefore, a kind of composite filter material composed entirely of chitosan, was successfully prepared which has both excellent strength of micro-fiber good filtration performance of nano-fiber, and good antibacterial performance. This work provides a new idea for the research and development of functional air filtration materials.

Key words: chitosan spunlaced nonwoven, nanofiber, micro-nano composite, antibacterial, air filtration