Abstract:

Objective Particulate pollutants in the air are the main cause for air pollution, threatening public health and ecological environment. The requirements for air quality around the world are becoming more and more stringent. However, traditional petroleum-based synthetic polymer fiber filter materials may cause secondary pollution to the environment due to their non-degradable properties. Therefore, it is of great significance to study biodegradable air filtration materials. Due to the good membrane forming, biodegradability, biocompatibility and rich functional groups of zein, more and more research has been carried out in the field of air filtration in recent years.

Method Using ethylene-vinyl alcohol copolymer (EVOH) and zein as raw materials, the mixed fiber membranes of zein and EVOH were prepared by single-needle two-component and double-needle two-component electrospinning, respectively. The fiber morphology prepared by two different electrospinning methods was studied, and the filtration performance and mechanical properties were compared and analyzed by attaching the nanofiber membrane to the commercial cellulose paper towel to form a composite filtration.

Results The EVOH/zein composite filter prepared by two-needle two-component electrospinning showed better performance than the single-needle two-component electrospinning EVOH/zein-n filter. Under the condition of controlling the weight, the filtration efficiency of the single-needle two-component electrospinning EVOH/zein-n filter was 26.8%-50.7%, the pressure drop was 19.2-39.6 Pa, while the pressure drop of the pure EVOH filter was 45.2 Pa. The filtration efficiency of the two-needle two-component electrospinning EZr filter is 43.2%-93.0%, and the pressure drop was 10.1-74.6 Pa. Among them, the EZ20 filter has the best filtration performance, the filtration efficiency reached 94.5%, and the quality factor of the EZr composite filter was greater than that of the pure EVOH and zein filters. Under the condition of controlling the flow rate, when the zein concentration was 20%, the air filtration stability of the EVOH / zein mixed filter was the best, the filtration efficiency increased from 92.45% to 98.19%. With the increase of flow rate, the pressure drop of the filter also increased, from 34.9 Pa to 184.5 Pa. When the particle size was 3-5 μm, the over-rate efficiency of the pure EVOH filter was 96.13%, while the EZr filter achieved 100% filtration efficiency, and EZ20 achieved about 100% filtration efficiency for PM_0.5-PM₃ including PM_2.5. In addition, the breaking strength of EZr fiber membrane was between that of pure zein fiber membrane and pure EVOH fiber membrane, and the breaking strength of EZ20 fiber membrane was 72.87 cN, which is 7 times that of pure zein fiber membrane.

Conclusion An environmentally friendly EVOH/zein filter was prepared by electrospinning EVOH/zein nanofibers on cellulose paper towels. By studying the single-needle two-component and double-needle two-component electrospinning, it is found that the EVOH/zein composite fiber prepared by single-needle two-component electrospinning is a circular structure with smooth surface, which is different from the flat ribbon zein fiber. It is not conducive to capturing particulate pollutants and shows poor air filtration performance. In the EVOH/zein composite filter prepared by double-needle opposite electrospinning, circular EVOH fibers and flat ribbon zein fibers are interlaced, and have the same filtration efficiency and lower pressure drop as the pure zein filter. In the study of mechanical properties, the mechanical properties of the prepared filter were significantly improved by mixing EVOH fiber with zein fiber, leading to good stress and strain. The mechanical properties also show more obvious advantages. This study will provide ideas for the further development of air filters.

Key words: zein, ethylene-vinyl alcohol copolymer, counter-jet electrospinning, air filter, composite filter material