Green Construction Of Bio-Based Multi-Hierarchical Nanofiber Membrane And The Application In Air Filtration

In recent years,with the acceleration of industrialization,air pollution not only causes the imbalance of ecological environment,but also directly affects human health.Therefore,there is an urgent need to develop effective air filters to intercept particulate matter（PM）.Electrospun nanofibers have become an effective media to manufacture high-performance air filters due to their typical advantages such as uniform nanofiber structure,high specific surface area,good internal connectivity and strong controllable morphology.However,the common fiber structure with uniform stick-like morphology showed poor physical interception for air pollutant molecules.To address this issue,designing multi-hierarchical nanofibers with rough surfaces could be an effective method to improve the poor interception ability of stick-like fibers.In addition,most electrospun nanofibers consume much solvents in the process of preparation and cause secondary pollution to the environment.In order to protect the environment and adapt to the sustainable development in the future,the nanofiber membrane should require sustainability and non-toxicity.Therefore,this work has selected water-soluble polymer and forest-derived bio-based molecule as raw materials,combined with electrospinning technology and crosslinking modification technology,constructed of a series of eco-friendly nanofiber membranes with typical multi-hierarchical structure for high-efficiency air filtration.Specific research content as follows:（1）The water-soluble polymer PVA was used as the matrix,and the bio-based molecule material sodium phytate（PANa）was introduced for crosslinking modification.The eco-friendly thermal crosslinking polyvinyl alcohol/sodium phytate（T-PANa/PVA）nanofiber membrane with granular-convex structure was prepared for air filtration.The self-aggregation effect of PANa was used to create a unique granular-convex secondary structure on the surface of the nanofibers,which improved the physical interception efficiency of the fibers against PM.The results showed that the granular-convex fibers after thermal treatment have good mechanical properties,and the tensile strength of the fiber membrane after crosslinking has increased by nearly 4 times to 21.3 MPa.Meanwhile,it has excellent water resistance,and the fiber structure remain stable after soaking for several days.In addition,when the air filtration pressure drop is36.5 Pa,the efficient filtration performance of PM_2.5 is maintained（>99.9%）,and the quality factor（QF）reaches 0.199 Pa^-1.（2）Fiber membrane with fluffy and breathable characteristics has more prominent advantages as an air filtration material.Based on the above research,the green electrospinning method was used to prepare a fluffy and highly breathable curved-ribbon structure of sodium sulphobutylether-β-cyclodextrin/polyvinyl alcohol（SBE-βCD/PVA）nanofiber membrane for high performance air filtration.The fast solvent evaporation strategy in the process of electrospinning was used to prepare curved-ribbon nanofibers.The fluffy structure and unique morphology endow the fibers with good air permeability.Compared with the ordinary nanofiber membrane,the curved-ribbon nanofiber membrane has excellent filtration performance,realizing the efficient filtration of small particles PM_1.0（99.12%）while QF reached 0.082 Pa^-1.After replacing the core-filter layer of commercial masks,the assembled masks have a filtration efficiency of nearly 100%against PM_1.0-10 with low air resistance（<60 Pa）and maintain long-term high performance filtration.（3）On the basis of the above research,an eco-friendly,high-performance and biosafe polyvinyl alcohol/sodium alginate/hydroxyapatite（T-PVA/SA/HAP）nanofiber membrane was prepared by green electrospinning and thermal treatment.The secondary structure is regenerated on the surface of nanofibers by utilizing the mineralization effect of hydroxyapatite（HAP）to create a unique wrinkled helical structure and improve the physical interception ability of the fibers.In addition,HAP endows the nanofiber membrane with the ability of electrostatic adsorption.Under the synergistic action of electrostatic effect and physical interception,the nanofiber membrane showed outstanding performance in capturing small particulate matter PM_0.3(filtration efficiency exceeded 99%,QF reached 0.042 Pa^-1).After several cycles,the filtration efficiency remained stable（>99%）.In addition,through the co-culture of the fiber membrane with zebrafish larvae,the fiber membrane under the green preparation technology has good biosecurity,and possesses great application prospects in the field of personal protection.