Improvement of Air Filtration Performance Using Nanofibrous Membranes with a Periodic Variation in Packing Density

Abstract

particulate matter (particle size > 10 µm), inhalable particulate matter (particle size < 10 µm), and fine particulate matter (PM 2.5 , equivalent diameter < 2.5 µm). [1] PM 2.5 particles are particularly harmful because they can be inhaled into the lungs and even enter the blood circulatory system, causing health issues. [2] PM 2.5 particles are also a good carrier of bacteria and viruses, resulting in the transmission of diseases, such as COVID-19. [3] Filtration with a filter is an effective method to remove these harmful particles and prevent the diseases from spreading.The removal mechanism of fibrous filters for these tiny particles mainly includes inertial collision, [4,5] direct interception, [6] diffusion effect, [7] gravity sedimentation, [8] and electrostatic attraction. [9] Nanofibrous filters have outstanding filtration efficiency due to the fine fiber diameters and high specific surface areas. [10] In addition, nanofibers have lower pressure drop due to the "slip effect" of their unique fiber diameter size, similar to the mean air molecule free path, reducing the airflow resistance. [11] Hence, nanofibers are widely used in air filtration, especially in air filters, [12][13][14] ventilating and air conditioning filters, [15] and masks. [16] Xia et al. [17] compared 122 nanofibrous filters with conventional heating, ventilation, and air-conditioning (HVAC) filters and showed that nanofiber filters had a higher quality factor than the conventional filters because of nanofibers' "slip effect."Considerable research has been devoted to understanding the structural parameters of nanofibers and their effect on filtration performance. For example, Wang et al. [18] studied the influence of nanofiber morphology on filtration performance. Zhang et al. [19] reported a pore size gradient combination of different nanofibrous membranes, which showed a filtration efficiency of 99.992% for 300 nm particles at a low-pressure drop. Li et al. [20] proposed a mathematical relationship between filtration efficiency and nanofibrous pore size. Bian et al. [21] established a semiempirical model to predict the influence of nanofiber diameter, membrane thickness, and packing density on the pressure drop of nanofibrous filters. Most studies have been based on nanofiber membranes with a homogenous distribution of nanofibers along the membrane.This study reports a patterned nanofibrous membrane and its novel filtration performance. The nanofibers are prepared using an electrospinning technique, and the nanofibers are collected on a commercial nonwoven fabric covering a roller collector, which is prepared using a metal sheet with a round hole array. The nanofibers collected on the metal surface have a much denser structure than those in the hole areas. As a result, the patterned nanofibrous membrane has a different filtration performance (lower pressure drop and filtration efficiency) from the uniform nanofiber membrane, prepared under the same condition but using a smooth roller collector. When two layers of this patterned nanof...

Microfluidic Spinning of Metal–Organic Framework-Loaded Nanofibers toward High-Efficient Particulate Matter Removal and Antibacterial Filters

“…Obviously, with the particle size increasing from 0.5 to 10 μm, the Q f increased for both the pure polymer and the ZIF-8@CCM-loaded composite nanofiber membrane. Meanwhile, compared with the pure polymer nanofiber membrane, the ZIF-8@CCM endows the composite nanofiber membrane with a higher Q f , which is comparable to other membrane filtration materials reported in the literature. − The above results indicate that the ZIF-8@CCM-loaded composite nanofiber membrane has good PM removal efficiency, which can be attributed to the following. On the one hand, due to the high porosity and excellent pore connectivity, the particles are blocked in the nanofiber membrane.…”

Natural Fiber-Reinforced Thermoplastic ENR/PVC Composites as Potential Membrane Technology in Industrial Wastewater Treatment: A Review

“…Membrane technology is developing rapidly, following its use in a variety of applications [66][67][68][69][70]. A membrane is an intermediary between two adjacent phases that acts to control the transport of a substance that has different components [14].…”

Phase separation patterned films of natural materials: Preparation of mixed monolayers of nanocellulose integrates and organo‐modified nanoclays

“…27 Therefore, mixed monolayers of CNF and organomodified nanoclays can be preparted. 28 The development of a mixed membrane system consisting of CNF and nanoclay is considered to be of great significance due to their possible applications, such as air filtering for CNF 29 and absorbency for nanoclays. 30 In this study, mixed Langmuir monolayers were prepared by spreading cellulose acetate and organo-modified montmorillonite at various ratios at the air-water interface (Figure 1C).…”

“…Therefore, mixed monolayers of CNF and organo‐modified nanoclays can be preparted 28 . The development of a mixed membrane system consisting of CNF and nanoclay is considered to be of great significance due to their possible applications, such as air filtering for CNF 29 and absorbency for nanoclays 30 …”