Exploration of Ultralight Nanofiber Aerogels as Particle Filters: Capacity and Efficiency

Abstract

Ultralight nanofiber aerogels (NFAs) or nanofiber sponges are a truly three-dimensional derivative of the intrinsically flat electrospun nanofiber mats or membranes (NFMs). Here we investigated the potential of such materials for particle or aerosol filtration because particle filtration is a major application of NFMs. Ultralight NFAs were synthesized from electrospun nanofibers using a solid-templating technique. These materials had a tunable hierarchical cellular open-pore structure. We observed high filtration efficiencies of up to 99.999% at the most penetrating particle size. By tailoring the porosity of the NFAs through the processing parameters, we were able to adjust the number of permeated particles by a factor of 1000 and the pressure drop by a factor of 9. These NFAs acted as a deep-bed filter, and they were capable of handling high dust loadings without any indication of performance loss or an increase in the pressure drop. When the face velocity was increased from 0.75 to 6 cm s, the filtration efficiency remained high within a factor of 1.1-10. Both characteristics were in contrast to the behavior of two commercial NFM particle filters, which showed significant increases in the pressure drop with the filtration time as well as a susceptibility against high face velocities by a factor of 105.

Semi‐Interpenetrating Polymer Network Biomimetic Structure Enables Superelastic and Thermostable Nanofibrous Aerogels for Cascade Filtration of PM2.5

“…The formation of this unusual morphology was not difficult to understand. Attributed to the high freezing‐front velocity of 166.7 µm s −1 (Methods Section, Supporting Information) generated by liquid nitrogen, the solidification front was faster than the mobility of the fibers; thus, dispersed nanofibers within the slurry would be trapped and embedded into the growing solvent crystals 16,29. It is worth noting that this specific uniform cellular structure combined the advantages of both electrospun nanofibrous membranes (random accumulation of nanofibers) and NFAs (high porosity and large thickness), all of which were helpful in achieving high air filtration performance.…”

“…However, because of the dense packing of nanofibers (with a limited porosity of <90%), electrospun air filtration materials tend to exhibit a high pressure drop, giving rise to large energy consumption. Moreover, as determined by the inherent anisotropic lamellar deposition character, electrospun NFMs suffer from a bottleneck in improving thickness (usually <100 µm), causing poor dust‐holding capability in the long‐term filtration process 15,16. More effective, energy‐saving, and durable air filtration materials that can alleviate PM from high‐temperature sources are long‐sought‐after yet largely unmet.…”

“…However, less solidity would also lead to the easy collapse of the cellular structure while large amounts of particles are deposited or subjected to high airflow velocity, as evidenced by the low compressive stress (≈1.4 kPa at a strain of 60%) and modulus (6.1 kPa) of PI NFAs. Moreover, electrospun NFAs derived from PI and other materials (e.g., polyvinyl alcohol) also suffer from a monoassembling structure parallel to the filtering direction, which would render the inability to collect PFPs as a uniform deposition pattern, resulting in a short service life 16,21. Therefore, the remaining challenge is to construct a heat‐resistant electrospun NFA with robust structural stability and variable cellular architecture for filtering PFPs effectively and enduringly even at high flow rates.…”

Novel micro‐spherical Si3N4 nanowire sponges from carbon‐doped silica sol foams via reverse templating method

“…Recently, with the development of emerging industries, nanofiber sponges generated by nanofiber interlocked with each other, have become promising candidates in the area of filtration, catalyst support, thermal insulators, energy storage, bone scaffolds and the like. As is well‐known, one of the most widely applied materials in the above area are light‐weight ceramic foams.…”

“…So far, several studies about ceramic nanowire aerogels have been proposed, which refer to the efficient solution blow‐spinning process for preparing various oxides ceramic including TiO 2 , ZrO 2 , yttria‐stabilized ZrO 2 and BaTiO 3 , and a facile chemical vapor deposition method for SiC nanowire aerogels . Moreover, Deuber et al . synthesized ultralight nanofiber aerogels/sponges from electrospun nanofibers by a solid‐templating technique, which exhibit high particle filtration efficiency.…”