High-throughput production of low-cost hydrophobic and oleophilic mullite fiber sponges for high-temperature PM filtration

Particulate matter (PM) from high-temperature emissions like chemical plants, coal stoves and vehicle exhausts poses a gravel challenge to human health. To address this issue, researchers have explored various fiber filters, yet the bulk struggle to withstand high temperatures. In this study, mullite fiber sponges were developed utilizing low-cost materials and Kármán vortex solution blow spinning, using surfactants to improve the spinnability of the sol. Optimized sponges demonstrate ultralight (19 mg cm⁻³), temperature-resistant reversible compressibility (50% strain) and a water contact angle of 135°. These sponges exhibited exceptional thermal insulation (thermal conductivity: 0.0256 W m⁻¹ K⁻¹) and performed well in high-temperature air filtration. At 800 °C, the mullite sponge with a base weight of 35 mg cm⁻², achieved an average filtration efficiency of 98.18 % and 99.57 % for PM_2.5 and PM_2.5−10, respectively, with a quality value of 0.98 Pa^-1 at a wind speed of 4 cm s⁻¹. This low-cost mullite fiber sponge offers a promising avenue for designing high-performance filtration materials.