Sandwich-structured bimodal polymeric fiber/waste wool fiber bio-composite membrane for high-performance and eco-friendly air filtration

Air pollution due to fine airborne particles remains a pressing environmental challenge. To reduce the environmental footprint of air filtration technologies, it is crucial to develop sustainable, efficient, durable, and reusable solutions. In this work, sandwich-structured membranes based on waste wool fibers (WWF) were produced by combining a central layer of hot-pressed wool fibers with two layers of fibrous membrane based on polylactic acid (PLA) and waste wool powder (WWP) obtained by solution blow spinning (SBS) technique. The sandwich-structured waste wool based membrane (S-WWM) was tested for air filtration applications using different flow rates and environmental conditions. The addition of 10 wt% of WWP to PLA led to a modification in the solution viscosity, improving the morphology of the fibers. Thanks to the combination of small pores and low packing density S-WWM exhibited excellent PM₁ removal efficiencies of 99.5 % and pressure drops of 70 Pa at flow rate of 32 L/min. Moreover, the membrane maintained filtration stability up to 5 reuse cycles and durability under high humidity conditions. These membranes are characterized by the unique properties of wool fibers, such as excellent breathability and mechanical strength combined with high filtration efficiency achieved by PLA composite fibers. The findings showed that combining waste wool fibers with biodegradable polymers results in efficient air filtration devices while supporting environmental sustainability through waste valorization.