Superior particle filtration of multilayer electrospun nanofiber air filters by combination of electrostatic and mechanical mechanisms

Abstract

Indoor particulate matter (PM) is a well-known airborne pollutant that threatens human health as it can penetrate the respiratory system and cause unexpected diseases. Air filtration was developed to maintain clean indoor air to protect human health. Among air filtration technologies, nanofibers synthesized by electrospinning are currently popular owing to their superior filtration performance and the low pressure drop caused by gas slip around the nanofiber. In this study, multilayer PVDF electrospun nanofiber air filters were developed with a hierarchical design that integrates two distinct filtration layers (S- and L-layers) to achieve high filtration efficiency with a low pressure drop. The S-layer is composed of thinner fibers with smaller pores to mechanically intercept particles larger than 100nm through inertial impaction and interception. In contrast, the L-layer is composed of thicker fibers and larger pores to effectively capture particles smaller than 100nm, aided by electrostatic attraction with minimal airflow resistance. Among the multilayer air filters, the 1S1L filter (pore size of 110 ± 77nm for 1S and 589 ± 290nm for 1L) achieved a filtration efficiency of 95.60% with a pressure drop of 48.38Pa (quality factor (QF)=0.064Pa⁻1). The 2S1L filter (pore size of 94 ± 60nm for 2S and 589 ± 290nm for 1L) demonstrated a high filtration efficiency of 99.62% with a pressure drop of 119.97Pa (QF=0.046Pa⁻1). The multilayer electrospun nanofiber air filters exhibit significant potential as a superior air purification technology with a low pressure drop for indoor environments.