Nanoscale capture and evolution behaviors of oily aerosols by different wettability membranes

Oily aerosols in the submicron size range pose a tremendous threat to the natural environment and human health. Although nanofiber membranes have been widely used to separate oily aerosols from the air, their filtration behaviors are not yet clearly understood. In this work, we investigated the nanoscale capture and evolution behaviors of oil droplets on membranes with varying wettability using an optical microscope. The findings indicate that the surface wettability of the membranes significantly influences the filtration performance of oily aerosols arising from their varied interfacial interactions. The captured oil droplets have a small contact area on the amphiphobic nanofibers and take on a non-axisymmetric conformation. As the capture process continued, larger oil droplets accumulated on the membrane and eventually detached from the membrane due to the force of gravity. This is beneficial regenerating nanofibers and improving capture efficiency. In comparison, the captured oil droplets coalesce on the oleophilic membrane to form a liquid film and eventually penetrated the bottom surface of the membrane, leading to an increase in pressure drop and a decrease in filtration efficiency. This work offers valuable insights into the filtration mechanism of oily aerosols using membranes with varying wettability and provides guidance for the design and development of high-performance membranes.