LAUSR

Oil aerosol usually causes air pollution, health issues, and corrosion to equipment. The removal of aerosol oil particles from the air is a crucial process in industrial production and daily life. Though fibrous filters have been a widely used material for the separation of oil aerosol from the air, it is still a challenge to separate submicron aerosol oil particles with both high filtration efficiency and low resistance. Herein we report a novel approach to markedly reducing the pressure drop of a fibrous filter and simultaneously increasing its aerosol filtration efficiency, only by surface treatment to make the filter have an in-plane alternating superoleophilic and superoleophobic pattern. We used a spraying method to prepare superoleophobic and superoleophilic patterns on the filter. The best filtration results were achieved when two layers of the patterned filters that have superoleophobic and superoleophilic strips (both width 5 mm) were stacked in a way that the opposite wetting surfaces were contacted each other between the layers. The filter showed much-reduced filtration resistance, the pressure drop (4.16 kPa) at pseudo-steady state being at least 45% lower when compared to the two-layer controls with a homogenous surface wettability (i.e., untreated surface, superoleophobicity, and superoleophilicity). It also showed higher filtration efficiency (98.37%) and over two times higher quality factor (0.99 kPa-1 for small oil mists and 2.27 kPa-1 for large oil mists). The asymmetric wettability leads to the formation of unobstructed channels for the air stream to penetration through the filter matrix, leading to low resistance with improved oil capture efficiency. The pattern strip width showed an effect on filtration performance. This unexpected finding may provide a novel approach to design high-performance, low energy consumption, and long-life coalescence filters.