Tailoring asymmetric wettability of Janus nanofiber membranes for directional oil transport and oil capture from oil/water mixtures and oil-in-water emulsions

Abstract

The separation of oil from oil-in-water emulsions is crucial for the recycling of valuable resources. Janus membranes, characterized by their asymmetric configuration, have shown promise in capturing oil from these emulsions due to their ability to efficiently catch micro-size oil droplets with competitive flux rates, minimal energy costs, and fouling-free operations. This study explored the impact of asymmetric wettability on the oil capture capabilities of Janus nanofiber membranes (JNMs). The wettability of the JNMs’ skin layer was modified from oleophilic, with an oil contact angle (OCA) of ∼0°, to oleophobic, with an OCA of ∼142.7°. This adjustment significantly influenced the oil capture process. The oleophobic skin layer acted as a barrier, reducing oil permeation flux from the feed side. However, this same repellent effect facilitated the directional transport of oil once it breached the skin layer. Interestingly, this led to divergent outcomes in the JNMs’ ability to capture oil from oil/water mixture versus oil-in-water emulsion, a distinction not reported in previous studies. These findings are expected to contribute to the enhancement of Janus membranes, optimizing them for more efficient oil recovery from both oil/water mixture and oil-in-water emulsion.