Continuous oil/water separation using LDH-based membranes with inverse wettability

Oil spills and industrial oily wastewater pollution are two global environmental problems that necessitate the separation of oil and water. In this work, we present a novel continuous separation system based on two membranes with inverse wettability, both derived from a single adsorbent layered double hydroxide (LDH) through minimal surface modification. Drawing inspiration from biological surfaces, a superhydrophilic/underwater superoleophobic membrane was prepared by coating micro/nanostructured stainless-steel mesh with LDH, mimicking the wetting behavior of fish scales. A simple post-modification with stearic acid transformed the same LDH coating into a superhydrophobic/superoleophilic membrane, inspired by lotus leaf surfaces. These two complementary membranes were integrated into a bidirectional system capable of continuous and efficient separation of both light and heavy oil/water mixtures. The system achieved separation efficiencies over 98% and an ultrahigh flux of 105,000 Lm^-2h^-1. This study demonstrates a cost-effective, scalable approach to continuous oil/water separation using a single functional material, significantly advancing membrane design for environmental remediation.