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

Abstract

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.