A Robust Graphene/Poly(vinyl alcohol) Janus Aerogel with Hierarchical Architecture for Highly-Efficient Switchable Separation of Oil/Water Emulsions.

Abstract

Given the complexity and diversity of actual oily sewages, developing multifunctional separation materials with high separation efficiency and low energy consumption features for separating diverse oil/water emulsions is urgently needed, yet remains a formidable challenge till now. Herein a superior graphene/poly(vinyl alcohol) Janus aerogel (J-CGPA), showing an intriguing 3D hierarchical architecture (dense skin-layer and larger internal cell network) and desirable asymmetric wettability, was exploited via a simple direct freeze-shaping technique and subsequent mussel-inspired hydrophilic modification. Benefiting from the controlled unilateral decoration of dopamine (DA), the resultant aerogels displayed completely opposite superwettability on two antithetic sides, i.e., one side is highly hydrophobic (water CA, 143 °) while the other side is superhydrophilic. On the basis of the favorable 3D hierarchical structure and binary cooperative superwetting properties, the Janus aerogels achieved a remarkable switchable separation performance for both highly emulsified oil-in-water and water-in-oil emulsions as well as stratified oil/water mixtures accompanied with outstanding separation efficiencies. Particularly, an ultrahigh permeation flux of 1306 L m-2 h-1 along with a high rejection efficiency of 99.7% was acquired solely under the driving of gravity (<1 kPa), which is 1~2 order of magnitude higher than those of pioneering 2D Janus polymeric/inorganic membranes recently reported. Moreover, together with a robust reusability, this novel 3D Janus aerogel indicates a promising practical application for high-performance oily wastewater remediation.