Low-pressure-driven special wettable graphene oxide-based membrane for efficient separation of water-in-oil emulsions

Abstract

Oil and water separation is a significant challenge due to the rapid discharge of oily wastewater. Special wettable membranes have received substantial consideration in emulsified oil/water separation. Here, a superhydrophobic octadecyl-functionalized crosslinked graphene-oxide-grafted ceramic membrane (R18-CLGO-N-CM) was designed to separate water-in-oil emulsions. The selective layer of the ceramic membrane was evaluated using molecular dynamics simulation studies to understand its mechanism and separation capabilities. The underwater oil contact angle on the surface of the R18-CLGO-N-CM was dramatically reduced, from 141.3° ± 1.5° to 0°, and the water contact angle in air increased from 0° to 152.8° ± 0.6°, after functionalization. High hexane permeability was observed in the range of 294 to 311 Lm−2 h−1. The octadecyl-functionalized crosslinked graphene oxide acts as an excellent separating layer to selectively allow oil passage with a separation efficiency of ~99% for water-in-oil emulsion. The designed membranes show excellent antifouling behavior while dealing with water-in-heavy oil emulsions. The surface of the functionalized membrane was restored with a flux recovery ratio of 98.5% by simply treating the surface with dichloromethane while separating the water-in-light oil emulsions. This work shows that the rational functionalization and grafting of 2D materials on the membrane surface can significantly enhance the antifouling characteristics and the separation performance of the membranes.