Science and Technology Daily (Reporter Wang Zhuhua and Intern Qu Yizhen)

Recently, the reporter was informed by Hainan University that Prof. Liu Yanan at the university, in collaboration with Prof. Mark Olivier Coppens, a professor at the University of London in the UK, provided new insights into the study of the manufacture of high-performance membranes for oil/water separation.

In addressing the challenges of severe shortage of fresh water resources and environmental pollution by oily wastewater, membrane technology has many advantages over conventional water treatment technologies, including highly selective separation, low energy consumption, simple equipment and low space requirements as well as continuous and automated operation, especially for the separation of emulsified oil/water mixtures.

It is understood that Prof. Liu Yanan, inspired by the structure of cell membranes, including water channel proteins with hydrophilic gates for selective transport and hydrophobic channels for low friction with water, prepared and fabricated a graphene nano-web membrane through a vacuum-assisted self-assembly process. On this basis, nano-pores were synthesized to reduce the length of the mass-transfer channels, which combined with the low friction between the graphene nano-sheets and water molecules to achieve a high permeability. Chitosan with hydrophilic hydroxyl and amino groups was used to modify the retinal membrane to increase its hydrophilicity and induce the formation of a hydrated layer on the membrane surface. The mesh has high hydrophilicity, superoleophobicity and low oil adhesion underwater. The membranes prepared in this study exhibited excellent anti-fouling properties when used to separate oil-in-water emulsions stabilized with various surfactants.

It is reported that graphene oxide, which has a two-dimensional carbon structure and the thickness of a single carbon atom, has become a popular membrane material due to its unique properties. At an average air pressure, the hourly permeation flux of this graphene nano-mesh membrane reaches almost 4,000 liters per square meter, which is about 260 times higher than the permeation flux of GO membranes. The membrane showed excellent anti-fouling performance in separating oil-in-water emulsions stabilized by a variety of surfactants, and the water flux recovery of a variety of emulsions exceeded 96.7%, which remained above 95.2% after three cycles.

The related findings were published in the international academic journal Advanced Functional Materials under the title of "Graphene Nano-membranes Inspired by Cell Membranes for Rapid Separation of Oil-in-Water Emulsions".