A superhydrophobic graphene@copper mesh irradiated by laser for efficient oil/water separation

Oil/water separation has become a global task due to the worldwide increase of oily wastewater. As such, developing membranes that could separate oil from water is of high importance. The aim of this work is to develop a copper mesh with superhydrophobic properties that has a high oil/water separation efficiency. To achieve this, a copper mesh was coated with a monolayer graphene/polydimethylsiloxane (PDMS) mixture in a one-step immersion process. Combining a fixed percentage of graphene (3 %) with three different ratios of PDMS (10 %, 5 % and 2.5 %) allowed us to investigate the effect of PDMS on the contact angle of the fabricated meshes. The Cu-mesh prepared by a 2.5 % PDMS solution displayed the highest contact angle of 133.3o +/- 0.5. Irradiating the samples with a Nd:YAG -1064 nm laser, that scans the whole area of the mesh, resulted in the improvement of the hydrophobic properties of the surface. It was also found that the laser-to-sample distance influenced the improvement of the contact angle. Graphene@Cu mesh, treated by laser at a distance of 1.5 mm above the laser focal point showed superhydrophobic characteristics with a contact angle of 155.6o +/- 0.3. The oil/water separation efficiency was measured for the fabricated meshes. The best developed mesh showed potential in separating both thick oils, such as HD-40 engine oil, and thin oils, such as toluene, from water with separation efficiencies of 92 % and 95 %, respectively.

Automated summary

The development of a superhydrophobic copper mesh for efficient oil/water separation was investigated in this study. A monolayer graphene/polydimethylsiloxane (PDMS) mixture was coated on the copper mesh to enhance its hydrophobic properties. By combining graphene with different ratios of PDMS, the effect on the contact angle of the fabricated meshes was examined. Irradiation with a Nd:YAG -1064 nm laser improved the hydrophobicity of the surface, with the best result achieved at a laser-to-sample distance of 1.5 mm above the laser focal point. The developed graphene@Cu mesh showed a contact angle of 155.6o +/- 0.3 and demonstrated high separation efficiencies of 92% for HD-40 engine oil and 95% for toluene.