Figure 3. Oil suction characteristics of graphene vessel.

(a) Dependence of oil suction rate on the thickness of oil (kerosene) layer. (b) Optical image of oil-water-rGO foam interface. A contact length much larger than the oil layer thickness exists at the interface because of the hydrophobicity and oleophilicity of the foam. Scale bar is 5 mm. (c) Recyclability of rGO vessel in terms of separation efficiency (oil purity). The efficiency is maintained better than 99.99% even after 100 cycles of usage, showing reliable reusability of the rGO vessel. (d) Separation efficiency of various oils and organic solvents. Gasoline, diesel, n-hexane, toluene, and 1,2-dichlorobenzene were successfully collected by the vessel showing high separation efficiencies above 99.97%. The inset graph shows water content of various oils and organic solvents. The inset figure is the optical image of crude oil collected by rGO vessel. The oil was collected by the rGO vessel dipped in crude oil for a month to check its chemical stability. Although various organic solvents, which dissolve organic compounds, are contained in crude oil, the vessel maintained its hydrophobic and oleophilic nature even after a month of direct contact with the crude oil.