Synthesis of free-standing graphene in atmospheric pressure microwave plasma for the oil-water separation application

The synthesis of free-standing graphene in a microwave plasma at ambient conditions is currently of great interest. The past works have relied on the usage of higher microwave powers to synthesize free-standing graphene which is not only costly but also an obstacle to the industrialization of the process. The aim of this work was to bring down the cost of the process by synthesizing graphene at a significantly lower microwave power, i.e. 250 W. The formation of graphene was confirmed through Raman spectrum and scanning electron microscopy, where the Raman spectrum showed the signature 2D peak of graphene, and the vertical orientation of the graphene was observed in the microscopic images. The application of graphene in oil-water separation is demonstrated based on its hydrophobic and oleophilic properties. The as-synthesized pristine graphene coated on a melamine sponge showed a mass absorption capacity (57 g/g) comparable to that of functionalized or composite graphene.