An improved Hummers method for eco-friendly synthesis of graphene oxide

An improved Hummers method without using NaNO3 can produce graphene oxide nearly the same to that prepared by conventional Hummers method. This modification does not decrease the yield of product, eliminating the evolution of NO2/N2O4 toxic gasses and simplifying the disposal of waste water because of the inexistence of Na+ and NO3− ions. For the first time, we also developed a prototype method of post-treating the waste water collected from the systems of synthesizing and purifying graphene oxide. The content of Mn2+ ions in the purified waste water was measured to be lower than the guideline value for drinking water.