Fast technique for the purification of as-prepared graphene oxide suspension

Abstract

Improved Hummer's method is widely used to prepare graphene oxide (GO), which is a precursor of graphene. Purification of as-prepared GO is challenging due to the used corrosive acidic media, large amounts of impurities are formed as byproducts during GO production, and the long time required for purification process. GO purification with traditional methods is difficult and time consuming. Novel methods for fast purification of as-prepared GO without pre-treatment was developed using commercially available hollow-fibre dialyzer (Phylther-1.7 m2). The dialyzer can be used several times in a crossflow filtration or dialysis process in the designed systems without deteriorating. The concentrations of impurities in GO suspension were monitored during purification process by measuring the ionic conductivity of the GO suspension. For process optimization, the factors affecting the purification methods were studied. The results showed that exfoliated GO can be purified in <1 h. Moreover, the concentration of purified GO was 6 mg/mL when using cross-flow filtration. X-ray diffraction (XRD), Fourier transform infrared (FTIR), field emission scanning electron microscope (FESEM), energy-dispersive X-ray spectroscopy (EDX) and atomic absorption spectroscopy (AAS) were used to characterize the purified GO. EDX results showed complete removal of potassium and phosphorous impurities, and only sulfur and manganese remained in GO. Mixing the purified FGO sample with HCl followed by a second stage of cross-flow filtration greatly reduced manganese and sulfur contents.