Kinetic study of application of graphene oxide as a catalyst to accelerate extraction of total flavonoids from Radix Scutellaria

A new kinetic model, So's three-step kinetic model, was used to study the kinetics of graphene oxide (GO)-assisted ethanol reflux extraction (GERE). An experimental design to investigate the effect of five single factors (extraction temperature, dosage amount of GO, concentration of ethanol aqueous solution, the ratio of liquid to solid, rotating speed) on the kinetic extraction of total flavonoids was materialized. From the single factors experiments, we found that the extraction process is mainly controlled by internal diffusion, and the extraction rate increases with the growth of GO dosage, ethanol concentration and liquid–solid ratio at 30–70 °C; moreover, the rotating speed had little effect. The effective internal diffusion coefficient (D′) and the activation energy (Ea) of total flavonoids extracted by ERE and GERE were also studied, respectively. Results showed a good prediction of So's three-step kinetic model for extraction kinetics in all experiments, which gave the possibility for estimating the initial rate and extent of GERE.