Abandoned fine blue-coke was modified with a physicochemical method including nitric acid (HNO3) treatment and nitrogen gas (N2) calcination, and used as an adsorbent for p-nitrophenol (PNP) removal. The preparation process was optimized to improve the adsorption ability based on the 2IV6–2 fractional factorial design, steepest ascending method and the Box–Behnken design (BBD) of the response surface methodology (RSM) technique. The significant factors on each experimental design response were identified by means of analysis of variance (ANOVA). The predicted adsorption capacity of PNP on MFBC was found to agree with the experimental values. The optimum experimental conditions were as follows: HNO3 concentration: 4.46 mol L−1, modification temperature: 87.8 °C, modification time: 20.3 h, impregnation ratio of HNO3 to MFBC: 10 mL/1 g, calcination time: 2 h, and calcination temperature: 716 °C. Moreover, surface roughness of the MFBC was found to increase obviously after the modification by FESEM and HRTEM analysis, and the total pore volume and specific surface area increased by 0.8 and 1.2 times, respectively. The PNP equilibrium adsorption capacity of MFBC was found to be 156.9 mg g−1 at 328 K, which highlights its potential application in wastewater treatment.

•We adopt graphene oxide (GO)-assisted ethanol reflux extraction (GERE) to extract flavonoids from Radix scutellaria.•GO can change the pH of the solution and improve the yields of total flavonoids and baicalein.•GO can catalyze the hydrolysis of baicalin to baicalein.•The yields of total flavonoids and baicalein by GERE reached 24.95% and 0.38%.A new method, graphene oxide (GO)-assisted ethanol reflux extraction (GERE) was investigated to extract total flavonoids from Radix scutellaria and accelerate the hydrolysis of baicalin (BG) to baicalein (B), simultaneously. The parameters of GERE were optimized by the single factor experiments, the optimal conditions were 1.1 mg GO/g dry raw material, ethanol 60% (v/v), ratio of liquid to solid 15 (mL/g) at 70 °C for 6 h. Under optimized conditions, the yields of total flavonoids and baicalein by GERE reached 24.95% and 0.38%, about 9.72% and 375% higher than single ethanol reflux extraction (ERE), respectively. SEM results revealed that after treated with GO, the Radix scutellaria surface appeared cracks, ravines and small holes. The structural disruption of wall reduces the mass transfer resistance and accelerates the leaching of flavonoids by ethanol solvent. XRD and FTIR results showed that GO reduced the crystallinity and the grain sizes of the Radix scutellaria cell, changed the internal structures of cellulose as well as cellulose accessibility, and improved the hydrolysis efficiency. HPLC results revealed that the content of baicalein in extract by GERE was significantly higher than that by ERE, which means that GO can catalyze the hydrolysis of baicalin to baicalein. The high yields of total flavonoids and baicalein can be related to the catalytic activity of GO, which can lead to the destruction of the cell wall, the reduction of the crystallinity and the grain sizes of cellulose. Thus, it was indicated that GERE method could be an alternative method for natural compounds extraction in industry.