Abstract:

Using Ningxia agricultural waste wolfberry stems as raw materials，phosphoric acid-activated carbon（P-AC），potassium hydroxide-activated carbon（K-AC） and phosphoric acid-potassium hydroxide-activated carbon（P-K-AC） were prepared with different activators.The specific surface area test（BET），X-ray diffraction（XRD），infrared spectroscopy（FT-IR） and scanning electron microscopy（SEM） were used to analyze the pore structure and surface characteristics of activated carbon，and the removal effect of activated carbon on methylene blue（MB） in aqueous solution was explored.The results showed that P-K-AC had a larger specific surface area（1 519.84 m²/g） and total pore volume（0.81 cm³/g） than P-AC and K-AC.The average pore diameters of P-AC，K-AC and P-K-AC were 5.28，2.58 and 1.99 nm，respectively.P-K-AC was mainly microporous，while K-AC and P-AC were mesoporous.The surfaces of the three kinds of activated carbons were distributed with rich oxygen-containing functional groups and a large amount of amorphous carbon，which provided active sites for adsorption of MB.At 25 ℃，10 mg of P-AC，K-AC and P/K-AC were added to 50 mL of MB solution with mass concentration of 100 mg/L for MB adsorption experiment，respectively.The results showed that P-K-AC had the best adsorption effect，with the adsorption rate of 95%，the adsorption capacity of 480.81 mg/g，followed by K-AC（the adsorption capacity of 352.26 mg/g），and the adsorption capacity of P-AC was the smallest（225.01 mg/g）.The adsorption process of P-AC，K-AC and P-K-AC for MB was conformed to the pseudo second order kinetic model，intraparticle diffusion model and Langmuir isothermal adsorption model.

Key words: wolfberry stem, activated carbon, potassium hydroxide, adsorption, methylene blue