Abstract: Using walnut shells as raw materials, the modified walnut shell biochar was prepared by high temperature pyrolysis （500 ℃, 2 h）and NaOH modification treatment. The concentration of Rhodamine B was determined by UV-visible spectrophotometry. The effects of adsorption time, the dosage of modified walnut shell biochar and the initial mass concentration of Rhodamine B on the adsorption performance were analyzed. The adsorption mechanism of modified walnut shell biochar on Rhodamine B was investigated. The results showed that when the dosage of modified walnut shell biochar was 0.02 g, the volume of Rhodamine B solution was 20 mL, the initial mass concentration of Rhodamine B solution was 2.0 mg/L, and the adsorption time was 130 min,the removal rate of Rhodamine B was 94.65%, and the corresponding adsorption capacity was 1.893 1 mg/g. The adsorption process of Rhodamine B solution by NaOH-modified walnut shell biohar accorded with the quasi-second-order kinetic equation, and Langmuir adsorption isotherm model can describe the adsorption process accurately, indicating that the adsorption process was a single-layer adsorption with uniform surface and controlled by chemical adsorption.

Key words: modified walnut shell biochar, Rhodamine B, adsorption kinetics, NaOH