High specific area activated carbon derived from chitosan hydrogel coated tea saponin: one-step preparation and efficient removal of methylene blue

Abstract A novel activated carbon (CCH-TS) derived from chitosan hydrogel (CH) coated tea saponin (TS) was prepared to investigate its removal performance for methylene blue (MB). CCH-TS was characterized by thermogravimetric analysis, field-emission scanning electron microscope, fourier transform infrared spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Brunauer-Emmett-Teller, and zeta potential analysis. The results showed that CCH-TS had a high specific area 3504 m2/g with a large pore volume of 6.03 m3/g. In the batch mode adsorption experiments, the effects of initial pH values, adsorbent concentration, initial MB concentration and contact time, and adsorption temperature on the adsorption performance of CCH-TS for MB were studied. The experimental results were fitted by pseudo-first-order kinetic, pseudo-second-order kinetic and intra-particle diffusion models. Furthermore, Langmuir, Freundlich and Temkin isotherms were employed to analyze the equilibrium adsorption data. It was found that these data were fitted to Langmuir isotherm best with a maximum adsorption capacity of 604.10 mg/g, while pseudo-second-order kinetic model could describe the adsorption process more accurately. Thermodynamic analysis implied that the adsorption process was spontaneous and exothermic. Therefore, a facile one-step route to preparation of activated carbon with a high specific area and efficient dye removal ability was achieved.