Adsorption behavior of methylene blue on glycerol based carbon materials

Abstract

A glycerol based carbon was synthesized by partial carbonization of glycerol using concentrated H2SO4 in the molar ratio 1:4. The carbonized material was further treated at 120 degrees C and 350 degrees C to obtain the carbons GBC-120 and GBC-350 respectively. The samples were characterized by XRD, ir, thermal analysis (TG-DTG-DTA), pzc measurements; SEM and BET surface area analysis. The TGA showed a gradual weight loss up to about 800 degrees C. The adsorption studies were carried out using methylene blue as a model adsorbate. The BET surface area of GBC-120 and GBC-350 were determined to be 21 and 464 m sup(2) g sup(-1). The GBC-120 gave maximum adsorption capacity with nearly 100 percent dye removal efficiency using 8 10 milligrams of the adsorbent powder, when the dye concentration was 25 μg mL sup(-1). It showed Type I adsorption isotherm profile at lower concentration range and the data could be readily fitted into Langmuir adsorption model. At higher concentration the adsorption data showed a better fit for Frumkin adsorption model. The adsorption generally increased with temperature and showed a favorable free energy change. The GBC-350 showed comparatively less adsorption and but the data could also be fitted in Langmuir adsorption profile. Investigation of adsorption kinetics revealed better fit with pseudo second order kinetic model for both GBC-120 and GBC-350. GBC-120 due to presence of SO3H surface functionality showed a high adsorption capacity ∼1050 mg g sup(-1) which is significantly higher than the literature values.