Enhanced adsorptive removal of cationic dyes from aqueous solution by chemically treated carob shells

The aim of this work was to study the removal of methylene blue (MB) and malachite green (MG) from aqueous solution by raw and chemically treated carob shells as low cost biosorbent. Samples were characterized by Boehm titration, elemental analysis (CHNOS), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and the point of zero charge (pH(PZC)). The experimental results show that the biosorption yield increases with an increase in the biosorbent dosage. Maximum biosorption capacity occurred at basic pH medium. Kinetic data were analyzed using pseudo-first and pseudo-second kinetic models. Equilibrium data fit Langmuir model with maximum monolayer biosorption capacities of 217.15, 232.44 and 342.21 mg/g for MB and 233.40, 291.74 and 327.89 mg/g in the case of MG, respectively, for Raw-carb, HCl-carb and NaOH-carb. The temperature doesn't have much influence on the biosorption performance. The NaOH treated carob shells was considered to be strongly efficient for the removal of MB and MG from aqueous solutions.