Comparative assessment of methylene blue biosorption using coffee husks and corn cobs: towards the elaboration of a lignocellulosic-based amperometric sensor

The ability of coffee husks (CHs) and corn cobs (CCs) as biosorbents for methylene blue (MB) was investigated in batch mode. The energy dispersive X-ray spectroscopy was used for the determination of elemental composition of both biosorbents. Sorption experiments were carried out as a function of temperature, pH and MB initial concentration. Adsorption capacities of both materials significantly increased with the MB initial concentration. Among the various kinetic and adsorption isotherm models, the experimental adsorption data were best fitted in pseudo-second-order kinetic model and Langmuir isotherm model. The maximum adsorption capacities at room temperature were found to be 79.60 and 73.16 mg g(-1) for CHs and CCs respectively. Moreover, the great affinity of MB towards CHs led to deep electrochemical experiments shown that CHs can be used as prominent modifier for a carbon paste electrode (CPE). The linear dynamic range of MB was found within the concentration range of 1-125 mu mol/L with a detection limit (3 sigma) of 3 mu M. The elaborated sensor was successfully applied for the determination of adsorption capacities of CHs placed into a column for MB biosorption in river water, suggesting that CH-CPE could be an efficient tool for MB detection in environmental samples.