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INFLUENCE OF SOME EXPERIMENTAL PARAMETERS ON METHYLENE BLUE SORPTION KINETICS FROM SYNTHETIQUE AQUEOUS SOLUTIONS USING THISTLE STALKS AS A LOW-COST SORBENT: EXPERIMENTAL AND MODELLING STUDIES

The ability of thistle stalks, as an inexpensive sorbent for the removal of methylene blue (basic dye) from synthetic aqueous solutions, has been studied in batch conditions. The influence of some parameters such as: contact time, initial dye concentration, sorbent dose and agitation speed on dye sorption kinetics, has been studied. Dye uptake was time contact, initial dye concentration, sorbent dose and agitation speed dependent. The main parameters that play an important part in removal phenomenon were initial cadmium concentration and sorbent mass. Agitation speed showed a restricted effect on the dye removal kinetics. Two simplified kinetic models including a first-order and a pseudo second-order rate equation were selected to describe the dye sorption kinetics. Methylene blue sorption process followed a pseudo second – order rate kinetics. A multiple-stage diffusion of methylene blue onto thistle stalks particles was observed indicating that intraparticle diffusion was not a fully operative mechanism for this system and reflects some degree of boundary layer control. From these first results obtained under the investigated experimental conditions, the thistle stalks tested were shown to be promising sorbent material for removal/sorption of methylene blue from synthetic aqueous solution.