Influence of ionic strength on methylene blue removal by sorption from synthetic aqueous solution using almond peel as a sorbent material: experimental and modelling studies

In the present work, the influence of ionic strength on kinetics and equilibrium of methylene blue sorption from synthetic aqueous solutions, in single dye solutions, using almond peel as a sorbent material has been investigated in batch conditions. NaCl concentration played a certain part in sorption phenomenon: the methylene blue sorption increased as NaCl concentration increased. The pseudo second-order model was selected to describe the experimental data of methylene blue sorption kinetics. The results showed that the process follows a pseudo second - order kinetics. Equilibrium data were mathematically fitted to Langmuir equation which gave an acceptable fit over the whole equilibrium dye concentrations range. A high dye sorption was observed by this sorbent material: a maximum sorption capacity about 121.80 - 138.31 mg/g was achieved depending on NaCl concentration tested. Under these experimental conditions, the analysis of mechanistic steps involved in the sorption process confirms that methylene blue sorption process is particle-diffusion-controlled, with some predominance of some external mass transfer at the initial stages.