Adsorption of Methylene Blue onto Environmentally Friendly Lignocellulosic Material Obtained from Mature Coltsfoot (Tussilago farfara) Leaves

The present study investigates the potential of a new lignocellulosic adsorbent material obtained from mature coltsfoot (<i>Tussilago farfara</i>) leaves for the removal of methylene blue from aqueous solutions. The material was obtained after minimal processing of the leaves, without chemical or thermal treatment. The material was first characterized using several specific techniques (FTIR, color analysis). Then, the mechanism of the adsorption process was investigated through studies related to adsorption equilibrium, kinetics, and thermodynamics. The adsorption process is described by the Sips isotherm and the general kinetic model, while the thermodynamic parameters suggest that physical adsorption is the primary mechanism responsible for dye retention. The Taguchi method was used to optimize the adsorption conditions and to identify the most influential controllable factor. ANOVA was used to calculate the percentage contribution of each controllable factor to the dye removal efficiency. pH had the greatest influence on the process (87.78%), while temperature had the least effect (0.16%). The maximum adsorption capacity determined was 278.1 mg/g, being higher than other similar adsorbents. All the results show that coltsfoot (<i>Tussilago farfara</i>) leaves are a very cheap, environmentally friendly, and effective adsorbent for the removal of methylene blue dye from aqueous solutions.