Removal of Methylene Blue dye from aqueous solutions by illite clay

In this study, adsorption of methylene blue (MB) dye on illite from aqueous solutions was investigated as a function of pH, electrolyte concentration and temperature. Illite clay was characterized using FTIR-ATR, BET, SEM, XRF and XRD instruments. Adsorption studies showed that adsorption process attained to equilibrium about 3 h and adsorbed amount of MB on illite increased with increasing pH, electrolyte concentration and temperature. Experimental data were analysed with Temkin, Dubinin-Radushkevich (DR), Freundlich and Langmiur isotherms and correlated reasonably well by Langmuir adsorption isotherm with highest R2 values. Then, Langmiur isotherm parameters (qm and K) were calculated. The value of maximum adsorption capacity (qm) was varied from 14.61·10–5to 31.63.10–5 mol·g–1 for different experimental conditions. The adsoption heat was calculated as 14.38 kJ·mol–1 for isosteric conditions (θ = 0.5). The positive and relatively low value of adsorption heat shows that adsorption process is an endothermic process and interaction between the dye and illite is a physical interaction. The values of RL, calculated dimensionless separation factor, showed that illite can be used for removal of MB from aqueous solutions.