Montmorillonite clay modified with iron oxide (MtMIO)was prepared for use as an adsorbent of methylene blue
dye. Structural characterization of MtMIO was performed by field-emission scanning electron microscopy,
energy-dispersive spectroscopy, surface area measurements, zeta potential analysis and Fourier transform infra-red spectroscopy. Batch experiments were carried out under different conditions of initial dye concentration,
contact time and temperature to investigate the adsorption of methylene blue onto MtMIO. Adsorption iso-thermswere experimentally determined and the Freundlich and Langmuir models were used tofit the data, bet-ter results being obtained for the latter with a maximum adsorption capacity of 71.12 mg g
−1
at 333 K.
Thermodynamic parameters, such as standard enthalpy, standard entropy and standard free energy changes
were determined, indicating an endothermic and non-spontaneous process. Also, pseudo-first-order and
pseudo-second-order kinetic models were applied, and the experimental datafitted the pseudo-second order
model. The activation energy of +19.32 kJ mol−1
was determined using the Arrhenius equation