This study evaluated the performance of an Unmodified Ugwuoba-montmorillonite Clay (UUC) and the Acid Modified Ugwuoba-montmorillonite Clay (AMUC) of Nigerian origin as low-cost materials for attenuation of Methylene Blue (MB). Batch sorption methodology was applied in adsorption and desorption studies. AMUC was found to have higher adsorption of MB than UUC under all experimental conditions. Optimum experimental conditions were achieved at pH 8.0, adsorbent particle size 100 μm, MB concentration 200 mg/L and contact time of 60 and 90 min for AMUC and UUC, respectively. Equilibrium isotherm analysis was performed by the application of the Langmuir, Freundlich, Flory-Huggins, Tempkin, Dubinin-Radushkevich and Scatchard isotherm models. The Langmuir isotherm was found to be applicable (R2 of 0.999) in the sorption of MB on UUC while the Freundlich gave the best fit (R2 of 0.990) for AMUC. Kinetic analysis was evaluated by the Pseudo First Order (PFO), Pseudo Second Order (PSO), Elovich, Bangham, Intraparticle diffusion and liquid film diffusion models. The PSO model was found to be applicable in the kinetics with an initial sorption rate of 0.647 and 1.477mg g-1 min-1 for the respective adsorbents. Thermodynamics revealed a spontaneous, feasible and exothermic adsorption process, while desorption studies showed a physical adsorption mechanism.
Keywords: Acid-modification, desorption, dye, thermodynamics, water treatment