Adsorption of Cu(II) onto Fe(III)-Modified Montmorillonite - Kinetic, Isotherm, and Thermodynamic Studies

Abstract

Abstract Trace metal ions, such as Cu(II), in wastewater could pose serious health threats when not treated. This study employed adsorption using an Fe(III)-modified montmorillonite (Fe-MMT), an abundant mineral in the Philippines, to remove Cu(II) ions in synthetic wastewater. Scanning electron micrographs of the synthesized clay show showed its layered structure while elemental analysis confirmed the successful modification to Fe-MMT with high amounts of retained Fe in the clay. Batch adsorption was performed at varying adsorption time, initial Cu(II) concentration, and temperature, for which applicable models were then employed to understand the adsorption mechanism. Cu(II) adsorption showed a slow rate until the process reached equilibrium at 12 hrs corresponding to 85.86% removal. Adsorption of Cu(II) on Fe-MMT was found to agree with both the pseudo-first order and the liquid-film diffusion kinetic models. Isotherm modelling revealed that the process fitted well with the Langmuir model with theoretical adsorption capacity of Fe-MMT as 48.077 mg/g. On the other hand, Dubinin-Radushkevich isotherm suggests that the mechanism was via physisorption. From the thermodynamic modelling, it was obtained that the Cu(II) adsorption was an endothermic process which further translated to a ΔG°298 of 5,696.89 J/mol.