Abstract

This study focuses on the synthesis of pure and Fe-substituted CuAl₂O₄ nanospinels using the co-precipitation method at elevated temperatures. Various analytical techniques, including scanning electron microscopy, transmission electron microscopy, FT-IR spectroscopy, and X-ray diffraction, were employed to confirm the formation of the nanospinels. The efficiency of the prepared nanospinels in adsorbing Pb²⁺ ions from aqueous solutions was evaluated. A Response Surface Methodology (RSM) based on a Central Composite Design (CCD) was developed to optimize three independent variables: pH, contact time, and initial concentration. A quadratic model was constructed to predict the adsorption behavior, and the model predictions closely matched the experimental values, indicating high reliability. The adsorption isotherm and kinetic studies suggest multilayer adsorption governed by the Langmuir isotherm, with physisorption as the dominant mechanism, although the kinetic data fitted well with the pseudo-second-order kinetic model. The spontaneity of the adsorption process increased with rising temperature and was found to be exothermic in nature. The adsorbents exhibited preferential uptake of Pb²⁺ ions, though the process was not selective. The adsorption mechanism of Pb²⁺ ions onto CuAl₂O₄ and CuAlFeO₄ nanospinels was elucidated as electrostatic attraction, which was confirmed by XPS analysis. The present work highlights the potential application of CuAl₂O₄ and CuAlFeO₄ nanospinels for the adsorption of Pb²⁺ ions.