Adsorption of Copper (II) Ions on a Montmorillonite Clay and its Application as Heterogeneous Catalyst for Knoevenagel Condensation Reaction

In the present study, a simplest and most effective method was applied to removal of Cu^2+ ions from an aqueous solution using Montmorillonite clay, nontoxic and abundantly available as an adsorbent. The used adsorbent was characterized using X-ray diffraction (XRD), the X-ray fluorescence spectrometry, Fourier Transform Infrared Spectroscopy (FT-IR) and scanning electron microscope (SEM) coupled with EDX analysis. Adsorption experiments were conducted under various conditions,.i.e., contact time , initial concentration, pH of Cu(II) ions solution, adsorbent mass, and particle size . The results proved that the adsorption of Cu(II) ions by Montmorillonite clay was favorable at pH=5.5 with an extraction yield of 85% after 30 min contact. The equilibrium isotherm data were analyzed using the Langmuir and Freundlich equations. In all cases, the adsorption process fitted the second-order kinetics well, and the isotherm equation due to Freundlich showed good fits with the experimental data. In order to value our Cu-Montmorillonite clay (Cu-MC) support, we thought of applying it as recyclable heterogeneous catalyst for the condensation of Knoevenagel. The model reaction was carried out at room temperature, using a quantity of 0.5 mg of catalyst and a volume of 2ml of ethanol, the reaction yield was excellent (87%). The recyclable solid catalyst was effective for five successive cycles, indicating that this clay is a potentially eco-friendly heterogeneous catalyst.