A New Highly Efficient Algerian Clay for the Removal of Heavy Metals of Cu(II) and Pb(II) from Aqueous Solutions: Characterization, Fractal, Kinetics, and Isotherm Analysis

A physicochemical characterization, the irregularity of the surface quantified by the fractal dimension (D_S), and the adsorption of copper (Cu(II)) and lead (Pb(II)) of a kaolin clay from aqueous solutions were studied. In addition, the effects of temperature, contact time, pH of solution, and clay mass on copper Cu(II) and Pb(II) adsorption were investigated. In this work, X-ray fluorescence, X-ray diffraction, and Fourier transform infrared spectroscopy were applied to study the composition and structure of the clay studied. The Brunauer–Emmett–Teller theory and the t-plot method were used to calculate the specific surface and porosity, respectively. The fractal analysis showed that the material has an irregular surface, with a very complex pore structure. This material has a very high adsorption capacity, which exceeds 97.5% and 99.95% for Cu(II) an Pb(II), respectively, for all concentrations under normal conditions of pH and temperature (pH7, T = 25 °C). The maximum adsorption capacity calculated by the Langmuir model was 52.63 mg g⁻¹ for copper (Cu). For lead (Pb) ions, the maximum capacity was 57.30 mg g⁻¹. The adsorption process was rapid, as equilibrium was achieved within 10 min for copper at 25 and 50 mg L⁻¹ and within 30 min at 100 mg L⁻¹. For lead (Pb) ions, equilibrium was achieved within the first minute at all concentrations. The kaolin clay has a better affinity for Pb(II) than Cu(II). The Temkin model showed better correlation with the experimental data for this material. The kinetic study demonstrated that Pb(II) and Cu(II) adsorption on kaolin was in a good accordance with the pseudo-second-order kinetic model.