Analytical study on lead elimination by anionic clays: Characterization, adsorption kinetics, isotherm, thermodynamic, mechanism and adsorption

The co-precipitation method synthesized the synthetic anionicMg–Al and Ni-Al clays with three molar ratios (Mg/Al, Ni/Al). The samples were characterized by powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). No other crys talline phases were detected in the powder XRD patterns of the co-precipitated samples. The infrared spectra obtained all the functional groups that characterize these two types of anionic clays. SEM micrographs indicate the presence of particles and aggregates. The particles, or aggregates, are in the form of plates, supported by particles of acceptable sizes. The optimal pH for maximum lead adsorption is about 6.5 for both clays. The optimal adsorbent masses for the maximum percentages of lead removal are 0.2 g for Mg3AlCO3 and 0.25 g for Ni3AlCO3. The Mg3AlCO3 has a maximum adsorption capacity of lead, where qm=73.42 mg g-1. The adsorbed amount increases with increasing temperature for both types of clays s tudied. The equilibrium time of Pb2+ adsorption is reached after 5 min for both clays. The mos t appropriate models to describe the experimental data of adsorption kinetics and isotherms are pseudo-second-order and Langmuir. The detection limit (LOD) was 0.272 mg L-1. The linearity range was 1 to 5 mg L-1; the correlation coefficient in this range was 0.9997.