Treatment of water contaminated by cadmium using low-cost and eco-friendly alginate/Moroccan clay composite beads

This study aims to investigate the batch mode adsorption of Cd(II) from an aqueous solution using two adsorbents: raw clay without any treatment (NC) and clay composite beads (CCB). The adsorbents before and after adsorption were characterized using several techniques such as X-ray fluorescence, X-ray diffraction, Fourier-transform infrared, scanning electron microscopy, energy-dispersive X-ray, thermogravimetric analysis, differential thermal analysis and zeta potential. The influence of the experimental parameters of adsorption such as mass, pH, concentration, contact time, and temperature were studied to optimize them. The results of the kinetic study suggest that the adsorption of Cd(II) by NC and CCB can be explained by the pseudo-second-order kinetic model. The time after which the adsorption reaction does not evolve was 120 min for both adsor-bents. The Langmuir isotherm model was found to be the most adequate for Cd(II) adsorption, with maximum adsorption capacities of 42.97 and 100.8 mg·g –1 for NC and CCB, respectively. The thermodynamic parameters indicated that the adsorption mechanism of Cd(II) on the surface of NC and CCB was endothermic, spontaneous, and favorable with a random distribution of Cd(II) ions at the solid/liquid interface. The regeneration study showed that NC and CCB are recyclable with. These findings suggest that NC and CCB could be used as effective and environmentally friendly adsorbents for treating heavy metal contamination in effluents.