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SnO2 nanoparticles were first synthesized using a grape extract media, then characterized by XRD, FE-SEM, TEM, BET, and DLS techniques, and finally used as an efficient adsorbent for the removal of Pb2+ and Cd2+ ions from wastewater. The prepared sample had a tetragonal phase with an average crystallite size of 41 nm (XRD analysis), a specific surface area of 47.08 m2.g-1 (BET method)/46.25 m2.g-1 (BJH method), and a pore diameter of 6.49 nm (BJH method). The best conditions for adsorbing were a 30 ppm concentration of metal ions, ambient temperature, pH of 6, and 0.025 g of an adsorbent. The maximum adsorption for Pb and Cd ions was 97 and 93%, respectively. The Elovich model was matched as the most suitable kinetic model, indicating that the adsorption mechanism is chemical adsorption. The negative values of ΔG (Pb: -6.38 kJ.mol-1; Cd: -4.16 kJ.mol-1) represent the spontaneousness of the adsorption process. The negative values of the parameters ΔH (Pb: -63.0 kJ.mol-1; Cd: -42.95 kJ.mol-1) and ΔS (Pb: -188.8 J.mol-1; Cd: -128.4 J.mol-1) represent the exothermic nature of the adsorption.

A simple method was applied to construct Ni-doped CaTiO3 nano-powders from commercial CaCO3 and TiO2, characterized by XRD, FE-SEM, and FT-IR. The sample was composed of small grains with an average size of 78 nm. This method could be a useful, inexpensive, and efficient tool for the preparation of Ni-doped CaTiO3 nano-powders. The prepared sample was used for the removal of Cd2+ from water media. Results indicated that Cd2+ removal by Ni-doped CaTiO3 nano-powders was very efficient (100% removal yield) when the pH was adjusted to 4.5, the catalyst dosage amounted to 0.05 g, and the Cd2+ solution concentration was 60 mg.L-1. A pseudo-second-order kinetic model described the kinetics of Cd2+ removal.