Humic acid as a green-sorbent was synthesized from marine sediments. While kaolin was modified to nano-zeolite NaX. Different tools such as FT-IR, SEM, EDX and XRD were applied to confirm the characteristics of the generated green-sorbents. Different factors such as pH, contact time, sorbent dosage, initial metal ion concentration, temperature and interfering ions were carefully examined and used to optimize the batch adsorption process for Cd2+ and Pb2+. A small dose of nano-zeolite of 100 mg was required to attain the maximum adsorption of Pb2+ at pH about 7, shacking time at 60 min and Pb2+ concentration at 30 ppm. Also, the maximum sorption capacity of Cd2+ ions on nano-zeolite was achieved in a neutral medium and very short contact time implying the economic feasibility of the adsorption process. In the case of humic acid, the maximum removal capacity for Pb2+ and Cd2+ was operated at acidic medium and shacking time was 40 min. Metal ions remediation results were evaluated by some adsorption isotherm models at different temperatures. The kinetic and thermodynamic variables were also computed. The data fitted very well with the linear Langmuir and the pseudo-second-order model implying a favourable adsorption process. The sorption of Cd2+ and Pb2+ was regulated by both external mass transfer and intraparticle diffusion steps over the whole range of concentrations, as shown by the results. The metal ions removal percentage from four real water samples by green sorbents were applied and provides good evidence of two sorbents as promising eco-sorbent for removal of heavy metal ions.

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Nano-ZnO was synthesized by the reduction of Zn (CH3COO)2.2H2O salt using the extract of Ocimum tenuiflorum leaves. The generated ZnO NPs were characterized by FT-IR, XRD, SEM, and EDX techniques. FT-IR results approved the characteristic peaks, the formation of ZnO bonds, and the morphology changes after the adsorption of Cd2+ and Pb2+ from solutions. The outlined data of the XRD pointed to the formation of a hexagonal wurtzite structure. SEM images showed the spherical nature of the synthesized particles with an average diameter of 19 nm. Moreover, the best conditions for the adsorption of Cd2+ and Pb2+ by ZnO NPs were evaluated and fitted to isotherm and kinetic models. Short contact time of ~ 20 min and a small sorbent dosage of 40 mg were sufficient conditions for attaining maximum Pb2+ adsorption capacity. Based on the modeling parameters, the adsorption follows pseudo-second-order kinetics where ZnO and metal ions are involved in the rate-determining step. Two important applications were thoroughly studied. The nanoparticles significantly removed Pb2+ and Cd2+ contaminants from real environmental water samples collected from different locations in Egypt. Additionally, the cytotoxic activity results provided perfect evidence for the higher efficacy of the synthesized ZnO NPs as an anticancer agent against Panc-1, PC-3, and CACO-2 cell lines with IC50 of 1.70, 3.67, and 5.70 μgml−1, respectively, compared to cisplatin (IC50 = 3.57, 5.09, and 7.75 μgml−1). Furthermore, a low cytotoxic effect was observed on the normal human lung cell line (MRC-5, IC50 = 22.40 μgml−1). The data can be used as a preliminary study for anticancer drug design after further clinical investigations. Graphical Abstract