الفهرس 
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Abstract
Heavy metal pollution is a serious environmental problem that can be cured by different adsorbents. Herein, a new hydroxyapatite / graphene oxide nanocomposite (HAp/GO) material was synthesized from waste eggshell as a green and eco-friendly adsorbent for the effective removal of heavy metals (e.g., Cd, Pb, Cr, Ni, Co) from wastewaters. Nano-structured HAp was synthesized by calcination of waste eggshell followed by hydrothermal treatment in the presence of phosphate solution. However, GO was synthesized using the Hummar’s method. The HAp/GO nanocomposite was synthesized from the HAp and GO precursors by ultrasonic treatment. The morphology, composition, crystal structure, functionality and stability of the synthesized sorbent were evaluated using Fourier transform infrared spectrophotometry (FTIR), Raman spectrometry, high resolution transmission electron microscopy (HR-TEM), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), X-ray diffraction (XRD) and N2-BET (Barrett–Emmett–Teller) surface area measurement techniques. Inductively Coupled Plasma Mass Spectroscopy (ICP-MS) was used to monitor the equilibrium concentrations of the investigated metal ions. The effects of the initial concentration of heavy metals, the dosage of HAp/GO adsorbent, working temperature, and the solution pH on the adsorption capacity was investigated. The synthesized HAp/GO was adopted to achieve superior simultaneous removal efficiencies (≥ 90 %) for (Cd, Pb, Cr, Ni, Co) metal ions in a given polluted sample