Efficient adsorbent graphene oxide (GO) and its derivative, i.e., thiol-functionalized graphene oxide (GO-SH), was used for the removal of noxious Pb(II) ion from the aqueous phase. Different amounts, i.e., 60, 80, and 100 mg of cysteamine, were used as functionalizing agent to functionalize the GO with thiol group; hence, three different nanocomposites, i.e., GO-SH 1 , GO-SH 2 , and GO-SH 3 were prepared from the different amount of the cysteamine. The developed nanocomposites were characterized using various analytical techniques such as Fourier transform infrared spectroscopy, scanning electron microscopy, and X-ray diffraction analysis. The whole removal and adsorption process was well illustrated and investigated. The impact of influential factors including initial concentration, pH, contact time, temperature, and concentrations cysteamine on the adsorption properties of Pb(II) from aqueous solution was well elucidated and optimized. The obtained equilibrium results were inserted in various adsorption isotherm models such as Langmuir (liner types I, II, III, and IV), Freundlich, Temkin, Helsey, and Dubinin-Radushkevich isotherms, it was found that the Langmuir (type I) model demonstrated was well fitted and in good agreement with the maximum adsorption of Pb(II) ion from aqueous solution. Thermodynamic functions, such as ∆G°, ∆H°, and ∆S° were calculated and it reveals that the adsorption of Pb(II) ion on all the surfaces was spontaneous and endothermic in nature.
