Removal of Pb(II) from Aqueous Solutions Using Graphene-Immobilized Nickel Oxide Composites

Considering lead’s toxicity and its characteristics as a serious environmental pollutant, to protect the human population’s health and the ecosystem it is necessary to stop this heavy metal from entering water resources and the environment through industrial wastewater. Therefore, the present study was carried out to manage lead elimination from aqueous solutions using NiO nanocomposites immobilized on graphene. To determine the effective factors in the elimination process, some parameters including contact time (20, 30, 15, 5, 10, 3 min), adsorbent dosage (0.1, 0.05, 0.2, 0.01g), initial concentration of the lead solution (5, 10, 20, 50, 100, 200, 300, 800, 1000 mg/L) and pH (2, 4, 5, 6, 7) were investigated at room temperature, 40 ˚C and 55 ˚C. Based on the results, the amount of lead eliminated by graphene-immobilized nickel oxide nanoparticles reached its maximum value under the optimum conditions of 20 min contact time, 0.05g adsorbent, 5ppm initial concentration, and 55 ˚C temperature. In addition, the experimental data were analyzed using Langmuir, Freundlich, and Dubinin-Radushkevich isotherms of the adsorption process and the results indicated maximum compliance with the Langmuir isotherm, with a maximum adsorption capacity of 2000 mg/g. These findings show that lead absorption is an endothermic reaction. The graphene/NiO magnetic nanocomposite made in this way has many pores and a high specific area (196.5 m2/g), which makes it an ideal adsorbent for removing lead(II) ions from aqueous solution. The maximum absorption capacity obtained from the said adsorbent was 2000 mg/g, which is much higher than other common adsorbents. Among the advantages of this method, we can point out the very high absorption capacity, the simplicity of separating the adsorbent from the solution, and the fast duration of the absorption equilibrium (up to 20 min).