Performance evaluation of a novel rGO-Fe0/Fe3O4-PEI nanocomposite for lead and cadmium removal from aqueous solutions

The capability of a novel rGO-Fe-0/Fe3O4-PEI adsorbent to remove heavy metals from aqueous solutions was investigated. Graphene oxide (GO) was synthesized by Hummers' and Offenman's method. The GO modified by magnetic iron oxide (rGO-Fe-0/Fe3O4), then PEI was used as chelator to modify the surface of rGO-Fe-0/Fe3O4. The rGO-Fe-0/Fe3O4-PEI nanocomposite was characterized by FE-SEM, TEM, EDS, FT-IR, VSM, BET, and TGA. Then, the synthesized adsorbent was used for the removal of lead and cadmium from aqueous solutions. The effects of various experimental parameters such as solution pH, adsorbent dosage, contact time, temperature, and metal ion concentration were evaluated. The optimum conditions determined as 5 mg of the adsorbent, 2 mg.L-1 of each metal at pH = 6, and 60 min of contact time provided a high adsorption capacity. The maximum adsorption capacities (Qm) were 60.24 and 54.47 mg.g(-1) for lead and cadmium ions, respectively. The isotherm and kinetic evaluation revealed a good fit to the Langmuir and pseudo-second-order model, respectively. The thermodynamic results revealed that the adsorption of metal ions onto the adsorbent was spontaneous and endothermic in nature. Reusability, desorption, stability, competitive adsorption, and solution ionic strength studies were also performed on the synthesized adsorbent. The study of reusability revealed that the synthesized adsorbent can be successfully reused following 4 cycles of adsorption/desorption. Accordingly, rGO-Fe-0/Fe3O4-PEI can be utilized as a potential adsorbent for lead and cadmium removal from aqueous solutions. (C) 2020 Elsevier B.V. All rights reserved.