Thermodynamic and kinetic study of the removal of Cu2+ and Pb2+ ions from aqueous solution using Fe7S8 nanomaterial

• Published in: Microchemical journal 2018-07, Vol.140, p.80-86
• Main Authors: Cantu, Jesus, Gonzalez, Diego F., Cantu, Yvette, Eubanks, T.M., Parsons, J.G.
• Format: Article
• Language: English
• ISSN: 0026-265X; 1095-9149
• DOI: 10.1016/j.microc.2018.04.003

In the present study, pyrrhotite (Fe7S8) was investigated for the removal of Pb2+ and Cu2+ ions from aqueous solution. The Fe7S8 material was prepared through a solvothermal method and was characterized using XRD. The average particle size for the nanomaterial was determined to be 29.86±0.87nm using XRD analysis and Scherrer's equation. Batch studies were performed to investigate the effects of pH, time, temperature, interfering ions, and the binding capacity of Pb2+ and Cu2+ ions to the Fe7S8 nanomaterial. During the pH profile studies, the optimum pH for the binding of Pb2+ and Cu2+ was determined to be pH5 for both cations. Isotherm studies were conducted from which the thermodynamics and binding capacities for both Cu2+ and Pb2+ were determined. The binding capacity for Pb2+ and Cu2+ binding to the Fe7S8 were determined to be 0.039 and 0.102mmol/g, respectively at 25°C. The thermodynamic parameters indicated a ∆G for the sorption of Pb2+ ranged from 5.07kJ/mol to −2.45kJ/mol indicating a non-spontaneous process was occurring. Whereas, the ∆G for Cu2+ ion binding ranged from 9.78kJ/mol to −11.23kJ/mol indicating a spontaneous process at higher temperatures. The enthalpy indicated an endothermic reaction was occurring for the binding of Pb2+ and Cu2+ to the Fe7S8 nanomaterial with ∆H values of 55.8kJ/mol and 153.5kJ/mol, respectively. Furthermore, the ∆S values for the reactions were positive indicating an increase in the entropy of the system after metal ion binding. Activation energy studies indicated the binding for both Pb2+ and Cu2+ occurred through chemisorption. •A Fe7S8 nanomaterial was synthesized solvothermally using FeCl36H2O in a mixture of ethylene glycol and water.•The binding of both Pb2+ and Cu2+ ions from aqueous solution to the Fe7S8 nonmaterial were tested.•The Binding parameters investigated included pH, kinetics (time dependency), and thermodynamics.•Hard cations showed little to no effect on both Pb2+ and Cu2+ ions to the Fe7S8 nanomaterial.