Removal of orange G via environmentally friendly GO@Fe3O4-COOH@NH2-MIL-101(Fe) nanocomposite

Attractive environmentally friendly magnetic metal-organic framework (MOF) nanocomposite GO@Fe3O4-COOH@NH2-MIL-101(Fe) was synthesized by a solvothermal method and characterized by X-ray diffraction, Fourier transform infrared, scanning electron microscopy, Brunauer-Emmett-Teller, and vibrating sample magnetometer, and used as an effective adsorbent for the removal of orange G from aqueous solution. The various operating parameters that effect the adsorption process, such as adsorbent dosage (0.01-0.2 g), pH (1.0-10.0), initial concentration (50-400 mg L-1), and temperature (298.15-318.15 K) were studied. The percent removal of orange G increases with the increment of the adsorbent dosage and decrease of the initial concentration, and the optimum pH is 6.0. The Redlich-Peterson model can be favorably applied to describe the adsorption equilibrium data, indicating that the surfaces of GO@Fe3O4-COOH@NH2-MIL-101(Fe) nanocomposite for the orange G adsorption are made up of homogeneous adsorption patches. The adsorption kinetics indicate that the adsorption process of GO@Fe3O4-COOH@NH2-MIL-101(Fe) toward orange G obeys the pseudo-second-order model and the activation energy is 16.5 kJ mol(-1). Thermodynamic parameters, Delta H = 39.81 kJ mol(-1), Delta S = -46.80 J mol(-1) K-1, and Delta G < 0, exhibit that the adsorption is exothermic and spontaneous. The maximum adsorption capacity of orange G onto GO@Fe3O4-COOH@NH2-MIL-101(Fe) nanocomposite is 128.8 mg g(-1). Therefore, magnetic GO@Fe3O4-COOH@NH2-MIL-101(Fe) nanocomposite can be employed as an environmentally friendly and efficient adsorbent for the orange G removal from wastewater.