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@Fe 3 O 4 -COOH@NH 2 -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@Fe 3 O 4 -COOH@NH 2 -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@Fe 3 O 4 -COOH@NH 2 -MIL-101(Fe) toward orange G obeys the pseudo-second-order model and the activation energy is 16.5 kJ mol –1 . Thermodynamic parameters, ΔH = 39.81 kJ mol –1 , ΔS = –46.80 J mol –1 K –1 , and ΔG < 0, exhibit that the adsorption is exothermic and spontaneous. The maximum adsorption capacity of orange G onto GO@Fe 3 O 4 -COOH@NH 2 -MIL-101(Fe) nanocomposite is 128.8 mg g –1 . Therefore, magnetic GO@ Fe 3 O 4 -COOH@NH 2 -MIL-101(Fe) nanocomposite can be employed as an environmentally friendly and efficient adsorbent for the orange G removal from wastewater.