Synthesis and characterization of rGO/Co3O4 composite as nanoadsorbent for Rhodamine 6G dye removal

In this paper, Co3O4 nanoparticles are loaded onto rGO sheet by the hydrothermal method and used as a surface to absorb the cationic dye (Rhodamine 6G). They are characterized using X-ray diffraction, field emission scanning electron microscopy, transition electronic microscopy, UV-Vis spectroscopy, Fourier transform infrared spectroscopy, energy dispersion X-ray, and zeta potential. The results indicated that there was heterogeneous distribution of Co3O4 nanoparticles (45 nm in size) on rGO sheets. The rGO/Co3O4 nanocomposite showed adsorption capacity with 122.4 mg/g for Rh. 6G dye. Additionally, the factors affecting the process of adsorption that include equilibrium time, temperature, pH solution, ionic intensity, and adsorbent dose were studied. The equilibrium removal efficiency was studied using Langmuir, Freundlich, and Temkin isotherm models. The kinetic data were analyzed with two different kinetic models and pseudo-first-order kinetic model was found to be the best model for our adsorption experiment. The thermodynamic parameters including Gibbs free energy (Delta G degrees), standard enthalpy change (Delta H degrees), and standard entropy change (Delta S degrees) were calculated for the adsorption process.