Nonlinear and linear analysis of Direct Yellow 50 adsorption onto modified graphene oxide: kinetic, isotherm, and thermodynamic studies

The present work describes the removal of Direct Yellow 50 from an aqueous solution by graphene oxide modified with 4-aminodiphenylamine (GO-A). The final adsorbent was characterized by carbon, hydrogen, and nitrogen analysis, Brunauer-Emmett-Teller technique, Fourier transform-infrared resonance spectroscopy, and scanning electron microscopy. Batch studies were carried out to investigate the effect of experimental factors such as contact time (5-120 min), initial dye concentration (10-80 mg/L), and temperature (25 degrees C, 35 degrees C, and 45 degrees C) on the GO-A adsorption of dye. The linear and non-linear forms of kinetic and isotherm models were also investigated. The isotherm and kinetic data of dye were correlated reasonably well by non-linear Freundlich and Elovich models, respectively. The thermodynamic studies showed that the dye adsorption onto GO-A is a spontaneous, favorable, and exothermic process. Additionally, dye isotherm studies revealed that maximum dye adsorption capacities of 10.71, 8.03, and 5.71 mg/g were achieved for 25 degrees C, 35 degrees C, and 45 degrees C temperatures, respectively. It can be collected that GO-A could be applied as an effective adsorbent for the removal of dye.