The present study aims to evaluate the biosorption of reactive orange dye by using garden grass. Experiments were carried out in a batch reactor to obtain equilibrium and thermodynamic data. Experimental parameters affecting the biosorption process such as pH, shaking time, initial dye concentrations, and temperature were thoroughly examined. The optimum pH for removal was found to be 4. Fourier transform infrared spectroscopy analysis indicated that the electronegative groups on the surface of garden grass were the major groups responsible for the biosorption process. Four sorption isotherm models were employed to analyze the experimental data of which Temkin and Pyzhey model was found to be most suitable one. The maximum biosorption capacity was 12.2 mg/g at 30 °C. The maximum removal percent reached 90% at optimum conditions. Therefore, the pretreatment or modification of this biosorbent may enhance the biosorption capacity. Thermodynamic parameters (i.e., change in the free energy, the enthalpy, and the entropy) were also evaluated and their values revealed that the biosorption process was exothermic in nature and less favorable at high temperature.
