The adsorptive removal of Methyl Orange (MO) dye using a sugar beet bagasse (SBB) as agro-industrial byproduct has been investigated. The adsorption potential of SBB was improved by grafting with FeCl3, 6H2O. The dependency of removal efficiency (R) and adsorption capacity (qe) on the level and magnitude of variables including initial pH, MO concentrations and sorbent dosage was investigated and optimized by central composite design (CCD) under response surface methodology (RSM). Besides, the effect of temperature on adsorption process was evaluated in terms of thermodynamic study. The good agreement found between observed and predicted values supports and confirms the suitability of the applied model to predict adsorption state. The applied models revealed that MO removal in aqueous solution was affected by all the three factors studied. By consideration of 7 starting points in the response surface solutions, the best local maximum was found to be at initial solution pH 2.51, sorbent dosage of 0.37 g.L-1, initial dye concentration of 100 mg.L-1, removal efficiency of 51.8%, adsorption capacity of 221.5 mg.g-1 and desirability of 0.692. A pseudo second-order model more accurately represented the adsorption process. Moreover, Freundlich isotherm model was superior to the Langmuir isotherm model.
