Response Surface Modeling of the Removal of Methyl Orange Dye from an Aqueous Solution Using Magnesium Oxide Nanoparticles Immobilized on Chitosan

In this work, the chitosan-based magnesium oxide nanoparticles (CS-MgONP) composite was used as an adsorbent for the removal of the organic dye Methyl Orange (MO). The adsorbent characterization was carried out using X-Ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FE-SEM), and Fourier Transform InfraRed (FT-IR) spectroscopy. The faster equilibrium, i.e. at an agitation time of 30 min, indicated the faster adsorption capability of the prepared adsorbent CS-MgONP. The Central Composite Design (CCD) of response surface methodology (RSM) was used to evaluate the impact of process parameters in the range of pH (6-10), CS-MgONP dosage (0.1-0.5g/L), MO concentration (10-30mg/L), and temperature (283-323K) at an optimal agitation period of 30 min. Under optimum conditions of pH=7.93, CS-MgONP dosage=0.4g/L, initial MO concentration=15mg/L, and temperature=313 K, 96.42% removal of MO was achieved with desirability of 0.805. The adsorption of MO onto CS-MgONP was best fitted with the Langmuir adsorption isotherm, with an uptake capacity of 237.5 mg/g, and followed the pseudo second-order kinetics. The thermodynamic studies showed positive enthalpy and negative Gibbs free energy that confirmed the spontaneous and endothermic process. Due to the fast equilibrium agitation period, i.e.30 min, and high adsorption capacity, the adsorbent CS-MgONP proved to be an excellent choice for dye removal.