Application of magnesium oxide nanoparticles for malachite green removal in aqueous solutions: adsorption isotherm, kinetic and thermodynamic studies

In this study, we successfully developed a new magnesium oxide nanoparticles (MgO) absorbent for theadsorption of the cationic malachite green (MG) dye. Scanning electron microscopy and Fouriertransform infrared spectroscopy were carried out to characterize the MgO adsorbent's physical, chemicaland surface morphology. In the newly developed absorbent, the effect of pH, contact time, temperature,adsorbent dose, thermodynamic, adsorption isotherms and adsorption kinetics were investigated. Theoptimum results (pH=۷.۰, ۳۰ minutes contact time in ambient temperature) was observed for ۱۰.۰ mg ofMgO adsorbent. The adsorption of MG on MgO was fitted well to Freundlich model (R۲=۰.۹۳). Kineticsof adsorption follows Pseudo-second order (R۲=۱). Based on thermodynamic results, the adsorption ofMG on the surface of MgO nanoparticles is endothermic (an increasing trend with temperature can beobserved). Also, the Negative Gibbs free energy and the positive values of entropy have demonstratedthat the adsorption of MG on MgO substrate and increasing in the interface disordering of the MgOsolution during the fixation of MG.