Adsorptive removal of malachite green dye from aqueous solution by ion exchange resins

The adsorption of malachite green dye by commercially available synthetic polymers Diaion CR-11 and Amberlite IRC-748 resins has been studied. The effect of the initial dye concentrations, adsorbent dosage, contact time, pH, and temperature were examined. The dye adsorption mechanism for both resins was investigated using Langmuir, Freundlich, Scatchard, and Dubinin-Radushkevich (D-R) isotherm models. Also, experimental data were applied to the pseudo-first-order and pseudo-second-order kinetic models. The Langmuir isotherm and pseudo-second-order kinetic model best fit to the equilibrium data showed maximum adsorption capacities of 102.1 mg/g and 480.6 mg/g for Diaion CR-11 and Amberlite IRC-748, respectively. Thermodynamic studies show that the adsorption of malachite green dye increases with temperature and indicates that the adsorption process of both resins is endothermic. The negative value of change in Gibbs free energy shows spontaneous adsorption of malachite green on both resins. The polymer resins are characterized by Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscope (SEM).