Kinetics, Isotherms, and Thermodynamics Studies on Adsorption of Methyl Green Dye Onto Different Zeolites

The adsorption of methyl green (MG) dye from aqueous solutions over different zeolite samples was investigated. Five types of zeolites H-Y (HY), H-BETA (Beta), NH₄-Mordenite (MOR), NH₄-ZSM-5 (ZSM-5), and NH₄-Ferrierite (FERR) were obtained and characterized by X-Ray diffraction analysis (XRD), Fourier transform infrared spectroscopy (FTIR), inductively coupled plasma (ICP) elemental analysis, N₂ sorption measurements, and scanning electron microscopy (SEM). The obtained characterization results pointed out to several significant differences between the investigated samples such as morphological structure, textural properties, aluminium content, and the counter cation. The adsorption capacities of HY, Beta, and MOR zeolites using MG were determined to be 41.54, 25.05 mg/g, and 40.57, respectively. On the other hand, FERR and ZSM-5 exhibited the smallest adsorption capacity. The process of adsorption was optimized in terms of a number of variables, including contact time, adsorbent dosage, solution pH, dye concentration, and solution temperature. Moreover, the kinetics, isotherm, and thermodynamic parameters of adsorption were calculated. The Langmuir isotherm model had the best correlation with the experimental data, and the kinetics studies showed that the adsorption followed pseudo-second order kinetics. Moreover, the mechanism of adsorption process was proposed and discussed.