Kinetic, Isotherm, and Thermodynamic Studies of the Adsorption of Methyl Orange from Aqueous Solution by Chitosan/Alumina Composite

Alumina, a support material, was loaded with chitosan to form a chitosan/alumina composite (CA) and was utilized for removing sulfonated azo-dye methyl orange (MO) from aqueous media in this study. The adsorbents were characterized by Fourier transform infrared (FTIR) spectra to confirm that chitosan was successfully immobilized on alumina, and some functional groups were successfully introduced into the surface of alumina after modification. The effects of pH, the amount of adsorbent, initial concentration, time, and temperature were studied in batch experiments. The experimental data were analyzed by Langmuir and Freundlich adsorption isotherms. Thermodynamic parameters such as Δ G o, Δ H o, and Δ S o have also been evaluated, and it has been found that the sorption process was spontaneous and exothermic in nature. Pseudofirst-order and pseudosecond-order kinetic models were used to fit the experimental data. Kinetic parameters, rate constants, equilibrium adsorption capacities, and related correlation coefficients for each kinetic model were calculated and discussed. It revealed that the adsorption of MO could be described by the pseudosecond-order equation, suggesting that the adsorption process is presumably chemisorption.