Removal of anionic dye from aqueous solution by chitosan-magnetite nanocomposite

Chitosan-magnetite nanocomposite (CM) was synthesised using the one-step procedure, reducing the synthesis time and the complexity of the process. The synthesized CM was characterised by using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET), vibrating sample magnetometer (VSM). The nanocomposite was used to remove eriochrome black T (EBT) from the aqueous solution. The effects of pH, adsorption time, initial concentration of EBT, dose, and temperatures were studied. The experiment data were analysed by pseudo-first-order, pseudo-second-order, Elovich, and intra-particle-diffusion kinetic models. Among these models, the pseudo-second-order was the best fit model and the adsorption rate constant of EBT was 0.007 g/mg.min. The adsorption isotherms were studied by fitting the experimental data to the Langmuir, Freundlich, and Temkin models. The results indicated that the Langmuir model was the fittest model for describing the isotherms of the EBT adsorption on CM. When the temperature increased from 293 to 313K, the maximum adsorption capacity of EBT decreased from 291.2 to 83.5 mg/g. The thermodynamic study showed that the ETB adsorption process onto CM was a spontaneous and exothermic process with increment G(0), increment H-0 negative. The EBT dye adsorption mechanism was discussed, involved interactions, such as electrostatic attraction and H-bonding. CM could be regenerated and reused to adsorb anionic dye.