Magnetic red mud/chitosan based bionanocomposites for adsorption of Cr(VI) from aqueous solutions: synthesis, characterization and adsorption kinetics

Magnetic red mud/chitosan (MRM/CS) based bionanocomposites were prepared by the neutralization method, and this method had the advantages of simplicity, low-cost and eco-friendly. The adsorbents were characterized by XRD, FTIR and VSM analysis. The effects of various parameters, such as RM addition amounts, pH, concentration, temperature, time and co-existing metal ions, on the adsorption of Cr(VI) were studied. Moreover, adsorption kinetic, isotherm and thermodynamic of the Cr(VI) adsorption were analyzed. The results show that the MRM/CS composite has good recoverability (8.56 emu·g −1 ) and adsorption performance (7.79 mg·g −1 , 303 K, pH = 3). The process of the adsorption reaction conforms to the Langmuir model and the pseudo-second-order kinetic model, suggesting that the adsorption of Cr(VI) ions on the surface of CS-based adsorbents are monolayer adsorption and chemisorption. Thermodynamic study reveals that the adsorption is spontaneous and endothermic.