Performances of local chitosan and its nanocomposite 5%Bentonite/Chitosan in the removal of chromium ions (Cr(VI)) from wastewater

The present work focuses on the study of the application of abundant and less expensive materials such as chitosan (CS) and bentonite/chitosan nanobiocomposite (nano 5%Bt/CS) in the removal of hexavalent chromium. The adsorption behavior of the prepared materials (CS and nano 5%Bt/CS) was tested for the removal of chromium (VI) ions in a synthetic solution and wastewater from a tanning industry. Spectroscopic analysis like techniques FTIR, XRD and SEM/EDX have been used to characterise the adsorbents before and after their contact with chromium ions. The experimental data indicate that the adsorption of chromium proceeds kinetically according to a pseudo-second order model on both adsorbents and the apparent activation energy (Ea) have been measured to be 4.11kJmol-1 and 15.98kJmol-1 for chitosan and nano 5%Bt/CS, respectively. It was found that the non-linear modelling of experimental isotherms was well adapted to the Langmuir and Redlich-Peterson models. Thermodynamic parameters (i.e., change in the free energy (ΔG°), the enthalpy (ΔH°), and the entropy (ΔS°)) have been also, evaluated and the results revealed that the removal of chromium ions on both solids was done via physical adsorption. The adsorption test on a real rejection of the tanning industry shows that the CS and nano 5%Bt/CS can substitute other more expensive adsorbents.