Adsorption of hexavalent chromium from aqueous medium using a new Schiff base Chitosan Derivative

Modification of chitosan biopolymer was achieved by grafting (3-phenyl-1H-pyrazole-4-carbaldehyde) by the Schiff base reaction to synthesize a new chitosan derivative (ChD). The formation of the product was confirmed by FTIR, XRD and 13CNMR analysis. The grafted molecule provided additional nitrogen bearing groups as binding sites. The new derivative was used to investigate the removal of Cr (VI) ions in water. The sorption was best favoured at a pH of 3.0. From the Langmuir isotherm, the maximum monolayer adsorption capacity for the adsorbent was determined (Qo=63.5 mg/g). The sorption data fitted satisfactorily to the Redlich-Peterson isotherm. The kinetics of adsorption was best described by pseudo-second order rate equation. The thermodynamic study revealed that the adsorption of Cr (VI) on to ChD was spontaneous and accompanied by increase in entropy. The metal removal was favoured at lower temperatures indicating that the adsorption was exothermic in nature.