Synthesis and characterization of recyclable O-carboxymethyl chitosan Schiff base for the effective removal of Cd(II) from aqueous solution

A novel O-carboxymethyl chitosan Schiff base (OCMCS-SB) was synthesized by condensation of O-carboxymethyl chitosan and o-vanillin and evaluated as an adsorbent for Cd(II). The structure of the chitosan Schiff base was characterized through Fourier transform infrared spectroscopy, thermogravimetric analysis/differential thermal gravity, X-ray diffraction and scanning electron microscopy. The effect of adsorbent dose, pH, concentration, the contact time was evaluated in the adsorption experiments of Cd(II). The optimum adsorption pH value was found at 5.5. The adsorption isothermal data fitted well with the Langmuir isotherm equation, the kinetics of adsorption was best described by a pseudo-second-order model. The maximum adsorption is gained at 480 min as 46.72 mg/g and after that the adsorption attained equilibrium. This OCMCS-SB results to be an excellent adsorbent with good selectivity for Cd(II) from a multi-ionic system, was successfully recycled for several runs without significant loss in its adsorption activity.