Effective detoxification of hexavalent chromium using sulfate-crosslinked chitosan.

A sulfate-crosslinked chitosan (SCC) was prepared for effective detoxification of hexavalent chromium (Cr(VI)) from effluents. SCC was characterized using Fourier transform infrared, X-ray diffraction, scanning electron microscopy and energy dispersive X-ray studies. The maximum adsorption of Cr(VI) was observed at pH 6.0 with adsorption capacity of 157 mg/g in accordance with the Langmuir adsorption isotherm model. The adsorption process was found to follow the pseudo-second-order rate kinetics. From the study of various thermodynamic parameters (Gibbs energy, entropy and enthalpy changes), the adsorption capacity was found to decrease with increase in temperature. Column studies were carried out to obtain a breakthrough point of the adsorbent. The adsorbent was regenerated using sodium hydroxide with no change in the adsorption efficiency for up to 10 cycles. Effect of diverse ions on adsorption efficiency was studied and SCC was applied for Cr(VI) removal in synthetic effluents.