Adsorptive removal of Cr(VI) from aqueous solutions by cross-linked chitosan/bentonite composite

−Cross-linked chitosan/bentonite composite (CCB) was prepared, and characterized by Fourier transform infrared (FTIR) spectroscopy, BET surface area and pore diameter analyses, X-ray diffraction (XRD) patterns and thermal gravimetric analyses (TGA). The adsorption of hexavalent chromium Cr(VI) onto CCB as a function of adsorbent dosage, initial Cr(VI) concentration, solution pH, and contact time was investigated through batch experiments. The removal towards Cr(VI) decreased with increasing solution pH from 2 to 11 and initial Cr(VI) concentration, while it increased with increasing adsorbent dosage. The adsorption kinetic data of Cr(VI) on CCB were well described by the pseudo-second-order model. The equilibrium data were correlated by the Langmuir isotherm model. The maximum monolayer Cr(VI) adsorption capacity for CCB at pH 2 and 293 K was 89.13 mg/g. The mechanisms for the adsorption of Cr(VI) on CCB at pH 2 may include electrostatic interaction and chemical interaction between CCB and Cr(VI) ions.