Removal of Cr(VI) from aqueous solution using modified corn stalks: Characteristic, equilibrium, kinetic and thermodynamic study

The adsorbent modified from corn stalks was synthesized after the reaction between epichlorohydrin and triethylamine by using diethylenetriamine (DETA) as modifying agent in the presence of N,N-dimethylformamide (DMF). The performance of the modified corn stalks (MCS) was characterized by BET, SEM, zeta potential, FTIR and thermogravimetric analysis. The adsorption of Cr(VI) from aqueous solutions with MCS which contained amine groups was studied at varying adsorbent dose, initial Cr(VI) concentration, pH, contact time and temperature. Results showed that the Cr(VI) adsorption depended insignificantly on pH but significantly on temperature. The batch equilibrium data fitted well to the Langmuir isotherm. Maximum adsorption capacity of MCS for Cr(VI) was 200.00 mg/g at 303 K which was relatively large compared to some adsorbents as reported. Kinetic data were best fitted with the pseudo-second-order kinetic model. The intra-particle diffusion model was applied to investigate the adsorption mechanisms. The obtained thermodynamic parameters showed that the adsorption of Cr(VI) onto the adsorbent was an spontaneous and endothermic process. These results showed that the anion exchanger could be considered as a potential adsorbent for the removal of Cr(VI) ions from aqueous solutions.