Application of pyridine-modified chitosan derivative for simultaneous adsorption of Cu(II) and oxyanions of Cr(VI) from aqueous solution

The bioadsorbent C1, which is a chitosan derivative prepared in a one-step synthesis, was successfully used to adsorb Cr(VI) and Cu(II) simultaneously. Here, for the first time the simultaneous adsorption of a cation and an anion was modeled using the Corsel model for kinetics and the Real Adsorbed Solution Theory model for equilibrium data. Batch studies of the adsorption of Cu(II) and Cr(VI) in single and binary aqueous solutions were performed as a function of initial solute concentration, contact time, and solution pH. The maximum adsorption capacities of C1 in single and binary aqueous solutions were 1.84 and 1.13 mmol g(-1) for Cu(II) and 3.86 and 0.98 mmol g(-1) for Cr(VI), respectively. The reuse of C4 was investigated, with Cu(II) ions being almost completely desorbed and fully re-adsorbed. For Cr(VI), the desorption was incomplete resulting in a lower readsorption. Energy-dispersive X-ray spectroscopy was used for mapping the distributions of Cr(VI) and Cu(II) adsorbed on the C1 surface in single and binary adsorption systems. Isothermal titration calorimetry experiments were performed for Cr(VI) and Cu(II) adsorption in single solutions. The thermodynamic parameters of adsorption showed that the adsorption of both metal ions was enthalpically driven, but entropically unfavorable.

Automated summary

The bioadsorbent C1 was successfully used to simultaneously adsorb Cr(VI) and Cu(II) through one-step synthesis, and modeling was conducted using the Corsel model for kinetics and the Real Adsorbed Solution Theory model for equilibrium data. The maximum adsorption capacities of C1 for Cu(II) and Cr(VI) in single and binary aqueous solutions were determined, showing different values for each metal ion. The reuse of C4 was investigated, with different desorption and readsorption behaviors observed for Cu(II) and Cr(VI).