Cross-linked chitosan into graphene oxide-iron(III) oxide hydroxide as nano-biosorbent for Pd(II) and Cd(II) removal.

In this study, chitosan cross-linked into graphene oxide/iron(III) oxide hydroxide nanocomposites. For this purpose, to a mixture of graphene oxide in deionized water was added to iron(II) sulfide and hydrogen peroxide solution. The pH was then adjusted. Then, chitosan dissolved in acetic acid was added. This compound applied as nano-biosorbent for the removal of Pd(II) and Cd(II) ions from aqueous solution. Nanocomposites were characterized by FT-IR, XRD, SEM, and EDX analysis. The effects of valid parameters such as pH (2-9), sorbent mass (0.01-0.1 g), temperature (25-60 °C), and contact time (20-50 min) were investigated in adsorption of Pd(II) and Cd(II) ions. The results showed that oxygen-containing functional groups on the surface of graphene oxide, iron(III) oxide hydroxide nanoparticles, and the abundant amino and hydroxyl functional groups of chitosan chain were shown excellent potential for Pd(II) and Cd(II) adsorption. The removal percentage of Pd(II) and Cd(II) were 84 and 95%, respectively. The Freundlich and Langmuir adsorption isotherms were investigated for the description of adsorption onto nanocomposites. However, the Freundlich model showed a higher correlation coefficient (R2) than Langmuir isotherm. The pseudo-second-order equation was the best fitted kinetic model for this process.