Competitive adsorption of Cu(II) and Cd(II) ions on spray-dried chitosan loaded with Reactive Orange 16

Chitosan microspheres cross-linked with glutaraldehyde and containing the reactive dye Orange 16 (RO 16) as a chelating agent were obtained by spray drying technique. These microspheres (CHS-RO 16) were characterized by FTIR, TGA, DSC, SEM and EDX analyses, and tested for metal adsorption. The new adsorbent was used in batch experiments to evaluate the adsorption of Cu(II) and Cd(II) ions in single and binary metal solutions. In single metal solutions, the maximum adsorption capacity for Cu(II), obtained by Langmuir model, was close to 1.69 mmol Cu g− 1; this means the double of the adsorption capacity for Cd(II) (i.e. 0.80 mmol Cd g− 1). Adsorption isotherms for binary solutions showed that the presence of Cu(II) decreased Cd(II) adsorption due to a significant competition effect. On the other hand, Cu(II) adsorption hardly changed when the initial concentration of Cd(II) increased: the new adsorbent was selective to Cu(II) against Cd(II). The metal ions were efficiently desorbed from chitosan-RO 16 with aqueous solutions of H2SO4.