Chitosan/iron oxide nanocomposite films: Effect of the composition and preparation methods on the adsorption of congo red

Composite films based on chitosan, glycerol and magnetic iron oxides were obtained by two different procedures: in situ generation of iron oxide particles in the already formed films and dispersion of previously synthesized iron oxide particles into the film forming solution by sonication, and then tested as adsorbents for the removal of congo red (CR) from solutions of different concentrations. Their performances were compared with those of the corresponding films without particles. All the samples presented similar behavior when contacted with solutions containing up to 70 mg/L CR (maximum sorption capacity (similar to)25 mg/g), but sonicated samples exhibited an increased dye adsorption when in contact with more concentrated solutions, reaching up to 700 mg/g sorption capacity. These differences were explained considering the obtaining procedure of the films, their composition and microstructure, as well as the changes in the pH of the dye solution once the adsorbent film was put inside.