Removal of anionic and cationic dyes with bioadsorbent oxidized chitosans.

Different oxidized chitosans were prepared following various approaches, by thermo-acid oxidation or by using KMnO/NaHSO, (NH)SO/NaHSO and KCrO/NaHSO redox pairs added sequentially or simultaneously. All these reactions pursue the formation of carboxylic groups which enhance their capability to remove model cationic and anionic dyes such as methylene blue and methyl orange, respectively. The resulting oxidized chitosans were structurally and thermally characterized by elemental analysis, infrared spectroscopy, nuclear magnetic resonance, scanning electron microscopy and thermogravimetry.