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A new efficient, low cost chitosan based biosorbent was successfully prepared and employed for the biosorption of copper ions from an aqueous solution using a fixed bed column. Pyromellitic dianhydride crosslinked chitosan as the new adsorbent was characterized by SEM, FTIR spectroscopy, X-ray diffraction, thermogravimetric analysis and solid state (13)C NMR analysis. Scanning electron microscopy coupled with an X-ray energy dispersed analysis for the copper-equilibrated biomass confirmed the presence of Cu(II) ions on the surface of the hydrogel. Thermogravimetric analysis showed a significant improvement in the thermal stability of the new hydrogel compared to pure chitosan. Kinetic models were applied to predict the breakthrough curves. This study shows that the prepared hydrogel based on modified chitosan could be utilized as an efficient bioadsorbent for the removal of copper ions from wastewater., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Unsatisfactory mechanical properties, poor heat resistance, dissolution in acidic media and high swelling ratios limit using chitosan as an adsorbent in industry. In this study, we used dianhydride derivatives famous for their exceptional mechanical and thermal characteristics and low water absorption. In this study, pyromellitic dianhydride (PMDA), benzophenone-3,3',4,4'-tetracarboxylic dianhydride (BTDA), 4,4'-oxydiphthalic dianhydride (ODPA) and 4,4'-(hexafluoroisopropylidene)diphthalic dianhydride (FDA) were utilised as crosslinking agents. Use of common crosslinking agents usually decreases the metal uptake capacity of chitosan. These novel crosslinking agents increased the metal uptake from 1.8 (ODPA/Cu 2+ ) to 7.8 (PMDA/Zn 2+ ) times. Langmuir and Freundlich adsorption models were applied to analyse the isotherms and isotherm constants. Kinetic, X-ray diffraction, pH, FTIR studies were also carried out., (Copyright © 2011 Elsevier Ltd. All rights reserved.)