Study on the binding interaction of chromium(VI) with humic acid using UV-vis, fluorescence spectroscopy and molecular modeling

In this report, the binding interaction of chromium(VI), as Cr2O73-, with humic acid was studied by using UV-visible absorption, fluorescence spectroscopy, and molecular modeling method. The fluorescence spectral data indicated that the binding interaction existed between Cr2O72- and humic acid and the order of magnitude of binding constants were 10(3). The rise in temperature caused a decrease in the values of the binding constant of humic acid with Cr2O72-. Thermodynamic analysis presented that multi-intermolecular forces including hydrogen bonding, hydrophobic, and electrostatic forces were involved in the binding process at pH 6.5. The spectral data also indicated that Cr2O72- affected the aromatic ring structures in humic acid. Furthermore, the molecular modeling analysis indicated that a lot of reactive groups and binding cavities in HA played a key role in its binding with Cr2O72-. (C) 2014 Elsevier B.V. All rights reserved.