Solubility enhancement of seven metal contaminants using carboxymethyl-β-cyclodextrin (CMCD)

Carboxymethyl-beta-cyclodextrin (CMCD) has been suggested as a complexing agent for remediation of sites co-contaminated with metals and organic pollutants. As part of an attempt to construct a geochemical complexation model for metal-CMCD interactions, conditional formation constants for the complexes between CMCD and 7 metal ions (Ba, Ca, Cd, Ni, Pb, Sr, and Zn) are estimated from experimental data. Stable metal concentrations were reached after approximately 1 day and estimated logarithmic conditional formation constants range from -3.2 to -5.1 with confidence intervals within +/- 0.08 log units. Experiments performed at 10 degrees C and 25 degrees C show that temperature affects the solubility of the metal salts but the strength of CMCD-metal complexes are not affected by this temperature variation. The conditional stability constants and complexation model presented in this work can be used to screen CMCD as a potential remediation agent for clean-up of contaminated soil and groundwater. (C) 2009 Elsevier B.V. All rights reserved.