MODELING MIXED WASTE REMEDIATION WITH CYCLODEXTRIN

Carboxymethyl-â-cyclodextrin (CMCD) has been shown to be an effective remediation agent for chlorinated hydrocarbons. Based on limited experimental data, cyclodextrin (CMCD) has also been shown to increase the solubility of Cd, Ni, Sr and Hg raising the possibility that this sugar could be used to remediate mixed waste sites (metals and organics). We present the results of laboratory experiments using a mixture of three metals, Pb, Sr and Zn together with PCE show that the ability of CMCD to complex metal salts was not changed in the presence of PCE. For instance, CMCD solutions of up to 20 grams/L produce enhancement in the solubility of Pb of about 30-fold even if the solution is saturated with respect to PCE.

The experimental data is used to determine conditional stability constants, which are added to the database for the geochemical code PHREEQC. The modified database also includes the acid-base and organic complexation behavior of CMCD. The modified database can be used to simulate pump and treat remediation of Pb, Zn and PCE contaminated sediments for more realistic conditions including those where the metals and organics occur as salts, free product and sorbed phases. The simulations show that for relatively low concentrations of CMCD (10g/L), the removal of mixed wastes may be up to 50X faster than conventional pump and treat approaches.