ENHANCED SOLUBILIZATION AND DESTRUCTION OF TETRACHLOROETHYLENE BY HYDROXYPROPYL-BETA-CYCLODEXTRIN AND IRON

Hydroxypropyl-beta-cyclodextrin (HP-beta-CD) enhances the solubility o f tetrachloroethylene (PCE) in water bath in static and in flowing sys tems. HP-beta-CD does not decrease the interfacial tension between PCE and water and, therefore, should not mobilize immiscible-phase PCE in the subsurface. Rates for the reaction of PCE with metallic iron were measured in HP-beta-CD solutions under static conditions. In Rowing s ystems, metallic iron removed PCE, and no other chlorinated ethylene s pecies were observed in the column effluent. in several such systems, recycling of the HP-beta-CD solution took place following the reaction with iron. No downward mobilization of the PCE pool in the generator column was observed. The solubility enhancement and reaction with meta llic iron are consistent with reversible formation of a stoichiometric HP-beta-CD/PCE complex. A theoretical treatment of the reaction rates of complexed PCE on an iron surface was developed. This treatment sug gests that any material that enhances the solubility of low-solubility organic substances may slow down the rate of reaction in aqueous solu tion. In many cases, the rate retardation should equal the degree of s olubility enhancement The combination of HP-beta-CD and iron metal app ears to be a promising groundwater remediation technology.