Stabilization and Prolonged Reactivity of Aqueous-Phase Ozone with Cyclodextrin.

Recalcitrant organic groundwater contaminants, such as 1,4-dioxane, may require strong oxidants for complete mineralization. However, their efficacy for in-situ chemical oxidation (ISCO) is limited by oxidant decay and reactivity. Hydroxypropyl-β-cyclodextrin (HPβCD) was examined for its ability to stabilize aqueous phase ozone (O3)and prolong oxidation potential through inclusion complex formation. Partial transformation of HPβCD by O3 was observed. However, HPβCD proved to be sufficiently recalcitrant, because it only partially degraded in the presence of O3. The formation of a HPβCD:O3 inclusion clathrate complex was observed, which delayed decay of O3. The presence of HPβCD increased the O3 half-life linearly with increasing HPβCD:O3 molar ratio. The O3 half-life in solutions increased by as much as 40-fold relative to HPβCD-free O3 solutions. Delayed release and indigo oxidation confirmed that the formation of the inclusion complex is reversible. This proof-of-concept study demonstrates that HPβCD can complex O3 while preserving its reactivity. These results suggest that the use of clathrate stabilizers, such as HPβCD, can support the development of a facilitated-transport enabled ISCO for the O3 treatment of groundwater contaminated with recalcitrant compounds. EnChem Engineering, Inc. has patented this technology with plans to commercialize O3 complexed with HPβCD to enhance the remediation of contamination in soil and groundwater.