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 was only partially degraded in the presence of O₃. The formation of a HPβCD:O₃ clathrate complex was observed, which stabilized 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. Observed O₃ release from HPβCD 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.