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-beta-cydodextrin (HP beta CD) was examined for its ability to stabilize aqueous-phase ozone (O-3) and prolong oxidation potential through inclusion complex formation. Partial transformation of HP beta CD by O-3 was observed. However, HP beta CD proved to be sufficiently recalcitrant, because it was only partially degraded in the presence of O-3. The formation of a HP beta CD:O-3 clathrate complex was observed, which stabilized decay of O-3. The presence of HI13CD increased the O-3 half-life linearly with increasing HP beta CD: O-3 molar ratio. The O-3 halflife in solutions increased by as much as 40-fold relative to HP beta CD-free O-3 Solutions. Observed O-3 release from HP beta CD and indigo oxidation confirmed that the formation of the inclusion complex is reversible. This proof-of concept study demonstrates that HP beta CD can complex O-3 while preserving its reactivity. These results suggest that the use of clathrate stabilizers, such as HP beta CD, can support the development of a facilitated-transport enabled ISCO for the O-3 treatment of groundwater contaminated with recalcitrant compounds. (C) 2016 Elsevier B.V. All rights reserved.