Stabilization and prolonged reactivity of aqueous-phase ozone with cyclodextrin

Area of Science:

• Environmental Chemistry
• Water Treatment Technologies
• Oxidation Chemistry

Background:

• Recalcitrant organic compounds in groundwater, like 1,4-dioxane, pose treatment challenges.
• In-situ chemical oxidation (ISCO) efficacy is often limited by oxidant decay and reactivity.
• Strong oxidants are necessary for complete mineralization of persistent pollutants.

Purpose of the Study:

• To investigate the potential of hydroxypropyl-β-cyclodextrin (HPβCD) to stabilize aqueous ozone (O3).
• To evaluate the prolonged oxidation potential of stabilized ozone through inclusion complex formation.
• To assess the feasibility of using HPβCD as a clathrate stabilizer for ISCO applications.

Main Methods:

• Complexation of aqueous ozone (O3) with hydroxypropyl-β-cyclodextrin (HPβCD).
• Monitoring of O3 decay kinetics in the presence and absence of HPβCD.
• Assessment of HPβCD's recalcitrance to O3 degradation.
• Confirmation of reversible inclusion complex formation via O3 release and indigo oxidation.

Main Results:

• HPβCD formed a clathrate complex with O3, stabilizing its decay.
• HPβCD demonstrated significant recalcitrance to O3 degradation.
• Ozone half-life increased up to 40-fold with increasing HPβCD:O3 molar ratio.
• Complex formation was reversible, preserving O3 reactivity.

Conclusions:

• HPβCD effectively stabilizes aqueous O3 via reversible clathrate complexation.
• HPβCD can enhance O3 half-life and maintain its oxidation potential.
• HPβCD shows promise as a clathrate stabilizer for facilitated-transport ISCO of recalcitrant groundwater contaminants.