Intrinsic Electric Field Triggers Phenol Oxidative Degradation at Microbubble Interfaces.

Area of Science:

• Environmental Chemistry
• Physical Chemistry
• Green Chemistry

Background:

• Phenol is a toxic and persistent environmental pollutant found in industrial wastewater.
• Conventional phenol removal methods often require high energy input or expensive catalysts.
• Developing sustainable and efficient degradation techniques for phenolic compounds is crucial.

Purpose of the Study:

• To investigate the oxidative degradation of phenol at air-water interfaces (AWIs) using microbubbling.
• To elucidate the degradation pathway and underlying mechanism of phenol oxidation at AWIs.
• To evaluate the efficiency and sustainability of this AWI-mediated oxidation process.

Main Methods:

• Microbubbling of air through aqueous phenol solutions.
• High-resolution mass spectrometry for identifying degradation products.
• Vortex experiments to study the degradation pathway.
• Radical scavenger experiments and DFT calculations to explore the reaction mechanism.
• Analysis of para-halogenated phenols to support the proposed mechanism.

Main Results:

• Achieved over 96% degradation of 2 mM phenol solution within 3 hours.
• Identified acetic acid as the final degradation product.
• Elucidated a degradation pathway involving hydroxylation, dehydrogenation, and ring cleavage.
• Provided evidence for an interfacial electric field-induced excitation pathway via radical reactions.
• Demonstrated a reagent-free, efficient, and mild oxidation process.

Conclusions:

• AWI-mediated oxidation is a highly effective and sustainable strategy for degrading phenolic pollutants.
• The process offers advantages over conventional advanced oxidation processes, including reagent-free operation and reduced secondary pollution.
• The findings support an interfacial field-induced molecular activation mechanism for phenol degradation at AWIs.