Oxidation of As(III) to As(V) using ozone microbubbles

Area of Science:

• Environmental Chemistry
• Water Treatment Technologies

Background:

• Arsenic contamination in water poses significant health risks.
• Arsenic(V) is more easily removed by adsorption than arsenic(III).
• Ozone is a powerful oxidant increasingly used in water purification.

Purpose of the Study:

• To investigate the oxidation of toxic arsenic(III) to less toxic arsenic(V) using ozone microbubbles.
• To elucidate the oxidation mechanisms, including the roles of hydroxyl radicals and carbonate ions.
• To study the kinetics of arsenic(III) oxidation by ozone.

Main Methods:

• Pilot-plant study using ozone microbubbles for arsenic oxidation.
• Investigation of pH effects on the oxidation rate.
• Use of 2-propanol as a hydroxyl radical scavenger.
• Analysis of carbonate ion effects on oxidation kinetics.

Main Results:

• Ozone microbubbles effectively dissolved ozone, enhancing oxidation efficiency.
• Rapid arsenic(III) oxidation to arsenic(V) was observed across a wide pH range (4-9).
• Hydroxyl radicals were confirmed to play a role in oxidation under acidic conditions.
• Carbonate ions accelerated arsenic(III) oxidation, likely via carbonate radical formation.

Conclusions:

• Ozone microbubble technology is a viable method for converting toxic arsenic(III) to less toxic arsenic(V) in water.
• Understanding the roles of hydroxyl radicals and carbonate ions is crucial for optimizing ozone-based arsenic remediation.
• The study provides insights into the kinetics of arsenic(III) oxidation by ozone.