Direct, radical and competitive reactions in the ozonation of water micropollutants

Abstract

Contribution of direct and radical reactions in the ozonation of three water micropollutants: ortho‐chlorophenol, mecoprope and atrazine, including competition of secondary reactions, are evaluated. Consumption rates of ozone due to these contributions are determined at different ozone partial pressure and pH. In the ozonation of ortho‐chlorophenol the oxidation is due to the direct reaction with ozone and an important fraction of the ozone absorbed (up to 60%) is also consumed by intermediate compounds. The pesticides studied, mecoprope and atrazine, show different behaviour for the ozone consumption. Thus, radical reactions are the main pathway for the elimination of atrazine, at any pH, and mecoprope at pH = 12. The influence of secondary reactions on the consumption of ozone is also important. Concentration of hydroxyl and superoxide ion radicals are determined from the kinetic data.

Key words:

• Ozonation
• ozone
• kinetics
• pesticides
• water treatment
• mecoprope
• atrazine
• ortho‐chlorophenol