Oxidation of chlorophene by ozonation: Kinetics, identification of by-products and reaction pathways

• Ozonation of chlorophene, a model emerging contaminants (ECs) is investigated.
• Apparent second order rate constants are determined for each pH of work.
• 24 Intermediates by-products are indentified.
• The degradation pathways are proposed for the ozonation reaction.
• Toxicity measurements show a decrease in the pollutant content of the water.

The ozonation of chlorophene, an emerging contaminant frequently present in aquatic systems because of its numerous uses nowadays, is studied. The kinetic experiments allowed the determination of the apparent rate constants for its reaction with ozone in the pH range 3–11. The rate constants values obtained varied from 1.67 × 103 L mol−1 s−1 at pH = 3 to 1.82 × 105 L mol−1 s−1 at pH = 11. As a consequence of its acidic nature (pKa = 9.81), the degree of dissociation of this pollutant was determined at every pH of work, and the specific rate constants of the neutral and anionic species were evaluated, being these rate constants k1 = 2.8 × 103 L mol−1 s−1 and k2 = 2.5 × 105 L mol−1 s−1. Up to 24 by-products formed in the ozonation reaction were identified by liquid chromatography/mass spectrometry using a high-resolution time of flight analyzer (LC-TOFMS). From these intermediates identified, the degradation pathways are proposed and discussed. Toxicity measurements of the ozonated chlorophene solutions revealed that these by-products are less toxic than the parent compound.