Degradation of Aqueous Phenol and Chlorinated Phenols by Ozone

Abstract

The degradation of phenol and its chlorinated derivatives with ozone is studied. The studied compounds are phenol (Ph), 4-chlorophenol (4-CPh) and 2,4-dichlorophenol (2,4-DCPh). The kinetic performances of each phenolic compound and their model mixture are examined. The pH influence on the decomposition dynamics for different phenolic compounds in the range 2–12 is investigated. The increase of the decomposition rate under increasing pH was observed. In the pH range studied, phenol and chlorophenols ozonation proceeds rapidly. The UV absorbency is used for the preliminary control of the degree of decomposition. The HPLC analysis is used to identify intermediates and final products formed during ozonation. It is shown that the basic intermediates are muconic and fumaric acids, malonic and maleic acids, catechol and hydroquinone. The final products are oxalic acid and formic acid. In the case of alkaline media, the principal final product is oxalic acid. Furthermore, intermediates and final decomposition products obtained at different pH are compared. According to the results obtained, the possible mechanism of ozonation by the reaction of hydroxylation and dechloration in the early stage is proposed. The BOD₅/COD ratio is used as a biodegradability measure for the comparison of biodegradability of initial compounds and final products composition.

Keywords:

• Ozone
• Phenol Decomposition
• Chlorophenols Decomposition
• pH Effect

ACKNOWLEDGMENTS

The authors thank the Department of Graduate Study and Investigation of the National Polytechnic Institute of Mexico for the supporting of this investigation.

Notes

*Probably chlorocatecholes, chlorohydroquinones and aldehydes, etc.

^a Hautaniemi et al., 1998a;

^b Razumovskii and Zaikov, 1984;

^c Hoigne and Bader, 1983-I.

“Biochemical Oxygen Demand (BOD)“, Standard Methods for Examination of Water and Wastewater, American Water Works Association (AWWA), Water Pollution Control Federation (WPCF), 19a Ed.