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72268 
Journal Article 
Ozonation of water: kinetics of oxidation of ammonia by ozone and hydroxyl radicals 
Hoigne, J; Bader, H 
1978 
1 
Environmental Science & Technology
ISSN: 0013-936X
EISSN: 1520-5851 
12 
79-84 
Ozone initiated oxidation of ammonia in water can result from the direct reaction of 0 3 with NH3 as well as from the reactions of OH. radicals formed upon O3 decomposition. The direct reaction of 0 3 predominates at pH <9. In the presence of low concentrations of free "3, it is a slow reaction; the rate constant for O3 depletion by reaction of O3 with NH3 is 20 k 1 M-' s-l. At pH values >9, OH- and radical-catalyzed decomposition of 03 to the very reactive intermediate, OH., determines the kinetics of the NH3 oxidation. The reaction rate constant of OH. with NH3 is relatively small. Whenever the OH. mechanism is involved, NH3 is easily protected by other solutes which also consume OH. radicals. Even carbonate and bicarbonate ions may act as efficient OH. scavengers. Because carbonate and organic solutes affect the lifetime of 0 3 in water, they consequently shift the pH range in which either the direct 0 3 or the OH. mechanism predominates. A comparison with reactions initiated by gamma irradiation proves helpful in elucidating the reaction mechanisms.