Aqueous reactions of ozone with primary aromatic amines

Ozone reacts readily with primary aromatic amines (aniline, 3-methylaniline, 3-chloroaniline, 4-bromoaniline, 4-nitroaniline) in dilute aqueous solutions (10$\sp{-5}$-10$\sp{-4}$ M). The major isolated reaction products identified by GC/MS were nitrosobenzenes, nitrobenzenes, azobenzenes, azoxybenzenes, benzidines, aminodiphenylamines, and phenazines. The N-substituted polyaromatic compounds (NPACs), azobenzenes, azoxybenzenes, and benzidines, were the products of interest because of their potential toxicity. When the reactions were conducted under experimental conditions approximating drinking water treatment ((aniline) = 1.00 $\times$ 10$\sp{-5}$ M and (O$\sb3$) = 2.00 $\times$ 10$\sp{-5}$ M, (CO$\sb3\rbrack \sb{\rm T}$ = 1.00 $\times$ 10$\sp{-2}$ M, pH 8.2), the yields of azobenzene and azoxybenzene were 0.78% and 0.15%, respectively. The experimental data showed that the reaction mechanisms for the formation of these NPACs mainly, but not exclusively, involve free radicals initiated by hydroxyl radical. Addition of mannitol, a $\cdot$OH scavenger, in most cases, significantly reduced NPACs formation. The actual reduction in the yield of azobenzene by the addition of mannitol was close to the values predicted by kinetic analysis. Hydrogen ion concentrations (pH 7.25-10.65), the selection of inorganic buffer (phosphate or carbonate), and aniline concentrations (0.10-1.00 $\times$ 10$\sp{-4}$ M) affected the yields of these NPACs. Raising the pH increased the yields of azobenzene and azoxybenzene by increasing $\cdot$OH formation. The reaction mixture with the carbonate buffer showed even a greater increase in these products due to the shift of the oxidation mechanism to the highly selective carbonate radical pathway. Additionally, lowering the relative concentration of aniline to the carbonate buffer increased the yields of azobenzene and azoxybenzene. However, the formation of benzidine was higher at pH 8.25 than at pH 10.65. The presence of dissolved organic and inorganic matter in the reaction systems significantly reduced the yield of azobenzene, azoxybenzene, and benzidine without affecting aniline removal.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Environmental Engineering

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2011

Author dc:creator

• Chan, Wayne Fai

Contributors dc:contributor

• Larson, Richard A.

• Engineering, Sanitary and Municipal

Statement dc:rights

• Copyright 1991 Chan, Wayne Fai

Language dc:language

eng

Identifier

AAI9210759
(UMI)AAI9210759

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/21908