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Chlorination and monochloramination of 3-aminophenol: kinetics and formation of first by-products
O Abou Mehrez1, F Dossier-Berne, B Legube
1a Equipe Eaux-Géochimie organique-Santé, Ecole Nationale Supérieure d'Ingénieurs de Poitiers , Institut de Chimie des Milieux et Matériaux de Poitiers, Université de Poitiers , CNRS UMR 7285, 1 rue Marcel Doré, TSA 41105, 86073 Poitiers cedex 9 , France.
Abstract:
Aminophenols (AP) are synthetic intermediates in pharmaceutical, photographic and chemical dye industry. They can be released into the environment from wastewater and can react during water treatment processes. Therefore, it was interesting to study the oxidation of AP with chlorine and monochloramine in aqueous solution. In particular, the chlorination and monochloramination of 3-aminophenol (3AP) were investigated, and the formation of first by-products and kinetic rates were determined. The chlorination rate was 3.6 × 10(5) times greater than the monochloramination rate at pH 8.6. Two reaction pathways can explain the variation of the monochloramination apparent rate constant with pH. The first one was an electrophilic substitution of Cl(+) on the aromatic ring of the non-ionized 3AP, leading to the formation of chloroaminophenol, with an individual rate constant of 6.7 × 10(2) M(-1) h(-1). The second reaction pathway was a monochloramine attack on the amino group of 3AP catalyzed at acidic pH with an individual rate constant of 9.2 × 10(9) × M(-2) × h(-1).
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