Ozonation des amines dans l'eau ozonation of amines in aqueous solutions

Abstract

Amines are nitrogenated compounds which may be found in water and in the atmosphere. The use of ozone for micropollution removal is growing; the aim of our study is to specify the behaviour of these compounds during ozonation. The studied amines are: methylamine. ethylamine, propylamine, cyclohexylamine, dimethylamine. N-methyl-butylamine and trimethylamine; the tests are classified in two groups. The first group of tests is carried out with concentrated aqueous solutions (7% in weight) to find the ozonation products. the identifications are carried out by the coupling gas chromatography with mass spectroscopy. The second group of tests is carried out with diluted aqueous solutions concentrations (10 ppm) are of which nearer to the usual effluent concentrations than the concentrated solutions ones. 1. The identifed compounds in concentrated solution (Table 1) lead us to propose a reaction diagram (Fig. 3) for the ozonation of primary, secondary, tertiary amines. In any case, we notice an electrophilic attack of ozone on nitrogen lone pair of electrons, with: oxidation products of nitrogen (hydroxylamines, oximes and nitrogen oxides) and of carbon in α position (amides): breakdown products from initial molecules (aldehydes, ketones and acids) associated with the formation of mineral nitrogen (NO 2 -. NO 3 -) condensing products as polyamide types. ▪ Figure 5 shows the evolution of the different products of ozonation in terms of the ozone consumption for the cyclohexylamine instance. 2. In diluted solutions, the oxidation rate of the various amines is linked to the available quantity of ozone (Figs 1 and 2): we find aldehydes, carboxylic acids and nitrates as ozonation products. According to these results, ozone is the choice oxidant for the treatment of industrial sewages and malodorous gas containing amines. The ozone used for the production of drinking water contributes to the removal of this kind of pollution.