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Abstract
The degradation by ozone of the hydrolyzed Uniblu-A (Uniblu-OH), i.e. the compound found in the spent bath resulting from dyeing process with the reactive dye Uniblu-A, has been studied with the aim of identifying intermediate as well as end by-products formed. The experimental results, obtained by ozonating (16 mg O3/L in the feed gas at 100 mL/min) aqueous solutions (500 ml) of Uniblu-OH (40 mg/L), in the presence or not of t-butanol, show that the oxy-dye is completely removed within 30 minutes and that its decay results only slightly affected by the presence of t-butanol. Several organic by-products have been identified by liquid chromatography-mass spectrometry (turboionspray interface) as a result of the oxy-dye degradation. Such by-products result from oxidation of the amino group, hydroxylation of the aromatic rings, cleavage of the alkyl chain, cleavage of the sulfoalkylbenzene group leaving substituted anthraquinone structures and cleavage of the latter structures leading to phthalic acid. Such by-products are further degraded leading to the formation of low molecular weight aldehydes and acids, nitrate and sulphate. As for the formation of inorganic end by-products, after 120 minutes of ozonation, the percentages of nitrate and sulphate conversion resulted 6 and 7 %, 53 and 89% in the absence and in the presence of t-butanol respectively.
