Oxidation rates of two textile dyes by ozone: Effect of pH and competitive kinetics

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• 作者：Arlindo C. Gomes^a ; ^b ; Luis R. Fernandes^a ; ^b ; Rogé ; rio M.S. Simõ ; es^a ; ^b ; ^rmss@ubi.pt
• 关键词：Ozone ; Homogeneous reactions ; Kinetics ; Textile dyes ; Competitive reactions
• 刊名：Chemical Engineering Journal
• 出版年：2012
• 期刊代码：16_13858947
• 类别：ce
• 出版时间：1 May, 2012
• 卷：189-190
• 期：Complete
• 页码：175-181
• 文件大小：666 K

摘要

Different dyes can exhibit markedly different reaction rates with ozone. These observations can raise the concern that in a mixture of dyes one of them can be over-oxidized while the other remains under-oxidized, i.e. exhibiting colour. In addition, the effect of pH on decolourisation also deserves additional investigation. The influence of pH on the oxidation rate of the monoazo dye Acid Orange 7 (AO7), one of the most difficult dyes to degrade, was studied in a homogeneous medium. The results have revealed an increase of nearly two orders of magnitude in the AO7 decolourisation rate when pH increased from 3 to 8.2. This effect was only slightly diminished when the radical scavenger was added. Competitive studies were performed between AO7 and the anthraquinone dye Acid Green 27 (AG27), which exhibits a much faster reaction rate. When the two dyes are mixed together, the AO7 decolourisation rate increases markedly, approaching the AG27 values, even under conditions that favour the undissociated species (pH = 2.7). This is a very positive practical result as the charged ozone can be consumed almost indistinctly by the two dyes.