The sonochemical degradation of azobenzene and related azo dyes: Rate enhancements via Fenton's reactions
The sonochemical degradation of azobenzene and related azo dyes: Rate enhancements via Fenton's reactions
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DOI：
10.1021/jp992354m
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发表时间：
2000-01-20
影响因子：
2.9
通讯作者：
Hoffmann, MR
中科院分区：
文献类型：
--
作者：
Joseph, JM;Destaillats, H;Hoffmann, MR
在288 K、空气、氧气或氩气饱和条件下，以500 kHz、50 W的声化学降解偶氮苯及其相关偶氮染料（甲基橙子、邻甲基红和对甲基红）的水溶液。通过HPLC-ES-MS鉴定反应产物和中间体。还确定总有机碳（TOC）作为反应时间的函数。我们提出了一个反应机制的基础上观察到的物种和TOC消耗的程度和速度。OH自由基的偶氮双键的加成被认为是氧化键裂解序列的第一步，导致产生羧酸，醌，二氧化碳和硝酸根离子作为主要的降解产物。研究了染料结构和背景气体对声化学漂白速率的影响。邻甲基红的反应速率比其他化合物快约30-40%。这似乎是一个强大的影响，由羧基邻位的偶氮基团。饱和与Ar而不是空气或O-2的伪一级速率常数增加了10%的降解。在Ar-饱和的甲基橙子溶液中，还研究了加入Fe（II）后的声化学漂白和矿化过程的加速。在最佳Fe（II）浓度下观察到反应速率增加3倍。这种动力学效应是定量占一个简单的动力学模型的基础上的Fe（II）与超声化学产生的H2 O2（芬顿的反应）的反应。后一种效果说明了实现声化学降解反应效率的实质性改进的简单方式。
The sonochemical degradation of aqueous solutions of azobenzene and related azo dyes (methyl orange, o-methyl red, and p-methyl red) was performed at 500 kHz and 50 W, under air, O-2, Or Ar saturation at 288 K. Reaction products and intermediates were identified by HPLC-ES-MS. Total organic carbon (TOC) was also determined as a function of reaction time. We propose a reaction mechanism based on the observed species and the extent and rate of TOC depletion. The addition of OH radicals to the azo double bond is considered to be the first step of the sequence of oxidative bond cleavages leading to the production of carboxylic acids, quinones, carbon dioxide, and nitrate ions as the main degradation products. The effects of the dye structures and of the background gas on the sonochemical bleaching rates were also investigated. The reaction rates for o-methyl red were approximately 30-40% faster than those for the other compounds. This appears to be a strong influence by a carboxylic group ortho to the azo group. Saturating with Ar instead of air or O-2 increased the pseudo first-order rate constants for the degradation by 10%. The acceleration of the sonochemical bleaching and the mineralization process upon addition of Fe(II) was also investigated in Ar-saturated methyl orange solutions. A 3-fold increase in the reaction rate was observed at optimal Fe(II) concentrations. This kinetic effect is quantitatively accounted for by a simple kinetic model based on the reaction of Fe(II) with sonochemically produced H2O2 (Fenton's reaction). This latter effect illustrates a simple way of achieving a substantial improvement in the efficiency of sonochemical degradation reactions.