College of Resource and Environment, Shaanxi University of Science and Technology, Xi'an 710021, China.
Chemosphere. 2013 Jan;90(2):143-9. doi: 10.1016/j.chemosphere.2012.06.018. Epub 2012 Jul 13.
Three azo dyes (Methyl Orange, Direct Brown and Direct Green) were treated by catalytic wet air oxidation (CWAO) with the catalysts CuO/γ-Al(2)O(3) prepared by consecutive impregnation. The relationship of decolorization extent, chemical oxygen demand (COD) removal extent and total organic carbon (TOC) in dye solution were investigated. The results indicated that the CuO/γ-Al(2)O(3) catalyst had excellent catalytic activity in treating azo dyes. Almost 99% of color and 70% of TOC were removed in 2h. The high removal extent of color and TOC indicated that the CWAO obtained perfect decomposition for pollutants. The degradation pathway of azo dyes was analyzed by UV-Vis, FTIR and MS. According to the examined results, the hydroxyl ((·)OH) radicals induced strong oxidizing effects in the target solution and destroyed the chromophoric groups of azo-benzene conjugated of the molecular structure. Considering characteristics of the dye structure, the azo bond (-N=N-) would first be attacked by the hydroxyl radical and other free radicals. With the continuous oxidization and the long reaction time at high temperature, these intermediates could be oxidized to the final oxidation products, such as water and carbon dioxide.
三种偶氮染料（甲基橙、直接棕和直接绿）用通过连续浸渍法制备的氧化铜/γ-氧化铝（CuO/γ-Al(2)O(3)）催化剂通过催化湿式空气氧化（CWAO）进行处理。考察了染料溶液中脱色程度、化学需氧量（COD）去除程度和总有机碳（TOC）之间的关系。结果表明，CuO/γ-Al(2)O(3)催化剂在处理偶氮染料方面具有优异的催化活性。在 2 小时内，颜色几乎去除了 99%，TOC 去除了 70%。高的颜色和 TOC 去除程度表明 CWAO 对污染物进行了完美的分解。通过 UV-Vis、FTIR 和 MS 分析了偶氮染料的降解途径。根据检查结果，羟基（·OH）自由基在目标溶液中产生强烈的氧化效应，破坏了分子结构中偶氮苯共轭的生色基团。考虑到染料结构的特点，偶氮键（-N=N-）首先会受到羟基自由基和其他自由基的攻击。随着氧化的不断进行和高温下的长时间反应，这些中间体会被氧化为最终的氧化产物，如水和二氧化碳。
