超声波/零价铁体系降解五氯酚的机理

The mechanism of degradation of pentachlorophenol in an ultrasound/zero-valent iron system

在超声波/零价铁体系中,以五氯酚为目标污染物,分别对各种形态铁离子浓度和羟基自由基表观生成率进行了定量测定,探讨了超声波与零价铁的协同作用机理.结果表明,在超声波/零价铁体系降解五氯酚过程中,同时存在超声波的羟基自由基氧化作用和零价铁的还原作用,其中超声波的羟基自由基氧化作用占主导,零价铁大大地促进了该体系羟基自由基的生成.同时,采用气相色谱-质谱联用仪测定中间产物,并结合相关研究推测,超声波/零价铁降解五氯酚主要是通过羟基自由基的氧化脱氯、五氯酚氧自由基的自身耦合,以及零价铁的还原脱氯3种降解途径完成的.

The synergistic mechanisms of degradation of pentachlorophenol （PCP using a combination of ultrasound and zero-valent iron were investigated. The iron ion concentrations and apparent production of hydroxyl radicals in aqueous solution were quantitatively analyzed. The degradation of PCP is attributed to the oxidation of hydroxyl radicals formed from the ultrasound and the reduction of iron in the ultrasound/zero-valent iron system （Ultra/Fe^0）. The oxidation of hydroxyl radicals plays a dominant role in the process. The apparent production of hydroxyl radicals is markedly advanced by the iron powder. Meanwhile, the intermediate products of the degradation process were detected using a gas chromatograph-mass spectrometer. （GC/ MS） Three pathways of the oxidative dechlorination of hydroxyl radicals, the coupling of pentachlorophenoxy radicals and the zero-valent iron dechlorination of pentachlorophenol are proposed on the basis of the maior intermediates and correlation studies.