氨基羧酸类配体强化Fe^(2+)活化分子氧降解对硝基酚

Effect and mechanism of Fe^(2+)-activated molecular oxygen advanced oxidation of p-nitrophenol enhanced by aminocarboxylic acid chelating agents

本研究构建了Fe^(2+)/O_(2)/乙二胺四乙酸钠(EDTA)、Fe^(2+)/O_(2)/次氮基三乙酸钠(NTA)、Fe^(2+)/O_(2)/乙二胺二琥珀酸(EDDS)高级氧化体系,选取对硝基酚(PNP)为目标污染物,探究3种体系降解PNP的性能,着重分析Fe^(2+)/O_(2)/EDTA、Fe^(2+)/O_(2)/NTA体系的ROS产生过程及对污染物的降解贡献,阐明氨基羧酸类配体的强化效果及机制.结果表明,Fe^(2+)/O_(2)/EDTA、Fe^(2+)/O_(2)/NTA体系的最佳降解条件均为pH=3、Fe^(2+)与配体物质的量比为1:1,PNP降解率分别为50.8%、81.2%.Fe^(2+)/O_(2)/EDTA体系生成的ROS为HO·与O_(2)^(·−),ROS产生途径存在单电子转移(O_(2)→O_(2)^(·−)→H_(2)O_(2)→HO·)、双电子转移(O_(2)→H_(2)O_(2)→HO·)途径,部分PNP被O_(2)^(·−)还原为对氨基酚,大多数PNP及其还原产物被HO·氧化生成对苯二酚和对苯醌,之后氧化开环;Fe^(2+)/O_(2)/NTA体系生成的ROS主要是HO·,体系ROS产生途径主要为双电子转移途径,PNP被HO·直接氧化,生成对苯二酚和对苯醌,之后氧化开环.此外探究了两种配体活化能力的差异及机制.

Three advanced oxidation systems,including Fe^(2+)/O_(2)/disodium ethylenediamine tetraacetate(EDTA),Fe^(2+)/O_(2)/trisodium nitrilotriacetate(NTA)and Fe^(2+)/O_(2)/N,N'-Ethylenediamine disuccinic acid(EDDS)systems,were constructed to investigate the effectiveness of the 3systems focr removing target contaminant p-nitrophenol(PNP).The generation process of reactive free radicals,and their contribution of pollutants degradation as well as the enhancement of aminocarboxylate ligands and its underlying mechanisms were also studied and clarified in the system of Fe^(2+)/O_(2)/EDTA and Fe^(2+)/O_(2)/NTA.The highest PNP degradation efficiency of 50.8%and 81.2%were achieved in the system of Fe^(2+)/O_(2)/EDTA and Fe^(2+)/O_(2)/NTA,respectively,under pH=3 and the molar ratio of Fe^(2+)to ligand of 1:1.The reactive free radicals generated by Fe^(2+)/O_(2)/EDTA system were HO·and O_(2)^(·−),with two generation pathway(one-electron transfer mechanism:O_(2)→O_(2)^(·−)→H_(2)O_(2)→HO·;two-electron transfer mechanism:O_(2)→H_(2)O_(2)→HO·).initial PNP was reduced to p-aminophenol by O_(2)^(·−);PNP and its reduction products were oxidized by HO·to hydroquinone and p-benzoquinone,followed with the ring structure breakage.HO·was the major reactive free radicals generated by Fe^(2+)/O_(2)/NTA system by two-electron transfer mechanism.PNP was directly oxidized by HO·to hydroquinone and p-benzoquinone,followed with the ring structure breakage.The mechanisms of the difference in the activation capacity of the two ligands were studied.