二价铁离子对零价铁还原硝基苯的影响

为了解地下水环境中铁离子对零价铁(zero valention)还原作用的影响,采用批次实验,研究不同质量浓度二价铁离子对ZVI还原硝基苯的影响,利用HPLC和GC-MS作为分析工具,观测反应过程中硝基苯的质量浓度,同时跟踪溶液中Fe2+、pH、ORP的变化.结果表明,有无Fe2+存在,硝基苯均可被ZVI还原为苯胺,Fe2+没有改变还原产物;溶液中投加Fe2+后,ZVI还原硝基苯的反应速率明显加快,溶液中Fe2+对于还原反应起促进作用;溶液中Fe2+对ZVI体系pH起缓冲作用,含有Fe2+的ZVI体系ORP下降明显.反应动力学分析表明,硝基苯的还原反应符合假一级动力学模型,表观速率常数kobs值随Fe2+质量浓度的升高而增加,Fe2+离子的存在有助于ZVI对硝基苯的还原.

Effects of ferrous ions on reduction of nitrobenzene by zero-valent iron

To find out the effect of ferrous ions (Fe2+) on the reduction of zero-valent iron (ZVI) in groundwater,the reduction of nitrobenzene (ArNO2) was investigated in a ZVI system (Fe0) with the addition of Fe2+ with various concentrations adopting batch tests. Using HPLC and GC-MS as analytical tools,the concentrations of ArNO2 were monitored during the reaction process,and the variations of Fe2+,pH as well as ORP during the reaction were examined. The results indicate that the reductive product of nitrobenzene is not changed with the addition of Fe2+,and ArNO2 is still reduced to aniline by Fe0. The reductive reaction rate of ArNO2 is apparently enhanced by the addition of Fe2+. Fe2+ has a capacity of buffering in the ZVI system,and the oxidation-reduction potential (ORP) of ZVI system containing Fe2+ is decreased clearly. The reductive reaction can be described by a pseudo-first-order kinetic model,and the observed pseudo-first-order rate constants (kobs) is increased with the increasing Fe2+ concentration,which indicates that the presence of Fe2+ accelerates the reduction of ArNO2 by Fe0.