Degradation Of Atrazine And Thiamphenicol With Molecular Oxygen Activated By Fe@Fe₂O₃ Core-shell Nanowires

In recent years, with the development of economy and the abuse of pesticides and antibiotic, the persistent pollutions accumulate in the environment and then have harm to natural ecological environment as well as the human health. In order to control the water pollution, numerous environmental researchers have been beginning to focus on how to develop efficient and environmentally friendly wastewater treatment method. Over the past 20 years, zero-valent iron （ZVI） has been extensively applied for the remediation/treatment of wastewater contaminated with various organic and inorganic pollutants. But, there are some major limitations in ZVI treatment system, for example, reactivity loss with time due to the precipitation of metal hydroxides, narrow working pH （pH< 3）, and limited efficacy for treatment of some refractory contaminants. To solve these problems, the paper aims to explore the mechanism of enhanced zero-valent iron activate molecular oxygen by Cu²⁺ to degrade pollutant and research the reaction process of typical persistent organochlorine pollutants.Firstly, we found that copper ions could efficiently promote Atrazine degradation with Fe@Fe₂O₃ core-shell nanowires via the molecular oxygen activation processes. The results of electron spin resonance analysis （ESR） and X-ray photoelectron spectroscopic analysis （XPS） to demonstrate that the Fe@Fe₂O₃ core-shell nanowires after the addition of Cu²⁺ could produce more dissolved Fe（Ⅱ）, help the molecular oxygen activation via the single-electron or double-electron transfer route, and then generate more reactive oxygen species such as OH to degrade atrazine. At the same time, these can promote the iron circulation and realize the circle of copper species as well. According to the experimental results, we put forward a most likely atrazine degradation pathway and explored the possibility of complete degradation of atrazine in Fe@Fe₂O₃/Cu²⁺/Air systems.Secondly, we investigated the degradation of thiamphenicol （TAP） with core-shell Fe@Fe₂O₃ nanowires under air or argon atmosphere and compared the defference of degradation pathway between in the two conditions. We found that core-shell Fe@Fe₂O₃ nanowires could degrade thiamphenicol under these two atmosphere, but the degradation rate of thiamphenicol in Fe@Fe₂O₃/Ar system is significantly higher than that in Fe@Fe₂O₃/Air system. After analysis of the intermediate products, we found the degradation mechanism of thiamphenicol under two kinds of atmosphere were not the same:The core-shell Fe@Fe₂O₃ nanowires could aerobic degrade thiamphenicol via molecular oxygen activation to produce hydroxyl radicals; while under argon atmosphere, the zero-valent iron in the center of core-shell Fe@Fe₂O₃ nanowires directly passed electrons to thiamphenicol, and made thiamphenicol reduction and decomposition.In summary, we develops a new way of enhancing core-shell Fe@Fe₂O₃ nanowires to activate the molecular oxygen and deepens understanding of the molecular oxygen activation processes by Fe@Fe₂O₃/Cu²⁺. In addition, pollution of heavy metal Cu could be removed as well as atrazine in the environment by this new method. And we provides a new insight on the aerobic atrazine degradation. The study of thiamphenicol aerobic and anaerobic degradation with core-shell Fe@Fe₂O₃ nanowires give a new idea and method for removing thiamphenicol in the environment.