【作者】 郭加会；

【导师】 郭建维； 刘鸿；

【作者基本信息】 广东工业大学 ， 应用化学， 2012， 硕士

【摘要】 近年来,随着各国工业化进程加快,水污染问题日趋严重,已对人类的生存安全构成重大威胁,成为人类健康、经济和社会可持续发展的重大障碍。硝基苯作为一种重要的化工生产原料,其毒性强,并具有分子结构稳定,难于微生物降解,不宜直接采用生物降解法降解的特征。已经成为大气、水体及土壤的典型污染物,硝基苯的净化处理已是摆在环境工作者面前刻不容缓的问题。零价铁还原技术可有效处理硝基苯,产物为苯胺,苯胺毒性较低、较易生物降解。但普通铁粉活性位点少、反应速率慢、效率低、用量大,造成了资源浪费。纳米零价铁粒径小、比表面积大、活性高,在废水处理中有着广泛应用,已成为水体修复技术研究的热点。液相还原法是最常用的制备纳米零价铁的方法,但目前的制备工艺难以得到纯净且干燥的纳米零价铁粉,材料中特别是材料表面含有氧化物薄膜,阻碍还原过程中电子的传输,不利于反应。材料中未干燥完全的水分会加速纳米零价铁的氧化,不利于其保存。本文采用二次还原技术可制备出纯净的纳米零价铁粉,表面无氧化层薄膜,有利于电子的传输及纳米零价铁的保存。本文利用二次还原技术,先将FeSO4液相还原为纳米零价铁,然后用高温氢气对其进行二次还原和干燥,高温氢气在纳米零价铁制备过程中既有二次还原作用又有干燥作用。本文还使用XRD、SEM、TEM、BET等仪器对新制备的纳米零价铁的微观形貌及化学组成进行表征,并对新制备的及干燥条件下保存了两个月的纳米零价铁粉进行对比分析。最后探索了自制纳米零价铁在降解水体中硝基苯的应用研究。主要结论如下：(1)使用硼氢化钠溶液将硫酸亚铁溶液还原为纳米零价铁,然后使用400℃高温氢气将纳米零价铁二次还原可以制得纯净的纳米零价铁粉。经过表征,自制的纳米零价铁粉不含氧化物杂质,其表面没有物氧化物薄膜,其粒径大小为90nm～100nm,纳米零价铁颗粒之间呈链状排列。(2)纳米零价铁可以有效地还原降解硝基苯,在硝基苯浓度为0.01mmol/L的溶液中,纳米零价铁投加量只需56mg(10mmol/L),硝基苯即可60min内被完全还原,还原反应的中间产物为亚硝基苯和苯基羟胺,最终产物为苯胺。(3)纳米零价铁还原硝基苯反应中,溶液pH值对反应具有明显的影响,在pH值范围为2-9范围内,纳米零价铁还原硝基苯反应速率随pH降低而增大,在pH值较低情况下,纳米零价铁与H+反应生成H2释放,会使反应效率略有下降。(4)干燥条件下保存了两个月的纳米零价铁粉,其化学组成和结构均未发生变化,还原降解硝基苯的速率和效率未受影响。更多还原

【Abstract】 In recent years, water pollution problem has been growing incleasingly serious along with the industrialization advancement, which threats the human health, economic and social sustainable development of the major obstacles. In water pollutants, Nitrobenzene is a kind of widely used synthetic organic compounds in the world, Studies show that the molecular structure of nitrobenzene is very stable, difficult to biodegrade, So it is directly using biological degradation. Both gaseous and liquid of nitrobenzene are highly toxic, Nitrobenzene in the environment which mainly comes from the effluent of chemical and dye works, has caused grave damage to the air,water resources and soil environment. Therefore, how to control the nitrobenzene and aniline pollution has been an urgent problem all over the world.Zero-valent iron can effectively reduce the nitrobenzene in groundwater with the product of aniline, which of toxicity is lower than nitrobenzene, at the same time, the biodegradation of aniline is easier than nitrobenzene,but the iron activity is small, reaction rate is slow as well as low efficiency, large in amount, and a waste of resources. The advantages of nanometer zero-valent iron are small particle size, large specific surface area, high surface activity, it has a wide range of applications in water treatment, and it has become the research hotspot of groundwater remediation technology. Liquid phase reduction method is the most commonly method used in the preparation of nanometer zero-valent iron, but the current preparation process is difficult to abtain clean and dry nanometer zero-valent iron. Material, especially the surface of material usually contain oxide film, which hinder the reduction process of electron transfer, and is not conducive to the reaction. The moisture of not drying completely will accelerate the oxidation of nanometer zero-valent iron, and is not conducive to the preservation of nanometer zero-valent iron. This paper adopts two times reduction technology for preparation of pure nanometer zero-valent iron, which has no oxide film in the surface, and it is conducive to the electron transfer and storage.In this paper, twice reduction technology is used to reduce FeSO4solution into nanometer zero-valent iron, then using high temperature hydrogen deal with nanometer zero-valent iron, high temperature hydrogen during the process of the preparation is not only a twice reduction process but also a drying process. XRD, SEM, TEM, BET and other instruments are used to characterize the micro structure and chemical composition of nanometer zero-valent iron. XRD analysis chemical composition of nanometer zero-valent iron, which is saved in dry conditions for two months, finally the self-made nanometer zero-valent iron is used for degradation of nitrobenzene ni wastewater, the main conclusions are as follows:(1) Ferrous sulfate solution can be reducted as nanoscale zero valent iron, Thereafter, nanoscale zero valent iron was secondly reduced by hydrogen with high temperature400℃. the products were nanoscale zero valent iron power. Through characterizing, self-prepared nano zero valent iron powder did not containt oxide impurities and surface oxide film, the particle size was from90nm to100nm, the arrangement of particle was chainlike.(2) The nanoscale zero valent iron power chould reduce nitrobenzene, with the concentration of nitrobenzene is0.01mmol/L, only need10mmol/L nanoscale zero valent iron, nitrobenzene chould be Degradated Completely just in60min, Intermediate product were nitrosobenzene and phenylhydroxylamine, final product was aniline.(3) The value of pH had a obvious effect for the reaction of nanoscale zero valent iron reduce nitrobenzene. During pH in the range of2to9, the reaction rate of nano zero valent iron reduct nitrobenzene becomed fast as the value of pH reduced. If the value of pH was too low, nano zero valent iron would react with H+and generate H2, this would waste zero valent iron.(4) Nanometer zero-valent iron in drying condition for two months, which chemical composition and structure were not changed, had the same reaction rate and efficiency of reductive degradation.更多还原