反应气氛对绿色合成纳米铁的组分及其活性的影响

Effect of the reaction atmosphere on component and reactivity of green synthesis of iron nanoparticles

成本低廉和无二次污染的"绿色"合成纳米材料是发展原位纳米环境修复技术的前沿研究课题之一.本文以绿茶提取液为还原剂和稳定剂进行"绿色"合成纳米铁,探讨在不同的气氛下"绿色"合成的纳米铁颗粒的主要成分,以期为调控合成纳米铁系材料提供基础研究.首先,利用扫描电子显微镜(SEM)、X射线能谱(EDS)、X射线光电子能谱分析(XPS)和傅里叶变换红外光谱(FTIR)等表征手段对不同反应气氛下合成的纳米铁颗粒的表面微观形貌、尺寸和价态结构进行分析.结果发现,在通入N2情况下,合成的纳米铁颗粒粒径为(84.7±11.5)nm,其主要成分以纳米零价铁为主;在通入空气情况下,合成的纳米铁粒径为(117.8±26.2)nm,其主要成分是纳米零价铁、氧化铁和四氧化三铁的混合物;通入O2时,合成的纳米铁粒径为(141.2±26.3)nm,其主要成分以四氧化三铁为主.其次,评价在不同气氛条件下合成纳米铁颗粒对去除亚甲基蓝(MB)的反应活性.结果表明,在反应温度313 K下降解初始浓度为50 mg·L-1的MB溶液,反应5 min时已达到平衡,通入N2合成的纳米铁降解MB,去除率高达98.7%,而通入O2合成的纳米铁反应效率低,对MB的去除率仅为65.3%.最后,从以上发现提出不同气氛下可以调控"绿色"合成的铁系纳米材料成分,从而导致不同的纳米修复环境中污染物的能力.

Green synthesis of nanoparticles has received extensive attention for in situ environmental remediation due to its low cost and biocompatibility.In this study,the composition of iron-based nanoparticles( Fe NPs) at various atmospheres using green tea extract as reducing and stabilizing agent was investigated to understand the influence of the atmosphere during the plant-mediated synthesis. Firstly,SEM,EDS,XPS and FTIR were employed to confirm the morphology,size and surface composition of Fe NPs. In a nitrogen atmosphere,the size of as-prepared product is( 84.7±11.5) nm and the main component is zero-valent iron. On the other hand,the product synthesized with air has a large size range of( 117.8±26.2) nm,including zero-valent iron,iron oxide and iron hydroxide. Meanwhile,in an oxygen atmosphere,the product with the largest size range of( 141.2±26.3) nm mainly contains iron oxide. Secondly,the activities of Fe NPs at various atmospheres were tested by removal of methylene blue( MB). The reaction process reached equilibrium within 5 minute at a temperature of 313 K and an initial concentration of 50 mg·L-1MB. The removal efficiency of Fe NPs by passing N2 is more than 98.7% and the removal efficiency is only 65.3% using Fe NPs under O2. Finally,we proposed that the composition of Fe NPs can be controlled at various atmospheres,thereby tuning the removal capacity for different contaminants in remediation.