Synthesis Of Iron Nanoparticles From Pomegranate Leaves And Its Application On Indole Removal

The green synthesis of iron nanoparticles using plant extracts as raw materials has the advantages of simple operation,mild conditions,environmental,non-toxic and ultra-low cost.In addition,the iron nanoparticles prepared by this method have high reactivity and strong stability,which have become a new type of materials.Based on the principles of green synthesis,this thesis prepared iron nanoparticles(PL-Fe NPs)with high activity by using the Pomegranate leaf extracts(PL extracts)as raw materials,and explored their removal performances for indole which is a typical refractory organic pollutant in water.The main contents and results of this thesis are as follows:(1)Prepare PL-Fe NPs with Pomegranate leaf extracts as raw material.Investigate the active constituents of Pomegranate leaf extracts and explore the mechanism of synthesis of PL-Fe NPs.The composition of Pomegranate leaf extracts was separated and identified by Gas Chromatography-Mass Spectrometry(GC-MS)and Liquid Chromatography-Mass Spectrometry(LCMS).The results showed that the main components of PL-Fe NPs synthesis were small molecules such as enols,ketones and amines and organic active components in plant extracts such as ellagic acid,betaine and anthocyanins.Among them,organics containing-OH,=O,and-NH2 mainly act as a reduction,while organics containing C=C and C=N act to stabilize and disperse in the formation of PL-Fe NPs.At the same time,the size,shape and surface functional groups of PL-Fe NPs were characterized.Transmission Electron Microscopy(TEM)images showed that Fe was homogeneously distributed in the sample.The particle size of PL-Fe NPs ranged from 50 to 80 nm,and the surface had a translucent floc-like coating.Combining with the results of FTIR and XPS,the main component in the coating layer was the composition of Pomegranate leaf extracts.According to the above results,the possible synthesis mechanism of PL-Fe NPs was proposed.(2)Indole,the typical refractory and nitrogen-containing heterocyclic organic pollutants in the water,was the object of this study.The removal efficiency of indole was explored by PL-Fe NPs and the thermodynamics and kinetics of reaction were analyzed.The results showed that the removal efficiency of indole by PL-Fe NPs could be stabilized above 50% after 1 h,and the reaction accords with Langmuir isotherm adsorption model as well as the quasi-secondary adsorption kinetics model.Subsequently,the PL-Fe NPs after reaction were characterized by scanning electron microscopy(SEM)and energy dispersive X-ray spectroscopy(EDS).The results showed that the agglomeration of PL-Fe NPs was accompanied by the oxidation of iron elements.Fourier transform infrared spectroscopy(FTIR)and X-ray diffraction(XRD)results showed that the functional groups and coatings on the surface of the particles had changed,indicating that the bioactive components in the pomegranate leaves also played a role in degrading indole.The indole removal process mainly involves adsorption and redox.(3)In order to improve the reactivity of PL-Fe NPs and enhance the removal performance of indoles,PL-Fe/Cu NPs were prepared and characterized by introducing copper(Cu)into the process of green synthesis.The results showed that compared with PL extracts and PL-Fe NPs,the removal efficiency of indole by PL-Fe/Cu NPs was 2.6 and 1.3 times,respectively,at the same conditions for 1 h.The results showed that PL-Fe/Cu NPs were prepared successfully with irregular shape.And elements in the range of 60 ~ 80 nm distributed homogeneously.After reaction with indole,PL-Fe/Cu NPs surface was corroded,with the phenomenon of roughness increases,particles agglomerate,surface functional groups change and stable crystal state which was possible to be reused.Finally,the possible mechanism of PL-Fe/Cu NPs enhanced indole removal was proposed.Nano-scale metallic iron and copper formed numerous tiny galvanic cells in the system,which promoted electron transfer between interfaces,hindered the formation of particles surface oxide layer,enhanced the reactivity of materials,and improved the removal rate of indole.