The Remediation Of Lead、Cadmium And PAHs Contaminate Using Green Synthesis Of Iron-based Nanomaterials

In this study,iron-based nanoparticles（H-Fe NPs）were successfully green synthesized using Ilex latifolia Thunb leaf extracts,and H-Fe NPs was used to removal metal ion and PAHs in soil.Hence,this highlights a considerable knowledge gap in the current literature.Here,a functional nanoparticles H-Fe NPs was prepared to address the limitations of chemical synthesis.The key knowledge gaps to be met were（1）the formation of H-Fe NPs using Ilex latifolia Thunb leaf extracts,and（2）the factors influencing removal efficiency of Cr（Ⅵ）,Pb（Ⅱ）and Cd（Ⅱ）,as well as the PHAs,and（3）their removal mechanisms.Firstly,synthesized H-Fe NPs were characterized by various techniques.The size of approximately 100 nm with a capping layer was observed by FTIR and XRD.XPS indicated that the H-Fe NPs contained Fe and Fe₃O₄,as well as a layer covering the H-Fe NPs created by biomolecules from Ilex latifolia Thunb leaf extract.The biomolecules in the extract were analyzed by gas chromatography-mass spectroscopy,and showed that the aldehyde anhydride on polysaccharide as the main reducing agents in the formation of H-Fe NPs,while polyphenols flavonoids was also involved in the reduction,and as a capping agent for H-Fe NPs.Secondly,Iron nanoparticles（H-Fe NPs）were used for the removal of Pb（Ⅱ）and Cd（Ⅱ）.A relationship of competitive removal was observed when Pb（Ⅱ）and Cd（Ⅱ）co-exist.The kinetics followed a pseudo-first-order rate and a pseudo-second-order rate equation,respectively.On the basis of characterization and kinetic data of H-Fe NPs obtained from before and after removing Pb（Ⅱ）and Cd（Ⅱ）,we proposed that simultaneous removal of Pb（Ⅱ）and Cd（Ⅱ）was based on Pb（Ⅱ）occurred through both adsorption and reduction,while the removal of Cd（Ⅱ）occurred through adsorption rather than reductionThirdly,H-Fe NPs was used to an oxidation system to degrade PAHs in soil.The effects of different factors on the degradation were investigated by orthogonal experiment.PAHs degrade improved with the increase of heating temperature and H₂O₂ concentration.H-Fe NPs as a Fenton system to degrade PAHs in soil gave an optimal p H value of 5.The degradation mechanism of PHAs using H-Fe NPs is based on electro-fenton reaction,producing hydroxyl radicals and degrading PAHs as small molecule,which was confirmed by s the characterization of GCMS.Finally,H-Fe NPs was used to simultaneous degrade PAHs and Cr（Ⅵ）in soil.The degradation of Cr（Ⅵ）in soil was improved by single factor analysis including the dosage of the H-Fe NPs,temperature.However,the degradation of anthracene,phenanthrene and pyrene in the soil were 71.4%,73.5%and75.7%,respectively,while the degradation of Cr（Ⅵ）and total chromium were98.3%and 83.2%,respectively.Batch experiments revealed that reduction kinetics followed a pseudo-first-order model,where adsorption fitted well with Freundlich model.The mechanism of H-Fe NPs used to degrade Cr（Ⅵ）in soil was different form of Cr（Ⅵ）adsorption on H-Fe NPs surface,also included both the reduction of Cr（ⅡI）and the formation of hydroxide precipitation.