Green Synthesis Of Iron Nanoparticales Using Tea Leaves For Removal Of Hexavalent Chromium And Lead In Waste Water

The preparation of iron nanoparticles was varied and developed rapidly. Biological method has become a focus of scholars because of its wide raw material sources, modest reaction conditions, weak aggregation, mild reaction conditions, and few by-products. The biosynthesis iron nanoparticles is still in its initial stage, and many descriptions of mechanism still is a theoretical guess or inference. Therefore, it’s a new way for iron nanoparticles development and to solve the pollution of heavy metals by selecting biomass reasonably, thoroughly analyzing the main functional components, and researching the reaction mechanism, to optimize nanoparticles’ morphology and size, and to improve yields.Green iron nanoparticles(BT-Fe NPs) were prepared by brick tea. Then, the BT-Fe NPs was characterized by UV-Vis、XRD、TEM、EDX. And the particle was modified by loading on the attapulgite(ATP) to synthesize a new iron nanoparticles-green iron nanoparticles/ attapulgite(BT-Fe NPs/ATP). And researcher estimate the removal efficiency of Cr(Ⅵ), Pb(Ⅱ) by them. The effect of different factors on the removal efficiency was investigated. And explore the mechanism of heavy metal removed by BT-Fe NPs. The experimental results show that:(1)BT-Fe NPs is amorphous spherical with the particle size of 100~200nm. It was mainly in the form of magnetic hematite(γ-Fe2O3), magnetite(Fe3O4) and iron hydroxide. Nanoparticle was coated with C-N, C-O,-OH.(2)At 25 ℃, p H = 4.0, initial concentration of Cr(Ⅵ) for 20 mg/L, the removal rate of Cr(Ⅵ) reached 96.3% by BT-Fe NPs after 90 min. Because of enwrapped organic composition in brick tea extract, the oxidation resistance of BT-Fe NPs is better than Na BH4-Fe NPs made by chemical method. At room temperature, initial concentration of Pb(Ⅱ) for 10 mg/L, the p H for 7, the amount of BT-Fe NPs/ATP is 0.1 g, the removal rate of Pb(Ⅱ) can reach 99.8% after 90 min.(3)After modification, BT-Fe NPs/ATP still keeps the basic layered-chain structure of ATP, and it has larger surface area. Green iron nanoparticle that is approximate an ellipsoid loads in parallel ATP bundles dispersedly, and particle size is about 200~500nm, and the agglomerate reduces significantly.(4)C-N perssad and Fe-O keys had a leading role in the process of removal of Cr(Ⅵ), Pb(Ⅱ). Heavy metal ions were adsorbed on the surface of nanoparticles by the organic groups in the tea, then reduced by Fe-O keys. It shows that it is a complex physical and chemical process included physical adsorption and reduction in process of removal of Cr(Ⅵ), Pb(Ⅱ) by green iron nanoparticles.