Green Synthesis Of Iron-based Nanoparticles By Eucalyptus Leaf And Used To Remove Cr(?) From Aqueous Solution

Green synthesis of iron nanoparticles(Fe NPs)using plant extracts has been an alternative and environmentally friendly technology due to its rapid,nontoxic,and eco-friendly features.In this study,iron-based nanoparticles(EL-Fe NPs)were successfully green synthesized using eucalyptus leaf extracts and were used to remove Cr(?)from aqueous solution.Firstly,the morphology,surface and compositions of synthesized EL-Fe NPs were characterized by various techniques.The size of approximately 100 nm with a capping layer was observed,containing polyphenols and aliphatic acids confirmed by FTIR and XRD.XPS indicated that the EL-Fe NPs contained Fe and Fe3O4,as well as a layer covering the EL-Fe NPs created by biomolecules from eucalyptus leaf extract.Furthermore,the biomolecules identified by GC-MS showed that alcohol phenols and alkylaldehyde acted as reducing agents,while alcohol acids,alkanols,phytols,acetate and aromatic ketones acted as capping agents.It can be concluded that aldehydes,phenols and alcoholic compounds played dominant roles in the synthesis of EL-Fe NPs.Finally,the mechanism for the formation of EL-Fe NPs was proposed.Secondly,EL-Fe NPs were used to remove Cr(?)from aqueous solution under varying experimental conditions,including temperature,pH,initial Cr(?)concentration and EL-Fe NPs loading.Under optimal experimental conditions,84.6%of total chromium and 98.6%of Cr(?)were removed.The results showed the removal efficiency of Cr(?)still reached 55.7%after using four times.The nanoparticles were characterized using a range of techniques such as SEM,EDS,FTIR,XRD and DLS before and after interaction with Cr.This characterization revealed the existence of Cr on the surface of Fe NPs,indicating adsorption of Cr(?)was occurring and a mechanism of Cr(?)removal was proposed.Batch experiments revealed that reduction kinetics followed a pseudo-second order model where adsorption fitted well the Langmuir model(R2=0.9998)with Qm and b being 20.45 mg/g and 3.596 L/mg,respectively.Finally,Fe/Ni bimetal nanoparticles(Fe/Ni NPs)were facilely synthesized by eucalyptus leaf extract.Fe/Ni NPs exhibited a higher Cr(?)removal efficiency than EL-Fe NPs from aqueous solution,with an almost complete removal of Cr(?)in 5 minutes contact time while 78.3%by EL-Fe NPs.SEM-EDS mapping revealed the successful synthesis of Fe/Ni NPs,obvious agglomeration and adsorption of Cr onto Fe/Ni NPs after reaction.XPS results demonstrated the multiple peaks for iron and chromium adsorbed onto Fe/Ni NPs,peaks for Cr(?)and Cr(?)provided support for the reduction and adsorption of Cr(?)by Fe/Ni NPs.Above results indicated that Fe/Ni NPs improved the removal of Cr(?) efficiently.