The Remediation Of Cadmium Contaminated Soil Using Green Syrnthesized Iron Oxide

In recent years,soil heavy metal pollution has become the focus of attention in China.The iron oxide nanoparticle-has been considered as one of the best material to recover heavy metal contaminated soil.The aim of this study is to explore the remediation of Cd contaminated soil using green synthesized iron oxide nanoparticles.Firstly,iron oxides nanoparticles(GION)were synthesized by the extract of Excoecaria cochin chinensis Lour.The SEM-mapping,TEM,XRD,XPS and FTIR were used to analysize the properties of GION.The images of SEM-mapping and TEM revealed that GION is a nanoscale iron oxide coated with organic molecules.The spectras of FTIR and XPS revealed that the organic framework of GION includes abundant of oxygen-containing functional groups,such as C-O,C=O,-OH and S=O which will provide active sites for the complexation of Cd2+ in the soil.The results of XRD and EDS further confirmed that the green synthesized GION is a compound consists iron oxide and organic molecules.Secondly,Cd contaminated soils were treated with different dosages(0%,1%,3%,9%)of GION.The immobilization efficiency,and the variations of pH,iron and enzyme were studied.At 120 day,There were no significant difference in pH between the control,1%and 3%GION treatments,whereas the pH of 9%GⅡON treatment was higher than 6.0.The Cd bioavailability was significantly reduced in all GION treatments,where the bioavailable Cd was immobilized by 60%in the 9%GION treatment.The activity of urease,catalase and invertase increased by 187.07%,91.41%and 101.33%respectively after 120 days.The variations of HCl-Fe,(NH4)2C2O4-Fe and DCB-Fe showed that the content of amorphous iron oxide increased with incubation time in the GION treatments.Finally,GION was used to immobilize Cd in six soils with different properties.Additionally,the variations of pH,iron and DOC were investigated.The results showed that the soil pH,DOC,DCB-Fe,(NH4)2C2O4-Fe,and HCl-Fe were increased with increasing GION dosage.The bioavailable Cd was significantly reduced after the application of GION.Moreover,Cd bioavailability under the aerobic condition was much higher than the anaerobic condition.