Comparative Study On Stabilization Technology Of Several Heavy Metal Contaminated Soils

In recent years,remediation of Multi-heavy metals contaminated soils is increasingly becoming a hot topics in environmental sciences.As an effective remediation technology in the field of heavy metals contaminated soils remediation,the chemical immobilization technology has received more attention due to its simple,economic,and efficiency.The chemical characteristics of different heavy metals are quite different.Single stabilizer is difficult to achieve simultaneous repair of various heavy metals.Therefore,the combination of multiple stabilizers has wide application potential in heavy metal contaminated soil remediation in China.In this paper,the study object is the soil polluted by As,Cd,Pb,Zn in a waste smelter area in southern Hunan Province.The stabilizers suitable for the remediation of As,Cd,Pb,Zn contaminated soil were screened and compounded.The effects of addition ratio,soil and water environment and addition sequence on the effect of composite remediation were analyzed.The speciation of heavy metals in the soil after restoration was studied.The main conclusions are as follows:(1)By comparing the stable soil available content and TCLP concentration,it is difficult for single stabilizer to repair As,Cd,Pb and Zn at the same time.Fe-containing substance(FeSO4 and FeCl3)on the stability of As is better,the highest stabilization rate is 90.50%,but it has a certain activation effect on Cd,Pb and Zn.Alkaline substances(CaO and CaCO3)had better stabilizing effect on Cd and Zn,and the highest stabilization rate reached 75.57%and 91.51%.The stability of CaO on As concentration showed a trend of first strengthening and then decreasing.P-containing substance(KH2PO4 and Ca(H2PO4)2)had the best stabilizing effect on Pb,Ca(H2PO4)2 had the highest stability rate of 91.90%,KH2PO4 had the highest stability rate of 87.41%,but had a strong activation effect on As.(2)By comparing the effects of compound stabilizer ratio,soil and water environment,and adding sequence on the restoration effect,it can be concluded that the effect of compound stabilizer on single heavy metal is low,but As,Cd,Pb and Zn can be repaired at the same time:The mass ratio of 3%FeSO4+2%CaO when the soil water content was 30%had the best repair effect.Stabilizer added step effect is better than added at the same time,it can reduce the antagonistic effects of FeSO4 and CaO on As,Cd,Pb,Zn.When FeSO4 is added first,the stabilization effect of As is better,and when CaO is added first,the stabilization effect is better for Cd,Pb,Zn.(3)The results of heavy metal speciation in stabilized soil indicated that the residual content of As,Cd,Pb,Zn increased significantly after stabilization treatment.According to the correlation analysis.The acid extactable and reducible state of As may be the main factors affecting the change of As available state,and the acid extractable state may be the main factor of the change of leaching concentration.The change of Cd available state and leaching concentration is closely related to the acid extractable,reducible and oxidizable states.The acid extractable and reducible states of Pb may be the main factor of the change in the Pbavailable state,and the acid extractable state may be the main factor of the change of the leaching concentration.The change of the available state and leaching concentration of Zn has a significant correlation with the oxidizable state.