Study On Electrokinetic Removal And Recycle Of Heavy Metals From Sewage Sludge Using Double-deck And Double-anode Electrokinetic Reactor

With the rapid development of China’s economy and the process of accelerating urbanization,the output of sewage sludge in our country increases rapidly.Due to the infusion of industrial waste water,there are a certain amount of heavy metals in sludge.They will not only seriously affects the safe application of subsequent disposal methods on sludge such as agricultural using,composting,incineration and landfill etc,but also cause huge waste of resources and economic losses,unless the heavy metal in sludge can be proceed and recycled safely.In order to explore the feasible way that could be suitable for the future industrial application,we designed a self developed double-deck and double-anode electrokinetic reactor to remove and recycle heavy metals in sewage sludge with ethylenediamine as complexing agent,and characterize the cathode precipitation.（1）Based on the comprehensive analysis of research status and limitation of the existing electrolytic devices,we designed a double-deck and double-anode electrokinetic reactor.The results of preliminary experiments show that the capacity of the new device（9 L）is much larger than that of old one（2.5L）,in addition,the removal rate of Cu increased from 67.64%to 76.02%,the removal rate of Pb increased from 57.79%to 60.23%,and the removal rate of Zn also increased from 87.51%to 89.13%.So the new device can significantly improve the removal efficiency of heavy metals in sewage sludge and has a larger single processing quantity.（2）The electrokinetic remediation experiments indicated that the best current density of this device is 1.2mA/cm² considering both the removing effect and economic benefit.In the three groups of experiments,the ultimate removal rate of Zn,Cu get increased with the increase of current density,however,ultimate removal rate of Pb and Cr decreases firstly and then increases with the increase of current density（3）Synergy electric experiments indicated that:1)the addition of ethylenediamine can enhance the remove and recycle rate of heavy metals in sewage sludge.2)The optimal removal rates for Zn,Cu、Cr and Pb were achieved by when ethylene diamine ratio at 0.06.3)In the process of electrolysis,three was no obvious competitive relationship between Cu,Pb and Cr,but they compete with Zn to some degree.（4）The characterization of cathode sedimentation indicated that cathodic precipitation mainly contain nine kinds of metal elements:Zn,Fe,Cu,Cr,Na,Ca,K,Mg,Pb,and three kinds of nonmetal elements:Si,Cl and S.The content sequence is Zn>Fe>Cu>Cr>Na>Ca>K>Si>Mg>Pb>Cl>S.The dried cathode deposits are most likely to contain ZnO、ZnS、CuS、CuO、PbS、PbO₂ and KxCrO₂,Zn exists mainly in the form of ZnO and ZnS,Cu exists mainly in the form of CuO and CuS,Cr exists mainly in the form of KxCr0₂,and the least Pb mainly exist in the form of PbS and PbO₂.