Study On The Removal Of Heavy Metals From Sewage Sludge By Electrokinetic Device Combining With Coordation And The Features Of Retrieves

As the acceleration of Chinese economic development and its urbanization process, the treatment volume of municipal wastewater has been increasing and therefore correlated sludge output has increased as well in the past decade. Due to the abouchement of industrial wastewater and its enrichment of precipitation, there still exist certain levels of heavy metal in the sludge; and those heavy metal will not only cause secondary pollution in the sludge treatment process but also incur enormous waste of heavy metals. As a result, removing and recycling those heavy metals becomes key essential in the process of reusing sludge and related resources.The municipal wastewater sludge was prepared as the experimental objects, and the self-designed electrokinetic remediation device was used as the experimental facility.The experiment combined electrokinetic remediation with the effect of coordination and chelation was applied in order to remove heavy metals from the sludge. Afterwards, different mixture and concentration of ammonia and ethylene diamine was added as the pretreatment process to increase the removal rate of heavy metals. Finally, products from negative pole was collected in order to characterize so that a more efficient way of removing heavy metals from municipal wastewater sludge can be obtained.1. The electrokinetic remediation experiments indicated that anodic acidification had a moderate exsolution removal rate on heavy metals from municipal wastewater sludge; while isolating the anode chamber (sludge chamber) by using cation exchange membrane can use acidizing effect sufficiently. The removal rates of anodic acidification on Zn, Cu and Pb are 41.63%,26.34% and 35.61%, respectively.2. Cooperation by coordination and chelation experiments indicated that adding ammonia/ethylene diamine had limited impact on pH decrease and electric current density in the electrokinetic process, while it enhanced the trapping and removal rate of heavy metals in the sludge; when ammonia water was added at a ratio of 0.12, removal rates were the highest for Zn and Cu, they are 91.62% and 71.49% respectively. Optimal remediation was achieved at ratio of 0.08 for Pb with a removal rate of 47.85%; and the optimal removal rates for Zn, Cu and Pb were achieved by having a 0.06 ethylene diamine ratio, the removal rates are 87.51%, 67.64% and 57.79%. The enhanced removal effect exerted by coordination and chelation was presumably the result of decreased residual fractions and organic bound fractions, as well as the increased exchangeable fractions of these metals.3. Characterization of sedimentation generated in the cathode region showed that the experimental group with pretreatment by adding ammonia water has relatively low degree of product crystallinity, while at the same time the gap between particles and superficial area are relatively big. Main product ingredients include calcite, germanium deposit and renierite. The group with pretreatment from ethidene diamine has high degree of product crystallinity on its negative pole, the main ingredients of the product include aragonite, basic zinc chloride and domeykite.