Study On Basic Characteristic And Electrokinetic Removal Technology Of Municipal Solid Waste Incinerate Fly Ash

With the development of incinerate technology, the amount of the municipal wastesolid incineration （MWSI） fly ash grows fast, which contains lots of heavy metals withhigh leaching value. Therefore, the heavy metals can easily release to soil and wateraround, threaten to people’s heath, once the fly ash is poorly disposed. This researchaimed at the MWSI fly ash in Chongqing, studied the basic characteristic,environmental toxic and the environmental active feature of the sample fly ash. Studythe feasibility of electrokinetic removal technology by analysis the removal efficiencyof heavy metals in fly ash.To begin with, this research made some conclusions by taking advantage of theanalysis of the surface characteristic, environmental toxic and the environmental activefeather of the sample fly ash:â‘ the diameter of fly ash is small, median diameter isabout100um, the fly ash’s diameter centers on15²00um, parts of small fly ash caneasily fly to the air and result to pullote; The main elemental composition in fly ashwere O、Ca、Cl、K、Na、S、Si and so on, and the main heavy metals were Pb、Zn andCu; what’s more the heavy metals are main exit with the form of chloride, oxidate andsilicate; meanwhile, the fly ash was like small ball and it was very small, which maymake fly ash a high leaching value; fly ash were irregular.â‘¡The total contentexperiment of fly ash showed the content of heavy metals in fly ash is very high, amongwhich, Zn was5239.5mg/kg, Pb was2560mg/kg, As was66.38mg/kg, Cu was632mg/kg and Cd was116.95mg/kg, which were far beyond the solid background value ofheavy metals in Chongqing. The leaching toxic experiment of fly ash showed theleaching value of Zn, Pb and Cd were far higher than the standard value in ‘Standard forPollution Control on the Landfill Site of Municipal Solid waste’, and, the value of Pband Cd were even above ten times higher; The subsequent extract experiment of fly ashshowed that the content of Cd, Zn, Pb and Cu in the first step is high, expecial, thecontent of Cd, the percent value achieved57.3%. Meanwhile, the content of As in thelast step is high, achieved94%in total content, which indicate As has a very smallleaching value. This research concluded that As is stable and leach less in low pH, whilethe other heavy metals are dangerous in environment.In the second place, in the process of electrokinetic removal experiment, the use ofcation exchange membrane solved the ‘pH effect’. The final result is thatâ‘ the highest efficiency of Cd is34%, the highest efficiency of Zn is28.9%;â‘¡the leaching valueof Zn after experiment is lower than the standard, which is100mg/L, while the leachingvalue of Pb and Cd has reduced40%,50%separately;â‘¢the result of optimized BCRexperiment showed that the forms of heavy metals are more or less changed from stableform to unstable form.In the third place, after enhanced electrokinetic removal experiment, the removalefficiency and leaching value of heavy metals in fly ash were improved. The removalefficiency of heavy metals near anode was the highest, that of Zn, Pb, As, and Cd was40%、32%、14%and45%respectively. Besides, the leaching value of Pb and Cddecreased more.This research proved that the electrokinetic removal technology is feasible to flyash, but the removal efficiency should be improved. The leaching value of Zn reachedthe standard while Pb and Cd do not after experiment. Meanwhile, the content ofwater-solubility irons, such as Cl-, SO₄^2-, K-were high, which greatly decreased thecurrent efficiency, therefore, pretreatment to fly ash is necessary. And, the mechanism ofthe release of heavy metals in fly ash, mechanism of move and new experiment deviceshould be studied in the further research to promote the development of electrokineticremoval technology.