| With the development of city, the amount of municipal waste becomes more andmore. The municipal waste solid incineration (MWSI) becomes the main method forreducing of volume, harmlessness and turning to resources. However, the compositionsof the municipal waste incineration fly ash are complicated, which contain lots of heavymetals and dissolving salt. If we don’t deal with the fly ash harmlessly, it will bringpollution and harm to our environment.The object of this paper was the fly ash which was taken from a municipal wasteincineration plant in Chongqing. Firstly, the paper did research on the basiccharacteristic of fly ash by surface characteristic analysis and environmental toxicityanalysis. At the same time, washing pretreatment was taken to reduce the chlorinewhich was generated in electrokinetic removal and to improve the leaching qualityremoval efficiency of heavy metals. And then, this paper did the experiments ofwashing pretreatment and enhanced electrokinetic removal by adding citric acid forimproving the leaching quality removal efficiency. The following conclusions aredrawn:Surface characteristic analysis: the median diameter of fly ash was about100μm,80%of those fly ash focued on25~285μm. And the fly ash shaped lump, flake and soon. The particles, which were surface uneven, combined closely and porously.Environmental toxicity analysis: the results of the total content of heavy metals showedthat the total contents of Zn, Pb, Cd, Cu and As were very high, among which, Zn was5847mg/kg, Pb was2628mg/kg, Cd was176mg/kg, Cu was679mg/kg, As was66mg/kg, and all of them exceeded the limit of II-class standard of the Soil EnviromentalQuality Standard (GB15618-2008II). Meanwhile, the leaching quality of Zn, Pb, Cd andCu were126.65mg/L,9.11mg/L,5.20mg/L and6.11mg/L. Only As was not found forits leaching quality was too low. The leaching quality of Zn, Pb and Cd were beyond thestandard value in Standard for Pollution Control on the Landfill Site of Municipal SolidWaste (GB16889-2008).Washing pretreatment: compared to the electrokinetic removal without washingpretreatment, the results of electrokinetic removal with washing pretreatment showedthat the removal efficiency of leaching quality of Cd, Pb and Zn were better, amongwhich, Cd was27.37%, Pb was38.31%, Zn was33.96%. Enhanced electrokinetic removal by adding citric acid experiment: the paper tookthe orthogonal table L9(34), which chose retention time of electrokinetic removal (5days,10days,15days), voltagegradient (1V/cm,1.5V/cm,2V/cm) and concentrationof citric acid (0.05mol/L,0.1mol/L,0.2mol/L) as the factors. The results of those9groups of enhanced electrokinetic removal by adding citric acid experiment showed thatthe best leaching quality removal efficiency of Cd, Pb and Zn achieved55.00%,67.84%,50.77%, respectively. Correspondingly, the average leaching quality of them achieved2.34mg/L,2.93mg/L and62.35mg/L, respectively. Considering the removal efficiencyof Cd, Pb and Zn, the optimal combination of parameters was retention time ofelectrokinetic removal15days, voltagegradient2V/cm and concentration of citric acid0.05mol/L. |
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