Study On The Leaching Of Heavy Metals Of Solid Waste Incineration Fly Ash

With the accelerated urbanization process in China, the municipal solid wastegenerated rapid growth. Incineration as a major disposal for waste and fly ash producedby the incineration process also increased significantly. Fly ash due to high levels ofheavy metals and toxic organic compounds, treatment is difficult and has been certifiedas a hazardous waste. Environmental pollution has become a prominent environmentalproblems which caused by improper disposal of fly ash.In this paper, the fundamental properties of MSWI fly ash including particle sizecomposition, microstructure, element composition were analyzed by the instrumentslike X-ray fluorescence spectrum analyzer （XRF）, Scanning electron microscopy （SEM）,X-ray diffraction analyzer （XRD）; And the forms of heavy metals in the fly ash wereextracted by Tessier five-step sequential extraction method; the fly ash were dispelledby HNO3-HF-HCl in order to measure the content of heavy metals; Toxicitycharacteristic leaching procedure（TCLP） method were used to analyze the leachingtoxicity of heavy metals. The physical and chemical characteristics of fly ash can bestudied by the experiments mentioned above.Leaching of the mainly heavy metals in the fly ash was studied by washing andpickling, Simulation the leaching of heavy metals in the analog ordinary naturalenvironment and under extreme conditions,The influence of heavy metals in the fly ashwashout rate was analysis by the leaching temperature, leaching time, solid liquid ratioand other factors. And through comparative analysis of fly ash leaching and understandthe effects of leaching on the basic properties of fly ash.Through all aspects of the study, the following conclusions:（1） Most of the fly ash was fine amorphous particulate. The main elements in thefly ash are O, Ca, Cl, Na, K, S, Si, and Fe. The XRD tests show that the use of fly ash ismainly salt （NaCl）, sylvite （KCl） and gypsum （CaSO₄）. Heavy metals in the fly ash aremainly Zn, Pb, Cd, Mn, Cu, Hg, etc., Zn, Pb, and Cd leaching excessive toxicitycriteria.（2）Large amount of salt （NaCl）, potassium salt （KCl） can be removed bywashing, while remove a few heavy metals in the fly ash. Found washing can remove in exchangeable of heavy metals; basically no affect for heavy metals of other forms byanalysis washed fly ash morphological.（3）Pickling wash about70%of the main heavy metals, different Leaching ratesof different heavy metals is also different.Through the single factor experiment andorthogonal experiment optimum pickling conditions: the ratio of liquid to solid20, acidconcentration:1mol/L, acid: nitric acid, time:20min. The analysis of pickling fly ashshows that pickling can remove the large amount of salt （NaCl）, potassium salt （KCl）,and calcium, and also the heavy metals unstable state. The pickling process leachingmain carbonate-bound,but also a little iron-manganese oxide combined state and boundto organic leaching,acid content of fly ash residue form significantly increased.