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Fly ash sample collected from a facility which treat urban waste with combustion, the major physio-chemical features of which were studied including chemical composition; the heavy-metal content, speciation as well as leaching toxicity; surface morphology analysis and composition within the mineralogical phase using XRF, ICP, SEM and XRD. Results from the experiments indicate that the primary elements contained in the fly ash are Cl, K, Na, S, Ca and Si, and Zn, Pb and Cu all belong to the category of primary heavy metals. Crystalline phase’s analysis demonstrated that the fly ash is primarily composed of some soluble salts like KCl, NaCl and some crystals as SiO2 and CaSO4. In terms of morphology of the fly ash, it is irregular, along with aggregation of both amorphous structures and polycrystalline. This structure makes the fly ash strong adsorption capacity on heavy metals, dioxin and other pollutants. The leaching toxities of all the observed elements of Zn, Cu, Pb, Ni, Cd have all exceeded the limits of Landfill Waste Requirement in China (GB16889-2008) and the leachate concentration realated to Pb, Zn, Cd have also exceeded the limitation of Chinese Identification Standard for Hazardous Wastes (GB5085.3-2007). According to the results of sequential extraction, high mobililty of Cd, Pb and Zn has been discovered in this research. Consequently, this could pose a threat to the surroundings when MSWI fly ash is landfilled or reutilized. KEYWORD: fly ash; basic characteristics; heavy metals; leaching toxicity; speciation 4th International Conference on Mechanical Materials and Manufacturing Engineering (MMME 2016) © 2016. The authors Published by Atlantis Press 563 2.2 Characterization Composition and content In this research, XRF with apparatus ZSX PrimusII assisted with determining the composition and content of the fly ash. This device is a WDXRF spectrometer with a Rh anode end-window Xray tube equipped with 30 μm Be window. The results were expressed in the percentage of corresponding oxides. Content and leaching characteristic of heavy metals. For the sake of acquiring relatively more precise heavy-metal concentrations, microwave together with digesting acid (HNO3/HCl/HF) in three steps were used to dissolve the fly ash samples. Then ICP (1000II) assists with the determination of the content of heavy metals. Heavy-metal leaching toxicity determination is in accordance with the Chinese Solid waste-Extraction Procedure for Leaching Toxicity-Acetic Acid Buffer Solution Method (HJ/T 300-2007). Firstly, 75.0 g dried sample was poured to deionized water of 750 mL in a 1L bottle made of polyethylene with a solid to liquid ratio of l:10; subsequently, the polyethylene bottle was fixed in a flip oscillator. Then, it was agitated at a speed of 30±2 r/min for 18 h in succession. After all these, it was placed to stand for 0.5 h; thirdly, vacuum filtration, with the assistance of a 0.45μm-micropore filter membrane, has helped with separating the component which is soluble. Finally, the filtrate was adjusted to a required volume and then the heavy-metal concentrations contained could be detected with the assistance of ICP. Chemical speciation of heavy metals Five different fractions, which are named as exchangeable fraction (F1), fraction bound to carbonate (F2), fraction bound to Fe-Mn oxides (F3), fraction bound to organic matters (F4) and residual fraction (F5) were classified so as for determining heavy-metal partitioning. Experimental conducting conditions abide by the details demonstrated in Table 1. Centrifuging would accomplish the process of separating when each one step of extraction is over; and the residual solids were utilized for the successive extractions. For further analysis, 0.5 mL HNO3 should be added to preserve the supernatant. Table 1 Experimental conditions in sequential extraction Chemical fraction Separation conditions 1. Exchangeable 8 mL 1.0 mol/L MgCl2 adjusted to pH=7.0, successive oscillation for 1 h at 25°C 2. Bound to carbonate 1.0 mol/L NaAc adjusted to pH=5.0 with 8 mL HAc, successive oscillation for 5 h at 25°C 3. Bound to Fe-Mn-oxides 0.04 mol/L NH2OHHCl in 25% 25 mL HAc, occasional oscillation for 6 h at 96±2°C 4. Bound to organic matters 3 mL 0.02 mol/L HNO3 + 5 mL 30% H2O2 adjusted to pH=2.0 with HNO3, occasional agitation for 2 h at 85±2°C. 3 mL 30% H2O2 adjusted to pH=2.0 with HNO3, occasional agitation for 3 h at 85±2°C.After cooling to room temperature, 5 mL 3.2 mol/L NH4Ac in 25% HNO3, continuous agitation for 0.5 h. 5. Residual digesting with an HF-HClO4 mixture, and then diluted with 1 mol/L HCl SEM observation: Morphology of the fly ash was observed with the assistance of SEM. The samples were coated with Au and then analyzed with the means of a scanning electron microscope Hitachi S-4800 equipped with a Genesis XM2 energy-dispersive spectrometer. XRD analysis: The crystalline phases of the fly ash could be analyzed by XRD. XRD analysis was conducted with a X ́ Pert PRO rotating-target X-ray diffractometer (4 kV, 30 mA). The samples were put into a sample rack with zero background and the experiments were conducted with the scanning 2θ angles from 20° to 80°, a step interval of 0.02° and a scan speed of 2°/min. All of the the concentrations mentioned above as well as all the features were regarded as the average values of three parallel experiments. 3 RESULTS AND DISCUSSION 3.1 Composition and content Generally, the MSWI fly ash composition is determined by the composition of combusted waste, technology of incineration (equipment for controlling the air pollution, filters’ separation efficiency, etc.) and the conditions of redox (K. Martin, 2012). Chemical composition of the fly ash measured by XRF is listed in Table 2. The results demonstrate that Cl, K, Na, S, Ca and Si are the primary elements in the fly ash. Particularly, Cl, Na2O, K2O and SO3 are found in a relatively high content of 18.95%, 16.61%, 15.08% and 14.36%, respectively. High content of chlorine has a direct relationship with the PVC in waste plastics and NaCl in kitchen garbage, which makes up most of the chlorides in MSW. Unfavorable, from the opinion of applying it in concrete, is particularly a relatively great amount of sulfates and chlorides. The sulfates could make the concrete strength decline, while chlorides accelerate

Study on the basic characteristics of MSWI fly ash in northern China