Volume 2 · Issue 2 (2025)
Study on the Distribution of Dioxins with Density in MSWI Fly Ash
Ling Qin1,5，Xu Li2, Hong Zhang2, Nian Liu2, Tong Gao2, Zhiguang Zhou3, Dunyu Liu4, Zechuan Teng2
1 China Cooperation Energy Technology (Zhejiang)CO., LTD，Hangzhou 310012, China
2 China University of Mining and Technology, Xuzhou 221116, China
3 National Research Center for Environmental Analysis and Measurement, Beijing 100048, China
4 University of Shanghai for Science and Technology, Shanghai 200093, China
5 China Electric Power Promotion Council, Beijing 100053, China
Abstract: In this paper, the relationship between dioxin content and density in MSWI fly ash was studied. The MSWI fly ash was leached with ammonium chloride, eliminating Ca(OH)2 as well as chlorides, and then separated into different densities using sodium polytungstate solutions as heavy liquids. Carbon content, chemical composition, mineral composition, particle size distribution and concentration and absolute I-TEQ of dioxins in each density fraction were studied. It was found that carbon content is well related to density. With the increase of density, carbon content decreases from 58.47% in the <1.8 g/cm3 fraction to 0.29% in the >2.7 g/cm3 fraction. Chemical compositions have certain degree of differentiation among density. The particle sizes of the two >2.5 g/cm3 fractions were found significantly smaller than the three <2.5 g/cm3 fractions as a whole. The dioxin concentration in each fraction was found to decrease with density, except the <1.8 g/cm3 fraction, indicating that much more dioxins exist in residual carbon than injected activated carbon. The absolute I-TEQ of dioxins was found far exceeding the permit content in the fraction even with lowest carbon content, which indicates that froth flotation alone cannot attain the permit content of dioxins in the tailing. Prospective measures were discussed.
Keywords: MSWI Fly Ash; Dioxin; Carbon Content; Density separation
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