4.7 Article

Preparation of municipal solid waste incineration fly ash-based ceramsite and its mechanisms of heavy metal immobilization

Journal

WASTE MANAGEMENT
Volume 143, Issue -, Pages 54-60

Publisher

PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.wasman.2022.02.021

Keywords

MSWI fly ash; Ceramsite; Civil sludge; Contaminated soil; Heavy metals; Immobilization mechanisms

Funding

  1. Qilu University of Technology (Shan-dong Academy of Sciences) integration of science, education and in-dustry innovation pilot project [2020KJC-ZD12, 2021GXRC067, 2021GXRC124]
  2. Major Scientific & Technological Innovation Project of Shandong Province [2020CXGC011404]

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In this study, ceramsite was prepared using MSWI fly ash, civil sludge, and contaminated soil as raw materials. The optimal preparation conditions were determined and the immobilization mechanisms of heavy metals were explored. The obtained ceramsite showed excellent performance parameters and the leaching of heavy metals was much lower than the standard. Therefore, the reuse of MSWI fly ash is an effective method for reducing solid wastes.
With an increase in municipal solid waste incineration (MSWI) fly ash and its dangerous characteristics, the manner of its disposal has caused widespread concerns. In this study, ceramsite was prepared by using MSWI fly ash, civil sludge, and contaminated soil as the main raw materials; then, a certain proportion of clay was added as an additive. The optimum MSWI fly ash content and sintering conditions were investigated, and the immobilization mechanisms of heavy metals were explored. Based on the obtained results, the optimum preparation conditions were a preheating temperature of 400 degrees C, a preheating time of 10 min, a sintering temperature of 1150 degrees C, and a sintering time of 20 min. Moreover, the optimal raw material ratio of MSWI fly ash, civil sludge, contaminated soil, and flint clay was 30%:40%:15%:15%. Under these optimum preparation conditions, the obtained ceramsite showed the following excellent performance parameters: a 1-h water absorption of 0.97%, bulk density of 998.7 kg/m(3), and cylindrical compressive strength of 37.84 MPa. Furthermore, the leaching of heavy metals was far less than the standard GB5085.3-2007. The immobilization of heavy metals in the ceramsite was mainly caused by the glass phase encapsulation and the formation of new crystal phase with the heavy metals. In addition, the generation of aluminosilicates played a positive role in the immobilization of heavy metals. Thus, the reuse of MSWI fly ash by preparing fly ash-based ceramsite is one of the effective methods for reducing solid wastes.

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