Abstract
Incineration is one of the most effective techniques for the treatment of both municipal and hazardous wastes. Via this technique, the majority of toxic substances are expected to be stabilized in the durable matrix of the end-ofprocess bottom ash products. These products consist of a variety of glassy/crystalline components including primary Fe-rich phases that may undergo alterations when exposed to natural environment. In the present research, the impact of natural weathering on the behavior of primary Fe-rich phases, their alteration, and the formation of the relevant secondary products in the weathered bottom ash samples of a (mono) landfill site was systematically investigated. Samples of various ages (1-20 yrs) were collected from four locations of the landfill in 2009. Optical microscopy, SEM-EDX, XRD and XRF examinations were applied in order to document the footprints of weathering processes. Using these techniques, we understood that several secondary (newly-formed) products (amorphous or crystalline) have been developed, including goethite (α-FeOOH), lepidocrocite (γ-FeOOH), hematite (Fe2O3), magnetite (Fe3O4), iron oxide (FeO), and Fe-rich Ca-Si and Ca-Al-Si gel phases. They occurred under variable environmental conditions as the weathering products of the primary iron-rich phases. The strong affinity of these secondary phases with heavy metals of environmental significance such as Zn, Cu, Pb, and Ni was also identified. This suggests that the development of secondary Fe-rich products can partially contribute to the reduction of heavy metals release to the surrounding environments. However such phenomena may have inhibitory effect on the utilization of bottom ash as recycled aggregates.
Highlights
Incineration technology has been adopted as an effective strategy for the treatment of municipal and hazardous wastes in many communities at different scales with highest share among the developed countries
With the emerging high-performance software technologies SEMEDX has become a standard method for the characterization and Results and Discussion Primary iron-rich constituents of Municipal solid waste incineration (MSWI) bottom ash MSWI bottom ash may contain a considerable amount of metalrich phases that are essentially made up of iron, aluminum and copper
We designed a systematic approach in order to evaluate the inorganic chemistry and mineralogical properties of MSWI bottom ash products when exposed to natural weathering in a full-scale MSWI mono site
Summary
Incineration technology has been adopted as an effective strategy for the treatment of municipal and hazardous wastes in many communities at different scales with highest share among the developed countries. This treatment technique results in the generation of various residues including bottom ash and fly ash as the major solid outputs totally ranging from 4-10% by volume and 15-20% by weight of the original quantity of waste [1]. They predominantly consist of glassy phase and significant concentration of hazardous components comparing with the source materials. Many researchers have been investigating the natural or accelerated aging of bottom ash, a process which could be applied to fly ash disposal [7,8,9,10]
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