Municipal solid waste incineration (MSWI) fly ash composition analysis:a case study of combined chelatant-based washing treatment efficiency

The challenge of sustainable use of MSWI residues such as fly ash is particularly acute. One of the possible uses of these residues in making secondary building materials. However, MSWI fly ash is highly contaminated with toxic elements such as Pb, Zn, Cd, Cu, etc. Its treatment to reduce the environmental impact is required before reuse or disposal. Here, the efficiency of a new three-step combined treatment with two complexing agents (ethylenediaminetetraacetate and gluconate) to increase the toxic-element elution from fly ash in contrast to conventional water-only treatments is shown. The compositions of raw and differently treated (reagent-combined and water-only treatments) MSWI fly ash were compared by macro- and microelemental, mineralogical, and microstructure analysis, in addition to the standard leaching test. The relevancy for such comprehensive analysis of MSWI fly ash prior and after treatments to minimize the environmental risks is shown. For Cd, Cu, and Zn, the combined treatment is proved to be 10–1000-fold more efficient than the water-only one. It was shown that the same WFA, which seems non-hazardous according to the leaching test after being washed with water, proves to be extremely hazardous when more properties are taken into account. Thus, it is relevant not only to study the leaching of WFA components and the factors affecting it, but also to pay detailed attention to amounts of elements remaining in the material after treatments.