Bayuseno, Athanasius P.; Schmahl, Wolfgang W.
Characterization of MSWI fly ash through mineralogy and water extraction.
In: Resources Conservation And Recycling, Vol. 55, No. 5: pp. 524-534
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This paper investigates the mineralogical characteristics of fresh, agedand hot water extracted MSWI fly ash for providing the baselineinformation of minerals stability which controls the released heavymetals into the environment. Quantitative determination of bulk phaseabundance in the fresh fly ash by the XRD Rietveld refinement methodprovided composition levels for amorphous and crystalline phases such aspotassium tetrachlorozincate (K(2)ZnCl(4)), gehlenite, halite, quartz,anhydrite, and feldspar. The minerals association in the fly ash isclearly unstable and subject to mineralogical reactions. The phases ofK(2)ZnCl(4), halite and anhydrite in the fresh fly ash were involved inhydration and dissolution/precipitation processes to form new mineralssuch as the Zn-bearing mineral gordaite, syngenite, gypsum andhydrocalumite. The solubility-controlling phases and extractability ofheavy metals were examined in a Soxhlet hot water-extractor. Here thesoluble salts were simply removed from fly ash while Ca-, Al-, Si- andSO(4)(2-)-bearing hydrate minerals were precipitated from the extractionsolution. Furthermore, a low release of heavy metals Zn, Pb and Cd inhot water was noticed, indicating a strong retention of the trace metalsin the mineral phases remaining in the insoluble fly ash residues.