The leaching of major and trace elements from MSWI bottom ash as a function of pH and time

Quality and generation rate of solid residues in the boiler of a waste-to-energy plant

“…The release of Cr, Pb, Se and Zn was influenced by pH conditions following typical release curves, as found for other incineration residues (e.g. [7,35,36,37,38,39]). Similar results were obtained during the first sampling campaign (results reported in Fig.…”

Long-term brine impacted fly ash, Part II: Mobility of major species in the ash residues

“…However, a rapid and continuous increase in the concentrations of Ca observed as the pH decreased could be attributed to the dissolution of any secondary Ca-rich mineral phases in the ash residues. The dissolution of gypsum has been observed to govern the solubility of Ca between pH 4 and 8 (Dijkstra et al 2006). Vitkova et al (2013) observed non-stoichiometric release of Ca at high pH ranges after which a congruent dissolution of calcium silicate followed at lower pH.…”

“…The slow initial release of Al in the ANC systems could be governed by the precipitation of amorphous phases at high pH while the dissolution of the amorphous and crystalline mineral phases at lower pH could responsible for the increase thereafter. Studies (Kim et al 2003;Ward et al 2009;Izquierdo and Querol 2012;Dijkstra et al 2006;Djedidi et al 2009) have shown that at pH below the natural pH of fly ash (ranging between 6 and 8), the release of Al is controlled by the precipitation of Al (hydr)oxides such as Al(OH) 3 from solution. The lower concentration of Al at pH between 6 and 10 could be attributed to the precipitation of amorphous Al-bearing phases in the systems.…”

“…The leaching of species from fly ash also depends on the pH of the leachant (Gitari et al 2009; Van der Sloot and Dijkstra 2004). Any aqueous flow that percolates or comes in contact with the fly ash dissolves or precipitates the species (Dijkstra et al 2006) depending on its pH. The release of species from fly ash systems is primarily controlled by the solubility of various mineral phases at different pH levels (van Herreweghe et al 2002).…”

“…The safe disposal of fly ash has been a major issue because of the possible leaching of species from the waste material to the receiving environment including surface and groundwater. The leaching of species from fly ash or municipal solid waste incineration (MSWI) ash depends on several factors which include physical and chemical composition of the fly ash (Dijkstra et al 2006). The leaching of species from fly ash also depends on the pH of the leachant (Gitari et al 2009; Van der Sloot and Dijkstra 2004).…”