Leaching of CCBs: observations from over 25 years of research

Hassett, D.J.; Pflughoeft-Hassett, Debra F.; Heebink, Loreal V.

doi:10.1016/j.fuel.2004.10.016

Cited by 67 publications

(49 citation statements)

References 5 publications

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“…As will be discussed later, minerals such as ettringite [Ca 6 Al 2 (SO 4 ) 3 (OH) 12 ·26H 2 O], which is the primary phase always reported during the reaction of alkaline ash with water (Hassett et al, 2005), may capture a number of trace elements (Jones, 1995). Ettringite requires Ca, Al, SO 4 2-, excess water and pH>11 to form (Hassett et al, 2005).…”

Section: General Aspectsmentioning

confidence: 99%

“…Ettringite requires Ca, Al, SO 4 2-, excess water and pH>11 to form (Hassett et al, 2005). The precipitation of various Ca-bearing species is also common, given the ubiquity of Ca.…”

Section: General Aspectsmentioning

confidence: 99%

“…Among the variety of available leaching procedures, four types are commonly used in the literature to assess the leaching behaviour of coal ash: (i) batch leaching tests using deionised water or similar as leachant (no pH buffering) are often conducted to obtain information on the leachability of elements when the pH is governed by the ash itself; (ii) column/flow-through tests provide valuable data on the release pattern of elements under uncontrolled pH conditions; (iii) Toxicity Characteristic Leaching Procedure (TCLP), designed by US EPA and mandated for use in determining the hazardousness of materials to be disposed of (Hassett et al, 2005). The US EPA does not specifically recommend this test for coal combustion products, as it does not provide an accurate assessment of this material (Federal Register, 2010;Hassett et al, 2005).…”

Section: Leaching Protocols and Regulationsmentioning

confidence: 99%

“…The US EPA does not specifically recommend this test for coal combustion products, as it does not provide an accurate assessment of this material (Federal Register, 2010;Hassett et al, 2005). However, the TCLP appears to be the worst case test most often used throughout the literature.…”

Section: Leaching Protocols and Regulationsmentioning

confidence: 99%

“…The precipitation of ettringite at pH>11.5 would also account for the dramatic reduction in As in solution (Figure 1), along with Al, Si, S and and other oxyanionic species (Jones, 1995;Cornelis et al, 2008). According to Hassett et al (2005), As in its oxyanionic form is too large to fit into the ettringite structure, but it can sorb on to already-formed ettringite. At such pH values, portlandite may contribute to the sequestration of As by strongly sorbing arsenate (van der Hoek et al, 1994).…”

Section: Arsenicmentioning

confidence: 99%

See 4 more Smart Citations

Leaching behaviour of elements from coal combustion fly ash: An overview

Izquierdo

Querol

2012

International Journal of Coal Geology

625

379

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Coal-based power generation produces over 750 Mt of coal ash per year globally, but under 50% of world production is utilised. Large amounts of fly ash are either stored temporarily in stockpiles, disposed of in ash landfills or lagooned. Coal ash is viewed as a major potential source of release of many environmentally sensitive elements to the environment. This paper encompasses over 90 publications on coal fly ash and demonstrates that a large number of elements are tightly bound to fly ash and may not be easily released to the environment, regardless of the nature of the ash. This review provides an extensive look at the extent to which major and trace elements are leached from coal fly ash. It also gives an insight into the factors underlying the leachability of elements and addresses the causes of the mobility. The mode of occurrence of a given element in the parent coal was found to play an important role in the leaching behaviour of fly ash. The amount of calcium in fly ash exerts a dominant influence on the pH of the ash-water system. The mobility of most elements contained in ash is markedly pH sensitive. The alkalinity of fly ash attenuates the release of a large number of elements of concern such as Cd, Co, Cu, Hg, Ni, Pb, Sn or Zn among others, but at the same time, it enhances the release of oxyanionic species such as As, B, Cr, Mo, Sb, Se, V and W. The precipitation of secondary phases such as ettringite may capture and bind several pollutants such ash As, B, Cr, Sb, Se and V.

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Section: General Aspectsmentioning

confidence: 99%

“…Ettringite requires Ca, Al, SO 4 2-, excess water and pH>11 to form (Hassett et al, 2005). The precipitation of various Ca-bearing species is also common, given the ubiquity of Ca.…”

Section: General Aspectsmentioning

confidence: 99%