Extraction of soluble major and trace elements from fly ash in open and closed leaching systems

Querol, Xavier; Umaña, J.C; Alastuey, Andrés; Ayora, Carlos; López-Soler, A.; Plana, F.

doi:10.1016/s0016-2361(00)00155-1

Cited by 123 publications

(72 citation statements)

References 20 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…In a column leaching test conducted by Dudas (1981), a steady rise in soluble Mg levels of leachates was observed as Ca was progressively washed out, which was attributed to the slow dissolution and hydrolytic reactions of carbonate compounds. Other authors did not observe this Ca-linked increase in Mg leaching over time, but the leached levels of Mg remained close to the detection limit (Querol et al, 2001). …”

Section: Magnesiummentioning

confidence: 78%

“…The drop in the Al leachability at pH11.5 is consistent with that of Si and other oxyanions, and is directly linked to the precipitation of ettringite (Cornelis et al, 2008;Jones, 1995 (Roy and Griffin, 1984), mullite is considered a non reactive mineral in aqueous solutions (Tishmack, 1996). The dissolution of the amorphous glassy matter appears to be the most likely source of Al in leachates (Dubikova et al, 2006;Querol et al, 2001). The structure and composition of the glass may enhance the reactivity and leachability of Al.…”

Section: Major Elements Aluminiummentioning

confidence: 83%

“…If conducting a column test or a multiple batch test, one can expect high conductive salt-rich leachates at early stages (Dudas, 1981;Querol et al, 2001), as these KCa-Na chlorides and sulphates are soluble across the pH range. As the leaching progresses, the leachate composition will reflect this rapid depletion of salts.…”

Section: General Aspectsmentioning

confidence: 99%

“…The pH of the ash-water system seems to be controlled by the ratio between ubiquitous Ca and S concentrations in fly ash (Querol et al, 2001), although other minor alkalis or alkaline earth cations such as Mg may also contribute to the balance (Ward et al, 2009). The occurrence and levels of Ca-bearing phases in ash are intimately related to the depositional environment of coal.…”

Section: General Aspectsmentioning

confidence: 99%

“… Mildly alkaline ashes: anhydrite dissolution dominates leaching, with moderately low Ca levels and balanced Ca/S ratios that give rise to mildly alkaline conditions (pH 8-9) (Querol et al, 2001)  Acidic fly ash: depleted in CaO and MgO in relation to the sulphate content (Ward et al, 2009) and therefore retains its original acid characteristics, as the acidic components concentrated on the surface of fly ash particles are initially brought into solution as sulphuric acid (Swaine, 1990).…”

Section: General Aspectsmentioning

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

619

379

View full text Add to dashboard Cite

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.

show abstract

Section: Magnesiummentioning

confidence: 78%

Section: Major Elements Aluminiummentioning

confidence: 83%

Section: General Aspectsmentioning

confidence: 99%

Section: General Aspectsmentioning

confidence: 99%

Section: General Aspectsmentioning

confidence: 99%

See 3 more Smart Citations

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

Izquierdo

Querol

2012

International Journal of Coal Geology

619

379

View full text Add to dashboard Cite

show abstract

Fossil‐Fuel Power Plants

Vogel¹,

Kalb²

2010

Large‐Scale Solar Thermal Power

View full text Add to dashboard Cite

Removal of heavy metals from fly ash and the impact on its quality

Nugteren

Janssen-Jurkovícová

Scarlett

2002

J of Chemical Tech & Biotech

View full text Add to dashboard Cite

Most coal¯y ashes currently produced in The Netherlands contain leachable trace elements in amounts higher than allowed by Dutch law for its free application as a granular building material. To improve their technical and environmental quality, these ashes were subjected to forced leaching using water, citrate, oxalate, EDTA and carbonate solutions. With water alone, the free lime and substantial amounts of Mo (30%), Se (20±40%) and SO 4 2À (40±50%) are removed. Using the extraction agents, these percentages increase to 60±90% and in addition 15±20% Cr, V and Sb are removed. Most of the extraction agents used form stable complexes or compounds with Ca 2 , thus prewashing with water followed by treatment with extraction agents resulted in higher removal and/or lower reagent consumption. The environmental quality of the washed¯y ash was evaluated using the Dutch standard leaching test (NEN7343). Leachability of oxyanions decreased by a factor of 2±4 after washing with water and by between 2 and 18 after washing with extraction agents. However, combined washing did not further decrease leaching but in some cases caused increased leaching. Selection of the washing procedure thus depends on the subsequent application of the ash, that is whether low concentrations or low mobility of trace elements are required. Removing extractants and metals remaining in the moisture after ®ltration will further decrease leaching. For a feasible process reduction of reagent consumption and simple methods for process water recycling are needed.

show abstract

Extraction of soluble major and trace elements from fly ash in open and closed leaching systems

Cited by 123 publications

References 20 publications

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

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

Fossil‐Fuel Power Plants

Removal of heavy metals from fly ash and the impact on its quality

Contact Info

Product

Resources

About