The surface chemistry of leaching coal fly ash

Iyer, Ramasubramania

doi:10.1016/s0304-3894(02)00049-3

Cited by 114 publications

(57 citation statements)

References 23 publications

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“…This results not only in a strong gradient of element concentrations within fly ash particles (Kukier et al, 2003), but also in a gradient of leachability. The surface layer of fly ash particles, only microns in thickness, contains a significant amount of readily leachable elements (Iyer, 2002) that, with the exception of S, stand out for being inherently more toxic at low levels than major elements.…”

Section: General Aspectsmentioning

confidence: 99%

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

Izquierdo

Querol

2012

International Journal of Coal Geology

632

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%

“…A given element may dissolve from fly ash and then precipitate as stable and less soluble secondary phases (Iyer, 2002), with the result that the element is removed from the leachates.…”

Section: General Aspectsmentioning

confidence: 99%

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

Izquierdo

Querol

2012

International Journal of Coal Geology

632

379

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“…The leaching of toxic elements can be minimized by transporting the ash slurry at high solids concentration as the production of leachate can be controlled by the evaporation of bleeding water (Iyer 2002). At higher solids concentration, the viscosity of the slurry increases and flow behaviour changes drastically affecting the rheological parameters.…”

Section: Introductionmentioning

confidence: 99%

Assessment of heavy metals and rheological characteristics of coal ash samples in presence of some selective additives

Pani

Rath

Maharana

et al. 2015

Int. J. Environ. Sci. Technol.

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The huge quantity of coal ash produced in Indian thermal power plants is disposed of in ash landfills or ash ponds. The deposition of ash in ash ponds through conventional lean slurry form is viewed as a major potential release of many environmentally sensitive heavy metals due to possible contamination with ground water. An attempt has been made in this paper to assess the leachability of the heavy metals such as Cu, Pb, Ni, Co, Zn, Cd, Hg and As from two Indian power plant ash samples in the presence of some selective low-cost additives. The additives used for the study were sodium silicate (Na 2-SiO 3 Á5H 2 O), Reetha fruit (botanical name: Sapindus Mukorossi) extract, banana leaf extract, Aloe vera juice and active carbon. By adopting short duration (7 days) batch leaching test and toxicity characteristics leaching procedure (TCLP), the behaviour of various heavy metal ions released in water influenced by small dosage of these selective additives has been analysed. By introducing the same additives, the rheological behaviour of the two fly ash samples at high solids concentration (C W = 55-67.5 % by weight) was carried out using a HAAKE rotational rheometer (model: RheoStress 1, Thermo Fisher Scientific). The influence of small dosage of these additives on rheological parameters of the ash-water slurry has been discussed.

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“…Extracting aluminum from CFA is a practical option since CFA contains about 10-55% (by mass) of Al 2 O 3 [14][15][16][17][18]. Especially, high-aluminum CFA (40-50%) has been found in southern Inner Mongolia, northern Shanxi and the Shaanxi province of China [4,[19][20].…”

mentioning

confidence: 99%

S181 Extraction of Aluminum from Coal Fly Ash by Alkali Activation with Microwave Heating

Liu¹,

Peng²,

Zhang³

et al. 2016

JRST

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ABSTRACT:Recovering aluminum from coal fly ash (CFA) is a practical option for its value-added utilization. The alkali activation of CFA with Na 2 CO 3 was carried out using two heating methods: the conventional heating (CH) and microwave heating (MWH). Compared to CH, MWH enhanced the atomic diffusion and mass transportation in the CFA-Na 2 CO 3 mixture, accelerated the decomposition of mullite and the formation of the soluble Al-containing materials, thus greatly reducing the sintering temperature and dramatically shortening the activation reaction time. Under the moderate activation condition in MWH (700°C and 20 min), the aluminum extraction could reach 95.52% or more.

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The surface chemistry of leaching coal fly ash

Cited by 114 publications

References 23 publications

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

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

Assessment of heavy metals and rheological characteristics of coal ash samples in presence of some selective additives

S181 Extraction of Aluminum from Coal Fly Ash by Alkali Activation with Microwave Heating

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