Determining controls on element concentrations in fly ash leachate

Reardon, Eric J.; Czank, C.A.; Warren, C.J.; Dayal, R.; Johnston, Holly M.

doi:10.1016/s0734-242x(05)80023-0

Cited by 14 publications

(6 citation statements)

References 22 publications

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“…6). This result is supported by the work of Reardon et al (1995), who assume arsenic as arsenate in leachate of fly ashes. Selective measurements of the redox potential show that (for arsenic) oxidising conditions prevail and arsenic is soluble as arsenate (see Fig.…”

Section: Anionssupporting

confidence: 64%

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Slag from hazardous waste incineration: Reduction of heavy metal leaching

Reich¹

2003

Waste Manag Res

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Hazardous waste incineration (HWI) in rotary kilns and the disposal of the residues on landfills play an important role in German waste treatment. In order to reduce costs by disposal on cheaper landfill sites still applying to landfill regulations the leaching behaviour of HWI-slag should be improved further. In a new process-integrated approach hazardous waste is mixed with limestone, which initiates chemical reactions with heavy metals in the rotary kiln yielding new compounds of different solubility. These reactions were observed after treatment at 1200 degrees C combined with fusion processes, at 930 degrees C they also occurred without fusion to the major part. For that purpose HWI-slag/limestone mixtures are thermally treated and then examined by elution tests. A minimum of overall heavy metal leaching was determined at CaO-contents between 15 and 20% after sintering at the average temperature at HWI.

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Section: Anionssupporting

confidence: 64%

“…7). This result is supported by the work of Reardon et al (1995), who assume arsenic as arsenate in leachate of fly ashes. The authors suggest that precipitation and sorption processes with iron mainly control arsenic solubility.…”

Section: Anionssupporting

confidence: 64%

Slag from hazardous waste incineration: Reduction of heavy metal leaching

Reich¹

2003

Waste Manag Res

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“…Chemical composition of coal ash and the factors influencing it are important, because the ash resulting from coal combustion is most often stored in landfills, where it is exposed to different influences that can solubilize some otherwise sparingly soluble compounds, which can then contaminate the soil and the surface water and groundwater in the vicinity of the plant. − This is particularly the case in situations when combustion byproducts are stored in the wet state, which prevents wind spreading but increases leaching of inorganic and organic pollutants. Coal ash dumping results in radioactive contamination, pollution of soil, , water, − and food resources. , Although some experiments of PAH formation during combustion were conducted (for example, establishments of the PAH content in filter ash obtained from lab- and bench-scale combustion systems), in situ studies of the influence of the temperature on the composition of PAH compounds in real systems in coal-fired power plants were not performed. This paper presents results obtained by the investigation of the PAH formation and behavior dependence upon the temperature, during coal combustion in the “Nikola Tesla B” coal-fired power plant.…”

Section: Introductionmentioning

confidence: 99%

Polycyclic Aromatic Hydrocarbons: Temperature Driven Formation and Behavior during Coal Combustion in a Coal-Fired Power Plant

2013

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In situ dependence of the formation and behavior of 16 United States Environmental Protection Agency (U.S. EPA) priority polycyclic aromatic hydrocarbons (PAHs) upon the temperature was examined during the experiment carried out on combustion temperatures between 930 and 998 °C in the "Nikola Tesla B" power plant, located 50 km from the Serbian capital, Belgrade. Samples of used lignite and lignite combustion byproducts were collected on a regular basis, and PAHs in collected samples were extracted using ultrasonic extraction with methylene chloride and analyzed by gas chromatography with mass selective detection (GC/MSD). Degradation and formation of PAH molecules were established. Different PAH synthesis mechanisms were noticed by correlation of obtained data, and the presence of phenyl addition/cyclization (PAC) and hydrogen abstraction/acetylene addition (HACA) mechanisms was confirmed. It was concluded that the increase of the combustion temperature has an influence on the increase of total PAH concentrations in combustion byproducts up to the threshold value, while at the same time, there are different distributions of different PAHs in ash and slag. The optimal combustion temperature, producing a minimal PAH concentration in combustion products, for Kolubara basin lignite in the "Nikola Tesla B" power plant is 930 °C.

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“…For example, on a molar basis, boron is the third highest concentration constituent in these leachates (only calcium and sulfate are higher). The approximate doubling in concentration with a halving of the water/ash ratio is evidence that there is no solubility control on boron concentrations in these mixes (10). Although dolomite addition had no effect on boron levels, lime addition resulted in concentration reductions to values below the detection limit, reflecting at least a 2 order of magnitude decrease in concentration.…”

Section: Resultsmentioning

confidence: 92%

Anion Sequestering by the Formation of Anionic Clays: Lime Treatment of Fly Ash Slurries

Reardon

Valle

1997

Environ. Sci. Technol.

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The addition of hydrated lime and dolomite to fly ash slurries results in the development of anionic clays. These minerals are comprised of stacked sequences of double-metal hydroxide layers. Unlike most clays, the hydroxide layers have a net positive charge. As a result, anionic-form elements in fly ash leachate waters are scavenged into the interlayer positions to neutralize the positive charge. In our experiments, leachate borate, sulfate, and arsenate concentrations were reduced by up to 2 orders of magnitude. High leachable boron is the chief limitation on the agricultural use of fly ash in soil remediation, and in this study lime treatment reduced leachable boron to levels below those toxic to plants. Under the oxygenated conditions of surface and near-surface waters, many elements of environmental concern occur as oxyanions, such as borate, arsenate, chromate, selenate, and molybdate. Anions are typically mobile under the neutral to alkaline pH conditions typical of most groundwaters, and little reliance can be given to the geosphere for their attenuation. The design of geochemical conditions to precipitate anionic clay minerals is a promising means to sequester and immobilize anionic-form elements from wastewaters. However, it is not known whether high pH conditions, which promote the formation of these anionic clays, will also be necessary to ensure their stability and thus the long-term immobilization of sequestered anions.

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Determining controls on element concentrations in fly ash leachate

Cited by 14 publications

References 22 publications

Slag from hazardous waste incineration: Reduction of heavy metal leaching

Slag from hazardous waste incineration: Reduction of heavy metal leaching

Polycyclic Aromatic Hydrocarbons: Temperature Driven Formation and Behavior during Coal Combustion in a Coal-Fired Power Plant

Anion Sequestering by the Formation of Anionic Clays: Lime Treatment of Fly Ash Slurries

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