Removal of uranium and gross radioactivity from coal bottom ash by CaCl2 roasting followed by HNO3 leaching

Lei, Xuefei; Qi, Guangxia; Sun, Yinglong; Wang, Yi

doi:10.1016/j.jhazmat.2014.05.052

Cited by 37 publications

(5 citation statements)

References 25 publications

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“…When the coal bottom ash was exposed to direct nitric acid (1 to 8 M) leaching, 22.6−25.5% of the total uranium was removed. 57 According to Warren and Dudas, 58 approximately 50% of the total U in the fly ash was leached in the sulfuric acid solution (pH 2.1). The leached concentrations of U in the European fly ashes range from <0.001 to 0.012 μg/g.…”

Section: Resultsmentioning

confidence: 99%

Leachability of Hazardous Trace Elements from Entrained-Flow Coal Gasification Residues in Ningdong, China

et al. 2017

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Based on the Solid Waste-Extraction Procedure for Leaching Toxicity (Chinese method HJ/T299-2007), the mobility of hazardous trace elements Be, Cr, Co, Ni, Cu, Zn, As, Se, Mo, Cd, Sb, Ba, Tl, Pb, U, and Hg in coal gasification residues and feed coal collected from a coal gasification plant in Ningdong, China, was evaluated to assess the potential hazard of these solid wastes when disposed. The major and trace element contents of the coal gasification residues and feed coals and the trace element concentrations of leachates were analyzed using X-ray fluorescence, atomic fluorescence spectrometry, and inductively couple plasma mass spectrometry. The volatile trace elements As, Se, Cd, Sb, Tl, and Pb tend to be enriched in fine residues with a smaller particle size and larger specific surface areas. Except for Hg, the other 15 hazardous trace elements are mobile to some extent in leaching solutions of pH 3.2 and 7.1. Because of the fixation by the glassy matrix and low liquid−solid ratio, the hazardous trace elements in the coal gasification residues have low extracted fractions. The leached Ba concentration is the highest, with a maximum leached concentration at 150 μg/L. Molybdenum is the most mobile of all 16 elements with 27.35% leached. Governed by geochemical properties and modes of occurrence for the elements in the residues, the concentration trends of As, Mo, Cd, Sb, Co, and Tl in the leachates are consistent, and their leached concentrations are in line with their concentration in the residues. The coal gasification residue samples generally do not present a leaching toxicity hazard. However, in some cases, the leached concentrations of Be, Mo, and Ba exceed the limitation of the secondary groundwater standards in China, and the leached Sb and Tl exceed the maximum contaminant level of primary drinking water in the U.S. However, the Sb concentration in the pH 3.2 leachate is 3 orders of magnitude higher than its general level in groundwater.

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Section: Resultsmentioning

confidence: 99%

Leachability of Hazardous Trace Elements from Entrained-Flow Coal Gasification Residues in Ningdong, China

et al. 2017

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“…It is lost with the gas and ultimately ends up in the fly ash during combustion in coal-fired power plants at temperatures above 1000 °C. (Coles et al 1978, Lei et al 2014, Yang et al 2016, Chen et al 2017. On the other hand, uranium which is originally associated with a silicate, such as coffinite, may migrate into the bottom ash as U 3 O 8 , UO 2 , and UO 2.33 (β) species (Coles et al 1978, Lei et al 2014, Yang et al 2016, Chen et al 2017.…”

Section: Uranium Isotope Ratios In Coal and Ashmentioning

confidence: 99%

“…(Coles et al 1978, Lei et al 2014, Yang et al 2016, Chen et al 2017. On the other hand, uranium which is originally associated with a silicate, such as coffinite, may migrate into the bottom ash as U 3 O 8 , UO 2 , and UO 2.33 (β) species (Coles et al 1978, Lei et al 2014, Yang et al 2016, Chen et al 2017. The distribution of different U species between fly ash and bottom ash may give rise to U isotope variation.…”

Section: Uranium Isotope Ratios In Coal and Ashmentioning

confidence: 99%

δ²³⁸U of Coal Reference Materials Determined by MC‐ICP‐MS

Sheng,

Li,

Owens

et al. 2023

Geostandard Geoanalytic Res

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Uranium (U) associated with coal can be an important source of U and result in environmental pollution during coal combustion. In this study, we developed a method for measurement of U isotope ratios in coals using multiple‐collector inductively coupled plasma‐mass spectrometry. The 233U‐236U double‐spike was utilised to calibrate the instrumental isotopic fractionation. High‐pressure bomb and dry ashing were adopted to digest the coal samples. The δ238UCRM‐145 values obtained from the two different digestion procedures were in good agreement. The δ238UCRM‐145 of seven coal and one fly ash reference materials are reported. Furthermore, the results of fly ash, bottom ash and feed coal samples reveal that the combustion processes lead to relatively small U isotopic fractionation between the samples within the same coal‐fired power plant, indicating that U isotope data can be used as a tracer for heavy metal pollution resulting from coal combustion. The U isotope measurement method of coal established in this study provides technical support to understand the behaviour of U during coal formation and combustion.

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“…The utilization of a huge amount of CCRs has many benefits in both economic and environmental aspects. Over the years, CCRs have been used in the manufacturing of cement, bricks, and concrete; in the extraction of critical metals (e.g., U, Ge, Ga, Al, and rare-earth elements); and in the construction of roadbed and dams. − About 5% of the total ash produced in coal-fired power plants is currently used as the substituent for building materials in the construction of residence . When CCRs with high NORMs are used in building materials, they may affect the human health by both external and internal irradiation .…”

Section: Introductionmentioning

confidence: 99%

Toward the Threshold of Radiation Hazards of U in Chinese Coal through the CART Algorithm

Yang

Peng

et al. 2022

Environ. Sci. Technol.

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The high volume of coal used for combustion usually leads to a large amount of coal combustion residues (CCRs), which contain the naturally occurring radioactive materials (NORMs) decayed from U and Th in coals. The high radioactivity of NORMs can cause potential harm to humans if the CCRs are used as building materials. The activities of CCRs not only depend on the concentrations of radionuclides but also largely depend on the variations of ash yields of coal. On the other hand, ash yields significantly vary in coal from less than 1−50%. This indicates that similar concentrations of radionuclides in coal with different ash yields generally do not result in similar activities in CCRs. Therefore, it is significant to build a threshold of U in coals with different ash yield levels. In this research, based on the data of 945 coal samples from China and the selected optimal model using the classification and regression tree algorithm, the threshold of U for the radiation hazard is determined to be 7.98 mg/kg for coals with ash yields higher than 20%, while the threshold of U for the radiation hazard is 5.28 mg/kg for coals with ash yields lower than 20%.

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Removal of uranium and gross radioactivity from coal bottom ash by CaCl2 roasting followed by HNO3 leaching

Cited by 37 publications

References 25 publications

Leachability of Hazardous Trace Elements from Entrained-Flow Coal Gasification Residues in Ningdong, China

Leachability of Hazardous Trace Elements from Entrained-Flow Coal Gasification Residues in Ningdong, China

δ²³⁸U of Coal Reference Materials Determined by MC‐ICP‐MS

Toward the Threshold of Radiation Hazards of U in Chinese Coal through the CART Algorithm

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Removal of uranium and gross radioactivity from coal bottom ash by CaCl2 roasting followed by HNO3 leaching

Cited by 37 publications

References 25 publications

Leachability of Hazardous Trace Elements from Entrained-Flow Coal Gasification Residues in Ningdong, China

Leachability of Hazardous Trace Elements from Entrained-Flow Coal Gasification Residues in Ningdong, China

δ238U of Coal Reference Materials Determined by MC‐ICP‐MS

Toward the Threshold of Radiation Hazards of U in Chinese Coal through the CART Algorithm

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δ²³⁸U of Coal Reference Materials Determined by MC‐ICP‐MS