Leaching Behavior of Fossil Fuel Wastes: Mineralogy and Geochemistry of Calcium

Rai, Dhanpat; Eary, L. E.; Mattigod, Shas V.; Ainsworth, Calvin C.; Zachara, John M.

doi:10.1557/proc-86-3

Cited by 5 publications

(3 citation statements)

References 36 publications

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“…High concentrations of Cr(VI) may induce precipitation of a moderately soluble mineral (hashemite: BaCrO 4 ) and/or the formation of the lower solubility solid solutions of BaCrO 4 BaSO 4 , . These phases may control Cr(VI) solubility and mobility especially in naturally aged contaminated sediments.…”

Section: Introductionmentioning

confidence: 99%

Pathways of Aqueous Cr(VI) Attenuation in a Slightly Alkaline Oxic Subsurface

Qafoku

Dresel

McKinley

et al. 2009

Environ. Sci. Technol.

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Column experiments combined with geochemical modeling, microscopic inspections, spectroscopic interrogations, and wet chemical extractions were used to study sediment-dependent Cr(VI) desorption, physical location, mineral association, and attenuation mechanism(s) in four freshly or naturally aged contaminated sediments exposed to concentrated Cr(VI) waste fluids. Results showed that majority of Cr(VI) mass was easily removed from the sediments (equilibrium site K(d) varied from 0 to 0.33 mL g(-1) and equilibrium site fraction was greater than 95%). Long tailings of time-dependent Cr(VI) concentrations above maximum contaminant level of 1.9 micromol L(-1) were also observed (kinetically controlled fraction K(d) and desorption reaction half-lives varied from 0 to 45 mL g(-1), and from 76.1 to 126 h, respectively). Microscopic and spectroscopic measurements confirmed that Cr was concentrated within fine-grained coatings in small areas mainly rich in phyllosilicates that contained both Cr(III) and Cr(VI). However, Cr(VI) reduction was neither significant nor complete. Under slightly alkaline and oxic conditions, contaminant Cr in the sediments occurred: (i) In the highly mobile pool (over 95% of total Cr); (ii) In the slow and time-dependent releasing pool, which served as long-term source of contamination; (iii) As reduced Cr(III) which most likely formed during Cr(VI) reaction with aqueous, sorbed, or structural Fe(II).

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Section: Introductionmentioning

confidence: 99%

Pathways of Aqueous Cr(VI) Attenuation in a Slightly Alkaline Oxic Subsurface

Qafoku

Dresel

McKinley

et al. 2009

Environ. Sci. Technol.

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“…3, 44.3, 4.7, 25.7, and 15.6. Brought to you by | UCL -University College London Authenticated Download Date | 1/1/16 5:49 PM Notes: n.d. = not determined either a waste product or a secondary raw material. In the first case, studies addressed primarily the potential environmental problems related to disposal of large quantities of fly ash in landfills, surface impoundments, and mines, and the associated possible release of toxic components to the groundwater (Rai et al 1987;Mattigod et al 1990;Hansen et al 2002). In the second case, fly ash was investigated as a possible resource for the production of so-called ecomaterials (Halada and Yamamoto 2001), e.g., as an additive to concrete formulations or as a raw material for ceramics, glass-ceramics, and glasses (DeGuire and Risbud 1984;McCarthy et al 1989;Cumpston et al 1992;Cioffi et al 1993;Glasser 1993;Barbieri et al 1999).…”

Section: Discussionmentioning

confidence: 99%

Micro- and nanochemistry of fly ash from a coal-fired power plant

Gieré

Carleton

Lumpkin

2003

American Mineralogist

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Fly ash from a coal-fired power plant was investigated to obtain detailed information on its physical and chemical properties, and to gain an understanding of potential environmental and health impacts associated with its disposal in landfills. The studied material was produced through combustion of Illinois Basin coal and trapped within the power plant by an electrostatic precipitator. It is a finegrained, low-Ca fly ash containing primarily SiO 2 , Al 2 O 3 , and Fe 2 O 3 , and is enriched in many toxic elements (e.g., Be, Zn, As, Cd, Tl, Pb, and U) by a factor of up to 30 relative to coal. The ash consists of mainly hematite, magnetite, mullite, quartz, and amorphous material. These constituents occur mostly as spherical particles with diameters of less than 13 mm. We examined the physical, chemical, and structural characteristics of individual fly ash particles by scanning and transmission electron microscopy and electron probe microanalysis. The results demonstrate that, with the exception of complex plerospheres, individual particles are chemically fairly homogeneous, but a pronounced compositional variation exists among particles with similar physical and structural attributes. Electron microprobe data document that several trace elements, including U, are partitioned into the Ferich particles. Transmission electron microscopy revealed that various types of small (<1 mm) crystalline Ca-rich phases, including lime, are attached to the glass spheres, particularly the nonmagnetic glass. These crystals may contain substantial amounts of S. Even though only a few of these crystals were analyzed quantitatively, our data indicate that the Ca-rich and S-rich phases may be important hosts for trace elements such as V and Zn. The observed element partitioning and the existence of surface-attached crystals enriched in certain trace elements suggest that fly ash from coal-fired power plants might have a more deleterious environmental impact than is inferred from bulk analytical data.

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“…These results were related to prop- erties of Cr 3+ ions in solution such as hydrolyzation (reaction (15)), hydroxylation (reactions (16), (17)) and oxygenation (reaction (18)), in which the hydroxyl bridge transformed to oxygen bridge. 22,23) Higher pH value could facilitate the occurrence of reaction (15) and thus reaction (16) and (17) to produce Cr(OH)3, leading to increase in the recovery rate of chromium. However, Cr(OH)3 would gradually dissolve to produce CrO2 -in alkaline solution (pH > 8.05) as described by reaction (18), leading to lower chromium recovery rate.…”

Section: +mentioning

confidence: 99%

Effective Chromium Extraction from Chromium-containing Vanadium Slag by Sodium Roasting and Water Leaching

Fang

Xie

2012

ISIJ Int.

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Chromium (Cr) was concentrated as chromium spinel in the vanadium slag produced by pre-oxidizing vanadium-containing hot metal in Pan-steel in China. Due to the chromium-rich Hongge ores used, chromium concentration in this slag was much higher than that in common vanadium slags. To propose a process for effective Cr extraction from the slag, mechanisms of Cr oxidation in Pan-steel vanadium slag under sodium roasting conditions were studied experimentally and with thermodynamic simulations. Chromium slags without vanadium were synthesized in the laboratory to mimick mineralogical characteristics of Pan-steel vanadium slag and characterized by XRD, SEM/EDS and TG-DSC techniques. Conditions for Cr extraction from the chromium slag after sodium roasting by leaching with water were studied and optimized. Results showed that Cr spinel was encapsulated in the silicate phase. During sodium roasting, Cr spinel was oxidized and decomposed after oxidation and decomposition of the olivine phase. Sodium carbonate began to react with chromium oxide, which was produced by decomposition of Cr spinel, at 537°C and large amount of sodium chromate appeared after 800°C. However, multi-component liquid phase (mixture of Na2Cr2O4, Na2CrO4 and Na2CO3) was produced after 1 000°C, which suppressed the conversion of Cr(III) to Cr(VI) by inhibiting oxygen supply. A conversion about 90% was obtained when the chromium slag was roasted at 1 000°C for 2 h with Na2CO3 addition in stoichiometric ratio to total amount of Cr2O3 and SiO2. 96% of Cr in the leaching liquid was recovered as chromium sesquioxide in fine powder form and high purity by reducing and precipitating.

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Leaching Behavior of Fossil Fuel Wastes: Mineralogy and Geochemistry of Calcium

Cited by 5 publications

References 36 publications

Pathways of Aqueous Cr(VI) Attenuation in a Slightly Alkaline Oxic Subsurface

Pathways of Aqueous Cr(VI) Attenuation in a Slightly Alkaline Oxic Subsurface

Micro- and nanochemistry of fly ash from a coal-fired power plant

Effective Chromium Extraction from Chromium-containing Vanadium Slag by Sodium Roasting and Water Leaching

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