Calcined Dolomite: Alternative to Lime for Minimizing Undesirable Element Leachability from Fly Ash

Guo, Qinghai; Reardon, Eric J.

doi:10.1021/ie300387d

Cited by 8 publications

(3 citation statements)

References 18 publications

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“…In view of its unique structure and chemical characteristics, hydrocalumite has been applied in not only catalysis industry but also environmental remediation. In recent years, it was widely used for removing undesirable anions from wastewaters or contaminated natural waters, including B(OH) 4 − , CrO [4,5] and even some organic anions (e.g., dodecyl benzene sulfate (DBS − ) and methyl orange (MO)) [6,7]. The involved anion uptake mechanisms comprise surface adsorption, anion exchange, and dissolutionreprecipitation.…”

Section: Introductionmentioning

confidence: 99%

Thermal Decomposition of Hydrocalumite over a Temperature Range of 400–1500°C and Its Structure Reconstruction in Water

Jiao

Guo

2014

Journal of Chemistry

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The thermal decomposition process and structure memory effect of hydrocalumite were investigated systematically for the first time over a wide temperature range of 400–1500°C. The calcined hydrocalumite samples and their rehydrated products were characterized by XRD, FT-IR, and SEM-EDX. The results show that the calcination products at temperatures ranging from 500 to 900°C are basically mayenite and lime, while one of the final products obtained by calcination at and above 1000°C is probably tricalcium aluminate (Ca3Al2O6). For the hydrocalumite samples calcined at temperatures below 1000°C, their lamellar structure can be completely recovered in deionized water at room temperature. However, the further increase of calcination temperature could impair the regeneration ability of hydrocalumite via contact with water. Upon calcination of hydrocalumite at 1000–1500°C followed by reaction with water, a stable compound tricalcium aluminate hexahydrate (Ca3Al2O6·6H2O) was produced, which is the reason why less hydrocalumite could be regenerated.

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Section: Introductionmentioning

confidence: 99%

Thermal Decomposition of Hydrocalumite over a Temperature Range of 400–1500°C and Its Structure Reconstruction in Water

Jiao

Guo

2014

Journal of Chemistry

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“…Therefore, Ca-enriched particles correspond to hydrocalumite and Mg-enriched particles to hydrotalcite. In fact, hydrotalcite is more likely to be present as a non-well-formed phase compared with hydrocalumite [44]. The EDX analysis also shows the presence of silica that has been attributed to the presence of microcrystalline quartz.…”

Section: Resultsmentioning

confidence: 97%

Hydrotalcite and Hydrocalumite in Mortar Binders from the Medieval Castle of Portilla (Álava, North Spain): Accurate Mineralogical Control to Achieve More Reliable Chronological Ages

et al. 2018

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Abstract:Mortars from different stratigraphic units at Portilla Castle (Alava, North Spain) have been analyzed for mineralogical characterization before radiocarbon dating. The mortar binder at Portilla Castle is composed not only of neoformation calcite but also of double-layered hydroxide (LDH) minerals such as hydrotalcite and hydrocalumite. The mineralogy of several fractions of the binder has been analyzed to determine the granulometric distribution of minerals in the binder. The continuous monitoring of mineralogy during the extraction of different grain size fractions has been performed by using a scanning electron microscopy (SEM), X-ray diffraction (XRD), and thermogravimetric analyses (TGA). Hydrotalcite and hydrocalumite-bearing mortar binders give older ages than expected since they introduce dead carbon into the system.

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“…Throughout the past couple of decades, people have done a great deal of experimental research on the chemical kinetics of the dolomite decomposition stage − and the magnesium reduction stage, ,− and some solid–solid reaction models were applied to describe these two processes. The phase boundary reaction model of zero order was found by Halikia et al to best represent the dolomite decomposition stage, and the shrinking nonreacted core model was used to describe the intrinsic kinetics of the magnesium reduction stage.…”

Section: Introductionmentioning

confidence: 99%

Experimental and Numerical Studies on a One-Step Method for the Production of Mg in the Silicothermic Reduction Process

Zhang

Wang

Zhang

et al. 2015

Ind. Eng. Chem. Res.

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In this paper, a new efficient one-step technical method was first developed for the production of magnesium in the industry. The one-step method could combine the two processes of dolomite decomposition and magnesium reduction in the magnesium reduction retort. Thus, the high-temperature carbon dioxide produced by the dolomite decomposition process could be collected in a timely manner instead of being emitted into the atmosphere, and excessive heat loss caused by the two separate processes also could be almost completely avoided. This paper presents an experimental study on the intrinsic chemical kinetics mechanisms of this new efficient one-step technology. By applying each of the most likely solid-state kinetic models, the kinetic parameters of the two reactions that reacted during the dolomite decomposition stage and magnesium reduction stage were evaluated, and the kinetic models that best verify the experimental data were attempted. For the dolomite decomposition stage of the one-step technology, the equation of the chemical kinetic model can be represented by α2/2 = k D1τ in the temperature range of 1173–1473 K, and the apparent activation energy was determined to be 160.6 kJ mol–1. For the magnesium reduction stage of the one-step technology, the surface reaction chemical kinetic model 1 – (1 – β)1/3= k Sτ described very satisfactorily the experimental values for the different reduction temperature. Then, a one-step model incorporating the chemical reaction kinetics of the dolomite decomposition stage and the magnesium reduction stage and heat conduction was first developed. The simulations of the impact of heating temperature on the dolomite decomposition stage and magnesium reduction stage were carried out in the reduction retorts of the furnace utilizing this model. The distribution of dolomite decomposition extent in the retorts, the total extent of dolomite decomposition with time, the distribution of magnesium reduction extent in the retorts, and the total extent of magnesium reduction with time were studied in detail. The analysis showed that the one-step technology is effective in not only reducing the cycle time of dolomite decomposition stage and magnesium reduction stage but also saving energy.

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Calcined Dolomite: Alternative to Lime for Minimizing Undesirable Element Leachability from Fly Ash

Cited by 8 publications

References 18 publications

Thermal Decomposition of Hydrocalumite over a Temperature Range of 400–1500°C and Its Structure Reconstruction in Water

Thermal Decomposition of Hydrocalumite over a Temperature Range of 400–1500°C and Its Structure Reconstruction in Water

Hydrotalcite and Hydrocalumite in Mortar Binders from the Medieval Castle of Portilla (Álava, North Spain): Accurate Mineralogical Control to Achieve More Reliable Chronological Ages

Experimental and Numerical Studies on a One-Step Method for the Production of Mg in the Silicothermic Reduction Process

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