Ageing of chromium(III)-bearing slag and its relation to the atmospheric oxidation of solid chromium(III)-oxide in the presence of calcium oxide

Pillay, Kriveshini; Blottnitz, Harro von; Petersen, Jochen

doi:10.1016/s0045-6535(03)00453-3

Cited by 95 publications

(56 citation statements)

References 15 publications

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“…Therefore, the rates of the oxidation reaction of Cr(III) were investigated in a number of long-term experiments using both original slag samples and mixtures of chromium and calcium oxides. 3) These experiments revealed that the oxidation rate of the chromium contained in the slag was an exponentially decreasing function of time, and the oxidation reaction almost ceased in the long term. Further, in the mixtures of calcium and chromium oxides, the oxidation reaction appeared to occur at the interfaces between the chromium oxide and calcium oxide phases under atmospheric oxygen, which results in the formation of calcium chromate.…”

Section: Introductionmentioning

confidence: 94%

Chemical State of Chromium in CaO–SiO2 Base Oxides Annealed under Different Conditions

et al. 2008

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In order to understand the formation mechanism of Cr(VI) in chromium-containing steel slag, X-ray diffractiometry (XRD), X-ray absorption spectroscopy (XAS) in the region of X-ray absorption near edge structure (XANES), and X-ray photoelectron spectroscopy (XPS) measurements were performed for analyzing the chromium contained in the model slag of CaO-SiO 2 base. The model slag was annealed under different temperatures and atmospheres to change the chemical state of chromium. XRD results showed that a diffraction peak that can be assigned to CaCrO 4 comprising of Cr(VI) was detected in the model-slag sample annealed under a high partial pressure of oxygen (air). XANES results showed that the Cr(VI) concentration in the slag increased by annealing under a high partial pressure of oxygen, while it was very low in the slag sample annealed under a low partial pressure of oxygen. The XANES results were consistent with the XRD results. The formation conditions of Cr(VI) were discussed on the basis of the thermodynamic characteristics of a Ca-Cr-O system. The XPS results for the slag surface were dependent on the leaching tests performed on the slag, while the XANES results were insensitive to the leaching tests. This indicates that Cr(VI) dissolved from only a surface layer of the model slag. The chromium that dissolved from the slag in an aqueous solution by the leaching test was also analyzed and was found to be in the form of Cr(VI); further, its concentration depended on the annealing conditions of the slag.

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Section: Introductionmentioning

confidence: 94%

Chemical State of Chromium in CaO–SiO2 Base Oxides Annealed under Different Conditions

et al. 2008

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“…After leaving the EAF process, the slag is cooled and stored for other utilizations. It has been found by some studies [2][3][4][5] that hexavalent Cr can be generated from Cr oxides in the EAF slag in the period of slag processing and storage. Hexavalent Cr is toxic and easily leachable from the slag, leading to water pollution and some economic and ecologic issues.…”

Section: Introductionmentioning

confidence: 99%

Effect of FeO on the formation of spinel phases and chromium distribution in the CaO-SiO2-MgO-Al2O3-Cr2O3 system

et al. 2013

Int J Miner Metall Mater

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Synthetic slag samples of the CaO-SiO2-MgO-Al2O3-Cr2O3 system were obtained to clarify the effect of FeO on the formation of spinel phases and Cr distribution. X-ray diffraction (XRD) and scanning electron microscopy (SEM) equipped with energy-dispersive spectroscopy (EDS), as well as the thermodynamic software FactSage 6.2, were used for sample characterization. The results show that the addition of FeO can decrease the viscosity of molten slag and the precipitation temperatures of melilite and merwinite. The solidus temperature significantly decreases from 1400 to 1250• C with the increase of FeO content from 0wt% to 6wt%. The addition of FeO could enhance the content of Cr in spinel phases and reduce the content of Cr in soluble minerals, such as merwinite, melilite, and dicalcium silicate. Hence, the addition of FeO is conducive to decreasing Cr leaching.

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“…On the other hand phases featured by high melting point can crystallize during the solidification, avoiding amorphous structures formation. For this reason, the correct balance of acid and basic species in the slags (MgO, CaO, FeO and SiO 2 ) is fundamental to obtain the favorable microstructure [10][11][12][13] and avoid chemical leaching. Acid species addition, i.e.…”

Section: Introductionmentioning

confidence: 99%

Survey about Safe and Reliable Use of EAF Slag

Barella

Gruttadauria

Magni³

et al. 2012

ISIJ Int.

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The demand of green and recycling technology has become, nowadays, a crucial issue for the scientific community. In this work, a preliminary approach for safe and reliable "black slag" use is discussed on chemical and microstructural characterization basis. Different EAF slag types, coming from several steelmaking plants, are analyzed. The characterization is aimed to explain the diffusion, dissolution and releasing mechanisms of the polluting elements that affect the black slags and avoid their recycle as alternative filler materials. Furthermore, the work focuses on the leaching inhibition of these dangerous species in the environment.Experiments involve SEM-EDS and SEM-EBS analysis and elution tests, according to the UNI EN 12457 standard, on high FeO content slag, on slag featured by chromium high content and on slag with low FeO content. The analysis allows to recognize the phases responsible for the polluting elements releasing and to identify the phases to be promoted in order to obtain a safe and inert by-product.

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Ageing of chromium(III)-bearing slag and its relation to the atmospheric oxidation of solid chromium(III)-oxide in the presence of calcium oxide

Cited by 95 publications

References 15 publications

Chemical State of Chromium in CaO–SiO2 Base Oxides Annealed under Different Conditions

Chemical State of Chromium in CaO–SiO2 Base Oxides Annealed under Different Conditions

Effect of FeO on the formation of spinel phases and chromium distribution in the CaO-SiO2-MgO-Al2O3-Cr2O3 system

Survey about Safe and Reliable Use of EAF Slag

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