scholarly journals Investigation on Vanadium Chemistry in Basic-Oxygen-Furnace (BOF) Slags—A First Approach

Metals ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1869
Author(s):  
Sophie Wunderlich ◽  
Thomas Schirmer ◽  
Ursula E.A. Fittschen
Keyword(s):  
Economic Value ◽  
Basic Oxygen Furnace ◽  
Oxidation States ◽  
Environmental Toxicity ◽  
X Ray Diffraction ◽  
Average Amount ◽  
Basic Oxygen ◽  
X Ray ◽  
Bof Slag ◽  
Component Models

Basic oxygen furnace (BOF) slag accounts for the majority of all residual materials produced during steelmaking and may typically contain certain transition metals. Vanadium, in particular, came into focus in recent years because of its potential environmental toxicity as well as its economic value. This study addresses the vanadium chemistry in BOF slags to better understand its recovery and save handling of the waste stream. The experimental results from the electron probe microanalysis (EPMA) study show that vanadium is preferably incorporated in calcium orthosilicate-like compounds (COS), with two variations occurring, a low vanadium COS (COS-Si) (approx. 1 wt.%), and a high vanadium COS (COS-V) (up to 18 wt.%). Additionally, vanadium is incorporated in dicalcium ferrite-like compounds (DFS) with an average amount of 3 wt.%. Using powder x-ray diffraction analysis (PXRD), EPMA, and virtual component models, stoichiometric formulas of the main vanadium-bearing phases were postulated. The stoichiometries give an estimate of the oxidation states of vanadium in the respective hosts. According to these results, trivalent vanadium is incorporated on the Fe-position in dicalcium ferrite solid solution (DFS), and V4+ and V5+ are incorporated on the Si-position of the COS.

scholarly journals Time-Dependent Strength Behavior, Expansion, Microstructural Properties, and Environmental Impact of Basic Oxygen Furnace Slag-Treated Marine-Dredged Clay in South Korea

2021 ◽  
Vol 13 (9) ◽  
pp. 5026
Author(s):  
Gyeong-o Kang ◽  
Jung-goo Kang ◽  
Jin-young Kim ◽  
Young-sang Kim
Keyword(s):  
Particle Size ◽  
Environmental Impact ◽  
South Korea ◽  
Mechanical Characteristics ◽  
Basic Oxygen Furnace ◽  
Microstructural Properties ◽  
Compression Tests ◽  
Basic Oxygen ◽  
Strength Behavior ◽  
Bof Slag

The aim of this study was to investigate the mechanical characteristics, microstructural properties, and environmental impact of basic oxygen furnace (BOF) slag-treated clay in South Korea. Mechanical characteristics were determined via the expansion, vane shear, and unconfined compression tests according to various curing times. Scanning electron microscopy was conducted to analyze microstructural properties. Furthermore, environmental impacts were evaluated by the leaching test and pH measurements. According to the results, at the early curing stage (within 15 h), the free lime (F-CaO) content of the BOF slag is a significant factor for developing the strength of the adopted sample. However, the particle size of the BOF slag influences the increase in the strength at subsequent curing times. It was inferred that the strength behavior of the sample exhibits three phases depending on various incremental strength ratios. The expansion magnitude of the adopted samples is influenced by the F-CaO content and also the particle size of the BOF slag. Regarding the microstructural properties, the presence of reticulation structures in the amorphous gels with intergrowths of rod-like ettringite formation was verified inside the sample. Finally, the pH values and heavy metal leachates of the samples were determined within the compatible ranges of the threshold effect levels in the marine sediments of the marine environment standard of the Republic of Korea.

scholarly journals Component Modification of Basic Oxygen Furnace Slag with C4AF as Target Mineral and Application

2021 ◽  
Vol 13 (12) ◽  
pp. 6536
Author(s):  
Yanrong Zhao ◽  
Pengliang Sun ◽  
Ping Chen ◽  
Xiaomin Guan ◽  
Yuanhao Wang ◽  
...  
Keyword(s):  
Intermediate Phase ◽  
Raw Materials ◽  
Activity Index ◽  
Basic Oxygen Furnace ◽  
Hydration Products ◽  
Basic Oxygen ◽  
Bof Slag ◽  
Mineral Compositions ◽  
Slag Component ◽  
Basic Oxygen Furnace Slag

In this paper, a new method of basic oxygen furnace (BOF) slag component modification with a regulator was studied. The main mineral was designed as C4AF, C2S and C3S in modified BOF slag, and the batching method, mineral compositions, hydration rate, activation index and capability of resisting sulfate corrode also were studied. XRD, BEI and EDS were used to characterize the mineral formation, and SEM was used to study the morphology of hydration products. The results show that most inert phase in BOF slag can be converted into active minerals of C4AF and C2S through reasonable batching calculation and the amount of regulating agent. The formation of C4AF and C2S in modified BOF slag is better, and a small amount of MgO is embedded in the white intermediate phase, but C3S is not detected. With the increase in the CaO/SiO2 ratio in raw materials, the CaO/SiO2 ratio of calcium silicate minerals in modified BOF slag increases, the contents of f-CaO are less than 1.0%, and the activity index improves. Compared with the BOF slag, the activity index and exothermic rate of modified BOF slag improved obviously, and the activity index of 90 days is close to 100%. With the increase in modified BOF slag B cement, the flexural strength decrease; however, the capability of resisting sulfate corrode is improved due to the constant formation of a short rod-like shape ettringite in Na2SO4 solution and the improvement of the structure densification of the hydration products.

scholarly journals Simulated Experiment Study of Factors Influencing the Hydration Activity of f-CaO in Basic Oxygen Furnace Slag

2016 ◽  
Vol 2016 ◽  
pp. 1-15 ◽  
Author(s):  
Ruiquan Jia ◽  
Jiaxiang Liu
Keyword(s):  
Solid Solutions ◽  
Volume Expansion ◽  
Basic Oxygen Furnace ◽  
Hydration Reaction ◽  
Basic Oxygen ◽  
Activity Sequence ◽  
Bof Slag ◽  
Iron Phase ◽  
Calcium Iron ◽  
Iron Manganese

The compositions and formation process of f-CaO in BOF slag were revealed and simulated to understand its expansion rules and why its hydration activity is low. BSE showed the compositions of f-CaO, which included calcium iron phase and calcium iron manganese phase, were diverse. The hydration activity sequence was Ca2Fe2O5 and Ca3Fe1.5Mn1.5O8 in tricomponent f-CaO < CaO in tricomponent f-CaO < monocomponent f-CaO; only Ca2Fe2O5 and Ca3Fe1.5Mn1.5O8 were hard to hydrate, and the volume expansion rates of the tricomponent f-CaO varied with different compositions. Inductively, in BOF slag, the hydration activity sequence was solid solutions CaO-FeOx and CaO-FeOx-MnOy in tricomponent f-CaO < CaO in tricomponent f-CaO < monocomponent f-CaO; the volume expansion rates of tricomponent f-CaO changed with different compositions, and CaO-FeOx and CaO-FeOx-MnOy were difficult to hydrate. The reason why solid solutions CaO-FeOx and CaO-FeOx-MnOy were hard to hydrate was that their hydration reaction driving force, which is the absolute value of standard molar reaction Gibbs functions, decreased.

scholarly journals Growth, Stratification, and Liberation of Phosphorus-Rich C2S in Modified BOF Steel Slag

Materials ◽  
2020 ◽  
Vol 13 (1) ◽  
pp. 203 ◽  
Author(s):  
Lei Rao ◽  
Yuanchi Dong ◽  
Mancheng Gui ◽  
Yaohui Zhang ◽  
Xingmei Shen ◽  
...  
Keyword(s):  
Solid Solution ◽  
Phosphorus Content ◽  
Steel Slag ◽  
Basic Oxygen Furnace ◽  
Holding Time ◽  
Basic Oxygen ◽  
Free Particles ◽  
Bof Slag ◽  
Grinding Time

Basic oxygen furnace (BOF) slag was modified by adding 3.5% SiO2 and holding at 1673 K for 0, 5, 40, 90, 240, or 360 min. Kilo-scale modification was also carried out. The growth, stratification, and liberation of P-rich C2S in the modified slag were investigated. The optimum holding time was 240 min, and 90% of C2S grains were above 30 μm in size. The phosphorus content increased with holding time, and after modification, the phosphorus content in C2S was nearly three times higher than that in the original slag (2.23%). Obvious stratification of C2S was observed in the kilo-scale modification. Upper C2S particles with a relatively larger size of 20–110 μm was independent of RO (FeO-MgO-MnO solid solution) and spinel, which is favorable for liberation. Lower C2S was less than 3 μm and was embedded in spinel, which is not conducive to liberation. The content of phosphorus in upper C2S (6.60%) was about twice that of the lower (3.80%). After grinding, most of the upper C2S existed as free particles and as locked particles in the lower. The liberation degree of C2S in the upper increased with grinding time, from 86.02% to 95.92% in the range of 30–300 s, and the optimum grinding time was 180 s. For the lower slag grinding for 300 s, the liberation degree of C2S was 40.07%.

scholarly journals Effect of basic oxygen furnace slag particle size on sequestration of carbon dioxide from landfill gas

2019 ◽  
Vol 37 (5) ◽  
pp. 469-477 ◽  
Author(s):  
Krishna R. Reddy ◽  
Archana Gopakumar ◽  
Raksha K. Rai ◽  
Girish Kumar ◽  
Jyoti K. Chetri ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Particle Size ◽  
Inner Core ◽  
Landfill Gas ◽  
Particle Surface ◽  
Basic Oxygen Furnace ◽  
Column Experiments ◽  
Basic Oxygen ◽  
Slag Particle ◽  
Bof Slag

The mineral carbon sequestration capacity of basic oxygen furnace (BOF) slag offers great potential to absorb carbon dioxide (CO2) from landfill emissions. The BOF slag is highly alkaline and rich in calcium (Ca) containing minerals that can react with the CO2 to form stable carbonates. This property of BOF slag makes it appealing for use in CO2 sequestration from landfill gas. In a previous study, CO2 and CH4 removal from the landfill gas was investigated by performing batch and column experiments with BOF slag under different moisture and synthetic landfill gas exposure conditions. The study showed two stage CO2 removal mechanism: (1) initial rapid CO2 removal, which was attributed to the carbonation of free lime (CaO) and portlandite [(Ca(OH)2)], and (2) long-term relatively slower CO2 removal, which was attributed to be the gradual leaching of Ca2+ from minerals (calcium-silicates) present in the BOF slag. Realising that the particle size could be an important factor affecting total CO2 sequestration capacity, this study investigates the effect of gradation on the CO2 sequestration capacity of the BOF slag under simulated landfill gas conditions. Batch and column experiments were performed with BOF slag using three gradations: (1) coarse (D50 = 3.05 mm), (2) original (D50 = 0.47 mm), and (3) fine (D50 = 0.094 mm). The respective CO2 sequestration potentials attained were 255 mg g−1, 155 mg g−1, and 66 mg g−1. The highest CO2 sequestration capacity of fine BOF slag was attributed to the availability of calcium containing minerals on the slag particle surface owing to the highest surface area and shortest leaching path for the Ca2+ from the inner core of the slag particles.

Alkin-Komplexe des Rheniums in hohen Oxidationsstufen / Alkyne Complexes of Rhenium in High Oxidation States

1990 ◽  
Vol 45 (6) ◽  
pp. 876-886 ◽  
Author(s):  
Wolfgang A. Herrmann ◽  
Josef K. Felixberger ◽  
Josef G. Kuchler ◽  
Eberhardt Herdtweck
Keyword(s):  
Diffraction Study ◽  
Scale Up ◽  
Oxidation States ◽  
X Ray Diffraction ◽  
X Ray ◽  
Reducing Conditions ◽  
Molar Amount ◽  
High Oxidation ◽  
Alkyne Complexes ◽  
Type 3

The class of π-alkyne complexes of metals in medium and high oxidation states has been extended by the type CH3ReO2(RC≡CR′) (3a—i). Exchange of alkyne for oxo ligands under reducing conditions has been employed as a new general synthesis. Compounds 3 are thus obtained by reaction of methyltrioxorhenium(VII) (1) with the alkynes 2a—i in the presence of a ca. 1.1-fold molar amount of polymer-bound triphenylphosphane as reducing agent (desoxygenation). The structural characterization was carried out for the example of the tolan complex 3 e by virtue of a single-crystal X-ray diffraction study at —80 °C, according to which the description of compounds 3 as “rhenacyclopropenes” seems justified. Evidence from NMR investigations of 3 a and 3 c shows that no fast rotation of the respective alkyne ligand around the axis to the metal atom occurs on the NMR time scale up to at least 105 °C. A minimal rotation barrier of approximately 20 kcal/mol is thus to be estimated. Reaction of type 3 compounds (R = R′ = CH3, b; R = R′ = C2H5, c) with polymer-bound triphenylphosphane under more drastic conditions (boiling toluene) for two days effects further reduction, with the dinuclear, diamagnetic rhenium(IV) complexes 4b and 4c, resp., being formed. Sterically demanding alkynes (e.g., R = R′ = Si(CH3)3, C6H5) seem to prevent this type of reaction. According to an X-ray diffraction study, 4b has an equilateral Re2O-triangular core geometry, with the ligands O, CH3, and butyne(2) arranged in such a way that C2-symmetry results. The alkyne complexes reported here are the first ones of tetra- and pentavalent rhenium.

The crystal structures of the mixed-valence tellurium oxysalts tlapallite, (Ca,Pb)3CaCu6[Te4+3Te6+O12]2(Te4+O3)2(SO4)2·3H2O, and carlfriesite, CaTe4+2Te6+O8

2019 ◽  
Vol 83 (4) ◽  
pp. 539-549 ◽  
Author(s):  
Owen P. Missen ◽  
Anthony R. Kampf ◽  
Stuart J. Mills ◽  
Robert M. Housley ◽  
John Spratt ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Mixed Valence ◽  
Oxidation States ◽  
Structural Refinement ◽  
X Ray Diffraction ◽  
X Ray ◽  
Naturally Occurring ◽  
The One ◽  
Micro Analysis ◽  
Secondary Bonding

ABSTRACTThe crystal structure of tlapallite has been determined using single-crystal X-ray diffraction and supported by electron probe micro-analysis, powder diffraction and Raman spectroscopy. Tlapallite is trigonal, space groupP321, witha= 9.1219(17) Å,c= 11.9320(9) Å andV= 859.8(3) Å3, and was refined toR1= 0.0296 for 786 reflections withI> 2σ(I). This study resulted from the discovery of well-crystallised tlapallite at the Wildcat prospect, Utah, USA. The chemical formula of tlapallite has been revised to (Ca,Pb)3CaCu6[Te4+3Te6+O12]2(Te4+O3)2(SO4)2·3H2O, or more simply (Ca,Pb)3CaCu6Te4+8Te6+2O30(SO4)2·3H2O, from H6(Ca,Pb)2(Cu,Zn)3(TeO3)4(TeO6)(SO4). The tlapallite structure consists of layers containing distorted Cu2+O6octahedra, Te6+O6octahedra and Te4+O4disphenoids (which together form the new mixed-valence phyllotellurate anion [Te4+3Te6+O12]12−), Te4+O3trigonal pyramids and CaO8polyhedra. SO4tetrahedra, Ca(H2O)3O6polyhedra and H2O groups fill the space between the layers. Tlapallite is only the second naturally occurring compound containing tellurium in both the 4+and 6+oxidation states with a known crystal structure, the other being carlfriesite, CaTe4+2Te6+O8. Carlfriesite is the predominant secondary tellurium mineral at the Wildcat prospect. We also present an updated structure for carlfriesite, which has been refined toR1= 0.0230 for 874 reflections withI> 2σ(I). This updated structural refinement improves upon the one reported previously by refining all atoms anisotropically and presenting models of bond valence and Te4+secondary bonding.

Oxidation of Sn Thin Films to SnO2. Micro-Raman Mapping and X-ray Diffraction Studies

1998 ◽  
Vol 13 (9) ◽  
pp. 2457-2460 ◽  
Author(s):  
Luigi Sangaletti ◽  
Laura E. Depero ◽  
Brigida Allieri ◽  
Francesca Pioselli ◽  
Elisabetta Comini ◽  
...  
Keyword(s):  
Thin Film ◽  
Phase Segregation ◽  
Oxidation States ◽  
Inhomogeneous Distribution ◽  
Raman Mapping ◽  
X Ray Diffraction ◽  
X Ray ◽  
Optical Inspection ◽  
Degree Of Oxidation ◽  
Sample Homogeneity

The oxidation of tin layers deposited onto alumina substrates is investigated with the aim to identify the different steps of the process and obtain information on the sample homogeneity, phase segregation, and degree of oxidation. It is shown that at least three phases coexist at 450 °C, Sn, SnO, and SnO2, and remarkable inhomogeneities, already visible at an optical inspection, are found in the thin film. A micro-Raman mapping of the layer shows that these inhomogeneities are related to the presence of different Sn oxidation states, as evidenced by the inhomogeneous distribution of SnO and SnOx Raman bands. The thin film becomes homogeneous after annealing treatments above 550 °C, where only the SnO2 cassiterite phase is detected.

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