In the past decades the increased use of chromium (Cr) in several anthropogenic activities and consequent contamination of soil and water have become an increasing concern. Cr exists in several oxidation states but the most stable and common forms are Cr(0), Cr(III) and Cr(VI) species. Cr toxicity in plants depends on its valence state. Cr(VI) as being highly mobile is toxic, while Cr(III) as ...
Chromium metal and ferrochromium alloy as well as chromium pigments are produced from chromite (iron chromium oxide, ...Cr(VI) and Cr(III) compounds dominate chromium chemistry, Cr(III) being 500–1000 × less toxic than Cr(VI).. Author: Jan Aaseth. Publisher: Academic Press ISBN: 9780128030738 Category: Page: 388 View: 399
Recovery of chromium from these slags is not only beneficial to increase the slag's economic potential but also favorable to solve the environmental problems induced by the chromium (VI) in the ...
12%Chromium has long been recognized as a toxic, mutagenic and carcinogenic metal. It is toxic to microorganism, plants, animals and humans. Chromium exists in environment in two stable forms: Cr(VI) and Cr(III). Cr(III) is less toxic and insoluble, while Cr(VI) is extremely toxic and highly soluble. Chromium is used in many industrial applications, but it poses a …
Ferro chrome slag may contain chromium in +3 and +6 oxidation states. Separation and determination of chromium content of the slag samples collected from Jindal Ferro Alloys Corporation, (Kottha ...
The present invention relates to a kind of Leaching of Vanadium from Vanadium slag containing chromium and the process of coproduction chromium-base alloy, comprise the steps: that (1) vanadium slag selective oxidation obtains calcining;(2) gained calcining leaching agent is leached vanadium extraction, obtain after solid-liquor separation containing vanadium leachate and tailings in ...
slag. It is worthy to investigate Cr(VI) reduction by using ferrochromium slag which contains iron and chromium mostly in metallic state as reductants. Further, oxide and silicate matrix of slag may partly adsorb chromates. Addi-tionally, after reduction, in a following step another por-tion of slag may be used to neutralize the reduced solu-
Chromium 01-21194809 Iron 01-21194652 CAS number Ferrochrome 1 1.2 Relevant identified uses of the substance and uses advised against This product is used as raw material for the manufacture of various grades of stainless steel, high chromium casting, and special steel. No uses advised against.
This study investigates the leaching behavior of hexavalent chromium (Cr (VI)) from both industrial electric arc furnace steel slag and steel slag modified with up to 2% wt Cr2O3.
Hexavalent chromium (Cr) is a toxic element causing serious environmental threat. Recently, more and more attention is paid to the bio-remediation of Cr (VI) in the contaminated soils. Cr (VI) remediation by indigenous bacteria in soils contaminated by chromium-containing slag at a steel-alloy facto …
Chromium alloy is a key ingredient in stainless steel production, and slag forms a significant proportion of the production process's output. To investigate how to avoid the leaching of Cr(VI) from stainless steel slag into the environment, we examined the effect of the FeO content on the stability of chromium in the CaO-SiO 2 -MgO-Al >2O3-Cr2O3 system in ...
Ferro chrome slag may contain chromium in +3 and +6 oxidation states. Separation and determination of chromium content of the slag samples collected from Jindal Ferro Alloys Corporation, (Kottha valasa, Visakhapatnam Dt.) has been carried out following extraction with benzene solutions of TOAO(0.01M). Maximum
The term "hexavalent chromium" is a shorthand designation for chemical compounds that contain the element chromium in the positive 6 valence state [written as Cr(VI) or Cr 6+].Metallic chromium is in the zero valence state and naturally occurring chromium oxide contains chromium in the positive 3 valence state, also called trivalent chromium or Cr(III).
The content of chromium VI in cement depends on the Cr content, mostly chromium III, of the raw material but also from the kiln lining and by chromium steel abrasion during the grinding process (CSTE/93/12/COM). ... Singapore have increasingly used slag from iron ore processing as a substitute. This results in lower chromium
The present invention relates to a method for reducing to metallic chromium the chromium oxide material found in slag formed in an electric arc furnace during the process of making stainless steel in that furnace. The chromium oxide content of the slag can be effectively reduced to a relatively low concentration by maintaining the slag in a liquid phase while at the same time blowing into the ...
mortar, is the chromium(VI) reduced to chromium(III) once the cement is thoroughly mixed with water. The same occurs when the extraction method is carried out in the laboratory (standard mortar method to EN 196-10) to determine the content of soluble chromium(VI). …
Background. Stainless steel slags generated in melting and refining operations are CaO-SiO 2-MgO rich with Cr 2 O 3, Al 2 O 3 and F-in minor quantities. A major issue is collapse of the slag structure on cooling as the high dicalcium silicate (C 2 S) content undergoes a phase transformation from β-C 2 S (monoclinic) to γ-C 2 S (orthorhombic). This phenomenon is accompanied by a volume ...
The chromium content in clinker samples from a Belgian study are shown in Table 5. In regards to Cr (VI) levels in clinker, a Spanish investigation reports Cr (VI) content of clinker between 8 and 20% of the total chromium content (Lizarraga 2003). The content of total chromium and Cr (VI) of cements are shown in Tables 6 and 7.
cancer have been found in chromium (VI) workers. There is an increased incidence of lung cancer in industrial workers exposed to chromium (VI) compounds. Please refer to IARC volume 23 for a more detailed discussion. Silicon: Can cause chronic bronchitis and narrowing of the airways.
Chromium content must be increased with increasing section size. In type D alloy, chromium levels range from 7 to 11% (typically 9%) for the purpose of producing eutectic carbides of the M 7 C 3 chromium carbide type, which are harder and less deleterious to toughness.
Removal of hexavalent chromium had attracted much attention as it is a hazardous contaminant. An electrocoagulation-like technology electro-reduction was applied. The chromium (VI) in the wastewater was reduced to chromium (III) by the electron supplied by electricity power and Fe2+, formed from corrosion of steel electrodes in acidic conditions.
for Cr(VI) in chromium-slag leakage with self-generated electricity. Dynamic leaching experiments of chromium-slag samples were conducted to survey the release and leaching behavior of Cr(VI).
The chromium content in clinker samples from a Belgian study are shown in Table 5. In regards to Cr (VI) levels in clinker, a Spanish investigation reports Cr (VI) content of clinker between 8 and 20% of the total chromium content (Lizarraga 2003). The content of total chromium and Cr (VI) of cements are shown in Tables 6 and 7.
Release behaviour of chromium from ferrochrome slag. Huge amount of ferrochrome slag, a solid waste is being generated from submerged electric arc furnace during manufacturing of ferrochrome alloy. The waste slag contains about 6–12% chromium as chromium oxide and it has the potentiality of releasing hazardous chromium compounds.
Chahak child and the crucible slag and a smithing slag layer. (Image: Rahil Alipour, UCL) Chromium alloys afford steel products an anti-corrosive quality, and dating to the 11th century this discovery represents the "first known use of chromium to make a steel alloy," and while chromium steel is similar to stainless steel, an alloy must have a chromium content of at least 10.5 per cent to ...
12%Chromium alloy is a key ingredient in stainless steel production, and slag forms a significant proportion of the production process's output. To investigate how to avoid the leaching of Cr(VI) from stainless steel slag into the environment, we examined the effect of the FeO content on the stability of chromium in the CaO-SiO2-MgO-Al2O3-Cr2O3 system in laboratory …
Chromium (VI) is much more toxic than chromium (III), for both acute and chronic exposures. (1,3,4) The respiratory tract is the major target organ for chromium (VI) following inhalation exposure in humans. Shortness of breath, coughing, and wheezing were reported in cases where an individual inhaled very high concentrations of chromium xide.
EPA-450/4-84-007G July 1984 Locating and Estimating Air Emissions From Sources of Chromium U.S ENVIRONMENTAL PROTECTION AGENCY Office of Air and Radiation
Chromium waste slag containing potentially hazardous levels of Cr(VI) compounds was used as fill material at more than 160 residential, industrial, and recreational sites. Persons living or working in the vicinity of the sites may have been exposed through inhalation, ingestion, or skin contact with contaminated soils and dusts [Fagliano ...
Seven alloy steel electrodes with chromium content vary- ing from 1.37 to 26.3 1 pet were used. The chemical com- ... which there is no transfer of chromium between metal and slag, is approximately 8.7 pet for flux D (MnO-Crz03-SOz) ... chromium content of the electrode on the silicon content of
Although someoxidation of chromium is unavoidable, the chromium oxide content ofthe slag should be kept as low as possible. Figure 6 shows the solubility'·6 of Cr20) and CaO.Cr20) in 1I CaO-SiO,-CaF2 melt at 1500°C. The Cr20) content at a double saturation ofCoO and CaO.Cr20) is approximately 2 per cent. The value of Lp at this slag 0,0 CaO ...
monoxide content gas may be used within the plant or flared. The molten alloy and slag that accumulate on the furnace hearth are removed at 1 to 5-hour intervals through the tap hole. Tapping typically lasts 10 to 15 minutes. Tap holes are opened with pellet shot from a gun, by drilling, or by oxygen lancing. The molten metal and slag flow from the
Here we demonstrate a calcifying ureolytic bacterium Bacillus sp. CS8 for the bioremediation of chromate (Cr(VI)) from chromium slag based on microbially induced calcite precipitation (MICP). A consolidated structure like bricks was prepared from chromium slags using bacterial cells, and five stage Cr(VI) sequential extraction was carried out to know their distribution …