Technical note Cr(VI) generation during milling

Beukes, J. P.; Guest, R.N.

doi:10.1016/s0892-6875(01)00022-x

Cited by 16 publications

(10 citation statements)

References 2 publications

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“…It is a surprising result that a trace amount of chro- mate compound generates during smelting in spite of strong reductive conditions. However, Beukes and Guest [7] have reported a similar result that has been explained as the milling practice of ferrochromium slag could alter the oxidation state of chromium. In crushing and grinding operations, the atmospheric oxygen and also the heat evolving by the result of friction may cause or contribute to a partial oxidation of metallic or oxidic chromium in FS.…”

Section: Results Of Sequential Washing Of Fsmentioning

confidence: 73%

“…In a study dealing with the process water of metal recovery from slag, it has been reported that Cr has been detected as chromate in the processing water, which may create chromium pollution [6]. In another study, it has been reported that milling practice of ferrochromium slag could alter the oxidation state of chromium and cause the threat of Cr(VI) releasing [7]. On the other hand, it has been indicated that other solid wastes such as bag filter dust or its sludge produced during the ferrochromium production contain high levels of soluble hexavalent chromium [8][9][10][11].…”

Section: Introductionmentioning

confidence: 99%

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Hexavalent chromium removal by ferrochromium slag

Erdem

Altundoğan

Turan

et al. 2005

Journal of Hazardous Materials

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The aim of this study is to demonstrate the potential of Cr(VI) generation during jigging operation applied for ferrochrome recovery from slag. The Cr(VI) concentrations of water contacted with ferrochromium slag (W/FS=10) in a closed cycle after 50 batches were found as 0.61 mg/l. Also, reduction of Cr(VI) to Cr(III) and a subsequent precipitation of Cr(III) by using ferrochrome slag (FS) in a model solution has been aimed. The effects of amount of acid, contact time, FS dosage, initial Cr(VI) concentration and temperature on the Cr(VI) reduction have been studied through the batch runs. The amount of acid has been found to be the most effective parameter affecting the Cr(VI) reduction. A 10 g/l FS dosage and 3.5 ml/l H2SO4 (5M) are sufficient to reduce all Cr(VI) in the model solution containing 10mg/l Cr(VI) and for contact time of 60 min at 25 degrees C. In reduced solutions, precipitation of metal ions has been studied by using extra FS. A 60 g/l dosage of fresh FS can precipitate all Cr(III) and Fe ions in the reduced solution. Thus, it has been demonstrated that the treatment of jigging water stream to be generated in a ferrochrome plant containing Cr(VI) can be accomplished by using ferrochromium slag and sulphuric acid. Also, it has been determined that solid residues of the process are environmentally stable by applying TCLP test.

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Section: Results Of Sequential Washing Of Fsmentioning

confidence: 73%

Section: Introductionmentioning

confidence: 99%

Hexavalent chromium removal by ferrochromium slag

Erdem

Altundoğan

Turan

et al. 2005

Journal of Hazardous Materials

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“…All results reported are mean values calculated from triplicate repetition of particular experimental conditions and subsequent Cr(VI) analysis. Since it is well known that Cr(VI) can be generated during the milling of chromite, [25,34] the Cr(VI) contents of the sizefractioned ores samples were determined to establish a baseline. These baseline values were subtracted from the Cr(VI) contents determined after exposure to heat, to reflect the real Cr(VI) conversion.…”

Section: G Expressing Cr(vi) Conversionmentioning

confidence: 99%

Cr(VI) Generation During Flaring of CO-Rich Off-Gas from Closed Ferrochromium Submerged Arc Furnaces

Preez

Beukes

Zyl

2014

Metall Mater Trans B

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Ferrochromium (FeCr) is the only source of new Cr units used in stainless steel production, which is a vital modern day alloy, making FeCr equally important. Small amounts of Cr(VI) are unintentionally formed during several FeCr production steps. One such production step is the flaring of CO-rich off-gas from closed submerged arc furnaces (SAF), for which Cr(VI) formation is currently not quantified. In this study, the influence of flaring temperature, size of the particles passing through the flare, and retention time within the flame were investigated by simulating the process on laboratory scale with a vertical tube furnace. Multiple linear regression (MLR) analysis was conducted on the overall dataset obtained, which indicated that retention time had the greatest impact on pct Cr(VI) conversion, followed by particle size and temperature. The MLR analysis also yielded an optimum mathematical solution, which could be used to determine the overall impact of these parameters on pct Cr(VI) conversion. This equation was used to determine realistic and unrealistic worst-case scenario pct Cr(VI) conversions for actual FeCr SAFs, which yielded 2.7 9 10 À2 and 3.5 9 10 À1 pct, respectively. These values are significantly lower than the current unsubstantiated pct Cr(VI) conversion used in environmental impact assessments for FeCr smelters, i.e., 0.8 to 1 pct.

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“…Son varios los métodos que se pueden utilizar para eliminar el cromo de las aguas residuales. Éstos incluyen la precipitación química, la degradación biológica, la adsorción, el intercambio iónico, la biosorción, la separación por membranas y los métodos electroquímicos [6,[56][57][58][59][60][61][62][63].…”

Section: "Tratamiento De Disoluciones Que Contienen Cromo Hexavalenteunclassified

“…La energía específica (Es) representa la energía consumida necesaria para eliminar un kilogramo de cromo en la unidad de tiempo y se puede determinar a partir de la ecuación (63). La energía específica consumida es un parámetro muy importante en los procesos electroquímicos que se puede relacionar con la viabilidad del proceso, puesto que está relacionado con los costes de operación, los cuales habrá que minimizar.…”

Section: Efecto De Las Concentraciones De Nacl Y H 2 So 4 Sobre La Enunclassified

Tratamiento de disoluciones que contienen cromo hexavalente mediante electrocoagulación con ánodos de hierro

Núñez¹,

Guadalupe²

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Son muchas las personas que de una u otra manera han contribuido a la realización de esta tesis, y a todas ellas quiero expresarles mi agradecimiento.En el plano académico, quiero agradecer al Departamento de Ingeniería Química y Nuclear, por haberme brindado la oportunidad de completar mi formación, realizando la tesis doctoral en este grupo de investigación.A mis directores de tesis, Valentín y Tere por su ayuda, ideas, consejos, comentarios, paciencia y por depositar su confianza en mí, pero sobre todo por su excepcional calidad humana.A mis compañeros del departamento de Ingeniería Química y Nuclear, por su apoyo y ayuda durante esta investigación, que con el tiempo se han convertido en amigos, gracias a todos, en especial a Virginia, Isaac y Carlos que se han convertido en parte de mi familia y han compartido conmigo los buenos y malos momentos en estos años.A mis amigos de siempre, y a los que he ido encontrando en el camino, Dulce, Edith, Itzma, Xitlali, Faby y todos los que me han hecho olvidar por un momento todas mis preocupaciones para disfrutar de su compañía y su cariño, a todos ellos, muchísimas gracias.Agradezco muy especialmente a mi familia, a mis padres Humberto y Loli, por confiar en mi, por todo el amor que me dan y por darme alas para volar, sin ustedes esto no hubiera sido posible, a mi hermana Ani por apoyarme en todo momento y estar allí para mi siempre, a mis hermanos Beto y Alex por su apoyo y consejos, a mis abuelitas Dalia y Mary por ser mujeres excepcionales y un gran ejemplo para mi, a todos gracias por estar conmigo en todo momento y por enseñarme que merece la pena esforzarse para conseguir lo que se desea.A mi esposo Germán que me ha acompañado a lo largo de este proceso, gracias por escucharme, por no permitir que desespere, por tu apoyo, tu amor incondicional y simplemente por ser parte de mi vida.

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Technical note Cr(VI) generation during milling

Cited by 16 publications

References 2 publications

Hexavalent chromium removal by ferrochromium slag

Hexavalent chromium removal by ferrochromium slag

Cr(VI) Generation During Flaring of CO-Rich Off-Gas from Closed Ferrochromium Submerged Arc Furnaces

Tratamiento de disoluciones que contienen cromo hexavalente mediante electrocoagulación con ánodos de hierro

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