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Determination of hexavalent chromium in leather extracts by the diphenylcarbazide (IUC-18) procedure pitfalls and refinements / S. Jambunathan in JOURNAL OF THE SOCIETY OF LEATHER TECHNOLOGISTS & CHEMISTS (JSLTC), Vol. 84, N° 2 (03-04/2000)  

[article]  inJOURNAL OF THE SOCIETY OF LEATHER TECHNOLOGISTS & CHEMISTS (JSLTC) > Vol. 84, N° 2 (03-04/2000) . - p. 63-73 Titre : Determination of hexavalent chromium in leather extracts by the diphenylcarbazide (IUC-18) procedure pitfalls and refinements Type de document : texte imprimé Auteurs : S. Jambunathan, Auteur ; P. K. Dasgupta, Auteur Année de publication : 2000 Article en page(s) : p. 63-73 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Analyse spectrale Cuir -- Teneur en chrome hexavalent Cuirs et peaux -- Analyse Diphénylcarbazide Photométrie Spéciation (chimie) Index. décimale : 675.2 Préparation du cuir naturel. Tannage Résumé : The customary diphenylcarbazide (IUC-18) procedure and several modifications thereof have been studied with a view to accommodate coloured extracts and to improve the sensitivity of the procedure for determining the concentration of hexavalent chromium in leather samples. The unmodified IUC-18 procedure is generally inapplicable to leather samples that produce a coloured extract. Even otherwise, the sensitivity of the IUC-18 procedure is limited. We propose here a pre-bleaching procedure that allows reliable analysis of the majority of the samples studied based on results obtained with Induction Coupled Plasma-Optical Emission Spectrometry (ICP OES) of cation exchanged samples as the reference method. A liquid core waveguide based flow-through absorbance detector deployed in a flow injection format was utilized to significantly improve on the sensitivities normally attainable in the diphenylcarbazide method. Ion exchange of the samples through H+form cation exchangers has also been found to be essential to prevent gross overestimation of the Cr(V1) concentrations, presumably he interference occurs from the presence of other metals in the extract. Concentrations of Cr(VI) in cation exchanged, bleached leather extracts as low as 1 tg/l can be readily measured with inexpensive equipment. Note de contenu : - Speciation of Cr(III) and Cr(VI) by ion exchange pretreatment - Photometric methods for the measurement of chromium - The IUC-18 protocol and problems - Experimental : Reagents - Leather samples - Equipment - Results and discussion : Extraction profile of Cr (VI) from leather samples - ICP-OES as a reference method - Diphénylcarbazide method : Calibration results in the manual spectrophotometric procedure - Spectral characteristics of the DPC reaction product and the led source of flow injection measurement - Bleaching procedures En ligne : https://drive.google.com/file/d/1MaegzuuDm9WjqwhmbBa1opjtI7ye7gN4/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=41460 [article]

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Potential chemical mechanisms causing false positive results in hexavalent chromium determination / A. J. Long in JOURNAL OF THE SOCIETY OF LEATHER TECHNOLOGISTS & CHEMISTS (JSLTC), Vol. 84, N° 2 (03-04/2000)  

[article]  inJOURNAL OF THE SOCIETY OF LEATHER TECHNOLOGISTS & CHEMISTS (JSLTC) > Vol. 84, N° 2 (03-04/2000) . - p. 74-78 Titre : Potential chemical mechanisms causing false positive results in hexavalent chromium determination Type de document : texte imprimé Auteurs : A. J. Long, Auteur ; N. J. Cory, Auteur ; C. B. Wood, Auteur Année de publication : 2000 Article en page(s) : p. 74-78 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Analyse des défaillances (fiabilité) Chimie analytique Chrome trivalent -- Oxydation Cuir -- Teneur en chrome hexavalent Mimosa et constituants Oxydants Index. décimale : 675.2 Préparation du cuir naturel. Tannage Résumé : Chemical analysis has indicated the presence of hexavalent chromium in some leather samples. However, Cr VI is not used in the leather tanning process, and leather normally exhibits a reductive capacity. This research was designed to explain the anomaly. Our work shows that once in solution, at the elevated pH of the phosphate buffer used, certain leather process chemicals may be able to oxidise leachable Cr III, giving a "false positive" Cr VI result. Hydrogen peroxide was found to oxidise Cr III to Cr VI in the phosphate buffer. The peroxide was used as a surrogate for the transient-lived hydroperoxides formed during oil oxidation. Hence fatliquors are implicated indirectly. The oxidation reaction did not occur in an acetate buffer, which is within the natural pH range of most leathers. Acetate buffer spiking experiments demonstrated that Cr VI is stable at pH 4, validating the result. We attempted to identify specific leather chemicals able to cause the reaction. Surprisingly, mimosa was shown to oxidise Cr III in the buffer solution in a time dependent reaction. Although previous work has proven a direct relationship between fatliquor unsaturation and Cr VI result, results in solution were inconclusive but explainable. Magnesium ions added as an antioxidant reduced the Cr VI result by 60%, providing further evidence that an oxidation mechanism produces Cr VI during the phosphate buffer extraction procedure. By demonstrating that magnesium ions do not reduce Cr VI to Cr III, we may conclude that the majority of the Cr VI originally detected had been formed during the extraction, and was not present in the sample. Finally, work utilizing artificial perspiration as a potential substitute extraction solution provided further evidence that the official test method buffer causes false positive results. Note de contenu : - Effect of process chemicals and extraction buffer - Antioxidant effect - Table 1 : Effect of leather chemicals on Cr III oxidation - Table 2 : Oxidation of Cr III by mimosa in phosphate buffer - Table 3 : Effect of mimosa on Cr VI restes - Table 4 : Concentration of Cr VI in spiked extract buffers - Table 5 : Concentration of Cr VI in leather extracts - Table 6 : Evaluation of extraction buffers En ligne : https://drive.google.com/file/d/1PlJdFCmBJwSjhWsLF565-8lruQSdp7lv/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=41461 [article]

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A new methodology for the rapid determination of chromium in tanning floats / M. Dolors Borras in JOURNAL OF THE SOCIETY OF LEATHER TECHNOLOGISTS & CHEMISTS (JSLTC), Vol. 84, N° 2 (03-04/2000)  

[article]  inJOURNAL OF THE SOCIETY OF LEATHER TECHNOLOGISTS & CHEMISTS (JSLTC) > Vol. 84, N° 2 (03-04/2000) Titre : A new methodology for the rapid determination of chromium in tanning floats Type de document : texte imprimé Auteurs : M. Dolors Borras, Auteur ; J. M. Morera, Auteur ; A. Rius, Auteur ; R. M. Romero, Auteur Année de publication : 2000 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Bains de tannage -- Teneur en chrome Chimie analytique Index. décimale : 675.2 Préparation du cuir naturel. Tannage Résumé : A method for the determination of chromium in tanning floats is presented in this paper. The new method is based on spectrophotometry and multivariate calibration. Its main characteristics are rapidity and the fact that only deionized water is used as reagent. The sample is first diluted and then the visible spectrum is recorded. The spectrum is related to the chromium concentration in the sample through the use of a calibration function previously calculated by Partial Least Squares (PLS). The results obtained are comparable to those obtained by the classical methodology in terms of accuracy (3.3%). Systematic errors are not detected at a 95% confidence level. Note de contenu : - Theoretical background : Multivariate calibration - Experimental : Instrumentation - Software - Samples - Reagents and procedures - Table 1 : Reference and predicted concentration of chromic oxide for the 23 samples used. The relative error for each sample is also shown En ligne : https://drive.google.com/file/d/1fcdf4m8V2FG2V2BOYU6GoCDgOMo2QZmY/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=41462 [article]

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A novel chromium-iron tanning agent cross-fertilization in solo tannage / P. Thanikaivelan in JOURNAL OF THE SOCIETY OF LEATHER TECHNOLOGISTS & CHEMISTS (JSLTC), Vol. 84, N° 2 (03-04/2000)  

[article]  inJOURNAL OF THE SOCIETY OF LEATHER TECHNOLOGISTS & CHEMISTS (JSLTC) > Vol. 84, N° 2 (03-04/2000) . - p. 82-87 Titre : A novel chromium-iron tanning agent cross-fertilization in solo tannage Type de document : texte imprimé Auteurs : P. Thanikaivelan, Auteur ; V. Geetha, Auteur ; Jonnalagadda Raghava Rao, Auteur ; Kalarical Janardhanan Sreeram, Auteur ; Balachandran Unni Nair, Auteur Année de publication : 2000 Article en page(s) : p. 82-87 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Agents de tannage Caractérisation Chimie analytique Chrome Cuirs et peaux -- Propriétés mécaniques Cuirs et peaux -- Propriétés physiques Fer Tannage minéral Tannage dans lequel interviennent différents minéraux. Le plus répandu est le tannage aux sels de chrome, mais aussi à l’aluminium Index. décimale : 675.2 Préparation du cuir naturel. Tannage Résumé : Ecological pressures on chromium have now forced the leather industry to look for possible alternatives. Since chromium appears to be indespensible to the leather industry, we must look for low chrome technology. In this connection, the present study concerns iron as a tanning agent along with chromium in a selected ligand environment. The study reveals that the exhaustions of both the metals were above 90% with shrinkage temperature above 115 C. The negative attributes associated with iron tanning such as deterioration and darkening of colour on ageing were negated with this product. In view of improved organoleptic properties coupled with enhanced physico-chemical properties, it is appropriate to promote the novel chromium-iron tanning agent to replace basic chromium sulphate in tanning with the slogan "chrome saver approach". The work provides a starting point for the revival of iron tannage, opening new avenues to eco-friendly leather processing. Note de contenu : - Experimental : Preparation of Cr-Fe tanning salt - Characterisation of the tanning salt - Tanning trials and examination of the leather : Differential Scanning Calorimetric analysis of the tanned leather - Scanning Electron Microscope analysis - Ageing—effects on strength - Ageing-effects on colour - Chemical and physical analysis - Results and disussion - Table 1 : Constituents and characteristics of Cr-Fe tanning salt - Table 2 : Spent tan liquor analysis and shrinkage temperature values - Table 3 : Tensile strength and % elongation at break measurements before and after ageing for one year - Table 4 : Physical properties of Cr-Fe tanned leathers - Table 5 : Chemical constituents in the Cr-Fe tanned leather En ligne : https://drive.google.com/file/d/1LVzLk_83CO5uYh9rLzyXwlEonqIoqSkQ/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=41463 [article]

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Chrome-free tannage by sequential treatment with synthetic resin and aluminium or titanium / S. Gangopadhyay in JOURNAL OF THE SOCIETY OF LEATHER TECHNOLOGISTS & CHEMISTS (JSLTC), Vol. 84, N° 2 (03-04/2000)  

[article]  inJOURNAL OF THE SOCIETY OF LEATHER TECHNOLOGISTS & CHEMISTS (JSLTC) > Vol. 84, N° 2 (03-04/2000) . - p. 88-93 Titre : Chrome-free tannage by sequential treatment with synthetic resin and aluminium or titanium Type de document : texte imprimé Auteurs : S. Gangopadhyay, Auteur ; S. Lahiri, Auteur ; P. K. Gangopadhyay, Auteur Année de publication : 2000 Article en page(s) : p. 88-93 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Aluminium L'aluminium est un élément chimique, de symbole Al et de numéro atomique 13. C’est un métal pauvre, malléable, de couleur argent, qui est remarquable pour sa résistance à l’oxydation13 et sa faible densité. C'est le métal le plus abondant de l'écorce terrestre et le troisième élément le plus abondant après l'oxygène et le silicium ; il représente en moyenne 8 % de la masse des matériaux de la surface solide de notre planète. L'aluminium est trop réactif pour exister à l'état natif dans le milieu naturel : on le trouve au contraire sous forme combinée dans plus de 270 minéraux différents, son minerai principal étant la bauxite, où il est présent sous forme d’oxyde hydraté dont on extrait l’alumine. Il peut aussi être extrait de la néphéline, de la leucite, de la sillimanite, de l'andalousite et de la muscovite. L'aluminium métallique est très oxydable, mais est immédiatement passivé par une fine couche d'alumine Al2O3 imperméable de quelques micromètres d'épaisseur qui protège la masse métallique de la corrosion. On parle de protection cinétique, par opposition à une protection thermodynamique, car l’aluminium reste en tout état de cause très sensible à l'oxydation. Cette résistance à la corrosion et sa remarquable légèreté en ont fait un matériau très utilisé industriellement. L'aluminium est un produit industriel important, sous forme pure ou alliée, notamment dans l'aéronautique, les transports et la construction. Sa nature réactive en fait également un catalyseur et un additif dans l'industrie chimique ; il est ainsi utilisé pour accroître la puissance explosive du nitrate d'ammonium. Essais (technologie) Tannage combiné Le tannage combiné se dit des tannages qui allient deux familles ou genre de tannage pour obtenir un résultat additionnant les qualités complémentaires des tannins mis en Å“uvre par exemple Chrome-Végétal ou Chrome-Synthétique Tannage minéral Tannage dans lequel interviennent différents minéraux. Le plus répandu est le tannage aux sels de chrome, mais aussi à l’aluminium Tannage synthétique Titane Index. décimale : 675.2 Préparation du cuir naturel. Tannage Résumé : Severe limitations imposed on the water authorities in developed countries on the discharge of chromium in tannery effluents have developed a keen interest to find an alternative to chrome tanning. A sequential tanning procedure using synthetic resins prepared from urea or dicyanidiamide, phenolic compounds, sulphonated phenolic compounds and formaldehyde followed by masked aluminium or titanium salt has been developed. The method has produced white full leather having a shrinkage temperature up to 100°C. Leather produced by the method requires higher levels of fatliquor and can withstand relatively severe dye bath conditions. Note de contenu : - Materials and reagents - Tanning trials En ligne : https://drive.google.com/file/d/1HlNUjSzfz071-FTL4hkQ0KtQ7f8GXtLF/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=41464 [article]

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The environmental impact of waste chromium of tannery / B. Chattopadhyay in JOURNAL OF THE SOCIETY OF LEATHER TECHNOLOGISTS & CHEMISTS (JSLTC), Vol. 84, N° 2 (03-04/2000)  

[article]  inJOURNAL OF THE SOCIETY OF LEATHER TECHNOLOGISTS & CHEMISTS (JSLTC) > Vol. 84, N° 2 (03-04/2000) . - p. 94-100 Titre : The environmental impact of waste chromium of tannery Type de document : texte imprimé Auteurs : B. Chattopadhyay, Auteur ; S. Datta, Auteur ; A. Chatterjee, Auteur Année de publication : 2000 Article en page(s) : p. 94-100 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Chimie analytique Eaux usées -- Teneur en chrome Environnement -- Etudes d'impact Pollution Index. décimale : 675.2 Préparation du cuir naturel. Tannage Résumé : Six different sampling stations on tannery wastewater carrying canais and a wastewater-fed agriculture pond have been studied to estimate the concentration of total chromium of composite tannery effluents, stabilized tannery wastewater, tannery sludge, bottom sediments of the wastewater carrying canal and the soifs from agricultural plots which use wastewater in irrigation and sludge/sediments as landfill. These study sites are located in the east Calcutta wetland ecosystem (lat. 22°33'-22°50'N ; long. 88°25'-88°35'E), the biggest urban wetland ecosystem covering 12 500 ha, which includes 286 wastewater-fed fish ponds spread over 3832.27 ha (over 30 % of the total wetland area), producing 10 915 metric tonnes of fish annually. This wetland area has taken the load of wastes from Calcutta tannery agglomerates for nearly a century. Total Cr accumulation in bone, gill, muscle and liver tissues of six fish species and in peel and pulp of waterchestnut, cultivated in wastewater-fed aquaculture ponds, have been estimated. Total Cr concentration of roots, stems, leaves and fruits of important vegetable plants cultivated in the adjoining contaminated areas have also been estimated. Total Cr concentration in effluent (0.025-1.70 mgr') and sludge/sediments (0.125-59.86 g kg') have been recorded. Hexavalent Cr in sludge/sediment/soil varied from 0.00765 to 24.319 g kg". Total Cr concentration in different plant parts (4.97 4691.81 mg kg" dry wt.) and in net plankton (2.28 g kg" dry wt.) and fish tissues (0.96 181.82 mg kg dry wt.) have never been observed to be limiting to growth. Note de contenu : - Chromium in wastewater - Chromium in soil-sludge - Chromium in plants - Chromium in fishes - Table 1 : Trivalent and hexavalent Cr content (mean value in g kg') of tannery sludge/sediments - Table 2 : Total Cr content (mean value in mg kg' dw) of plants grown on tannery sludge and contaminated sites En ligne : https://drive.google.com/file/d/1ltsRjwbLJco2gVJUz4emnIv3YB58ilXB/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=41465 [article]

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