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Testing aerobic degredation of the protein portion of filter cake after filtration of chrome tanned waste / M. Dvorackova in JOURNAL OF THE AMERICAN LEATHER CHEMISTS ASSOCIATION (JALCA), Vol. CII, N° 3 (03/2007)  

[article]  inJOURNAL OF THE AMERICAN LEATHER CHEMISTS ASSOCIATION (JALCA) > Vol. CII, N° 3 (03/2007) . - p. 77-84 Titre : Testing aerobic degredation of the protein portion of filter cake after filtration of chrome tanned waste Type de document : texte imprimé Auteurs : M. Dvorackova, Auteur ; J. Kupec, Auteur ; H. Mikulcakova, Auteur Année de publication : 2007 Article en page(s) : p. 77-84 Note générale : Bibliogr. Langues : Américain (ame) Index. décimale : 675 Technologie du cuir et de la fourrure Résumé : An example of utilizing tanning waste as a secondary raw material is enzymatic hydrolysis of chrome shavings, the result of which is collagen hydrolysate (commercially applicable ) and filter cake containing hydrated Cr2O3 contaminated with collagen residues. With a view to further potential utilisation of chrome cake, the content of collagen portion has to be reduced to a minimum. A possible solution, the subject of this presented work, is removal of the collagen portion through aerobic biological degradation in an aqueous or soil environment. This process was examined by means of biochemical oxygen consumption (standard CSN EN ISO 9408) and carbon dioxide production expressed as a percentage of theoretical production (standard ASTM 5209-92). The source of micro organisms was the commercially produced soil substrate and a soil extract prepared there from for inoculating aqueous environment. Using the described conditions, it was found that the collagen portion is removed from aqueous environment by 83% and from the soil by 58% (in approximately 80 hours). Due to its insolubility, chromic oxide does not exhibit toxic influence. En ligne : https://drive.google.com/file/d/1m-7GfH0_gaHisUVa3t9aQr1rr8svwfln/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=3363 [article]

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Critical appraisal of analytical procedures for the determination of CR(VI) in dyed leathers by 1,5 diphenylcarbazide spectrophotometry after sample dilutin or color removal / J. Scancar in JOURNAL OF THE AMERICAN LEATHER CHEMISTS ASSOCIATION (JALCA), Vol. CII, N° 3 (03/2007)  

[article]  inJOURNAL OF THE AMERICAN LEATHER CHEMISTS ASSOCIATION (JALCA) > Vol. CII, N° 3 (03/2007) . - p. 85-92 Titre : Critical appraisal of analytical procedures for the determination of CR(VI) in dyed leathers by 1,5 diphenylcarbazide spectrophotometry after sample dilutin or color removal Type de document : texte imprimé Auteurs : J. Scancar, Auteur ; R. Milacic, Auteur ; N. Bukovec, Auteur ; T. Osterman, Auteur Année de publication : 2007 Article en page(s) : p. 85-92 Note générale : Bibliogr. Langues : Américain (ame) Index. décimale : 675 Technologie du cuir et de la fourrure Résumé : Colored chemical species in leather extracts may contribute to the measurement signal in spectrophotometric determination of Cr(VI), resulting in false positive Cr(VI) concentrations. In the present work the efficiency of sample dilution, or color removal by the use of RP C18 columns and columns filled with florisil, to reduce color interferences prior to spectrophotometric determinations of Cr(VI) in dyed leathers were evaluated. Limits of detections were 2.5 mg kg-1 Cr(VI) when samples were diluted (1:5) and 0.5 mg kg-1 Cr(VI) after color removal by RP C18 or florisil. In all procedures applied repeatability and reproducibility of measurements were better than ± 5 %. The accuracy of the 1,5 diphenylcarbazide spectrophotometric determination of Cr(VI) was tested by analysis of the certified reference material CRM 544, Cr(VI) in lyophilized solution. By spiking leather extracts it was experimentally proven that the use of decolorizing agents did not change Cr(VI) speciation. The experimental data also indicated that in some of the leather extracts analyzed colored species caused severe positive interference effects that could not be reduced by dilution or the use of RP C18. Florisil was found to be an efficient decolorizing agent and enabled accurate and reliable determination of Cr(VI) in dyed leathers by 1,5 diphenylcarbazide spectrophotometry. En ligne : https://drive.google.com/file/d/1wEa6iB2_-GBRgPmRvj5TyguS-TjxINaQ/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=3364 [article]

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Covalent fixation of drum dyes on collagen / Gerhard Wolf in JOURNAL OF THE AMERICAN LEATHER CHEMISTS ASSOCIATION (JALCA), Vol. CII, N° 3 (03/2007)  

[article]  inJOURNAL OF THE AMERICAN LEATHER CHEMISTS ASSOCIATION (JALCA) > Vol. CII, N° 3 (03/2007) . - p. 93-98 Titre : Covalent fixation of drum dyes on collagen Type de document : texte imprimé Auteurs : Gerhard Wolf, Auteur ; Harald Kiesow, Auteur ; Laszlo Somogyi, Auteur Année de publication : 2007 Article en page(s) : p. 93-98 Note générale : Bibliogr. Langues : Américain (ame) Index. décimale : 675 Technologie du cuir et de la fourrure Résumé : Covalent fixation of performance chemicals on various substrates of natural or synthetic origin is a well-known and thoroughly investigated principle since decades. Taking a deeper look into the literature of collagen, though, there are only a few examples found to this topic. Immobilisation of process chemicals is of great importance for leather as well. Especially dyes play a crucial role, since their mobility within the substrate matrix my lead to visible staining of other materials upon contact. In order to meet these challenges in leather manufacturing a new dyeing concept has been developed: covalent fixation of drum dyes to the collagen fibre. The dyes react with collagen under mild alkaline conditions at moderately elevated temperatures, thus reaching a fixation rate of above 95%. Due to the fact that only covalently fixed dye molecules remain in leather, unprecedented fastness properties are achieved even on leather dyed to very deep shades. En ligne : https://drive.google.com/file/d/1p_vfblOOzZvNwx4dqML7Vp18KB7iCr0r/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=3365 [article]

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A theoretical study on autoxidation of unsaturated fatty acids and antioxidant activity of phenolic compounds / Wenhua Zhang in JOURNAL OF THE AMERICAN LEATHER CHEMISTS ASSOCIATION (JALCA), Vol. CII, N° 3 (03/2007)  

[article]  inJOURNAL OF THE AMERICAN LEATHER CHEMISTS ASSOCIATION (JALCA) > Vol. CII, N° 3 (03/2007) . - p. 99-105 Titre : A theoretical study on autoxidation of unsaturated fatty acids and antioxidant activity of phenolic compounds Type de document : texte imprimé Auteurs : Wenhua Zhang, Auteur ; Bi Shi, Auteur ; Jeff Shi, Auteur Année de publication : 2007 Article en page(s) : p. 99-105 Note générale : Bibliogr. Langues : Américain (ame) Résumé : The purpose of this research is to assess oxidative stability of unsaturated fatty acids and their derivatives in leather fatliquors, and to predict effective antioxidants suitable to be used for the systems. The B3LYP/6-31G(d,p) method was employed to obtain C-H and O-H bond dissociation energies of unsaturated fatty acids and phenolic compounds. Using palmitoleic, oleic, ricinoleic, erucic, linoleic, linolenic, and a-eleostearic as models, the autoxidation of unsaturated fatty acids was theoretically clarified based on free-radical chain reaction mechanism and structure-oxidative stability relationships. Calculated results showed that the allylic hydrogens of unsaturated fatty acids are easily abstracted. Unsaturated fatty acid stability is dependent on the number of double bonds and the existence of the substituent group in the carbon chain. Unsaturated fatty acids that contain more double bonds, particularly conjugated double bonds, would be easier to oxidize. Theoretical calculations suggest that the esters are more stable than the free fatty acids. The electron-donating substituent group also favors oxidative stability of unsaturated fatty acids. However, the carbon chain length doesn’t significantly affect autoxidation of unsaturated fatty acids. The antioxidative activity of phenolic compounds in unsaturated fatty acids was also studied. Calculated results showed that gallic acid, epigallocatechin, tocopherol and caffeic acid are effective antioxidants in unsaturated fatty acid systems. Epicatechin, ellagic acid and ferulic acid might be suitable to be used as antioxidants for unsaturated fatty acids containing one double bond. En ligne : https://drive.google.com/file/d/1mZJZvUcEvsIjmIklB1hQub2igT0UnsI3/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=3366 [article]

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