Mechanism of vegetable tannin-aldehyde combination tannage / Zhongbing Lu in JOURNAL OF THE AMERICAN LEATHER CHEMISTS ASSOCIATION (JALCA), Vol. C, N° 11 (11/2005)  

[article]  inJOURNAL OF THE AMERICAN LEATHER CHEMISTS ASSOCIATION (JALCA) > Vol. C, N° 11 (11/2005) . - p. 432-437 Titre : Mechanism of vegetable tannin-aldehyde combination tannage Type de document : texte imprimé Auteurs : Zhongbing Lu, Auteur ; Bi Shi, Auteur ; Yi Tao, Auteur ; Wenhua Zhang, Auteur ; Xuepin Liao, Auteur Année de publication : 2005 Article en page(s) : p. 432-437 Note générale : Bibliogr. Langues : Américain (ame) Index. décimale : 675.2 Préparation du cuir naturel. Tannage Résumé : Using (+)-Catechin and (+)-gallocatechin as models for condensed vegetable tannins, the reaction mechanism between the flavonoid ring structure and aldehyde was elucidated based on the density functional theory (DFT) calculation. The results show that A-ring of the flavonoid structure is the nucleophilic center, according to the atomic charges and the distribution of highest occupied molecular orbital (HOMO), which implies that A-ring is more reactive to aldehydes. As to (+)-catechin, C-6 and C-8 positions are of equal reactivity to aldehydes, according to the energy transformations in the reaction. C-8 of (+)-gallocatechin is more reactive than C-6 in the same molecule. The difference of B-rings between (+)-catechin and (+)-gallocatechin influences the distribution of HOMO in molecules and consequently leads to difference of relative reactivity between C-6 and C-8-positions in flavonoid structures, in agreement with the NMR observations. The difference of HOMO distributions of (+)-catechin and (+)-gallocatechin imply that gallocatechin-based tannins, such as mimosa tannins, have higher reactivity to aldehyde, and are more suitable for tannin-aldehyde combination tannage. En ligne : https://drive.google.com/file/d/1cHECt3xPcyyVPCDBd_-Ovu9K6dDC2bPD/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=4052 [article]

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The reaction of vegetable tannin-aldehyde-collagen - A further understanding of vegetable tannin-aldehyde combination tannage / Zhongbing Lu in JOURNAL OF THE SOCIETY OF LEATHER TECHNOLOGISTS & CHEMISTS (JSLTC), Vol. 87, N° 5 (09-10/2003)  

[article]  inJOURNAL OF THE SOCIETY OF LEATHER TECHNOLOGISTS & CHEMISTS (JSLTC) > Vol. 87, N° 5 (09-10/2003) . - p. 173-178 Titre : The reaction of vegetable tannin-aldehyde-collagen - A further understanding of vegetable tannin-aldehyde combination tannage Type de document : texte imprimé Auteurs : Zhongbing Lu, Auteur ; Xuepin Liao, Auteur ; Bi Shi, Auteur Année de publication : 2003 Article en page(s) : p. 173-178 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Calorimétrie Cuirs et peaux de moutons Mimosa et constituants Oxazolidine Poudre de peaux Stabilité hydrothermale 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 organique Tannage végétal Température de retrait Index. décimale : 675.2 Préparation du cuir naturel. Tannage Résumé : Using mimosa as a vegetable tanning agent and oxazolidine as an aldehydic tanning agent, the approaches of hydrothermal analysis, hydrogen bond and hydrophobic bond breaking as well as chemical modifications of collagen were employed to investigate the effects of hydrogen bonds, hydrophobic bonds and side amino groups of collagen on vegetable tanning, aldehyde tanning and vegetable-aldehyde combination tanning The results indicated that the aldehyde should still predominantly react with the side amino group of collagen even when added after vegetable tanning. However, the aldehyde could further react with the vegetable tannin and thus form a cross-linkage between collagen and the vegetable tannin if high-activity nucleophilic sites are present in the tannin molecules. As a result, the synergistic effect of the combination tanning on increasing the hydrothermal stability of collagen fibres was achieved and the combined stability of vegetable tannin and collagen was strengthened remarkably. This mechanism is appropriate for describing combination tanning with condensed tannins which contain nucleophilic sites. However, with hydrolysable tannins, no aldehydic cross-linkage between collagen and tannin could be observed. In general, this research revealed that vegetable-aldehyde combination tanning has features which are different from those previously assumed. According to the mechanism suggested in this paper, all the phenomena relating to vegetable tannin -aldehyde-collagen interactions can be well understood. Note de contenu : - EXPERIMENTAL METHODS : - Materials - Methods - Vegetable tanning of hide powder - Combination tanning of hide powder - Aldehyde tanning of hide powder - Hydrogen bond breaking - Hydrophobic bond breaking - Differential scanning calorimetry (DSC) studies - Amino analysis - RESULTS AND DISCUSSION - Table 1 : The influence of urea solution on hydrothermal stability of collagen (oC) - Table 2 : The influence of n-propanol solution on hydrothermal stability of collagen (oC) - Table 3 : The content of typical amino acids in the hide powders before and after chemical modifications (number of amino acid / 1000 amino acids) - Table 4 : Ts and Tp of hide powders tanned by different tannages (oC) - Table 5 : The shrinkage temperature (Ts) of the sheepskin leathers tanned by combination tannage using 20% tannin extract and 4% oxazolidine - Table 6 : The influence of sequence in combination tannage on shrinkage temperature En ligne : https://drive.google.com/file/d/1hO3CzXXRcP8Uf_g31Ja9PijSfHmCzAJ-/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=39707 [article]

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Ultrasonic removal of organic pollutants in tannery wastewater / Bi Shi in JOURNAL OF THE AMERICAN LEATHER CHEMISTS ASSOCIATION (JALCA), Vol. XCVII, N° 3 (03/2002)  

[article]  inJOURNAL OF THE AMERICAN LEATHER CHEMISTS ASSOCIATION (JALCA) > Vol. XCVII, N° 3 (03/2002) . - p. 98-101 Titre : Ultrasonic removal of organic pollutants in tannery wastewater Type de document : texte imprimé Auteurs : Bi Shi, Auteur ; Xinghai Gao, Auteur ; Zhongbing Lu, Auteur ; Youjie He, Auteur ; Guoxing Li, Auteur Année de publication : 2002 Article en page(s) : p. 98-101 Note générale : Bibliogr. Langues : Américain (ame) Index. décimale : 675 Technologie du cuir et de la fourrure Résumé : The effect of ultrasonic treatment on flocculating settling of tannery effluent, the reduction of COD in particular, was studied. The influence of the irradiation method, the duration of ultrasound and offer, and the prescription of coagulants on the efficiency of minimizing organic chemicals in wastewater were investigated. The results show that: (1) when waste water is treated only by ultrasound for 60 seconds, the removal rate of COD is 40.6%; (2) when total concentration of coagulants is increased to 100 mg/l, the greatest reduction of COD is achieved; (3) when wastewater is first treated with ultrasound for 60 seconds and then flocculated by coagulants, the reduction of COD is 10 - 37% higher than the controls without ultrasound. Thus, treatment of tannery wastewater with flocculating-settling technology can be effectively improved by ultrasound. En ligne : https://drive.google.com/file/d/13Tuy7K7WcmYAJ0GOWsnRSYeML-Vzev5G/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=4314 [article]

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