A further investigation on collagen-Cr(III) interaction at molecular level / Weimo Han in JOURNAL OF THE AMERICAN LEATHER CHEMISTS ASSOCIATION (JALCA), Vol. CXI, N° 3 (03/2016)  

[article]  inJOURNAL OF THE AMERICAN LEATHER CHEMISTS ASSOCIATION (JALCA) > Vol. CXI, N° 3 (03/2016) . - p. 101-106 Titre : A further investigation on collagen-Cr(III) interaction at molecular level Type de document : texte imprimé Auteurs : Weimo Han, Auteur ; Yunhang Zeng, Auteur ; Wenhua Zhang, Auteur Année de publication : 2016 Article en page(s) : p. 101-106 Note générale : Bibliogr. Langues : Américain (ame) Catégories : Chrome trivalent Collagène Dynamique moléculaire Groupement carboxyle Réactions chimiques Tannage au chrome Thermodynamique Index. décimale : 675.2 Préparation du cuir naturel. Tannage Résumé : As we know, the reaction of chrome tanning primarily occurs at carboxyl groups of collagen, tacitly assumed at aspartic and glutamic side chains. However, the differences of the reactivity and reaction extent at these sites, as well as the effect of environmental conditions on the reaction are still unclear at molecular level. This paper presents a theoretical analysis of the reactivity of collagen carboxyl groups and Cr(III) species based on electrophilicity index (?), and the driving force for tanning reaction by using density functional theory (DFT) with Lanl2dz for chrome atom and 6-31g(d) for non-metal atoms. Glutamatic acid (Glu) and aspartatic acid (Asp) were used as the models of collagen side chains containing carboxyl group. Based on visual minteq calculation, the main Cr(III) species in chrome tanning liquor were found to be Cr(SO4)(H2O)4+, Cr(H2O)63+, Cr2(OH)2(H2O)84+, and Cr3(OH)4(H2O)105+ under the pH range of tanning process, and the content of multi-nuclear Cr(III) species increases with the rise of pH. The reactivity of collagen carboxyl groups is in the sequence of ionized Asp (Asp-) > ionized Glu (Glu-) > unionized Glu > unionized Asp, while the reactivity of the main Cr(III) species is sequenced by Cr3(OH)4(H2O)105+ > Cr2(OH)2(H2O)84+ > Cr(H2O)63+ > Cr(SO4)(H2O)4+. The data of thermodynamic driving force for tanning reaction indicate that ionized carboxyl groups have stronger tendency to form more stable carboxyl-Cr(III) complexes compared with unionized carboxyl groups, and the order of the tendency is Glu- > Asp- > Asp > Glu. Obviously, for Glu- and Asp- or Glu and Asp, the thermodynamic driving force is exactly the opposite with reactivity. Therefore, as for collagen carboxyl groups, the predominant reaction bonding site is determined by both thermodynamic and kinetic conditions. As for Cr(III) species, the order of thermodynamic driving force is Cr3(OH)4(H2O)105+ > Cr2(OH)2(H2O)84+ > Cr(H2O)63+ > Cr(SO4)(H2O)4+ which is consistent with the order of reactivity. Note de contenu : - METHODS : The main Cr(III) species under the pH range of tanning - The models of colagen carboxyl groups - The theoretical parameters - RESULTS AND DISCUSSION : The states of Cr2(SO4)3 and collagen carboxyl groups under tanning condition - The reactivity of the reactants - The driving force of typical reaction of chrome tanning En ligne : https://drive.google.com/file/d/1Mte56ufxy5sTOAeowKKeQJgcarvCPx9-/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=25745 [article]

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Investigation into the hazards of finished Cr-tanned leather as both product and waste / Liangqiong Peng in JOURNAL OF THE SOCIETY OF LEATHER TECHNOLOGISTS & CHEMISTS (JSLTC), Vol. 103, N° 1 (01-02/2019)  

[article]  inJOURNAL OF THE SOCIETY OF LEATHER TECHNOLOGISTS & CHEMISTS (JSLTC) > Vol. 103, N° 1 (01-02/2019) . - p. 43-48 Titre : Investigation into the hazards of finished Cr-tanned leather as both product and waste Type de document : texte imprimé Auteurs : Liangqiong Peng, Auteur ; Yue Li, Auteur ; Weimo Han, Auteur ; Wenjun Long, Auteur ; Wenhua Zhang, Auteur ; Bi Shi, Auteur Année de publication : 2019 Article en page(s) : p. 43-48 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Caractérisation Chrome Chrome hexavalent -- Toxicologie Cuir -- Déchets Produits de lixiviation Substances dangereuses Tests de toxicité Toxicologie Index. décimale : 675 Technologie du cuir et de la fourrure Résumé : In this study, the hazardous, substances in finished chrome-tanned leather and in leachates were determined and evaluated based on ISO or national standards, and the overall toxicity toward Photobacterium phosphoreum of the leachates was assessed. No restricted hazardous substances, such as Cr(VI), Hel-40 and carcinogenic dyes in leathers exceeded the thresholds proposed in the criteria for eco-label leather products. Chrome leathers were then leached with deionized water with a solid/liquid ratio of 1:20 to simulate rainwater leaching, and the heavy metals as well as organic compounds in leachates were analysed by ICP-OES, spectrophotometry, and GC-MS. The total chrome, Cr(VI) and TOC in the leachates of leathers were about 2.6-2.8, 0 and 237-277mg/L, repectively, and the low contents of hazardous substances in leachates showed that leather should net be considered as toxic waste when discarded. However, the biotoxicity assays of the leachates from leathers showed quite a high luminescence inhibition rate of about 97-98%, suggesting a hazard to aquatic organisms. Though the leachable chrome showed the greatest concentration in general, the toxicity of leachates seems complicated and further studies are needed. Note de contenu : - MATERIALS AND METHODS : Materials and reagents - Hazardous substances in leather - Leaching test - Toxicological assays - RESULTS AND DISCUSSION : Hazardous substances in leather - The characterisation of the leachates - The biotoxicity of leachates to photobacterium phosphoreum En ligne : https://drive.google.com/file/d/133EXsCaE5xJbzgJAphoFkiwhdmagqdMi/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=31792 [article]

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Molecular level understanding of the stability difference in collagen induced by chromium sulfate and aluminum sulfate / Weimo Han in JOURNAL OF THE SOCIETY OF LEATHER TECHNOLOGISTS & CHEMISTS (JSLTC), Vol. 101, N° 6 (11-12/2017)  

[article]  inJOURNAL OF THE SOCIETY OF LEATHER TECHNOLOGISTS & CHEMISTS (JSLTC) > Vol. 101, N° 6 (11-12/2017) . - p. 273-279 Titre : Molecular level understanding of the stability difference in collagen induced by chromium sulfate and aluminum sulfate Type de document : texte imprimé Auteurs : Weimo Han, Auteur ; Jianfei Zhou, Auteur ; Wenhua Zhang, Auteur ; Bi Shi, Auteur Année de publication : 2017 Article en page(s) : p. 273-279 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Collagène -- Stabilité Sulfate d'aluminium Sulfate de chrome 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 Technologie du cuir et de la fourrure Résumé : Though the tanning process of both chromium(III) and aluminum(III) are mainly the reactions of coordination with the collagen side chain carboxyl groups, the stability toward water and denaturing temperature of Cr(III)-tanned leather is much higher than that of Al(III)-tanned leather. In this paper, the differences between Cr(III) and AI(III) tanning mechanisms are explored from the species distribution of tanning liquors and the thermodynamics of coordination reaction. First, there are more multinuclear metal species in Cr(III) tanning liquor than in Al(III) tanning liquor through visual Minteq. For example, at pH4 Cr3(OH)4(H2O)10 5+ accounted for 39% in 0.05mol/L Cr2(SO4)3, and Al (OH)4(H2O), only 0.04% in 0.05mol/L AI2(SO4)3. In addition, a large amount of negative species Al(SO4)2(H2O)2 (always about 30% in AI2(SO4)3) appeared in Al(III) tanning liquor, which would show low coordinating effect because of the electrostatic repulsion with the ionised collagen sidechain carboxyl groups. The density functional method (DFT) was used to study the kinetics (the electrophilic indexes w) and thermodynamics (the Gibbs energy change ?rG) of tanning reaction with Lanl2dz for metal atoms and 6-31g(d) for non-metal atoms. The results showed that the reactivity of multinuclear species is higher and the complexes formed by collagen and multinucIear species are more stable for both Cr(III) and Al(III), and the differences of ?rG between corresponding Cr(Ill) and Al(lll) tanning reactions are miner. Then the main reason for the lower shrinkage temperature of Al2(SO4)3 may be the lower contents of multinuclear aluminum species and the higher content of the negative specie Al(SO4)2(H2O)2 in AI(III) tanning liquor. These results suggested that appropriate masking agents which could increase the multinuclear aluminum species content and decrease the negative species content should improve the AI(III) tanning process Note de contenu : - METHODS : The main chromium and aluminum species present under the pH range of tanning - The models of collagen sidechain carboxyl groups - The theoretical parameters - RESULTS AND DISCUSSION : The main species in Cr(III) and Al(III) tanning liquor - The reactivity of chromium and aluminium species - The driving force of typical reaction of Cr(III) and Al(III) tanning En ligne : https://drive.google.com/file/d/1T7KdyR561R35KhADfXa1mw77cSrGZhXU/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=29658 [article]

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