April 2019 Abstracts

Evaluation of Chemical Products in Leather Post-tanning Process and Their Influence in Presence of Neutral Salts in Raw Tannery Effluent

by M. V. Moreira, E. Hansen, G. Giacomolli, F.D.P. Morisso and P. M. Aquim

In the leather industry, several chemical products are used for the transformation of the raw hide into the demanded final product. The production flow and the post-tanning of wet-blue leathers may vary according to the available technologies and the type of final item produced. Previous operations and processes are also relevant, particularly the steps of unhairing-liming and tanning process. During the effluent treatment process, there is a great difficulty in removing soluble salts, such as sodium chloride and sodium sulfate in conventional effluent treatment stations. These salts might compromise the biological treatment of tannery wastewater and adversely impact the receiving water bodies, causing environmental pollution. Further, the presence of chlorides and sulfates might interfere in the implementation of the bath reuse system or in the recycling of the treated effluents in the post-tanning process. Therefore, this work aims to investigate the measures used to control the production of sodium neutral salts, such as the sodium chlorides and sulfates, contained in the chemical compounds uses in the industry that performs post-tanning in bovine wet-blue leather, mostly for automotive and furniture upholstery. The work was carried out following the production of the factory for six months, with approximately 1485 whole wet-blue leathers being processed per day, with an average production of 7500 m² of crust leathers per day. The work methodology was based on the diagnosis of the initial situation of the tannery, chemical analyses of the supplies employed and in proposals of action based on this initial profile. The work also involves the checking of the water consumption and the evaluation of the residual baths. The identification of the chemical products in the formulation that contribute directly to the presence of neutral salts in the gross effluent and their presence in the residual baths were among the main results observed in the present work. In order to determinate sodium, chlorides and sulfates, two methodologies were tested (ion chromatography, for chlorides and sulfates; and absorption spectroscopy, for sodium), showing similar results.

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Characterization of Halotolerant Bacillus Species Isolated from Salt Samples Collected from Leather Factories in Turkey

by E. Yilmaz and M. Birbir

Salt curing is the method most commonly utilized in the leather industry to prevent microbial growth on raw hides/skins. Despite this processing, a wide diversity of microorganisms belonging to Domains Bacteria and Archaea have nevertheless been observed on salted hides/skins. In order to understand whether halotolerant bacterial species in salt contaminate hides/skins during the curing process, 30 salt samples collected from 14 leather factories in Corlu and Tuzla (Turkey) were examined for halotolerant bacteria. Total counts of halotolerant bacterial numbers, pH values and moisture contents of the salt samples were respectively determined between 104 CFU/g and 106 CFU/g, 6.23 and 7.22, 0.90 and 5.02. All isolates were able to grow on both Nutrient Agar Medium without NaCl and Nutrient Agar Medium containing NaCl at concentrations ranging from 2 to 10%. The microorganisms isolated from the samples were identified using phenotypic characteristics and comparative partial 16S rRNA gene sequence analysis. The phylogenetic analysis, using more than 1300 base comparisons of 16S rRNA sequence data, revealed 83 halotolerant isolates that share highly similar identities (97.82-100%) with their closest phylogenetic relatives. These isolates were assigned to 12 different Bacillus species (B. amyloliquefaciens, B.atrophaeus, B.halotolerans, B.licheniformis, B.mojavensis, B.paralicheniformis, B.pumilus, B.safensis, B.siamensis, B.subtilis, B.tequilensis, B.velezensis). We detected catalase and protease activities, as well as production acid from fructose, in all Bacillus isolates. Fifty-five isolates demonstrated positive oxidase activities, and 50 isolates utilized citrate as a sole carbon source. While a fairly high percentage of the isolates produced acid from maltose, almost half of the isolates produced acid from myo-inositol. While 67% of the salt samples contained 1-2 different Bacillus species, 33% of the salt samples contained 3-4 different Bacillus species. Although B.amyloliquefaciens, B.atrophaeus, B.safensis, B.siamensis species were detected at a few salt samples, B.paralicheniformis and B.halotolerans species were detected at more than half of the salt samples. These results uphold the hypothesis that proteolytic halotolerant Bacillus species in the curing salts may contaminate hides/skins during curing process. Hence, we recommend sterilized salts be used in the preservation of the hides/skins to prevent economic losses in the leather industry.

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Quantitative Analysis of FITC-trypsin Distribution in Goatskin Matrix

by Xuesong Li, Deyi Zhu, Jinzhi Song and Yanchun Li

The application of enzyme for leather making has attracted much attention in recent years. Therefore, the enzyme diffusion mechanism deserves to be investigated and it is helpful to enzyme application in leather industry. In this study, a novel method basing fluorescence detection technology was developed to achieve quantitative detection of trypsin distribution into goatskin matrix in the model of one-way and turbulent diffusion. In one-way diffusion, trypsin diffusion from the flesh side was faster than that from the grain side. As for turbulent diffusion assay, the trypsin diffusions in grain and flesh layer were directly influenced by the position of goatskin matrix such as back and belly, which could lead to different fluorescence intensity distribution. In addition, the modeling equations, which were fitted with fluorescence intensities, confirmed the quantitation feature in trypsin diffusion process. These results indicated that the method was competent for quantitative detection of enzyme spatial distribution in goatskin matrix. And it would provide the basis foundation for the development of researches in enzyme mass transfer kinetics.

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A Diverse Color-tunable Luminous Polyurethane Leather Coating Based on Long Persistent Phosphors and Photochromic Spiropyrans

by Saiqi Tian, Zhe Sun, Haojun Fan, Yi Chen and Jun Yan

A diverse color-tunable luminous polyurethane leather coating (CLPU) which can reversibly change color as well as fluorescent emission through the UV-vis or UV-darkness circle was prepared, via covalent incorporation of amino-functionalized phosphors and photochromic 1-(2-Hydroxyethyl)-3,3-Dimethylindolino-6’-nitrobenzopyrylospiran (SP). X-Ray Diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV-vis absorption spectra, reflectance spectra, fluorescent spectra as well as the migration percentage were measured to characterize the resultant samples structure and properties. In daylight, CLPU appears white before 365 UV irradiation and violet after UV irradiation, due to the transition of the spiro forms of spiropyran to merocyanine forms. In darkness, CLPU emits intense green light before UV irradiation, and the light changes to orange after UV irradiation, due to the phosphors showing pleasant diverse color-tunable luminous effect.

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