X射线散射方法对废液封闭循环利用工艺中皮革胶原结构的研究

在皮革加工过程中控制有害物质的过量使用,减少环境污染和健康隐患对废物管理是至关重要的。为了回收皮革加工中的废液循环再利用,减少废水和废料的排放,开发了一种封闭循环利用工艺。这种加工方法伴随的胶原的结构变化尚待研究,而这有利于理解封闭循环利用及其生产出的皮革性能。在这项研究中,用同步辐射小角X射线散射方法,分析了在封闭循环利用方法的不同阶段中胶原蛋白的结构变化。研究表明,回收废液中的有机成分和铬增加了对胶原纤维基质的填充效果。同时,由铬废液处理过的皮革对X射线的散射强度增强,这归因于废液处理皮革中更高的对铬的吸收率。此外,从角蛋白和脂类对X射线的散射强度变化佐证了废液用于脱毛过程的有效性。此项关于胶原结构的研究结果将支持制革封闭循环利用工艺是更加环境友好并有助于经济可持续发展的加工方法。

Collagen structure changes during chrome tanning in propylene carbonate

Green solvents,such as propylene carbonate(PC),can be used in leather processing to improve the efficiency of chrome tanning and reduce wastewater.Here we report a combined small-angle X-ray scattering(SAXS)and differential scanning calorimetry(DSC)study on PC and its efficacy as a carrier medium during chrome tanning.SAXS analysis on the collagen structure of chrome tanned leather using PC,compared to conventionally tanned leather using water,showed an increase in Cr uptake in addition to the more uniform penetration of Cr through the leather cross-section.The increased binding of Cr to the collagen matrix drives the decreased hydration environment of the collagen triple helix.Furthermore,DSC studies show a uniform hydrothermal stability for the PC samples due to the more even distribution of Cr through the collagen matrix.Understanding the mechanisms by which chrome tanning occurs in non-aqueous solvents can guide us towards a more sustainable future for the leather industry.

Monitoring the mode of action of synthetic and natural biocides against Aeromonas hydrophila by Raman spectroscopy and chemometrics

We have investigated the mode of action of synthetic biocides,(2-(thiocyanomethylthio)benzothiazole(TCMTB),dichlorophen,(commonly used in leather industry for preservation)and natural biocides,oregano and eucalyptus oils,on Aeromonas hydrophila using Raman spectroscopy in collaboration with multivariate analysis and 2D correlation spectroscopy to evaluate whether Raman spectra acquired contained valuable information to study the action of biocides on bacterial cells.The growth of A.hydrophila in clear and outer edge zone of inhibition differ in their reaction with different biocides,which allows us to highlight the differences as a characteristic of two kinds of bacteria.Such classification helps identify oregano oil as the most effective biocide by altering clear and outer edge zone of bacteria.Standard disk diffusion assay method was used for screening biocide bacteria interactions and later analysed by Raman spectroscopy.The paper also presents the introduction of TCMTB and oregano oil into leather processing stages to examine and determine the antimicrobial effect as an application to real-world setting.Therefore,we conclude that Raman spectroscopy with appropriate computational tools constitutes a powerful approach for screening biocides,which provide solutions to all the industries using biocides including leather industry,considering the potentially harmful effect of biocides to humans and the environment.

RAMAN AND ATR-FTIR SPECTROSCOPY TOWARDS CLASSIFICATION OF WET BLUE BOVINE LEATHER USING RATIOMETRIC AND CHEMOMETRIC ANALYSIS

There is a substantial loss of value in bovine leather every year due to a leather quality defect known as“looseness”.Data show that 7%of domestic hide production is affected to some degree,with a loss of$35m in export returns.This investigation is devoted to gaining a better understanding of tight and loose wet blue leather based on vibrational spectroscopy observations of its structural variations caused by physical and chemical changes that also affect the tensile and tear strength.Several regions from the wet blue leather were selected for analysis.Samples of wet blue bovine leather were collected and studied in the sliced form using Raman spectroscopy(using 532 nm excitation laser)and Attenuated Total Reflectance-Fourier Transform InfraRed(ATR-FTIR)spectroscopy.The purpose of this study was to use ATR-FTIR and Raman spectra to classify distal axilla(DA)and official sampling position(OSP)leather samples and then employ univariate or multivariate analysis or both.For univariate analysis,the 1448 cm^(-1)(CH_(2) deformation)band and the 1669 cm^(-1)(Amide I)band were used for evaluating the lipid-to-protein ratio from OSP and DA Raman and IR spectra as indicators of leather quality.Curve-fitting by the sums-of-Gaussians method was used to calculate the peak area ratios of 1448 and 1669 cm^(-1 )band.The ratio values obtained for DA and OSP are 0.57±0.099,0.73±0.063 for Raman and 0.40±0.06 and 0.50±0.09 for ATR-FTIR.The results provide significant insight into how these regions can be classified.Further,to identify the spectral changes in the secondary structures of collagen,the Amide I region(1600-1700 cm^(-1))was investigated and curve-fitted-area ratios were calculated.The 1648:1681 cm^(-1)(non-reducing:reducing collagen types)band area ratios were used for Raman and 1632:1650 cm^(-1)(triple helix:α-like helix collagen)for IR.The ratios show a significant difference between the two classes.To support this qualitative analysis,logistic regression was performed on the univariate data to classify the samples quantitatively into one of the two groups.Accuracy for Raman data was 90% and for ATR-FTIR data 100%.Both Raman and ATR-FTIR complemented each other very well in differentiating the two groups.As a comparison,and to reconfirm the classification,multivariate analysis was performed using Principal Component Analysis(PCA)and Linear Discriminant Analysis(LDA).The results obtained indicate good classification between the two leather groups based on protein and lipid content.Principal component score 2(PC2)distinguishes OSP and DA by symmetrically grouping samples at positive and negative extremes.The study demonstrates an excellent model for wider research on vibrational spectroscopy for early and rapid diagnosis of leather quality.