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Powdered Hide Model for Vegetable Tanning 
by E. Brown, R. Latona, M. Taylor and A. Gehring
Volume: 109      Number: 1     Page: 8-13     Year: 2014
To demonstrate the utility of the powdered hide model for vegetable tanning studies, interactions of quebracho with samples of powdered hide prepared from partially processed hides were investigated. Hides were dehaired by a typical sulfide or oxidative method and carried through the delime/bate step of a tanning process. Prior to tanning, the powdered hide from oxidative dehairing was on average slightly more susceptible to attack by collagenase than was the powdered hide from sulfide dehairing. After tanning with as little as 20% quebracho, powdered hide from both processes was well protected against collagenase degradation. Apparent shrinkage temperatures ranged between 79°C and 87°C, increasing with increased quebracho offer. Shrinkage temperatures for quebracho-treated oxidatively powdered hides were generally 2°C lower than for sulfide dehaired samples. This contrasts with no difference in shrinkage temperature for chrome tanned powdered hides. Comparison of micrographs of powdered hide treated with crude and purified quebracho suggest that the tanning effect of quebracho is both a function of quebracho/collagen interactions, and the filling effect of other components of the crude quebracho.
Low Carbon Products to Design Innovative Leather Processes. Part II: Determination of the Optimal Physical Modification of Tara  
by L. Olle, C. Casas, J. Diaz, S. Sorolla and A. Bacardit
Volume: 109      Number: 1     Page: 25-31     Year: 2014
This study considers the fruit of the tara bush as a sustainable source for tanning agents and proposes alternatives to chromium and other mineral salts and vegetable extracts. Specifically, physical modifications have been developed in part II of the study to obtain a modified tara with a higher percentage of tannins and with a better level of penetration (see Low carbon products to design innovative leather processes. Part I: determination of the optimal chemical modification of tara).1 The physical modification of tara focused on milling and sieving. The different products obtained have been characterized and applied to leather samples in order to evaluate the degree of penetration and stabilization in the leather structure.
Characterization of Leather Structure via Metallographic Sample Preparation 
by Huayong Zhang, Yongmei Xia, Lei Shi and Tianduo Li
Volume: 109      Number: 1     Page: 1-7     Year: 2014
In this paper, the leather cross-sectional images based on metallographic sample preparation were introduced, including those of the vertical cross section of the grain layer and reticular layer, the fine fiber cross section and the black outlines surrounding the fiber bundles sections etc. The differences between the images of fiber bundles sections obtained by the light transmission mode and by the light reflective mode were explained. With the introduction and explain of this article, the images obtained by metallographic sample preparation can be well understood.
Removal of Chromium (III) from Tannery Wastewaters with Acidophilic Fungi 
by J. Lalueza, R. Puig, A. Rius, E. Marti, J. Marti, N. Rodriguez and R. Amils
Volume: 109      Number: 1     Page: 14-24     Year: 2014
Conventional methods for chromium removal from industrial effluents may be limited by technological or economical constraints, especially when they are applied to dilute metal solutions. Thus, biotechnological processes, which are efficient at low metal concentrations and require the use of fewer chemicals, may play an important role. The chromium recovery proposed here is based on the specific uptake of this metal by acidophilic fungi. Fifty acidophilic fungal isolates from the Río Tinto basin, an extreme acidic environment, were tested. Most of them were resistant to Cr(III) and Cr(VI) solutions at concentrations up to 10 mmol/L. The influence of different experimental conditions was evaluated (medium concentration, kinetics, requirement of induction etc.). Fungal isolate 143 was able to remove 63% of Cr(III) at 0.1 mmol/L, 74% at 1 mmol/L and 21% at 10 mmol/L. These are the best Cr(III)-fungal-uptake results at acidic pH described in the literature so far. It should be possible to use these acidophilic fungi, for example in tannery wastewater, as they can resist chromium concentrations and pH values found in these effluents (between 6.5-7.5 mmol/L Cr (III) and pH as low as 3-4).
A Study on the Reliability of UNI EN ISO 17075 Method for the Determination of the Cr(VI) Content in Leather 
by A. Ballrdin and L.M. Iannone
Volume: 108      Number: 12     Page: 457-461     Year: 2013
The UNI EN ISO 17075 method for Cr(VI) detection in leather presents several drawbacks. One of these is the choice of an alkaline extraction pH, which produces severe false positive results. Summary: The hexavalent chromium content in 14 leather samples, resulted positive to the presence of Cr(VI) according to the UNI EN ISO 17075 method in two certified laboratories, was re-determined, using the official extracting method at pH 8 and a different phosphate extraction buffer at pH 4.4 containing 5% NaCl. The well-known transient nature of Cr6, that is the decrease of its amount in leather during time, required a re-activation by thermal treatment before analysis. The results show that the official method systematically gives false-positive values and that 10 of the 14 examined leather samples, when extracted with a buffer at pH 4.4, proved to have acceptable levels of Cr(VI). In addition we found that Solid Phase Extraction (SPE) cartridges, either normal or end-capped, absorb about 10% of chromate and this indicates that the calibration curves should be obtained after filtering each standard with the SPE employed.
Hydroxyapatite Nanoparticles and Polyethylene Glycol Treatment of Historical Leather: Mechanical Properties 
by A. Ershad-Langroudi and A. Mirmontahai
Volume: 108      Number: 12     Page: 449-456     Year: 2013
Historical leather objects are at risk of deterioration through mechanical stress such as viscoelastic and plastic deformation as well as natural aging erosion. So, it was expected that appropriate leather treatment should improve their mechanical properties. For this purpose, the mechanical behavior of goat historical leather treated with hydroxyapatite (HA) and polyethylene glycol 400 (PEG400) was studied and compared with the mechanical properties of untreated sample (control). The samples were subjected to a dynamic tensile stress by dynamic mechanical thermal analysis (DMTA) as well as static stress by tensile test. In addition, the treatment effects on the leather mechanical properties were investigated after accelerating aging test. It was shown that treated sample exhibited more softness, better mechanical properties and less structural changes than the untreated sample. The Scanning Electron Microscopy studies show uniform distribution of nanoparticles in the leather matrix as well as the nano hydroxyapatite particles, which are placed between collagen fibers.
New Chrome Tanning Method Assisted by Wringing and Ultrasound 
by Jinwei Zhang, Yu Wang, Bo Teng and Wuyong Chen
Volume: 108      Number: 12     Page: 445-448     Year: 2013
A new chrome tanning method was designed using wringing (10 kg/cm2) and ultrasound (28 kHz, 300W). The grain down pickled skin was put into the penetration tank to let the chrome tanning agent penetrate for 3min. After penetration, the skin was transferred into the fixation tank to basify for 3min. Then the skin was again penetrated and fixated to finish the tanning process as is described above. During the penetration and fixation stage, an ultrasound field was used and the skin was transported with belts one by one. Before each stage skins were wrung to recover the penetration solution or fixation solution and lower the water content of the leathers to about 55%. The results showed that tanning time was obviously shorted compared with a conventional method because of the mechanical extrusion formation of the micro vacuum and ultrasonic cavitationsf effect. The wet blue obtained by the new method remained the same properties compared with conventional wet blue, such as shrinkage temperature, chrome content in leather, and physical properties after retanning, fatliquoring and finishing in a normal shoe upper leather process. Furthermore, collagen structure and cross section of the leathers maintained integrity during the tanning processCproved by SEM. In short, this new chrome tanning method assisted by wringing and ultrasound could be used in future tanning industry.
Treatment of Hides with Tara-modified Protein Products  
by M. Taylor, M. Medina, J. Lee, L. Bumanlag, N. Latona, E. Brown and C.-K. Liu
Volume: 108      Number: 12     Page: 438-444     Year: 2013
In prior research, we demonstrated that gelatin could be modified with quebracho to produce products whose physicochemical properties would enable them to be used effectively as fillers in leather processing, and that leather resulting from this treatment had improved subjective properties with little effect on mechanical properties. In an extension of the study, the tannin, tara was examined for its potential in gelatin modification. The advantage for using tara is that it gives an almost colorless product, which would be desirable in production of light colored leather, as well as imparting light fastness to the leather. The conditions for optimal tara modification of gelatin were determined and the products characterized. In this present study, these tara-modified gelatins were evaluated as fillers in the treatment of wet blue and wet white. In addition, the rate of uptake of the product was also examined using an analysis developed at ERRC for the measurement of polyphenols in foods. It was found that the treated leathers, when evaluated for their subjective properties (handle, fullness, break and color), demonstrated improved properties. There were no significant differences in treated and control samples of wet blue and wet white, with respect to the mechanical properties (tensile strength, elongation, Young’s Modulus, toughness index and tear strength). SEM examination of fiber structure showed differences in treated and untreated samples. Thus, another sustainable, economical resource, the polyphenolic tara, in conjunction with gelatin, has further shown its potential for use in leather production.
Characterization and Mechanism of Zinc Salts as Tanning Agents 
by Shan Cao, Baozhen Cheng, Qiaoe Wang and Bing Liu
Volume: 108      Number: 11     Page: 428-433     Year: 2013
Zinc has important biological functions as one of the essential trace elements to human. The Zinc tanning agent could produce white leathers with properties comparable to the chrome tanning agent, and the tanning agents based on Zinc salts were prepared using different masking agents such as sodium formate, sodium acetate, sodium tartarate and potassium hydrogen phthalate. The selection of the zinc tanning agents has been optimized based on the properties like hydrothermal stability and percentage exhaustion of zinc. The results indicated that zinc sulfate can be used as tanning agent under acidic conditions (50g/L, pH=3, 25Ž) and is an effective and superior method. Moreover, Sodium citrate (0.1mol/L) was selected as masking agent compared with other masking agents. The hydrothermal stability was improved effectively with the action of masking agent.
Characterization of the Volatile Organic Compounds by HS-SPME-CG-MS in the Leather Sector 
by R. Cuadros, A. Marsal, L. Olle, A. Bacardit and J. Font
Volume: 108      Number: 11     Page: 420-427     Year: 2013
Current European legislation demands a reduction in the amount of volatile organic compounds (VOCs) used in industrial processes. The presence of these compounds in the leather industry arises from the chemicals used in the various stages of the leather manufacturing process. An important aim of tanners is to reduce or eliminate VOCs, without lowering the quality of their leather products. The HS-SPME-GC-MS method is an innovation in leather analysis. The solid phase micro extraction (SPME) is a sample preparation technique used for the extraction of volatile and semi-volatile organic compounds and is becoming widely accepted as the technique of choice for many applications and that can be connected to gas chromatography. The main advantages of this technique are speed, sensitivity, and the fact that it requires no sample handling or solvent extraction. Other advantages include the fact that the concentration and the extraction are reached simultaneously and that it enables on-site extraction of the analyte, even without the prior destruction of the sample. This paper shows the development of a new HS-SPME-GC-MS method with a deuterated internal standard for the detection and identification of volatile organic compounds emitted by leather. This method enables us to carry out a simple and rapid determination of the qualitative and semi-quantitative composition of the organic compounds in the samples.