A Novel Preservation-cum-Unhairing Process for Sustainable Leather Manufacturing: An Unconventional Approach in Leather Making

Content: Preservation (or) curing is an important unit process for transportation and storage of raw hides/skins without any deterioration. Popular preservation process is mostly achieved by reducing the moisture content of hides/skins using common salt (NaCl). Usage of salt in preservation process leads to generation of large amount of contaminated salt, total dissolved solids (TDS) and consume huge amount of water for subsequent rehydration step. On the other hand, lime-sodium sulphide based reductive process is commonly employed for the removal of hair from hides/skins. This process leads to generation of lime sludge and possible evolution of toxic hydrogen sulphide gas thereby making the working atmosphere more unpleasant. Several alternative techniques for preservation as well as unhairing process have been developed individually to replace salt and sulfide, respectively. However, a single compound performing dual functions such as preservation and unhairing action in neutral pH conditions has not explored so far. In the present work, a novel formulation has been developed, which possess the both preservation and unhairing potential, and applied on the hides/skins for storage up to 6 months at ambient conditions without dehydration. Low level of sulphide was used during alkaline fiber opening for complete removal of hair. The strength and organoleptic properties are on par with salted skins/hides. The developed process completely eliminates the use of salt and 75% sulphide and also reduces the time and water required for soaking process. The developed system reduces 85% of pollution load discharged from soaking and unhairing processes. Take-Away: One pot system for salt free preservation and low sulfide dehairing for sustainable leather manufacture

Conducting Leathers for Smart Product Applications

Leather is a unique consumer material possessing a variety of properties such as strength, viscoelasticity, flexibility, and longevity. However, the use of leather for smart product applications is a challenge since it is an electrically insulating material. Here, we report a simple method to produce conducting leathers using an in situ polymerization of pyrrole. The concentrations of pyrrole, ferric chloride, and anthraquinone sulfonic acid and the number of polymerization were optimized to produce maximum conductivity in the treated leathers. The coating of polypyrrole in the treated leathers was probed using Fourier transform infrared spectroscopy, X-ray diffraction, and electron microscopic analysis. We also show that the treated leathers are black through reflectance measurements, thereby suggesting that the use of toxic and expensive dyes can be avoided for coloration process. We further demonstrate that the treated leathers, with a maximum conductivity of 7.4 S/cm, can be used for making conductive gloves for operating touch-screen devices apart from other smart product applications

A Novel Preservation-cum-Unhairing Process for Sustainable Leather Manufacturing: An Unconventional Approach in Leather Making

Content: Preservation (or) curing is an important unit process for transportation and storage of raw hides/skins without any deterioration. Popular preservation process is mostly achieved by reducing the moisture content of hides/skins using common salt (NaCl). Usage of salt in preservation process leads to generation of large amount of contaminated salt, total dissolved solids (TDS) and consume huge amount of water for subsequent rehydration step. On the other hand, lime-sodium sulphide based reductive process is commonly employed for the removal of hair from hides/skins. This process leads to generation of lime sludge and possible evolution of toxic hydrogen sulphide gas thereby making the working atmosphere more unpleasant. Several alternative techniques for preservation as well as unhairing process have been developed individually to replace salt and sulfide, respectively. However, a single compound performing dual functions such as preservation and unhairing action in neutral pH conditions has not explored so far. In the present work, a novel formulation has been developed, which possess the both preservation and unhairing potential, and applied on the hides/skins for storage up to 6 months at ambient conditions without dehydration. Low level of sulphide was used during alkaline fiber opening for complete removal of hair. The strength and organoleptic properties are on par with salted skins/hides. The developed process completely eliminates the use of salt and 75% sulphide and also reduces the time and water required for soaking process. The developed system reduces 85% of pollution load discharged from soaking and unhairing processes. Take-Away: One pot system for salt free preservation and low sulfide dehairing for sustainable leather manufacture

A Novel Preservation-cum-Unhairing Process for Sustainable Leather Manufacturing: An Unconventional Approach in Leather Making

Content: Preservation (or) curing is an important unit process for transportation and storage of raw hides/skins without any deterioration. Popular preservation process is mostly achieved by reducing the moisture content of hides/skins using common salt (NaCl). Usage of salt in preservation process leads to generation of large amount of contaminated salt, total dissolved solids (TDS) and consume huge amount of water for subsequent rehydration step. On the other hand, lime-sodium sulphide based reductive process is commonly employed for the removal of hair from hides/skins. This process leads to generation of lime sludge and possible evolution of toxic hydrogen sulphide gas thereby making the working atmosphere more unpleasant. Several alternative techniques for preservation as well as unhairing process have been developed individually to replace salt and sulfide, respectively. However, a single compound performing dual functions such as preservation and unhairing action in neutral pH conditions has not explored so far. In the present work, a novel formulation has been developed, which possess the both preservation and unhairing potential, and applied on the hides/skins for storage up to 6 months at ambient conditions without dehydration. Low level of sulphide was used during alkaline fiber opening for complete removal of hair. The strength and organoleptic properties are on par with salted skins/hides. The developed process completely eliminates the use of salt and 75% sulphide and also reduces the time and water required for soaking process. The developed system reduces 85% of pollution load discharged from soaking and unhairing processes. Take-Away: One pot system for salt free preservation and low sulfide dehairing for sustainable leather manufacture

Biointervention makes leather processing greener: an integrated cleansing and tanning system

The do-undo methods adopted in conventional leather processing generate huge amounts of pollutants. In other words, conventional methods employed in leather processing subject the skin/hide to wide variations in pH. Pre-tanning and tanning processes alone contribute more than 90% of the total pollution from leather processing. Included in this is a great deal of solid wastes such as lime and chrome sludge. In the approach described here, the hair and flesh removal as well as fiber opening have been achieved using biocatalysts at pH 8.0 for cow hides. This was followed by a pickle-free chrome tanning, which does not require a basification step. Hence, this tanning technique involves primarily three steps, namely, dehairing, fiber opening, and tanning. It has been found that the extent of hair removal, opening up of fiber bundles, and penetration and distribution of chromium are comparable to that produced by traditional methods. This has been substantiated through scanning electron microscopic, stratigraphic chrome distribution analysis, and softness measurements. Performance of the leathers is shown to be on par with conventionally processed leathers through physical and hand evaluation. Importantly, softness of the leathers is numerically proven to be comparable with that of control. The process also demonstrates reduction in chemical oxygen demand load by 80%, total solids load by 85%, and chromium load by 80% as compared to the conventional process, thereby leading toward zero discharge. The input-output audit shows that the biocatalytic three-step tanning process employs a very low amount of chemicals, thereby reducing the discharge by 90% as compared to the conventional multistep processing. Furthermore, it is also demonstrated that the process is techno-economically viable

Bifunctional Hybrid Composites from Collagen Biowastes for Heterogeneous Applications

We report the synthesis of an electrically conductive and magnetically active hybrid biocomposite comprising collagen and polyaniline (PAni) as the matrix and iron oxide nanoparticles (IONPs) as the filler through an in situ polymerization technique. Here, the matrix biopolymer, collagen, was extracted from trimmed wastes of animal hides generated from the leather industry. The as-synthesized C/PAni/IONP hybrid biocomposite powder possesses excellent electrical conductivity, thermal stability, and saturation magnetization, thereby providing scope for a wide range of applications. We show that the bifunctional composite has an ability to conduct electrons using a light emitting diode and battery setup, degrade dye under sunlight owing to its inherent photocatalytic activity, and absorb oil from oil–water mixtures with easier collection under magnetic tracking. We also demonstrate that the composite has remarkable electromagnetic interference shielding in the X-band frequency range. The results suggest that biowastes can be converted into useful high-value hybrid materials for applications in catalysis, biological, electronic, and environmental fields, thereby presenting a scalable and sustainable approach

Progress and recent trends in biotechnological methods for leather processing

Global environmental regulations are changing the leather-processing industry. Pre-tanning and tanning processes contribute 80-90% of the total pollution in the industry and generate noxious gases, such as hydrogen sulfide, as well as solid wastes, such as lime and chrome sludge. The use of enzyme-based products is currently being explored for many areas of leather making. Furthermore, enzymes are gaining increasing importance in the de-hairing process, eliminating the need for sodium sulfide. This review discusses emerging novel biotechnological methods used in leather processing. One significant achievement is the development of a bioprocess-based de-hairing and fiber-opening methodology to reduce toxic waste