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To augment sustainable tanning, less chrome input, high functional quality leather processed via no restricted substance in processing, and ease to treat the inevitable protein waste generated are the key challenge, and currently, they have become the active part of leather research. Our work covers the synthesis of a formaldehyde-free chromium-incorporated polymeric tanning agent (FF-CIPTA) and its application in a reformed leather processing route which ensures near zero discharge of chromium containing solid waste. The preliminary characterization of FF-CIPTA reveals that the developed product is stable up to pH 5.2, and the particle size distribution ranges from 955 to 1450 nm with 12% Cr2O3 content. The present work significantly reduces the tanning agent input without compromising the thermal stability (103 °C) of the leather because of its multicrosslinking nature. Since the product exhibits a polymeric character, it provides tanning-cum-filling action which in turn reduces the retanning agent consumption in subsequent processes. Scanning electron microscopic study, porosity analysis, and hand assessment results clearly indicate the significant improvement in organoleptic properties. In addition, the process also enjoys the benefits of zero chromium containing solid waste generation, 71.4% reduction in chromium input, and high chromium transfer efficiency (92%) than the conventional process (36%), and 74.4% reduction in total dissolved solids generation. Furthermore, the water consumption and chemical input are reduced by 51.6 and 17%, respectively. Reduction in wastewater treatment cost and a high economic value of chromium-free leather scraps leads to a cumulative gain of US$ 39.84 per ton of raw material processing. Overall, a potential and practical applicability for cleaner and sustainable tanning is well established.

Sustainable management plays a vital role in the emerging world, reproducing a pollution-free environment and leading to sustainable growth. In that aspect, leather industries are cornered toward greener leather processes to reduce chemical and water usage. On the same path, deliming is one of the significant steps in the pretanning process to drive into a greener process because the conventional deliming process requires 4% ammonium salts and 100% water, which leads to an enormous amount of ammonium salts in wastewater, leading to eutrophication which adds to the pollution load. To reduce the pollution load, in this work a chemical and water-free deliming process is performed using supercritical carbon dioxide (SCCO₂) as a medium as well as deliming agent to remove the lime content from goat skin at 75 bar pressure within 10 min. Also, the utilized CO₂ is collected and reused for the subsequent set of processes. The morphological analysis shows no grain damage on delimed pelts processed using SCCO₂, and leathers post-tanned from this system exhibit better organoleptic and mechanical strength properties. The developed process opens newer vistas for sustainable development in leather manufacture.

Accumulation of hair waste is a major burden to the leather industry, causing a negative impact on the industry's sustainable development. The industry is already bogged down by the usage of synthetic re-tanning agents that are not only extremely challenging for biodegradation but also release free-form of formaldehyde in the final leather stage. This research work focuses on developing a formaldehyde-free bio-based re-tanning agent from hair waste. In order to do so, hair waste is subjected to alkali hydrolysis and subsequently graft-copolymerized with methacrylic acid (MAA). These treatments were optimal using 20 % (w/w) sodium hydroxide and thermal activity at 90 °C. This resulted in effective hydrolysis of red sheep hair, which was the ideal candidate in this study. The hydrolysate was subjected to monomer in situ polymerization (using MAA) with potassium per sulfate/sodium meta-bisulphite redox system, leading to the development of keratin hydrolysate-g-methacrylic acid (KH-g-MA) copolymer (this was noted both at a laboratory level and pilot scale). The obtained KH-g-MA copolymer exhibited ideal characteristics such as increased protein content (78.3 ± 1.2), appropriate particle size (1516 nm), suitable pH (5) and required viscosity of 512 cP. The developed KH-g-MA copolymer was then applied as a re-tanning agent in the leather manufacturing process. Significant improvement in leather's mechanical strength characteristics was observed. In addition, the organoleptic properties of leather such as fullness, softness and grain tightness showed much improvement. Scanning electron microscopy (SEM) showed an enhanced surface smoothness and filling of the voids in experimental leather in comparison to the control leather. This recycle and reuse strategy of hair waste not only helps resolve issues with handling of hair solid waste but also results in producing an eco-friendly re-tanning agent in leather manufacturing, thereby paving the way for cyclic economic utilization and cleaner environment.

This study reports on the diffusion and sorption phenomena of Cr(III) in water, propylene carbonate (PC), and a mixture of PC + water during the leather tanning process. The results presented here ...

Fatliquoring is an important step of post tanning process of leathermanufacturing where incorporation of self-emulsified oil (lubricant)makes the leather soft. There are several methods which introducepolarity into oil and provide the path where reactive species ofmodified oil can interact with water which leads to form a fatliquor.The aim of this work is to introduce an extra polarity into the fattyacid moiety through chemical modification of castor oil by carbeneintermediate. The spectroscopic characterisation such as FTIR,1H-NMR and 13C-NMR of fatliquor have been carried out. Particle size analysis of fatliquor has also been done. The experimental leathers have been tested for physical strength characterisation such as tensile and tear strength verses control and found to have better properties than control. SEM analysis for morphological study of experimental leather were also carried out which clearly indicates the uniform dispersion of fiber bundles due to the fine distribution of the novel and self-emulsifying fatliquor throughout the matrix.

With the recent events following the pandemic COVID-19, global awareness about the use of biosafety materials has been in raise. Leather industry being a major commodity-driven sector, its role in addressing the issues concerning the safe use of leather products has become inevitable for the sustainability of the industry. A significant number of researches have been conducted to fabricate bio-safe leather by incorporating different types of antimicrobial agents during leather manufacturing. Besides, the increasing diversity in the development of synthetic materials and the impact of COVID-19 outbreak on automotive industry may create more demand from customers for incorporating different functionalities in leather without losing its inherent properties. Some of the key functionalities discussed include resistance to microbial growth, self-cleaning through superhydrophobicity and photocatalysis, thermal regulation, flame retardance and scented leather. This review focusses on the fabrication of such advanced functional leather materials over the past decade with special emphasis on antimicrobial leather. Some of the key factors elaborated in the review include the state of art approaches for the preparation of functional materials, mode of incorporation of the same into the leather matrix, the mechanism behind with a perspective on the challenges involved in fabrication for real-world applications. A major outcome of this review is that even though several kinds of cutting edge researches are happening in the field of leather manufacturing, most of them were not validated for its practical applicability and sustainability of the proposed solution. This could be majorly attributed to the cost involved in fabrication of such materials, which forms a crucial factor when it comes to a mass production industry such as leather. Also, the researchers should concentrate on the toxicity of the fabricated materials which can impede the process of adopting such emerging and need of the hour technologies in the near future. Knowledge obtained from this review on fabrication of bio-safety leather against bacteria, mold and fungi would help further to integrate the antiviral property into the same which is a global need. Also, fabrication of functionalized leather would open new avenues for leather manufactures to venture into the development of advanced leather products such as flexible electronics, radiation shielding and fire fighting garments etc.

Intensifying researches in leather sector are focusing on eco-benign tanning chemicals with less environmental impact processing route. The present study aims to design an eco-acceptable shoe upper leather process that could potentially eliminate use of chrome from the leather industry. Possible conversion of Cr3+ to Cr6+ in suitable oxidant environment during leather manufacture is always a threat to the ecosystem. Water load for leather processing is very high, also becoming a precious resource that needs to be reduced for industrial applications. Further without water usage for a process, generation of wastewater could be averted. With this context, a combination tanning using wattle and aluminium has been developed in a pickle-less and waterless medium. The experimental leather possesses a shrinkage temperature of 84 °C with a fully loaded compact fibre structure indicating that tannin penetration is not affected in waterless medium. Experimental leathers exhibit better physical strength and comparable organoleptic characteristics. The process enjoys environmental benefits as it shows significant pollution load reduction in Biological Oxygen Demand (BOD), chemical oxygen demand (COD), Total Dissolved Solids (TDS) by 88, 89, and 97%, respectively. Hence, a viable option is made available to manufacture eco-acceptable leather without water usage and chrome salts in tanning.

For the first time, GSK's solvent selection guide (SSG) has been explored for leather making from the view of sustainable manufacturing. A novel “Solvent Selection Tool” has been developed to identify sustainable non-aqueous media for leather making from the solvents listed in GSK's SSG. The developed solvent selection tool has been structured into four segments and each one has a particular screening criterion. Preliminary screening-I, based on the cumulative score of GSK's SSG, enabled the shortlisting of 41 solvents from 110. Screening-II, based on toxicity (LD50 value >5000 mg kg−1 of rat), has filtered the number of solvents down to 16 from 41. The effect of the selected 16 solvents on the hydrothermal stability of the skin matrix (screening-III) shows that 9 solvents, namely propylene carbonate, 1,2-propane diol, 2-butanol, ethyl lactate, tetraethylene glycol, ethyl acetate, ethanol and dimethyl carbonate, have no negative impact, whereas the other 7, namely glycerol, DMGMBE, diethylene glycol, propyl acetate, 1,3-propane diol, 1,4-butane diol and 2-propanol, have a negative impact on thermal stability. Propylene carbonate, dimethyl carbonate, ethanol and 2-butanol show superior tanning performance (screening-IV) in terms of mass transfer efficiency (>99% w/w), hydrothermal resistance (104 °C) and leather quality compared to the other selected solvents. The internal comparison results show that propylene carbonate is an ideal medium for a sustainable tanning process. The propylene carbonate based tanning process enjoys zero discharge of water/chromium(III), avoids the usage of fungicides in the tanning process and is ecologically acceptable.

Leather industry is forced to adopt green manufacturing options due to consumer awareness and statutory environmental stipulation norms. Conventional leather manufacture involves various physico-chemical treatment processes, leading to the generation of wastewater with high pollution load. Several alternative leather chemicals and in-process control measures have been developed to overcome the environmental issues. Till date, no such significant measures have been found out. Sustainable leather manufacture necessitates complete redefinition of the conventional leather making processes. Replacement of water with alternative sustainable carrier medium could be one of the possible redefined approaches. In this perspective, an attempt has been made to summarize the current status of different alternative carrier medium and its pros and cons with respect to leather manufacture. Solvent selection tool, usage of supercritical fluid and switchable solvents in different unit processes of leather manufacture are the green chemistry approaches to be employed in order to overcome the drawbacks associated with alternative carrier medium based leather manufacture. This review focuses on such possible green chemistry approaches, challenges and critical factors for usage of alternate sustainable carrier medium in leather industry.

One of the long lasting problems associated with leather industry is to meet environmental standards for both liquid and solid wastes. Statistics show that one tonne of wet-salted hides/skins yields around 650 kg of solid waste. Among various wastes generated, trimmings for the most part have been underutilized. Collagen presents in trimmings waste are effectively used but hair goes unutilized or at the most as feed for boilers during gelatin manufacturing. Hence, newer technology is needed for complete and effective utilization of raw trimmings. In leather manufacture, formaldehyde condensates polymers are used as re-tanning agent to enhance the compaction of leather. However, these products are hard for biodegradation and also cause the release of free formaldehyde in leather, which is a known carcinogen. Here, there is a need for development of formaldehyde free re-tanning agent for eco-benign leather processing. In this work an attempt had been made to develop formaldehyde free biodegradable eco-benign re-tanning agent from raw trimming of tannery solid waste as a circular economy model. Alkaline (7.5%w/w NaOH) – hydrogen peroxide (10%w/w) pre-treatment followed by thermal hydrolysis at 100 °C for 5 h was an optimized method for effective hydrolysis of trimmings and the process of preparation of product results in the holistic utilization of raw trimmings. The developed product was characterized using Dynamic light scattering and FTIR techniques. The product prepared was further used in leather manufacture as a re-tanning agent and was found to impart multifunctional properties to leathers such as fullness, grain tightness and shade of dye brilliance. Product improves the mechanical strength characteristics of leather and also the exhaustion of post-tanning chemicals. SEM analysis shows that the experimental leather is more compact and flat than control. This novel strategy had not only solved the issue of solid waste but also resulted in a greener leather auxiliary leading to greener environment.

Fibroblast growth factor-23 (FGF23) is a bone-derived hormone regulating vitamin D hormone production and renal handling of minerals by signaling through an FGF receptor/αKlotho (Klotho) receptor complex. Whether Klotho has FGF23-independent effects on mineral homeostasis is a controversial issue. Here, we aimed to shed more light on this controversy by comparing male and female triple knockout mice with simultaneous deficiency in Fgf23 and Klotho and a nonfunctioning vitamin D receptor (VDR) (Fgf23/Klotho/VDR) with double (Fgf23/VDR, Klotho/VDR, and Fgf23/Klotho) and single Fgf23, Klotho, and VDR mutants. As expected, 4-week-old Fgf23, Klotho, and Fgf23/Klotho knockout mice were hypercalcemic and hyperphosphatemic, whereas VDR, Fgf23/VDR, and Klotho/VDR mice on rescue diet were normocalcemic and normophosphatemic. Serum levels of calcium, phosphate, and sodium did not differ between 4-week-old triple Fgf23/Klotho/VDR and double Fgf23/VDR or Klotho/VDR knockout mice. Notably, 3-month-old Fgf23/Klotho/VDR triple knockout mice were indistinguishable from double Fgf23/VDR and Klotho/VDR compound mutants in terms of serum calcium, serum phosphate, serum sodium, and serum PTH, as well as urinary calcium and sodium excretion. Protein expression analysis revealed increased membrane abundance of sodium-phosphate co-transporter 2a (NaPi-2a), and decreased expression of sodium-chloride co-transporter (NCC) and transient receptor potential cation channel subfamily V member 5 (TRPV5) in Fgf23/Klotho/VDR, Fgf23/VDR, and Klotho/VDR mice, relative to wild-type and VDR mice, but no differences between triple and double knockouts. Further, ex vivo treatment of live kidney slices isolated from wild-type and Klotho/VDR mice with soluble Klotho did not induce changes in intracellular phosphate, calcium or sodium accumulation assessed by two-photon microscopy. In conclusion, our data suggest that the main physiological function of Klotho for mineral homeostasis in vivo is its role as co-receptor mediating Fgf23 action. © 2017 American Society for Bone and Mineral Research.

Leather processing involves various unit processes in which deliming is an essential unit process carried out conventionally using ammonium salts. This results in the generation of a huge amount of ammoniacal nitrogen and a considerable amount of total dissolved solids in tannery wastewater. In the current work, an effort has been made to design a deliming process using dry ice (solid carbon dioxide). It was observed that 2% (w/w) dry ice is adequate for the complete deliming of limed pelts of goat skins in 45 min; whereas the conventional process using 2% ammonium chloride requires 60 min. Morphological analysis using scanning electron microscopy shows no surface deposition or grain damage on delimed pelts processed using dry ice. Experimental leathers exhibit organoleptic and mechanical strength properties comparable to that of control leathers. The alternative method developed using dry ice reduces the generation of ammoniacal nitrogen, total dissolved solids, total Kjeldahl nitrogen and chloride from the deliming process by 98, 88, 95 and 94% respectively compared to the control process. This method also helps in reduction of chemical oxygen demand and biochemical oxygen demand in wastewater. Moreover, the methodology of using dry ice for deliming is very simple for practical applications. The option of using dry ice for deliming would be effective for cleaner leather manufacture.

The fundamental knowledge of the porous nature of crosslinked collagen matrix such as tanned leather is an aid to design appropriate chemicals for leather making. It would also help to target a particular area of matrix to improve its uniformity and other functional properties. The purpose of this study is to analyze the variations in pore sizes of chromium crosslinked collagen matrix, chrome tanned leather, from different animal species and different areas of the same species. In this study, chrome tanned leather from goat and sheep were investigated for surface area, pore size, and distribution. Thermoporometry results show that average pore radius of goat leather is around 2–30 nm and that of sheep is 2–20 nm. Nitrogen adsorption result shows that average surface area of goat (8.24 m2/g) leather is higher than sheep (6.73 m2/g), but the average pore diameter of goat (289 nm) is smaller than sheep (385 nm) leather. It has been found that more numbers of smaller pores are present in goat than sheep leather and all the leather samples including goat and sheep obeyed type-III adsorption isotherm. Capillary flow porometry analysis gives the smallest, largest, and mean-flow-diameter of through-pores. The average size of largest throat pore diameter of sheep (1313 nm) is smaller than that of goat (1385 nm) leather. In general, the pore volume distribution of sheep leather is higher than that of goat leather. Morphological analysis using scanning electron microscopy shows that pore mouth of goat is deeper than that of sheep. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40835.

―Green‖ odors comprise a group of eight structurally related aliphatic alkenals and alkenols which are characteristic for the odor of a wide variety of plant materials. Using an automated olfactometer, the olfactory detection thresholds for ―green‖ odors were determined in six CD-1 mice and compared with that of spider monkeys and human subjects. Detection threshold values for alcoholic ‖green‖ odors (cis-3-hexen-1-ol, trans-3-hexen-1-ol, trans-2-hexen-1-ol and 1-hexanol) ranged from 8.1 x 109 to 8.1 x 1011 molecules/cm3 and for aldehydic ‖green‖ odors (cis-3-hexenal, trans-3-hexenal, trans-2-hexenal and n-hexanal) , from 8.1 x 107 to 8.1 x 1011 molecules/ cm3 . Detection threshold values of ―green‖ odor with double bond ranged from 8.1 x 107 to 8.1 x 1011 molecules/cm3 and for ―green‖ odor without double bond ranged from 8.1 x 108 to 8.1 x 1011 molecules/cm3. Detection threshold value of cis- configured ―green‖ odors ranged from 8.1 x 108 to 8.1 x 1011 molecules/ cm3 and for trans- configured ―green‖ odors threshold value ranged from 8.1 x 107 to 8.1 x 1011 molecules/ cm3. Trans-2-hexenal with a double bond at C-2 position in its molecular structure yielded the lowest detection threshold value when compared the other ―green‖ odors (8.1 x 107 to 8.1 x 109 molecules /cm3) which shows not only the presence of double bond plays a major role in detection but the position of the double bond present. A comparison between the present data and data from the other species showed that CD-1 mice displayed lower detection thresholds for all ‖green‖ odors than human subjects and spider monkeys except for the cis-3-hexen-1-ol odor. These findings suggest that the differences in the threshold values between ―green‖ odors are due to the difference in the molecular structure like the presence of double bond and the position of double bond.