Leather Solid Waste Research Articles

Hydrophobic, flexible electromagnetic interference shielding films derived from hydrolysate of waste leather scraps

With the rapid development of wireless telecommunication technologies, it is of fundamental and technological significance to design and engineer high-performance shielding materials against electromagnetic interference (EMI). Herein, a three-step procedure is developed to produce hydrophobic, flexible nanofiber films for EMI shielding and pressure sensing based on hydrolysate of waste leather scraps (HWLS): (i) electrospinning preparation of HWLS/polyacrylonitrile (PAN) nanofiber films, (ii) adsorption of silver nanowires (AgNWs) onto HWLS/PAN nanofiber films, and (iii) coating of HWLS/PAN/AgNWs nanofiber films with polydimethylsiloxane (PDMS). Scanning electron microscopy studies show that AgNWs are interweaved with HWLS/PAN nanofibers to form a conductive network, exhibiting an electrical conductivity of 105 S m−1 and shielding efficiency of 65 dB for a 150 μm-thick HWLS/PAN/AgNWs film. The HWLS/PAN/AgNWs/PDMS film displays an even better electromagnetic shielding efficiency of 80 dB and a water contact angle of 132.5°. Results from this study highlight the unique potential of leather solid wastes for the production of high-performance, environmentally friendly, and low-cost EMI shielding materials.

Study on the adsorption properties of multiple-generation hyperbranched collagen fibers towards isolan-series acid dyes.

In the present study, collagen fibers derived from leather solid wastes were used and modified as insoluble vectors and successfully employed as adsorbents for the removal of acid dyes. A “one-step” method was applied to synthesis effective adsorbents, which provided a sustainable way to reuse leather solid wastes via multifunctional modification. The adsorption properties of amino-terminated hyperbranched polymer (HBPN)-modified collagen fibers for the removal of different kinds of acid dyestuff from aqueous solutions were studied. The adsorption capacities of the second generation of modified collagen fibers (CF-HBPN-II) toward Isolan Black 2S-LD, Supralan Yellow, Isolan Grey K-PBL 02, Isolan Dark Blue 2S-GL 03, and Isolan Brown NHF-S were determined to be 224.87, 340.14, 287.36, 317.80, and 251.25 mg g−1, respectively. Three kinetic models, namely, pseudo-first-order, pseudo-second-order and intraparticle diffusion, were used to analyze the kinetic data. The fitting result indicated that the adsorption process of Isolan Black 2S-LD on CF-HBPN-II followed a pseudo-second-order rate model. The adsorption equilibrium of amino-terminated hyperbranched polymer-modified collagen fibers (CF-HBPN) was analyzed using the Langmuir, Freundlich and Temkin isotherm models. The Langmuir isotherm was suitable to describe the adsorption process of Isolan Black 2S-LD. RL was observed to be in the range of 0–1. The values of ΔH, ΔS and ΔG suggest that adsorption is an endothermic and spontaneous process. The adsorbed dye from the modified collagen fiber was successfully desorbed by 0.1 M NaOH. This research provides theoretical guidance for the engineering and recycling application of bio-based adsorbents.

Phase Change Composites Derived from Chromium-Containing Leather Solid Waste for Efficient Solar-Thermal Energy Storage

Phase Change Composites Derived from Chromium-Containing Leather Solid Waste for Efficient Solar-Thermal Energy Storage

Development of an Eco-friendly and Sustainable Method of Dechroming Leather Wastes

Huge quantities of chromium-containing leather solid wastes are generated during the production of chrome-tanned leather worldwide. Disposal of these huge quantities of leather solid wastes is a major challenge due to the presence of chromium, which is highly toxic (mainly in its hexavalent form) and detrimental to the environment. Sustainable and environmentally friendly methods of their disposal and treatment options for removing chromium are required so that the dechromed waste can be utilized to make useful products, such as fertilizer for soil conditioning, to improve agriculture, or other applications. In this study, therefore, a new method of dechroming leather solid wastes was designed, whose procedure and results were compared with three other commonly used methods. The focus of the various dechroming methods was on the evaluation of the degree of chromium extraction from chrome-tanned leather wastes without destroying the collagen tissues. The average total amount of extractable chromium content (Cr2O3) in the dried leather waste samples was found to be 3.67%. The new method was found to be relatively more efficient, environmentally sound and less cumbersome than all the other methods investigated in this work. At P-Value of < 0.05, concentrations of chromium extracted and %TKN in residual collagen hydrolysate reached up to 99.89% and 52.89%, respectively. The levels of total ash and total organic carbon were also relatively high in the resultant collagen hydrolysate (i.e. 12.42% and 23.27%, respectively). The t distribution test on the results of the various dechroming methods confirmed that there was a significant difference at 95% confidence interval, since t (calculated) was greater than t (tabulated). It was concluded that nearly all the chromium in chrome-tanned leather wastes can be removed with a simple technology, which is sustainable and environmentally sound.

Application of Modular Design in Upcycling Solid Leather Waste: A Sustainable Development Approach from Ethiopia

Fast changes in fashion trends have stimulated customers’ buying behavior; this has increased the demand for leather products. Fulfilling this demand requires unsustainable practices of overproduction and utilization of resources leading to increased waste generation. By far, the highest percentage of waste generated in the leather product industry is from the cutting section. Since leather scraps retain most of the chemicals added in the processing stage, disposal of this waste in landfills contributes to a higher degree of environmental pollution. This paper introduces modular design techniques for the upcycling of solid leather wastes created at the cutting stage. This contributes to creating a more sustainable approach in leather product development through the reuse of waste material, reducing required resources, and avoiding waste disposal to the environment. Primary data gathered from export-oriented leather goods manufacturing industries in Ethiopia identified a percentage of waste created at the cutting stage. Further, the physical property characterization of leather scraps was carried out to determine the appropriate modular design that can reuse the highest percentage of solid waste. The project concludes that most of the solid scraps disposed of in the leather product industry are in both areas and quality useable as raw material for the manufacturing of marketable sustainable leather products.

Eco-friendly bioenergy: New approaches for the effective treatment of tannery fleshings

The aim of this work is to produce novel bioelectricity using tannery leather fleshing (TLF), carbon nanoparticles (CNP) from vegetable waste and poly ethylene glycol (PEG). Tannery leather fleshing solution (TFS) was produced from TLF. Nanopolymeric blended solution (NPBS) was produced using TFS and reinforced using various proportions of CNP and PEG. Physico-chemical characterization has clearly revealed the chemical nature, elemental composition and thermal stability of NPBS. The microstructure and electrical conductivity of the NPBS were elucidated by scanning electron microscopy and cyclic voltameter respectively. NPBS produced with 3% CNP demonstrated high electrical conductivity (voltage: 1201.13 + 1.00 mV per cell, current: 749.42 + 0.56 mA per cell and resistance: 98.77 + 0.57 Ω per cell). The study provides an opportunity for utilization of solid leather waste generated by tanneries for production of eco-friendly bioelectricity. It also paves an economical way to make direct/alternative current and batteries.

Facile fabrication of chrome-tanned leather wastes/natural rubber composite: Mechanochemical de-crosslinking effect on collagen fibers and chrome complexation enabled in-situ compatibilization

With the growth of leather industry, plenty of leather solid wastes (LSW) have been generated annually but economic and ecological solution to utilize LSW is lacking because the crosslinked structure inhibits the reprocessing at macromolecular level to attain high performance materials. Herein, we present a facile route to realize physically de-bundling and de-crosslinking of chrome tanned collagen fibers as well as the preparation of LSW/natural rubber (NR) composite featuring remarkable tensile properties via mechanochemistry effect exerted by solid-state shear milling (S3M) equipment. It is found that original coordination between chrome and carboxylic group can be cleaved and the released chrome enables the in-situ compatibilization between LSW and natural rubber via the complexation between chrome and sulfur, which enables dual excellence in toughness and tensile strength compared with non-chromium containing composite. The improved dispersion and interfacial interaction enable the incorporation of 40 wt% LSW to afford respective NR composites with exceptional stress at 100 % strain (S100) and modulus, which are 5.07 MPa and 27.33 MPa, respectively, as well as superior tear strength and thermal stability. The S3M technology not only highlights a facile and green route to turn chrome containing LSW into high performance bio-based NR material, but also spurs the devising of innovative materials comprising leather collagen fibers.

Research on the composite and functional characteristics of leather fiber mixed with nitrile rubber

The recycling of leather solid waste not only involves resource utilization and environmental protection but also has important significance for the sustainable development of the leather industry. In this paper, the leather waste was crushed into fibers, which were stabilized and mixed with nitrile-butadiene rubber (NBR). The mixture was milled and vulcanized and a composite NBR-SLF (Stabilized Leather Fiber) is prepared for sealing material. The physical and mechanical properties, water resistance, oil resistance and aging resistance of NBR-SLF were tested and analyzed. It is found that the optimized NBR-SLF not only reduces the cost of raw material, but also changes the physical and mechanical performance of NBR. As a sealing material, it satisfies the substitution of NBR in terms of hardness and thermal stability. Especially the anti-aging ability is better than NBR.Graphical abstract

Preparation of Polypeptide Surfactants Using Chromium‐Containing Waste Leather: Effect of Hydrophilic and Lipophilic Groups

AbstractPolypeptide surfactants with different lengths of hydrophilic groups and lipophilic groups were synthesized from collagen hydrolysate polypeptides by the Schotten‐Baumann reaction. Collagen hydrolysate polypeptides were prepared through alkaline hydrolysis of chromium‐containing leather wastes, followed by changing the molecular weight of the collagen hydrolysate and the carbon chain length of the acid chloride. Fourier transform infrared spectroscopy, confirmed the successful synthesis of the polypeptide surfactants. Furthermore, surface activities of surfactants were tested to reflect the influence of the length of hydrophilic and lipophilic groups on properties, such as surface tension, foamability, foam stability, wettability, and Hydrophile–Lipophile Balance value. The results indicated that for surfactants prepared from collagen hydrolysate, a shorter hydrophilic group length resulted in lower surface tension and better foamability, foam stability, and a wetting ability which indicates the surfactants can be used as wetting agents. In contrast, the surfactant with a greater lipophilic group length had lower surface tension and poorer foamability, foam stability, and wetting ability. The presence of the C=C bond of the oleoyl lipophilic group decreased surface tension. The polypeptide surfactants prepared from collagen hydrolysate not only can effectively utilize chromium‐containing leather solid waste produced, but also avoid environmental pollution and promote the sustainable development of the leather industry.

Leather Solid Waste/Poly(vinyl alcohol)/Polyaniline Aerogel with Mechanical Robustness, Flame Retardancy, and Enhanced Electromagnetic Interference Shielding.

Renewable biobased aerogels display a promising potential to fulfill the surging demand in various industrial sectors. However, its inherent low mechanical robustness, flammability, and lack of functionality are still huge obstacles in its practical application. Herein, a novel integrated leather solid waste (LSW)/poly(vinyl alcohol) (PVA)/polyaniline (PANI) aerogel with high mechanical robustness, flame retardancy, and electromagnetic interference (EMI) shielding performance was successfully prepared. Amino carboxyl groups in LSW could be effectively exposed by solid-state shear milling (S3 M) technology to form strong hydrogen-bond interactions with the PVA molecular chains. This led to a change in the compressive strength and the temperature of the initial dimensional change to 15.6 MPa and 112.7 °C at a thickness of 2.5 cm, respectively. Moreover, LSW contains a large number of N elements, which ensures a nitrogen-based flame-retardant mechanism and increase in the limit oxygen index value of LSW/PVA aerogel to 32.0% at a thickness of 2.5 mm. Notably, by the cyclic coating method, a conductive PANI layer could be polymerized on the surface of LSW/PVA aerogel, which led to the construction of a sandwich structure with impressive EMI shielding capability. The EMI shielding effectiveness (SE) reached more than 40 dB, and the specific shielding effectiveness (SSE) reached 73.0 dB cm3 g-1. The inherent dipoles in collagen fibers and the conductive PANI synergistically produced an internal multiple reflection and absorption mechanism. The comprehensive performance of LSW/PVA/PANI aerogel not only demonstrates a new strategy to recycle LSW in a more value-added way but also sheds some more light on the development of biomass aerogels with high-performance, environmentally friendly, and cost-effective properties.

From Waste to Wealth: A Lightweight and Flexible Leather Solid Waste/Polyvinyl Alcohol/Silver Paper for Highly Efficient Electromagnetic Interference Shielding.

With the popularization of 5G communications and the internet of things, electromagnetic wave (EW) radiation pollution has aroused much concern from the public, and the search for new materials and technologies for preparing electromagnetic shielding materials still continues all around the world. However, the contradiction among high shielding performance, economic applicability, and flexibility is still not well balanced. Herein, we fabricated a novel foldable leather solid waste (LSW)/polyvinyl alcohol (PVA)/silver (Ag) paper with excellent electromagnetic interference (EMI)-shielding ability using a facile but sustainable electroless plating (ELP) method with LSW as the resource. Taking PVA as a cross-linker, debundled leather fibers (LFs) generated by solid-state shearing milling could generate a flexible LSW/PVA substrate with a high specific surface area, and eventually the deposited Ag layer served as a protective layer not only to significantly improve the mechanical and thermal robustness, but also to endow the LSW/PVA/Ag paper with good hydrophobicity, which could protect from potential moisture damage. In addition to the reflection effect of metallic Ag on EW, the hierarchical structure of collagen fibers played an important role in superior high EMI-shielding effectiveness (∼55-∼90 dB) by an absorption-dominant EMI-shielding mechanism. Furthermore, a multilayer LSW/PVA/Ag paper was also prepared with enhanced EMI-shielding effectiveness of 111.3 dB benefited by constructing multiple reflection-absorption interfaces. The high-performance, environmentally friendly, and low-cost EMI-shielding materials not only offered a new avenue toward recycling LSW in a more value-added way, but also displayed promising potential for application in flexible shielding materials or wearable clothing.

Solid leather wastes as adsorbents for cationic and anionic dye removal

ABSTRACT The removal of anionic and cationic dyes from aqueous solutions was investigated by different leather shavings, which are solid wastes generated in the leather industry. Wet-blue leather shavings (WB), vegetable-tanned leather shavings (VT), pickled hide (not tanned) shavings (PIC) and wet-white leather (pre-tanned) shavings (WW) were used. The cationic dye was Basic Red 2 and the anionic dye was Acid Brown 414. Point of zero charge, functional groups, shrinkage temperature and adsorbent surface area were characterized. The point of zero charge was 4.0, 6.0, 3.9 and 4.1 for WB, VT, PIC and WW, respectively. The specific surface area showed low values which was expected for this type of material. Tanning agent influence was verified through shrinkage temperature analysis of leather shavings. Main functional groups of the acid dye and the collagen structure of the solid wastes were determined. The tests with Basic Red 2 solutions showed only VT had a considerable removal for this cationic dye (96.7%). The tests with Acid Brown 414 were carried out with different contact times and adsorbent mass. Results showed high efficiency of WW and PIC, whose percentages of dye removal were above 96% at contact time of 30 min and above 90% using 20 mg of adsorbent. In this way, the final dye removal was 98.1% and 98.3% for contact time tests and 97.7% and 98% for adsorbent mass tests for WW and PIC, respectively. These results highlight the promising use of leather shavings as alternative adsorbents for the treatment of wastewater containing dyes.

Selection of Tanned-Leather Waste in Recovering Novel Raw Material for Manufacturing Rubber Artifacts: Towards a Zero-Waste Condition

Zero-waste is an ambitious goal to encourage sustainable production, consumption optimum recycling and resource recovery. The recycling and resource recovery of chrome-tanned leather waste is a difficult proposition because of the three-dimensional chemical network of collagen, which renders leather waste incompatible to polymer matrices. Many attempts have been undertaken to reuse leather waste, most of them require technological processes and challenging chemical pretreatments, which make the reuse an economically disadvantageous industrial operation. The paper aims to show how a very fine separation of leather solid waste leads to raw materials suitable for mixtures with natural rubber, without any chemical pretreatment. In other words, the paper intends to be a stimulus to manage leather solid waste carefully to start a cleaner and more profitable production. In particular, various industrial compounds containing different concentrations of post-tanning dyeing, or chrome shaving or oil-tanning and natural rubber were vulcanized through a standard preparation. Some compounds were also reinforced with carbon black and the vulcanization kinetics were monitored through rheometer. Experimental results indicate that there exists an optimal concentration of waste such that post-tanning dyeing post-tanning and chrome shaving are suitable for manufacture floor mats, soles and heels while oil-tanning waste can be used for making hose or conveyor belts. The mechanical performances of the articles prepared by direct mixing with leather waste are the same as those of commercially distributed rubber products.

Superior nitrogen-doped activated carbon materials for water cleaning and energy storing prepared from renewable leather wastes

The fabrication of nitrogen-doped activated carbons (N-ACs) from leather solid wastes (LSW), a huge underutilized bioresource, by different activation methods was investigated. N-AC prepared by KOH activation (named KNAC) exhibited superior physical and chemical properties with much higher BET surface area (2247 m2 g−1) and more abundant hierarchical micropores than those activated by nano-CaCO3 (CNAC) or by direct carbonization (NNAC). KOH activation decreased the total nitrogen content in KNAC, but it increased the ratio of surface nitrogen species. KOH activation also significantly promoted the conversion of nitrogen species in the carbon material to pyridinic N. Potential applications of the prepared N-ACs were evaluated, and they were tested as adsorbents to remove phenols from water and as the anodes of lithium batteries. The high surface area, abundant micropores, and plentiful surface pyridinic N guaranteed KNAC a superior nitrogen-doped activated carbon that could serve as an excellent adsorbent to remove phenols (282 mg/g) from waste water as well as an outstanding electrode material with a high and stable charge/discharge capacity (533.54 mAh g−1 after 150th cycle). The strategy of LSW conversion to versatile N-ACs turns waste into treasure and could promote the sustainable development of our society.

Sustainable Solid Waste Management in Leather and Textile Industry

Proper disposal methods and solid waste management are necessary for all the processing industries such as leather, textile and chemical industry. In this regard, the present paper reviews in detail about the leather and textile waste fibre-polymer composites and nanocomposites as a viable solid waste management strategy. In the paper, several published papers and patents available in this area are reviewed in detail. This approach adopts confinement of leather or textile waste fibres in a polymer matrix as a composite. Nanocomposites of leather waste fibre and polymer with nano-particle reinforcement have been reported to have enhanced physical and other properties. This would not only solve the problem of the disposal issue regarding leather solid wastes containing leather or textile waste fibres, but also provide versatile composite or nanocomposite materials as “Wealth from Waste Approach”. The unique feature of the present analysis and the review paper is that both leather and textile waste management have been covered in the present approach for the first time.

Properties and characterization of thyme essential oil incorporated collagen hydrolysate films extracted from hide fleshing wastes for active packaging.

In this investigation, collagen hydrolysate (CH) films extracted from hide fleshing wastes were successfully developed using solvent casting method by incorporating different concentrations of thyme essential oil (TO) (2%, 4%, 6%, and 8%) into the CH. Depending on the concentration of TO, thickness, tensile strength (TS), elongation at break (EAB), film solubility (FS), color, opacity, light transmittance, and thermal properties varied. Addition of TO resulted in the increases in the thickness, EAB (%), and light barrier performance of CH-TO films while there was a significant decrease in TS and FS of the CH films (p ≤ 0.05). According to our findings, the increment of TO content induced higher lightness and yellowness but lower redness values compared to CH film. Fourier-transform infrared spectroscopy was conducted to determine the molecular changes and interactions between CH extracted from hide fleshing wastes and TO. In order to analyze the thermal behavior of the films, differential scanning calorimetry analysis was conducted. Moreover, the structure-property relationships of CH and TO were examined by scanning electron microscopy and a reduction in the compact and homogenous structures of the films containing TO was observed. Promising results have been obtained showing that CH-based films can be used for active packaging purposes, thereby contributing to a significant reduction in the environmental impact of both leather solid waste and plastic packaging materials.

Preparation, Characterization and Application of Lubricating Protein Filler for Sustainable Leather Production

ABSTRACT In this study, collagen hydrolyzate was obtained from bovine shaving wastes of leather production with the alkali hydrolysis reaction. Total amino acid, total carbon and total nitrogen amounts of liquid collagen hydrolyzate (CH) were determined. Fourier-transform infrared spectroscopy (FTIR) characterization of collagen hydrolyzate was performed. Obtained CH was emulsified with hydrogenated castor and amino functional silicone oils to prepare lubricating protein filler (LPF). Particle size and zeta potential of the LPF were analyzed. 10%, 15%, and 20% LPF was used in the retanning/fatliquoring process of chromium tanned bovine leathers. Performance characterizations of leathers treated with LPFs were carried out with tensile strength, tear strength, filling efficiency, light fastness, shrinkage, and denaturation temperature analyses. Moreover, bounded fat content in leather was also determined. Results showed the increased thermal stability, strength performance and good filling effect in leather by application of the prepared LPF. Consequently, LPF had a good potential as natural retanning/fatliquoring agent via achieving reuse of the solid leather wastes and providing satisfactory leather properties and cleaner production by one product itself.

Characterisation of Shoe Soling Material Prepared by using Rubber and Leather Solid Waste

The ultimate aim of this research is to develop footwear soling materials from solid waste generated from leather industry. The Chrome shaving from the leather sector is used as a solid waste in this study. Styrene butadiene, Nitryl, Ethylene propylene monomer (EPDM) and Isoprene elastomers were used for this research. The rubber and chrome shavings mixes were prepared by using industrial two roll mill. Various propositions of rubbers, chrome shavings and nano fillers were characterised in this research. The developed soling materials were tested for physical testing like hardness, abrasion resistance, tensile strength, density and elongation at break and compared with compared with commercially available soling material. In this research four different experiments has been conducted among the four experiments the soling material prepared using a isoprene rubber-70 Phr and EPDM rubber - 30Phr with chrome shavings -50 Phr and KLN(Silica based) nano fillers- 7 Phr meets the required parameters of commercial soling material. Hence, it is concluded that chrome shaving wastes from tannery in soling material preparation is one of the best remedy for the environmental issues.

Leather waste management scenario in Developed and Developing nations: A Comparative

Solid waste management has been a serious issue of concern for both developing and developed nations as it stands out to be a potential threat in term of health hazards, environmental exploitation and economic burden. Hence, a properly well-designed eco-friendly solid waste management system is mandatory.Most of the developed countries had witnessed success in handling solid waste generated by households and industries by implementing closed-loop supply chain management (CLSCM) and majorly by outsourcing. But, solid waste management scenario in developing nations is entirely different and is not even in initial stage. This paper specially emphasize on leather industries solid waste management as leather industries around the world possess threat to mankind and environment. In this study, papers on leather solid waste management is selected and reviewed. Finally, a strategic comparison is made between the waste management techniques followed in developing and developed nation.

Investigation on pyrolysis and incineration of chrome-tanned solid waste from tanneries for effective treatment and disposal: an experimental study.

Chrome-tanned leather solid wastes (leather finished trimmings (LFT) and chrome shavings (CS)) from tanneries were studied using pyrolysis and incineration. Detailed characterization of CS and LFT indicated higher calorific value of 15.77MJ/kg and 19.97MJ/kg respectively, which makes it suitable for thermal treatment. Thermal Gravimetric Analysis (TGA) of CS and LFT recorded a weight loss of 79.82% and 68.22% at 800°C respectively. Energy-dispersive X-ray spectroscopy and scanning electron microscopy analysis for CS and LFT were also carried out. Pyrolysis of CS and LFT was carried out using a fixed bed-type pyrolysis unit at a temperature of 500 ± 10°C for a reaction time of 30min and three different by-products (bio-oil, biochar and pyrolytic gas) were obtained as a result of pyrolysis. From pyrolysis process, higher bio-oil yields of 52wt.% and 49wt.% from LFT and CS with calorific value of 28.0 and 27.8MJ/kg respectively were obtained. The calorific values of the biochar obtained from LFT and CS were found to be 20.5 and 23.0MJ/kg respectively. Incineration was carried out in the existing incineration facility of 150kg/h capacity at a temperature of 1200°C. The results of incineration process showed a higher weight reduction (93.0wt.%) and higher concentration of gaseous emissions, revealing the need for off-gas treatment. Further, FT-IR spectra of residual ash from the incineration process revealed the occurrence of oxidation of trivalent chromium to its hexavalent form, which could be a potential raw material in the metallurgical/chemical industry for the synthesis of sodium chromate or ferrochrome alloy. Comparative experimental investigations of pyrolysis and incineration revealed that incineration could be a potential treatment and disposal option, in developing countries like India, for chrome-tanned leather solid wastes from tanneries, forproducing heat energy and the residue with potential utilization viability in another industry paving a way towards circular economy.