Leather Tanning Research Articles

Sustainable leather tanning: Enhanced properties and pollution reduction through crude protease enzyme treatment

In this study, proteolytic bacteria, particularly Pseudomonas aeruginosa strain SM4 (OQ349573), were isolated from tannery solid waste dumping yard soil and employed to produce extracellular protease enzymes. The bacteria exhibited optimal growth after 30 h of incubation at 37 °C and pH 7. Under conditions of 55 °C, pH 8, and a substrate concentration of 2 %, the crude enzyme displayed its highest activity at 105 UmL−1. Notably, the produced crude enzyme showed no discernible inhibitory effects on detergents, metal salts, or organic solvents. Application of the crude protease at concentrations of 3 % and 2 % in chrome tanning of goatskins (GS) and cowhides (CH), respectively, yielded significant reductions of 35 % and 30 % in chromium and other post-tanning chemicals compared to conventional processes. Despite the 30 to 35 % reduction in tanning and post-tanning chemicals, the uptake of chrome and associated chemicals by crust leather was higher than observed in conventional processes. Chromium content analysis of the effluent revealed an 81 % reduction during piloting in real industrial operations, accompanied by reductions of about 46 % in BOD and COD pollution loads. The finished leather obtained from the enzymatic process exhibited superior mechanical properties, including higher tensile strengths (210 and 195 kg cm-2), stitch tear (92 and 165 kg cm−1), grain crack load (28 and 32 kg), and distension (73 and 62 mm) for GS and CH, respectively, surpassing or closely aligning with standard values and those obtained in conventional processes.

Development of polyester-based structural composites using recycled plastic core, tanned leather, and GFRP additives for safe and sustainable environmental production

Development of polyester-based structural composites using recycled plastic core, tanned leather, and GFRP additives for safe and sustainable environmental production

Insights into the Development of Dyeing-Assisting Amphoteric Acrylic Retanning/Fatliquoring Agents for Ecological Chrome-Free Tanned Leather Production

Insights into the Development of Dyeing-Assisting Amphoteric Acrylic Retanning/Fatliquoring Agents for Ecological Chrome-Free Tanned Leather Production

Effect of Gamma Irradiation on the Stability of Tanned Leather

Leather tanning involves several processes of converting putrescible hide to stable leather resistant to harsh environmental conditions. Severe conditions such as high temperatures and UV radiation, when exposed to the leather materials, cause degradation and decrease physical, chemical, and structural properties. The effect of gamma irradiation on viscoelastic properties and stability of tanned leather against thermal and photodegradation was studied using the Dynamic Mechanical Analysis (DMA) technique. The thermal stability of chrome and mimosa-tanned leather was inferred from the peak of storage modulus graphs. Gamma irradiation of samples with low doses increased the storage modulus of chrome and mimosa-tanned leathers. Doses up to 20 kGy decreased the stability of thermally aged chrome-tanned leather. However, for mimosa-tanned, there was an increase at higher doses as a result of gamma irradiation inducing additional bonds that enhance the stability of the tanned leather. Nevertheless, there is a variation in the stability of chrome-tanned leather at different doses of irradiation.

Manufacturing of isocyanate-based oligomeric dyes with high coloring capabilities: synthesis and application in the dyeing of organic chrome-free leather

Leather dyeing is a critical step in leather manufacturing, as it is responsible for providing leather products with an eye-catching visual aspect and adequate quality properties to meet customers' expectations. This step is becoming more and more challenging as the leather industry advances hand in hand with new environmentally friendly policies and regulations to achieve a safer and healthier planet by replacing the highly polluting Cr-based leather tanning technology with greener alternatives. As a result, achieving high-performance dyeing of organic chrome-free leather is one of the bottlenecks for the sustainable development of the leather industry. Herein, we propose a novel strategy to fabricate an isocyanate-based oligomeric dye (IBD) with high coloring capabilities (component content higher than 62.8%) based on toluene 2,4-diisocyanate and reactive red dye 180. This material has been tested for the dyeing of biomass-derived aldehyde (BDA)-tanned leather with excellent outcomes. The experimental results showed that the crust leather dyed with our novel IBD dyeing agent had higher color fastness and better fullness than the leather dyed with conventional anionic (CAD) or reactive red 180 (RRD-180) dyes. These excellent and promising results open new avenues in manufacturing high-performance organic Cr-free leather products and help to ensure the sustainable transition of the leather industry from Cr-based leather tanning to more sustainable alternatives, maintaining the final quality of the leather products.Graphical abstract

Child Labour in Saurashtra Region of Gujarat State

Child labour is one of the most pressing social problems which the international community has been facing. Children are an important asset not only for their country but for the whole of mankind. They are not merely future adults. They are tiny apostles of peace and above all very much human beings though weak and immature. In almost all societies, children work in some way, though the types of work they do and the forms of their involvement vary. But many millions of children work under abusive and exploitative conditions that are clearly dangerous to them. There are still a large number of children who are employed in rag picking, collection of raw hides and skins, leather flaying and tanning, accompanying their parents for deep sea fishing, fish processing and storage, collection of minor forest produce, etc., that have not been brought within the ambit of the prohibited category.

Bicarbonate Alternatives in the Neutralization Phase of Leather Tanning to Ensure Sustainability

The post-tanning procedure involves neutralizing the iso-electric point, which ensures that there is no imbalance between carboxylic groups and amino groups. This balance allows for the penetration of dyes, fatliquoring agents, and other chemical materials. Bicarbonate is used during the neutralization phase, and to eliminate it, 4 metric tons of water are needed for each metric ton of leather. Additionally, this leads to an elevation in both Biological Oxygen Demand (BOD) and Chemical Oxygen Demand (COD). The objective of the research was to substitute bicarbonate with sodium borate, sodium acetate, and sodium formate, and neutralise syntan to decrease the quantities of pollutants generated from this process, minimize the consumption of water, and improve the quality of the produced leather. Each experimental group's BOD, COD, microscopic micrographs, physical, chemical, and organoleptic parameters were determined. The use of sodium borate, neutralizing syntan, sodium acetate, and sodium formate resulted in a significant decrease in the discharge of BOD, COD, and water consumption. Furthermore, the use of 2.5% sodium borate has proven to be the most effective neutralizing agent in reducing water consumption by 80%, total oxygen demand by 39% and costs of neutralization chemicals by 0.62%. Also, the physical and chemical properties of the leather product were similar to those of the control. Therefore, the leather that has been neutralized with sodium borate is considered to have the best organoleptic characteristics compared to the control.

Identification and application of Cr(VI) based on 2-amino-5-substituted-1,3,4-thiadiazole molecular probes

With the modernization of industry, increasingly serious water pollution has become a global environmental pollution problem. Cr (Ⅵ) is the most common water pollutant and is applied to aluminum plating, paint production leather tanning, etc. Cr (Ⅵ) is a kind of aspiration and swallowed poison, that can enter the body through the digestive tract, respiratory, and skin mucous membrane, and may occur after skin contact dermatitis, or allergic phenomena, such as redness, itching, tingling, etc. In view of the harm of Cr (Ⅵ) to the human body, it is an urgent problem to develop a probe that can simultaneously detect two kinds of Cr (Ⅵ) in the environment. Herein, a novel green synthetic 2-amino-5-substituent-1,3, 4-thiadiazole was synthesized. The synthesized 2-amino-5-methyl-1,3, 4-thiadiazole (Probe M) was used as a molecular probe to selectively recognize Cr2O72− and CrO42−, and then the anti-interference detection and quantitative test of Cr2O72− and CrO42− were carried out. The binding ratios of Probe M with Cr2O72− and CrO42− were 1:1 and 2:1, respectively. The complexation constants were 5.8617 × 105 M−1 and 9.328 × 105 M−1, respectively, and the detection limits were 1.3334 × 10−7 M and 1.3046 × 10−7M, respectively. In this paper, 2-amino-5-substituted-1,3,4-thiadiazole was used as a probe to detect Cr (VI) for the first time, also carried on the dipstick experiment observed with the increase of concentration, the color of the paper changed from colorless to yellow, can be used in the “naked eye” identification, the method can be more convenient and quick detection of Cr (VI) solution.

Development of masked silica tanning system for sustainable leather production.

Amid mounting pressure on the long-term recyclability of chromium in tanned leather and the associated environmental hazards, the quest for an alternative, cleaner tanning system has gained tremendous momentum. In this context, our study explores the remarkable potential of silicates as a versatile platform for skin/hide tanning, circumventing the inherent risks and ecological threats posed by chromium exposure and leaching. We present an alternative approach of using a silica-based tanning system, employing a Taguchi model, to optimize a masked silica (MaSil) tanning product/process for achieving effective collagen stabilization. Our results demonstrate the significant advancements made in hydrothermal denaturation temperature, reaching an impressive 79 °C through precise Taguchi parameters-5% SiO2, masked with 0.3 mole of citrate salt, and a tanning process fixation pH of 4.5. Notably, the mechanical strength analysis reveals compliance with the stringent upper leather recommendation standards, validating the practicality and quality of MaSil crust leather. Moreover, our research highlights the unprecedented environmental benefits of the first reported application of Taguchi's approach to the MaSil tanning system. The developed tanning system remarkably reduces total dissolved solids (TDS), biological oxygen demand (BOD), chemical oxygen demand (COD), and overall water load by 68.4%, 25.4%, 59.5%, and 33.7%, respectively, heralding a promising era of water and environmental sustainability in the leather sector. This study holds the potential to transform leather production, wherein the envisioned future on the use of the Taguchi model and optimized MaSil tanning system could find a place in shaping a cleaner, greener, and more sustainable leather industry.

Monitoring and Recovery of Chromium (III) from Inorganic Waste Industrial Solution

Using Solvent Extraction Calixe arene diluted in toluene at pH 6.5 extracts Chromium (III) from aqueous medium well. The equilibrium time has been calculated to be between 20 and 25 minutes. The degree of extraction increases with increasing Chromium (III) concentration in the aqueous phase, whereas the extraction ratio decreases with increasing Chromium (III) concentration. The extraction rate increases as the pH and concentration of Calixe arene rise. The results of batch equilibrium tests showed that the Langmuir isotherm accurately reflects the adsorption process; the impact of numerous analytical parameters such as pH, equilibrium time, temperature, stripping agent, and diluents was rigorously investigated. The findings showed that 99.5%. The recovered solvent could be utilized in subsequent extractions. The results of batch equilibrium tests showed that the Langmuir isotherm accurately reflects the adsorption process; the impact of numerous analytical parameters such as pH, equilibrium time, temperature, stripping agent, and diluents was rigorously investigated. The findings showed that 99.5%. The regenerated solvent might be reused in further chromium (III) extractions. Finally, the process was used to extract Cr (III) from waste solutions from electroplating and leather tanning.

THE ROLE OF SOLAR AND ALTERNATIVE ENERGY IN DIRECTING OF THE BIOECOLOGICAL CHARACTERISTICS, CONSERVATION AND USE OF ESSENTIAL OIL PLANTS

The main purpose of the research is to study the role of solar and alternativ energu in the direction of bioecelogical characteristics, protection and usage of essential oil plants. The huge food and technical importance of oil and essential plants are given in the article. The vegetable oils obtained from them are used in the food industry, in baking, in the preparation of various preserves, confectionery, margarines and oils, and from essential oils in the field of medicine, in the perfumery and cosmetics industry, etc. widely used. At the same time, it is used in the production of linoleum and stearic acids, lacquer-paint, weaving, soap-making, leather tanning, etc. these oils are used in industries. Oil crops include sunflower, soybean, sesame, groundnut (araxis), safflower, castor, poppy, white mustard, blue mustard, winter and spring rape, oilseed rape, lallemantia, perilla (sudza), oil tulip, radish, flax, etc. includes plant species. Among the vegetable oils produced for edible oil on a global scale, the first place is soybean, the second place is sunflower, and then peanut, cotton, rapeseed, olive, sesame, corn and safflower oils. Most essential oils are found in free form in plants. Their amount in different types of plants varies greatly, from 0.001% to 22%. There may be a type of plant in which the amount and composition of the essential oil is negligible. This may mainly depend on the cultivated region, the age of the plant, the phase of development and other conditions. It has been determined that plants accumulate more essential oil in dry and hot weather than in cold and humid conditions. The amount of essential oil in the plant is greater during the flowering and ripening period. A group of plants cultivated to produce essential oil are called essential oil plants. They contain volatile aromatic substances with different chemical composition. The amount of these oils in the seeds, flowers, leaves, branches and other organs of the plant varies depending on cultivation technology and soil-climate conditions. Essential oil plants include coriander, mint, cumin, basil, cloves, myrtle, etc. belong to plants. Essential oils are widely used in the food, medicine and perfume-cosmetics industry. The waste obtained after the processing of fruits and seeds is used as feed in livestock and poultry farming. Solar energy from alternative energy sources is used in many countries of the world. In the process, solar energy is converted into useful energy and replaced by other forms of energy, such as biomass, wind or hydropower, and "drives" the weather on Earth. Most of the solar radiation is absorbed by the oceans and seas, as a result of which their water heats up, evaporates and falls to the Earth in the form of rain, "feeding" hydroelectric power plants. Solar energy affects to the plants mainle the essentional oil plants, either. Most plants admit solar energy during the drying or feeding process. Thus, we considered both the essential oil plants, especially the flax plant, and learned the advantages and disadvantages of alternative energy. We came to the conclusion that alternative energy has a role in the process of cultivation and protection of essential oil plants. Approaches and results can be different in the analysis of positive and negative sides in the fast developing era. Keywords: essential oil, plants, solar energy, ecology, industry, flax, linseed

Eco-friendly Chrome Tanning of Leather using Ultrasound Technique

This article describes the development of an environmentally friendly chrome tanning process of leather using ultrasound. Most of the leathers are tanned by the conventional method using basic chromium sulfate. It is one of the most polluting and time-consuming steps in leather processing. Investigations were carried out on ultrasound assisted eco-friendly tanning process so that the chrome tanning agent could provide better quality leather. Effects of using ultrasound in chrome tanning process were studied at different pH, tanning time, tanning agent dosage, and then compared with that of conventional method. Tanned leathers were characterized by scanning electron microscopy (SEM), photomicrographic analysis, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and energy dispersive X-ray (EDX). SEM analyses of the surface and cross-section of the tanned leather showed that fiber structures were not affected by ultrasound. It was also found that the shrinkage temperature of leather tanned with ultrasound was increased by about 5-29 °C. Chrome uptake and content were found to increase by 30-50% and 1-7%, respectively. Tanning time was shortened from 6 hours to 2 hours and the quantity of leachable chromium in ultrasound assisted chrome tanned leather was also decreased significantly. The noteworthy enhancing effects have been attributed largely because of the increased penetration of tanning agents into pickled leather. Photomicrographic analysis of the cross-section of the tanned leather also showed a higher penetration of tanning agents in presence of ultrasound.

New materials-based on gelatin coordinated with zirconium or aluminum for ecological retanning

Ecological retanning agent is an effective way to solve the pollution source of leather manufacturing industry. In this study, the gelatin from chrome-containing leather shavings in the leather industry was used to realize sustainable leather post-tanning. The gelatin hydrolysate (GH) coordinated with Zr4+ or Al3+ to prepare eco-friendly retanning agents GH-Zr and GH-Al. The successful coordination between GH and metal ions was characterized by FTIR and XPS. The retanning agents were characterized by FTIR curve-fitting and circular dichroism spectroscopy. The results showed that the conformation of the secondary structure of the polypeptide became ordered and stable after coordinating with the metal ions. The particle size and weight average molecular weight of the retanning agents were ~1700 nm and ~2100, respectively, measured by nanoparticle size analyzer and gel permeation chromatography (GPC). The retanning agents were applied to retanning of chrome tanned leather and glutaraldehyde tanned leather. The abundant free amino from retanning agents can consume the free formaldehyde. Meanwhile, retanning agents can effectively improve the multiple binding sites, resulting in favorable thickening rate (>110 %) and excellent dye and fatliquor absorption rate with ~99.91 % and ~93.18 %. Thus, this strategy can provide a viable choice for solid leather waste and sustainable development of the leather industry.

The effect of Aspergillus sp. as a bating agent in tanned goat’s skin on bending strength, paint fade, and protein level

Bating is a process of eroding proteins carried out in the process of tanning the skin to erode protein on the skin using protease activity. Feliderm is commonly used as a bating agent. However, the disadvantages of feliderm are relatively high cost, access to purchases is quite difficult, and not being environmentally friendly. Aspergillus sp. is widely known by the public for its use in fermenting soybeans to soy sauce, which is one of the producers of protease enzymes that can be utilized. The method used was an experimental trial using a Completely Randomized Design with 5 treatments and 3 replications, if there were significant influences followed by Duncan’s Multiple Range Test Method. The results show that Aspergillus sp. can be used to replace feliderm as a bating agent on goat’s skin leather tanning. The best result is T4 with the bending strength showing Nerf and the paint not cracking, the paint not fading at the value of 4/5, and the protein content with the value of 70,91%.

Experimental Study on Chrome Tanned Leather Shavings Modification—Properties and Prospective for Future Application

Chrome tanned leather shavings (CTLS) are considered one of the more difficult wastes to manage in the tanning industry. At the same time, this waste is an important source of good quality collagen. The few methods described in the literature for the valorization of these wastes usually require pre-treatment or activation. In this study, an attempt was made to see if raw chrome tanned leather shavings (CTLS) could be modified to obtain secondary raw materials with new physical properties. Glutaraldehyde, glycerol, EDCs, pectin, and tannins were selected for modification of the CTLS. The effectiveness of the processes carried out was confirmed by FTIR analysis of the materials obtained. Changes in the intensity of the characteristic collagen peak (amide I, amide II, and amide III) and changes in the position of the bands in the 1200–1000 cm−1 region were observed in the recorded spectra. The modifications introduced confirmed changes in the physical properties of samples M1–M5, including an increase in bulk density from 0.15 to 0.59 g cm−3, and improved tensile strength is some cases. The elemental content results of the samples tested showed the resulting modified CTLS were free of Cd, Hg, Pb, and Cr(VI). It was also confirmed tanning waste contained significant amounts of various valuable elements. The research also included preliminary tests to assess the environmental impact of the modified materials. In a phytotoxicity test conducted on modified CTLS, M1 with pectins showed the highest root stimulation (105%), while samples with glutaraldehyde and unmodified CTLS showed significant root inhibition (75%, 74%). Other samples showed moderate plant toxicity and seed germination was not significantly affected.

Evaluation of the Physical Properties of Goatskins Tanned using Banana (Musa spp.) Leaf Midrib Tannins

Vegetable tannins have been studied over the years with an aim to reduce the pollution load caused by chrome tanning. Although mimosa tannins have been utilized commercially, they are expensive and not readily available. The purpose of this study was to assess the physical properties of leather tanned with banana leaf midribs tannins in order to determine their suitability as vegetable tannins. Selected banana leaf midrib samples were collected from Gikondi village in Mukurweini, Nyeri County, Kenya. They were shade-dried and ground into powder. The skins were processed conventionally using banana leaf midribs tannins of Musa sapientum Linn. and ‘Muraru’ (AA genome), with mimosa as a control. The physical properties of the resultant leathers were determined following the standard IUP methods. It was found that Musa sapenitum Linn, ‘Muraru’ (AA genome) and mimosa-tanned leathers had average shrinkage temperatures of 80.33 ± 0.74°C, 78.67 ± 0.47°C and 81.67 ± 0.94°C, respectively. The properties of the tanned leathers were compared with those of the control-tanned leather. Assessment of the physical properties indicated that the leathers met the minimum recommended values safe for Musa sapentium Linn-tanned leather, which failed at 30,000 flexes. These results indicate that banana leaf midribs can be used as an organic tanning agent source for production of leathers from goatskins.

Exploring Vegetable-Tanned Leather as a Sustainable Alternative Material for Pottery Production. A Comparative Study of its Properties and Application

Vegetable tanned leather is a flexible material with numerous usages, this material is still unexplored by the pottery industry in Ghana with regards to the production of containers such as pots. It is clearly evident that local potters overly depend on materials as clay, cement and metals. This study is based on a qualitative research approach to evaluate the effectiveness of leather as an alternative material for the production of pots. The study aimed at manipulating indigenous tanned leather as an alternative material for the production of pots. The elements or individuals in the population are exogenous, so convenience and purposive sampling techniques were employed. From the Tamale Metropolis, a sample of 14 respondents were chosen, 5 of which were producers, 5 pot sellers, 2 pot users and 2 experts in the field of leather studies who all shared their ideas on the philosophies and concepts behind the production and use of pots. Interviews and observations were the main instruments used, based on the data collected, through experiments, leather was manipulated to produce pots. The Results showed that, indigenous leather is an effective substitute material for the production of pots in this contemporary era due to its qualities such as flexibility, durability and the beautiful nature of its surface after applying appropriate finishing/ decorative technique. In view of this, the researcher recommends that pot producers give a second thought to the use of leather as an equally viable material for production as this will pave way for improved human resource development as well as create alternative opportunities in the leatherwork industry in Ghana. This publication is deliberately designed as an additional motivation in expanding the effectiveness of vegetable tanned leather apart from its conservative convention for the production bags, sandals and footrests.

Rapid deterioration in buried leather: archaeological implications.

Understanding archaeological leather degradation helps inform economies, crafts, and technologies of historic communities. However, archaeological leather is at high risk of degradation due to deterioration and changes within the burial conditions. This research applied non-destructive FTIR-ATR to experimentally buried vegetable-tanned leather and archaeological leather excavated at the Roman site of Vindolanda, UK to explore survival, destruction, and preservation processes of tanned leather. Analyses focused on observing and monitoring changes in chemical functional groups related to leather tannins, collagen and lipid components following burial. FTIR-ATR results highlighted rapid changes following experimental burial in wet soil, tentatively associated with early onset microbial activity, which targeted readily available lipids but not tightly bound collagen. Prior to burial, differences in structural composition were present in leather spectra based on manufacture; however, following burial in wet soil, FTIR-ATR spectra indicated de-tanning occurs rapidly, especially in waterlogged conditions, with archaeological leather becoming more uniform and similar to untanned leather. Therefore, the comparison of FTIR-ATR results from archaeological leather to experimentally buried leather samples was informative for showing the destructive de-tanning in waterlogged environments. The comparison of FTIR-ATR data from modern unburied leather cannot be compared against archaeological samples. Importantly, despite de-tanning occurring soon after burial, the vegetable-tanning method promoted long-term preservation of leather in wet soil. The observed changes could not be directly associated with the proportion of condensed to hydrolysable tannin, suggesting alternate variables impacted the preservation. Furthermore, mineral components introduced into the leather through the animal skin, tannin material and/or tannin liquid are suggested to contribute to these changes. Crucially a high degree of heterogeneity in error results within the experimentally buried sample material underlined that any changes in collagen ratios cannot be overinterpreted and must be considered within the context of larger datasets.

Determination of the Composition of Wastewater from Individual Processes of Leather Tanning Production in a Small Plant

Determination of the Composition of Wastewater from Individual Processes of Leather Tanning Production in a Small Plant

Flotation of Chromium Ions from Simulated Wastewater Using Air Microbubbles

A microbubble air flotation technique was used to remove chromium ions from simulated wastewater (e.g. water used for electroplating, textiles, paints and pigments, and tanning leather). Experimental parameters were investigated to analyze the flotation process and determine the removal efficiency. These parameters included the location of the sampling port from the bottom of the column, where the diffuser is located to the top of flotation column (30, 60, and 90 cm), the type of surfactant (anionic, SDS, or cationic, CTAB) and its concentration (5, 10, 15, and 20 mg/L), the pH of the initial solution (3, 5, 7, 9, and 11), the initial contaminant concentration (10, 20, 30, and 40 mg/L), the gas flow rate (0.1, 0.2, 0.3, and 0.5 L/min), and the contact time (5, 10, 15, 20, 25, 30, and 35 min). The experimental results revealed that the highest removal efficiency (95%) was achieved in 20 min with a pH of 7, a flow rate of air 0.5 L/min, an SDS surfactant concentration of 15 mg/L, and a pollutant concentration of 30 mg/L at a sampling port height of 30 cm. The use of microbubbles in comparison to normal bubbles, resulted in a 56% improvement of the removal efficiency. The flotation process follows a first-order kinetics.