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In sub-Saharan Africa, chromium tanning during leather processing constitute one of the significant sources of large amounts of hazardous solid and liquid waste. The release of chromium with high poisonous quality and portability still remains a big concern for any ecosystems. Poor or improper management of chromium-rich wastes can result in irreve...
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... tanning is the most adopted tanning method in leather industries for the conversion of animal hides and skins into useful artefacts. This is accomplished by continuous agitation of the skins/hides in large rotating drums containing chromium sulphate solution, allowing for the tanning agent to be evenly distributed (Fig. 1). During chrome tanning process, the positively charged chrome tanning agent i.e. hydrated chromium ions binds with negatively charged collagen carboxyl group through a coordinate bond to fix the structure of collagen fibre, thereby giving tanning effects such as thermostability, chemical resistance and flexing endurance ( Beghetto et ...
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Waste management in leather processing is crucial in limiting the excess use of hazardous materials that lead to environmental pollution and health concerns. A closed-loop approach was developed to recycle the spent solutions from leather processing to reduce waste in the effluent. The structural changes of collagen that accompany such processing a...
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... Generally, vegetable-tanned leather is highly valued because of its adaptability and the process is eco-friendly [16]. Basic chromium sulphate used in tanning might occasionally be left behind by traditional chrome tanning techniques [17]. Higher quantities of chromium compounds are carcinogenic and highly hazardous to public health [18]. ...
For commercial leather processing, chrome tanning is the most used approach but it significantly contributes to environmental pollution. Vegetable tannins, which are large polyphenolic compounds, form strong interactions with proteins and carbohydrates, thereby enhancing the adaptability and value of vegetable-tanned leather as well as reducing environmental impact. In this study, vegetable tannins were extracted from the leaves of Guava plants (Psidium guajava) using ethanol as the solvent, facilitated by ultrasound. Extracted tannins were quantified using the Folin-Ciocâlteu reagent with ultraviolet-visible spectroscopic method. Ultrasound enhanced the extraction process producing a high yield in less time due to its mechanical, thermal, and cavitation impacts. The extracted tannins were characterized by a variety of spectroscopic techniques, including Proton (1H) Nuclear magnetic resonance, Fourier-transform infrared, and ultraviolet-visible spectroscopy. The effect of various process variables, such as temperature, solid-liquid ratio, ultrasonic power, extraction period, and powder fineness, were also investigated to optimize the extraction process. Finally, the extracted tannins were employed in leather tanning processes to assess their potential as tanning agents. The extracted tannins ensured uniform diffusion of tannins, improved thermal stability and reduced the number of tannins in effluent by 68% making it an environmentally friendly leather tanning process.
... Generally, vegetable-tanned leather is highly valued because of its adaptability and the process is eco-friendly [16]. Basic chromium sulphate used in tanning might occasionally be left behind by traditional chrome tanning techniques [17]. Higher quantities of chromium compounds are carcinogenic and highly hazardous to public health [18]. ...
For commercial leather processing, chrome tanning is the most used approach but it significantly contributes to environmental pollution. Vegetable tannins, which are large polyphenolic compounds, form strong interactions with proteins and carbohydrates, thereby enhancing the adaptability and value of vegetable-tanned leather as well as reducing environmental impact. In this study, vegetable tannins were extracted from the leaves of Guava plants (Psidium guajava) using ethanol as the solvent, facilitated by ultrasound. Extracted tannins were quantified using the Folin–Ciocâlteu reagent with ultraviolet-visible spectroscopic method. Ultrasound enhanced the extraction process producing a high yield in less time due to its mechanical, thermal, and cavitation impacts. The extracted tannins were characterized by a variety of spectroscopic techniques, including Proton (1H) Nuclear magnetic resonance, Fourier-transform infrared, and ultraviolet-visible spectroscopy. The effect of various process variables, such as temperature, solid-liquid ratio, ultrasonic power, extraction period, and powder fineness, were also investigated to optimize the extraction process. Finally, the extracted tannins were employed in leather tanning processes to assess their potential as tanning agents. The extracted tannins ensured uniform diffusion of tannins, improved thermal stability and reduced the number of tannins in effluent by 68% making it an environmentally friendly leather tanning process.
... The leather goods industry was worth USD 245 billion in 2022 [13] and stands out as one of the most environmentally impactful and resource-intensive sectors. From every 1000 kg of raw material, 250 kg of leather is produced, leaving a substantial water footprint ranging from 15,000 to 120,000 cubic meters [14]. This process results in the generation of 15 to 50 metric tons of wastewater and 400 to 700 kg of solid waste, greenhouse gases (such as CO 2 , H 2 S, and NH 3 ), as well as volatile organic compounds like amines, aldehydes, and hydrocarbons [12]. ...
Tanning, crucial for leather production, relies heavily on chromium yet poses risks due to chromium’s oxidative conversion, leading to significant wastewater and solid waste generation. Physico-chemical methods are typically used for heavy metal removal, but they have drawbacks, prompting interest in eco-friendly biological remediation techniques like biosorption, bioaccumulation, and biotransformation. The EU Directive (2018/850) mandates alternatives to landfilling or incineration for industrial textile waste management, highlighting the importance of environmentally conscious practices for leather products’ end-of-life management, with composting being the most researched and viable option. This study aimed to isolate microorganisms from tannery wastewater and identify those responsible for different types of tanned leather biodegradation. Bacterial shifts during leather biodegradation were observed using a leather biodegradation assay (ISO 20136) with tannery and municipal wastewater as the inoculum. Over 10,000 bacterial species were identified in all analysed samples, with 7 bacterial strains isolated from tannery wastewaters. Identification of bacterial genera like Acinetobacter, Brevundimonas, and Mycolicibacterium provides insights into potential microbial candidates for enhancing leather biodegradability, wastewater treatment, and heavy metal bioremediation in industrial applications.
... The leather goods industry was worth USD 245 billion in 2022 [13] and stands out as one of the most environmentally impactful and resource-intensive sectors. From every 1,000 kg of raw material, 250 kg of leather is produced, leaving a substantial water footprint ranging from 15,000 to 120,000 cubic meters [14]. This process results in the generation of 15 to 50 metric tons of wastewater and 400 to 700 kg of solid waste, greenhouse gases (such as CO2, H2S, NH3), as well as volatile organic compounds like amines, aldehydes, and hydrocarbons [12]. ...
Tanning, crucial for leather production, relies heavily on chromium yet poses risks due to chromium's oxidative conversion, leading to significant wastewater and solid waste generation. Physico-chemical methods are typically used for heavy metal removal, but they have drawbacks, prompting interest in eco-friendly biological remediation techniques like biosorption, bioaccumulation, and biotransformation. The EU Directive (2018/850) mandates alternatives to landfilling or incineration for industrial textile waste management, highlighting the importance of environmentally conscious practices for leather products' end-of-life management, with com-posting being the most researched and viable option. This study aimed to isolate microorganisms from tannery wastewater and identify those responsible for different types of tanned leather biodegradation. Using a leather biodegradation assay (ISO 20136) with tannery and municipal wastewaters as inoculum, bacterial shifts during leather biodegradation were observed. Over 10,000 bacterial species were identified in all analyzed samples, with 8 bacterial strains isolated from tannery wastewater. Identification of bacterial genera like Acinetobacter, Brevundimo-nas, and Mycolicibacterium provides insights into potential microbial candidates for enhancing leather biodegradability, wastewater treatment, and heavy metal bioremediation in industrial applications.
... The leather industry is an elderly manufacturing sector producing a broad range of house and living things related to people's livelihoods, e.g., shoes, gloves, bags, belts, sofas, car cushions [1]. The global leather industry has recently sought more environmentally friendly, chrome-free manufacturing technologies due to the ever-increasing public concern, strict legislative control, and ecological awareness of chrome pollution [2]. This new movement toward sustainability has been called eco-friendly leather production. ...
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 (compo-nent 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.
... Processing one tonne of wet salted material could generate 226 kg of tanned Cr leather scrapes and 27.5 billion of Cr-containing effluent (Pradeep et al. 2021). This kind of waste poses a series threat to the environment and its adhered ecosystem if untreated properly (Oruko et al. 2020). Presence of specific oxidizing medium drastically increases the risk of Cr conversion to its hexavalent state, which has severe carcinogenic and mutagenic effects (Dubey et al. 2022). ...
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.
Graphical Abstract
... The leather industry also emits an obnoxious smell due to protein degradation of the skin which results in the generation of toxic gases such as ammonia, H2S, etc. (Oruko et al., 2020). Based on this research data, only 20% of the rawhide is used for the production of leather, and the remaining is generated as waste. ...
The study aims at optimizing the uptake of tannins obtained from Piliostigma thonningii by goat skin, using a central composite design. The study was carried out using the central composite design of experiment version 10.0.3.1 which consists of four factors. Bark of Piliostigma thonningii were collected freshly. The barks were dried in an electric oven at a temperature, of 100-105oC and later crushed to powder, to increase the surface area. The samples of goat skin were obtained and were then divided vertically through the backbone into two equal halves, and subjected to the standard procedure of the leather tanning processes. The samples of skin pieces obtained were tanned using the standard procedure of leather tanning. The plant samples were subjected to four experimental conditions, concentration (%), pH, particle size (mm), and time (min). The result indicates that the optimization conditions required for the uptake of tannins by the sample (goat skin) were 20% of plant material, pH of 4.81, 1.988 mm of particle size, and 50 min of time. The optimum responses of the leather produced were 77°C (shrinkage temperature), 27.934 N/mm2 (tensile strength), 13.009 mm (lastomer distention), and 0.293% (water vapor permeability) obtained respectively. Control of these parameters resulted in producing the most stable and flexible leather, which will release fewer contaminants into the environment. Based on the result obtained in the study, Piliostigma thonningii bark can be used as one of the vegetable tanning materials.
... 2023.116 COD and BOD as well as high amounts of chromium and calcium content [2]. Although the leather industry significantly contributes to Bangladesh's national economy through income and employment opportunities, it also creates an enormous amount of solid and liquid waste from its manufacturing system [3]. ...
Chrome tanning is the most popular and widely used method utilizing basic chromium salts in leather processing. Only 60-70% of these salts react with collagen to form leather. The rest remains unreacted being released as toxic waste and causing severe environmental pollution in many developing countries. In the current study, a significant approach was made to utilize solid waste with a clean environment perspective. The chromium was extracted as basic chromium sulfate using H2SO4 from tannery waste and reused in the leather manufacturing procedure. Extracted solid sludge was examined by Atomic Absorption Spectrometry and elemental analysis before and after the separation of chromium (III). It revealed that 97% of chromium was extracted from tan yard sludge. Recovered chromium sulfate was reused in goat skin processing. Batch experiments were carried out by applying recovered basic chromium sulfate, and a combination of fresh and recovered basic chromium sulfate solutions separately. Fresh basic chromium sulfate was used as the control method. The structure and morphology of the final processed leather were characterized by Field Emission Scanning Electron Microscope (FESEM) and Thermogravimetric analysis (TGA). The identical structural morphologies of all processed leather were confirmed in the FESEM study. The physical and chemical characteristics of all finished leather were found very similar. The TGA analysis data proved that raw leather processed by recovered chromium is thermally more stable than others. These research findings signify a new potential effort of separating important chemicals from solid sludge and reusing them. This technique is simple, cost-effective, eco-friendly, and sustainable as it reduces environmental pollution from tannery chromium waste.
... For the BS strategy, the addition of nutrients stimulated the growth of several microbes that produced acid, leading to the re-dissolution of Cr(VI). This is consistent with previous studies, which reported that oxidative microbial species were able to leach the heavy metals as well as being involved in the process of producing acids [66,67]. Furthermore, the addition of nutrients significantly decreased the bacterial diversity, which was not beneficial to the ecological balance of the soil [68]. ...
Unchecked releases of industrial waste, including chromium smelting slag (CSS), have resulted in disastrous effects on the environment for human use. Considering the problems of environment, efficiency, and sustainability, the present research was designed to evaluate the potential feasibility of Cr(VI) bioremediation by different strategies of natural attenuation (NA), bioaugmentation (BA), biostimulation (BS), and bioenhancement (BE). Results showed the BE was the best strategy for Cr(VI) removal and reached 86.2% in 84 days, followed by the BA, BS, and NA. The variation of Eh values indicated all systems translated the oxidation state into reduction continuously except for NA and BS during the bioremediation process. After bioremediation, the Tessier sequential extraction analyzed in the BE showed stable chromium levels up to 97%, followed by BA (89~93%), BS (75~78%), and NA (68%), respectively. Moreover, High-throughput sequencing was also used to assist in revealing the differences in microbial community structure between the different strategies. Stenotrophomonas, Ochrobactrum, and Azomonas, as the bioremediation microbes, were enriched in the BE in comparison with the others. This provided a new enhancement strategy for bioremediation microbes colonized in a new environment to achieve sustainable removal of Cr(VI).
... The discharge of a high amount of Cr(VI) from the recycling of electronic waste caused a high concentration of Cr(VI) in the blood of children in Guiyu, China, which could negatively affect the physical growth of children in that area (Xu et al., 2015). Over exposure to Cr(VI) species caused conjunctivitis and dermatitis among tannery workers from the tanning industry in Dhaka, Bangladesh (Oruko et al., 2020). High concentrations of Cr(VI) in River Ganga, India caused the extinction of the fish population (i.e., Labeo rohita) (Paul, 2017). ...
Heavy metals, such as chromium, copper, lead and nickel are commonly found in industrial effluent. Of these, chromium is one of the heavy metals that gains more attention worldwide, primarily related to its hexavalent compounds (Chromium (VI)) owing to its toxic effects on humans and other living organisms. Although this element can be adsorbed by various adsorbents, the adsorption alone experienced few drawbacks such as small capacity, agglomeration of particles and difficulty for large-scale application. This chapter is organized into four sections. Section 2.1
presents the background of Cr(VI). Section 2.2 describes the formsnof Cr(VI) in water. Section 2.3 provides the removal of Cr(VI) from contaminated water by membrane filtration technique. Finally, the conclusion is presented in Section 2.4.
