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Vegetable tannins are environmentally friendly tanning agents. However, they generally impart a dark colour to the tanned leather and highly contribute to the organic load in wastewaters. In this study, we employed a purification protocol separately on chestnut tannin (CT) and sulfited quebracho tannin (QT) to obtain the purified fractions (PCT and PQT). These samples were characterised by GPC, 1H NMR, 13C NMR, FT-IR, and HPLC–DAD techniques and applied for tanning tests. Through the purification process, non-tannin components and smaller molecules such as gallic acid, glucopyranose, and catechin were effectively removed from CT and QT, which consequently led to the reduced moisture content, pH value, and lighter colour of purified fractions. The crust leathers processed with PCT and PQT showed desirable light shades. Moreover, the organic loads in PCT and PQT tanning wastewater were reduced by 13.5% and 19.1%, respectively, when compared to those in traditional CT and QT tanning wastewater. Additionally, the physical and mechanical characteristics of crust leathers processed with PCT and PQT were comparable to those processed with CT and QT. Thus, purification of vegetable tannins may serve as a feasible strategy for producing light-colored vegetable-tanned leather while minimizing organic pollutant discharge during the vegetable tanning process. [ABSTRACT FROM AUTHOR]

The post‐tanning process of leather making involves the of large quantities of auxiliary chemicals to enhance the functionalities of the leather. Hence, developing multifunctional polymers are essential to reduce the pollution load and enhance sustainability. Herein, we report the synthesis of multifunctional retanning and fatliquoring agent using a hydroxyethyl methacrylate (HEMA) monomer by modifying the hydroxyl group to carboxyl and long‐chain hydrocarbon along with quaternary ammonium monomer. The resulting polymer has been subsequently used in the tanning and post‐tanning process. The influence of the carboxyl group increases the metal uptake of the aluminum (twofold) and zirconium (1.5‐fold) tanning agent, and hydrothermal stability of the polymer‐treated leathers is 74 and 81°C for aluminum and zirconium tanning, respectively. The experimental leather showed uniform pore size distribution and better organoleptic characteristics than the control. Introducing the quaternary ammonium group in the polymer increased dye exhaustion in the experimental process up to 97%. The anti‐bacterial studies show the polymer is effective against gram‐positive species due to electrostatic interaction. The biochemical analysis of the experiment process shows higher biodegradability (0.62). Thus, the present study opens a new avenue for a sustainable replacement for conventional post‐tanning chemicals. [ABSTRACT FROM AUTHOR]

• The aging process of leather was artificially accelerated. • Changes in secondary collagen structure was analyzed by deconvoluted FT-IR spectrum. • Thermal stability of vegetable-tanned leather was studied by TG/DTG. Leather artifacts, mainly composed of collagen and tanning agents, possess significant historical importance. However, external factors could lead to the aging of such artifacts during preservation. Therefore, it is crucial to examine the impact of various factors on leather aging. In order to know the effects of high temperature and humidity conditions on the changes of leather artifacts, the traditional vegetable tanning agents (chestnut, tara, quebracho, and mimosa) were used to tan the pickled sheepskins to prepare leather artifact model samples. The leather artifact model samples were aged for 0, 2, 4, 8, 16, and 32 days at 80°C and 40–80 % relative humidity (RH). The changes in appearance, structure and thermal stability of the vegetable-tanned leather samples under the synergistic impact of temperature and RH were analyzed using total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), chromatography, and scanning electron microscopy (SEM). The thermal degradation of the samples before and after being tanned with vegetable tanning agents was analyzed using thermal gravimetric analyzer (TGA) analysis. Furthermore, the shrinkage temperature (Ts), tensile strength and elongation at break of the samples were investigated during different aging periods. The study aims to provide valuable insights into the stability of leather artifacts during long-term storage, as well as guidance for their restoration and conservation. [ABSTRACT FROM AUTHOR]

The current study set out to assess and create long-term solutions for improving environmental performance concerning water use, wastewater production, and treatment at Syntan plant (glass-lined vessel unit) and application laboratory (small-scale leather retanning. Based on evaluations and analyses, best available techniques including water gauging, pressurized vessel washing, dedication of vessels to similar production, reuse techniques, developing commercial grade intermediate products from wash water, managing cooling water and developing reuse methods of reverse osmosis reject water were applied to reduce water consumption and effluent generation in process and non-process activities. Furthermore, the reduced effluent was subjected to treat using electrochemical processes, i.e., electrocoagulation and electro-Fenton, before it was drained to outside environment. As a result of the applications, 0%-100% change was measured in various process and non-process activities, whereas, 12.8%-100% reduction was measured in effluent. Soft cooling water consumption was reduced by 46.7%. The results of treated effluent parameters were compared and found the final removal efficiencies of total dissolved solids (51.4%), total suspended solids (99.2%), chemical oxygen demand (98.5%) and electric conductivity (67.7%). It is concluded that this study can be considered as a successful model to increased water efficiency in chemical industries, Furthermore, it could serve as a building block for the incorporation of cleaner and sustainable production approach into national agenda and to overcome stern issues of high-water and energy consumption and effluent management in different industries. [ABSTRACT FROM AUTHOR]

This study explored the potential application of polyphenols from Pinus halepensis bark in leather tanning. The primary objective was to characterize these polyphenols. The extraction and atomization processes proved efficient, reducing moisture content to 7.4%, increasing tannin content from 26.2% to 45.1%, and reducing insoluble substances by 77.5%. High-performance liquid chromatography (HPLC) coupled with mass spectrometry identified and quantified various polyphenolic compounds, including (+)-catechin, (+)-taxifolin, protocatechuic acid, and procyanidin B2. Notably, tannic catechin dimers were detected. Lignin was effectively removed through filtration. Concentrations of protocatechuic acid, (+)-catechin, (+)-taxifolin, (−)-epicatechin, and procyanidin B1 were significantly higher in the extract than in the powder, with the extract showing 1214.3 mg/kg of protocatechuic acid, 2098.0 mg/kg of (+)-catechin, 4017.0 mg/kg of (+)-taxifolin, 2163.0 mg/kg of (−)-epicatechin, and 917.0 mg/kg of procyanidin B1. [ABSTRACT FROM AUTHOR]

In this study, decolorization via a bleaching operation was carried out on chrome and dye spotted skins with several bleaches to valorize the defective leather materials. Sodium perborate, hydrogen peroxide, sodium thiosulfate, sodium percarbonate, and oxalic acid were applied as bleaching agents in production. Sodium perborate by itself was applied and combined with other bleaching agents. Combined processes were also supported with an emulsifier agent for uniform distribution and deeper penetration of bleaching agents into the fibers. Color changes and differences on leather products were determined by Konica Minolta CM-3600d test apparatus spectrophotometrically before and after the applications. Bleached leathers were processed again, re-dyed, and finished after the bleaching operations. Then, bleaching performances of the single and combination applications were also evaluated for the leather strength indicators by analyzing tensile and tear strength of the final products as well as chromium (VI) oxidation of basic chromium (III) salts used in tanning. Antibacterial properties of the final bleached products were also investigated. As a result, sodium perborate was found to provide the most effective and safe bleaching without any physical and chemical deformation by creating antibacterial activity on leather. [ABSTRACT FROM AUTHOR]

The study investigates the potential of anaerobic co-digestion (AcoD) as a sustainable solution for managing putrescible organic waste generated by leather processing. Three experiments were conducted to assess the impact of various tannery wastes, pretreatment methods, and waste combinations on methane production. Experiment 1 demonstrated that co-digesting tannery wastewater primary sludge (TWPS) and fleshings significantly increased methane yield compared to digesting TWPS alone, though the addition of chromium- and vegetable-tanned leather wastes decreased yield. Experiment 2 explored TWPS pretreatment methods and found that ultrasonic pretreatment increased soluble chemical oxygen demand (SCOD) but did not significantly improve methane yield, suggesting that pretreatment may not be necessary. Experiment 3 revealed that increasing the proportion of fleshings to TWPS resulted in higher methane yield, ranging from 226.52 mL/gVS with 6% fleshings to 395.71 mL/gVS and 538.34 mL/gVS with 12% and 20% of fleshings, respectively. Additionally, this increase in fleshings also led to a reduction in digester volume. These findings highlight the importance of AcoD in addressing both environmental and economic challenges in the leather industry. [ABSTRACT FROM AUTHOR]

Tanoak (Notholithocarpus densiflorus) is an evergreen tree in the Fagaceae family found in California and southern Oregon. Historically, tanoak acorns were an important food source for Native American tribes, and the bark was used extensively in the leather tanning process. Long considered a disjunct relictual element of the Asian stone oaks (Lithocarpus spp.), phylogenetic analysis has determined that the tanoak is an example of convergent evolution. Tanoaks are deeply divergent from oaks (Quercus) of the Pacific Northwest and comprise a new genus with a single species. These trees are highly susceptible to "sudden oak death" (SOD), a plant pathogen (Phytophthora ramorum) that has caused widespread deaths of tanoaks. In this study, we set out to assemble the genome and perform comparative studies among a number of individuals that demonstrated varying levels of susceptibility to SOD. First, we sequenced and de novo assembled a draft reference genome of N. densiflorus using cobarcoded library processing methods and an MGI DNBSEQ-G400 sequencer. To increase the contiguity of the final assembly, we also sequenced Oxford Nanopore long reads to 30× coverage. To our knowledge, the draft genome reported here is one of the more contiguous and complete genomes of a tree species published to date, with a contig N50 of ∼1.2 Mb, a scaffold N50 of ∼2.1 Mb, and a complete gene score of 95.5% through BUSCO analysis. In addition, we sequenced 11 genetically distinct individuals and mapped these onto the draft reference genome, enabling the discovery of almost 25 million single nucleotide polymorphisms and ∼4.4 million small insertions and deletions. Finally, using cobarcoded data, we were able to generate a complete haplotype coverage of all 11 genomes. [ABSTRACT FROM AUTHOR]

The development of new tanning agents in the leather sector is urgently needed to cope with the increasing environmental pressure on the use of current tanning materials and processes. The best alternative tanning agent to replace chromium which is not environmentally friendly is titanium-based sulfate salts (IV). These compounds are most recommended to be developed and used in new, cleaner tanning processes for the leather industry. The main source of Ti(SO4)2 comes from the mineral ilmenite (FeTiO3) extracted using H2SO4. The extraction process will produce a mixture of Ti(SO4)2 and Fe(SO4) in the H2SO4-FeSO4-Ti(SO4)2-H2O system at high acidity of H2SO4. The purpose of this study is to separate each of these compounds based on their solubility in methyl alcohol. This study discusses the comparison of feed and residue with FTIR, residual characteristics with XRD and XRF. While the results of quantitative analysis of each final product of Ti(SO4)2 and Fe(SO4) compounds using XRF. Qualitative results using FTIR show that Ti(SO4)2 images are different from FeSO4. The %recovery result in the optimal state of H2SO4 extraction obtained Ti(SO4)2 was 20.6%, while FeSO4 was only 9.2% from the feed of 30 g ilmenite. [ABSTRACT FROM AUTHOR]

Summary: Burdekin plums (BP) are the fruits of Pleiogynium timoriense (DC.) Leenh, a tree native to Australia. In this study, BP fruit leathers were developed by blending BP puree with apple puree (0%–80% levels) to make five formulations of BP fruit leathers (100BP, 80BP, 60BP, 40BP, 20BP). Physicochemical parameters and microbial stability of fruit leathers were studied during six‐month storage at ambient conditions (temperature 16–25 °C, humidity 60%–77%). Results showed that BP leathers had a water activity from 0.60 to 0.64 and moisture content from 21% to 25%, and both were stable during storage. 20BP had the highest score for all colour parameters measured and had the lowest value in hardness. Reduction in redness and chroma and an increase in hue were observed in all leathers after storage. The total content of cyanidin 3‐galactoside and cyanidin 3‐glucoside decreased from 400–1600 mg/kg DW to 100–500 mg/kg DW after processing into leathers then to 9–70 mg/kg DW after storage. A decrease in catechins was also observed after puree was processed into leather and after the 6 months of storage, whereas an increase in gallic acid, ellagic acid, quercetin 3‐glucoside, trigalloylglucose was observed particularly in 20BP. Total phenolic content (ranging from 6 to 24 mg GAE/g DW) and antioxidant capacity (ranging from 80 to 240 μmol Fe2+/g DW) remained relatively stable after processing and storage with a slight reduction in 80BP and 100BP. Fruit leathers were microbiologically safe and shelf‐stable during the 6 months of storage. These results demonstrated the potential of BP to be processed into shelf‐stable fruit leathers rich in bioactive phenolics. [ABSTRACT FROM AUTHOR]

The object of the study was the process of coagulation treatment of wastewater of leather industry enterprises. The treatment of samples of real wastewater from a leather production was investigated. Such wastewater is characterized by high concentrations of pollutants of varying degrees of dispersion, which is due to the use of a large number of various chemicals in the leather production process. During technological operations related to the skinning and processing of skins, these substances enter the wastewater, which is discharged into the sewer. A peculiarity of leather production wastewater is large fluctuations in composition and volume, high concentrations of pollutants, and an increased content of suspended solids. Such waters have certain toxicity. The existing methods of wastewater treatment of leather industry enterprises do not provide the necessary treatment efficiency, do not allow to create a closed circulation of water at enterprises, to use or regenerate valuable components of wastewater, and to ensure their economically feasible disposal. Therefore, the research is aimed at improving the process of coagulation wastewater treatment of leather factories using mathematical modeling and optimization methods. This will make it possible to modernize existing wastewater treatment schemes. The experiments were carried out on the Niva Jar-test laboratory unit, which allows simultaneous examination of 6 samples. Samples of wastewater from leather production after the fattening-filling and dyeing stages were studied. The effectiveness of the coagulation process was determined by the degree of wastewater treatment. The factors were analyzed and the intervals of variation of factors that have a significant impact on the process of coagulation treatment of wastewater from leather factories were established. An experiment plan was drawn up and implemented in order to study the effect of coagulants based on aluminum and ferrum, as well as flocculants on the quality of wastewater treatment. The choice of quality indicators of the coagulation process is substantiated. A statistical analysis of the results of experimental studies was performed, a correlational analysis of the interdependence of parameters and indicators of the quality of the coagulation process was performed. Aluminum-based coagulant has been found to be more effective than iron-based coagulant. The results of mathematical modeling were used to determine the optimal parameters of the coagulation process: pH 10, coagulant dose – 2.5 g/dm³, flocculant dose – 100 mg/dm³. [ABSTRACT FROM AUTHOR]

Bating animal hides with trypsin is an essential step for making leathers. But the mechanism why the calcium in the hide influences the bating performance remains unclear. Here, the enzyme activity of trypsin was determined using N-alpha-benzoyl-L-arginine ethyl ester, bovine albumin (BSA) and collagen fibres as substrates in the presence and absence of calcium salts. The interactions of calcium with trypsin, BSA and collagen were analysed by fluorescence spectroscopy and molecular docking. Data reveal that calcium which binds to BSA and collagen improves the structural stability and enzyme resistance of hide proteins. As a result, a high calcium content of delimed hide is useful to obtain an intact surface of bated hide. However, a low calcium content of hide for pickling is necessary for producing leathers with high physical properties and uniform colour. According to these results, a novel bating system involving deliming, bating and redeliming operations was developed. This system provides a high calcium content of hide for bating and a low calcium content of hide for subsequent pickling and tanning, which effectively reduces the risk of hide damage and improves the physical properties and colour uniformity of leather. [Display omitted] • How calcium salts affect hydrolysis of hide proteins with trypsin in bating was revealed. • A high calcium content of delimed hide protects the grain surface of hide. • A low calcium content of hide is necessary for high physical properties of leather. • A novel system involving deliming, bating, and redeliming operations was designed. • This system effectively reduces the risk of hide damage and can ensure leather quality. [ABSTRACT FROM AUTHOR]

The use of collagen is the recent development in various medical fields. Huge quantities of hide and skin trimmings are generated during the leather processing are wasted or underutilized. Trimmings contain collagen which can be beneficially extracted and utilized for high value products. Poly methyl methacrylate based denture materials exhibit serious concerns such as high porosity, presence of residual monomer, shrinkage, distortion and high rate of deterioration of the materials. This study aims to incorporate extracted Type I collagen with polymer to obtain denture base and investigate its chemical and mechanical properties. The present research methodology also reduces the quantity of monomer and acrylic resin usage. The collagen was extracted from animal skin and hide trimmings which are otherwise disposed as wastes. This study investigated the effect of visco-elastic characteristics of resulted specimens and their transition temperature, mechanical properties, decomposition temperature and leachability. The collagen-based specimens have better tensile strength with high decomposition temperature compared to control specimens. Scanning Electron Microscopy analysis revealed that the experimental specimens was cohesive and homogeneous which explained the higher tensile and decomposition values. The study suggests that collagen cross-linked acrylic denture base exhibit better mechanical and thermal resistance properties when compared to control specimens. The study indicates that biomaterials are emerging as smart products of value in human health. [ABSTRACT FROM AUTHOR]

Currently, the textile industry is a poorly automated sector, due in part to problems in the handling of deformable leather and textile parts during production operations. In this work, several problems in the handling process of leather and textile parts are addressed, introducing methods to increase the automation of the process. A pneumatic actuator designed to pick up textile or leather parts avoiding their deformation during transport has been developed. This actuator maximizes the number of gripping points to improve handling, making it more stable and efficient. Additionally, a vision system has been implemented in the part-picking task which, in conjunction with the CAD information of the part, sends the modified gripping position of the part to the robot. This allows customized handling of each textile or leather part. Finally, validation tests have been carried out on this development, both in simulations and in laboratory conditions, demonstrating its viability and direct applicability in the production line. [ABSTRACT FROM AUTHOR]

Biodegradability is a crucial indicator to evaluate the sustainability of leather. Herein, a rapid method for biodegradation test in an aqueous medium by measuring biochemical oxygen demand was used to determine the biodegradability of leather from different tanning methods, tanning conditions and process stages. In addition, the difference in biodegradability between leather and leather-like synthetic materials were investigated. Chrome-free tanned leather showed higher degree of biodegradation and faster biodegradation rate than chrome tanned leather. Among them, leathers tanned with biomass-based tanning agents were much easier to biodegrade because the crosslinking network of tanned leather constructed with biomass was more susceptible to microbial attack. The enhancement of tanning effects through changing tanning methods and conditions (such as tanning agent dosage, pH and temperature) resulted in the decline of leather biodegradability. Future development of novel chrome-free tanning technologies should balance between these two aspects. The biodegradability of leather from tanning to post-tanning to finishing showed a stepwise decrease because various chemicals were applied and bound to leather during processing. Even so, finished leather still possessed significantly higher biodegradability compared to leather-like PU and microfiber synthetic materials, demonstrating superior environmental sustainability of natural leather. The results are expected to provide support for the evaluation of the ecological properties of leather and green upgrade of the leather industry. [ABSTRACT FROM AUTHOR]

The leather industry generates a significant amount of various wastes, and their utilisation is a serious task for researchers. Ways to reuse or decontaminate such waste are being developed intensively. Unfortunately, the reuse of finished leather, which eventually becomes waste, is almost unexplored. The present research is designed to evaluate the potential of finished leather hydrolysis to obtain protein hydrolysates suitable for reuse in leather processing and to establish factors that influence leather quality during such an application. Enzyme preparation Vilzim PRO Conc was characterised as a potential agent for such hydrolysis. The addition of 3-4% Vilzim PRO Conc is appropriate for the enzymatic stage of the hydrolysis process. It was established that after alkalineenzymatic hydrolysis of used leather powder the obtained hydrolysates are complicated systems containing proteins, chromium compounds, dyes, fatliquoring materials, etc. Hydrolysates could be used for the dyeing of chromed leather. The method of preparation for dyeing and dyeing of wetblue leather with the use of hydrolysate influences the depth of dye penetration and the quality of finished leather. It was established that the neutralisation process is not necessary before such dyeing. Also, an increased amount of formic acid is necessary to improve the bonding of fatliquors with dermal tissue after treatment with hydrolysate. [ABSTRACT FROM AUTHOR]

The article introduces one of the leather industries, the tanning industry, which is responsible for some of the most critical processes that leather undergoes before it is used in subsequent parts of the industry. Since the processes carried out require significant amounts of water, they generate equally large amounts of wastewater, which, as industrial wastewater, requires appropriate treatment. Additionally, due to the quantities and complexity of the processes carried out, the chemicals used become demanding in terms of how they are treated and managed. The parameters of wastewater subjected to a collection in a typical tank are changed. In contrast, wastewater from chromium tanning processes, which should be discharged into a separate tank, is a source of chromium pollution with its high content, thus posing a significant danger to the environment. The study made it possible to assess the biodegradability of wastewater generated during production and the concentration of chromium compounds and other pollutants. Based on the results, it was found that the wastewater generated during the production process is biodegradable (except for mixed wastewater), and the concentration of chromium is 2.81-3.11 g/dm³. [ABSTRACT FROM AUTHOR]

Loquat (Eriobotrya japonica Lindl.) is a perishable fruit with a huge potential for processing. In this study, the effects of food processing techniques and in vitro gastrointestinal digestion on the phenolics of loquat products were investigated. For this purpose, the results of processed loquat products including juice, nectar, leather, pulp, and jam were compared to the control loquat samples. Spectrophotometric and chromatographic methods were used to analyze the total phenolic (TPC) and total flavonoid contents (TFC), individual phenolic compounds (chlorogenic acid, p-coumaric acid, epicatechin) as well as total antioxidant capacity by DPPH and CUPRAC assays. The TPC and TFC of loquat products varied from 61.2±5.4 to 855.7±36.0 mg GAE/100 g and 37.2±1.6 to 979.5±65.3 mg CE/100 g, respectively. As in total phenolics, flavonoids, and antioxidants, the highest chlorogenic acid, p-coumaric acid, and epicatechin contents were obtained in loquat leather as 201.20±9.99 mg/100 g, 47.50±2.21 mg/100 g, and 46.87±0.28 mg/100 g, respectively. In addition to these, after in vitro gastrointestinal digestion, it was revealed that loquat leather had the highest TPC, TFC, and total antioxidant capacity values compared to other samples. Results have indicated that the phenolic content of fresh loquat fruits could be improved or protected, mainly by processing into leather and/or jam. Thus, the product scale for this fruit can be increased by obtaining foods with high nutritional value. [ABSTRACT FROM AUTHOR]

The leather-making process necessitates large amounts of water and consequently generates tons of liquid waste as leather tannery wastewater (TWW) is disposed of directly in the open environment. Open disposal of untreated TWW into the natural environment causes an accumulation of various polluting compounds, including heavy metals, dyes, suspended solids inorganic matter, biocides, oils, tannins, and other toxic chemicals. It thus poses potential hazards to the environment and human health. This study primarily focuses on providing in-depth insight into the characteristics, treatment strategies, and regulatory frameworks for managing TWW in leather processing industries. Different technologies of conventional physico-chemical (equalization, coagulation, and adsorption), advanced approaches (Fenton oxidation, ozonation, cavitation), thermo-catalytic and biological treatments available to treat TWW, and their integrative approaches were also highlighted. This review also sheds light on the most frequently applied technologies to reduce contaminant load from TWW though there are several limitations associated with it such as being ineffective for large quantities of TWW, waste generation during treatment, and high operational and maintenance (O&M) costs. It is concluded that the sustainable alternatives applied in the current TWW technologies can minimize O&M costs and recirculate the treated water in the environment. The exhaustive observations and recommendations presented in this article are helpful in the industry to manage TWW and recirculate the water in a sustainable manner. [ABSTRACT FROM AUTHOR]

In this study, the effects of the pH of tannery wastewater obtained from a local leather processing factory on the removal of COD and turbidity, and cost of theelectrocoagulation process was investigated. Studies were carried out under two different operatingconditions. The highest COD removal efficiency was obtained as 83.5% when the initial pH was set to 3, while the energy consumption at this pH was found to be 3.88 kwh m−3. In studies where pH was kept constant, the highest removal efficiency obtained was 83.33% at pH = 5. In this case, the energy consumption was determined as 2.44 kWh m−3. The total cost of the system was calculated as 1.0899 $ m−3 under controlled pH conditions and 0.8761 $ m−3with uncontrolled pH. Studies show that the COD removal kinetics are more suited to 2nd degree kinetics. The highest removal rate for uncontrolled pH was k2 = 0.0791 L g−1 min−1 at pH = 3. The highest rate for controlled pH was k2 = 0.0397 L g−1 min−1 at pH = 5. [ABSTRACT FROM AUTHOR]

In recent decades, there has been growing concern and negativity from the environmental impact of industrial development, which produces lots of technological changes. The significant contribution of the leather industry has a good impact on the economic sector; however, it is faced with challenges caused by pollution to the environment. Special attention is required for disposal of solid wastes because of the large amounts that are generated and legal restrictions. Environmental problems are caused by the large amount of wastes originating from chemicals during processing, especially in dehairing process. Conventional dehairing by lime sulfide process causes high chemical oxygen demand emission, biological oxygen demand, and total suspended solids. The dehairing mechanism is vaguely understood at present from the point of view of the enzyme specificity, which is needed for consistent and satisfactory hair removal without deleterious effect on the leather quality. It is known that the use of enzymes has potential as an alternative that can be used to reduce the harm caused by toxic chemicals including for waste management. Recently, there has been increasing research on application of enzymes in various leather production processes. The use of protease and keratinase enzymes in leather processing industry has the most promising potential to improve the surrounding environment. Therefore, this study aimed to review relevant literature in terms of dehairing processes without adverse effects in order to make good quality leather. Further scientific discussion is needed for understanding the gap of these critical issues in this area. [ABSTRACT FROM AUTHOR]

The tannery is one of the leading revenue-generating sectors in developing countries. The ever-increasing demand for leather products in the global market requires converting large amounts of rawhide/skins into resilient non-putrescible finished leather. Only 20% of the raw material is converted into a finished product; the rest 80% is discarded as solid and liquid wastes during leather processing. A heavy discharge of improperly treated solid tannery waste (STW) causes a severe impact on the surrounding environment by polluting soil, surface water, and groundwater resources, posing severe hazards to human and animal health. STW comprises proteinaceous untanned and tanned waste, which requires proper treatment for eco-friendly disposal. Several strategies have been developed over the years for the reduction and recycling of STW for producing renewable energy (biogas and biohydrogen), biofuels (biodiesel and briquettes), construction material, fertilizers, commercial products (adsorbents, animal feeds, proteins, fats, and enzymes), and biodegradable packaging and non-packaging materials. In this review, we discuss various strategies adopted for recycling, reutilization, and reduction of STW in an environment-friendly manner. Furthermore, an overview of the current perspectives toward achieving a zero-waste policy is also presented to reduce the environmental burden using green-clean technology to aid the survival of present-day tanneries. [ABSTRACT FROM AUTHOR]

With the growing environmental concern, alternative processes and products are must for sustainable development of processing industries. Leather processing industries conventionally employ sodium sulfide (Na2S) for hair loosening step, which is unsafe as it produces hydrogen suflide. Thiogycolic acid is the key component of hair treatment formulations used in cosmetics. The use of alkali salt of thioglycolic acid known as calcium thioglycolate for hair loosening has been studied in this paper as an alternative to Na2S. The spent effluent liquor of liming process was analyzed for pollution load through biochemical oxygen demand (BOD), chemical oxygen demand (COD) and total dissolved solids (TDS) analysis, which indicated significant reduction in pollution load: BOD (50%) and COD (fivefold) for calcium thioglycolate process as compared to Na2S-based control process. Physical strength characteristics such as tensile strength, tear strength, grain crack and distention have also been analyzed for both experimental and control leathers, which revealed that strength properties of processed leathers from calcium thioglycolate process were either improved or on par with control leathers, whereas the potential danger of H2S formation at work place due to the use of Na2S has been avoided. In addition, cost analysis indicates substantial reduction in pollution load and related effluent treatment costs could compensate for the higher cost of calcium thioglycolate process. [ABSTRACT FROM AUTHOR]

Leather manufacturing processes raw hides and skins into various finished leather products, generating huge amounts of untanned and untanned leather solid wastes (LSWs). The present study investigates the LSWs generation, characterization, and management practices of the Sheba leather industry in Ethiopia. Results revealed that LSWs are categorized as non-chrome solid waste, including de-dusted salt, raw trimming, hairs, fleshing waste, pickle trimming, and splitting wastes. Chrome-based wastes include chrome shaving waste, crust leather trimming waste, buffing dust waste, finished leather trimming waste, etc. Further, solid wastes were characterized for the physico-chemical parameters viz. moisture (31.5%), ash content (7.3%), pH (5.7), carbon content (14.7%), nitrogen content (0.3%), chromium content (2%), calorific value (20,107 kJ.kg-1), VOCs (75.1%) and carbon to nitrogen ratio (52:1). Results obtained suggested various sustainable technological options for the effective LSWs management to preserve environment. [ABSTRACT FROM AUTHOR]

Tanning is a processing mechanism that prevents the collagen fibers from putrefaction to maximize the hydrothermal stability of leather. Tannin agents extracted from plants were used in leather production in a process called vegetable tanning. Vegetable tanning is an eco-friendly tanning method when compared to chrome tanning. Chrome tanning is the most common method of tanning hides. Currently, chrome tanning, which is extracted from chrome ores, is used in more than 80–90% of the leather tanning industry, but the most serious environmental issue associated with tanneries is chromium. This implies that the presence of chromium both in wastewater and in leather waste has a significant environmental impact and a high cost for landfills. However, currently, vegetable tanning and other tanning materials take up a 10–20% share of the leather tanning industry. Even today, most commercial vegetable tanning is a mimosa. In this study, a new alternative material and chrome-free tanning process using the barks of the Osyris lanceolata plant barks which reduces the environmental pollution load in terms of wastewater and solid wastes would be introduced. The study also aimed to improve the extraction and optimization mechanisms of tannin material from the bark of the Osyris lanceolata plant, which grows in Dera Hamusit Woreda in Ethiopia's south Gonder Amhara region. In addition to these, the chemical and physical properties of experimentally treated leather were analyzed. This study's results show that the bark of Osyris lanceolata contains (18.72%) tannin with 96% tanning strength (96%), and 49 percent purity. Also, leather treated with this tannin showed good shrinkage temperature (84.5°C), and organoleptic properties results such as tensile strength, tear strength, and elongation were 7.1 N/mm2, 19 N, and 45%, respectively. Besides that, the FTIR analysis shows that the bark of the Osyris lanceolata plant has a phenolic compound that is used for tanning purposes. This study clearly shows that extracted tannin from Osyris lanceolata has the potential to be used as an alternative tannin material in the leather tanning industry. [ABSTRACT FROM AUTHOR]

Bio-based leather substitutes are an emerging class of ethically and environmentally responsible natural fabrics that are increasingly exceeding consumer aesthetic and functional expectations as an alternative to bovine and synthetic leathers. This literature review creates a clear and elaborative overview of conventional leather processing along with innovative potential bio-leather substitutes. Plant-driven, fungal-origin, bacterial-driven, and animal-origin bio-leathers are the current innovative research advances addressed in this literature. While traditional leather and its alternatives are sourced from animals and synthetic polymers, these renewable and sustainable leather substitutes are gained from bacterial cellulose, mycelium, plant cellulose, and animal cells using tissue engineering and other eco-friendly techniques. In conclusion, bio-based leather alternatives are eco-friendly, non-toxic, and sustainable and ultimately can substitute natural leather made by conventional processing. [ABSTRACT FROM AUTHOR]

Introducing sustainability by a reduction in chemical input has added value to technology innovations, especially in the leather fatliquoring process. Major concern of sustainable leather fatliquoring process lies in factors like usage of natural oil, avoidance of hazardous substances and reduction in organic load to the environment. Due to their special features, such as their ease of preparation and environmental friendliness, Pickering emulsions and their applications have received significant attention in recent years. The present study reports a novel sustainable leather fatliquoring process by usage of hybrid particles (alumina coated with silica) stabilised Pickering emulsions as fatliquor instead of conventional sulphated oil based fatliquor. Eco fatliquoring agent with a particular choice of vegetable oil stabilised by hybrid alumina functionalised with silica (Al-O-SiO 2)/ hybrid nanoparticles through Pickering emulsion was reported. During the post tanning process, the uses of this developed fatliquoring agent causes a reduction in the 30% of fatliquoring agent input and 40% reduction in dye input. The presence of alumina nanoparticles resulted in an immediate improvement of the abrasion resistance, softness, and physical properties of the crust leather. Utilizing hybrid particles (Al-O-Si) as a stabiliser readily improves the uptake of other post tanning chemicals. Thus, the prepared fatliquoring agent suitably softened the leather and significantly improved the mechanical properties, light fastness, and fullness with the reduction in the pollution load. To divulge the sustainability of the fatliquoring process, the sustainability analysis for the developed product was analyzed and presented. As compared to the conventional fatliquoring process the E factor of the experimental process was estimated to be lower (at a value of 0.25) which indicates minimum emissions. Based on cost estimation, leather fatliquoring is economically viable when using the prepared fatliquoring agent. [ABSTRACT FROM AUTHOR]

Subtilisins from microbial sources, especially from the Bacillaceae family, are of particular interest for biotechnological applications and serve the currently growing enzyme market as efficient and novel biocatalysts. Biotechnological applications include use in detergents, cosmetics, leather processing, wastewater treatment and pharmaceuticals. To identify a possible candidate for the enzyme market, here we cloned the gene of the subtilisin SPFA from Fictibacillus arsenicus DSM 15822T (obtained through a data mining‐based search) and expressed it in Bacillus subtilis DB104. After production and purification, the protease showed a molecular mass of 27.57 kDa and a pI of 5.8. SPFA displayed hydrolytic activity at a temperature optimum of 80 °C and a very broad pH optimum between 8.5 and 11.5, with high activity up to pH 12.5. SPFA displayed no NaCl dependence but a high NaCl tolerance, with decreasing activity up to concentrations of 5 m NaCl. The stability enhanced with increasing NaCl concentration. Based on its substrate preference for 10 synthetic peptide 4‐nitroanilide substrates with three or four amino acids and its phylogenetic classification, SPFA can be assigned to the subgroup of true subtilisins. Moreover, SPFA exhibited high tolerance to 5% (w/v) SDS and 5% H2O2 (v/v). The biochemical properties of SPFA, especially its tolerance of remarkably high pH, SDS and H2O2, suggest it has potential for biotechnological applications. [ABSTRACT FROM AUTHOR]

Leather industry produces huge amounts of solid wastes. In the last decade, several methods for the recovery and valorization of these wastes were developed, mainly focused on the extraction of collagen using chemical methods. The extracted collagen, due to its poor quality, is mostly used in agriculture as a nitrogen source ingredient of fertilizers. This study aims to apply collagen, extracted from leather tanned solid wastes using a recently reported new process based on enzymatic hydrolysis, as filling agent for low quality leather. Thanks to the enzymatic hydrolysis, collagen can be extracted without affecting its integrity and, therefore, its quality. In order to use the extracted collagen as filler for low quality leather, an enzymatic mediated cross-linking reaction between collagen and casein was developed. The enzymatic cross-linking reaction was added as an additional phase of the re-tanning process or as a replacement of one of the re-tanning steps. To evaluate the filling effect, thickness of the treated leather was measured and infrared and microscopy analyses were performed, comparing the new methods to the traditional standard one. The mechanical properties of the filled leather were tested and the sensorial features, such as fullness and touch feelings, were estimated through a panel test. Results suggest the high potential of extracted collagen to be employed back in leather processing both as additive and as substitutive filler. [ABSTRACT FROM AUTHOR]

Subtilisins from microbial sources, especially from the Bacillaceae family, are of particular interest for biotechnological applications and serve the currently growing enzyme market as efficient and novel biocatalysts. Biotechnological applications include use in detergents, cosmetics, leather processing, wastewater treatment and pharmaceuticals. To identify a possible candidate for the enzyme market, here we cloned the gene of the subtilisin SPFA from Fictibacillus arsenicus DSM 15822T (obtained through a data mining‐based search) and expressed it in Bacillus subtilis DB104. After production and purification, the protease showed a molecular mass of 27.57 kDa and a pI of 5.8. SPFA displayed hydrolytic activity at a temperature optimum of 80 °C and a very broad pH optimum between 8.5 and 11.5, with high activity up to pH 12.5. SPFA displayed no NaCl dependence but a high NaCl tolerance, with decreasing activity up to concentrations of 5 m NaCl. The stability enhanced with increasing NaCl concentration. Based on its substrate preference for 10 synthetic peptide 4‐nitroanilide substrates with three or four amino acids and its phylogenetic classification, SPFA can be assigned to the subgroup of true subtilisins. Moreover, SPFA exhibited high tolerance to 5% (w/v) SDS and 5% H2O2 (v/v). The biochemical properties of SPFA, especially its tolerance of remarkably high pH, SDS and H2O2, suggest it has potential for biotechnological applications. [ABSTRACT FROM AUTHOR]

Leather is made of collagen protein polymer, which is used in the manufacture of a variety of products including footwear, automotive upholstery, garments, and sports equipment. Animal skins/hides are converted into leather using a series of chemical processes. Of them, the tanning process is the most important chemical process that converts animal skins into leather by stabilising collagen fibre so that they do not putrefy. However, it is a hazardous process because of the use of various toxic chemicals in tanning, re-tanning and fatliquoring treatments producing toxic effluent. Over the years many tanning treatments based on chromium sulphate, and vegetable and synthetic tannins in combination with heavy metals, have been developed but tanning with chromium sulphate (known as Cr-tanning) is still the most effective, cheap, and widely used tanning process in the leather industry. Although the development of various improved Cr-tanning methods highly reduced the chemical and water consumption in leather tanning, it is still under scrutiny because of the production of effluent containing a harmful level of Cr and there is strong evidence that when the treated leather is disposed into the environment, part of the released trivalent chromium is converted into carcinogenic hexavalent chromium. Many sustainable alternatives to Cr-tanning based on chemical and enzymatic crosslinking, various bio-derived polymers, enzymes, modified zeolites, and nanostructured materials have been developed over the years with limited success. The alternative methods are either not as effective as Cr-tanning, affect the dyeability and other functional and organoleptic properties of leather, and or are cost-prohibitive. In this comprehensive review article, various tanning methods used in industry or studied in the laboratory are critically reviewed, and their advantages and disadvantages are outlined. The consumption of tanning agents, total chemicals including various auxiliaries and fatliquoring agents, and water in tanning, and the tanning performance and mechanical properties of the processed leather are compiled and compared. The reaction mechanisms of novel tanning agents with leather collagens and the future directions to make leather tanning more sustainable are outlined. This review article will be a guide for academicians/researchers/manufacturers involved in leather processing to develop more sustainable leather materials. [ABSTRACT FROM AUTHOR]

Collagenolytic proteases (collagenases) can be used in a variety of areas of human life: processing of leather, production of detergents, and food and beverage preparation, as well as pharmaceuticals and medicine. The aim of this study was to develop methods for the preparation and characterization of collagenolytic proteinase from the filamentous fungus Aspergillus fumigatus. A method for preparing A. fumigatus extracellular collagenolytic proteinase by two-stage chromatographic purification was developed. Analysis of the physicochemical and biochemical properties of the enzyme confirmed that a serine-type proteinase with a molecular weight of 40 kDa and maximum activity at 40°C, pH 7.5, was synthesized. The data obtained here suggest that A. fumigatus proteinase can be regarded as a basis for obtaining new drugs with collagenolytic effects. [ABSTRACT FROM AUTHOR]

Natural leather is a durable and flexible material processed from the hides and skins of animals by tanning. The individual features and the composition of each animal's hides and skin contribute to determine the chemico‐physical and mechanical properties of the obtained natural leather. Deep knowledge of such properties is required to select a suitable application field for the produced leather as well as for the development of new performant synthetic leather. In the present work, the chemical structure of sheep leather used as a model is studied by attenuated total reflection Fourier‐transform infrared (ATR‐FTIR) spectroscopy. Moreover, some chemico‐physical properties, as well as microbiological properties and tensile strength, are determined. [ABSTRACT FROM AUTHOR]

Plankton communities are very important for the functioning of aquatic ecosystems [1, 2]. Phytoplankton is the dominant primary producer in the aquatic environment, from which most food webs begin, and which produces oxygen necessary for aquatic organisms [3]. Indicators of phytoplankton development are used to assess the ecological state of water bodies [4]. By quickly responding to changes in the aquatic environment, phytoplankton can serve as an indicator of the state of the entire ecosystem. Objective—A comparative analysis of the state of phytoplankton in two lakes experiencing anthropogenic pressure and located on the island territory of the Solovetsky archipelago and on the mainland of the Arkhangelsk oblast in the Northern Dvina River basin. Lake Bannoe (Gagarye) is located on the territory of Solovetsky village. Previously, a leather processing plant and a bathing facility of the monastery were located on its shore. Now there are buildings of the Solovetsky branch of the Arkhangelsk experimental algae plant. Lake Kholmovskoye is located in the Primorsky district of the Arkhangelsk oblast, 18 km from the city of Arkhangelsk. On the western shore of the lake is the village of Kholm and summer cottages. From the side of Lake Kholmovskoye, the village of Kholm is surrounded by an artificially dug ditch, into which all household drains flow. On the northern shore are former household premises. An operating cage trout farm is located in the water area of the lake, which is a source of additional organic matter entering the lake waters. [ABSTRACT FROM AUTHOR]

Leather processing generates a huge amount of chromium (Cr) containing wastes, and one of them is chrome shavings (CS), which frequently end up in landfills. It may be harmful to the environment and human health due to the oxidation of Cr(III) to poisonous Cr(VI). Herein, CS and polyvinyl alcohol (PVA) are used for the preparation of flexible CS-PVA composite sheets, using CS as a skeletal and PVA as a cross-linker by a simple and facile technique. CS-PVA composite sheets are characterized by FT-IR, SEM, STA, and UTM. FT-IR analysis of CS-PVA composite sheets indicated the existence of dominating peaks corresponding to collagen amide bands as well as PVA characteristic bands, and it demonstrates the uniformity of the developed composite sheets. When the amount of PVA is increased, the tensile strength of CS-PVA composite sheets increases from 0.21 to 4.17 N/mm2. With increasing of the amount of PVA, the softness decreases from 6.47 to 3.7 mm, and SEM shows decreasing of pores in the composite sheet. The addition of more PVA makes CS-PVA composite sheets more thermally stable. This facile method of preparing CS-PVA composite sheet is low-cost and eco-friendly, having potential applications in various fields, including clothing, leather goods, decoration, packaging, and footwear products, as well as presenting promising platforms for effective utilization of industrial waste materials. [ABSTRACT FROM AUTHOR]

The paper features the rawhide collagen defibrillization process in the elastic leather materials manufacturing. Optimal colloid-chemical properties of semi-processed products were defined by way of using mathematical optimization of rowhide liming process. It was found that during the alkaline treatment of raw material (in the operating temperature range) the degree of defibrillation of raw material raises (in proportion to the derm collagen swelling) with increase in the ratio of process solution to the mass of raw material, and the extremum of hydrothermal stability and leather yield can be estimated. It was also shown that the degree of swelling decreases with a decreasing ratio of sodium sulphide and sodium hydrosulphide, and the leather area yield reaches the maximum value at the equal proportion of these reagents. Multicriteria optimization of rawhide liming process using the Harrington's desirability function was carried out. The developed technology of soaking and liming was tested under production conditions. The above-mentioned low-waste technology provides elastic leather materials with a yield increase by 3.5%, which meet the industry standards requirements. [ABSTRACT FROM AUTHOR]

The study applies Kansei engineering in analyzing the color and texture of leather footwear, utilizing neural network verification to mirror consumers' visual and tactile imageries onto varieties of leather. This aids in the development of an advanced system for selecting leather footwear based on such impressions. Initially, representative word pairs denoting consumers' visual and tactile perceptions of leather footwear were delineated. Post-evaluation of these perceptions through a sensibility assessment questionnaire was administered, using 54 samples of leather footwear provided by manufacturers, with each leather type codified in terms of visual and tactile sensibilities. Subsequently, a customized software algorithm was crafted to isolate the primary color and adhesiveness as color features from the leather sample images. Analyzing grayscale values of the images and using pixel neighborhood as a base, the associated calculation methods, such as LBP, SCOV, VAR, SAC, etc., were proposed to extract texture features from the images. The derived color and texture feature values were used as the input layer and the sensory vocabulary quantified values as the output layer. Backpropagation neural network training was conducted on 49 leather samples, with five leather samples used for testing, culminating in the verification of neural network training for three types and 17 combinations. The outcome was an optimal method for leather footwear Kansei engineering and neural network training, establishing a design process for leather footwear characteristics assisted by sensory vocabulary and a backpropagation neural network. Additionally, a computer-aided system for selecting leather footwear, based on these impressions, was designed and validated through footwear design. This study utilized symmetry in footwear design. By using the design of a single shoe to represent the imagery of a pair of symmetrical shoes, we verified whether the leather samples recommended by the leather imagery selection query system met the expected system input settings. [ABSTRACT FROM AUTHOR]

Microalgae have been effectively used as a nutrient removal method in wastewater treatment. However, the harvesting microalgae step is a major hurdle to the industry. In this study, the silica non-toxic sol–gel is used as a matrix to immobilise microalgae. Non-toxic silica gel matrix was synthesised by tetraethoxysilane (TEOS) derived alcohol free route. This study aims to evaluate the effect of microalgae immobilisation in non-toxic silica gel to remove tanneries wastewater pollutants. The experiments were conducted by applying immobilised Scenedesmus sp. and Chlorella sp. in three concentrations in leather processing wastewater during 72 h of cultivation. The morphology of immobilisation was evaluated by optical microscopy, SEM and Zeta Potential analysis. The rate removals of total nitrogen (TN), total organic carbon (TOC) and Inorganic Carbon (IC) in comparison to immobilised and suspended microalgae were evaluated by the influence of the immobilisation, type of microalgae and microalgae concentration. For both microalgae, immobilisation showed promise for removing these nutrients. The immobilised Chlorella sp. at the initial concentration of 5.84 ± 0.975 mg.L−1 (I-Ch2) had the highest removal by immobilised microalgae, with an uptake of 20.82% of AN, 18.44% of TN, 30.42% of TOC and 64.73% of IC. [ABSTRACT FROM AUTHOR]

Collagen-based composite materials are extensively studied and used in different fields, including tissue engineering, food applications and leather manufacture. Leather is the largest application of collagen where typical tanning chemistries include metal salts, polyphenolics and aldehydes. A new type of material that is gaining industrial significance is based on a composite of collagen and zeolite in the area of sustainable leather manufacture. This approach utilises simple, abundant, and benign chemistry, which provides leather with the physical properties needed for a range of possible applications. However, the stabilising interactions between collagen and zeolite are not yet known and would benefit from deeper understanding of the interactions and the impact on environmental parameters. The composite material reported here is made by treating animal hide collagen with zeolite using established processing technologies, commonly used in leather tanning processes, without the need for further specialised apparatus. The interaction between collagen and zeolite has been characterised by small-angle X-ray scattering (SAXS), infrared spectroscopy (IR), solid-state nuclear magnetic resonance spectroscopy (NMR), scanning electron microscopy (SEM) and zeta potential. SAXS shows unique changes in the scattering profile revealing zeolite and collagen interactions, which relate to a combination of covalent and electrostatic mechanisms. The zeolite forms a 3D network structure covering collagen fibres, improving protein stability against hydrothermal denaturation and creating material strength. The environmental and industrial impact has been evaluated based on reaction uptake, waste stream assessment and biodegradability. Zeolite tanning shows a positive influence on reaction uptakes, similar to industry best practice, waste water impact and positive biodegradability results. Through the deeper understanding of the van der Waals interactions between collagen and zeolite, and the positive environmental assessment, this work demonstrates the merits of this new stabilisation approach with the possibility of further expansion into other applications. [ABSTRACT FROM AUTHOR]

• Leather shavings do not allow for autothermal combustion when combusted directly. • Adding wood biomass to tannery waste results in a complete combustion of such mixture. • Lower quality pellets combustion results in a prominent afterburn. • Large percentage of additive leads to ash sintering, smaller additions result in fine ash. • The ash from wet blue tannery waste combustion traps large amounts of Cr 2 O 3. Leather processing companies are struggling with the problem of increasing costs of post-production waste disposal. Therefore, the issue of thermal waste disposal at the plant and the use of generated heat in the production process is becoming more and more popular. Leather waste on its own does not allow for autothermal combustion despite the sufficient higher heating value (HHV). Therefore the Authors proposed to improve the flammability of the fuel by adding a small amount of wood sawdust to leather waste and produce premixed pellets. Six such samples were incinerated in a laboratory-scale reactor, which enables the simultaneous measurement of characteristic temperatures, exhaust gas analysis and sample mass loss rate. Research has shown that even a small addition of sawdust enables a stable combustion process and does not cause the formation of sinters. In addition, studies of the ash showed that in the case of chromium-containing waste, a large part of it remained in the ash in the form of Cr 2 O 3. Nevertheless, very fine ash causes the small fraction chromium to be carried with the flue gas stream, therefore controlled agglomeration of the ash structure would be advisable in the final installation. Emission analysis showed high and moderately high NO x and SO 2 emissions, decreasing with the increase in the amount of sawdust addition in the sample. Research has shown that leather waste is not a burden, but can be an attractive and safe source of energy for the company, while improving waste management in a circular economy. [ABSTRACT FROM AUTHOR]

This study intends to identify, analyse, and evaluate sustainability assessment (SA) methods, along with the critical factors of sustainable manufacturing (SM) practice. Based on the opinion of experts and a literature review, 10 SA methods and 20 critical factors of SM practice were identified and analysed in relation to their optimal selection in sustainable operations. This research uses a fuzzy MULTIMOORA (Multi-Objective Optimisation on the basis of a Ratio Analysis plus the full multiplicative form) to rank SA methods based on the weights of the critical factors of SM practice obtained using a fuzzy analytic hierarchy process (AHP). A case study of the leather processing industry in India describes the use of the technique in practice. The ranks obtained using the AHP-fuzzy MULTIMOORA is compared with those obtained using the best–worst method (BWM)-fuzzy MULTIMOORA. The results reveal that the Index of Social Progress and the Social Life Cycle Assessment are the top two reliable SA methods based on the identified critical factors of SM practice. Among the critical factors, the 'identification of alternative raw materials', 'methane mitigation', and 'opting for re-utilisation' are identified as the prominent critical factors of SM practices. In addition to the critical factors of SM, this study also evaluates SA methods as they help to monitor industrial progress towards sustainability. These findings provide useful insights to practitioners and can help them select optimal and robust SA methods. [ABSTRACT FROM AUTHOR]

During the leather tanning process, chromium (Cr) can interact with different macromolecular organics to generate mixed ligand complexes. The removal of organochromium complexes is one of the main difficulties in the treatment of tannery wastewater. In this study, a gelatin-gallic ac-id-Cr(III) (G-GA-Cr) mixed ligand complex was used to examine the effects of ultrasonic on chromium destabilization and removal from the dissolved complexes. To investigate organic destruction and chromium liberation, alkali precipitation or chelating precipitation assisted with ultrasound were conducted, respectively. The findings demonstrate that ultrasonic-assisted alkali precipitation and chelating precipitation, respectively, removed over 50% and 93% of Cr from the complexes. According to the data, ultrasonication weakened the bonds that bound macromolecular ligands together, and depolymerization took place to the point where Cr could interact directly with hydroxide ions or chelating agents. In addition, by applying ultrasonic-assisted chelating precipitation, the chromium concentration could meet the discharge standard and the amount of precipitation was also noticeably decreased. [ABSTRACT FROM AUTHOR]