Vegetable Tanning Process Research Articles

Improving vegetable tannins chemistry: A remarkable advancement in salt-free high tannin fixation

Traditional tanning practices often result in harmful waste products that pose significant environmental risks, including water pollution, non-biodegradable solids, hazardous emissions, and unpleasant odors. However, this study introduces a simple and effective alternative method for industrial-scale vegetable tanning, with the goal of minimizing environmental pollution. This innovative method eliminates the use of common salt and substantially reduces water consumption. The environmental benefits of this new approach are remarkable. It has led to a significant 70% reduction in water usage, a 25% decrease in energy consumption, and complete elimination of chloride discharge. These changes have also contributed to a notable reduction of 60-70% in tanning and treatment expenses. Furthermore, the leathers produced using this method exhibit comparable physical, chemical, and sensory properties to those produced through conventional tanning practices. This eco-friendly approach not only addresses environmental concerns but also offers economic advantages, making it a sustainable choice for vegetable tanning processes.

Utilization of vegetable tannins for stabilization of collagen fibers by using supported process enzyme

Tanning is the process of treating animal skins or hides to produce leather, which is more durable and less susceptible to decomposition. The leather industry has been pushed to develop tanning systems that utilize natural products due to environmental concerns. Vegetable tanning is one of the oldest methods, but its usage is limited due to the high organic load in the effluent generated. This load is difficult to degrade and results in high biological and chemical oxygen demand. This study aimed to develop an eco-friendly tanning process for protein fibers using proteolytic enzymes. The goal was to improve the exhaustion of vegetable tannins by increasing their uptake during the tanning process. The optimized experimental process, which involved enzymatic treatment of protein fibers, resulted in an exhaustion of 97% compared to 83% in conventional vegetable tanning processes. Enzyme treatment before tanning also led to a slight improvement in hydrothermal stability, as well as slightly better physical properties of the resulting leathers compared to conventionally tanned leathers. The enzymatic process has the added benefit of reducing total solids (TS) and chemical oxygen demand (COD) loads in the identified streams by 80% and 33%, respectively.

Novel Vegetable Tanning Techniques by Notholithocarpus densiflorus Extract and Fatliquoring with Indigenous Bovine Fat

The major technical challenge of vegetable tanning is to improve the higher wear-comfort, leather strength and water resistance efficiency in daily necessities of leather products, aiming as an alternative to chrome tanning. The demonstration has been made by indigenous bovine fat and Tanoak tree (Notholithocarpus densiflorus) bark-wood extract for usage in the tanning process as a new kind of stuffing tanning technique for the first time. The tannin content maximum efficiency was found at 34.25% for the bark and 28.5% for the wood sample. The presence of tanning content was characterized by using UV-visible absorption spectroscopy, FTIR spectroscopy and HPLC techniques. The characterization data revealed mainly catechol presence in the bark and pyrogallol presence in the wood. The stuffing techniques tanned leather showed a shrinkage temperature of 95±2 °C. Other physical properties such as tensile strength, tear strength, grain cracking load, and flexing endurance were comparable to conventional chrome-tanned leather. The cross-sectional morphology and thermal degradation of the tanned leathers were characterized by FE-SEM and TGA techniques which revealed a fat-coated compact structure of the leather fibres and decomposition at mainly 100 °C to 300 °C respectively. The average contact angle of a water droplet on bark-tanned leather was greater than 100° and wood-tanned 88° at the solid-liquid interface respectively, which indicated the low wettability of leather as a water resistance leather. These new kinds of stuffing techniques of vegetable tanning processes will help to replace the chromium tanning, sustainable tanning approach and save the environment.

Citric Acid as an Effective and Safe Fixing Agent in Vegetable Tanning Process of Goatskin

Formic acid is known as a fixing agent in vegetable tanning process but this material is corrosive and irritant. Citric acid has the potential to be developed as an alternative fixing agent. This research aims to study the ability of citric acid as an alternative fixing agent in the tanning process, especially vegetable tanning of goatskin. The tanning process was carried out by the drum method. Pickled goatskins were tanned with mimosa and then fixed with citric acid. The concentration of citric acid varied from 1%; 1.5%; 2%; 2.5%; to 3%, to determine the optimum concentration. A fixing agent of 2% formic acid was used as a control. The results show that the control skin had similar characteristics to the treated skin. Physical properties of T4 have met the standard of SNI 0253-2009. It can be concluded that the optimal concentration of citric acid that can be used as an alternative fixing agent in vegetable tanning process of goatskin is 2.5%.

Remediation of Spent Vegetable Tannins from Waste Tanning Liquor through Coagulation and Ultrasound Pre-Treatment

Vegetable tanning is one of the oldest methods of tanning. Vegetable tannins present in spent tanning liquor necessitates suitable remediation measures for sustainable solution. Vegetable tanning agent, wattle extract powder and vegetable tanning process spent liquor collected from a commercial tannery were used for the experiments. In the present approach, natural clay has been employed for the coagulation of spent vegetable tannins. Various other suitable precipitating agents such as zinc chloride (ZnCl2), barium chloride (BaCl2), ferric alum, lime and poly-electrolyte have also been studied for their efficacy in the treatment process and their requirement optimized. The efficacy of coagulation was monitored through settling characteristics of precipitation process and % settled volume for a given time. In the case of wattle powder, better settling of tannins was obtained due to combined use of optimized amount of clay and ZnCl2. Whereas, ultrasound pre-treatment provided further enhancement. In the case of spent tannery vegetable tanning liquor, ultrasound pre-treatment of polyelectrolyte along with optimized amount of normal lime, clay and ferric alum provided rapid settling behavior, with steady state achieved in 20 minutes with settled volume of ~10 ml. Similar trend was also achieved (10 ml, 8 min.) for ultrasound pre-treated optimized clay with the use of other agents as normal. There was a significant reduction in particle size of clay (from 539 nm to 298 nm) through ultrasound pre-treatment (20 min.), leading to more surface area facilitating the coagulation process. This method could be useful for remediation of vegetable tannins present in spent vegetable tanning liquors using available natural material clay and shall also be extended to other streams. The present study has explored the ultrasound assisted coagulation science and technology for remediation of wastewater in general, whereas, spent vegetable tanning liquor in specific.

Life Cycle Assessment of a Local Tannery in Southern Italy. A Chrome and Vegetable Tanning Processes Evaluation

Life Cycle Assessment of a Local Tannery in Southern Italy. A Chrome and Vegetable Tanning Processes Evaluation

Studies on the Effect of Bacterial Tannase Supplementation to Biodegradation of Tannins in Tannery Wastewater

Tannins present in the vegetable tanning process wastewater (VTW) affect the aerobic microbes and reduce the treatment efficiency in the tannery effluent treatment plants. Studies were performed wi...

Analysis of the environmental impacts of waterproofing versus conventional vegetable tanning process - A life cycle analysis study

Waterproofed vegetable leather is desired for its “greenness” in front of chromium-tanned waterproofed leather. However, conferring waterproofing capabilities to vegetable tanned leather maintaining light color and a soft touch is a fact of great concern for leather goods producers. Sustainable and technical requirements are currently demanded by high-quality brands in order to pass the threshold established by Leather Working Group (LWG) initiatives to earn their environmental audit seal. The research work has focused on testing various mineral salts and hydrophobic products compatible with vegetable tanned leather. According to the obtained results, acrylic copolymers along with zirconium salts are necessary to achieve the desired leather properties. The present study provides the environmental comparison of a new vegetable tanning process to give waterproofing capabilities with the conventional vegetable tanning process. The comparison comprises both wastewater analysis and environmental impacts in a life cycle assessment (LCA) framework. The paper also outlines the comparison using different life cycle impact assessment (LCIA) methods. Further, the study provides specific data on leather vegetable tanning processes. Comparative analysis has been focused on the two diverging stages for both conventional and waterproofing vegetable tanning processes, namely retanning and fatliquoring. Conventional process environmental impacts are lower than waterproofing process impacts according to LCA methodology. However, wastewater analysis shows no major differences between both processes. Main contributors to these results are the zirconium salts, dispersing agents and acrylic copolymers used along with an increase in energy consumption due to processing times. Alternative methods used in the impact assessment lead to similar results, revealing no major differences in the comparative results between methods in this case.

Nutrient requirement of tannery wastewater containing tannins

Biological wastewater treatment methods are extensively used in the treatment of industrial effluents among which Activated Sludge Process (ASP) holds a prominent position. To carry out the degradation of organic matter, the micro-organisms present in the activated sludge need sufficient amount of nutrients and oxygen in the aerobic treatment process. Hence, this study was undertaken to assess and optimize the nutrient requirement in the treatment of vegetable tanning process wastewater (VTW) generated from tanneries. The characterization of VTW revealed that the observed Biochemical Oxygen Demand (BOD):Nitrogen (N):Phosphorus (P) ratio of VTW was 100:1.42:0.07, which is deficient in both N and P. Aerobic reactor study was conducted with BOD:N:P ratio of 100:1.42:0.07, 100:5:0.1, 100:5:1, 100:5:3 and 100:5:5 separately. For N:P of 5:0.1, removal efficiencies of BOD 5 , COD and tannin were 49.0 %, 37.3 % and 30.2 %, respectively, whereas, for N:P of 5:3, BOD 5 ,COD and tannin removal efficiency was 59.7 %, 50.9 % and 38.0 %, respectively. However, further increasing the N:P ratio to 5:5, BOD 5 ,COD and tannin removal efficiencies were 60.9 %, 51.2 % and 38.7 %, respectively. It was observed from the results that for N:P ratio of 5:3 to 5:5, the improvement in removal efficiencies was marginal. Hence, BOD:N:P ratio of 100:5:3 was considered as optimum Respirometry study revealed that oxygen uptake was 62.5 mg O 2 during the 24 h and 18 % of MLSS growth was observed. From modified Stover–Kincannon model the kinetic constants U max of 3.74 g/L day and K B of 54.08 g/L.d were arrived at; The k value was obtained from first order and zero order equation was 16.95 mg/L h −1 and 0.026 h −1 , respectively for tannin as substrate for the optimized ratio BOD:N:P ratio of 100:5:3. This study emphasizes that proper balance of N and P is needed for synthesis of sufficient biomass for degradation in biological treatment.

Prospects and Challenges of Chrome Tanning: Approach a Greener Technology in Leather Industry

The leather industry is one of the heavy-polluting and hazardous industries that is creating toxic and harmful effects on the environment and human health by producing waste chemicals, tannery effluents, and various pollutants. Moreover, Tanning is the required stage to convert raw skin to durable and sustainable skin but most of the chemicals, salts, organic and inorganic toxic pollutants are produced. In commercial practices, Chrome tanning is the highly employed approach that uses a large number of basic chromium salts that becomes the major source of chromium pollutant in the environment. Chromium salt is not only harmful to the environment and ecology but also harms the human body such as causing respiratory problems, infertility and birth defects, skin and lung cancer of the workers. This article has presented two alternatives eco-friendly greener approaches of chrome tanning and waste management technique to reduce the toxic effect on the environment and human health. Firstly, to get rid of these harmful effects, the possible remedy of environmental and human health problems may be considered the vegetable tanning process. Vegetable tanning uses tannins (a class of polyphenol astringent chemicals), which occur naturally in the bark and leaves of many plants. Secondly, chrome tanning associate with ultrasound having a frequency range of 20–100 kHz is commonly employed for enhancing the physical processes and for performing chemical reactions. The basic principle associated with the process is an ultrasonic cavitation in dissolved media. Ultrasound decreases the consumption of conventional water and chemicals because it can also function as a physical activator resulting reduction in environmental pollution which is a prime concern nowadays to approach greener leather technology and eco-friendly leather processing. Furthermore, the possible waste management technique of chrome tanning helps to prevent pollution and ensure eco-friendly green technology of leather processing. Therefore, vegetable tanning and chrome tanning associated with ultrasound having proper waste management will be the viable and sustainable options for the tanners in the forthcoming future.

Evaluation of the aerobic and anaerobic degradation of an industrial effluent from vegetable tannery processing of leather on batch reactors

<p>In this study, the aerobic and anaerobic biodegradability of the industrial wastewater from the vegetable tanning process were evaluated. Water from a food wastewater treatment system was used as seed inoculum for the aerobic process and mature granular methanogenic sludge from a brewery industrial wastewater plant was used for the anaerobic process. The water from the tanning industry had a biological to chemical oxygen demand ratio of 33% with values of total chemical oxygen demand (COD) in the range of 342000 mg O2/L and total dissolved solids of 506595 mg/L. The assay of the tannery effluent under aerobic conditions resulted in a decrease of COD of 39.2% and a degradation of tannins lower than 12% after 26 days, while the anaerobic degradation showed a COD reduction of 65% with a 39% of degradation of tannins. The production of methane and Volatile Fatty Acids, during the anaerobic treatment, suggests a potential adaptation of biological organisms present in the mature anaerobic granular methanogenic sludge.</p>

Respirometric assessment of vegetable tanning process wastewater generated from tanneries

AbstractRegistration, Evaluation, and Authorization of CHemicals (REACH) regulations insist on ready biodegradability information for organic chemicals that are used on a large scale in industries. Leather industry being one such, involves addition of organic chemicals that are obtained from plant extracts for vegetable tanning process. In view of the fact that biodegradability assessment is of paramount importance now for industrial wastewaters, a study was conducted on vegetable tanning process wastewater generated from tanneries. As per the Organization for Economic Cooperation and Development (OECD) methods for ready biodegradability (301 C), respirometer studies were conducted on wastewater containing different tannin concentrations of 540 mg/L (T1), 900 mg/L (T2), and 1350 mg/L (T3). The oxygen uptake rate had shown a sharp initial peak at 74, 102, and 164 mg O2/d for the three samples T1, T2, and T3, respectively. The primary degradation % of tannins was found to be 78%, 50%, and 14% for T1, T2, and T3 respectively. The Chemical Oxygen Demand and Biochemical Oxygen Demand removal efficiency also decreased with increase in tannin concentration. The t1/2 values of tannin, calculated using the first‐order kinetic equation, was 8.8, 10.9, and 12.4 days and the experimentally observed t1/2 values were 9.8, 11.5, and 12.6 days for T1, T2, and T3 respectively. This study establishes that presence of tannins in the aerobic treatment significantly affect the oxygen uptake when the tannin concentration is increased. This study emphasizes that ready biodegradability assessment is essential to establish biodegradability of all the organic chemicals used during leather making process.

Studies on the effect of pre-treatment of vegetable tanning process wastewater prior to biological treatment

Abstract Vegetable tanning process is carried out by the tanning industry for making of thick leathers used in shoes, suitcases and wallets. The vegetable tanning process wastewater (VTW) contains tannins which are polyphenolic and recalcitrant. The present study was focused on Fenton’s oxidation (FO), ozonation (OZ) and Fenton’s oxidation followed by ozonation (FO + OZ) processes as pre-treatment for VTW. The optimized H2O2/COD ratio for FO was found to be 1.25 and the ozonation contact time was optimized as 30 min. The maximum removal of tannins observed for each pre-treatment was found to be 49.5 %, 27 % and 74.6 % for FO, OZ and FO + OZ, respectively. Fourier Transform – Infra Red (FT-IR) Spectroscopy and Electro Spray Ionization – Mass spectroscopy (ESI-MS) analysis were performed to confirm the breakdown of tannins after each pre-treatment. After pre-treatment, the samples were subjected to aerobic treatment and the process efficiency was evaluated in terms of Chemical Oxygen Demand (COD) and Biochemical Oxygen Demand (BOD5) removal. The effect of pre-treatment prior to biological treatment was assessed with the help of Monod kinetics. The kinetic parameters and the cost estimates for each pre-treatment were explained in detail in the manuscript.

Comparison of the Sustainability of the Vegetable, Wet-White and Chromium Tanning Processes through the Life Cycle Analysis

Public concerns about the quality of life of human beings as well as the quality of natural environments and ecosystems have led to the increasing importance of sustainability for governments and for all industries, including the leather industry. In this context, more "ecological" leather goods are being demanded. It should be noted that this concept is often used without a scientific study to support it. 
 This concept of sustainable or ecological product in the field of leather goods, are mainly associated with chrome-free tanneries (that is vegetable and wet-white), but this association should be backed up or dismissed by scientific evidence. A complete scientific study is required, which takes into account the different stages of leather production, including also the treatment of water and by-products, analyzing in a scientific and systematic way the environmental impact of each of these tanning processes. 
 This study focuses on the life cycle analysis of the three basic tanning processes: chrome, vegetable and wet-white leather production. It will focus on European manufacturing to have reliable data and reduce uncertainty. 
 In the tanning stage, the process with the greatest impact is the vegetable one, to highlight its high impact on global warming at 100 years (GWP100). This result is due to the energy necessary for the production of mimosa and quebracho in addition to the energy for the processing of the leather in the drums. 
 Wet white tanning with glutaraldehyde has lowest environmental results than vegetable tanning. 
 The chrome tanning process (wet blue) also stands out for its reduced environmental impact. 
 Subsequently, to have a global view of the entire production, the LCA of the post-tanning stages must be performed to evaluate the impact of each of the systems studied.

The effect of alum addition on shrinkage temperature, chemical properties, and morphology in the manufacture of vegetable-tanned leather

Vegetable-tanned leather has several disadvantages, which one of them is low thermal stability due to insufficient cross-linking with the collagen. The addition of aluminum sulfate in the vegetable tanning process will strengthen the cross-linking between the polyphenol and collagen, as well as forms the matrix in collagen. Thus, it will improve the thermal stability. The research aimed to figure out the addition of mimosa and aluminum sulfate on the shrinkage temperature, chemical properties, and morphology of leather. The research was conducted by using a variation of mimosa concentration (15%, 20%, 25% w/w) and aluminium sulfate concentration (3%, 6%, 9% w/w). The results showed that the treatment influenced the chemical properties and shrinkage temperature. The optimum treatment was the addition of 9% (w/w) aluminium sulfate to 25% mimosa which resulted to shrinkage temperature of 99,33° (rise 18,34%); nitrogen content (8,00 ± 0,0141)%; raw skins substance content (44,46 ± 0,0778)%; tannin bound content (28,29 ± 0,0424)% and the degree of tannage (62,93 ± 0,0141)%. Based on the SEM image, the addition of aluminum sulfate after mimosa has made the collagen fiber structure to be dense, which indicates the improvement of the cross-linking between the polyphenol and collagen.

Evaluation of 2-week repeated oral dose toxicity study of Mantidis ootheca water extract in mice

Most of the traditional tanning processes do generate wastes. These impact the environment in various forms including residual water with harmful pollutants, non-degradable solids as well as hazardous emissions and unpleasant odours. The present study examines an easy alternative method to the traditional vegetable tanning process at an industrial level to minimize pollutants. The new method is based on tanning eliminating common salt and significant reduction in water input. The advantages from the environmental point of view for the new method are substantial. There is 75% reduction in water input, 25% energy consumption reduction and 100% reduction in chloride discharge when the new method is adopted. The properties of leathers produced by the new process have comparable physical, chemical and organoleptic properties.

Evaluation and kinetic study on enzyme supplementation to biological treatment of vegetable tanning process wastewater

Vegetable tannins bind to the collagen of raw hides/skins and transform them into leather. The polyphenolic nature of tannin makes it inhibitory to the microorganisms and hinders the biodegradation process. Studies were carried out by external supplementation of tannase enzyme to enhance the biodegradability of tannins present in vegetable tanning process wastewater (VTW). Aerobic treatment studies were carried out for (1) VTW alone and (2) by external supplementation of tannase enzyme to VTW. The performance of the treatment process was assessed for biochemical oxygen demand (BOD5), chemical oxygen demand (COD) and tannin removal efficiencies, separately. The results indicated that the removal efficiencies of COD, BOD5 and tannin were 27%, 39% and 34.1%, respectively, for VTW alone and 51.4%, 63% and 57%, in case of tannase enzyme-supplemented VTW, for the same residence time of 24 h. Pyrogallol, which is a breakdown product of tannic acid, was found to be 324 mg/L in enzyme-supplemented reactor and 97 mg/L in reactor without tannase enzyme supplementation. Based on the experimental studies, biodegradation kinetic coefficients were derived. In the aerobic treatment process for the tannase enzyme-supplemented VTW, the values derived for maximum specific growth rate (µm), yield coefficient (Y), decay coefficient (Kd), Monod half-saturation constant (Ks) and substrate inhibition constant (Ki) were 0.068 h−1, 0.436, 0.015 h−1, 345 mg/L and 46 mg/L, respectively. The role of tannase enzyme supplementation in enhanced removal of tannin content during the aerobic treatment process was confirmed by FTIR and GC–MS analysis.

Salinity free high tannin fixation vegetable tanning: Commercial success through new approach

Most of the traditional tanning processes do generate wastes. These impact the environment in various forms including residual water with harmful pollutants, non-degradable solids as well as hazardous emissions and unpleasant odours. The present study examines an easy alternative method to the traditional vegetable tanning process at an industrial level to minimize pollutants. The new method is based on tanning eliminating common salt and significant reduction in water input. The advantages from the environmental point of view for the new method are substantial. There is 75% reduction in water input, 25% energy consumption reduction and 100% reduction in chloride discharge when the new method is adopted. The properties of leathers produced by the new process have comparable physical, chemical and organoleptic properties.

Comparison of polyflavonoids in bayberry tanning effluent and commercial bayberry tannin: prerequisite information for vegetable tanning effluent recycling

Recycling system is capable to minimize the serious environmental issues in leather making. It also has the advantage of reducing chemical consumption and providing an efficient way to decrease the cost of leather manufacture. High chemical oxygen demand, bio-chemical oxygen demand and microbial toxicity are all considered as the characters of vegetable tanning effluent, however, only a few recycling technologies were developed. In this study, bayberry tanning effluent was obtained with a commercial bayberry tannin through a common vegetable tanning process, then the polyflavonoids in the bayberry tanning effluent and commercial bayberry tannin were characterized with Fourier translation infrared spectrum, matrix-assisted laser desorption/ionization time of flight mass spectrometry, nuclear magnetic resonance, gel permeation chromatography and an elemental analysis. The results showed that the flavanol subunit in the polyflavonoids of the bayberry tanning effluent was the same with the commercial bayberry tannin, however the differences of the polyflavonoids between the bayberry tanning effluent and commercial bayberry tannin were presented in the aspect of stereochemistry, molecular weight as well as the quantity of sulfonic acid group. Polyflavonoid in the bayberry tanning effluent was composed of cis isomers, while both cis and trans stereoisomers were found in the commercial bayberry tannin. Average molecular weight of the bayberry tanning effluent was 1130 Da, in contrast to an obviously higher value in the commercial bayberry tannin (2292 Da). Meanwhile, higher sulfonic acid group content was presented in the bayberry tanning effluent. These structural differences were deduced in accordance with the diversity of collagen binding activities of the polyflavonoids. For the first time, the polyflavonoids in vegetable tanning effluent were characterized, meanwhile, the structural differences between the polyflavonoids in tanning effluent and commercial tannin were found. The results can be applied on the development of the vegetable tanning effluent related recycling technology.

Processing of Leather Using Deep Eutectic Solvents

Processing of leather has an historical reputation as a chemically and energetically intensive process that produces large volumes of aqueous waste. Saline pollution combined with heavy-metal, dyes and acid and base streams make leather production an ecologically sensitive industry. The current study shows that a variety of deep eutectic solvents (DESs) may be used for the tanning, fatliquoring and dyeing of animal hides, being particularly useful for mineral (chromium) and vegetable tanning processes. The tanning agents are able to penetrate rapidly into the hide, driven by lyotropic swelling due to their high ionic strength. The samples are shown to have similar tanning agent content to the currently used aqueous chromium(III) sulfate solution; however, the waste metal content is shown to be significantly reduced. Incorporation of the DES Ethaline into the leather significantly alters the swelling properties of the leather increasing the flexibility and ductility of the material, therefore acting in the...