Tanned Leather Wastes Research Articles

Depollution of Polymeric Leather Waste by Applying the Most Current Methods of Chromium Extraction.

The leather industry is one of the most polluting industries in the world due to the large amounts of waste following raw hide processing but also due to the high content of chemical substances present in leather waste. The main problem with chromium-tanned leather solid waste is related to the storage, due to the ability of chromium to leach into soil or water, and also owing to the high ability of trivalent chromium to oxidize to its toxic form, hexavalent chromium. The purpose of this article is to present the most current methods of chromium extraction from solid tanned leather waste in order to obtain non-polluting leather, which can constitute secondary raw material in new industrial processes. The extraction methods identified in the present study are based on acid/basic/enzymatic hydrolysis and substitution with the help of organic chelators (organic acids and organic acid salts). In addition, this study includes a comparative analysis of the advantages and disadvantages of each identified extraction method. At the same time, this study also presents alternative chromium extraction methods based on the combination of conventional extraction methods and ultrasound-assisted extraction.

Modified Fibrous Mass of Leather and Paper Waste for the Production of Packaging Paper and Cardboard

Recycling leather waste, which accumulates in large quantities in tanneries, and producing packaging paper with improved properties reduces the environmental burden and is at the same time economically efficient. A modified fibrous mass of waste from tanned and untanned leather scraps, waste paper, and acrylic emulsion was obtained and packaging paper based on them was produced. Alkaline modification of tanned leather waste - chrome shavings - leads to an increase in the electrokinetic potential and, accordingly, the stability of the fibrous suspension, partial hydrolysis of skin collagen occurs with the formation of new polar groups, and at the same time, the degree of cross-linking of the skin increases. In the paper composition, new intermolecular bonds are formed between cellulose and skin collagen. The microstructure, elemental composition, morphology, thermal and physical-mechanical properties of modified chrome shavings and composite paper were determined. A significant improvement has been achieved in the main parameters of paper: surface density (decrease by 16-25%), breaking load and breaking length (increase by 15-23%), number of double bends (increase by 2-6 times) in comparison with paper obtained from pure waste paper, and also to a greater extent compared to paper obtained from unmodified leather waste.

Removal of Cr(VI) from wastewater by impregnated activated carbon generated from vegetable tanned leather waste with aluminium oxide

The elimination of Cr(VI) from wastewater was examined by aluminium oxide-doped activated carbon originating from tannery solid waste. Activated carbon was generated from tannery solid waste at 500 °C and aluminium oxide-modified activated carbon composite was prepared at 400 °C in the muffle furnace. The AC-Al2O3 composite was characterized by elemental analysis, spectroscopically and morphologically. It was used as an adsorbent for the eradication of Cr(VI) from wastewater. The FT-IR spectra of AC-Al2O3 show the presence of different functional groups. A porous structure was found in the adsorbents by SEM analysis which was topped up with the chromium ions after adsorption. The maximum removal percentage by AC-Al2O3 adsorbent was found 97.90% at 60 mg/L while the highest adsorption capacity of Cr(VI) was 19.3 mg/g. The EDX analysis results of adsorbent after adsorption indicate the presence of chromium. The BET surface area, average pore size diameter and pore volume of the Al2O3-AC were observed to be 23.26 m2/g, 56.65 Å and 0.0329 cc/g respectively. The adsorption isotherm study revealed that the Freundlich model was best fitted with the regression coefficient (R2) of 0.9913. The kinetic investigation illustrated that the chromium removal process maintained a pseudo-second-order kinetic with the R2 value of 0.9951. Thermodynamic evaluation demonstrated that the adsorption of chromium on AC-Al2O3 adsorbent was spontaneous and exothermic. The study established that AC- Al2O3 is an inexpensive, environmentally friendly, and efficient adsorbent for extracting Cr(VI) from an aqueous solution.

Gelatin extracted from chromium (III) tanned leather waste for the synthesis of controlled release hydrogel

Chromium (III) tanned leather wastes were used to obtain gelatin, which was applied as a coating material for the synthesis of controlled urea release hydrogels. It was found that the hydrogel released its total urea content in 120 h in aqueous solution and that it promoted a significant difference in the growth of arugula seedlings. When compared with commercial gelatin, the hydrogels based on gelatin extracted from tannery waste had similar behavior, especially in the way urea was diffused to the external environment of the controlled release system, it can be characterized as a material of non-Fickian behavior during the swelling process and later, as a Fickian behavior, when it begins its process of degradation of the polymer matrix. In this way, this work demonstrates that it is possible to value a waste to obtain tools to promote a more sustainable agriculture.

Green and effective route to convert chromium-free leather waste into protein retarding material for building gypsum

Leather manufacturing generates a large amount of leather solid waste, among which the effective treatment of leather waste scraps rich in protein resources has always been a challenge for the tanning industry. In this paper, a green and convenient method was devised for the first time to prepare protein retarding material (PRM) for gypsum from chrome-free tanned leather waste. Aldehyde tanned leather scraps as the main chrome-free leather waste were directly hydrolyzed through high-pressure hydrothermal treatment without any chemicals to obtain PRM. Compared with chemical treatment (acid or alkaline hydrolysis), high-pressure hydrothermal method avoided the decrease of protein product purity due to without the help of acid and alkali. The results showed that PRM obtained from leather waste had a significant effect on prolonging the initial setting time and delaying the release of hydration heat of gypsum. With the dosage or molecular weight of PRM increased, this retarding effect on gypsum was more remarkable. SEM, XRD, and FTIR analysis indicated that the presence of PRMs inhibited the hydration process of gypsum hemihydrate to gypsum dihydrate. Through polypeptide-calcium chelation, PRMs could bind free Ca2+ ions dissolved from gypsum to delay them from participating in the hydration reaction. The larger molecular weight or the more dosage of PRM, the stronger ability to bind calcium ions in gypsum. Chemical structure characterization and molecular dynamics simulation of PRM-Ca chelate further proved that PRMs mainly through carboxyl groups on molecular chain combined with Ca2+ in gypsum system to inhibit hydration reaction, thereby fulfilling the retardation demand. This study indicated that PRM from leather scraps can be a promising candidate for gypsum retardation, which provides a path for the efficient utilization of leather waste.

Adsorption of Biebrich Scarlet Dye into Remains Chromium and Vegetable Tanned Leather as Adsorbents

Chromium tanned leather wastes (CTLW) and vegetable tanned leather wastes (VTLW) were used as adsorbent materials to remove the Biebrich scarlet dye (BS), as an anionic dye from wastewater, using an adsorption method. The effects of various factors, such as weight of leather waste, time of shaking, and the starting concentration of Biebrich scarlet dye, temperature and pH were studied. It described the adsorption process using Langmuir and Freundlich isotherm models. The obtained results agreed well with the Langmuir model, and the maximum adsorption capacities of CTLW and VTLW were 73.5294 and 78.1250 mg.g⁻¹, respectively, suggesting a monolayer adsorption process. The adsorption kinetic was found to follow a pseudo-second-order kinetic model with correlation coefficients R2 > 0.9982 and 0.9900 for CTLW and VTLW, respectively. The results predicted that chromium leather wastes were more suitable adsorbents for the removal of BS dye from wastewater than vegetable tanned leather wastes, and the adsorption process is endothermic, according to the study of the effect of temperature.

Leaching toxicity and ecotoxicity of tanned leather waste during production phase

This paper investigated the environmental impact of leather from production phase via identifying the hazardous substances (such as HCHO, Cr[VI]), leaching toxicity and ecotoxicity, with special emphasis on chrome or chrome-free. The hazardous substances of concern in various tanned leather waste from processing and commercial product were found lower than the present criterion for the eco-label product, different from the leaching toxicity and ecotoxicity. Several of the chrome-leather samples might be classified as hazardous waste for total chrome leached beyond the limitation though no Cr(VI) was leached out. Whereas the ecotoxicity toward photobacterium phosphoreum of leather samples from technology flow indicated chrome-tanned samples (S1–S3) was more toxic than corresponding chrome-free samples (S4–S6), confirming the crucial environmental impact of the tanning procedure. The increased toxicity of finished leather (S3 and S6) also revealed the significance of the finishing procedure in developing environment-friendly leather products. The multiple linear regression further demonstrated the positive correlations of the ecotoxicity of leather with leached total Cr, HCHO, and anionic polyelectrolyte. These results discerned the crucial procedures and chemicals to improve the process safety of leather.

Combined effect of transglutaminase and phenolic extract of Spirulina platensis in films based on starch and gelatin recovered from chrome III tanned leather waste

AbstractThis study aimed to enhance the properties of films produced from corn starch and gelatin recovered from chrome (III) tanned leather waste (CTLW) through the addition of transglutaminase enzyme (TGase) and phenolic extracts from Spirulina platensis (PESP). Mechanical, chemical, physical, and biological properties were analyzed and compared with control films elaborated in the same conditions but with commercial gelatin (COM). The possibility of applying the film as soil cover was analyzed through its degradation when exposed to the surface of a garden soil for a period of 60 days. The TGase caused a reduction of 50% in solubility in water, and 2% in the water vapor permeability (PWV), and PESP caused a reduction of 17% in solubility and 15% in PWV. The combined effect of TGase and PESP was a 60% reduction in solubility, 75% reduction in PWV, inhibition of contamination by Aspergillus niger, and reduction of film degradation on soil covering, evidenced by stability analysis using Fourier transform infrared (FTIR) spectrometry. The combined effect of TGase with PESP led to an improvement in the characteristics of the film produced with CTLW gelatin, rendering its application possible due to a higher lifespan, contributing to environmental sustainability and diminishing leather waste disposal at landfills. © 2021 Society of Chemical Industry and John Wiley & Sons, Ltd

Emerging contaminants adsorption by beads from chromium (III) tanned leather waste recovered gelatin

Tannery industries generate wastes that are rich in collagen and can be used to extract the gelatin. Gelatin is a macromolecule with excellent gel formation capacity, low acquisition cost, in addition to biodegradable and hydrophobic characteristics, with an abundance of chemical groups favorable to the adsorption technique. Thus, this work aimed to produce an alternative adsorbent from gelatin extracted from chromium (III) tanned leather wastes for application to remove emerging contaminants from aqueous solutions. Tartrazine yellow dye (TYD) and diclofenac sodium (DCF) were used as experimental models. The adsorbents were produced in beads shape, by drip emulsification. Commercial gelatin beads were also prepared for comparison purposes. The beads were characterized by SEM, TGA, FTIR, and pHpzc. The beads were subjected to equilibrium, kinetics, and desorption and reuse tests. The RCTLW gelatin beads showed a maximum adsorption capacity of 263.13 and 36.65 mg.g−1, for TYD and DCF, respectively. In kinetics, the adsorption density continued to increase after 300 min for TYD and was reached in the first 80 min for DCF. Mathematical modeling suggests that TYD adsorption follows the Freundlich model, while DCF is better represented by the Langmuir model. The PFO model best predicted TYD adsorption, while for DCF, both models of PFO and PSO can describe the kinetic data. The RCTLW gelatin beads showed promise for use for up to 10 cycles without loss of adsorption capacity, ending the 10th cycle with a capacity of around 100 mg.g−1 and 45% regeneration.

Transglutaminase Crosslinked Gelatin Films Extracted from Tanned Leather Waste

The production of biodegradable polymers has proved to be a promising alternative, since these materials have accelerated degradation, contributing to the reduction of residues and the reduction of environmental pollution. The tannery wastes contain considerable collagen and can be used for gelatin extraction and film production for use in agriculture. Gelatin-based films, however, present some challenges for practical application, such as permeability and solubility in water, parameters that can be improved through the crosslinking process by employing enzymes, promoting the union of polymeric gelatin chains. In this context, the action of the enzyme transglutaminase was investigated to improve the properties of gelatin films recovered from leather and chitosan residues, which were evaluated according to thickness, solubility, permeability, mechanical properties, and soil degradation. The results indicated that the enzyme concentration in the films had a significant effect on the properties of water permeability and solubility and strain to rupture. The evaluation of soil degradation showed that films with higher enzyme addition took longer to be degraded.

Adsorption of diclofenac sodium by composite beads prepared from tannery wastes-derived gelatin and carbon nanotubes

Diclofenac is an emerging contaminant belonging to the class of pharmaceutical and personal care products, and its presence in drinking water has been reported in several studies nowadays. The adsorption technique has been highlighted due to its operational simplicity, removal efficiency, and low cost, allowing the use of materials of residual origin. Gelatin has favorable characteristics for the production of adsorbent composites, and it can also be obtained from solid wastes from the tannery industry. Thus, this work aimed to produce composite beads based on gelatin recovered from leather wastes tanned with chromium(III) and the addition of carbon nanotubes, to remove diclofenac sodium. For comparison purposes, a composite based on commercial gelatin and carbon nanotubes was also produced. The composite beads were produced using the drip emulsification method. Equilibrium and kinetic tests were performed, and the materials were characterized by Scanning Electron Microscopy (SEM), Thermogravimetric Analysis (TGA), Fourier Transform Infrared (FTIR) Spectroscopy, X-ray diffraction (XRD), Point of zero charge (pHpzc), and Swelling and Water retention capacities. The composite based on gelatin recovered from chromium tanned leather waste and carbon nanotubes showed an adsorption capacity of around 20.57 mg g−1, close to the estimated value for commercial gelatin and carbon nanotubes, that was 26.97 mg g−1. The Freundlich model showed a better fit to the experimental equilibrium data. In adsorption kinetics, the Pseudo-second order model better described the kinetic behavior of removing diclofenac sodium by composite beads.

Response of Soil Bacterial Community to Application of Organic and Inorganic Phosphate Based Fertilizers under Vicia faba L. Cultivation at Two Different Phenological Stages

It is essential to investigate to which extent and how specifically soil–plant–microbe interactions can be conditioned by different agricultural practices. Legumes such as Vicia faba is one of the essential functional group in intercropping and crop rotations due to its higher N fixing capacity. Hence, it is important to study the living microbial community of this legume. Further, it is also expected that fluctuations in soil microbial diversity and composition could be complemented by plant phenological stages and different fertilizer amendments. Thus, we investigated bacterial community composition in soil treated with phosphate-based inorganic and organic fertilizers, in the presence of Vicia faba plants at flowering and fruiting time using NGS 16S rRNA gene amplicon sequencing. Further, the evaluation of plant biomass parameters under different fertilizer treatments was also carried out. The presence of the Vicia faba plant increased the abundance of N fixing bacterial such as Bardyrhizobium, Microvirga (Rhizobiales), Arthrobacter, and Psuedoarthrobacter (Actinomycetales) in soil. Fluctuation in composition and diversity of bacterial community was further supplemented by plant phenological stages. These alterations could be due to changes that occurred in the plant nutrient requirement and varied root exudation patterns at a specific phenological stage. Further, fertilizer treatments also have a profound effect on the diversity and structure of the bacterial community. Organic fertilizers, especially vegetable tanned leather waste (VTLW), have a stronger effect on the composition and diversity of bacterial community compared to inorganic fertilizer (PT—triple superphosphate). Alpha-diversity was significantly decreased by both organic and inorganic amendments, especially a species evenness because each fertilizer tends to stimulate the growth of distinctive microbes that dominated the community of amended soil. Proteobacteria, Actinobacteria, and Cyanobacteria were the most abundant phyla, and Chelatococcus, Cyanobacteria, Sphingomonas, and Microvirga were a most abundant genus that contributed most in co-occurrence pattern, which suggests that these generalists are adapted to a variety of environments. These indicate that plant presence was a key, dominating factor, followed by fertilizers and time, in affecting soil bacterial diversity and composition. Plant recruits system (fertilization and time) -specific taxa due to differences in available nutrients and energy sources among different treatments during different growth stages. Further, fertilizer treatments did not have a stronger effect on plant production as compared to the effect on microbial community, which highlights that organic fertilizers did not tend to increase plant production. Thus, organic and inorganic amendments with matched macronutrients could have a similar impact on crop yields.

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

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

Steam explosion as pretreatment to increase gelatin extraction yield from chromium tanned leather wastes

Alkaline hydrolysis of chromium tanned leather wastes (CTLW) is a promising process that allows turning this waste into valuable materials, especially into protein, recovered as gelatin. Steam explosion, which is a fast, chemical‐free, and efficient process, was tested in this work as a pretreatment to open up the fibrous structure of CTLW and ease gelatin extraction through subsequent alkaline hydrolysis, increasing the process yield. Two steam explosion temperatures (130 °C and 150 °C) and residence times (5 and 15 min) were tested. The gelatin extracted in aqueous medium was characterized according to its dry mass content, ash content, viscosity, protein content, chromium content, and helix‐to‐coil transition temperature. CTLW steam exploded in more aggressive conditions (150 °C, 15 min) allowed the extraction of three times more protein when compared to CTLW without any pretreatment. However, samples treated at 150 °C produced lower‐quality (partially degraded) gelatin. Steam explosion performed at 130 °C for 15 min almost doubled protein extraction and resulted in a better quality gelatin. This is a promising process for the proper use of CTLW as raw material for the production of high added‐value products. © 2018 American Institute of Chemical Engineers Environ Prog, 38: 367–373, 2019

Citronella essential oil microencapsulation by complex coacervation with leather waste gelatin and sodium alginate

Thousands of tons of chromium tanned leather wastes (CTLW) are produced worldwide. Alternatives for their use as raw material in other processes are particularly desired. In this study, gelatin extracted from CTLW was used in combination with sodium alginate as encapsulating agent to prepare microcapsules of citronella essential oil (CEO) by complex coacervation. The effect of gelatin and CEO concentration on the encapsulation efficiency was investigated using commercial gelatin. Best encapsulation conditions (mainly determined by morphology parameters) were found when 4% of gelatin and 10% of CEO were used, resulting in 83.5% of microencapsulation yield. Microencapsulation with CTLW gelatin was performed according to the best encapsulation conditions. It resulted in an efficiency of 73.7%, produced microcapsules with a diameter of 434.06 μm, and with a core completely covered by the encapsulating agent. Microencapsulation process with gelatin from CTLW, as presented in this paper, was shown to be an effective method that will allow controlled release of CEO.

Ecofriendly wet–white leather vs. conventional tanned wet–blue leather. A photochemical approach

Abstract Remaining waste disposal after leather tanning has become a cause of worldwide major concern since conventional disposal methods are not practicable when it comes to tanned leather wastes, such as Cr3+ conversion to Cr6+, hydrogen cyanide, nitrogen oxide and ammonia emissions. In order to bring knew knowledge and know–how into the replacing of the hazardous Cr tanned leather (wet–blue) with the eco–friendly Ti Al tanned leather (wet–white), one must first comprehend the photodecomposition mechanism of the differently tanned leathers under environmental accelerated aging conditions. It is theferore that this paper deals with comparing the influence of tanning agents on the artificial accelerated aging of the two tanned leathers. Structural changes during UV exposure were monitored by color modification measurements, fourier transform infrared spectroscopy, differential scanning calorimetry, scanning electron microscope equipped with a EDX for elemental analysis and dynamic water vapour sorption measurements. The different crosslinking patterns with tanning agents and irradiation wavelengths generated differences in photodecomposition behavior, occurring predominantly through collagen triple helix denaturation, at 365 nm, and/or cleavage of intermolecular hydrogen bonds and polypeptide chains, at 254 nm. The proteic structures photochemically decomposed through a photo–oxidative mechanism, assisted by the oxygen from air, with the formation of hydroperoxide entities. The wet–white leather was found to be less stable than the wet–blue leather in the UVA region, because of higher tendencies of polypeptide bonds cleavage occurring together with collagen triple helix denaturation. This aspect was also demonstrated by the more intense color modification registered for wet–white leather. These differences in photodegradation patterns may also further help in finding suitable photostabilizers.

Composites Produced from Natural Rubber and Chrome-Tanned Leather Wastes: Evaluation of their In Vitro Toxicological Effects for Application in Footwear and Textile Industries

A new composite has been developed from natural rubber and chrome-tanned leather waste for use in footwear and textile industries. The contribution of this material to environmental quality and sustained development should be highligh because chrome tanned leather wastes, a major environmental problem, can be recycled. However, the safety of this new material for human use is questionable, as it is already well reported in the literature that chromium, particularly in its hexavalent oxidation state, can be genotoxic and carcinogenic to living beings. Thus, the aim of this study was to evaluate in vitro biocompatibility of this composite material for possible use in the footwear and textile industries, through cytotoxicity, cell adhesion, and genotoxicity tests. Inductively coupled plasma optical emission spectrometry (ICP-OES) was used to measure both concentrations of total and hexavalent chromium. Based on the findings, it was concluded that the composite exhibits low levels of cytotoxicity and genotoxicity, and possesses favorable properties for initial cell adhesion. Furthermore, it was verified that the composites released low concentrations of chromium and that the predominant species released would be trivalent chromium. The results of the present study open the possibility of the incorporation of solid residues of tanned leather into chromium without necessarily the chromium contained in these residues influences the toxicity and genotoxicity of this new material.

Color removal from real leather dyeing effluent using tannery waste as an adsorbent

In this study the adsorption of the dye Acid Red 357 (AR357) present in dyeing effluent, through the use of chromium tanned leather waste (CTLW) as an adsorbent is investigated. The results demonstrate an adsorption capacity of 148.2mgg−1, and the removal of approximately 58% of the dye present in solution. In addition the data for adsorption in dyeing effluent, when compared to the data for aqueous solution, demonstrate that competition for adsorption sites by other chemical compounds present in the effluent takes place. The dyeing effluent presents elevated toxicity to microcrustacea, fish and luminescent bacteria, however, after treatment by adsorption, the toxicity is reduced by up to 90% compared to the untreated effluent.

Bio-mimetic mineralization potential of collagen hydrolysate obtained from chromium tanned leather waste.

Hydroxyapatite (HA) ceramics serve as an alternative to autogenous-free bone grafting by virtue of their excellent biocompatibility. However, chemically synthesized HA lacks the strong load-bearing capacity as required by bone. The bio-mimetic growth of HA crystals on collagen surface provides a feasible solution for synthesizing bone substitutes with the desired properties. This study deals with the utilization of the collagen hydrolysate recovered from leather waste as a substrate for promoting HA crystal growth. Bio-mimetic growth of HA was induced by subjecting the hydrolysate to various mineralization conditions. Parameters that would have a direct effect on crystal growth were varied to determine the optimal conditions necessary. Maximum mineralization was achieved with a combination of 10mM of CaCl2, 5mM of Na2HPO4, 100mM of NaCl and 0.575% glutaraldehyde at a pH of 7.4. The metal-protein interactions leading to formation of HA were identified through Fourier-transform infrared (FTIR) spectroscopy and x-ray diffraction (XRD) studies. The crystal dimensions were determined to be in the nanoscale range by atomic force microscopy (AFM) and scanning electron microscopy (SEM). The size and crystallinity of bio-mimetically grown HA indicate that hydrolysate from leather waste can be used as an ideal alternative substrate for bone growth.

Pollution reduction in an eco-friendly chrome-free tanning and evaluation of the biodegradation by composting of the tanned leather wastes

Abstract Chromium is one of the most important environmental concerns related to tanneries. The most often used process for hide tanning is chrome tanning. This implies the presence of chromium both in wastewaters and in leather wastes. Leather wastes have to be disposed in landfills what entails a considerable environmental impact and high cost. In this work, a study about the effect of a chrome-free tanning process using titanium salts instead, on the wastewater and on the solid wastes has been performed. In this way, a study of biodegradation of leather waste samples tanned with different tanned agents by composting together with food wastes is carried out in a laboratory composter. Results indicated that leather tanned with titanium salts met the required quality standards. Besides, the concentration of organic matter and salts in the tannery process wastewater was lower comparing with the chromium tanning agent. In the biodegradation study by composting, leather samples tanned with titanium were degraded, reducing around 10% the carbon content with the subsequent diminution of the C/N ratio. In addition, the size was reduced 41% in 45 days. However, leather sample tanned with oxazolidine was partially degraded in the composter; meanwhile chrome and vegetable tanned leather kept inalterable.